Marine Geology of Indonesia

8/20/2019 Marine Geology of Indonesia

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Berita Sedimentologi MARINE GEOLOGY OF INDONESIA – PART 2

Number 33 – August 2015

Published by

The Indonesian Sedimentologists Forum (FOSI) The Sedimentology Commission - The Indonesian Association of Geologists (IAGI)

Indonesian Marine

Geology ResearchVessels: TheirCapacity andActivity page 5

Tertiary Uplift and the

Miocene Evolution ofthe NW Borneo ShelfMargin page 21

Benthic Foraminifera in Marine SedimentRelated to Environmental Changes off

Bangka Island, Indonesia page 47


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Editorial Board

MinarwanChief Editor Bangkok, Thailand

E-mail: [email protected]

Herman Darman

Deputy Chief EditorShell International EPKuala Lumpur, MalaysiaE-mail: [email protected]

Fatrial BahestiPT. Pertamina E&PNAD-North Sumatra AssetsStandard Chartered Building 23rd Floor

Jl Prof Dr Satrio No 164, Jakarta 12950 - IndonesiaE-mail: [email protected]

Mohamad Amin Ahlun NazarUniversity Link CoordinatorPT. Pertamina E&P, Asset 5 Jakarta, IndonesiaE-mail: [email protected]

Visitasi FemantTreasurer

Pertamina Hulu EnergiKwarnas Building 6th Floor Jl. Medan Merdeka Timur No.6, Jakarta 10110E-mail: [email protected]

Rahmat UtomoBangkok, ThailandE-mail: [email protected]

Farid FerdianSaka Energi Indonesia Jakarta, IndonesiaE-mail: [email protected]

Advisory Board

Prof. Yahdi ZaimQuaternary Geology

Institute of Technology, Bandung

Prof. R. P. KoesoemadinataEmeritus Professor

Institute of Technology, Bandung

Wartono RahardjoUniversity of Gajah Mada, Yogyakarta, Indonesia

Ukat Sukanta ENI Indonesia

Mohammad SyaifulExploration Think Tank Indonesia

F. Hasan Sidi

Woodside, Perth, Australia

Prof. Dr. Harry Doust Faculty of Earth and Life Sciences, Vrije UniversiteitDe Boelelaan 10851081 HV Amsterdam, The NetherlandsE-mails: [email protected];[email protected]

Dr. J.T. (Han) van Gorsel6516 Minola St., HOUSTON, TX 77007, USAwww.vangorselslist.com

E-mail: [email protected]

Dr. T.J.A. Reijers Geo-Training & TravelGevelakkers 11, 9465TV Anderen, The NetherlandsE-mail: [email protected]

Dr. Andy Wight formerly IIAPCO-Maxus-Repsol, latterly consultantfor Mitra Energy Ltd, KLE-mail: [email protected]

• Published 3 times a year by the Indonesian Sedimentologists Forum (Forum Sedimentologiwan Indonesia, FOSI), a commission of the

Indonesian Association of Geologists (Ikatan Ahli Geologi Indonesia, IAGI).

• Cover topics related to sedimentary geology, includes their depositional processes, deformation, minerals, basin fill, etc.

Cover Photograph:

The Baruna Jaya I research vessel.

Photo courtesy of BPPT – Agency for the

Assessment and Application of

Technology, Indonesia.

(http://barunajaya.bppt.go.id/index.php/

id/armada/item/12-k-r-baruna-jaya-

i.html)

mailto:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]


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Dear Readers,

We're pleased to deliver anotheredition of Berita Sedimentologiinto your hands. This volume isBerita Sedimentologi No. 33 withthe main theme on Marine

Geology of Indonesia.

We included four articles in thispublication, which consist of:- Indonesian Marine GeologyResearch Vessels: Their Capacityand Activity, written by AiYuningsih et al.- Making the Most ofBiostratigraphic Data; Examplesfrom Early Cretaceous to Late

Jurassic Shallow Marine SandUnits in Papua New Guinea andAustralasia, written by MikeBidgood et al.- Tertiary Uplift and the MioceneEvolution of the NW Borneo ShelfMargin, written by Franz Kessler

and John Jong; and- Benthic Foraminifera in MarineSediment related toEnvironmental Changes ofBangka Island, Indonesia, writtenby Kresna Dewi et al.

On organizational change, wewould like to announce that M.Amin Ahlun Nazzar has teamedup with us as our University Link

Coordinator, replacing WayanHeru Young. Amin will help FOSIto create a stronger link withstudents whose research interestsare in sedimentology/sedimentarygeology. We also thank WayanHeru for all his contribution to

FOSI.

We hope you’ll get benefit ofarticles published in BeritaSedimentologi and if you’d like tocontribute by submitting yourarticles, please do not hesitate tocontact us.

Warm regards, Minarwan

Chief Editor

INSIDE THIS ISSUE

Indonesian Marine Geology ResearchVessels: Their Capacity and Activity – A.Yuningsih et al.

5

Book Review : The SE Asian Getway:History and Tectonic of the Australian-Asia Collision, editor: Robert Hall et J.A.Reijers

56

Making the Most of Biostratigraphic Data;

Examples from Early Cretaceous to LateJurassic Shallow Marine Sand Units inPapua New Guinea and Australasia – M.Bidgood et al.

11

Book Review - Biodiversity,Biogeography and Nature Conservationin Wallacea and New Guinea (Volume 1),Edited by D. Telnov, Ph.D. – H. Darman

58

Tertiary Uplift and the Miocene Evolutionof the NW Borneo Shelf Margin – F. L.Kessler and J. Jong

21

Benthic Foraminifera in Marine SedimentRelated to Environmental Changes offBangka Island, Indonesia – K.T. Dewi et al. 47

Berita Sedimentologi

A sedimentological Journal of the Indonesia Sedimentologists Forum

(FOSI), a commission of the Indonesian Association of Geologist (IAGI)

From the ditor

Call for paper BS #34 –

to be published in December2015


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About FOSI

he forum was founded in1995 as the Indonesian

Sedimentologists Forum(FOSI). This organization is acommu-nication and discussionforum for geologists, especially for

those dealing with sedimentologyand sedimentary geology inIndonesia.

