Acta geológica lilloanalillo.org.ar/revis/geo/2009-21-sup/AGN-2009-s-2.pdf · 2015. 10. 29. · 2 Acta geológica lilloana 21 – ISSN 0567-7513 – Suplemento, 9th ICFS, 2009 Acta

Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 1

Acta geológica lilloanaVolumen 21

Fundación Miguel Lillo— 2009 —

— Suplemento —

Abstracts of the9th International Conference on Fluvial Sedimentology

Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 20092

Acta geológica lilloanaSerie publicada por la Fundación Miguel Lillo, que tiene como objetivo divulgar trabajos originalessobre ciencias geológicas y afines. Los trabajos son evaluados por árbitros externos e internos.Correo electrónico: [email protected]

I S S N 0 5 6 7 – 7 5 1 3

© 2009, Fundación Miguel Lillo. Todos los derechos reservados.

Fundación Miguel LilloMiguel Lillo 251(4000) San Miguel de TucumánArgentinaTelefax +54 381 433 0868www.lillo.org.ar

Editora de Acta geológica lilloana: Ana FogliataSecretaria editorial: Lucía IbañezSecretaria del Área Geología: Rosa MolinaEditor gráfico: Gustavo Sánchez

Comité editorial:Dra. Ana S. Fogliata (Coordinadora) (Fundación Miguel Lillo, Facultad de Cs. Naturales, UNT)Dra. Lucía Ibañez (Secretaria) (Fundación Miguel Lillo, Facultad de Cs. Naturales, UNT)Dra. Judith Babot (Prosecretaria) (Fundación Miguel Lillo, Facultad de Cs. Naturales, UNT)Dr. Pablo Grosse (Fundación Miguel Lillo, CONICET)Dr. Hugo A. Carrizo (Fundación Miguel Lillo)Dr. Sergio Georgieff (Facultad de Cs. Naturales, UNT, CONICET)

Editores asociados:Dr. Carlos L. Azcuy (CONICET)Dr. Eduardo Piovano (CONICET, Universidad Nacional de Córdoba)Dr. Franco M. Tortello (CONICET, Universidad Nacional de La Plata)

Publicación indexada en las siguientes bases de datos:Bulletin Signalétique, Biosis Previews, Latindex, Periodica, Referativnyi Zhurnal

Canjes:Centro de Información Geo-Biológico del Noroeste Argentino,Fundación Miguel Lillo, Miguel Lillo 251, (4000) San Miguel de Tucumán, Argentina.Correo electrónico: [email protected]

Ref. bibliográfica: Acta geol. lilloana 21, Suplemento, 2009.

Periodicidad: un volumen anual en dos números.

Impresión: Artes Gráficas Crivelli.Propiedad intelectual Nº 315450.Prohibida su reproducción total o parcial.Impreso en la Argentina.P r i n t e d i n A r g e n t i n a .


24-28 August, 2009San Miguel de Tucumán, Argentina

Organization:Universidad Nacional de Tucumán

Fundación Miguel Lillo

Abstracts of the9th International Conference on Fluvial Sedimentology

ORGANISING COMMITTE

Sergio M. Georgieff— Convenor —

Sebastián Moyano— Secretary —

María Soledad Bustos— Finance —

Gerardo E. Bossi— Scientific Coordinator —

Lucía M. Ibañez— Publication Coordinator —

María Eugenia Vides— Scientific Programme Organizer —

Guillermo F. Aceñolaza— Excursion Coordinator —


9th ICFS is sponsored by

AGENCIA NACIONAL DE PROMOCIÓN CIENTÍFICA Y TÉCNICA

ASOCIACIÓN ARGENTINA DE SEDIMENTOLOGÍA

ASOCIACIÓN PALEONTOLÓGICA ARGENTINA

COLEGIO DE GRADUADOS EN CIENCIAS GEOLÓGICAS DE TUCUMÁN

CONSEJO DELIBERANTE DE SAN MIGUEL DE TUCUMÁN

ENTE CULTURAL TUCUMÁN

ENTE TUCUMÁN TURISMO

FACULTAD DE CIENCIAS NATURALES E INSTITUTO MIGUEL LILLO

FUNDACIÓN MIGUEL LILLO

HONORABLE LEGISLATURA DE TUCUMÁN

INSTITUTO DE ESTRATIGRAFÍA Y GEOLOGÍA SEDIMENTARIA GLOBAL

INSTITUTO NACIONAL DE AGUA DE LA NACIÓN

INTERNATIONAL ASSOCIATION OF SEDIMENTOLOGISTS

MUNICIPALIDAD DE SAN MIGUEL DE TUCUMÁN

SECRETARIA DE CULTURA DE TUCUMÁN

UNIDAD DE NEGOCIOS DE LA UNIVERSIDAD NACIONAL DE TUCUMÁN


This volume contains abstracts presented to the 9th International Con-ference on Fluvial Sedimentology, held at the Universidad Nacional deTucumán in San Miguel de Tucumán, Argentina between 24th and 28th

August, 2009. The 9th ICFS was co-organized between Universidad Na-cional de Tucumán and Fundación Miguel Lillo.

This volume is a Suplemento, Special Publication, of the ActaGeológica Lilloana Journal, Miguel Lillo Foundation.

We should like to thank all those involved in the organization of the9th ICFS:

The abstracts were printed due to the generous support of Miguel LilloFoundation; special thanks to the Honorable Advisor Commission, itsPresident Dr. Jorge L. Rougés, the General Director, Lic. Ana MaríaFrías de Fernández, the Director of Geology, Dr. Ana Lía Ahumada, theformer Director, Dr. Hugo A. Carrizo, and the Chief Editor of ActaGeológica Lilloana, Dr. Ana S. Fogliata.

The volume has been edited by Dr. Lucía M. Ibañez. Special thanks toLic Gustavo Sánchez, who provided the final fit to print this volume.

Mrs. Macarena Cárdenas Ypa realized a hard and tireless work in theorganization of Conference venue, travels and accommodations of KeyNote Lecturers.

Lecturers provided interesting keynotes and agreed to form the AwardCommittee.

Field excursion leaders are thanked for the time and effort they devot-ed to planning, running and preparing the excursions and the fieldguides.

The Agencia Nacional de Promoción Científica y Técnica supportedthe organization and travels of Lecturers.

The International Association of Sedimentologists sponsored travelgrants for students.

The Ente Tucumán Turismo de Tucumán provided hotel accommoda-tions for Lecturers.

The Instituto de Estratigrafía y Geología Sedimentaria Global spon-sored the Conference Venue and others additional supports involved inthe organization.

The Unidad de Negocios of the Universidad Nacional de Tucumánhelped the organizers with the finances; special thanks to its Director, Dr.Andrea Guraiib, Ms. Andrea Cavanna and Mr. Mario Abaca.

The Municipalidad de San Miguel de Tucumán provided posters andpamphlets.

SERGIO M. GEORGIEFFConvenor, 9th ICFS

Preface and Acknowledgements


Pre – Conference Field Excursions

1.- From the Cretaceous rift to the Pliocene Foreland basins (NW Ar-gentina): Tectonic and Sedimentation

Cecilia Del Papa - CONICET.

2.- Evolution of the Fluvial System in The Tertiary Andean ForelandBasin (Precordillera, Argentina)

Carlos O. Limarino. Universidad de Buenos Aires – CONICET.

3.- Fluvial Syntectonic Features in Cenozoic Pampean DepositsGerardo E. Bossi, Sergio M. Georgieff and Sebastián Moyano, Universidad Nacional

de Tucumán – CONICET.

Mid – Conference Field Excursions

4.- Mezoic and Cenozoic Fluvial Deposits of Northern TucumánGerardo E. Bossi and Sebastián Moyano, Universidad Nacional de Tucumán -

CONICET.

5.- San Javier - Raco, Precambrian, Creaceous-NeogeneGuillermo Aceñolaza, INSUGEO - CONICET. Universidad Nacional de Tucumán

6.- Tafí and Amaicha Valleys: Paleoclimatic and PaleoenvironmentalNeogene Evolution

Miriam M. Collantes, Lucía M. Ibañez, and José Busnelli, Universidad Nacional deTucumán – Fundación Miguel Lillo.

Post – Conference Field Excursions

7.- Paraná River, Miocene to PresentOscar Orfeo, CONICET – Universidad Nacional del Nordeste.

8.- Sedimentary Evolution of the Golfo San Jorge Basin, Central Pata-gonia, Argentina

José Paredes, Universidad Nacional de la Patagonia San Juan Bosco.

Field Excursion Leaders

Responsibility for the contents of these abstracts rests upon the authors and not the Miguel Lillo Foundationnor Universidad Nacional de Tucumán. Data presented and conclusions developed by the authors are for infor-mation only and are not intended for use without independent substantiating investigation on the part of thepotential user.

When conference abstracts are cited, this volume should be referred to as: Lucía M. Ibañez (Ed.), Abstracts,9th International Conference on Fluvial Sedimentology. Acta geológica lilloana 21 (2), Suplemento, 2009. SanMiguel de Tucumán.


ON THE INTERACTIONS BETWEENTURBULENT FLOWS, SEDIMENTTRANSPORT AND BEDFORMDEVELOPMENT IN ALLUVIAL CHANNELS:28 YEARS ONJim Best

Departments of Geology and Geography and Ven Te

Chow Hydrosystems Laboratory, University of Illinois,

Urbana, Illinois 61801, USA. [email protected]

Understanding the interactions betweenthe trinity of turbulent flow, mobile sedimentand bedform development lies at the heart ofinterpreting fluvial form and process. This‘trinity’ was used as the basis of the seminalpaper by Leeder (1983) that arose from the2nd ICFS, held in Keele, UK, in 1981. Theseideas were grounded in the exciting develop-ments that were made in turbulent boundarylayer research in the late 1970’s, with thepaper of Jackson (1976) being one of thefirst that attempted to link turbulent bound-ary layer structure with sediment transport,bedform generation and stability. Since theseadvances in our thinking in the 1980’s, thetools that we can use to investigate the com-plex feedbacks in this trinity have improvedbeyond our 1970/80’s dreams! - in laborato-ry technology, field methods and numericaltools. Where has this brought us and whatare the key issues that now face us in quanti-fying, understanding and predicting the mor-phodynamics of alluvial bedforms?

