Salt Tectonics, Associated Processes, and

Salt Tectonics, Associated Processes, and Exploration Potential: Revisited:

1989–2019

37th Annual Gulf Coast Section SEPM FoundationPerkins-Rosen Research Conference

2019

Program and Abstracts

Charles Davidson Hall, Noble EnergyHouston, Texas

December 3–6, 2019

Edited by

J. Carl FidukNorman C. Rosen

Copyright © 2019 by theGulf Coast Section SEPM Foundation

www.gcssepm.org

Published December 2019

ii Program and Abstracts

http://www.gcssepm.org

Foreword

“It was 20 years ago today, Sgt. Pepper taughtthe band to play.” Well no, that is not quite correct. Yetit was 30 years ago that the first conference on salt tec-tonics was held as the Tenth Annual GCSSEPMFoundation Research Conference. The conferenceheld in 1989 emphasized the basics as known at thetime: the rift origin of the Gulf of Mexico, the extent ofautochthonous and allochthonous salt, the delineationof regional salt provinces, descriptions of salt structuralstyles, limited understanding of internal salt character-istics, and simple salt-sediment interactions. It wasdominated by observations made in the northern Gulfof Mexico although there were papers on West Africaand the Canadian Arctic. The then chairman of theGCSSEPM Board of Trustees, Clarence Albers, sug-gested that “perhaps at some future time a reprise ofthis topic may be appropriate….” That time is now.

My initial thoughts when proposing this confer-ence was to do exactly as Clarence Albers suggested,to reprise the topics covered in the meeting 30 yearsago. However, I quickly realized that this would bewholly inadequate and fail to cover or acknowledge allthe progress that has been made since that first meet-ing. So a balancing act was required. To cover all theprogress I needed to invite the cream of those sea-soned professional and scientists to present theirworks. But rather than just nostalgically look at thepast, the conference should also eagerly focus itself onthe future. To that end very deliberate attempts weremade to include bright young professionals and prom-ising graduate students in the program. A solid mix ofpresenting what we have learned and where we areheaded is the game plan. Seven of the 33 plannedspeakers (21%) will be enthusiastic youngprofessionals.

What we have learned about salt and its behav-ior during the last 30 years is quite an impressive stepbeyond our initial understandings. Most importantly, wemust recognize and acknowledge that much of thatunderstanding has come from observations andresearch outside the Gulf of Mexico. Yes, the Gulf ofMexico is probably the most studied basin in the worldbut it is not the only place to learn about salt. The firstday has five talks focused on international settingsincluding 1) the La Popa Basin, Mexico, 2) the EasternMediterranean, 3) the Campos Basin, Brazil, 4) theSpanish Pyrenees and Catalunya, and 5) the NorthernCalcareous Alps and Pyrenees. Day 2 has eight talksfocused on various salt basins around the world. In oneof those papers the authors introduce a subject thatwould have been impossible 30 years ago: they pres-ent a methodology for producing a 3D model of theinterior of a salt diaper using cores, well logs, and

ground-penetrating radar. Yes, we have left the 1980sbehind. The key message is that there is a lot to learnfrom all the world’s salt basins. By opening our eyes tothese other salt basins worldwide we can shorten ourtime on the learning curve. Every salt basin has some-thing valuable to teach us.

This is not to say that the Gulf of Mexico is now“mature” and that we know everything there is to knowabout it. That is far from the truth. Although our currentunderstanding of the northern Gulf of Mexico is lightyears ahead of where it was 30 years ago, the papersto be presented here highlight how much is stillunknown and yet to be discovered in this basin. Theage of the Louann salt is very much in question andpast assumptions are being challenged. Many papersbring up this question and three papers in particularaddress this very topic: 1) The age of the Louann salt:Insights from historic isotopic analyses in salt stocksfrom the onshore interior salt basins of the northernGulf of Mexico, 2) Tectonic models for the Gulf of Mex-ico in light of new Bajocian ages for proximal saltdeposition, and 3) Paleo-oceanographic precondition-ing promotes precipitation: how the global context is akey factor for understanding Bajocian Louann saltdeposition. The timing of rift basin formation in the Tri-assic, and the depositional environments presentwithin the basin is another very hot topic. How muchtime is missing between the top of the synrift sedimentsand the emplacement of salt? How long did the saltdeposition phase last? Did the sea water that gave riseto the Louann salt come from the Pacific or the nascentAtlantic? These questions and more will addressed.

Conducting my part in producing this conferenceis something I have always aspired to do. Ever since Iattended my first GCSSEPM conference back in 1989,I’ve felt it was a task on my “to do” list. If I had trulyknown how much work it was going to be when I pro-posed the conference topic to Tony D’Agostino in 2017,I might have had second thoughts. But now that it isdone I am very happy to have made the commitment. Iconsider this part of my giving back to the geologiccommunity that has given so much to me. In my 37year career (and still going) there have been multipleups and downs, yet the highs far overshadow the lows.This is one of my high points and I am pleased to shareit with so many friends and colleagues.

My part in this reminds me that I am not alone.There are many others who have contributed to thisand all the past conferences who deserve credit. Toname everyone is impossible but to pay homage andrespect to those giving service does not happen oftenenough. Most deserving is Gail Bergan. Without her“the Minnow would be lost.” She makes everything

Salt Tectonics, Associated Processes, and Exploration Potential: Revisited: 1989–2019 iii

concerning the conference publication and websitework efficiently. You have my gratitude. I also want topay respect to the guys driving the boat, our pastGCSSEPM Foundation Directors Bob Perkins, NormRosen, Tony D’Agostino, and current Director JohnSuter. Without them there would not be a Perkins-

Rosen research conference for us to attend and ourscience would be much poorer without it. Thank yougentlemen for your time, your service, and your willing-ness to give back for the benefit of everyone else. Weare in your debt.

Carl FidukTechnical Program Chair

The GCSSEPM Foundation greatly appreciatesthe generosity of Noble Energy in providing the CharlesDavidson Hall as the venue for the 2019 Perkins-Rosen Conference. This generosity was facilitated byCarmen M. Fraticelli, Excellence and Portfolio Man-ager, and Jim Demarest, Vice President of Exploration.We thank Brad White and the entire AV staff of NobleEnergy for their efforts in putting on the presentations

and all the other Noble employees who were involvedin staging this event.

We further thank the staff of SEPM (Society forSedimentary Geology) of Tulsa, Oklahoma, particularlyCassie Turley, Hayley Cooney and Theresa Scott, fortheir tireless efforts in event planning and execution.Without their help we would be unable to plan, orga-nize, and stage an event like the Perkins-RosenConference.

John R. Suter, PhDExecutive Director

iv Program and Abstracts

Salt Tectonics, Associated Processes, and Exploration Potential: Revisited:

1989–2019

37th Annual Gulf Coast Section SEPM FoundationPerkins-Rosen Research Conference

2019

Program

Tuesday, December 3

6:30–9:00 P.M. Registration and refreshments at the BRIX Wine Cellar at Vintage Park, 110 Vintage Park Blvd. T, Houston, Texas 77070. Two drinks and appetizers will be provided per paid confer-ence attendee.

Wednesday, December 4

7:30 a.m. Continuous registration (breakfast and coffee served)8:00 a.m. Introduction and welcome remarks: John R. Suter, Executive Director, GCSSEPM Foundation;

Jim Demarest, Vice President of Exploration, Noble Energy; and J. Carl Fiduk, Technical Program Chair

Session 1: Lessons from the Past

Van Mount, Thomas Hearon, and Carl Fiduk, Co-Chairs

8:15 a.m. Evolution of Marine Seismic Imaging from Late 1990s to Middle 2010s: A WesternGeco Perspective ....................................................................................................................................1

Carl Fiduk and Kevin Lyons

8:45 a.m. Salt-Sediment Interaction: Lessons Learned from La Popa Basin, Mexico ..................................2Katherine A. Giles, Mark G. Rowan, and Timothy F. Lawton

9:15 a.m. It’s not Just Halite—What We’ve Learned in 30 Years About Intrasalt Deformation ..................4Mark G. Rowan, Janos L. Urai, J. Carl Fiduk, and Peter A. Kukla

9:45 a.m. Coffee break

10:05 a.m. Paleogeographic Reconstruction of the Louann Salt Basin ..........................................................5John W. Snedden, Ian O. Norton, Michael R. Hudec, and Frank Peel

Salt Tectonics, Associated Processes, and Exploration Potential: Revisited: 1989–2019 v

Session 2: Young Professionals Research 1

C. Evelyn Gannaway Dalton and Sian Evans, Co-Chairs

10:35 a.m. Intrasalt Structure and Strain Partitioning in Layered Evaporites: Insights from the Messinian Salt in the Eastern Mediterranean .................................................................................................6

Sian L. Evans and Christopher A.-L. Jackson

11:05 a.m. Salt Tectonics Within Strike-Slip Systems, Campos Basin, Brazil ................................................7Stephanie Wischer and Webster Mohriak

11:35 a.m. Evolution of Megaflaps, Extensional-Rollover Subbasins, and Salt-Withdrawal Minibasins at Aulet and Adons Diapirs in the Spanish Pyrenees, Catalunya ......................................................8

C. Evelyn Gannaway Dalton, Katherine A. Giles, Josep Anton Muñoz, andMark G. Rowan

12:05—1:15 Lunch served

Session 3. Age of Louann Salt

Andy Pulham and Thierry Rives, Co-Chairs

1:15 p.m. The Age of the Louann Salt; Insights from Historic Isotopic Analyses in Salt Stocks from the Onshore Interior Salt Basins of the Northern Gulf of Mexico ......................................................9

Andrew J. Pulham, Frank J. Peel, Thierry Rives, Bryan Delph, Jean-Francois Salel, Tim Nicholson, John Wu, and Rick Requejo

1:45 p.m. Middle Jurassic Tectonic Models for the Gulf of Mexico in Light of New Bajocian Ages for Proximal Margin Salt Deposition ..................................................................................................11

James Pindell, Diego Villagómez, Brian W. Horn, and Roberto Molina Garza

2:15 p.m. Paleo-Oceanographic Preconditioning Promotes Precipitation: How the Global Context is a Key Factor for Understanding Bajocian Louann Salt Deposition ................................................12

Frank J. Peel

2:45 p.m. Group discussion

3:15 p.m. Coffee break; continue group discussion

Session 4. New Ideas, Old Topics

Andy Pulham and Thierry Rives, Co-Chairs

3:35 p.m. Synthesizing Old Questions with New Developments in Caprock Research: Is it Time to Abandon Well-Trodden Paths? .....................................................................................................................14

Benjamin Brunner, Amanda L. Labrado, Gail L. Arnold, Julia Astromovich, Claire Bailey, Stefano M. Bernasconi, Kyle Deatrick, Hanah Draper, Frederic O. Escosa, C. Evelyn Gannaway Dalton, Elizabeth A. Heness, Muhammed Tarik Iraz, Jessica Thompson Jobe, Rachelle Kernen, David Lankford-Bravo, Kevin Lerer, Ally Mast, Josh McFarland, Jörn Peckmann, Piper Poe, Ryan Ronson, Austin Shock, andKatherine Giles

vi Program and Abstracts

4:05 p.m. Minibasins Involved in Fold and Thrust Belts: From Their Development in Passive Margins to Contractional Reactivation (Examples from the Northern Calcareous Alps, Pyrenees and Experimental Modeling) ................................................................................................................16

J. A. Muñoz, P. Granado, E. Roca, P. Strauss, O. Ferrer, P. Santolaria, O. Gratacós, N. Carrera, J. Miró, and E. Wilson

4:35 p.m. Applications of Biostratigraphy to Salt Tectonics, Northern Gulf of Mexico ...............................18

5:05 p.m.

Richard Denne

End of Day 1

Thursday, December 5

7:30 a.m. Continuous registration (breakfast and coffee served)

Session 5. Western Hemisphere

Co-chairs TBA

8:00 a.m. On Elevators and Bulldozers: What has Changed in Salt Tectonics? Examples from Passive Margin Salt Basins .....................................................................................................................................19

Hermann Lebit

8:30 a.m. Salt Tectonics in the Brazilian Margin: Key Issues and Technical Advancements in the Past 30 Years ..............................................................................................................................................20

Webster Mohriak

9:00 a.m. A Critical Review of Models for Deposition of the Louann Salt, and Implications for Gulf of Mexico Evolution ...........................................................................................................................21

Michael R. Hudec and Frank J. Peel

9:30 a.m. Salt Tectonics Controls on Deepwater Sedimentation: Salina del Istmo Basin, Southern Gulf of Mexico .......................................................................................................................................22

Clara Rodriguez, Jonathan Hernandez Casado, Raul Ysaccis, Sebastian Villarroel, Kevin Lyons, Maxim Mikhaltse, and Mohamed El-Toukhy


Session 6. Young Professionals Research 2

C. Evelyn Gannaway Dalton and Oliver Duffy, Co-Chairs

10:30 a.m. Controls of Interbedded Sand Beds on Pore Pressure, Stresses, and Evolution of a Salt System 23Mahdi Heidari, Maria A. Nikolinakou, Michael R. Hudec, and Peter B. Flemings

11:00 a.m. Redirection of Submarine Channels by Minibasin Obstruction on a Salt-Detached Slope: An Example from Above the Sigsbee Canopy .....................................................................................24

Oliver Duffy, Naiara Fernandez, Frank Peel, Michael Hudec, Gillian Apps, Dallas Dunlap, and Christopher Jackson

Salt Tectonics, Associated Processes, and Exploration Potential: Revisited: 1989–2019 vii

Session 7. Salt in Europe and Asia Minor

Maria A. Nikolinakou, Chair

11:30 a.m. The European Zechstein Salt Giant—Trusheim and Beyond ........................................................25Peter A. Kukla, Janos L. Urai, Alexander Raith, Shiyuan Li, Jessica Barabasch, andFrank Strozyk

12:00—1:15 p.m. Lunch served

1:15 p.m. 3D Model of Complex Internal Structures in a Northern German Salt Diapir: A Multi-disciplinary Approach Using Drilling Cores, Well Logs, and Ground Penetrating Radar ..........26

Lukas Pollok, Tatjana Thiemeyer, Marco Saßnowski, and Volker Gundelach

1:45 p.m. Salt Tectonics and Hydrocarbon Accumulations Trapped on Diapir Flanks in the Lusitanian Basin, Portugal ..............................................................................................................................27

Ian Davison and Pedro Barreto

2:15 p.m. Salt Tectonics Outcrops and 3D Drone Images from the Sivas Basin (Turkey) Compared to High-Resolution Seismic Lines in the GOM and B32 Angola .......................................................28

Jean-Claude Ringenbach, Charlie Kergaravat, Charlotte Ribes, Alexandre Pichat, Etienne Legeay, and Jean-Paul Callot