The forum was accepted as thesedimentological commission ofthe Indonesian Association ofGeologists (IAGI) in 1996. About300 members were registered in1999, including industrial andacademic fellows, as well asstudents.

FOSI has close internationalrelations with the Society of

Sedimentary Geology (SEPM) andthe International Association ofSedimentologists (IAS).Fellowship is open to those

holding a recognized degree ingeology or a cognate subject andnon-graduates who have at leasttwo years relevant experience.

FOSI has organized 2international conferences in 1999and 2001, attended by more than150 inter-national participants.

Most of FOSI administrative workwill be handled by the editorial

team. IAGI office in Jakarta willhelp if necessary.

The official website of FOSI is:

http://www.iagi.or.id/fosi/

Any person who has a background in geoscience and/or is engaged in the practising or teaching of geoscienceor its related business may apply for general membership. As the organization has just been restarted, we useLinkedIn (www.linkedin.com) as the main data base platform. We realize that it is not the ideal solution,and we may look for other alternative in the near future. Having said that, for the current situation, LinkedInis fit for purpose. International members and students are welcome to join the organization.

T

FOSI Membership

FOSI Group Memberas of AUGUST 2015: 961 members

http://www.iagi.or.id/fosi/http://www.iagi.or.id/fosi/http://www.iagi.or.id/fosi/


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Indonesian Marine Geology Research Vessels: Their

Capacity and Activity

Ai Yuningsih1, Wahyu Pandoe2 and Herman Darman2 1Marine Geological Institute (P3GL), Bandung, Indonesia.2 Agency for the Assessment and Application of Technology , Indonesia (BPPT).3Shell International EP, Kuala Lumpur, Malaysia.

Corresponding author: [email protected]

INTRODUCTION

About two thirds of Indonesian territory is coveredby sea, below which there is little-documented andfascinating geological features which require study.Observing and understanding this geology is

obviously technically more difficult than for theonshore. Thus, knowledge of the submarinegeology relies on research and commercial ships.

The marine geology of Indonesia has been studiedsince the 18th century. Two French ships calledBoudeuse and Etoile , and led by De Bougainvillesailed to collect data in 1768. Since then manyother research vessels came and were run byresearchers from the UK, Austria, the Netherlands,USA, Germany and Japan. In late 1980s Indonesiabought its own research vessel, Baruna Jaya 1,

and since then has built its own fleet of researchvessels.

The four institutions which run research vessels inIndonesia are:1.

BPPT – Badan Pengkasijan dan Penerapan Teknologi or the Agency for the Assessment andApplication of Technology. It is a non-departmental government agency under the

coordination of the Ministry of Research and Technology, which has the tasks of carrying outgovernment duties in the field of assessmentand application of technology. BPPT operates 4

Baruna Jaya vessels. BPPT named theirresearch vessels as Baruna Jaya I, Baruna JayaII, Baruna Jaya III and Baruna Jaya IV

2.

P3GL – Pusat Penelitian dan PengembanganGeologi Kelautan or Marine Geological Institute,under the ministry of Energy and MineralResources. This organization has been tasked tocarry out research, development, surveys andconduct systematic mapping of the marinegeology of Indonesia. P3GL has one GeomarinIII research vessel.

3.

LIPI – Lembaga Ilmu Pengetahuan Indonesia orIndonesian Institute of Sciences. LIPI manages

two research vessels: Baruna Jaya VII and

Baruna Jaya VIII. The Baruna Jaya VII is afishery patrol vessel and the Baruna Jaya VIII isone of the most modern research vessels inIndonesia, equipped for biological, geologicaland oceanographic surveys.

4. Balitbang KP – Badan Penelitian dan

Pengembangan Kelautan dan Perikanan orAgency for Marine and Fisheries Research andDevelopment of the Ministry of Marine Affairsand Fisheries. This agency operates severalresearch vessels including KR. Madidihang and

the newest vessel Bawal Putih III .

THE RESEARCH VESSELS

BPPT Baruna Jaya (BJ) research fleet comprisesthe four ships named above (Figure 1). All built byCMN in Cherbourg, France, the first three wereconstructed in 1989-1990 while the latest was

built in 1995. Each of them can carry 11-17 crewand 28 scientists. These ships are about the samein dimension with 60.4 meters in length and 11.6m in width. The gross weights of BJ I, II and III weigh 1184 tonnes and BJ IV is slightly heavier

with gross weight of 1219 tonnes. Their cruisingspeeds range from 8 to 10 knots (Table 1).

Each ship has different functions. BJ II , forexample has 2D seismic acquisition facility, BJ III

has oceanographic/geological research facility. Theseismic processing unit has industrial standard

equipment, using Linux-based software such asProMAX TM. BJ I has deep sea multipurposeresearch facility and BJ IV has hydrographic,

oceanographic and fishing research instruments.BPPT has research instruments which can be

added, such as side scan sonar unit,magnetometer, marine resistivity, sample grabber,dredging tool and coring tool.

BJ VII is fishery patrol vessel and BJ VIII is a high

end research vessel that can conduct geologicaland geophysical surveys. Both vessels wereoperated by LIPI. BJ VIII was built by PT. PAL in

Surabaya, Indonesia.


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P3GL manages 3 vessels called Geomarin I,Geomarin II and Geomarin III (Figure 1). Geomarin I

has been used to complete shallow water mappingin western Indonesia. Geomarin II is a small boat

which is useful for coastal and river mapping.Recently it was used for river survey on the impactof Sidoarjo mud in Porong River, East Java. P3GL ’ sGeomarin III is a modern research vessel, which

was completed in Japan and operated in 2008. It

replaced previous Geomarin I and II vessels.Compared to the Baruna Jayas, Geomarin III is

slightly bigger. It is 61.7 m long, 12 m wide and itsgross weight is 1300 tonnes (Table 1). Geomarin III

is equipped with modern facilities such as 2Dseismic acquisition equipment with 480 channels,onboard seismic processing unit, also multibeam,side scan sonar, and magneto-gravity meter

Figure 1. Indonesian research

vessels under BPPT management

are: (a) Baruna Jaya I, (b) Baruna

Jaya II, (c) Baruna Jaya III and (d)

Baruna Jaya IV. LIPI manage (e)

Baruna Jaya VII and (f) Baruna

Jaya VIII. Geomarin I (g),

Geomarine II (h) and Geomarine III

(i) are run by P3GL. Madidihang (j)

and the newest Bawal Putih III (k)

belong to Balitbang KP.