This talk will review some of the key de-velopments in the field of alluvial bedformmorphodynamics over the past 28 years, andshow results from the laboratory (using arange of optical and acoustic techniques),field (highlighting acoustic methods) andcomputational modelling (LES realizations offlow over bedforms). This review will encom-pass the feedbacks between bed morphologyand large-scale vorticity, the interactions be-tween bedforms, the influence of fine-grainedsediment on turbulence modulation within theflow, and some commonalities of bedforms

Keynotes

generated in different sized bed sediment.The talk will conclude with examples of howbedforms are key in understanding some ofthe larger-scale aspects of river channel mor-phodynamics, and highlight some areas ofcurrent research that raise issues concerningbedform development in both laminar andturbulent flows and the scaling of bedformswithin unidirectional flows.

References

Jackson, R.G. (1976) Sedimentological and flu-id-dynamic implications of the turbulentbursting phenomenon in geophysical flows.J. Fluid Mech. 77, 531-560.

Leeder, M.R. (1983) On the interactions be-tween turbulent flow, sediment transportand bedform mechanics in channel izedflows. In: Int. Ass. Sedimentol. Spec. Publ.(Eds. Collinson, J.D. and Lewin, J.), 6, 5-18.

ROLE OF CONTINENTAL MARGIN INCISED-VALLEY SYSTEMS IN THE EMERGINGSOURCE-TO-SINK PARADIGMMike Blum

ExxonMobil Upstream Research Company, Houston,

Texas

The emerging source-to-sink paradigmseeks to develop a holistic understanding ofsediment production, transport, and storagefrom source regions in tectonic hinterlandsto sinks within deep ocean basins. River sys-tems are an important component, the “to”in source-to-sink: this presentation discusseshow the evolution of incised-valley systemsin response to allogenic controls play a fun-damental role in modulating sediment trans-fer across continental margins.

Continental margins incised valleys formin response to sea-level fall, as fluvial sys-tems extend across newly emergent shelves tothe lowstand shoreline and shelf margin.But what is the shelf, anyway? It has longbeen recognized that modern shelf margins


correspond with the depth of sea-level fallduring late Pleistocene lowstands, and nu-merous studies illustrate the important roleof deltaic progradation during lowstands toconstruct the shelf margin. However, a grow-ing body of evidence now suggests thatshelves are fundamentally terrestrial land-scape elements (although they clearly have amarine overprint). The view taken here isthat shelves are essentially the lowstandcoastal plain, river long profiles are gradedto shelf margins, and shelf margins are sim-ply the end of the fluvial sediment dispersalsystem. In this view, the surface across whichrivers extend during sea-level fall is abyproduct of the fluvial system itself, part ofthe equilibrium profile, rather than a surfaceinherited from a different suite of processes.

The evolution of linked coastal-plain andcross-shelf incised-valley systems modulatessource-to-sink sediment routing from ero-sional continental interiors to deepwater en-vironments through the storage and exportof sediments. Incised valleys form in a step-wise manner, with short periods of incisionpunctuated by extended periods of lateralchannel migration and valley widening, andwith contemporaneous deposition of chan-nel-belt sands. Short periods of incision like-ly produce an insignificant amount of sedi-ment export, but periods of lateral channelmigration, valley widening, and channel-belt deposition significantly increase down-stream flux, such that periods of fluvial dep-osition within incised valleys correspond toincreased sediment delivery to the shelf mar-gin and beyond. Moreover, drainage basinscommonly merge as channels extend acrossthe shelf, such that signals of increased ordecreased flux of sediment to the shelf mar-gin and beyond may reflect geomorphic re-sponse to sea-level change —the merging ofdrainages as they transit a broad shelf—rather than changes in sediment supply fromthe hinterland.

High-frequency cyclical isostatic adjust-ments to changes in water and sedimentloads may be intrinsic to the evolution ofincised-valley systems. First, isostatic upliftof the shelf in response to sea-level fall will

enhance incision, whereas sea-level rise andflooding of the shelf will have the oppositeeffect. Second, the development of incisedvalleys results in sediment unloading andloading, which likely produces a cyclicalpattern of isostatic uplift and subsidence aswell. Cyclical uplift and subsidence, eitherdue to hydroisostasy or sediment unloadingand loading, should amplify valley incisionand filling, play a key role in development ofvalley-fill architecture, and play and impor-tant role in sediment export or storage.

UNIT-BAR DEPOSITS IN ANCIENT RIVER-CHANNEL ALLUVIUMJohn Bridge

Department of Geological Sciences, Binghamton Uni-

versity, Binghamton, NY 13902-6000.

Modern river-channel deposits compriseflood-generated sedimentation units, unit-bardeposits, and compound-bar deposits. Al-though all of these scales of deposits are rec-ognized in all modern river-channel depos-its, unit-bar deposits are not commonly re-ported from ancient river-channel deposits.However, unit-bar deposits have been recog-nized explicitly in ancient river-channel de-posits by McCabe, Jones, Bridge et al, andHaszeldine. Ancient unit-bar deposits havealso been misinterpreted by Allen, Roe andHermanson. One of the reasons for the ap-parent lack of unit-bar deposits in ancientalluvium is because they are very similar toflood-generated units. Similarities include:both types of stratasets are dominated bymedium-scale trough cross strata formed bydunes superimposed on bar surfaces;stratasets are decimeters to meters thick;stratasets commonly fine upward from anerosional base; stratasets commonly havestratal discontinuities with overlying andunderlying stratasets. Differences are: unit-bar stratasets are commonly mound-shapedor dip downstream, and; bases of medium-scale trough cross sets are variable in dipand rarely approach the angle of repose,thus giving rare large-scale cross strata asso-ciated with the avalanche face of a unit bar.


Here, ancient unit-bar deposits are recog-nized in re-interpreted ancient alluvium.

SEDIMENTOLOGICAL AND STRATIGRAPHICMODELS: INTEGRATION AMONG SCIENCE,TECHNOLOGY AND OIL INDUSTRY.EXAMPLES IN OIL FIELD OF GOLFO SANJORGE BASIN, CHUBUT AND SANTACRUZ PROVINCES, ARGENTINALuciano Di Benedettto

YPF SA, Av. Libertador 520, Km3, 9000 - Comodoro

Rivadavia, Argentina. [email protected]

At the present, Argentina has five mainoil basins and even some new efforts are con-ducted to explore its marine platform. YPFSA is working in the all basins and has alsorealized exploration in the named frontierbasins.

Since 1907, the Golfo San Jorge Basin(GSJB) is the pioneer oil basin in Argentinaand already has produced 0,3 Mbbl/days and14,713Mm3/days gas. The main productionof oil is coming from Cretaceous fluvial de-posits. The principal characteristic of the oilfield production is a rapid development, forinstance since middle ’90 the drillings werearound 200 wells per year, only by YPF SA.These intensive developments become a dailychallenge to optimization the productionand keep hydrocarbon reserves.

The GSJB was an extensional basin dur-ing Early Jurassic and Middle Cretaceous; itbecame compressive from Late Cretaceousbut mainly during Tertiary. The sedimentarycolumn is formed by fluvial, lacustrine, vol-caniclastics and volcanic deposits. The basinhosts deposits of economic importance inthe sandstone sequences in all of their Creta-ceous lithostratigraphic units.

The studies realized in these deposits arefocused to understand the external and inter-nal controls of the plays. The developmentof quantitative models and the comprehen-sion of tectonosedimentary evolution usingnew technologies and optimizing the avail-able resources (field, lab and research) arethe main goals to improve the prediction ofnew plays.

The sandstone bodies hydrocarbon-bear-ing belong to the Castillo and Bajo BarrealFormations (Chubut Group). These units areformed by fluvial channel belts with thick-nesses from 2m to 10-12m and widths be-tween few tens of meters to 600m. Thechannel belts flowed onto a silt-sandstonefloodplain toward east or southeast as iso-lated fluvial belts. The floodplain depositsare represented by splays and splay-channelswith a high proportion of volcanic ashes andvolcaniclastic deposits like surges and la-hars. Even channel belts show high propor-tion of volcaniclastic and pyroclastic materi-als. Thus, the poro-permeability characteris-tics are very variable into the same sand-stone bodies and the induced fractures arenormal in the primary oil recovery.

The sedimentological and stratigraphicstudies allowed to understand the deposition-al setting of Chubut Group in the The Guad-al Area through the merge of surface andsubsurface data (outcrops, wells, 3D seismic,geochemistry of oils, mudstone composition,petrography, and poro-permeability studies).

AN OVERVIEW OF EROSION ANDSEDIMENTATION PROBLEMS IN FLUVIALSYSTEMS OF NORTHERN ARGENTINAHector Daniel Farias

Instituto de Recursos Hídricos, Universidad Nacional

de Santiago del Estero, Argentina.

The North-West region of Argentinashows a variety of fluvial systems and associ-ated erosion-sedimentation problems. Mostof the large scale watersheds have theirheads along the Andean and Sub-Andeanzones, and they are characterized by a veryheavy sediment yield. On the other hand, thelower reaches of the rivers, mainly locatedon the Grand Chaco plain area, are charac-terized by a wide range of morphologicalprocesses, among others, net sedimentationand channel aggradation.

Several problems related with erosionand sedimentation processes in the studyarea are examined from an engineeringpoint of view.


For instance, the continuous aggradationof the Pilcomayo River, which defines theinternational boundary between Argentinaand Paraguay countries, causes several prob-lems. In fact, channel shifting and avulsionprocesses difficult the river water resourcesmanagement for several uses in both coun-tries and define a challenge to river engi-neers about the location and features of dis-charge diversion works.

Bermejo River also flows from the Andesto Chaco and the sediment yield of its water-shed is among the world highest ones. Thelower reaches of the river show a meander-ing pattern with a remarkable trend to devel-op lateral migration processes, which causesa lot of problems in works located in the riv-er environment, such as water intakes,bridge crossings, agriculture land loss due tobank erosion, etc.

Most of these problems are discussed inthe presentation, along with erosion-sedi-mentation aspects observed in other interest-ing fluvial systems in the region, such as Ju-ramento-Salado and Salí-Dulce.

FATHER OF THE WATERS: UNLOCKING THESECRETSOscar Orfeo,1 Daniel Parsons2

1 CONICET and Universidad Nacional del Nordeste.2 University of Leeds, UK.

The Paraná River System, the “Father ofthe Waters” (in translation from aboriginalGuaraní), is the 6th largest river system inthe world and as such is the most significantin southern South America. The Paraná, aswell posing as a flooding risk for millions ofpeople who live on its floodplain, also pro-vides a water supply, hydro-power, and amajor trade conduit in the region. Despiteits clear economic and social importance wehave a limited understanding of how manycomponents of the system functions and thereis thus a vital need to improve our knowl-edge of channel morphodynamics and im-prove our predictive capacity and thus ensuresustainable development of this immensewatershed.