2:45 p.m. Group discussion

3:15 p.m. Coffee break, continue discussion

Session 8. Advances in Modeling

Maria A. Nikolinakou, Chair

3:35 p.m. Salt Tectonics Restoration in Basin and Petroleum System Modeling: Contribution of Physical Analogue Models and Methodologies ...........................................................................................29

Sylvie Schueller, Marie Callies, Jean-Marie Mengus, Nadine Ellouz-Zimmermann, and Jean-Luc Rudkiewicz

4:05 p.m. Loading Complex Salt Isopachs: Progradation Across Segmented Salt-Filled Rift Systems .......30Tim P. Dooley and Michael R. Hudec

4:35 p.m. Geomechanical Modeling of Diapirism in Extensional Settings: Controls on Styles of Diapir Rise and Fall ..................................................................................................................................31

Maria A. Nikolinakou, Mahdi Heidari, Michael R. Hudec, and Peter B. Flemings

5:05 p.m. End of Day 2

viii Program and Abstracts

Friday, December 6

7:30 a.m. Continuous registration (breakfast and coffee served)

Session 9. New Insights from the Northern Gulf of Mexico

Van Mount, Thomas Hearon, and Carl Fiduk, Co-Chairs

8:00 a.m. Structural Configuration and Evolution of Subsalt Hydrocarbon Traps Adjacent to Salt Walls, Green Canyon, Gulf of Mexico ......................................................................................................32

Van S. Mount, Scott J. Wilkins, Brian Lindsey, Todd Butaud, Peter Gamwell, Todd Fowler, Carlos Morris, Haryanto Adiguna, and Byron McDonald

8:30 a.m. Sub-Seismic Deformation in Traps Adjacent to Salt Stocks/Walls: Observations from Green Canyon, Gulf of Mexico .................................................................................................................33

Scott Wilkins, Van Mount, Todd Butaud, Brian Lindsey, Haryanto Adiguna, Jonathon Syrek, Chelsea Fenn, Inga Matthews, and Russell Davies

9:00 a.m. Can Deep Mantle Processes Influence Regional Salt Tectonics? .................................................34Gillian Apps, Tim Dooley, and Alex Bump

9:30 a.m. Mass-Transport Complexes (MTCs) Steered by Minibasin Obstruction and Extensional Breakaway on a Salt-Detached Slope: An Example from Above the Sigsbee Canopy .................35

Naiara Fernandez, Oliver Duffy, Frank Peel, Michael Hudec, Gillian Apps, andChristopher Jackson


10:20 a.m. Interaction of Tectonics, Salt, and Sediments in the Gulf of Mexico: An Approach Using Image Processing of Seismic Data ...........................................................................................................36

Andreas W. Laake

10:50 a.m. The Sakarn Series: A Proposed New Middle Jurassic Stratigraphic Interval from the Offshore Eastern Gulf of Mexico ..................................................................................................................37

Thierry Rives, Andre Ramiro Pierin, Andrew J. Pulham, Jean-Francois Salel, John Wu,Adrienne Duarte, and Benoit Magnier

11:20 a.m. Salt Canopy Rafts in the Northern Gulf of Mexico: Identifying and Understanding the Significance of Strata Laterally Translated by Allochthonous Salt ..............................................39

Steven Holdaway

11:50—12:00 p.m. Group discussion. Meeting wrapup and adjourn.

Salt Tectonics, Associated Processes, and Exploration Potential: Revisited: 1989–2019 ix

GCSSEPM Foundation

Trustees and Executive DirectorJohn Suter, Executive Director

Houston, Texas

Ron WaszczakConsultantHouston, Texas

Dorene WestDorene B. West CPG Inc.Houston, Texas

John SneddenInstitute for GeophysicsAustin, Texas

Jennifer WadsworthBP AmericaHouston, Texas

Executive CouncilPresidentThomas DemchukRPS EnergyHouston, Texas

President ElectDon S. Van NieuwenhuiseUniversity of HoustonHouston, Texas

Vice PresidentMike L. SweetHouston, Texas

TreasurerJulitta Kirkova PourciauHouston, Texas

SecretaryMilly WrightChemostratHouston, Texas

Technical Program Co-ChairmenCark FidukFiduk Consulting

Thomas HearonEOG Resources

Van MountAnadarko

Technical Program CommitteeGillian AppsBEG

Kathrine GilesUTEP

Steve HoldawayChevron

Piotr KrzywiecPolish Academy of Science

Robin PilcherHess

Henrik RoendeTGS

Craig SchneiderConocoPhillips

Tim DooleyBEG

Bill HartVenari Resources

Brian HornION

Hermann LebitPGS

Frank PeelBEG

Andrew PulhamEarth Sci. Assoc. C&T

Mark RowanRowan Consulting

x Program and Abstracts

Contributors to the GCSSEPM Foundation

Sponsorship CategoriesPlease accept an invitation from the GCSSEPM Section and Foundation to support Geological and Geophysical

Staff and Graduate Student Education in Advanced Applications of Geological Research to Practical Problems ofExploration, Production, and Development Geology.

The GCSSEPM Foundation is not part of the SEPM Foundation. In order to keep our conferences priced at a lowlevel and to provide funding for university staff projects and graduate scholarships, we must have industry support.The GCSSEPM Foundation provides several categories of sponsorship. In addition, you may specify, if you wish,that your donation be applied to Staff support, Graduate support, or support of our Conferences. Please take amoment and review our sponsor categories for 2019, as well as our current and past sponsors. In addition, we askthat you visit our sponsors’ Web sites by clicking on their logo or name. Thank you for your support.

Corporate Sponsorships

Diamond($15,000 or more)

Platinum($10,000 to $14,999)

Gold($6,000 to $9,999)

Silver($4,000 to $5,999)

Bronze($2,000 to $3,999)

Patron($1000 to $1,999)

Individuals & Sole Proprietorships

Diamond($3,000 or more)

Platinum($2,000 to $2,999)

Gold($1,000 to $1,999)

Silver($500 to $999)

Bronze($300 to $499)

Patron($100 to $299)

Sponsor AcknowledgmentFor 2019, all sponsors will be prominently acknowledged on a special page inserted in the 2019 and 2020

Program & Abstracts volume, and with placards strategically placed in the registration area of the conference.

Corporate level Diamond sponsors will be acknowledged by having their logo placed in the front matter of theProgram & Abstracts volume and are eligible for a free half-page ad in the Section newsletter.

Corporate level Platinum sponsors will be acknowledged by having their logo placed in the front matter of theProgram & Abstracts volume and are eligible for a free quarter-page ad in the Section newsletter.

All contributions used for scholarships and/or grants will be given with acknowledgment of source. In addition tothe recognition provided to our sponsors in GCSSEPM publications, we proudly provide a link to our sponsors’ Websites. Just click on their logo or name to visit respective GCSSEPM sponsors.

The GCSSEPM Foundation is a 501(c)(3) exempt organization. Contributions to the organization are taxdeductible as charitable gifts and contributions. For additional information about making a donation as a sponsor orpatron, please contact Dr. John Suter, Executive Director, GCSSEPM Foundation, 12645 Memorial Dr., Ste. F-1#160, Houston, TX 77024. Telephone 713-858-6108, or e-mail at [email protected].

Salt Tectonics, Associated Processes, and Exploration Potential: Revisited: 1989–2019 xi

mailto:[email protected]




2019 Sponsors

Sponsorship Category

Corporations

Diamond

Silver

Bronze

Sponsorship Category

Individuals & Sole Proprietorships

Gold

Ian Davison, EarthmovesRon Waszczak

John R. Suter and Carmen M. FraticelliCarl Fiduk

PatronMichael StyzenRichard Fillon

xii Program and Abstracts

https://www.nblenergy.com/

http://www.hess.com

http://www.hess.com

https://www.pgs.com/

http://www.petrophysicalsolutions.com/

Credits

Design and Digital Publishing by

Rockport, Texaswww.bergan.com

Cover ImageThe cover image chosen for this year’s conference is from Kukla et al. “The European Zechstein Salt Giant—

Trusheim and Beyond”: Figure 7: Cylindrical folds of anhydrite layers in rock salt, exposed by solution mining.

Salt Tectonics, Associated Processes, and Exploration Potential: Revisited: 1989–2019 xiii

http://www.bergan.com

http://www.bergan.com

xiv Program and Abstracts

Evolution of Marine Seismic Imaging from Late 1990s to Middle 2010s: A WesternGeco Perspective

Carl FidukFiduk Consulting LLC9593 Doliver DriveHouston, Texas 77063

Kevin LyonsWesternGeco10001 Richmond AvenueHouston, Texas 77042

Abstract

The time period from the early 1990s through tothe early 2010s saw a consistent and steady increase inthe (1) depth of data imaged, (2) level of seismic detailrevealed, and (3) complexity of tectonic and salt struc-tures resolved. To achieve this remarkable increase indata quality, the seismic industry made paralleladvances in seismic acquisition techniques, data pro-cessing algorithms, and computer processing speed.The resulting high quality imagery has allowed inter-preters, modelers, and research scientists to advancethe science of salt tectonics from a relatively basiclevel in the early 1990s to a robust and highly inte-grated science in 2019.

State-of-the-art marine seismic data acquisitionin 1990 involved a single vessel towing a single cable 4km long collecting time data in a 1-2 km spaced 2-Dgrid. By the early 1990s, narrow azimuth 3-D timeacquisition evolved. Initially this started with a singlevessel towing two streamers of 4 km length and record-ing 8 second records. It grew to involve multiplevessels towing 3-6 streamers of 6 km length andrecording 14 second records. Kirchhoff was standardadvancing from post-stack time to pre-stack timemigration.

In the early 2000s, time processing and depthprocessing existed side by side, but exploration needswere pushing for better depth data. Kirchhoff pre-stackdepth volume quality was replaced by Wave Equationpre-stack depth data in areas of greater structural com-plexity. Depth processing now included one or two topsalt-base salt pairs to image the subsalt stratigraphy.

By the mid-2000s, wide-azimuth acquisition wasthe procedure of choice. Vessels were towing 8-10streamers of 7-8 km in length. Maximum offsets werereaching 8-9 km and receiver location systems werebeing employed. Velocity analysis employed multi-azi-muth sediment tomography incorporating seismicanisotropy and later vertical transverse isotropy.

Around 2009-2010, reverse time migrationbecame the processing algorithm of choice. Velocityfields were calibrated to subsalt well ties. Velocityanalysis incorporated full waveform inversion withvertical transverse isotropy and then tilted transverseisotropy. Running multiple iterations of intrasalt andsubsalt full waveform inversion would become stan-dard practice.

In the early 2010s, WesternGeco introduced fullazimuth and multi-vessel full azimuth acquisition.Proper acquisition and processing of full azimuth datarequired streamer steering capabilities, precise receiverpositioning, advanced noise attenuation algorithms,and state-of-the-art computing facilities. Full azimuthacquisition produced maximum offsets of 14-16 km.Eventually, full azimuth and wide-azimuth data setswere merged to reduce noise and maximize the effi-ciency of tried and tested wide-azimuth processingroutines. Seismic examples over the same location shotfrom 1990s to 2015 illustrate the incremental gainsmade in imaging the subsurface in response to thesetechnical advances.

Salt Tectonics, Associated Processes, and Exploration Potential: Revisited: 1989–2019 1

Salt-Sediment Interaction: Lessons Learned from La Popa Basin, Mexico

Katherine A. GilesInstitute of Tectonic StudiesThe University of Texas at El PasoEl Paso, Texas, 79968email: [email protected] G. RowanRowan Consulting Inc.Boulder, Coloradoemail: [email protected]

Timothy F. LawtonBureau of Economic GeologyAustin, Texasemail: [email protected]

Abstract

The state-of the-art in our understanding of salt-sediment interaction in 1989 was that stratal packagesgenerally thin and turn-up near salt stocks/walls. Thiswas attributed to late penetration of prediapiric strataby buoyant salt and consequent shear and structuralthinning of flanking strata. The primary sources ofinformation at that time were vintage seismic data andborehole data; i.e., poor images and one-dimensionalsamples of the diapir edges and adjacent sediment. Thisis where, starting in the mid-1990's, studies of theexceptional outcrops of La Popa basin, Mexico, pro-vided the first systematic and detailed documentationof near-diapir sedimentologic, stratigraphic, structural,and petroleum system architecture at several differenttypes of steep-sided salt structures including flaringsalt stocks and a secondary salt weld.

The first breakthrough from analysis of La Popaoutcrops was that not only do strata thin and upturn asthey approach the diapirs, but they form local, angularunconformity-bound stratal packages (halokineticsequences) that record the interplay between rates ofpassive diapiric rise and local sediment accumulation.Moreover, structural analysis revealed that the thinningwas depositional rather than structural and that theupturn was caused by drape folding of roof strataduring passive diapirism instead of drag folding.

Sedimentologic studies of halokinetic sequencesdeveloped in various depositional systems, rangingfrom nonmarine (mostly fluvial) to relatively sediment-starved outer-shelf systems in both siliciclastic and car-bonate rocks, showed that the diapirs had variabletopographic relief. Higher relief was created duringperiods of relatively slow sedimentation, whereby dia-pir-rise rate outpaced sediment accumulation. Thisscenario resulted in deflection of clastics away from

the high, intercalation of mass-wasting depositsderived from failure of the diapir roof, and the diapiritself, as well as generation of an elevated substrate in aregionally deeper water, siliciclastic-starved settingthat permitted prolific carbonate reef growth over thediapir high. Conversely, when sediment accumulationrates exceeded diapir rise, relief was minor to nonexis-tent and sediment deposition was controlled more byregional processes. The cyclic variations in sediment-accumulation rates vs diapir-rise rates in halokineticsequences were subsequently shown to stack intohigher order composite halokinetic sequences, whichwere correlated to regional depositional sequences andrelative sea-level changes. Composite halokineticsequences form two end-member types that vary indrape-fold geometry and scale, which is ultimatelyrelated to the thickness of the roof panel being drapefolded during diapir rise.

The La Popa outcrops also led to the firstdetailed structural analysis of a secondary weld formedby squeezing of a salt wall and the lateral variation inassociated small-scale structures over its 24 km length.There is little to no deformation of flanking strata onthe northwest portion where it is still an apparent weld(>50 m of remnant evaporite). Where it is a discontinu-ous weld (with pods of gypsum up to 30 m wide), thereis increased fracture density up to 15 m into the adja-cent strata. The southeast 8 km of the structure is acomplete weld with a damage zone up to 50 m thick inthe down-dropped siliciclastics due to post-weldingweld-parallel strike-slip deformation.