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instrument. It also has sediment coring systemand onboard laboratory.

RESEARCH ACTIVITIES

Baruna Jaya vessels were involved in manyresearch activities. The following are examples oftheir marine geology related projects in the last 5

years:- Seram: Geological and geophysical 1:500.000scale mapping in Seram Sea.- Ternate and Kapuas: Sea bottom profile /bathymetric mapping.- Makassar Strait: marine resistivity survey.- Mahakam Delta: abrasion survey for Total EPIndonesié.- Bangka Island: submarine mineral depositmapping around the island.- Natuna Sea: Geophysical and geotechnicalsurvey.- Tsunami buoy placement, replacement and

maintenance.

The research vessels managed by BPPT are up toindustrial standards; therefore they were also usedin a number of industrial activities. TotalIndonesié, ExxonMobil, Elnusa, EMP Kangean andFugro are examples of petroleum relatedcompanies which used the Baruna Jaya vessels.

The Seismic data acquired by Baruna Jaya infrontier areas of Indonesia provide initial regionalunderstanding (Figure 2). Although their coveragesare sparse, they gave preliminary view on thegeology. Some surveys with potential will befollowed by denser seismic with better resolution.

P3GL ’s Geomarin III has also completed a number

of significant research projects related toIndonesian marine geology. Figure 3A shows themarine geological map of Indonesia based onGeomarine surveys. The western part of Indonesiahas been covered but there are still significantareas to be covered in Eastern Indonesia. Figure

3B shows the map quadrants completed by P3GLso far. The current project aims to complete

significant areas in eastern Indonesia by 2019.

Figure 2. The cover of Samples of Seismic Profile on Baruna Jaya Seismic Atlas, prepared in 1990’s by

BPPT. The cover also shows the coverage of Baruna Jaya vessel (source H. Darman).


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Figure 3. A) Sea bottom sediment compiled from 1 : 250.000 systematic mapping result of P3GL from 1984

to 2012. The units are defined based on the distribution of sediment texture and composition (Usman, E.,

2014).B) Geological and geophysical map quadrant of 1:250.000 scale. Yellow boxes indicated completed

quadrant. The area indicated with black outline is the 2013-2019 mapping project area (Arifin, L., 2013).


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CONCLUSION

The vast area of Indonesia needs to be explored. There are still areas with very limited geologicalunderstanding, especially remote offshore areas

but the five research vessels of Indonesia areinsufficient to cover them. Until funds are availableto increase the size of this hard-worked fleet,proper and detailed planning in conductingsurveys becomes critical for efficient, cost-effectivesurveying.

REFERENCES

Arifin, L., 2013. Pemetaan Geologi dan Geofisika diPerairan Indonesia. Majalah Mineral danEnergi, Vol. 11, No. 4 – December.

BPPT Baruna Jaya website:http://barunajaya.bppt.go.id/index.php/id.html

Geomarin I-III website:http://www.litbang.esdm.go.id/index.php?option=com_content&view=category&layout=blog&id=83&Itemid=94

Usman, E., 2014. Data Dasar untuk PenyusunanPeta dan Kebijakan Pengelolaan SumberDaya Mineral Kelautan Indonesia. MajalahMineral dan Energi, Vol. 12, No. 2 - June

P3GL website: http://www.mgi.esdm.go.id/

http://barunajaya.bppt.go.id/index.php/id.htmlhttp://barunajaya.bppt.go.id/index.php/id.htmlhttp://www.litbang.esdm.go.id/index.php?option=com_content&view=category&layout=blog&id=83&Itemid=94http://www.litbang.esdm.go.id/index.php?option=com_content&view=category&layout=blog&id=83&Itemid=94http://www.litbang.esdm.go.id/index.php?option=com_content&view=category&layout=blog&id=83&Itemid=94http://www.mgi.esdm.go.id/http://www.mgi.esdm.go.id/http://www.litbang.esdm.go.id/index.php?option=com_content&view=category&layout=blog&id=83&Itemid=94http://www.litbang.esdm.go.id/index.php?option=com_content&view=category&layout=blog&id=83&Itemid=94http://www.litbang.esdm.go.id/index.php?option=com_content&view=category&layout=blog&id=83&Itemid=94http://barunajaya.bppt.go.id/index.php/id.htmlhttp://barunajaya.bppt.go.id/index.php/id.html


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Making the Most of Biostratigraphic Data; Examples from

Early Cretaceous to Late Jurassic Shallow Marine SandUnits in Papua New Guinea and Australasia

Mike Bidgood1, Monika Dlubak2 and Mike Simmons2 1GSS International, 2 Meadows Drive, Oldmedrum, Aberdeenshire, AB51 0GA, UK.2

Neftex Petroleum Consultants Ltd., 97 Jubilee Avenue, Milton Park, Abingdon, Oxfordshire, OX14 4RW,UK.

Corresponding author: [email protected] ; [email protected] ;

[email protected]

ABSTRACT

A fundamental task in the exploration workflow is the mapping of reservoir sand units within a

broader paleogeography. Such maps help, for example, to predict reservoir extent and link sandsback to likely sediments sources thereby helping to improve reservoir quality predictions. If thesesand units are multiple bodies within a relatively narrow time-stratigraphic interval, mapping ofindividual sands can be difficult if we rely on simple lithostratigraphic differentiation, orchronostratigraphic terminology (“ages”) for correlation.

An example of this is shown from the Early Cretaceous to Late Jurassic shallow marine sands ofsoutheast Papua New Guinea and Australasia. Previously correlated only on a broad timescaleand often with overlapping age-range for individual lithostratigraphic units, it can be difficult todetermine the precise stratigraphic position of each of these sands (e.g. the important ToroSandstone reservoir) which in turn can affect interpretations regarding their exploration and

production characteristics.