Large river systems have posed a consid-erable challenge to Science, owing to themagnitude and complexity of factors thatregulate their dynamics. For instance, theParaná has vast volumes of solid and liquiddischarge, a subtropical climate with arange of temporal and spatial variability, adiversity of relief and basin lithology, rapidchanges in the fluvial form, extensive flood-plains, and considerable influence of bothautochthonous and allochthonous tributar-ies. Additionally, many human impartedchanges have already exerted significant in-fluence on the system, including the effect oflarge dams, rectified channels, dredgedchannels, fluvial transit alterations, intensivedevelopment of ports, building of hydroelec-tric plants, the rapid development of cities,and changes in land-use, have or are compli-cating the functioning of the entire system.

The study of modern large fluvial envi-ronments is very much an incipient activity.This paper provides an outline of the re-search conducted by a large multi-nationalgroup of scientists, who have begun to iden-tify some key processes operating within theParaná System. This research for examplehas begun to address questions over mixingrates and flow structure at the Paraná-Para-guay confluence, the influence of bedformson channel scale flow processes and themorphodynamics and sedimentology of largecompound bars. This synthesis will highlightkey findings and point to future researchthat aims to unlock more secrets of thiswonderful fluvial system.

HISTORICAL PLANIMETRIC CHANNELCHANGES IN AN ITALIAN RIVER: THECECINA RIVERLiliana B. Teruggi,1 Massimo Rinaldi2

1 Dipartimento di Ingegneria Civile e Ambientale,

Università degli Studi di Firenze, Via S. Marta, 3

– 50139 Florence, Italy. [email protected] DICeA, Università degli Studi di Firenze.

Fluvial planimetric form is affected bycontinuous changes as a consequence ofchannel adjustments in response to varia-


tions in the balance between sediment supplyand transport capacity. Channel changes maybe caused by geomorphic response to natu-ral changes (e.g. climate) or human distur-bances. Human activities have had a strongimpact on most of the European alluvial riv-ers over the last centuries.

Nowadays, advances in Geographical In-formation System (GIS) technology has sig-nificantly increased the contribution that his-torical data can give to the analysis of chan-nel planform changes.

The aims of this study are twofold: (1) todevelop and apply a systematic methodologyfor measuring and analyzing channel changesby remote sensing and GIS technology; (2) todescribe and interpret in a case study the spa-tial and temporal patterns of channel changeswhich have affected the Cecina River.

The Cecina River is located in southernTuscany (Central Italy). It is a gravel bedriver with large alternating lateral bars, 79km long, and has a drainage area of about900 km² characterized by a Mediterraneanclimate.

A Geographical Information System hasbeen developed, and historical maps andaerial photographs of different scales anddates have been used to identify, measure andanalyze planimetric channel changes.

The active channel was defined and digi-talized from all the aerial photographs. Theriver course was divided into relatively ho-

mogeneous reaches, and a series of basicplanimetric parameters, such as channelwidth, sinuosity and braiding index, havebeen measured. This analysis has made itpossible to measure temporal and spatialchanges in Cecina River channel. In somerepresentative reaches, changes in land-useand forest cover floodplain were analyzedand quantified by comparing aerial photo-graphs using GIS data processing.

Results indicate that all reaches havebeen subjected to progressive channel nar-rowing since 1883. Channel width measuresindicate that the total channel narrowingvaries between 60-80% of the initial width inthe period of time analyzed. This adjustmentis characterized by two phases: the first onestarted at the end of 19th century, the secondand more intensive one began at the end of20th century. The main causes of Cecinachannel changes are associated with man-induced activity such as sediment miningand catchment land use changes (e.g. refor-estation). It is observed that channel narrow-ing is associated with a progressive increasein sinuosity, in some reaches with a changefrom a multithread pattern towards a sinu-ous-meandering configuration. All the mea-surements are used to analyze in detail thespatial and temporal trends in planimetricadjustments and ultimately to derive a con-ceptual evolution model illustrating the spa-tial and temporal trends of adjustments.


LOWER PALEOZOIC FLUVIAL DEPOSITS OFARABIA: FACIES, ENVIRONMENTS ANDDEPOSITIONAL STYLES, SAUDI ARABIAOsman Abdullatif

Earth Sciences Department, KFUPM.

[email protected]

The fluvial deposits in the lower Paleozoicsuccession in Saudi Arabia are dominantlysiliciclastic sediments that are mostly sand-stone dominated with subordinate siltstone ormudstone facies. These lower Paleozoic rocksare exposed locally nonconformably on theArabian Shield basement complex rocks andalso as a long, curve-linear belt around theArabian Shield in central Saudi Arabia. Onand around the Arabian Shield, the main low-er Paleozoic siliciclastic fluvial deposits in-clude the Siq Formation, Yatib Formation,Quweira Formation and Saq sandstone For-mation in the central and northwestern partsand the Wajid Formation in the southwesternpart. The Arabian Shield, which consists ofigneous and metamorphic metasedimentaryand metavolcanic rocks, is the main sedimentdetrital sources. In addition, recycled sedi-ments represent a secondary source. Thesefluvial formations show similarities and dif-ferences in their facies, lithology, texture andcomposition, however, all seem to be charac-terized by sand dominated stream systemwith little or scarce fine sediments. Moreover,the fluvial formations show variations in fa-cies types, architecture and their abundancesand their vertical and lateral stacking pat-terns. Different factors appear to have influ-enced the sedimentation of these formationsin terms of facies and depositional styles oftheir stream systems. These factors includecomplex controls varying from tectonics, sed-iment source/basin relief, climate, weather-ing history and sediment supply. All these fac-tors, in addition to stream autocyclic process-es, have contributed to facies and sequence de-velopment of these formations from theirproximal to distal depositional setting. The

sedimentary depositional heterogeneity ofthese formations has its impacts on theiraquifer and reservoir characteristics.

FLUVIAL DYNAMICS, ALLUVIALARCHITECTURE AND PALAEOHYDROLOGYOF AXIAL AND TRANSVERSE DRAINAGESYSTEMS IN AN EXTENSIONAL SETTING:LOS ADOBES FORMATION (APTIAN),CAÑADÓN ASFALTO BASIN, ARGENTINAJosé Oscar Allard,1 José Matildo Paredes,1 Raúl

Eduardo Giacosa1, 2

1 Dpto. de Geología, Facultad de Ciencias Naturales,

Universidad Nacional de la Patagonia ¨San Juan

Bosco¨, Ruta Provincial Nº 1 S/N Km. 4, (9000)

Comodoro Rivadavia, Chubut Argentina.2 SEGEMAR, Delegación Regional Comahue, CC 228

(8332), General Roca, Río Negro, Argentina.

The recognition of axial and transversedrainage systems in extensional settings re-quires a careful analysis of distribution andscale of fluvial sandstone bodies, palaeocur-rent data and changes in fluvial styles acrossthe depocentre. The variable slope and extentof the channels network can be interpreted byvariations in sediment flow and discharge ofboth systems. The fieldwork is based on theanalysis of 114 fluvial sandbodies of the Bar-das Coloradas Member (Los Adobes Forma-tion) in the Paso de Indios depocenter of theCañadón Asfalto Basin, covering an area of420 km2. Major normal faults of the area areNNW-SSE oriented, and the palaeocurrentanalysis reveals three main regional sedimentflow directions: W-NW (transverse), S-SW(axial) and E-SE (major trunk system). Thesuccession consists of five lithofacies associa-tions (bar deposits, talweg fill deposits,abandoned channel, proximal floodplain anddistal floodplain) and eight architectural ele-ments (channel, gravel bed form, sand bedform, dowstream and lateral accretion mac-roforms, hollow, top bar hollow and overbankfines). Dominance of multi-storey, broad rib-bons (61%) and narrow sheets (38%) reflect

Abstracts


bank resistance and rapid filling. Braidedsandstone bodies (85%), low sinuosity fluvialsandstone bodies (12%) and meanderingchannels (3%) were recognized. Axial sand-stone bodies show a mean thickness (T) of5.9m, the mean true width (W) increasesdownstream from 25m to 109m, and their W/T ratio changes from 14.8 to 42.2 and a me-andering system develops downdip. The meandischarge of the axial system decreasesdowndip from 83 m3/s to 49m3/s, as resultof infiltration and evaporation. The thicknessof transverse systems increases downstreamfrom 3.5m to 6.2m; their mean width (W)range from 40m to 86m. A maximum bank-full discharge (mbd) of 1535m3/s was ob-tained at the downstream point of the conflu-ence zone with a transverse tributary systemthat have a mbd of 1314 m3/s. In a basinwarddirection the axial channel network links to aregional trunk system draining to the E-SE, thelater having a mbd of 4143 m3/s. The pro-posed sedimentary model is characterized bytransverse tributaries that join an axial drain-age system, and a major trunk system basin-ward. The fluvial system records very impor-tant changes in water discharge (short andsharp floods) and migration by avulsionmechanism.

VOLCANIC BEDROCK MORPHOLOGY AS ACONTROL ON FLUVIAL PATTERN IN ASEMI-ARID SETTINGJosé Oscar Allard,1 Alejandro Montes,1, 2

José M. Paredes,1 Gustavo Gabriel Bujalesky2

1 Dpto. de Geología, Facultad de Ciencias Naturales,

Universidad Nacional de la Patagonia ¨San Juan

Bosco¨, Ruta Provincial Nº 1 S/N Km. 4, (9000)

Comodoro Rivadavia, Chubut Argentina.2 Centro Austral de Investigaciones Científicas (CA-

DIC), Housay 200 Ushuaia, Tierra del Fuego.

Downstream changes in the fluvial pat-tern can be imposed by lateral changes inthe nature of the substrate, or bedrockproximity. This study analyzes an ephemer-al, braided channel that cross an upliftedblock of Jurassic basement at Bahía Busta-mante, in the northern margin of the Golfo

San Jorge basin. Ground Penetrating Radarand vertical trenches were carried out in thevalley to characterize the subsurface stratig-raphy. GPR transects allowed us to identifysix radar facies: 1) subhorizontal, 2) lowangle, 3) high angle, 4) concave, 5) convex,6) irregular and discontinuos. Three radarfacies associations were defined: 1) channel,2) channel fill deposits and 3) bar deposits.The three-dimensional organization of radarfacies and superficial features (e.g. braidbars) are consistent with a braided pattern.The width of the river varies from 40 m to260 m, braid bars ranges from 50 m to 77m in width and are 79 m-266 m long.