Similar sedimentologic, stratigraphic, and struc-tural styles/trends have subsequently been documentedin many other outcropping salt basins worldwide (e.g.,Paradox Basin, Nova Scotia, Spanish Pyrenees, Atlas

2 Program and Abstracts

Mts., Zagros Mts., Flinders Ranges) and in subsurfaceequivalents. Ongoing studies that build on the funda-mental relationships documented in La Popa basininclude but are not limited to: changes in stratal andstructural style along strike or around diapirs, deposi-

tional response to halokinesis of deep watersedimentary systems, sediment routing systems in saltbasins, as well as the relationship of minibasin-widegrowth strata to halokinetic sequences.


It’s not Just Halite—What We’ve Learned in 30 Years About Intrasalt Deformation

Mark G. RowanRowan Consulting5rrr, Inc.850 8th St. Boulder, Colorado 80302email: [email protected] L. UraiStructural Geology, Tectonics and GeomechanicsRWTH Aachen University52056 Aachen, Germany

J. Carl Fiduk Fiduk Consulting, LLC9593 Doliver Drive Houston, Texas 77063Peter A. KuklaEnergy and Mineral Resources GroupRWTH Aachen UniversityDirector Geological InstituteWuellnerstr. 252062 Aachen, Germany

Abstract

Thirty years ago, salt bodies were generallydepicted on cross sections or seismic interpretationswith just outlines or solid colors. Exceptions weremade by those working in salt mines or drilling throughsalt in basins such as the southern Permian basin ofEurope. Over the past three decades, increased penetra-tions of salt layers and vastly improved seismic imageshave forced a reevaluation of how we think of diapirsand other salt bodies.

Salt layers are in reality layered evaporitesequences comprising interbedded incompetent layers(halite and bittern salts) and competent layers (anhy-drite, carbonates, and siliciclastics). This results in apronounced rheological stratification, with both fric-tional and ductile materials and a wide range ofeffective strength. Ductile flow of halite, as the domi-nant mineral, is understood reasonably well, but muchless attention has been paid to the stronger layers,whose behavior depends on the predominant mode ofdeformation.

In layer-parallel extension, boudinage of compe-tent layers is easy and forms ruptured stringers within ahalite matrix. In layer-parallel shortening, competentlayers are stronger, and tend to maintain coherency inmultilayer buckle folding. In differential loading,extension and the resultant stringers dominate beneathsuprasalt depocenters while folded competent bedscharacterize salt pillows. Finally, in tall passive diapirs,stringers generated by intrasalt extension are rotated tonear vertical and form tectonic melanges duringupward flow of salt. In all cases, strong layers are pro-gressively removed from areas of salt thinning andbecome increasingly disrupted in other areas as defor-mation intensifies.

The varying style of intrasalt deformationimpacts seismic imaging and analyses of both seismicand well data. Both may be interpreted to suggest thatdiapirs and other areas of more intense intrasalt defor-mation are more halite rich than is actually the case.


Paleogeographic Reconstruction of the Louann Salt Basin

John W. SneddenIan O. NortonInstitute for GeophysicsThe University of Texas at Austin10100 Burnet Rd. (R2200) Austin, Texas 78758email: [email protected]

Michael R. HudecFrank Peel Bureau of Economic GeologyThe University of Texas at Austin10100 Burnet Rd.Austin, Texas 78758

Abstract

The presence of Jurassic age salt in the Gulf ofMexico has been known for almost 60 years, originallyrecognized as two separate salt bodies. Reconstructionof the original saline basin as it appeared prior to seafloor spreading has been difficult to carry out due tosubsequent allochthonous salt movement that obscuresstratal relationships at depth. However, a new approachto seismic mapping of the Louann salt using its tec-tonostratigraphic character allows recognition ofdistinct Louann facies transitions from deep basin toonshore lapouts. Halite-dominated Louann is moreductile, often seismically dim, and readily facilitatesfault detachment. Halite likely formed in the deepbasin, with coeval anhydrite forming in shallow watersabhkas and evaporitic lagoons. Anhydrite-dominatedsections are seismically and structurally distinct havinghigh amplitude/continuity and a less ductile character.A zone of mixed seismic response that we infer to beinterbedded halite and anhydrite separates these seis-mic facies (Fig. 1; Snedden and Galloway, in press).

Our new paleogeographic reconstruction of theLouann salt has been developed on the basis of thisseismic facies mapping, in combination with new platetectonic models. 87/86Sr ratios from interior salt basinsindicate a proxy age of 170-ma when matched againstthe global strontium seawater curve (Fig. 2; Sneddenand Galloway, in press). Although a 170-ma age for theLouann salt is 7-8 ma earlier than previous estimates(Hudec et al. 2013), this occurs during a phase when

various plates are in closer proximity and thus condi-tions are more conducive to restriction andevaporation.

This reconstruction also allows evaluation of twocontrasting hypotheses regarding source of the originalseawater that fed this saline giant in the deep Gulf ofMexico basin. Our restoration shows narrow gatewaysto the Atlantic Ocean, from the deep Louann basinthrough the Florida straits, Northern Cuba and theBahamas. The chain of narrow basins connecting theAtlantic to the Gulf may have acted to deplete incom-ing seawater of all but Na and CL, evidenced by theremarkably pure Louann halite in the deep basin (Peel,this volume). The mapped configuration of narrow pas-sages in the eastern Gulf of Mexico and dominance ofbasin marginal anhydrite in Mexico (versus halite else-where) also leads one to question the conventionalmodel of a marine connection between the Louannbasin and the Pacific Ocean. Pacific affinity macro-fauna, originally a critical data point supporting thePacific seawater entry model, are now known to beyounger than the Louann salt.

Salt is a critical component of the prolific Gulf ofMexico petroleum system, setting up traps, providingtop seal, and mitigating heat flow so that Mesozoicsource rocks generate later in the basin burial history.Understanding the original distribution of Louann saltis also essential to basin modeling and structuralrestorations.


Intrasalt Structure and Strain Partitioning in Layered Evaporites: Insights from the Messinian Salt in the Eastern Mediterranean

Sian L. EvansBasins Research Group (BRG)Department of Earth Science and EngineeringImperial College LondonPrince Consort RoadLondon, SW7 2BPemail: [email protected]

Christopher A.-L. JacksonBasins Research Group (BRG)Department of Earth Science and EngineeringImperial College LondonPrince Consort RoadLondon, SW7 2BP

Abstract

Determining the composition and internal struc-ture of salt bodies is important for safe drilling throughthick salt sequences and enables us to build bettervelocity models that allow more accurate seismicimaging of near-salt geology. However, due to typicallypoor seismic imaging within salt bodies, and a lack ofoutcrop and well data, the nature of the lithologicalcontrol on intrasalt deformation is still poorlyunderstood.

The Messinian evaporites are lithologically het-erogeneous, shallowly buried, and only weaklydeformed along the Levant Margin in the eastern Medi-terranean. The halite-dominated units are interbeddedwith other evaporitic minerals (e.g., anhydrite, gypsum,potash salts) in addition to clastic units. This lithologi-

cal heterogeneity leads to rheological heterogeneity,and the different mechanical properties of the variousrock types control strain partitioning within thedeforming salt sheet.

A large, high resolution 3D seismic reflectiondata set provides us with an opportunity to assess howintrasalt strain varies within thick salt (up to 2 km)during the early phase of evaporite deformation. Wecalculate strain on individual reflectors and show thatstrain varies laterally and vertically across the contrac-tional domain of the Levantine Basin. These resultsprovide insights into how seismically derived strainprofiles may reflect the rheological properties of thedeforming units and changes in the kinematic evolutionof the salt sheet through time.


Salt Tectonics Within Strike-Slip Systems, Campos Basin, Brazil

Stephanie WischerWebster MohriakRio de Janeiro State University (UERJ)Rio de Janeiro, Brazilemail: [email protected]

Abstract

The Campos basin is a well-studied, economi-cally important basin located in the southeasternBrazilian coastal margin. Salt tectonics play an integralpart in the basin’s development by deforming the over-lying postsalt sedimentary package and forming avariety of extensional and contractional structures. Themajority of the salt structures within the basin are ori-ented perpendicular to the evaporite flow direction,which radiates seaward from the continental shelfbreak. As such, the basin is structurally similar to mostother salt-bearing Atlantic passive margin basins.However, the north-central portion of the basin ismarked by several peculiar structural elements, such asthe presence of northwest trending lineaments andfaults near the Roncador and Frade oil fields.

This portion of the basin contains reactivatedbasement faults that, together with salt tectonics, haveformed important controls for the structural and strati-graphic features found in the deep-water. These localreactivations have (re)deformed the earlier salt struc-tures previously formed by gravitational gliding andcreated a disparity with the previously defined passivemargin setting.

2D and 3D seismic data integrated with well con-trol covering the northern Campos basin were

interpreted in order to characterize Late Aptian saltstructures and were used to investigate the structuralcontrols involved in their development focusing on theMaastrichtian-Aptian interval. Analysis of the inter-preted 3D seismic showed that the salt-sedimentrelationship was further affected in some areas bystrike-slip systems and associated basementreactivations.

Salt structures within the study area are associ-ated with basement highs and have been (re) orientedinto west-northwest/east-southeast alignments, whichis parallel to sub-parallel with the original evaporiteflow direction. Structures include a dextral strike-sliprhombic graben at the Albian level and a still-activestrike-slip fault system which forms a large horst thatlimits a salt body within its normal faults. Developmentof the northwest and east-west trending shear zonesand reactivation of north-northwest/south-southeastextensional basement-involved faults act to control thegeometry of the salt structures. The presence of thesestrike-slip fault systems and their effect on salt tecton-ics has not been thoroughly characterized previously.The recognition of these features may impact the inter-pretation of similar features in other parts of theCampos basin and elsewhere.


Evolution of Megaflaps, Extensional-Rollover Subbasins, and Salt-Withdrawal Minibasins at Aulet and Adons Diapirs in the Spanish Pyrenees, Catalunya

C. Evelyn Gannaway DaltonInstitute of Tectonic StudiesThe University of Texas at El Pasoemail: [email protected] A. GilesInstitute of Tectonic StudiesThe University of Texas at El Paso

Josep Anton MuñozGeomodels Research InstituteUniversitat de BarcelonaMark G. RowanRowan Consulting, Inc.

Abstract

The Aulet and Adons diapirs in the south-centralPyrenees have been variously interpreted as salt rollersor passive diapirs derived from Triassic Keuper evapo-rites. They are flanked by upper Albian to Turonianstrata in three domains (Sopeira, Faiada, Sant Gervàs)correspondingly interpreted as extensional rolloversubbasins or salt withdrawal minibasins. Pyreneanshortening resulted in contractional megaflaps in theSopeira and Sant Gervàs domains, but the alternativesalt structures and domain origins have significantimplications on interpretations of subsurface geome-tries. We use sedimentologic and stratigraphic analysisto resolve if the Aulet and Adons diapirs evolved assalt rollers or passive diapirs, followed by structuralanalysis to interpret the kinematics of megaflap rota-tion during the Pyrenean Orogeny.

The Sopeira domain, south of the Aulet diapir,contains subvertical Aulet Fm. preserving an expandedcarbonate ramp shoreface succession showing broadfacies and thickness changes in the lower Aulet Fm.,minimal variations in the upper Aulet Fm. except iso-lated slump blocks, and no evidence of passivediapirism. This suggests the Sopeira domain evolved as

an extensional-rollover subbasin bound by the Auletsalt roller to the north and a buried salt roller to thesouth. The Sant Gervàs domain, south of the Adonsdiapir, contains completely overturned Santa Fe, Par-dina, and Agua Salenz strata. The subsurface geometryis uncertain, but an extensional-rollover origin, boundto the north by the Adons salt roller and to the south bya buried salt roller, best explains the salt-sediment rela-tionship and most realistically allows for later rotationto completely overturned. The Llastarri fault zone,interpreted as a buried salt ridge, was first part of thelateral margin of the older Sopeira basin, sourcingslump blocks, and later was the lateral footwall of theyounger San Gervàs basin. The Faiada domain, west ofthe Adons diapir, comprises an anomalously expandedSanta Fe, Pardina, and Agua Salenz succession withdiapir-derived detritus and halokinetic sequences, indi-cating at least some salt evacuation adjacent to apassive interface of the Adons diapir. Structural analy-sis highlights the impact of inherited extensional vs.passive salt structures on Pyrenean shortening andmegaflap rotation.


The Age of the Louann Salt; Insights from Historic Isotopic Analyses in Salt Stocks from the Onshore Interior Salt Basins of the Northern Gulf of Mexico

Andrew J. PulhamEarth Science Associates C&T Inc.5312 Gallatin PlaceBoulder, Colorado 80303, USAemail: [email protected] J. PeelBureau of Economic GeologyUniversity of Texas at AustinAustin, Texas 78713-8924, USAemail: [email protected] RivesTOTAL E&P Americas LLC1201 Louisiana Suite 1800Houston, Texas 77002, USAemail: [email protected] DelphKosmos Energy Limited,15011 Katy Freeway, Suite 700Houston, Texas 77094, USAemail: [email protected]

Jean-Francois SalelTOTAL E&P Americas LLC1201 Louisiana Suite 1800Houston, Texas 77002, USAemail: [email protected] NicholsonKosmos Energy Limited8176 Park Lane, Suite 500Dallas, Texas 75231, USAemail: [email protected] WuTOTAL E&P Americas LLC1201 Louisiana Suite 1800Houston, Texas 77002, USAemail: [email protected] Requejo611335 Twain DriveMontgomery, Texas 77356, USAemail: [email protected]

Abstract

The Louann Salt is an evaporitic successiondeposited in the Gulf of Mexico during the latter stagesof Mesozoic-age crustal stretching and likely immedi-ately prior to oceanic spreading in the basin. Theimportance of the Louann cannot be overstated, partic-ularly to the petroleum systems of the Gulf of Mexico.Since its precipitation, the original Louann has been onthe move, leaving autochthonous remnants and result-ing in a myriad of allochthonous and para-autochthonous intrusive diapirs, stocks, sheets, cano-pies, wings, etc. At a reservoir scale, and there arenumerous Gulf of Mexico productive units throughoutthe Mesozoic and Cenozoic, the age of the Louann canbe regarded as somewhat academic. At a regional andbasin scale the tectonostratigraphic architecturesrevealed by remote sensing techniques (seismic reflec-tion, gravity, and magnetic surveys, etc.) are poorlyconstrained by absolute ages at the level of the Louannand the continental-dominated stratigraphy that pre-dates and immediately post-dates the evaporites.

Since the late 1980s, the Louann salt has beeninterpreted as Middle Jurassic-Callovian in age, notexclusively but this is the default interpretation in most

publications that refer to the Louann. This age datingapproach has been called “stageology” by a respectedcolleague and is a well-established practice of conve-nience when absolute age is uncertain. The assignedage of Callovian for the Louann may well be correct. Inthe spirit and theme of this meeting we revisit the ageof the Louann salt and explore an alternate ageinterpretation.