The evaluation of large, public-domain, biostratigraphic datasets has allowed for the constructionof a detailed “synthesis biozonation” for the area which permits more reliable identification and

stratigraphic placement of individual sand units and which further allows for improvedcorrelation at local and regional scale and improved mapping.

INTRODUCTION

The Toro Sandstone is an important hydrocarbonreservoir rock in southeast Papua New Guinea (the“Papuan Basin – Shelf Platform” USGS basin) –

Figure 1 – and is generally considered to be of Late Jurassic to Early Cretaceous in age. Related sandbodies of similar general age include units labelledvariously as Alene, which occurs stratigraphicallyabove the Toro Formation, and the Digimu,P’nyang, Hedinia and Iagifu units together with aninformal unit known as “X” all of which occurstratigraphically below the Toro. The literatureshows much disagreement as to thelithostratigraphic definitions and relationshipsbetween many of these units (see Davey, 1999 andbelow for a brief discussion), particularly the

status of the Toro unit itself and its internal

subunits. Discussions as to the correctlithostratigraphic assignment of bed, member orformation status to these units is beyond the scopeof this work and – notwithstanding such

assignments given in the general descriptionsbelow – they are treated here as separate informal

“units”.

The main Toro unit has been subdivided into threesubunits; in descending order Toro A, Toro B and Toro C (Madu, 1996; De Vries et al ., 1996 andAzizi-Yarand and Livingstone, 1996) with the “B”unit being somewhat shaleier than those aboveand below it. The status of the “C” unit is

particularly debateable with Davey (1999)seemingly equating it with sands previouslyassigned to the Digimu unit (upper ImburuFormation) in the Toro’s type section. This has ledto the concept of a so-called “Digimu lobe” of the Toro Formation and a degree of uncertainty as toits status.

Overall, these various sand units are believed to beshallow marine shelf sands as determined mainlyby their palynological content (organic-walledmicroplankton, spores and pollen).

mailto:[email protected]:[email protected]:[email protected]:[email protected]


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In a regional context, these sediments form part ofthe Middle Jurassic – Early Cretaceous GondwanaSyn-Rift Megasequence and were deposited in apassive margin setting on a relatively stablemarine shelf, which progressively deepened

towards the north-east. Across the more proximalsouth-western portion of the basin, a series ofinterbedded sandstones and shales comprising theKoi-Lange Formation were depositedunconformably above the Barikewa Formation. These sandstones represent potential hydrocarbonreservoirs, whilst interbedded shales becomeincreasingly organic-rich towards the north-eastwhere they may have source potential with TOC of1-1.5% (Burns & Bein, 1980). The Koi-LangeFormation is overlain conformably by the Imburu

Formation which is typically divided into 4members. The Lower Imburu Member comprises

mainly shales with some source potential, whilstthe younger Iagifu, Hedinia and Digimu memberscomprise some important blocky coarseningupward reservoir sandstone bodies.

Early Cretaceous sediments continued depositionin a passive margin setting as the upper part of theGondwana Syn-Rift Megasequence. The ToroSandstone represents one of the most importanthydrocarbon reservoirs within the basin and iscapped by thick regionally extensive shales of theIeru Formation, which form the principle seal.

These formations are overlain by thick shales andsiltstones of the chronostratigraphically equivalent

deeper water Maril Shale across the distal north-eastern part of the passive margin. The lineardistribution of productive hydrocarbon fields in thefrontal part of the Papuan Fold Belt marks thedistal limit of sandstone deposition within this

megasequence.

Distally, beyond this limit (the “Darai Shelf Edge”of Hill et al ., 2000), shales and mudstones of the

Maril Shale or Om Formations (“Jurassic”) and theChim Formation (“Cretaceous”) are deposited.Using sequence stratigraphic principles, Hill et al .

proposes the existence of Toro equivalent lowstandfans beyond the shelf edge derived fromcannibalised Toro shelf sands (Figure 1).

RELATIVE AGES OF THE SAND UNITS

Many authors, with or without biostratigraphicdata, have assigned various age or biozone labelsto the sand units forming this study (e.g. Davey,1987, 1999; Denison and Anthony, 1990; Granathand Hermeston, 1993; Hill et al ., 2000; Hirst and

Price, 1996; Johnstone and Emmett, 2000; Madu,1996; McConachie and Lanzilli, 2000; McConachieet al ., 2000; Morton et al ., 2000; Phelps and

Denison, 1993; Powis, 1993; Varney andBrayshaw, 1993; Welsh, 1990; Winn et al ., 1993).

A summary of these composite age/zonal ranges isshown in Figure 2.

Figure 1. Generalised stratigraphy of the Late Jurassic to Early Cretaceous of Papua New Guinea (based onHill et al., 2000) and location of the study area. Chronostratigraphic timescale is approximate, but based on

biozones from this study.


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These composite age ranges are clearly unrealisticand have no practical value for correlationpurposes. Therefore how do they come about? Oneof the most likely sources is the over-reliance onusing interpreted ages as a basis for correlation.Chronostratigraphic (age) interpretations asderived from calibration of biostratigraphic zonesand events can and do change, sometimesfrequently and often significantly. The reasons forthis are many-fold and include iterative re-definitions of stage boundaries and improved

techniques (biostratigraphic, magnetostratigraphic,radio-isotopes, geochemical excursions, orbitalcalibration etc.) for recognising them. TraditionalEuropean-based stages, many of which were

defined in proximal settings and separated bysignificant unconformities, are being replaced bynew subdivisions based on marine sections withcontinuous deposition which allows easier globalcorrelation. The four chronostratigraphic stagesthat are of interest to us here have lower boundaryages which have varied between the followingvalues since the 1980’s alone:

Valanginian 128.0 – 140.7Berriasian 133.0 – 145.6 Tithonian 140.0 – 152.1Kimmeridgian 145.0 – 157.3

This also means the duration of stages can vary

considerably. It is easy to see why a worker usingone timescale might regard a section as Berriasian,while another worker using a different timescalewould attach a Tithonian label.