Specific stream power index (SSP) is de-fined as the Stream Power/Width of thechannel belt. SSP data were obtained in fivepositions along the course of the river. Al-though the river behaves as a braided riveralong their entire course, it shows systemat-ical change in the braiding index and SSP,defining aggradational and degradationalzones along the course. Degradational zonesare characterized by narrow valley widths,they have values of SSP of 0.0156 m2/s and0.00547 m2/s. The largest SSP value is ob-tained where the river crosses the volcanicbasement, which is also the place where thevalley river is narrowest. Aggradationalzones show wider valleys, and have SSP val-ues of 0.00049 m2/s, 0.00315 m2/s and0.000317 m2/s.

The spatial distribution of aggradationaland degradational zones along the course ofthe braided river is interpreted as a responseof the river to the location of the volcanicbasement along the course. Both the braidedpattern and the SSP values evidence the de-velopement of degradational zones where theresisting powerstream power.


ALTERNATING FLUVIAL STYLES WITHINTHE MARITIMES BASIN COMPLEX OFATLANTIC CANADA: A RECORD OFEQUATORIAL CLIMATE CHANGE DURINGTHE LATE PALEOZOIC ICE AGEJonathan P. Allen,1 Christopher R. Fielding,1 Martin

R. Gibling,2 Michael C. Rygel3

[email protected] Department of Geosciences, University of Nebras-

ka-Lincoln, Nebraska, 68588, USA.2 Department of Earth Sciences, Dalhousie University,

Halifax, Nova Scotia B3H 3J5, Canada.3 Department of Geology, SUNY Potsdam, Potsdam,

New York, 13676, USA.

The Maritimes Basin complex of AtlanticCanada preserves a thick stratigraphic suc-cession deposited within a low latitude, pre-dominantly continental setting during theLate Paleozoic. Within the Maritimes Basin,a newly recognized fluvial style has been uti-lized in order to interpret paleoclimaticchanges during the Late Paleozoic. This flu-vial style is characterized by 1) erosionallybased sandstone bodies that display complexand abrupt lateral variations of sandstoneand pedogenic mudstones, 2) an abundanceof sedimentary structures deposited by highflow conditions such as plane bedding andconvex-upward antidune stratification, 3)complex internal stratification produced byplant sediment interactions, and 4) in situarborescent trees preserved within denselyspaced groups that are consistently tilted ina downflow orientation. These characteris-tics have been interpreted to represent fluvialsandbodies deposited under a tropical cli-matic regime characterized by flashy,strongly seasonal discharge.

The recognition of this distinct fluvialstyle has allowed for a refinement of the pa-leoclimatic evolution of the Maritimes Basin.Four discrete stratigraphic intervals havebeen recognized lasting from 3-6 m.y. wherethis fluvial style is prominent, suggestingthat a subhumid, strongly seasonal paleocli-mate was the dominant imprint on these pre-served successions. Fluvial channel bodiescharacteristic of humid conditions dominate

other stratigraphic intervals mainly from theearly to middle Pennsylvanian, while fluvialstyles characteristic of semiarid to arid envi-ronments are dominant in the lowermost anduppermost portion of the studied interval.The recognition of these changes in fluvialstyle from one stratigraphic interval to thenext suggests that systematic changes in pa-leoclimate of at least regional extent are pre-served within the Maritimes Basin. Addition-ally, these intervals broadly coincide withmajor periods of southern hemisphere glaci-ation. Similar periods of fluvial instabilityare recognized within low latitude fluvialsystems within the Cenozoic during periodsof major climatic transitions and the fluvialsuccessions within the Maritimes may recorda similar, although highly time-averaged,response. The recognition of punctuated peri-ods of strongly seasonal paleoclimate repre-sented by the newly described fluvial stylemay aid in refining the paleoclimate evolu-tion of similar successions elsewhere in thepaleotropics.

MULTIPLE VALLEY FILLS FROM THE LATEQUATERNARY RECORD OF THE TUSCANCOASTAL PLAIN (ITALY)Alessandro Amorosi,1 Veronica Rossi,1 Giovanni

Sarti,2 Roberto Mattei,2 Serena Giacomelli2

1 Dipartimento di Scienze della Terra e Geologico-

Ambientali, Università di Bologna, Via Zamboni 67,

40127, Bologna, Italy. [email protected],

[email protected] Dipartimento di Scienze della Terra, Università di

Pisa, Via Santa Maria 53, 56126 Pisa, Italy.

[email protected]

Three consecutive, time-equivalent valleyfills of Lateglacial-Holocene age (13 to 8 calkyr BP) were identified in the Tuscan coastalplain, across a 30 km long transect approx-imately parallel to the present TyrrhenianSea shoreline. From South to North, the Arnovalley fill is 35-40 m thick and 5-7 km wide,the Serchio valley fill is 15-20 m thick and 7-8 km wide, while the Camaiore valley fill is20-30 m thick and 8-10 km wide. The threevalley fills display remarkably similar facies


architecture, with basal fluvial deposits over-lain by a variety of transgressive, mud-dom-inated coastal plain and estuarine deposits.The valley bodies are capped by a sheet-like,late transgressive succession of shorelinesands grading vertically into offshore clays.

Beneath present Arno River, the valleybody consists internally of three superposedmillennial-scale cycles bounded by floodingsurfaces (parasequences). These cycles dis-play a similar facies architecture, withsharp-based central/outer estuarine claysgrading upward into inner-estuary, bay-headdelta and coastal-plain deposits. Overall, thethree parasequences display an aggradation-al, rather than retrogradational stackingpattern, which is interpreted to reflect thecomplex relation between eustatic sea-levelrise and sediment supply during the post-LGM transgression. Diagnostic changes invegetation patterns, driven by opposite cli-mate conditions, enable documentation ofparasequence development as a function ofclimate change. Pollen spectra invariablyshow expansions of broad-leaved forests atparasequence boundaries, suggesting thatrapid shifts to warmer climate conditionsaccompanied episodes of sea-level rise. Incontrast, stillstand phases saw the develop-ment of cold-temperate communities, sug-gesting transition to temporary colder cli-mate conditions.

Stratigraphic architecture beneath theLateglacial-Holocene valley bodies showsthat the coastal system of Tuscany experi-enced multiple cycles of fluvial incision andsubsequent valley filling in response to lateQuaternary sea-level fluctuations. Below theLGM fluvial deposits, an older set of estua-rine clays is observed at depths ranging from40 to 90 m. Based upon physical correla-tions with nearshore deposits, these valleyfills are likely to record an older phase ofgeneralized fluvial incision, which is tenta-tively assigned to the MIS 6-5 transition.

DEVELOPMENT AND EVOLUTION OF ALATE QUATERNARY FLUVIAL CHANNELBELT: IMPLICATIONS FOR THEINTERPRETATION OF ANCIENTANALOGUESAlessandro Amorosi,1 Giovanni Sarti2

1 Dipartimento di Scienze della Terra e Geologico-

Ambientali, Università di Bologna, Via Zamboni 67,

40127, Bologna, Italy. [email protected] Dipartimento di Scienze della Terra, Università di

Pisa, Via Santa Maria 53, 56126 Pisa, Italy.

[email protected]

Defining age of ancient fluvial deposits isgenerally a very difficult task, owing to lackof reliable chronological indicators. In con-trast, Quaternary stratigraphy, due to a wellknown climatic and eustatic history com-bined with radiometric dating, may providea well constrained chronostratigraphicframework.

Detailed stratigraphic analysis of middle-late Quaternary fluvial deposits from the PoRiver Basin, in Northern Italy, reveals dis-tinctive cyclic changes in lithofacies andchannel stacking patterns, falling in the Mi-lankovitch (100 kyr) band . Stratigraphiccorrelations with the coeval nearshore suc-cessions document that the lower portions offluvial cycles, characterized by isolated sandbodies, were deposited during phases of rel-atively high-accommodation (episodes ofsea-level rise under interglacial conditions).In contrast, accumulation of laterally amal-gamated fluvial bodies (channel belts) tookplace during phases of relatively low accom-modation, marking the “regressive” maxima(i.e., OIS 2 and OIS 6). A well constrainedchronostratigraphic framework indicatesthat eight major channel belts (aquifer sys-tems), separated by thick mud-prone flood-plain successions, were deposited during thelast 870 ka, while development of the young-est (LGM) channel-belt took place during aninterval of time of about 20 ka.

Comparison of the late Quaternary suc-cession of the Po Basin with the fluvial ana-logue Escanilla Formation, an Eocene forma-tion commonly applied for reservoir studies,


documents striking analogies in terms ofboth tectonic setting and fluvial architecture.These include: i) sedimentation in a highlysubsiding, actively folded basin; ii) overallthickness of about 800 m; iii) similar cyclicarchitecture (100 m-thick cycles), with de-velopment of 6-8 laterally extensive channelbelts.

Whilst new data are increasingly capableof providing a refined stratigraphic frame-work for the Escanilla Formation, no directdating is available, and duration of its depo-sition (1.5 or 7 Ma?) is still problematic.Based upon similarities with modern channelbelts, we suggest that most of the EscanillaFormation (i.e., the 550 m-thick Olson Mem-ber) is likely to span less than 1 My, andthat the unconformities with both underlyingMondot Member and overlying CollegatsFormation could account for major strati-graphic hiatuses. This interpretation is con-sistent with the remarkable homogeneity interms of both lithology and facies architec-ture observed across the Olson member,along with lack of highly mature palaeosolsthroughout the formation.

FLUVIAL EVOLUTION AND SEQUENCE MAPSOF INTRAMOUNTAIN BRAIDED RIVERS,CATAMARCA PROVINCE, ARGENTINAKarina B. Anis,1, 2 Gustavo E. Rizo,1, 2 Lucía M.

Ibañez,1, 2 Sergio M. Georgieff2, 3

1 Fundación Miguel L i l lo, Miguel L i l lo 205,

T4000JFE, San Miguel de Tucumán, Tucumán,

Argentina.2 IESGLO – UNT, Miguel Lillo 205, T4000JFE – San

Miguel de Tucumán, Argentina.3 Consejo Nacional de Investigaciones Científicas y

Técnicas, CONICET.