The study presented here was part of an investi-gation undertaken originally by Cobalt InternationalEnergy and Total E&P Americas, and continued byTotal, that sought to constrain the timing of Jurassicevents in the offshore Eastern Gulf of Mexico (EGoM).Biostratigraphic data from wells encountering marineJurassic in the offshore EGoM provide some indicationthat post-Louann stratigraphy is as old as Callovian,albeit with uncertainties. Also, in the EGoM is a seis-mically mapped succession above the Louann that is upto 8,000 feet in thickness, named the Sakarn series inthis volume. This succession has not been encounteredby the numerous wells that penetrate autochthonous orquasi-autochthonous salt in the onshore interior saltbasins of the Northern Gulf of Mexico but implies


additional time post-Louann and prior to the onshoreand offshore aeolian-fluvial deposits of the NorphletFormation. The question being asked in our explorationteam in 2015 was; “Does the Callovian have the tem-poral capacity; 2.6 Ma, to contain the entire Louannand the Sakarn series, and perhaps also including theincreasingly economically important NorphletFormation?”

Our investigations lead to US AtomicEnergy Agency (AEA) and US Department of theInterior projects that, in part, extensively drilledand cored Louann salt diapirs across the onshoreNorthern Gulf of Mexico during the post-WWIIperiod and up to the early 1960s. These AEA proj-ects were concluded by the end of the 1980s; soonafter, organic and inorganic analyses of the exten-sive US Government Louann cores started toappear in peer reviewed journals. Within thesegeochemical data are isotopic analyses including87Sr/86Sr results from deep within the salt stocks of

Louann diapirs. In the intervening two to threedecades, the Phanerozoic record of 87Sr/86Sr values inthe world’s ocean has been refined and a robust recordnow exists for the Jurassic.

Comparison of the 87Sr/86Sr data derived fromAEA Louann core samples against the 87Sr/86Sr recordfor the Jurassic provide an intriguing option for inter-pretation of the Louann age. We propose that an agewindow of early Bajocian through early Callovian;~170 Ma to ~165 Ma, 5 m.y. of duration, should beconsidered for the age of the Louann and for the 6,000ft of post-Louann sediments in the EGoM. This timewindow is far from certain. New isotopic data may wellrefine a time window greater or shorter than we sug-gest. Establishing a robust age for the Louann will helpin refining tectonostratigraphic models for the earlyhistory of the Gulf of Mexico Basin. Existing isotopicanalyses offer a guide and new isotopic analyses maydeliver a solution.


Middle Jurassic Tectonic Models for the Gulf of Mexico in Light of New Bajocian Ages for Proximal Margin Salt Deposition

James PindellTectonic Analysis Ltd. and ION E&P Advisors Chestnut House, Burton ParkDuncton, West Sussex GU28 0LH UKemail: [email protected] VillagómezTectonic Analysis Ltd. and University of GenevaRue des Maraichers 13CH-1205 Geneva, Switzerland

Brian W. HornION E&P Advisors2501 City West BoulevardHouston, Texas 77042, USARoberto Molina GarzaCentro de GeocienciasUniversidad Nacional Autónoma de México Campus Juriquilla, Querétaro, México

Abstract

Recent Bajocian Sr87/86 ages (169 Ma) forLouann, Campeche, and other evaporite samples in thenorthern, southern, and western proximal rims of theGulf of Mexico Basin (GoM) suggest that new per-spectives on the basin’s rift and drift history arewarranted. Presently, sea-floor spreading is believed tohave started in the Oxfordian because (1) salt is usuallyconsidered Callovian-early Oxfordian and the basin-ward limits of Louann and Campeche salt, having beenseparated by spreading, closely match the limits of theintervening oceanic crust; and (2) Yucatán and thereconstructed, little-faulted, base-salt unconformityalong GoM margins can be accommodated neatly intocurrent early Oxfordian (~160 Ma) North America-South America tectonic reconstructions. However,reconstructions for Bajocian time (~169 Ma) generallydo not accommodate the great area of this nearly planarunconformity. Three possible explanations are evalu-ated here: (1) that Bajocian North America-SouthAmerica reconstructions are too tight; (2) that saltdeposition began in the Bajocian but persisted throughBathonian–early Oxfordian time before spreading andhence offlapped from the dated locations along theproximal GoM margins; and (3) that all salt is Bajo-cian, but that it flowed basinward to the eventual line ofinitial Oxfordian spreading. We assess explanation 1by a sensitivity analysis of the Equatorial Atlantic com-ponent of the circum-Atlantic reconstruction,concluding this option is viable. If correct, explanation1 implies a Bathonian rather than an Oxfordian onset ofseafloor spreading, along with several other important

aspects of GoM evolution. Explanations 2 and 3 implyongoing Bathonian-early Oxfordian basement expan-sion which is not readily identifiable in seismic data,but which might be allowable if the base-salt surfacebeneath the Sigsbee slope is eventually shown to benon-planar and if salt deposition is shown to beyounger in the eastern GoM than in the western/centralGoM. These options will thus remain viable unless Srisotope ages for distal salt eventually prove to be Bajo-cian, as in the proximal margins. We find explanation 3least likely because littoral-neritic paleo-environmentalassignments for Upper Jurassic strata in certain off-shore wells suggest maintenance of shallow waterconditions above salt far into the offshore and henceonly minor salt deflation by that time. The new agessuggest that the Huayacocotla area of central, continen-tal Mexico is the most likely link to the world ocean inBajocian time because Bajocian-Bathonian Huehuete-pec and equivalent evaporites occur there. Further, wehighlight and suggest alternatives for resolving a long-standing conundrum posed by the thin salt packagelying upon the little-faulted, postrift, base-salt uncon-formity in the eastern GoM that lies at the samestructural level as the oceanic crust. We suggest thatdeep-water salt deposition may provide a viable alter-native explanation to outer marginal collapse at the rift-drift transition. Finally, we present a 195 Ma (EarlyJurassic) reconstruction using the looser EquatorialAtlantic fit which shows that the looser fit accords wellwith reconstructions of western Pangea.


Paleo-Oceanographic Preconditioning Promotes Precipitation: How the Global Context is a Key Factor for Understanding Bajocian Louann Salt Deposition

Frank J. PeelApplied Geodynamics Laboratory Bureau of Economic GeologyThe University of Texas at AustinUniversity Station, Box XAustin, Texas 78713-8924email: [email protected]

Abstract

The Louann Salt of the Gulf of Mexico (GoM) isstrikingly different from most other halite giants;unstratified and with no Usiglio sequences; it consistsmostly of halite intimately mixed with anhydrite. Themeasured CaSO4 content is lower than that of normalseawater. An evaporite unit deposited by full evapora-tion of seawater of normal composition (Babel andSchreiber, table 1, 2014) should contain ca. 4% byweight CaSO4 (anhydrite plus gypsum recalculated asCaSO4). This is consistent with experimental evapora-tion; the classic data of Usiglio (1849) gives 4.4% byweight CaSO4 (Dean, 1987). However, compositionalmeasurements of the Louann indicate a significantlylower value. Figure 1 compares the predicted weightfraction of CaSO4 with observed composition of Gulfof Mexico salt bodies based on data from individualwells and mines (Martinez et al., 1979; Dix and Jack-son, 1981; Land et al., 1988; Fredrich et al., 2007).Dissolution by groundwater flow around shallow dia-pirs results in concentration of less solublecomponents, as shown in Figure 2A, (Kyle and Posey,1991; McManus and Hanor, 1993), but the geometry ofdeep-water salt sheets is less favorable to large scaledissolution (Figure 2B) and the observed mean wt%CaSO4 for deep-water salt sheets (2.03%) is probablycloser to that of the original Louann. Thus the Louannis significantly deficient in CaSO4; this compositioncannot simply be achieved by evaporation of raw sea-water. The simplest explanation for the observedsulphate deficiency is that the water from which theLouann was deposited had already been pre-processedon its journey through a chain of basins before itreached the Gulf of Mexico; i.e., the missing sulphateexists, but it was deposited in another basin.

Hitherto, the Gulf of Mexico basin has been seenin a relatively local context, initially with a restrictedconnection to normal oceanic water, either eastwardsinto the Tethys ocean via the North Atlantic (e.g., Pin-dell and Kennan, 2001), or westwards into the Pacific(Berggren and Hollister, 1977; Salvador, 1991). TheLouann has conventionally been thought to be of earlyCallovian age, but 87Sr/86Sr strontium isotope dataindicates that the Louann is older, deposited at ca. 170Ma (early Bajocian), (Pulham, 2016 pers. com.; Pul-ham, et al., 2019). Assigning an older (Bajocian) age tothe onset of salt deposition changes the balance of evi-dence towards an easterly water source. Ammoniteprovinces described by Callomon (2003) demonstratethat, throughout the Middle Jurassic, the basin chainwas linked eastwards to the Tethyan Ocean, and attimes northwards to the Boreal Sea, but a fully openwestwards connection to Pacific fauna did not comeinto existence until the Late Jurassic. As shown by Sco-tese (2013), the mid-Jurassic Gulf of Mexico is betterviewed as a Tethyan rather than an Atlantic basin,

The global plate tectonic context of the Gulf ofMexico at 170 Ma (Fig. 3) shows that the Louann wasdeposited in a rather special plate setting related to theinitial breakup of Pangea (Veevers, 2004); it lies at thewestern end of a chain of newly opening basins in themiddle of a supercontinent. Breakup occurred as Gond-wana and Laurasia progressively “unzipped”westwards, so that basins in the east opened earlier andat any given time tended to be wider than those in thewest. Major rift regions and early ocean basins, withinwhich water could circulate, were separated by strike-slip dominated zones which formed choke points,restricting ocean circulation between the basins. Figure4 shows the paleogeography of one such choke, con-


necting the Tethys and the Central Atlantic (adaptedfrom Sibuet et al., 2012). Plate reconstructions indicatethat the gap between continental basement blocks wasnarrow, but a full paleo-oceanographic reconstructionmust also incorporate the effects of sediment deposi-tion. In this region, deposition of platform carbonatesin the southern straits and deposition of marine mudand clastic sediments in the northern straits has theeffect of making the marine connection narrower andshallower. Water flowing from the Tethys into the Cen-tral Atlantic did so by an extremely restricted andshallow connection, and it can only have involved theshallowest part of the water column.

Figure 5 shows the connection between theLouann Sea (the water body occupying the early Gulfof Mexico at the time of salt deposition) and the proto-Caribbean, based on detailed 2D seismic mapping on a5-10km grid spacing by the author and MagdalenaCurry. This reveals a well-defined channel systemfeeding the Louann Sea, which was 500km long, tortu-ous, and in places both narrow and shallow. The authorsuggests that flow through this system is likely to havebeen one-way with no return flow component.

The climate within the middle of the fragmentingPangea supercontinent was hostile. The entire chain ofbasins lay within the low humidity arid tropic zone,within the center of a supercontinent; its western partwas flanked by sand deserts (San Rafael Group), andaverage summer temperatures probably exceeded100ºF (Harris et al., 2017). Conditions were ideal forrapid water evaporation; climate modeling (Chandler et

al.,1992) indicates that water loss by evaporationexceeded gain by precipitation across the entire west-ern Tethys, resulting in net evaporation in excess of2m/yr in the region of the Louann basin. However,salinity enhancement by evaporation was countered bythe flushing effects of strong marine currents passingthrough the basin chain (Figure 6A). Of these, the mostsignificant was the Viking current, which effectivelyflushed the entire eastern half of the basin chain (Korteet al., 2015). At the start of the Aalenian, mantle upliftraised the North Sea region, blocking the Viking cur-rent (Underhill and Partington, 1993), turning the basinchain into a dead-end street and allowing potentialsalinity buildup. The onset of salt deposition appears tohave been delayed by a regional climatic cooling event,as temperatures dropped by 15℃ in the early Aalenian(Korte et al. 2015). At the start of the Bajocian, thiscold period ended (Suchéras-Marx, 2013), as δ18Omeasurements in oyster and belemnites show thatTethyan water grew significantly warmer (Dera et al.,2011). Climatic and paleo-oceanographic conditionswere now perfectly set up for westwards-increasingbrine concentration throughout the chain. The authorsuggests that concentration to the point of gypsum/anhydrite precipitation was reached in the area of theproto-Caribbean, so that the brine passing onwards intothe Louann basin was both highly concentrated in NaCland partially depleted in CaSO4. This enabled veryrapid precipitation of the Louann salt giant andexplains the observed sulphate deficiency.


Synthesizing Old Questions with New Developments in Caprock Research: Is it Time to Abandon Well-Trodden Paths?

Benjamin [email protected] L. LabradoGail L. ArnoldJulia AstromovichClaire BaileyThe University of Texas at El Paso500 W. UniversityEl Paso, Texas 79968Stefano M. BernasconiGeologisches InstitutETH ZurichNO G51.3Sonneggstrasse 58092 Zürich, SwitzerlandKyle DeatrickHanah DraperThe University of Texas at El Paso500 W. UniversityEl Paso, Texas 79968Frederic O. EscosaUniversity of BarcelonaGran Via de les Corts Catalanes, 58508007 Barcelona, SpainC. Evelyn Gannaway DaltonElizabeth A. HenessMuhammed Tarik IrazThe University of Texas at El Paso500 W. UniversityEl Paso, Texas 79968Jessica Thompson JobeDept. of Geology and Geological EngineeringColorado School of Mines11500 Illinois St.Golden, Colorado 80401

Rachelle KernenDavid Lankford-BravoKevin LererAlly MastJosh McFarlandThe University of Texas at El Paso500 W. UniversityEl Paso, Texas 79968Jörn PeckmannUniversität HamburgInstitut für GeologieGeomatikum, Raum 1011D-20146 HamburgPiper PoeRyan RonsonThe University of Texas at El Paso500 W. UniversityEl Paso, Texas 79968Austin ShockOccidental Petroleum (Oxy)5 Greenway Plaza Suite 110Houston, Texas 77046Katherine GilesThe University of Texas at El Paso500 W. UniversityEl Paso, Texas 79968

Abstract

In 1901, the Lucas Gusher at Spindletop saltdome marked the beginning of the Texas oil boom inthe USA. The reservoir rock at Spindletop is carbonatecaprock. Originally identified as dolomitic caprock, itnot only yielded oil, but also large quantities of nativesulfur. However, more than a century later, major gapsremain in the understanding of how caprocks form.