These chronostratigraphic changes can have twosignificant adverse effects – the first, by incorrectlycorrelating separate strata given a similarchronostratigraphic age by two separate workersone of whom has made an incorrect interpretation

because definitions may have changed (see, forexample, the redefinition of the boundary betweenthe Campanian and Maastrichtian stages; Odin,2001 and Ogg, Hinnov and Huang, 2012; pp. 806-

808). For example, a stratigraphic section of thePhanerozoic of Papua New Guinea in McConachieet al ., 2000 shows the Toro unit placed

(incorrectly) within the Valanginianchronostratigraphic stage without any apparent justification for that age interpretation.Subsequent workers using this information maymiss-correlate the Toro with other local sand unitsof a proven Valanginian age, or believe genuine

Toro sands are not, in fact, Toro due to them not having a Valanginian age.

The second main source of error arises by notcorrelating separate strata given differentchronostratigraphic ages by two workers who each

Figure 2. Summary of the range of maximum and minimum age assignments conferred on sand units by

various authors, shown against the Gradstein et al., 2012 time scale.


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has a different “concept” of the chronostratigraphybut who are, in fact, talking about the samestratigraphic section. An example of this concernsthe lack of formal definition of the Jurassic – Cretaceous system (Berriasian – Tithonian stages)boundary where there are no fewer than 14

separate candidate markers for the boundaryspread over a 3-4 million year time-span (see Ogg,Hinnov and Huang, 2012; pp. 795-797). Thereforeit seems one person’s concept of “early Berriasian”may in fact be the same as another’s concept of“late Tithonian” but the two sections wouldnormally never be correlated, or may be incorrectlythought of as being diachronous. Such errors are

frequently perpetuated in the literature thusfurther compounding the problem.

Differences of opinion between paleontologists isanother factor, both by workers within the samefossil group and workers between different fossil

groups. For example, four important biozonationschemes based on palynology applicable to thePapua New Guinea region which cover the Late Jurassic and Early Cretaceous interval are those ofDavey, 1987 and 1999; Helby, Morgan andPartridge, 1987 and Welsh, 1990. Each hassimilarities with, and differences from, the other(see Figure 3).

Figure 3. Synthesis Biozonation scheme for the Late Jurassic – Early Cretaceous interval in the Papua NewGuinea region, including some of the important palynological schemes used in its construction. Standard

Chronostratigraphy is based on Gradstein et al., 2012. Chart constructed using TSCPro ©.


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Further sources of error may include the incorrectapplication of lithostratigraphy and possibly evensimple counting errors such as... “This is the fourthsandstone unit encountered, therefore it must be theP’nyang unit ” without independent confirmation.

Ensuring that the various biozonation schemes arecorrectly calibrated to global standards is a vitalstep in being able to correlate the differentschemes together. This involves the screening of allavailable palynological data throughout the region

to identify those fossil extinction and inceptionhorizons which are the most consistently andconfidently recorded. This only works as long asthe (in this case palynological) data itself has been

consistently recorded and calibrated against globalstandard biozonation schemes and timescales.

This workflow applies equally to other fossilgroups.

Note that in some instances (as in Figure 3) it canbe seen that the same stratigraphic zonal interval

is given different species names by the differentauthors and occasionally the boundaries betweenthe zones do not match up. This is, of course,scientifically correct especially if different fossilgroups are used (i.e. spores & pollen versusdinoflagellates) but is potentially very confusing for

a non paleontologist. Correlation of differentstratigraphic sections zoned by different workersusing different fossil groups is only possible if thistype of diagram – a “Rosetta Stone ” – is properly

calibrated and available.

Figure 4. Synthesis biozones applied to the Hedinia-1X well allowing the biostratigraphic fingerprintingof sand units and the strata between them. Note that the synthesis biozone PNG 1K identified in thelower part of the Toro unit beneath a clear biostratigraphic hiatus suggests this should be reinterpreted

as a Digimu equivalent. (Well data from Winn et al., 1993 and Denison and Anthony, 1990).


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The next logical step would be to further integratethe (calibrated) zonation schemes and bioeventsfrom additional fossil groups and to construct afull “synthesis biozonation” based on the mostreliable, widespread and confident bioevents.“Synthesis biozones” allow correlation at local andregional scales independent of current or past

timescales and avoiding the need to communicatewith potentially confusing and/or obsolete fossilnames.

Figure 3 shows the results of such a process forthe Kimmeridgian to Hauterivian stages of thePapua New Guinea area and four of the moreimportant individual palynological schemes usedin the construction. The full data set which wasused comprises many more schemes frompalynology and many other fossil groups and is notshown here.

The “synthesis biozones” are calibrated against aseries of standard, global biozones – in this case Tethyan ammonites.

Applying these synthesis biozones to well data wecan biostratigraphically “fingerprint” observedlithological units such as these various sandbodies (Figure 4).

By applying this technique to multiple wells, all ofwhich were previously zoned to a greater or lesserdegree by different workers using different localschemes, it is possible to arrive at a clearer idea ofthe exact stratigraphic levels upon which thesesand units lie (Figure 5). Compared to the initial

age assignments shown in Figure 2, this showsconsiderable improvement in resolution whichenables much greater confidence in correlating

these sand bodies across the region.

The calibration of the synthesis biozonationscheme to global standard schemes allows thetechnique to be carried over into nearby regionsand possibly even further beyond. An examplefrom similar-age sand units in the Ichthys Field(Northwest Shelf, Australia) shows how these toocan be biostratigraphically “fingerprinted” usingthe same synthesis zone model as for Papua NewGuinea.

Berriasian sand units in Titanichthys-1 (Figure 6)

appear to be biostratigraphically equivalent tosands identified as Digimu and Toro in Papua NewGuinea.

Figure 5. Biozonal assignment of individual sand units from the PNG area. Standard Chronostratigraphy is

based on Gradstein et al., 2012.


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Regional knowledge (Andrew Lavender, pers.comm .) indicates that the Ichthys sands are more

likely to be deposited in a slope setting andtherefore may cautiously support a similar modelproposed by Hill et al ., 2000, for the presence of

lowstand Toro sands in PNG, although such sandshave yet to be proved, and the thicker shelf sandsin PNG (compared with thinner shelf sands in NWAustralia) might indicate lesser degrees ofcannibalisation and shelf by-pass. Figure 7presents a schematic paleogeography.