The systematic study of sedimentary pro-cesses in the present day rivers allows identi-fying the influence of the individual con-trols, allocyclic and/or autocyclic, in the flu-vial evolution of intramountain braided riv-ers (Moyano et al. 2005, Grignola et al.2006, Georgieff, 2006).

A series of thematic maps were recordedfor the Hualfín and Corral Quemado Rivers

(Catamarca Province, Northwest of Argenti-na). Aerial photographs (from 1969), satel-lite images (from 1996 to 2004) and theodo-lite and gps mappings (from 2006 to 2008)form the database use to compare seasonalriver stages.

Rivers are coming from the boundary be-tween Puna and Pampean Ranges, flow to-wards south along tectonic valleys and joinnear the San Fernando Village. The climateis semi-arid with summer torrential rains,noticeable thermal amplitude and poor veg-etal cover. These characteristics determineimportant changes in dynamics and hydrau-lics of both rivers, e.g.: variations in thechannel belt width (banks erosion), bar mi-grations (lateral and downstream move-ments) and changes in their patterns afterthe confluence zone.

In particular, the Corral Quemado Riveris an ephemeral stream, torrential regime,and the grain size is predominantly sandy(very fine to medium sand, with little contri-bution of gravel and pebbles); whereas theHualfín River is semi–permanent stream andthe grain size is dominantly coarse (pebblesand cobbles).

The maps overlapping define erosion anddeposition areas, changes in the channel beltwidth, bar migrations and results of the manmanagement as intent to avoid floods. 3Dmaps of the study area were performed byusing field measurements, which allow visu-alizing better the morphologic changes.Therefore, some results are: a) the relief andthe climatic variability of the region deter-mine that both rivers and their confluencepresent a high rate of erosion and thereforea continuous internal morphologic variation;b) the greater rate of erosion corresponds tothe Hualfín River and would indicate a lowpotential of preservation of its deposits incomparison to the Corral Quemado River.The preservation rate is even smaller down-stream of the confluence zone.


UPPER CRETACEOUS - SEDIMENTARYPALEOENVIRONMENTS IN THENORTHEASTERN MARGIN OF THENEUQUINA BASIN – THE ANACLETOFORMATION AND THE LOWER MEMBEROF THE ALLEN FORMATION. ARGENTINAPaula Armas,1 María Lidia Sánchez,2 Estefanía

Asurmendi2

1 CONICET - Departamento de Geología, UNRC -

[email protected] Departamento de Geología, UNRC-Ruta 8 Km 603

(5800) Río Cuarto- msá[email protected]

A detailed sedimentary analysis of UpperCretaceous deposits, especially those thatcorrespond to the Anacleto Formation and tothe lower member of the Allen Formation,was carried out in the northeastern marginof the Neuquina Basin (Neuquén and RíoNegro Provinces). The study area is locatedin the boundary sector between the provinc-es of Neuquén and Río Negro and the out-crops are located at the north of the Neu-quén City (Neuquén Province), along theRoute 234 and in the proximity of Cinco Sal-tos (Río Negro Province) on the left marginof the Neuquén River.

The definition of lithofacies and architec-tural elements allowed the interpretation ofsedimentary paleoenvironments and the real-ization of a depositional model.

Using information obtained from the fa-cies association, the following fluvial archi-tectural elements were determined: channel,lateral accretion, downstream accretionmacroforms, crevasse (channel and splaydeposits) and floodplain. Elements influ-enced by tides were also defined: tidally in-fluenced fluvial channel, tidal channels,levee, supratidal flats, intertidal flats, sub-tidal flats and tidal bars. The paleoenviron-mental reconstruction for the Anacleto For-mation consists of a fluvial system withbraided, anastomosing and high sinuositychannels; besides of both upper and middleestuary system. Meanwhile a lower estuarysystem or estuary mouth is characteristic ofthe lower member of the Allen Formation.

Previous works have defined to the Neu-

quén Group as a succession of red layers en-tirely continental formed during a period oftotal disconnection with the Pacific Ocean.This work allows establishing the NeuquénGroup is characterized by typical deposits ofmarine littoral environments. The contactbetween the Neuquén and Malargüe Groupswas interpreted as the beginning of theMaastrichtian Atlantic ingression.

Based on the detailed study and correla-tion of the outcrops at regional scale, thiswork shows that the Anacleto Formation hasthe first evidences of the Atlantic ingression.Thus, the concepts at regional level of theextension and influence of the eustacy duringthe late Cretaceous in the ambit of the Neu-quina Basin are modified. One of the mainaspects that must now be established is theage of the Neuquén Group top or redefiningthe age of the Atlantic ingression.

TECTONIC GEOMORPHOLOGY OFRAMHORMOZ WATERSHED AREA IN THEZAGROS FOLD BELT OF SOUTHWESTERNIRANArash Barjasteh

Head of Geology group, Khuzestan Water & Power

Authority (KWPA), Ahvaz, IRAN.

P.O. Box 61335-137, [email protected]

Ramhormoz watershed is part of the Za-gros Fold Belt in Khuzestan Province ofsouthwestern Iran. It includes three main riv-ers namely Rud Zard, Rud Talkh and A’la riv-ers which combine together to form Ramhor-moz River which in turn joins with JarahiRiver which enters the Persian Gulf south-ward. The geomorphology of the catchmentarea as part of the Zagros Simple Fold Beltis highly influenced by the local and region-al tectonic of the area. Tectonic and structur-al controls on the Ramhormoz watershed arethe main targets of this study due to thebuild of three dams in next future. The tec-tonic setting is characterized by large thrustfaults and the occurrence of several land-slides, which involve deformable and lowcompetent sediments (especially marl, siltand evaporitic deposits). The most rivers are


tranverse-type which can be geomorphologi-cally classified as antecedent drainage. Insome parts, the rivers run parallel to thestrike of anticlines being locally coincidentwith fault traces. The river courses throughthe mountainous part of the studied area aregenerally SE-NW (Zagros trend) whereas theychange to NE-SW or N-S (Arabian trend) inthe plain part. The location of the landslidesis related to the fault junctions. Thrusting ofconformable over more competent ones fa-cilitated sliding in the area. This studyshows the importance to analyze the tectonicgeomorphology in order to improve the fu-ture watershed management projects relatedto geotechniques of the future dam reser-voirs. The results also show that lithologicaldiversity and complexity of the geologicalstructures have key roles on the geomorphol-ogy of the area.

References

Barjasteh, A., 2003. Morphotectonics of AllahRiver and its application in the rehabilitationstudy of Ramhormoz region, southwest ofIran. Proc., 6th. Int Conf. River Engineering,Ahvaz University, Ahvaz, Iran, 6p.

Barjasteh, A., 2006. Investigation of the engi-neering geomorphologic properties of AllahRiver, nor theast of Ramhormoz city ( inPersian). Proc.,10th Symp.Geol.Soc.Iran,Tarbiat Modarres University, Tehran, Iran,p.2368-2373

Barjasteh, A., 2007. Investigation of the rela-tionship of drainage network to fracturesystem in Gachsaran Formation (Ramhormozregion) (in Persian), Proc.,1st Applied Geol-ogy Congress of Iran. Azad Islamic Universityof Mashad, Mashad, Iran, pp.868-872.

HIGH FREQUENCE CICLICITY INCONTINENTAL SYSTEMS: EXAMPLE OFFM. TORDILLO, UPPER JURASSICNEUQUÉN BASIN ARGENTINAArregui Carlos Daniel

J.J. Lastra 6000, Neuquén (8300).

[email protected]

The genesis of the cyclicity in continentalsediments without connection with the seahas been intensively studied in modern

stratigraphy. The existence of upstream allo-genic controls (tectonic and climate – Catu-neanu 2006) and others associated with thedynamics of the own system (autogenic) givea very complex scenario in which is not al-ways easy to recognize the prevalence ofone above the other.

The existence in the continental rockrecord of different frequency cycles with highand low accomodation or humid and dryconditions alternated are very common.

Therefore we can predict that the exter-nal controls (allocyclic) are systematicallypresent in continental deposition.

In the Neuquén basin the fluvial – eolianTordillo Fm. is a very good example of thepresence of different hierarchic cycles wherethe predominance of humid (fluvial – humideolian intervals) or dry conditions (dry eo-lian systems) is of paramount importance inthe reservoir behavior of the rocks and theprediction of hydrocarbon productivity.

The change in the correlation philosophyfrom a lithostratigraphic to a chronostrati-graphic style have produced a very deep im-pact in the comprehension and predictabilityof the local to regional distribution of pro-duction zones in the most important reser-voir interval of the Basin.

References

Catuneanu, O. (2006) Principles of SequenceStratigraphy. Ed. Elsevier.

THE PROCESSES AND DEPOSITIONALARCHITECTURE OF BIG RIVERS: THE RIOPARANÁ, ARGENTINAAshworth, P. J.,1 Amsler, M. L.,2 Best, J. L.,3

Hardy, R. J.,4 Lane, S. N.,4 Nicholas, A. P.,5 Orfeo,

O.,6 Parsons, D. R. ,7 Reesink, A. J. H. ,1, 8

Sambrook Smith, G. H.,8 Sandbach, S. D.,4, 5

Szupiany, R. N.2

1 School of Environment and Technology, University of

Brighton, UK, email: [email protected] Universidad Nacional del Litoral, Facultad de Inge-

niería y Ciencias Hídricas, Centro Internacional de

Estudios de Grandes Ríos, C.C. 217 - (3000)

Santa Fe, Argentina.


3 Departments of Geology and Geography and Ven

Te Chow Hydrosystems Laboratory, University of Illi-

nois, Urbana-Champaign, IL, USA.4 Department of Geography, University of Durham,

Durham, UK.5 Department of Geography, University of Exeter, Exe-

ter, UK.6 Centro de Ecologia Aplicada del Litoral, Consejo

Nacional de Investigaciones Cientificas y Tecnicas,

Corrientes, Argentina7 School of Earth and Environment, University of

Leeds, Leeds, UK.8 School of Geography, Earth and Environmental

Sciences, University of Birmingham, UK.

Little is known about the processes, dy-namics and deposits of the world’s largestmulti-thread rivers and whether they are dif-ferent from smaller (less than 1 km wide)rivers. This paper reports on a combinedfield and numerical modelling campaign onthe sandy Rio Paraná, Argentina – theworld’s 6th largest river.