Caprocks are found at the top of salt diapirswhen dissolution of readily soluble halite (NaCl) leadsto the accumulation of less soluble calcium sulfateminerals, such as anhydrite (CaSO4) and gypsum(CaSO4•2H2O), as well as other insoluble constituents.When the sulfate minerals come into contact with oil orgas, the sulfate is thermochemically or microbiologi-



cally reduced to sulfide and the oil or gas are oxidizedto carbonate, driving the transformation of anhydriteand gypsum into limestone (CaCO3) along with theproduction of sulfide and/or native sulfur. Caprocksremain on top of the salt diapir or are rotated off into aflanking/lateral position. They may serve as reservoirs,traps, seals, or conduits for oil or gas but may also posedrilling hazards. Interestingly, in the Gulf of Mexico,with the exception of near-coastal sites, caprock isoften considered to be absent at most offshore saltdomes, but it is present at Challenger Knoll at a waterdepth of 3700 m in the center of the Gulf.

Over the last decade, the salt-sediment interac-tion research consortium at The University of Texas atEl Paso has made a number of discoveries that mayreshape the understanding of caprock formation. Theseinclude:

There are a much wider variety of caprock fab-rics than previously reported.

The geochemistry of Gulf Coast salt diapir cap-rocks indicates heat-loving microbes (thermophiles)

generate native sulfur from sulfate without requiringmolecular oxygen, challenging the paradigm thatmolecular oxygen is critical for the genesis of largenative sulfur deposits.

Steeply dipping carbonate lithologies foundbetween diapirs and adjacent strata can representrotated diapir-flanking caprock but can also correspondto upturned older strata or carbonates formed in a basinnext to an exposed diapir.

Petrographic-geochemical studies of caprockfrom the Gypsum Valley salt wall in Colorado indicatethat dolomite (MgCa(CO3)2) is an early carbonatephase, generating the conundrum of how replacementof calcium sulfate minerals can result in the formationof a carbonate rock with high magnesium content.

These surprising insights exemplify that muchremains to be learned about caprock formation and thatcarbonate and sulfur minerals may serve as untappedarchives of the history of fluid flow and hydrocarbonmigration in settings with active salt tectonics.


Minibasins Involved in Fold and Thrust Belts: From Their Development in Passive Margins to Contractional Reactivation (Examples from the Northern Calcareous Alps, Pyrenees and Experimental Modeling)

J. A. Muñozemail: [email protected]. GranadoE. RocaP. Strauss*O. FerrerP. SantolariaO. GratacósN. CarreraJ. MiróE. Wilson

Geomodels Research InstituteDepartament de Dinàmica de la Terra i de l’OceàUniversitat de BarcelonaMartí i Franquès s/n 08028Barcelona, Spain*also with:OMV Austria Exploration and Production GmbHTrabrennstrasse 6-8, 1020Vienna, Austria

Abstract

It is well known that the presence of salt horizonsand salt structures have a strong influence on the struc-tural style of fold-and-thrust belts. They also affect theinversion of rift basins that form during lithosphericstretching preceding thermal subsidence and passivemargin development. However, minibasins and saltstructures that form after rifting ceases have onlyrecently been recognized in orogenic systems such asthe Northern Calcareous Alps or the Pyrenees. We aimto characterize the structure of inverted minibasins butthe challenge is to understand, and match, the present-day contractional structure with a reasonable preoro-genic configuration. Yet, we still lack a properunderstanding on the development of these salt-sedi-ment systems and particularly, how salt tectonics istriggered and evolves through space and time. Twofundamental triggering mechanisms of passive marginsalt tectonics are known: (1) extension, by gravitationalcollapse and gliding, and (2) differential loading. A keyquestion is: do these mechanisms occur at the sametime or does one commonly follow the other? In thelatter case, which one is first? Which one dominates?Does it depend on the location and timing of deforma-tion on the passive margin?

In this contribution, we provide several casestudies from the Pyrenees and the Northern CalcareousAlps (Austria), both examples of fold-and-thrust beltsthat have deformed passive margins involving salt-basins. We investigate these contractional systems bygeological mapping, cross-section construction, and

structural restorations. Uncertainties are reduced by (1)integrating subsurface data if available, (2) by means ofexperimental modeling studies, and (3) by comparisonto present day continental margins.

The Pyrenees involved the North-Iberian passivemargin where salt tectonics was triggered by extensionduring Late Jurassic-Early Cretaceous rifting. It contin-ued during the subsequent early Late Cretaceousthermal phase preceding the onset of contraction. Saltstructure location was fundamentally controlled by thedistribution (and redistribution) of the Triassic salt.Extensional collapse occurred at the edge of saltinflated areas, mainly at the footwall of the main rift-margin extensional faults, and preferentially in therelay zones of the segmented Pyrenean rift system.Basinward, halokinetic geometries reveal that salt-withdrawal minibasins also occur, these depocentersshifted from those of the previous rift basins.

Recent field work and analysis of existing datafrom the Northern Calcareous Alps fold-and-thrust beltof Austria has shown characteristic structural stylesrelated to salt tectonics: (A) multiple structural orienta-tions for folds and faults, (B) strong changes in foldplunges, (C) large panels of fully overturned stratigra-phy (e.g., such as megaflaps), (D) mechanical contactsomitting or repeating stratigraphy (i.e., apparent exten-sional faults passing laterally into reverse/thrust faults),and (E) stripes of severely deformed evaporites or theirequivalent leached remnants (i.e., salt welds, thrustwelds) that bound thrust units having markedly differ-


ent sizes and contrasting stratigraphic thicknesses.These features point out the reactivation of structuresinvolving Permian salt. Similar to the Pyrenees, exten-sional collapse of the late rift to post-rift sequencesoccurred at the edge of a salt basin. Basinward, miniba-sins characterized by highly subsiding carbonateplatforms formed by salt evacuation of inflated areas,with carbonate aggradation at rates larger than thoseprovided by thermal subsidence alone (~2 km/m.y.).

In both contractional systems (i.e., the Pyreneesand the Northern Calcareous Alps), Alpine orogenicshortening has completely sheared off the sedimentarycover from its original presalt rifted basement; hence,the relationships between salt structures, with thosestructures responsible for crustal thinning have beenlargely obscured. The present structure of the miniba-sins in the Pyrenees and the Alps is characterized bylarge panels of vertical to significantly overturned sedi-

ments. At some places, overturned panels involve arelatively reduced succession away from the minibasindepocenters and have been interpreted as the result ofcontractional deformation in sediments overlying thesalt inflated areas. However, a problem lies in the inter-pretation of vertical to overturned panels (megaflaps)involving the depocenters of the minibasins. Experi-mental models show a moderate amount of rotationduring the contractional deformation of salt-with-drawal minibasins. This emphasizes that inversion ofsalt rollers and minibasins developed by extensionalcollapse, and probably above a stepped base salt topog-raphy, better explain the presence of such large andthick overturned megaflaps. Field evidence from theAlps and the Pyrenees also suggest that components ofpassive margin thin-skinned extension and downbuild-ing better explain the current contractional structure ofthese salt-influenced fold-and-thrust belts.


Applications of Biostratigraphy to Salt Tectonics, Northern Gulf of Mexico

Richard DenneTexas Christian UniversityDepartment of Geological SciencesTCU Box 298830Fort Worth, TX 76129email: [email protected]

Abstract

Biostratigraphy provides rock-based interpreta-tions of the age and depositional setting of strata whichcan be used to constrain structural and stratigraphicreconstructions of salt-deformed terranes. Data fromseven wells drilled in the deep-water northern Gulf ofMexico are used to demonstrate the use of biostrati-graphic data in differentiating suprasalt minibasinsfrom condensed carapace sections, identifying salt

welds, providing age control for salt inclusions, andproviding evidence for subsalt rubble zones and over-turned sections. In particular, the use of plankticmicrofossil and agglutinated benthic foraminifer abun-dances and rock accumulation rate curves areespecially useful in determining the depositional set-ting for out-of-place sections.


On Elevators and Bulldozers: What has Changed in Salt Tectonics? Examples from Passive Margin Salt Basins

Hermann LebitPGS Catalina Luneburg; TerraEx GroupHouston, Texasemail: [email protected]

Abstract

Salt tectonic studies emerged with the mining ofsalt stocks and early hydrocarbon exploration predomi-nantly in the Paleozoic salt basins of Europe(Trusheim, 1960; Jackson 1995; Stobova and Stephen-son, 2002). These intracontinental basins have evolvedunder tectonic conditions allowing salt structures togrow under regionally homogeneous stress conditions.Salt basins in other tectonic domains, such as fold andthrust belts or passive margins, have undergone differ-ent tectonic conditions controlling the development ofsalt structures.

In recent decades, focus has shifted to the mar-gins of continents where prolific hydrocarbon systemsare present. Many continental margins have accumu-

lated significant salt (evaporite) deposits during thetransition period from crustal extension to seafloorspreading (Hudec and Jackson, 2007; Jackson andHudec, 2005). Thermal subsidence dominates duringthe subsequent passive margin evolution introducing aslope towards the evolving oceanic lithosphere. Thedeveloping slope gives rise to lateral displacement gra-dients, which are superimposed by sedimentary loadingand eventually propagate into the evolving accommo-dation space (Fig. 1). Gravity is the driving force inthese passive margin systems, imposing an overall lat-eral displacement field that differs significantly fromthe vertical gradients in intracontinental settings(Fig. 1).


Salt Tectonics in the Brazilian Margin: Key Issues and Technical Advancements in the Past 30 Years

Webster MohriakState University of Rio de JaneiroFaculty of GeologyRio de Janeiro, Brazilemail: [email protected]

Abstract

The Brazilian salt basins belong to the SouthAtlantic salt province formed in the Early Cretaceousas a consequence of the Gondwana breakup and extendfrom the southern Santos basin towards the Sergipe-Alagoas basin in the northeast. Salt tectonics studies inthe past 30 years resulted in outstanding technicaladvancements and a much-improved understanding ofsalt sequences distribution along the various sedimen-tary basins along the eastern Brazilian margin. This hasled to giant hydrocarbon discoveries in the ultradeepwater regions of several salt provinces, particularly

within the Santos, Campos, and Espírito Santo basins.This work addresses some of the key issues in the salttectonics studies developed in the southeastern Brazil-ian margin in the past few decades, focusing onalternative interpretations of the Cabo Frio fault zone,between the Santos and Campos basins, the stratifiedevaporites in the distal Santos basin, the allochthonoussalt play in the northern Espírito Santo basin, andstrike-slip salt tectonics associated with the Frade Fieldin the northern Campos basin.


A Critical Review of Models for Deposition of the Louann Salt, and Implications for Gulf of Mexico Evolution

Michael R. HudecFrank J. PeelBureau of Economic GeologyJackson School of GeosciencesThe University of Texas at AustinAustin, Texas, U.S.A.email: [email protected]

Abstract

Two interpretations drive models for Louann saltdeposition in the Gulf of Mexico. First, it appears thatsalt at the landward edge of the basin was depositednear sea level. Second, it appears that salt at the sea-ward end of the basin was deposited at oceanic depthsshortly after salt deposition.

Three published models for Louann salt deposi-tion attempt to reconcile these interpretations. In theouter-marginal-collapse model, salt was deposited atsea level in a basin undergoing rapid tectonic subsid-ence. Continued subsidence after salt deposition tiltedthe basin seaward, placing the downdip end in deepwater. In the postsalt-crustal-stretching model, salt wasdeposited in shallow water in a pre-existing depression,eventually filling the basin to sea level. Crustal stretch-ing after the end of salt deposition thinned the salt,

eventually dropping the center of the basin down todepths comparable to oceanic crust. Finally, the high-relief-salt model suggests salt was deposited in a basinhaving several kilometers of depositional relief.

Each of these models has drawbacks in the Gulfof Mexico. For the outer-marginal-collapse model,numerical simulations of rifting do not produce theabrupt, late-stage collapse required by the model. Forthe postsalt-crustal-stretching model, there does notappear to be sufficient late-stage crustal extension. Thehigh-relief-salt model requires a type of salt depositionfor which there are no modern analogs. More data,especially from the downdip ends of the salt basin,would help narrow down the possibilities or contributeto a new model.


Salt Tectonics Controls on Deepwater Sedimentation: Salina del Istmo Basin, Southern Gulf of Mexico

Clara Rodriguez email: [email protected] Hernandez Casado email: [email protected] Ysaccis email: [email protected] Villarroel email: [email protected] Lyons email: [email protected]

Maxim Mikhaltseemail: [email protected] El-Toukhy email: [email protected] Richmond AvenueHouston, Texas 77042

Abstract

The Salina del Istmo Basin, also known asCampeche Salt Basin, is characterized by a complexstructural evolution controlled by a combination of salttectonics, gravity-driven extension, onshore uplift, andregional shortening. There are only a few studies in thesouthern Gulf of Mexico and these are mainly based onsparse 2D regional seismic lines. Due to the structuralcomplexity and the lack of previous studies, it isunclear how primary salt movement alone and in com-bination with regional tectonic events has controlledthe distribution of reservoir-prone sediments. Based ona basinwide (71,000 sq. km) 3D seismic interpretation,we reveal new insights about the temporal and spatialvariations of deep-water sedimentation and the explo-ration significance basinward (water depths rangingfrom 250 m to 3750 m) of the 2017 Zama-1 oil discov-ery. The data consists of a 3D wide-azimuth,broadband depth-imaged seismic reflection volumeacquired between 2015 and 2017.

The present day structural and stratigraphic com-plexity of the basin is illustrated by folding, thrusting,and complex dissection of submarine channels, deposi-tional lobes, and mass transport complexes.Nevertheless, detailed seismic stratigraphic mappingand geomorphological analysis suggest that primary

salt movement started in the Eocene and continuedduring the Oligocene. During this initial phase, salt-related highs locally diverted and laterally and frontallyconfined deep-water depositional systems.

Further confined sedimentation continued in thelower Miocene resulting in local welding of primaryminibasins, inversion of minibasin stratigraphy, and theformation of turtle structures. These observations arealso locally recognized in isopachs and seismic attri-butes below allochthonous salt sheets and canopies.Orogeny-driven shortening events in the Miocene ledto further lateral and frontal confinement of deep-waterdepositional systems within relatively smaller shorten-ing-related minibasins. The development ofshortening-related minibasins was locally accompaniedby secondary welding and the emplacement of alloch-thonous salt sheets and canopies due to shortening andsalt expulsion from bounding salt diapirs.

Salt tectonics controls during the evolution ofSalina del Istmo Basin have direct implications on res-ervoir distribution and architecture and trapping styles;thus, these observations should be recognized and con-sidered during further hydrocarbon exploration anddevelopment of this frontier basin.