CONCLUSIONS

Much valuable local biostratigraphic data,irrespective of publication date, is under-utilisedbecause of a lack of calibration to globalstandards, reducing their utility for optimumcorrelation, especially at regional scale. There is a

tendency among geoscientists to correlate usingchronostratigraphic (age) units rather thanbiostratigraphic units – this can be potentially

misleading if not applied very carefully. Ages are,after all, an interpretation contemporary only tothe date of publication. It is the biostratigraphicdata that is the fundamental correlation tool.

Critical screening of large biostratigraphic datasets across multiple fossil groups allows consistentand reliable bioevents to be identified to construct

a “synthesis biozonation scheme” which permitsmore confident correlation within a basin, and a

“Rosetta Stone” to allow workers to fit their localdata within a standard zonal framework forregional studies, which is independent of an ever-changing global timescale and undefined stageboundaries.

Figure 6. Biostratigraphic "fingerprinting" of sand units in Titanichthys-1 (Ichthys field, AustralianNorthwest Shelf). Biozonal correlation with similar units in the PNG Hedinia-1X well show that many of these

sand units were deposited during the same sequence cycles. (Well data from WAPINS database, 2008).


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The technique has been applied in the Papua NewGuinea/NW Australia area and increases thepower to discriminate between reservoir sand unitsand place them within the context of a globalsequence model.

In appropriate circumstances the technique andzonation scheme may be applied regionally,outside the basin within which it was constructed.

This has shown that biostratigraphicallyequivalent sands have been recorded on theAustralian NW Shelf which may be lowstand

equivalents of highstand/transgressive sands inPapua New Guinea and lends cautious support toa possible “lowstand Toro” play model in that area.

ACKNOWLEDGEMENTS

The authors would like to thank their colleagues atNeftex: James Barnett for valuable discussions onPNG regional geology, Andy Lavender forinformation on the Ichthys Field, Allie Nawell for

drafting and Ellen Foster for help with welldiagrams.

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and hydrocarbon potential of the Mesozoic ofthe western Papuan Basin, Papua NewGuinea. APPEA Journal (AustralianPetroleum Exploration Association Journal),v. 20, no. 1, p. 1-15.

Davey, R.J. 1987. Palynological zonation of theLower Cretaceous, Upper, and Upper Most

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Figure 7. Generalised Berriasian paleogeography relating to the Toro Sandstone and related units from

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Memoir no. 17, Geological Survey of PapuaNew Guinea, 1-51 p.

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DeVries, M.S., R.D. Parish and J.L. Ryan 1996.Horizontal well drilling in the Kutubuproject, Papua New Guinea. In P.G.Buchanan (Eds.), Petroleum Exploration,Development and Production in Papua NewGuinea; proceedings of the 3rd PNGPetroleum Convention, p. 551-561.

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Granath, J.W. and S.A. Hermeston 1993.Relationship of the Toro SandstoneFormation and the Alene Sands of Papua tothe Woniwogi Formation of Irian Jaya. InG.J. Carman and Z. Carman (Eds.),

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2000. Structural and stratigraphic shelf-edge hydrocarbon plays in the Papuan foldbelt. In P.G. Buchanan, A.M. Grainge andR.C.N. Thornton (Eds.), Papua New Guinea'spetroleum industry in the 21st century;Proceedings of the Fourth PNG PetroleumConvention, Port Moresby, p. 67-85.

Hirst, J.P.P. and C.A. Price 1996. Sequencestratigraphy and sandstone geometry of the

Toro and Imburu formations within thePapuan fold belt and foreland. In P.G.Buchanan (Eds.), Petroleum Exploration,Development and Production in Papua NewGuinea; proceedings of the 3rd PNGPetroleum Convention, p. 279-299.

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Guinea: Proceedings of the First PNGPetroleum Convention, Port Moresby, 12-14th February, 1990, p. 107-117.

Johnstone, D.C. and J.K. Emmett 2000. Petroleumgeology of the Hides Gas Field, SouthernHighlands, Papua New Guinea. In P.G.

Buchanan, A.M. Grainge and R.C.N. Thornton (Eds.), Papua New Guinea'spetroleum industry in the 21st centuryProceedings of the 4th PNG PetroleumConvention, Port Moresby, 29th-31st May2000, p. 319-335.

Madu, S 1996. Correlation sections of the Late Jurassic to Early Cretaceous succession inthe Papuan Fold Belt, Papuan Basin. In P.G.Buchanan (Eds.), Petroleum Exploration,Development and Production in Papua NewGuinea: Proceedings of the Third PNGPetroleum Convention, Port Moresby, 1996,p. 259-277.

Marshall, N.G. and S.C. Lang 2013. A NewSequence Stratigraphic Framework for theNorth West Shelf, Australia. West AustralianBasins Symposium 2013. Expanding ourhorizons, 18-21 August 2013, Perth WesternAustralia. PESA, Petroleum ExplorationSociety of Australia, p. 1-32.

Mason, H.D. And B.A. McConachie 2000. CrossCatalina Anticline; an oil accumulation in

the New Guinea fold belt in Irian Jaya (westPapua). In P.G. Buchanan, A.M. Graingeand R.C.N. Thornton (Eds.), Papua NewGuinea's petroleum industry in the 21stcentury Proceedings of the 4th PNGPetroleum Convention, Port Moresby, 29th-31st May 2000, p. 475-486.

McConachie, B.A. and E. Lanzilli 2000. Stanley gascondensate field discovery and the oilpotential of the Western Papuan Basin. InP.G. Buchanan, A.M. Grainge and R.C.N.

Thornton (Eds.), Papua New Guinea'spetroleum industry in the 21st centuryProceedings of the 4th PNG PetroleumConvention, Port Moresby, 29th-31st May2000, p. 427-442.

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Burge 2000. Extensions of the PapuanBasin Foreland geology into eastern Irian Jaya (West Papua) and the New Guinea FoldBelt in Papua New Guinea. In P.G.Buchanan, A.M. Grainge and R.C.N. Thornton (Eds.), Papua New Guinea’sPetroleum Industry in the 21st Century:Proceedings of the fourth PNG PetroleumConvention, Port Moresby, p. 219-237.