Bathymetric and 3D flow data were takenin a 38 km long, 4 km wide reach using sin-gle-beam echo sounders, acoustic Dopplercurrent profilers and dGPS. Results demon-strate that the main channels of the Paranáat low flow are dominated by dunes up to3.5 m high and less common unit bars 2-5 mhigh with some up to 10 m high. The depos-its of eight km-scale mid-channel bars werecharacterised by 43 km of Ground 4~Pene-trating Radar (GPR) with penetration downto 10 m, and 28, m-deep suction cores. Theinternal structure of mid-channel bars is dom-inated by (i) decimetre to sub-m high,stacked dune sets, (ii) up to 7 m thick, high-angle, bar margin sets, and (iii) decimetre-thick ripple sets, most commonly, but notexclusively found at the bartop. Re-activa-tion surfaces on bar margins are common.Between 2-7 stacked unit bars make up amid-channel bar.

Numerical modelling of flow, sedimenttransport and morphological change in the38 km study reach show a good match be-tween field and model flow distributions.Simulated channel change is characterisedby talweg shifting and the formation and

migration of low-relief bedforms with di-mensions similar to unit bars observed in thefield (height ~3-5 m, wavelength 1-2 km).Field-model data suggest a need to: (i) un-derstand the contribution of unit bars to bigriver sedimentology, and (ii) establish whythe majority of the Paraná channel-belt isstable over decadal time scales.

FACIES CHARACTERISTICS AND ORIGINOF THE QUATERNARY SEDIMENTS IN THENILE VALLEY, EGYPTAwad, M.H.

Dept. of Geology, Dean Faculty of Science, Al-Azhar

Univ., Cairo, Egypt.

The lithostratigraphic studies of the ex-posed Quaternary sequence at Idfu, Qenaand Beni Suef in the Nile valley of Egypt al-lowed to differentiate it into six rock unitsnamely, Idfu, Armant, Abbassia, Makhadmaand Warsha Formations.

Representative samples were subjectedfor size analysis, heavy mineral separationsand petrographic investigations.

The studied Quaternary sediments reflectaqueous sedimentation processes. The gravelof Idfu Formation are mainly rounded towell rounded reflecting long way run derivedfrom different basement rock types of theEastern Desert mixed with short way runsediments of Nile load origin.

The gravel of Armant, Makhadma andIssawia Formations are angular to subangu-lar indicating short way run derived from thesurrounded and nearby sedimentary sequenc-es. The Warsha gravels which are mainlyangular to subangular and rounded to sub-rounded pebbles and granules of sedimenta-ry and fewly volcanic origin indicate deriva-tion from nearby Eocene and volcanic rocksof the Eastern Desert.

Zircon, epidote, staurolite, kyanite, gar-net, rutile and tourmaline are the mainheavy minerals detected in the sands of Idfuand Armant Formations with varying degreesof abundance.

The combination of sedimentologicalcharacteristics of the studied Quaternary sed-


iments indicate that during the Quaternary(Pleistocene) torrential activities in the East-ern Desert together with Nile flooding led tothe deposition of the studied rock units.

HIGH-FREQUENCY VARIATIONS INACCOMMODATION SPACE IN PUNTA SANANDRÉS ALLOFORMATION (PLIO-PLEISTOCENE), BUENOS AIRES PROVINCE,ARGENTINAElisa Beilinson

Centro de Investigaciones Geológicas – 1 #644, La

Plata (B1900TAC), Argentina.

[email protected]

The continental deposits of the Punta SanAndrés Alloformation (Plio-Pleistocene)crop-out in the marine cliffs of south-easternBuenos Aires Province (Mar del Plata City,Argentina). Deposits of this unit have beenassigned to different sub-environments suchas floodplains, fluvial channels and tempo-rary water bodies according to their faciesassociation and geometry (tabular, wedge-shaped or lenticular). Their lateral and ver-tical arrangement allows to identify threedifferent sections, each of which represents adifferent sedimentary sub-environment anddifferent accommodational conditions.

The first and lower section is character-ized by floodplain deposits (crevasse-splaydeposits and paleosoils). The few channelbodies found in this lower section have asimple geometry, with width/length ratio <10 in all cases and monoepisodic filling.This lower section is considered to representan area distal form the heads, where pale-otopography, fluctuating climate and drain-age design lead to the development of exten-sive floodplains cut by episodic, short-livedstraight or low sinuosity channels associatedto food events or storms. Regarding the pa-leosoils, a cyclic alternation was found be-tween calcic paleosoils and hydromorfic pa-leosoils which was interpreted as cyclicitybetween dry and humid climates. Accommo-dation during this period was positive, buthigh-frequency fluctuations were defined be-tween hydromorphic paleosoils – higher ac-

commodation space- and calcic paleosoils –less accommodation space.

It’s worth saying that channels in thislower section are amalgamated verticallywith channels developed in the upper sec-tions, constituting multistorey channels. Be-cause of this, some areas are dominated bytabular geometries of floodplain depositsand others by channelized geometries whichreflect areas that remained preferentially in-cised during Plio-Pleistocene times.

The middle section is characterized bycoarser floodplain deposits and is muchmore dissected by channels, which have mul-tiepisodic filling and a complex geometry.This section is interpreted as a floodplainproximal to the heads. Paleosoils in this sec-tion are represented by hydromophic hori-zons with little participation of calcic facies.Accommodation during this period is inter-preted to have been positive but reducedwhen compared to the lower section.

The upper section is characterized by de-posits of mobile, high-sinuosity channels.Floodplain deposits are barely representedand highly dissected. Development of fluvialchannels is related to periods of diminishingaccommodation space, probably due to adrop in local base level and/or an increasein precipitations. Filling of the channels in-dicates a subsequent raise in local base leveland re-establishment of positive accommoda-tion space.

To summarize, the geometric and facialanalysis of Punta San Andrés Alloformationdeposits allowed to identify depositional en-vironments which vertical and lateral distri-bution show a progressive change in accom-modation and plaeoclimatic conditions. Dryand arid periods related to little accommo-dation space alternate with wetter periodsrelated to higher accommodation space andfinally to a more important drop in localbase level leading to general fluvial incisionand negative accommodation space.


ON THE INFLUENCE OF DENSITYDIFFERENCES BETWEEN MIXING FLOWSAT RIVER CONFLUENCESBest, J. L.,1 Parsons, D. R.,2 Amsler, M. L.,3

Kostaschuk, R. A.,4 Lane, S.N.,5 Orfeo, O.,6

Szupiany, R.N.,3 Hardy, R.J.5

1 Departments of Geology and Geography and Ven

Te Chow Hydrosystems Laboratory, University of Illi-

nois, Urbana, IL 61820, USA2 University of Leeds, UK; [email protected].

ac.uk3 Universidad Nacional del Litoral, Facultad de Inge-

niería y Ciencias Hídricas, Centro Internacional de

Estudios de Grandes Ríos, C.C. 217 - (3000)

Santa Fe, Argentina.4 University of Guelph.5 Durham University, UK.6 CECOAL, CONICET, Arg.

Channel confluences form key nodeswithin all alluvial networks and extensiveresearch over the past 25 years has shownhow the dynamics of mixing at these sites,and nature of the bed morphology, are con-trolled by the junction angle, the momentumratio between the two confluent flows, thejunction planform shape and the nature ofany bed height discordance between the twochannels. Although remote sensing of manyopen channel confluences, particularly oflarger rivers, often reveals a difference inturbidity between the two flows, there hasbeen little work conducted on how the densi-ty differences that such turbidity contrastsmay generate may influence the dynamics ofmixing at confluences.

This paper presents results from a fieldstudy of flow and bed morphology at theconfluence of the Río Bermejo and Río Para-guay, Argentina, where the sediment load,and thus bulk density, of the Río Bermejoflow is always greater than that of the RíoParaguay. The Río Bermejo is an importantriver in the Paraná basin as, although it mayonly contribute ~5% of the fluid dischargeto the Río Paraná, it may contribute up to~80% of the total wash load. Surveys of theconfluence were undertaken in May 2005and April 2007, when the discharge ratio

between the two rivers (Bermejo: Paraguay)was 0.17 (combined discharge ~ 2800 m3s-1) and 0.23 (combined discharge ~ 5050m3s-1) respectively. However, in 2007 thedensity excess of the Río Bermejo over theRío Paraguay was 5.1 kg m-3, whilst in thestudy period in 2005 it was 2.2 kg m-3. Flu-id mixing at this site is dominated by a den-sity underflow from the Río Bermejo thatpenetrates underneath the fluid of the RíoParaguay and then upwells at the outer bankof the Río Paraguay downstream from theconfluence. Mixing occurs through instabili-ties along the shear layer between the twoflows, fluid instabilities along the top of theunderflow current, topographic forcing overbedforms and interactions with the channelbanks. This paper will illustrate these mech-anisms of mixing and the possible signifi-cance of density contrasts between confluentflows in determining the morphodynamics atsuch channel junctions.

VISUALIZATION OF DUNE AND BAR-GENERATED TURBULENCE AND SEDIMENTSUSPENSION: IMAGES FROM THE SOUTHSASKATCHEWAN RIVER, CANADA, ANDIMPLICATIONS FOR SUSPENDEDSEDIMENT RATING CURVESJim L. Best, R.E. Thomas, P.J. Ashworth, S.N.

Lane, I.A. Lunt, G.H. Sambrook Smith, C.J. Simpson

Departments of Geology and Geography and Ven Te

Chow Hydrosystems Laboratory, University of Illinois,

Urbana, IL 61820, USA.

It has long been known that form rough-ness, such as dunes and bars, can generatelarge-scale turbulence that can dominate thetemporary suspension of sediment withinmany rivers. Several studies have linked suchlarge-scale turbulence to high instantaneoussediment fluxes, and shown how the fluidupwellings produced by form roughnessmay dominate the flow structure of manychannels, especially those with highwidth:depth ratios. Such upwellings arecommonly seen as ‘boils’ on the surface ofmany rivers and range from decimetres tometres in diameter.