Controls of Interbedded Sand Beds on Pore Pressure, Stresses, and Evolution of a Salt System

Mahdi HeidariMaria A. NikolinakouMichael R. HudecBureau of Economic GeologyThe University of Texas at Austin10100 Burnet Road, Building PRC-130Austin, Texas 78758, USAemail: [email protected]

Peter B. FlemingsDepartment of Geological Sciences and Institute for

GeophysicsJackson School of GeosciencesThe University of Texas at Austin10100 Burnet Road, Building PRC-130Austin, Texas 78758, USA

Abstract

We use a 2D forward finite-element model tosimulate how a salt wall rises, forms a salt sheet, andfinally welds along its feeder in a basin under tectonicshortening for end-member mudrock basins with andwithout interbedded sands. We begin with a flat 3X60km salt layer and sequentially deposit layers of sedi-ments that dip toward the center of the salt layer at aconstant base-level-rise rate. Shortening begins after asalt diapir rises to the basin surface at the center. In themodel with sand beds, sands extend laterally across thebasin to the salt diapir and have a uniform initial thick-ness of 100 m and a vertical spacing of 1 km far fromthe salt wall. Sands and mudrocks both have a poro-elastic-plastic behavior, but sands have different com-pressibility, higher friction angle, and orders-of-magnitude higher permeability than mudrocks. Weshow that sand beds significantly affect pore pressure,stresses, and evolution of the salt system. However,their effects differ substantially before and after theemplacement of the salt sheet.

Before a salt sheet forms, sand beds, dippingaway from the salt wall sub-parallel to the wall’s flank,focus pore water flow along the beds toward the saltwall, (1) increasing pore pressure at the crest of sandsand encasing mudrocks near salt; (2) decreasing thesealing capacity of the mudrocks; and (3) decreasingthe margin of appropriate mud weights for drillingwellbores near salt. In contrast, after a salt sheet forms,sand beds above the diapir’s feeder, extending to and

dipping toward subsalt areas, focus the flow away fromthese areas, decreasing pore pressure and increasing thesealing capacity and appropriate mud weights subsalt.The overall magnitude of overpressure and porosity islower in the basin with sand beds because sand bedsbelow the diapir’s feeder hydraulically connect deepsediments far from salt to subsalt sediments, and sandbeds above the feeder in turn connect subsalt sedimentsto the basin surface, substantially shortcutting thedrainage path of pore water in the basin and therebyresulting in higher overpressure dissipation and basincompression.

We show that at early stages of shortening, whenthe diapir’s feeder is wide, salt expulsion from the dia-pir requires minimal lateral pressure on the diapir, sothe salt diapir is far more deformable than the basin andmost of the shortening is accommodated by the diapirshortening. In contrast, at the late stages of shortening,when the diapir’s feeder is narrow, viscous resistanceagainst the salt flow through the feeder is substantiallyhigh, requiring dramatic lateral pressure on the diapirto expel salt; consequently, the diapir is less deform-able than the basin and most of the shortening isaccommodated by basin shortening through upturningagainst the diapir. Because the basin with sand beds hasless overpressure and higher effective stresses, it isstiffer and upturns less, resulting in a thicker salt sheetto form in the basin with sand beds.


Redirection of Submarine Channels by Minibasin Obstruction on a Salt-Detached Slope: An Example from Above the Sigsbee Canopy

Oliver DuffyNaiara FernandezFrank PeelMichael HudecGillian AppsDallas DunlapBureau of Economic GeologyJackson School of GeosciencesThe University of Texas at Austin University Station, Box XAustin, Texas, 78713-8924email: [email protected]

Christopher JacksonBasins Research Group (BRG)Department of Earth Science & EngineeringImperial CollegePrince Consort Road London, United Kingdom, SW7 2BP

Abstract

As minibasins subside and translate down salt-detached slopes in the presence of significant base-saltrelief, they may weld and be unable to freely translatedownslope. As salt and unwelded minibasins fartherupdip continue to move downslope, they may convergewith, weld against, or overthrust the obstructed miniba-sins. How these processes modify seafloor topographyremains unknown. In this study, we examine howobstruction of minibasins can modify seafloor topogra-phy and reroute deep-water depositional systems.

Seismic attribute analysis reveals how a subma-rine channel system evolves as it passes through acluster of supra-canopy minibasins in the mid-to-lowerslope, before spilling onto the continental rise. At anearly stage, the channel system trends broadly slope-parallel, spilling straight onto the continental rise.However, at a later stage, the channel system isdeflected through 90° in the frontal minibasin to trendbroadly slope-perpendicular, shifting the locus of depo-sition on the continental rise by ~20 km. We usegrowth strata and seismic-stratigraphic relationships

within the minibasins to determine that deviation of thechannel system is broadly coeval with the basal weld-ing, and hence obstruction, of part of the frontalminibasin, and overthrusting of this portion ofobstructed minibasin by an unwelded minibasin on itsupdip side. We argue that overthrusting of the frontalminibasin increases the tectonic load and enhances thesubsidence of its updip side. This topographic loweringthen captures sediment gravity currents that otherwisetrend slope-normal, causing rerouting of the associatedsubmarine channel system and a shift in the deposi-tional locus on the continental rise.

We show that zones of shortening upslope ofobstructed minibasins do not simply act as persistentseafloor topographic barriers to downslope sedimentrouting, as is implied in simple 2-D, fill-and-spill mod-els. Instead, we argue that a more three-dimensional,dynamic salt-tectonic framework is required whenassessing deep-water sediment dispersal on salt-influ-enced slopes.


The European Zechstein Salt Giant—Trusheim and Beyond

Peter A. KuklaGeological InstituteEnergy and Mineral ResourcesRWTH Aachen University52056 Aachen, GermanyJanos L. UraiStructural GeologyTectonics and GeomechanicsRWTH Aachen University52056 Aachen, GermanyAlexander RaithStructural GeologyTectonics and GeomechanicsRWTH Aachen University52056 Aachen, Germanynow with: DEEP.KBB GmbH26160 Bad Zwischenahn, Germany

Shiyuan LiStructural GeologyTectonics and GeomechanicsRWTH Aachen University52056 Aachen, Germanynow with: Department of Engineering MechanicsChina University of Petroleum, BeijingJessica BarabaschStructural GeologyTectonics and GeomechanicsRWTH Aachen University52056 Aachen, GermanyFrank StrozykGeological InstituteEnergy and Mineral ResourcesRWTH Aachen University52056 Aachen, Germany

Abstract

The work of Trusheim in the early 1950s in theGerman Zechstein Salt Basin laid the foundation forinterpreting the kinematic evolution of salt structures.His observations connected salt diapir evolution to sed-imentation. This paper shows examples of how ourunderstanding from Trusheim to today has evolved inthe Zechstein salt giant. We discuss later interpreta-tions of Trusheim’s work and show that his ideas werecloser to our current models than usually thought.Since then, we have seen enormous progress in under-standing of the driving mechanisms, kinematics andgeometries of salt tectonics, but still much can be donein understanding dynamics. Our knowledge of saltbasins has grown mainly by hydrocarbon explorationand production to define the external shapes and kine-matics of salt structures, while the search for nuclear

waste disposal and salt mining explored the internalstructure of salt.

We review work in the Zechstein in the past twodecades which combine geology, geophysics, geo-chemistry, salt rheology, geomechanics, structuralretro-deformation, finite element modeling and analogmodeling towards a more integrated approach to saltdynamics. We show examples of detailed case studiesof multiphase salt tectonics, with 3D seismic linkingthe external and internal structures at scales from 10 mto 100 km, and sedimentary response to multiphase saltmovement. The understanding of internal structures ofthe evaporites, their relationship with salt rheology, andfluid flow through salt at scales of nm to km has con-tributed to better prediction of subsurface integrity,avoidance of drilling hazards, design of salt caverns,and the quest for nuclear waste repositories.


3D Model of Complex Internal Structures in a Northern German Salt Diapir: A Multidisciplinary Approach Using Drilling Cores, Well Logs, and Ground Penetrating Radar

Lukas Pollokemail: [email protected] ThiemeyerMarco SaßnowskiVolker GundelachFederal Institute for Geosciences and Natural

Resources (BGR)Stilleweg 2Hanover, Germany 30655

Abstract

The detailed internal compositions of salt struc-tures are typically difficult to determine because theyare poorly imaged on seismic reflection data and rarelyexposed in field outcrops. Only a few studies haverevealed detailed data of the internal structures frommine excavations. In a North German salt diapir, thereare plans to expand one of these mines. For this pur-pose, detailed geological information of the saltstructure is necessary. Because saline solutions haveflooded two neighboring mines, special care needs tobe taken when deciding where the new mine openingscan be constructed.

In this study we use borehole data and drill coresplus ground penetrating radar (GPR) for site investiga-tion. Detailed core description, microscopic andmineralogical-geochemical analyses allow a reliablelithostratigraphic classification of the Permian (Zech-stein) evaporites penetrated. Structural analysis of welllogs and GPR data document the spatial arrangementof the strata. The multidisciplinary evaluation of differ-ent data sets lead to an improved understanding of the

evaporite composition and structure. The degree ofmatching of all exploration data in a new high resolu-tion 3D model as well as an integrated analysis allowsan estimate of the plausibility of the interpretation. Fur-thermore, the model can be used to assess the saltstructure as a whole as well as to plan future explora-tion work and new mine excavations.

Based on the new data, an updated interpretationdeviates considerably from the prior geological modelof the salt structure in the investigated area. The oldmodel predicted relatively pure halite in a large scaleanticline. However, complexly folded younger unitscontaining a number of 1-2.5 meters thick anhydriteswere discovered. This study highlights that structuralstyles can vary abruptly along strike in a salt diapir.The identified structures indicate the kinematics of amultiphase salt rise. We show that regional compres-sion and inversion tectonics played a key role in thediapir growth. They also affected the salt structureouter shape and lead to complexly folded as well aspartly overturned Zechstein strata.


Salt Tectonics and Hydrocarbon Accumulations Trapped on Diapir Flanks in the Lusitanian Basin, Portugal

Ian DavisonEarthmoves Ltd.38-42 Upper Park RoadCamberley, Surrey GU15 2EFemail: [email protected]

Pedro BarretoPartex Oil and GasRua Ivone Silva, 6 – 1o1050-124 Lisbon, Portugal

Abstract

Salt movement in the Lusitanian basin has sig-nificantly affected sedimentation in the onshore portionof the basin. We show that salt diapirism initiated soonafter deposition of the salt in the Hettangian and thatdiapirism was active throughout the Jurassic and Creta-ceous periods. Strong Alpine-age inversion producedsqueezing of the diapirs and folding and faulting in theoverburden around the salt structures. Large upturnedflanks of overburden sediments were produced andconstitute good potential traps for hydrocarbon accu-mulations. We describe two upturned diapir flankswhich are superbly exposed on coastal cliffs. Both theSão Pedro de Moel and Santa Cruz structures containtar-saturated reservoirs, trapped against salt diapir

walls. We interpret these to be exhumed but now bio-degraded, oil accumulations. The São Pedro de Moelstructure is estimated to contain >85 million barrels oftar and demonstrates that there is a commercially via-ble hydrocarbon system in the basin, although most ofthe traps onshore have been breached during inversion.This has positive implications for the deeper offshoreLusitanian and Peniche basins, as well as the conjugateCarson-Bonnition basin in Newfoundland. To ourknowledge these are the only documented examples ofexposed hydrocarbon accumulations trapped againstsalt diapir flanks and could represent the first bygoneoil accumulations described in the Lusitanian basin.


Salt Tectonics Outcrops and 3D Drone Images from the Sivas Basin (Turkey) Compared to High-Resolution Seismic Lines in the GOM and B32 Angola

Jean-Claude RingenbachCharlie KergaravatCharlotte RibesTOTAL saStructural Geology GroupAv. Larribau, 64018 Pau cedex, Franceemail: [email protected]

Alexandre PichatEtienne LegeayJean-Paul CallotLFC-R, Université de Pau et des Pays de l’AdourStructural Geology GroupAvenue de l’Université, BP 576, 64012 Pau cedex,

France

Abstract

The outstanding outcrops of salt tectonic struc-tures of the Sivas basin in Anatolia are now well-known. A drone acquisition in November 2018 pro-vides 3D images to visualize and interpret thestructures in order to better analyze subsurface datafrom salt domains. Drone images, now widely used instructural geology, allow building 3D qualitative mod-els of the outcrops. Seven structures among the mostdemonstrative of salt tectonics have thus been imagedin secondary minibasins.

The Sivas basin, an elongated Oligo-Miocenenorth-verging multi-phased foreland basin, developedabove the Neotethys suture zone. Evaporites depositedat the end of the early compression phase (Bartonian),filled the foreland basin and covered eroded thrustsheets and folds to the south. Primary minibasinsformed during a period of quiescence from LateEocene to Early Oligocene, associated to the buildingof an evaporite canopy. The system further evolvedduring convergence of the Arabian and Eurasian platesin the Late Oligocene-Early Miocene with a renewedcompression on the north verging fold-and-thrust belt

(FTB). This resulted in the formation of secondaryminibasins, ultimately tilted and welded.

In the last decades, huge improvements in seis-mic imaging under thick allochthonous salt have beenmade in the Gulf of Mexico and Angola. Wide-azimuthtowed-streamer (WATS) 2D as well as 3D seismicacquisitions allow far better imaging along steep sub-salt diapiric flanks and welds. However, major drillingdisappointments still do occur, due to unseen mega-flaps and small-scale structures such as halokineticsequences at various scales or small faults cannot beseen. Field analogs then become the only guide for abetter assessment of the traps.

Striking geometric analogies between the Sivasoutcrops and seismic images from the classic petro-leum provinces controlled by salt tectonics willillustrate the extraordinary quality of the Sivas basin asa geometrical field analog for the Angola and the Gulfof Mexico salt basins. Analog modelling imaged withX-ray tomography under a medical scanner will also beused for comparison (Callot et al., 2016).


Salt Tectonics Restoration in Basin and Petroleum System Modeling: Contribution of Physical Analogue Models and Methodologies

Sylvie SchuellerIFP Energies nouvelles 1&4 avenue de Bois-Préau 92500 Rueil-Malmaison, France email: [email protected] Marie Callies BEICIP FRANLAB 232 avenue Napoléon Bonaparte 92500 Rueil-Malmaison, France Jean-Marie Mengus IFP Energies nouvelles 1&4 avenue de Bois-Préau 92500 Rueil-Malmaison, France

Nadine Ellouz-Zimmermann IFP Energies nouvelles 1&4 avenue de Bois-Préau 92500 Rueil-Malmaison, France Jean-Luc Rudkiewicz IFP Energies nouvelles 1&4 avenue de Bois-Préau 92500 Rueil-Malmaison, France

Abstract

Being able to reproduce the tectonostratigraphicevolution of a basin is crucial to accurately reproducethe structural, thermal, pressure history of the basin,and its associated petroleum system(s). When saltmovement is involved, the structural reconstructionbecomes even more challenging. The objective of thispaper is to show how physical analog modeling canhelp to understand the structural complexity observedin salt tectonics. When correctly scaled, analog sand/silicon models add some constraints to the chronologyof deformation necessary for a convincing restorationscenario. Two methods of backward salt sequential res-toration, the classical pure vertical shear backstripping

and more recently developed structural restorationaccounting explicitly for lateral movements alongfaults, have been tested. Results are presented on 2Dand 3D basin model examples. Though much progresshas been made, sequential salt restoration still remainschallenging. On one hand, efforts are concentrating toset up fully automatic approaches. On the other hand,developments are performed to produce more flexibleand adaptable meshing technologies that will lead tomore realistic geometric evolutions through time, aswell as more accurate estimations of fluid flow andmechanical stresses.