Mollan, R.G. and G.J. Blackburn 1990. Petroleumpotential of the Fly-Bamu Deltas Region. InG.J. Carman and Z. Carman (Eds.),Petroleum exploration in Papua New Guinea:Proceedings of the First PNG PetroleumConvention, Port Moresby, 12-14thFebruary, 1990, p. 215-226.

Morton, A.C., B. Humphreys, G. Manggal and C.M.

Fanning 2000. Provenance and correlationof Upper Jurassic and Lower Cretaceous

reservoir sandstones in Papua New Guineausing heavy mineral analysis. In P.G.Buchanan, A.M. Grainge and R.C.N. Thornton (Eds.), Papua New Guinea'spetroleum industry in the 21st centuryProceedings of the 4th PNG Petroleum


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Convention, Port Moresby, 29th-31st May2000, p. 187-203.

Odin, G.S. 2001. The Campanian-Maastrichtianboundary: definition at Tercis (Landes, SWFrance) principle, procedure, and proposal.In G.S. Odin (Eds.), The Campanian-

Maastrichtian stage boundary;characterisation at Tercis les Bains (France)and correlation with Europe and othercontinents. Developments in Palaeontologyand Stratigraphy no. 19, p. 820-833.

Ogg, J.G., L.A. Hinnov and C. Huang 2012.Cretaceous. In F.M. Gradstein, J.G. Ogg,M.D. Schmitz and G.M. Ogg (Eds.), TheGeologic Time Scale 2012. Volume 2, p. 793-853.

Osborne, D.G. 1990. The hydrocarbon potential ofthe western Papuan Basin foreland - withreference to worldwide analogues. In G.J.Carman and Z. Carman (Eds.), Petroleumexploration in Papua New Guinea:

Proceedings of the First PNG PetroleumConvention, Port Moresby, 12-14th

February, 1990, p. 197-214.Phelps, J.C. and C.N. Denison 1993. Stratigraphic

thickness variations and depositionalsystems of the Ieru Formation, SouthernHighlands and Western Provinces, PapuaNew Guinea. In G.J. Carman and Z. Carman(Eds.), Petroleum exploration anddevelopment in Papua New Guinea.Proceedings of the Second PNG PetroleumConvention, Port Moresby, 31st May-2nd June, 1993, p. 169-190.

Powis, G.D. 1993. The Sequence Stratigraphy ofthe Mesozoic reservoirs of the GobeAnticline, Papuan Thrust Belt. In Carman,G.J. and Z. Carman (Eds.), Petroleumexploration and development in Papua New

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Varney, T.D. and A.C. Brayshaw 1993. A revisedsequence stratigraphic and depositionalmodel for the Toro and Imburu Formations,with implications for reservoir distributionand prediction. In G.J. Carman and Z.Carman (Eds.), Petroleum exploration anddevelopment in Papua New Guinea.Proceedings of the Second PNG PetroleumConvention, Port Moresby, 31st May-2nd June, 1993, p. 139-154.

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Western Australian Department of Industry andResources 2008. WAPIMS Database:Western Australia Digital Well Logs -Various. In Basin Data Packages, WesternAustralia. Geological Survey of WesternAustralia (GSWA).

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Tertiary Uplift and the Miocene Evolution of the NW Borneo

Shelf Margin

Franz L. Kessler1* and John Jong2 1 Independent Geosciences, Oil and Gas Consultant2 JX Nippon Oil and Gas Exploration (Deepwater Sabah) Limited

*Corresponding author: [email protected]

ABSTRACT

NW Borneo, of which the shelfal margin extends from the West Baram Line in the southeast tothe Balabac Line in the northwest, encompasses an area of active hydrocarbon exploration sincethe 1970’s. A large number of the earlier oil and gas finds are located in shelfal reservoirs of

Neogene age. In this study, we portray the development of the Miocene shelf from the

standpoints of stratigraphy, sea-level fluctuations, hinterland uplift and sediment recycling;mobile clay tectonics and, last but not least, the impact of the monsoon climate. Balancing thedifferent viewpoints, we believe the transition from a muddy Mid-Miocene shelf to an unusuallysandy one can be attributed to two independent factors, which are:

1.

The rise of the Borneo part of Sundaland in the Middle to Late Miocene, caused by tectoniccompression, in combination with the influence of the monsoon climate, and

2. The availability, through erosion of the Rajang/Crocker system, of massive amounts ofsand delivered to the basin in geologically short time intervals.

The Early to Mid-Miocene Cycle III/Stage III “Setap Shale” and other sediments in the BaramDelta appear characteristically lean in sand in most areas. The available data suggest that the

first massive regional sand pulse originated at the same time in the Baram Delta, Brunei and

Sabah, during Cycle IV/Stage IVA (Serravallian), post-MMU/DRU times. Continued sand supplyestablished a shelf edge that remained almost stationary throughout Mid Cycle V/Stage IVC. As

compression and uplift continued, the Middle to Late Miocene Cycles IV/V (Stages IVA-E) shelfsaw local modification by hydraulic clay injection. During Cycles V/VI, and also in the StagesIVD-F, we see a further major expansion of the shelf. The question, as to which of these pulsescan be linked to sea-level fluctuations, remains open; though it appears that the Borneo uplift has“outrun” rising sea -level at least since the Late Pleistocene.

Keywords: evolution, NW Borneo, Miocene, uplift.

INTRODUCTION

The purpose of this paper is to summarize theresults of studies, both published andunpublished, that help to explain the transitionfrom a mud-dominated, low-energy deeper watershelf in Cycle III/Stage III and leading to the sand-prone, post-MMU/DRU (Mid-MioceneUnconformity/Deep Regional Unconformity) largeshelfal margins from Cycle IV/Stage IVA onwards.However, there remains the question, which is yetto be fully resolved, how shelfal sedimentsunderlying the Cycle IV/Stage IVA sand pulses arerelated to each other in NW Borneo. These are:

1.