This paper presents images of form-roughness generated macroturbulence thatwere recorded from low-level aerial photo-grammetric surveys that were flown over thesand-bedded South Saskatchewan River,Canada. The South Saskatchewan River wasdammed upstream of the study reach in1964 and hence is now relatively clear, en-abling suspended sediment fluxes to be visu-alized within the water column at most stag-es. We will present images, taken at a rangeof flow stages, which show the form of suchupwellings associated with sand dunes andwith the fronts of unit and compound bars.Dunes are seen to provide periodic point-source ejections of sediment that erupt on theflow surface, and are manifested as a trailof circular/ovoid upwellings on the watersurface. Sediment suspension over bar frontsoccurs over a greater width and appears togenerate a more continuous source of par-tially-suspended sediment. The suspendedsediment rating curve for the river nowshows an increase in its slope at 330-403m3s-1, and it is suggested this break corre-sponds to the increased influence of formroughness in generating sediment suspen-sion.

CONTINENTAL SHELVES AS THELOWSTAND FLUVIAL LONGITUDINALPROFILEMike Blum

ExxonMobi l Upstream Research Company.

[email protected]

Lowstand fluvial profiles represent thefirst-order morphodynamic state for conti-nental shelves, and river long profiles arefundamentally graded to shelf margins. Overthe last 10^6 yrs mean sea level has been -60 to 65 m, with a mode at -85 to -90: formost of this time, the majority of shelveswould have been subaerial. Long profiles forriver systems have equilibrium times >10^4to 10^5 yrs: they should be adjusted tomean conditions over time scales that are =equilibrium times, and insensitive to theanomalous and infrequent highstands like

that of the Holocene. On a global scale, it iswell known that channel gradients correlateinversely to drainage basin areas: similarly,shelf gradients and width correlate to on-shore fluvial gradients and drainage areas,such that >50% of the variance in shelfwidth for the midlatitudes and tropics is ex-plained by contributing drainage basin areaalone.

In an icehouse world, high-frequency cli-mate changes are coupled to changes in icevolume, and unsteadiness of sediment supplydue to climate change is modulated by thetransit of river mouths across the shelf.Moreover, transit of river mouths across abroad shelf results in the merger of drainagebasins that, in a highstand world, dischargeseparately to the coastal oceans: merging ofdrainage basins increases individual point-source sediment supply, but there will be few-er river mouths and delta systems at the shelfmargin than there are during highstandtime. These relationships must be different ina Greenhouse world because the high fre-quency, long distance transit of rivermouths, and merger of drainage basinsshould not occur to the same degree. In anIcehouse world, major high-frequency chang-es in fluvial-deltaic, shelf-margin, slope, andbasin-floor stratal packages will reflect fluvi-al responses to sea-level change. By contrast,in a Greenhouse world, high-frequencystratigraphic packaging should be closelycoupled to unsteadiness in sediment supplydue to climate change, rather than modulat-ed by fluvial transit of the shelf, and mergingof drainages.

ROLE OF INCISED-VALLEY SYSTEMS INSOURCE-TO-SINK SEDIMENT ROUTINGAND STORAGE: EXAMPLES FROM THELATE QUATERNARY NORTHERN GULF OFMEXICO MARGINMike Blum, Matt Garvin

ExxonMobil Upstream Research Company.

[email protected]

Incised-valley systems form in responseto sea-level fall, as fluvial systems extend


across newly subaerial shelves to the low-stand shoreline and shelf margin. Recentwork on Late Quaternary systems of the Gulfof Mexico passive margin illustrate how sed-iment supply might change over the courseof a glacio-eustatic cycle, and how the evo-lution of incised-valley systems modulatessource-to-sink sediment routing to deepwaterenvironments.

First, empirical data that links sedimentsupply to climate suggests supply from thehinterlands should decrease during glacio-eustatic sea-level fall and lowstand due totemperature depression. Hence, supply fromthe hinterland may be (a) at a maximumwhen river mouths reside in highstand posi-tions, and sediment storage takes place onthe coastal plain and inner shelf, and (b) ata minimum when river systems are extendedto the shelf margin lowstand shoreline anddirectly feeding the slope and basin floor.

Second, studies of late Quaternary sys-tems, where deposits can be mapped and dat-ed independent of sea-level change, make itclear that incised valleys form in a step-wisemanner in response to sea-level fall and low-stand, with short periods of incision punctuat-ed by extended periods of lateral channel mi-gration, valley widening, and deposition ofchannel-belt sands. Step-wise incision andlateral channel migration is the process thatcreates the basal valley-fill surface, as well ascontrols the overall dimensions of the incisedvalley. The timing of incision and channel-belt deposition on the evolving valley-fill sur-face varies between river systems due to a va-riety of controls. The total volume of sedimentexported during the period of incised-valleyformation is a relatively small value com-pared to the ongoing flux from the hinter-lands, and short periods of incision likely pro-duce an insignificant amount. However, peri-ods of lateral channel migration and valleywidening significantly increase the export ofsediment, perhaps by 25% over backgroundrates, such that periods of fluvial depositionduring sea-level fall and lowstand corre-sponds to increased sediment delivery to theshelf margin.

Finally, for low-gradient continental mar-

gins with broad shelves, like those of theLate Quaternary Gulf of Mexico, drainagebasins merge as channels extend across theshelf, which in turn increases drainage areasthat contribute to single point sources at theshelf margin. Apparent signals of increasedor decreased flux of sediment to the shelfmargin and beyond may reflect geomorphicresponse to sea-level change - the merging ofdrainages as they transit the shelf - ratherthan changes in supply from the hinterland.

LAS CUMBRES FORMATION (EARLYPLEISTOCENE), AN EXAMPLE OF THEOROGENY CLIMAX TECTOFACIES IN THEPAMPEAN RANGESGerardo E. Bossi,1 Sergio M. Georgieff,1, 2 Lucía

M. Ibañez1, 3

1 IESGLO – UNT, Miguel Lillo 205, T4000JFE – San

Miguel de Tucumán, Argentina.2 CONICET.3 Fundación Miguel Lillo, Miguel Lillo 251, T4000JFE

– San Miguel de Tucumán, Tucumán, Argentina.

[email protected]

Las Cumbres Formation is an Early Pleis-tocene coarsening-upward succession com-posed mainly by conglomerates laying overthe Salicas (Pliocene) sandstones. The top ofthe unit is the original geomorphic deposition-al surface. In some places like, in Villa Mer-vil, the unit lays disconformably over the Sal-icas Formation but in others, like in Alpas-inche, the formational limit is a long transi-tion. At the northeast extreme of the VelascoRange, a ring of low hills (named Cumbres deLos Pozuelos) shows to the Las Cumbres For-mation as a complex system of allounits sep-arated by angular unconformities, which arerelated to Uscamayo Fault, an active synsedi-mentary fault in Pleistocen times.

Las Cumbres Formation is one of the typ-ical conglomerate units developed as veryextensive alluvial bahada coming downfrom the emerging ranges during the climaxof the tectonic inversion of the area. Theconglomerates entered deep into the “Bolsonde Pipanaco”, the biggest intramountain ba-sin of the Pampean Ranges. The sedimentary


succession shows an alternation of lenticularbodies of either massive or graded coarseconglomerates and ill-laminated better sort-ed fine conglomerates. The coarser faciesform tabular bodies with occasional over-sized blocks and were interpreted as debrisflows while the better sorted facies were as-signed to water laid deposits related toephemeral channels and chutes forming adistributary system. Texture, angularity andcomposition of the pebbles indicate a com-bined provenance from the Velasco (South),Vinquis and Zapata (North) and Paimán(West) Ranges, according to the measuredpaleocurrents. Paleocurrent and maximumpebble size maps composition indicate dis-placements of the compositional facies fromthe location of their source areas, whichcould be related to the activity of a regionalleft transcurrent fault (known as Lineamien-to Tucumán), and moved the whole sedi-mentary system during the deposition of theconglomerates.

THE RED BEDS OF HUALFÍN FORMATIONIN THE SYNRIFT STAGE OF PAMPEANRANGES, NORTHWEST OF ARGENTINA:PALEOGEOGRAPHIC ANDENVIRONMENTAL IMPLICATIONSGerardo E. Bossi,2 Sebastián Moyano1, 2

[email protected] IESGLO – UNT, Miguel Lillo 205, T4000JFE – San

Miguel de Tucumán, Argentina.2 Consejo Nacional de Investigaciones Científicas y

Técnicas, CONICET.

Hualfín Formation represents the earlyinfill of the Santa María – Hualfín Basin inthe Northwestern Pampean Ranges of Argen-tina. The unit is composed of well indurateddark red sandstones alternating with minorshale’s, laying over the Pampean Peneplain.Facies associations are dominated by massiveto parallel laminated medium to finegrained sandstones forming tabular lateralextensive beds (80%), irregularly cut by len-ticular medium sandstones with trough crossbedding (15%), assumed to be shallowchannel facies and thin tabular fine laminat-

ed shales. Conglomerates are scarce andconcentrated near the base of the succession.Isolated small and rounded pebbles occur inthe channel facies. The clasts are mainlyfrom granite and low grade metamorphicrocks, with minor proportion of volcanicrocks and tuff paraclasts. Associated withthe water laid facies there are also very thickhorizons of crossbedded sandstones, layingover a flat erosive surface. Fine grain falllamination alternates with grain flow thick-er lamina indicates an eolian origin.

Most indirect age evidence located the sed-imentation time in the Paleogene, in a timeprevious to the developping of the near basineastern volcanic arc of the Puna. In the Hua-lfín Range and in the Campo del Arenal, thesedimentation of the unit was controlled by anormal synsedimentary fault system orientedNE-SW, that imposed local variation of thethickness of the unit (between 50 to 200 m).

Dominant facies indicates sheetflood sed-imentation in a very extensive plain near sealevel, under an arid climate with distant andlow relief source areas, strongly oxidizing.Channel deposits are thin lenticular unitscomposed of trough cross - bedding sand-stone with minor indication of channel andbar developpings. The eolian horizons arelocated in the upper part of the unit whenthese sandy units reached the maximum de-velopment The normally ephemeral and dryfluvial system was an excellent repositoryfor the dune fields formed by better sortedsandstones.

Another unit of similar age with exten-sive dune fields interstratified with the samefluvial facies is known as Quebrada de losColorados Formation, outcropping about300 km to the north of the study area, in theCalchaquí Valley. In some places where theunit is absent, as in El Cajón Valley, the sur-face of the Pampean Peneplain is full of im-pact marks generated by wind erosion.

The low land paleogeography of the areaduring Paleogene times associated with theconvergence of the Hadley-Ferrel atmospher-ic cells is a well fitted scenario for the highlyoxidized arid fluvial facies alternating witheolian field.