Loading Complex Salt Isopachs: Progradation Across Segmented Salt-Filled Rift Systems

Tim P. DooleyBureau of Economic GeologyJackson School of GeosciencesThe University of Texas at AustinUniversity Station, Box X Austin, Texas 78713-8924, USAemail: [email protected]

Michael R. Hudec Bureau of Economic GeologyJackson School of GeosciencesThe University of Texas at AustinUniversity Station, Box XAustin, Texas 78713-8924, USA

Abstract

Deposition of salt during, or immediately after,crustal extension adds to the complexity of post-depo-sition salt tectonics in many ways. For example, saltmay be thin or absent across intra-rift highs, thusimpacting mobility and connectivityand influencingdeformation styles during subsequent sediment load-ing. We use physical models to investigate salt-tectonicprocesses in sediment-driven remobilization of a com-plex salt isopach within a segmented rift system. Astretching rubber sheet generated regional extension(Fig, 1). Slabs of weak silicone embedded at the baseof the pre-rift stratigraphy localized extension to pro-duce a series of soft-linked discrete graben (Fig. 1).Model salt filled the deep graben, thinning across link-age zones. The horst blocks between grabens wereeither covered with a thin salt fringe producing a com-plex, but connected, salt isopach (Model 1; Fig. 2), orsalt was entirely absent above these highs producing ahighly complex and segmented salt isopach (Models 2and 3; Fig. 5). The salt basin was tilted and loaded by aseries of sedimentary wedges. Distal aggradation grad-ually buttressed the prograding system and thickenedand strengthened the suprasalt roof.

Although impacted by the structural relief at basesalt, mobility was aided in models where a continuoussalt fringe covered the entire basin, resulting in exten-sion and translation of the sedimentary overburden(Model 1, Figs. 2-5). Large salt walls formed downdipof the toe of the sedimentary wedge as seaward-flow-ing salt was buttressed against the edges of deep graben(Figs. 3a-c). Continued thickening of these salt-coreduplifts eventually allowed them to collapse and trans-late seawards under extension (Fig. 3d). Sedimentaryloading of these extending, flat-topped diapirs formed

local minibasins that translated seawards until theywelded atop subsalt strata, freezing the adjacent diapirsin place (Fig. 4b). Diapirs were also deformed as theypassed through extensional and contractional hingesassociated with topographic monoclines developedabove the horst and graben topography in subsalt strata(Fig. 4b).

In models where salt was absent across structuralhighs (Models 2 and 3, Fig. 5), major intra-basinal highblocks formed significant barriers to lateral salt mobil-ity, trapping significant volumes of salt in the graben,especially where the salt was depositionally thin and/orthe suprasalt roof was thickened by aggradation andresisted breaching (Fig. 6). These horst blocks are alsocommonly sites of diapirism, where the salt budget issufficient, as salt displaced by the sedimentary load isagain contractionally thickened against these flow bar-riers (Fig. 7). Minor or narrow horst blocks are less of abarrier to seaward salt displacement, allowing saltexpulsion from one graben to another, and verticalstacking of salt bodies and canopy formation where thesalt budget is high (Fig. 8). Stepped counter-regionalsystems dominate in these segmented salt basins withlimited extension seen at the autochthonous level,although roho extension is seen above some canopiesprior to welding (Fig. 8). In both suites of models, por-tions of the rift zone having more subdued structuralrelief (e.g., transfer zones accommodation zones), andthus better salt connectivity, help facilitate seaward saltexpulsion (Figs. 4a and 9).

Despite the inherent oversimplifications in ourphysical models, some good first-order similarities aredemonstrated between our results and seismic-basedexamples from the Scotian margin (Figs. 10 and 11).


Geomechanical Modeling of Diapirism in Extensional Settings: Controls on Styles of Diapir Rise and Fall

Maria A. NikolinakouBureau of Economic Geology, Jackson School of

Geosciences, The University of Texas at Austin10100 Burnet Rd., Building 130Austin, Texas 78723email: [email protected] Heidari Michael R. HudecBureau of Economic Geology, Jackson School of

Geosciences, The University of Texas at Austin10100 Burnet Rd., Building 130Austin, Texas 78723

Peter B. FlemingsDepartment of Geological Sciences and Institute for

Geophysics,Jackson School of Geosciences, The University of

Texas at Austin 10100 Burnet Rd., Building ROCAustin, Texas 78723

Abstract

We develop large strain, transient evolutionarygeomechanical models of salt extensional systems tostudy possible controls on styles of diapir rise and fall.We examine extension rates of 1 and 2 km/m.y., base-level rise rates of 1km/5m.y. and 1km/3m.y. and base-ment slopes of 0°, 1°, and 2°. We find that highsedimentation rates and low extension rates promoteefficient sweep of salt from the source layer into thediapir(s). This favors the development of a single struc-ture and leads to taller diapirs that eventually developsharp corners. We show that growing diapirs load wallrocks laterally and increase their horizontal stressdespite the imposed regional extension. In contrast,basement slope and increasing extension rates lead toinefficient salt sweep. We show that this inefficient

sweep results in partitioning of the extensional strainacross the basin and development of multiple diapirswith extensional turtle structures between them. Hori-zontal stresses remain low across the basin. We alsostudy possible styles during diapir collapse. We showthat the presence of sharp corners (bulb shape) in a dia-pir favors synclinal collapse. This is because thecorners in a bulb-shaped diapir act as stress concentra-tion points and cause weak fault zones to radiateupwards and isolate the roof above the falling diapir.Horizontal stress in the roof sediments between thefaults increases and differential stress decreases. Wecompare our geomechanical observations with similarkinematic features found in the field, as well as withfeatures found in physical models.


Structural Configuration and Evolution of Subsalt Hydrocarbon Traps Adjacent to Salt Walls, Green Canyon, Gulf of Mexico

Van S. Mountemail: [email protected] J. WilkinsBrian LindseyTodd ButaudPeter Gamwell

Todd FowlerCarlos MorrisHaryanto AdigunaByron McDonaldAnadarko Petroleum CorporationP.O. Box 1330Houston, Texas 77251

Abstract

Seismic and well data are used to constrain thegeometry and evolution of an oil field located adjacentto a salt wall in the Green Canyon protraction area,northern Gulf of Mexico. Full and wide azimuth 3Dseismic data image the configuration of the salt-sedi-ment interface (SSI) and structure of the field: a three-way trap developed along a salt wall/weld system. Datafrom wells drilled to appraise and develop the field areused in conjunction with the seismic data to constrainthe structural interpretation and trap geometry. Welldata utilized in the study include: biostratigraphic agecontrol, wireline based sand and marker correlationsbetween wells (with supporting information fromdetailed geochemical analysis), and bedding orienta-tions from core and logs (resistivity and oil-basedimage logs). Wells are drilled in water depths ofapproximately 1.5-1.8 km (5,000-6,000 ft) targeting a

subsalt reservoir in Miocene turbidite sandstones.Wells penetrate a salt canopy up to 5 km (3 mi) thickoverlying the objective section. The field occurs in adipping halokinetic sequence (dip magnitudes rangefrom ~20° to overturned). The interpretation indicatesthat the reservoir sand interval pinches out before inter-secting the SSI. Two general populations of sub-seismic scale structures (deformation bands and smalloffset faults) are observed in core and image logs fromwells adjacent to the salt weld: one population in whichdeformation bands and faults trend approximately par-allel to the strike of the SSI; and one in which thesefeatures trend at a high angle to the SSI. The populationthat trends at a high angle to the SSI occurs in thevicinity of a change in megaflap geometry and achange in trend of the SSI.


mailto:

Sub-Seismic Deformation in Traps Adjacent to Salt Stocks/Walls: Observations from Green Canyon, Gulf of Mexico

Scott WilkinsVan MountTodd ButaudBrian LindseyHaryanto AdigunaJonathon SyrekChelsea FennInga Matthews Anadarko Petroleum Co. 1201 Lake Robbins Drive The Woodlands, Texas 77380 email: [email protected]@sbcglobal.net

Russell Davies Schlumberger 3011 Internet Blvd., Suite 200Frisco, Texas 75034

Abstract

Well data are used to constrain the sub-seismicdeformation of two oil fields trapped against a salt wallin the Green Canyon protraction area, northern Gulf ofMexico. Two general populations of sub-seismic scalestructures (deformation bands and small offset faults)are observed in core and image logs. One population ofdeformation bands and faults trend approximately par-

allel to the strike of the salt-sediment interface (SSI)and are observed where the SSI is relatively linear. Asecond population of features that trend at a high angleto the SSI occur in the vicinity of a change in flapgeometry and associated change in trend of the SSI.This later population is more important for reservoircompartmentalization and flow baffling.


Can Deep Mantle Processes Influence Regional Salt Tectonics?

Gillian Appsemail: [email protected] Tim DooleyBureau of Economic GeologyThe University of Texas at Austin

Alex Bump BP ExplorationLondon, UK

Abstract

Mantle processes produce uplift (over mantleupwelling) and downwarp (over downwelling) that areof more or less equal vertical and spatial magnitude.Mantle uplifts have been recognized in both the presentday and geological past because they have an obviouseffect recorded by erosion and fluvial incision patterns.Modern downwarped regions can be identified byanomalous bathymetry, but identification in the geolog-ical past is difficult.

Previous studies have considered the effect ofmantle uplift on fluvial processes and sediment bud-gets, but the effects of downwarping have receivedlittle attention, and the potential impact of an upwarp-downwarp pair on salt tectonic processes has not beenpreviously described.

Vertical offset of the ground surface is 1-2km.Vertical movement is magnified by the effects of ero-sion/deposition, and it may exceed 5km. Verticalmovement occurs over a 1-10 m.y. time frame; mostrapid uplift is at the million-year scale. Affectedregions are broadly circular, on a 500-1,000 km scale.Associated tilting ranges from 0.1 to 0.5 degrees. Thismight appear to be an insignificant influence on salttectonics, but there are several reasons why regionaltilting may be important. We consider a margin inwhich the basin is downwarped and the hinterland isuplifted.

Direct effect: Although the gradient change isslight, because it is sustained over a whole slope it maytrigger changes of behaviour. A passive-margin cou-lomb wedge at the point of failure may be pushed intooverall internal failure. Minor tilting of gravity-glidingsystems having near-horizontal basal surfaces greatlyincreases the energy released by gliding, potentiallyresulting in increased slip rates.

Indirect effect: The indirect effect is felt throughthe migration of facies belts at the shoreline and major

redistribution of sediment. Net sediment flux increasesbecause uplift of the hinterland causes increased ero-sion and sediment supply; fluvial systems areextremely sensitive to gradient, so tilting is likely toresult in stripping of older continental sediments andrapid transport of the erosion products to the shelf edgeand slope. Regional tilting can trigger mass failure ofthe upper slope/shelf margin resulting in shelf-marginbreak up and the release of large volumes of sedimentdownslope. Turbidite depositional systems are acutelysensitive to changes in slope: sustained 0.5 degree tiltmay change an entire slope from net deposition to netbypass. The overall effect is likely to be a majorincrease in sediment supply to the lower continentalslope and rise, fundamentally changing the sedimentload on subsurface salt.

Case studies: we suggest that Palaeocene andMiocene mantle uplift of the western US and down-warp of the U.S. GoM resulted in simultaneous anddrastic change in deposition (onset of Wilcox clastics)and change in salt tectonic style (e.g., renewed motionof the deep salt nappe, and development of Paleoceneand Miocene frontal fold belts). In Angola, mantledriven uplift of the Bié-Huila dome is coincident with amajor late episode of slope-scale basinward slip and asignificant increase in clastic sediment flux to the deepwater. We suggest that these are a direct consequenceof the regional low-angle tilting.

We also discuss the implications for sedimentflux to the shelf margin and the resulting deep-waterprocesses in the Gulf of Mexico of a paired system ofmantle-driven upwarp and downwarp that was activeduring the Paleogene and Miocene. We propose thereis a characteristic stratigraphic signature of the deepmantle processes discussed here.


Mass-Transport Complexes (MTCs) Steered by Minibasin Obstruction and Extensional Breakaway on a Salt-Detached Slope: An Example from Above the Sigsbee Canopy

Naiara FernandezOliver DuffyFrank PeelMichael HudecGillian AppsBureau of Economic GeologyJackson School of GeosciencesThe University of Texas at AustinUniversity Station, Box X Austin, Texas, 78713-8924email: [email protected]

Christopher JacksonBasins Research Group (BRG)Department of Earth Science & EngineeringImperial CollegePrince Consort Road London, United Kingdom, SW7 2BP

Abstract

In salt-detached slopes, minibasins translatedownslope as they subside into salt. If the base of salthas high relief, minibasins may weld and stop translat-ing downslope. An unwelded minibasin can pull awayfrom an obstructed minibasin located farther updip,forming an extensional breakaway zone. How this pro-cess can affect seafloor topography is still unknown. Inthis study, we examine how extensional breakawayzones associated with minibasin obstruction can mod-ify seafloor relief and therefore affect the routing ofslope depositional systems.

Using a 3D seismic data set, we investigate therouting of a mass-transport complex (MTC) through acluster of supra-canopy minibasins in the mid-to-lowerslope and onto the continental rise. The MTC is ini-tially transported slope-parallel before reaching theminibasin at the slope toe. At a later stage, growth of anextensional fault system causes formation of an intra-slope topographic barrier and deflection of the MTCinto an adjacent minibasin.

Kinematic analysis of the fault system and seis-mic-stratigraphic relationships show that: (i) the

extensional fault system formed in response to basalwelding of an updip minibasin; (ii) minibasin weldingpre-dates the MTC deflection; (iii) welding-relatedextensional fault system was initiated farther downdipaway from the MTC path and propagated along-striketowards the MTC path; (iv) when the extensional faultsystem reached the MTC path, salt-buoyancy assisteduplift of footwall block occurred and formed a topo-graphic barrier that deflected the MTC; and (v)deformation within the extensional fault system wasaccommodated as differential translation of the saltcanopy onto the continental rise.

Our findings highlight the complex geometryand kinematics of extensional breakaway zones associ-ated with minibasin obstruction and the role thatnormal fault growth and along-strike propagation hason MTC dispersal. Our study illustrates how salt-tec-tonic processes related to minibasin obstruction canmodify slope topography and control deepwater sedi-ment dispersal.