NATURAL AND ANTHROPICAL FACTORSAFFECTING MODERN RIVERS ANDRESERVOIRS IN A SEMIARID BASIN.TAPIA - TRANCAS BASIN, TUCUMÁN,ARGENTINABustos, María Soledad

Consejo Nacional de Investigaciones Científicas y

Técnicas, CONICET. Fundación Miguel Lillo, Miguel Lillo

205, T4000JFE, San Miguel de Tucumán, Tucumán,

Argentina. [email protected]

Present day rivers are certainly affected byhuman activity and natural factors. In the sameway, the dam construction increases the impacton the modern rivers. Among others anthropi-cal factors, mainly agriculture and deforesta-tion, the amount of runoff and sediment trans-ported to rivers and deposited in reservoirs areincreasing during the last decades.

Celestino Gelsi reservoir is the biggestreservoir in the Tucumán Province, Argenti-na. Since 1966, sediment deposition and lossof impoundment capacity were documentedand referred as consequences of mismanage-ment practices, on agricultural lands and,deforestation in the Tapia – Trancas up-stream area (Adler, 2004).

RUSLE model, (Renard et al., 1997), wasapplied to quantify soil loss for the basinarea. R-factor was calculated, according toRenard and Freimund (1994), two periodswere considered: 1) from 1935 to 1962 and,2) from 1963 to 1990. The values of R fac-tor, obtained were greater in the period1963-1990 than in the period of 1935-1962,probably related to an increase in mean an-nual and monthly rainfall in the source areaduring the second period. Same trend inrainfall amount was reported by Minetti andGonzales (2006) for other areas in NW re-gion of Argentina and Piovano et al. (2002)for central area of Argentina. Also increasedamounts of discharge entering the Reservoirwere registred for the period 1967 to 1996,according to the database from HydrologicResources Department (Dirección de Recur-sos Hidricos of Tucumán).

Satellite images (Landsat 5 TMfrom1988/08/15, 1997/08/24 and 2007/07/

19) were analyzed to detect changes in veg-etative cover, specifically deforestation, andchanges from natural vegetative cover toagricultural lands, for the last 30 years.LandSat images were analyzed to record alsochanges in the delta of Sali River at the res-ervoir.

Expansion of agricultural lands was ob-served mainly in lowland areas along theSali river Valley and in the east region of thebasin (piedmont areas of the Sierras de Me-dina). Changes in river morphology at thedelta, sediment deposits and stabilization ofdeposits with vegetation were observed com-paring Landsat 5 TM for different dates.Changes observed could be related to both,natural and anthropical factors. First,change in base level due to the presence ofthe reservoir and the adaptation of the fluvi-al system to the new base level, also in-creased rainfall amount an its consequentraise in sediment yield. In second place mis-management practices related to land usecould have affected the balance of sedimentleaving the basin area.

PALEOFLUVIAL SYSTEMS IN THEWESTERN CHACO PLAIN, TUCUMÁNPROVINCE, ARGENTINACollantes, M.M.,1 Sayago, J.M.,1, 2 Busnelli, J.1, 2

1 Geosciences and Environment Institute, National

University of Tucumán, Miguel Lillo 205, (4000)

Tucuman (Argentina); [email protected] National Council of Scientific and Technical Resear-

ch (CONICET).

The aims of the work was study de evolu-tion of the western fluvio-eolian plain in theTucumán Province. The analysis of the pale-ofluvial features of the study area, usingphotointerpretation and field observations,allowed mapping and classifying the geo-forms created by past river dynamics. Pale-ochannels with structural control, migratingpaleochannels and paleochannels turned intoravines by human-induced erosion werecharacterized according to their morphologyand/or genesis.

The paleochannels with structural control,


are elongated flat-bottom valleys run down tothe plain as shallow, sometimes buried. Themorphology of the paleoforms suggests thatthey were developed by NW-SE runningstreams with moderate energy and high com-petence. Although they are presently inactive,subsurface or even surface runoff during heavyrain periods might occur. River behaviorseems to be related to paleofluvial conditions,together with fault and fracture control.

The migrating paleochannels are frequentthroughout the fluvio-eolian plain, occurringas shallow channeled depressions generallymasked by crops or artificial drenaige. Suchchannels can be attributed to relatively re-cent overflows from the Tajamar river. Theyserved as local collectors of excess waterduring heavy rain periods, when the regionwas still covered by Chaco forest. Nowadays,they behave as local areas of runoff storageon soils having high capacity for moistureretention that plays an important role duringdrought periods.

The fluvial paleovalleys, are located inthe western sector of the study area, largeelongated depressions, similar to real fluvialvalleys, start in the fluvio-eolian on the westand extend southward over several tens ofkilometers and disappear in the saline de-pressions of Santiago del Estero province.They seem to be related to intensive head-retreat erosion during the moist Holoceneperiods, with runoff increase from the west,and/or to changes in the eastern base levelby neotectonic reactivation. In all cases, ra-vine heads are located in the plain, not inthe piedmont. This could be related to theexistence of an area depressed by tectonicsthat would have diminished river incision,and/or be caused by decrease in water sup-ply from the west due to climatic change. Allthese channels coincide, in some stretch oftheir courses, with structural features caus-ing slightly asymmetric margins. Additional-ly, mass movements might have contributednot only to channel widening but also tochannel stabilization through creeps andflows from the hillsides.

THE RIERA DE SOBIRANS (NE, SPAIN)MODEL OF OVERELEVATED TORRENTIALCHANNELS: SEDIMENTARYCHARACTERISTICSFerran Colombo,1 Oriol Riba,1 Lluis Rivero2

1 Dept. Estratigrafia, Paleontología y Geociencias

Marinas. Fac. Geología. Universidad de Barcelona,

C/ Martí-i-Franquès s/n, E-08028, Barcelona,

España. [email protected] Dept. Geoquímica, Petrología y Prospección Geoló-

gica. Fac. Geología. Universidad de Barcelona, C/

Martí-i-Franquès s/n, E-08028, Barcelona, España.

In the Quaternary of the Maresme thereare a number of natural overelevatedstraight streams of torrent channels locatedat a level higher than the surrounding flood-plains. These overelevated streams show adistinct morphology and a channelized con-vex-up sedimentary body where the verticalaccretion and the levee growth episodes arecoeval. These streams are characterized byepisodic water discharges that are interrupt-ed by prolonged dry periods with no superfi-cial water discharge.

The ”Riera” type stream corresponds to asingle channel of a sandy braided river. It isshort with steep gradient from 3.2% to 3.4%in the Riera d’Arenys (Sobirans). The sourcearea is made up of granitic rocks that supplylarge amounts of sandy sediments. The“Ramblas”, located in the Barcelonès andMaresme areas, are good examples of over-elevated streams.

The term “Sobirans” is proposed for thisnew model.

ESTIMATION OF SUSPENSION SEDIMENTVOLUME IN TO THE FUTURE DAM OFPOTRERO DE LAS TABLAS ON RIO LULES.TUCUMAN PROVINCE. REPUBLICAARGENTINAAnibal Comba, Julian Soto

Faculty of Exact Sciences and Technology. National

University of Tucumán. Independence Avenue 1800.

(4000). San Miguel de Tucumán (0381) 4354502-

155057213. [email protected]


The application of the methods of USLE,MUSLE, GAVRILOFF and MATHEMATICALCORRELATION OF LIQUID AND SOLID VOL-UMES is made, to estimate expectable futurevolume of suspension sediment in dam of Po-trero de las Tablas, on the Lules River in theProvince of Tucumán, Argentine Republic.The necessary parameters for the applicationof the mentioned methods are determined andthe hypotheses of work and the results ob-tained with each one are compared.

The information to use is included in thetopics of morphology, hydrometric, hydrom-eteorology, land use and fluvial hydraulics.

The results of the comparison are ex-pressed graphically and in percentage.

Conclusions are obtained about the effec-tiveness of the methods applied in mountainriver basins as the one of the Lules River andthe consequences of the sediment deposit inthe future dams are analyzed.

AN ESTUARINE FOSSIL ASSEMBLAGEFROM THE YACORAITE FORMATION(MAASTRICHTIAN-DANIAN) AND ITSPALEOENVIRONMENTAL SIGNIFICANCE.JUJUY - NORTHWESTERN ARGENTINECónsole Gonella, C. A.,1, 2 L.R. Horta,1 P.E. Herrera

Oviedo ,1 M. Grif f in,2 S.M. Georgief f,1, 3 F.G.

Aceñolaza1 2

1 Facultad de Ciencias Naturales e IML. Universidad

Nacional de Tucumán. Miguel L i l lo 205,

T4000JFE, San Miguel de Tucumán, Argentina.2 INSUGEO (Instituto Superior de Correlación Geoló-

gica) – CONICET. Miguel Lillo 205 (4000). S.M. de

Tucumán, Argentina.3 IESGLO (Instituto de Estratigrafía y Geología Sedi-

mentaria Global). Miguel Lillo 205, T4000JFE, San

Miguel de Tucumán, Argentina.

We describe a brackish water fossil as-semblage from Yacoraite Formation (Maas-trichtian – Danian), in the localities ofMaimará and Jueya, Jujuy - Northwest Ar-gentine. The dominant lithology of the studylevels is characterized by a calcareous sand-stones succession, with ripplestratified struc-ture, fining-upward. Fine to very fine sand-stone lenses occur in this fossiliferous inter-

val. The sandstones are interpreted as stormwashover deposits. In these sequences wehave found numerous disarticulated remainsof fishes (Pycnodontiforms and Siluriforms),fragments of tetrapods? (Tetrapoda), a toothof crocodile (Crocodylidae), preserved mol-lusks (Gastropods and Bivalves) of problem-atic taxonomy, stromatolites (LLHC, LLHSand dome type). Also was identified a set offossil traces integrated by traces of birds(Avipedidae) and Skolitos ichnofacies , be-sides a Domichnia trace on an estromatoliticrock, caused by a perforant bivalve, alsopreserved. The study of the fossils assem-blage, traces, sediments, and sedimentarystructures indicates a brackish mixed envi-ronment, of low depth and high energy, prob-ably estuarine.

GRADUAL LATERAL RIVER MIGRATIONINDUCED BY LATERAL FLOODPLAINTILTING; A 3D NUMERICAL SIMULATIO

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Acta geológica lilloanalillo.org.ar/revis/geo/2009-21-sup/AGN-2009-s-2.pdf · 2015. 10. 29. · 2 Acta geológica lilloana 21 – ISSN 0567-7513 – Suplemento, 9th ICFS, 2009 Acta