Interaction of Tectonics, Salt, and Sediments in the Gulf of Mexico: An Approach Using Image Processing of Seismic Data

Andreas W. LaakeWesternGecoHouston, Texas 77042email: [email protected]

Abstract

The interaction of salt tectonics and salt move-ment as well as their combined interaction withsedimentation has implications on the formation of res-ervoir distribution and formation of traps in the Gulf ofMexico. I have used the approach of image processingof seismic data that loads triplets of adjacent depthslices from the seismic data cube into red-blue (RGB)images and processes these RGB images with imageprocessing techniques. The method generates colorimages of impedance contrast correlation at single seis-mic sample resolution. Using this method, I havecreated color image cubes for seismic data from theSigsbee Escarpment. They reveal geological phenom-ena having a similar clarity to that of satellite images.These example images allow us to study the interactionof tectonics and salt migration, which in turn, jointlyinteract with sedimentation that has implications on theformation of reservoirs and traps in the Gulf of Mexico.

I have studied the interaction of tectonics withsalt where the salt has moved close to the sea floor.Shear faulting breaks up the protective caprock thusexposing the halite to dissolution by the undersaturatedsea water. The caprock collapses where shearing faultsenter the evaporite body leaving characteristic saltkarst dolines. In relatively deeper strata, the faults

crack the caprock, which has resulted in the depositionof the caprock boulders on the ancient sea floor andmay represent a potential drilling hazard.

The interaction of the salt with sedimentation hasbeen studied on seismic data as well. Local salt move-ment tilts the seafloor, thus destabilizing theunconsolidated seafloor sediments. The high verticalresolution of 5 to 10 m of the image-processed seismicdata reveals different stages of sea floor instabilitiesfrom slides to fully developed mass transport systems.Such processes have also been delineated in deeper for-mations in the same data cube and may be used toreconstruct the ancient tectonic stress.

Finally, the interaction of regional tectonics withflow features within the mass transport systems hasbeen studied. Incised sections of mass transport com-plexes are correlated in locations where shear faultsaffect salt flow. Large gravity slides of contiguous sec-tion of the unstable seafloor occur along regionalfaults.

The movement of salt can destabilize unconsoli-dated sediments at the seafloor resulting inredistribution of porous clastic sediments in turbiditechannels. The tectonic overprint of these channels cancreate traps for hydrocarbons.


The Sakarn Series: A Proposed New Middle Jurassic Stratigraphic Interval from the Offshore Eastern Gulf of Mexico

Thierry Rivesemail: [email protected] Ramiro Pierinemail: [email protected] E&P Americas LLC1201 Louisiana Suite 1800Houston, Texas 77002, USAAndrew J. PulhamEarth Science Associates C&T Inc.5312 Gallatin PlaceBoulder, Colorado 80303, USAemail: [email protected]

Jean-Francois Salelemail: [email protected] Wuemail: [email protected] Duarteemail: [email protected] Magnieremail: [email protected] E&P Americas LLC1201 Louisiana Suite 1800Houston, Texas 77002, USA

Abstract

The quasi-conformable succession of Middle toearly Upper Jurassic (Callovian to Oxfordian) withinthe onshore Gulf of Mexico Basin has classically beendescribed as follows: the Werner Anhydrite is the basalmember of the Louann Salt and lies above a subcrop ofolder Mesozoic and Paleozoic rocks. The Norphlet For-mation overlies the Pine Hill Anhydrite Member of theLouann Salt and in turn is overlain by the SmackoverFormation. However, analysis of the seismic stratigra-phy in the offshore region of the eastern Gulf ofMexico Basin (EGoM) has revealed the presence of asedimentary succession up to 2,500 meters (~8,000feet) thick above the Louann Salt, laterally adjacent tothe Norphlet Formation, and below the Smackover For-mation. Based on the seismic stratigraphy, this newlyrecognized interval, which the authors refer to as theSakarn series, is considered to be older than the Smack-over Formation and coeval to the Louann Salt.

There are no well penetrations within the Sakarnseries. The Sakarn series is interpreted on 3D seismicvolumes predominantly in the Lloyd Ridge Outer Con-tinental Shelf (OCS) protraction area, southeast of thecurrent offshore Norphlet exploration trend, and isunderlain by either Louann evaporites or welded salt.Deeper stratigraphy below the Sakarn series and/or theLouann Salt is interpreted as a pre-salt rift succession.The mapped area includes the Sakarn domain, which islimited by abrupt lateral termination of the Sakarnseries against major structural features, either normalor transform faults, which were important lineamentsduring the early opening phase of the Gulf of Mexico

Basin in the Middle and Late Jurassic; they limit thepresent day distribution of the Sakarn series.

Regional paleogeographic context of the Sakarnseries places its deposition in low-middle latitudesduring an overall extremely dry climate, indicated byLouann evaporites and the aeolian-fluvial, partiallyevaporitic Norphlet Formation. The seismic characterof the Sakarn series exhibits multiple frequency con-trasts and several high velocity intervals. Anhydrite,carbonates, shales, and siliciclastic sediments are allpossible given observed seismic attributes.

There is no consistent or accepted published bio-stratigraphy for both the Louann Salt and NorphletFormation. The Louann Salt has been classicallyplaced in the Callovian stage of the Middle Jurassic(Salvador, 1987; Mancini et al, 1985; 163.5Ma to166.5Ma; Gradstein et al., 2012), a duration of 2.6 m.y.Biostratigraphic data in onshore and offshore wellsprovide a Middle Oxfordian age for the SmackoverFormation, which constrains the age of the NorphletFormation as no younger than ~161 Ma. The units ofthe Sakarn series are therefore older than 161 Ma, butlack biostratigraphic constraints on absolute age andduration.

The Louann Salt, the Sakarn series, and the Nor-phlet Formation could collectively represent rapiddeposition during the Callovian to Early Oxfordian,perhaps >10,000 feet in a few million years. Alterna-tively, the thick Sakarn series and its seismic layeringindicate a potential significant time period for its depo-sition, implying our current understanding of Middle-


Upper Jurassic stratigraphic evolution of the EGoMmay need to be revisited. Extending the onset ofLouann Salt deposition to the Bathonian (170.3Ma to168.3Ma) or earlier may be considered and is postu-lated to be supported by historical strontium isotopicanalytical data (Pulham et al., 2019)

A revised stratigraphic chart and paleogeo-graphic evolution of the Middle Jurassic is proposed tointegrate the Sakarn series with a tentative and broadage bracket of within the Bathonian to perhaps earliestOxfordian, including the underlying Louann Salt depo-sitional episode and overlying Norphlet Formation; atotal time period of up to 9 m.y.


Salt Canopy Rafts in the Northern Gulf of Mexico: Identifying and Understanding the Significance of Strata Laterally Translated by Allochthonous Salt

Steven HoldawayChevron1500 Louisiana StreetHouston, Texas 77002email: [email protected]

Abstract

Identifying the age of sediment above allochtho-nous salt in the northern Gulf of Mexico can bechallenging. To assist in understanding the sectionabove the salt canopy, a model has been created toidentify and categorize different age successions ofsupra-canopy strata. Salt canopy rafts (rafts) aredefined here as stratal packages above allochthonoussalt that are disconnected from primary minibasins andhave moved a significant lateral distance from wherethey were deposited. Rafts are categorized by the ageof the oldest strata present at their base in contact withallochthonous salt or its welded equivalent, and the dif-ferent ages are related to their depositional origin.Mesozoic rafts have Cretaceous or Late Jurassic strataat the base and generally have been deposited onautochthonous or para-autochthonous salt. Paleogeneand younger rafts are generally deposited on allochtho-nous salt; the basal age relates to the timing of canopyemplacement at their initial location. Minibasins con-taining salt canopy rafts have a different geologichistory than basins containing only in place section.Therefore, recognition of rafted strata is required tounderstand the structural and stratigraphic develop-ment of suprasalt minibasins.

The relative thickness of raft strata is dependentprimarily on the amount of underlying salt inflation ordeflation during deposition. Relatively condensedintervals are deposited during or after underlying saltinflation or contraction and are very common. Rela-tively expanded intervals are deposited during or afterunderlying salt deflation or extension, and normalthickness intervals have been deposited while theunderlying salt was stable. It can be difficult to estab-lish normal thickness in areas of thick autochthonousand allochthonous salt. The most reliable estimates ofnormal or regional thickness are found where salt hasnever been present, such as the abyssal plain beyond

the downslope limits of para-autochthonous andallochthonous salt. Strata deposited above autochtho-nous salt after welding also provide estimates ofnormal thickness, although this requires knowledge ofthe welding history. Strata deposited on the crests ofturtle structures after welding of the underlying salt areusually a good location to estimate normal thickness. Inpractice, normal thickness estimates often containuncertainty; however, going through the process ofestimating normal thickness and considering the impli-cations for where salt is inflating and deflating is auseful exercise that leads to a better understanding ofthe structural history.

In deep-water depositional environments, sedi-mentation generally occurs in all areas, even those thatare topographically high due to underlying salt infla-tion. These topographically high areas typically receivereduced deposition that contains the finer grained frac-tions of the sediments being deposited, including thesides and tails of the turbidites, but often excluding thecoarser grained components that are preferentiallydeposited in the topographic lows. Given enough time,these fine-grained deposits can accumulate to signifi-cant thicknesses up to several thousand feet in areas ofactive depositional systems.

Rafts of all types are most confidently recog-nized using wells plus 3D seismic tied topaleontological data that document repetition of supra-salt canopy strata below the salt canopy. Well logsfrom boreholes with incomplete paleontological datacan be correlated to wells with paleontological data,and rafts that have not been penetrated by boreholescan be identified by correlating seismic character withdrilled examples. In some cases, the complexity ofsuprasalt structural deformation near the base of theminibasin indicates significant lateral movement. Thestrength, character, and polarity of the top of salt can-


opy reflection in sediment flood volumes can also beused to distinguish between Mesozoic or younger sec-tion immediately above the salt.

Because Mesozoic strata contain significantthicknesses of carbonate lithologies that are generallyfaster than younger siliciclastic strata at relatively shal-low burial depths, they also can be identified throughcareful application of tomographic velocity analysisand observations of weak and often uncertain polaritytop of salt reflections. In the Gulf of Mexico, strong topof salt peaks in seismic data indicate the velocity ofsuprasalt strata is significantly slower than salt, whichgenerally corresponds to Paleogene or younger sectionimmediately above the salt. When Mesozoic section ispresent above the salt canopy, the top of salt reflectionis typically a weak reflector of unknown polarity due tothe low velocity contrast. The top of salt reflectionbeneath Mesozoic rafts will be a trough if the intervalvelocity juxtaposed with salt is faster than salt or up toapproximately 10% slower than salt due to the signifi-cant negative density contrast between relatively highdensity carbonates and low density halite. These raftsshow variable thickness of Mesozoic section and vari-able age of the oldest strata above the salt. The entireMesozoic section in rafts is typically condensed, some-times highly condensed, but not always. The detailedage of the strata immediately above the salt canopyranges from Oxfordian to Early Cretaceous; Oxfordianis the oldest documented sediment deposited above thelayered evaporite sequence in the Gulf of Mexico. Thepresence of strata younger than Oxfordian immediatelyabove the salt in Mesozoic rafts is interpreted to be dueto a combination of delayed onlap of sediments due toMesozoic inflation of underlying salt and downslopemovement associated with para-autochthonous canopyemplacement. Mesozoic rafts may also contain raftedPaleogene and younger section.

Paleogene and younger rafts have been depositedon allochthonous salt, the basal age relates to the tim-ing of canopy emplacement at the location of initialdeposition, and the salt sheet or canopy has developedduring Paleogene time. Paleogene rafts are oftenencountered in areas where the local salt canopyformed during the Miocene, documenting significantraft translation from areas of Paleogene canopy locatedupslope. Paleogene rafts also contain rafted Mioceneand younger section. Miocene rafts form on a salt sheetor canopy that initiated in Miocene time or earlieremplaced canopy salt that has been locally unroofedduring Miocene time. Miocene, Paleogene, and Meso-zoic rafts contain younger Pliocene or even Pleistocene

age rafted section if they continued to move laterallywith the salt after the end of the Miocene. Pliocene andPleistocene rafts are also present in some of the rela-tively shallow suprasalt minibasins near the leadingedge of the Sigsbee canopy where salt has continued toinflate and advance after the end of the Miocene.Expanded late Miocene, Pliocene, and Pleistocenesuprasalt section is generally not rafted and is mostoften encountered in deep minibasins upslope of theleading edge of the Sigsbee salt canopy.

Careful application of the salt canopy raft modelcan provide a practical solution to the challenges ofidentifying age successions of supra-canopy sediments,appropriately modeling their geologic history, andaccurately correlating rock properties and drilling haz-ards. The stratigraphic and structural relationshipscaptured in raft strata document their geologic history,providing additional information on the regional geol-ogy of the Gulf of Mexico. Many rafts have portionsthat are nearly parallel bedded and condensed, butother parts of the rafts contain significant changes inthickness; growth strata record the underlying saltinflation and deflation history as well as structuraldeformation through time.

Rafts can rotate, undergo extension or contrac-tion, or move laterally past each other duringtranslation on allochthonous salt. Significant overrid-ing of salt sheets can cause supra-canopy sediment tobecome encapsulated by salt. These encapsulated mini-basins are often composed wholly or in part of rafts.The presence of rafted condensed section overlying thesalt canopy in the bottom of many suprasalt minibasinsshows that the earliest phase of minibasin developmentis often not caused by local thickening of strata abovethe salt but is instead a period of relatively condenseddeposition on salt-cored topographic highs thatoccurred in a different location. These rafts are pro-gressively translated with the canopy salt to theircurrent position where salt deflation eventuallyoccurred, although some thinner rafted minibasins donot show any significant salt deflation in their history.

Creating accurate structural restorations andbasin models in areas with salt canopy rafts requiresspecial attention. Not only is it necessary to properlyidentify the age and thickness of rafted strata, but itmust be treated carefully during restoration and basinmodeling. It is tempting to use the elevations of raftedsections to constrain the regional elevations and thick-nesses of strata where there is no local subsalt controlfor structural restorations, but this leads to significanterrors if the strata have been displaced laterally and


vertically after deposition. Interpreting rafted section asin place leads to erroneously thick overburden abovethe source rocks and reservoirs in past time steps, inac-curately early estimates for hydrocarbon generation,and incorrect effective stress histories for reservoirquality predictions. Application of the salt canopy raft

model leads to more accurate interpretation of the sec-tion above the base of allochthonous salt, which iscritical for proper correlation of hazards from drilledexamples to undrilled minibasins, and the interpretedinterval thicknesses can be combined with regionalwell control to help guide predrill lithology estimates.


Documents

Salt Tectonics, Associated Processes, and