The gray Setap Shale/Sibuti Formation inSarawak (Central Luconia, Balingian Province),a sequence of marls, and fine silt to sandyturbidite beds with carbonate shoals developed

in places.

2.

The Setap Shale underlying the Baram Delta, aclay-dominated sequence with the occasional

thin sandstone beds; at the top, just beneaththe unconformity to Cycle IV/Stage IVA, there

are glauconite-rich green sands with a richforaminifera fauna.

3. The Temburong Formation (Brunei, Limbangand Sabah), clay-dominated with thinsandstone beds.

4.

The Kudat Formation, formed by clay and thinsands in NW Sabah.

Mazlan (1994) investigated the relationshipbetween the Temburong Formation and the SetapShale on Labuan Island, and came to the

conclusion that the Temburong and Setap are de- facto time-equivalent depositional sequences.

Based on different burial history, metamorphismand uplift, it can be argued that theRajang/Crocker Basin is tectonically andstratigraphically distinct from the NW Borneo


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(Baram-Balabac) Basin. The apparent lithologicalsimilarity between the Temburong and the Crockercommented in some studies might therefore becoincidental.

Regionally, the South China Sea corresponds to a

former area of Cenozoic crustal extension, flankedby the Asian continent (Vietnam, China), thePhilippines, and the Sundaland continent (areas of Java, Borneo, and Peninsular Malaysia). The areasaw periods of compression, manifested in strike-slip (and occasionally thrust) movements alongmajor lineaments (Hutchison, 2014: Jong et al.,2014 and 2015). Underlying the differentsedimentary fills of variable thicknesses, thebasement is formed predominantly of strongly tomoderately attenuated continental crust.

Figure 1 shows a summary map of the study areaof the South China Sea bounded by the majorlineaments of West Baram Line in the southeast

and the Balabac Line in the northwest. An indexmap of important outcrops and offshore locations

studied is shown in Figure 2.

An interesting (and economically important)phenomenon observed in our study is the suddenappearance of sandy shelves in Cycle IV/StageIVA, and related turbidite families in thedeepwater. In Sarawak / Brunei area, the early

development of the Baram Delta may be sub-divided into three phases in Brunei and Limbang(Sandal, 1996). The first, probably Lower to MiddleMiocene age, is called the Meligan Delta and was aprecursor pulse of sand which accumulated in aforeland basin. Phase II is known in Brunei as the

Mid-Miocene Champion System. As in Phase I,these sands are strictly localized in Brunei, andcannot be found anywhere else. Phase III formsthe third and major sand pulse starting with CycleIV, which shaped the sandy shelfal margins inSarawak, Brunei and Sabah.

STRATIGRAPHY AND SEISMICEXPRESSIONS OF SHELF EDGES

Stratigraphic nomenclatures The simplified stratigraphic scheme for NW Borneoused in this study is presented in Table 1, withdetailed description of the “Cycle” and “Stage”concepts in Sarawak and Sabah provided by Doust

(1981) and van Hoorn (1997), respectively. Inaddition, Besems (1992) also gave a gooddescription of the Cycle concept with specialreferences to Cycles I, II and III. A brief summaryon the nomenclature evolution of the Tertiarysediments in NW Borneo is given below, whichbasically reflects increasing area knowledge andthe change in focus of the exploration activities.

Figure 1. Tectonic overview map of NW Borneo from Cullen, 2010. The exact course and significance of theBalabac Line (BAL) and West Baram Line (WBL) remain controversial.


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The stratigraphic subdivision of Tertiary rocks inSarawak and Sabah has evolved through variousphases of nomenclature. During the early stage ofexploration, a large number of local formation

names were used (e.g., Belait Formation; Liechti etal., 1960), which proved to be of limited regionalapplication since this approach is impractical inthe offshore area, where different formations aredifficult to recognize on the basis of lithology. Inaddition, the great thickness (up to 6s TWT or

approximately 7300 m) of the offshore sequencesdoes not allow proper definition for litho-stratigraphical definition due to a lack of wellpenetration. The proliferation of Tertiary formation

names in NW Borneo led to the introduction of aregional subdivision into two major units; aPalaeogene geosynclinal phase, followed by aNeogene regressive phase, the latter beingsubdivided into six (later eight) regressive cycles.

The Cycle concept was first introduced for both

Sarawak and Sabah in the late 1960’s (Geiger,1964; Eckert, 1971). At the basis of this cycle

concept was the recognition of a number of rapid,widespread transgressions within the regressivesequence, which often coincided with periods of“tectonic unrest” in the Baram Delta area. Eachtransgression was considered to correspond to theonset of a new cycle, which ideally is composed of

a shaly base grading upward in a sandy regressivetop. The cycle boundaries were considered to beapproximate time lines and isochronous. However,subsequent drilling showed that the criteria, which

can be used in Sarawak for the recognition of thecycle boundaries, could not be applied in Sabahbecause of the presence there of apparently large,diachronous transgressions and regressions.Consequently, a mixture of units of differentmeaning and magnitude was used, serving as a

correlation tool in rather limited areas (Cycle-equivalent; M, N, O units; South Furious Sands;St. Joseph Sands; West Emerald Sands, etc.). These litho-stratigraphic units have been dated

using a fairly detailed palynological subdivisioninto zones and subzones.

Whereas a detailed pollen zonation is acceptable asa correlation tool within limited areas, it is felt thatits application for regional correlation is quite oftendifficult. This is due to the definition of the pollen

zones in use, which is mainly based on statisticaldeterminations of the relative abundance of certain

types and not on top/bottom occurrences.Furthermore, this relative abundance may beinfluenced by the distance from the coastline.However, recent work by Morley and Morley (2011)has managed to identify the timing of arrival ofspecific floras in Miocene SE Asia. Upland floras

Figure 2. Summary index map showing the location of outcrop locations and seismic offshore examples.


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thrived during sea level low stands, whilstmangroves prospered during high stands in thecoastal areas. Obviously, the scale of sea-levelchanges, being in the order of 20-30 m, must beenseen in the context of the much bigger Borneouplift.

The Stage concept, which recognizes four majorStages (I to IV), separated by unconformities, wasintroduced for Sabah in the early seventies, andsummarized by van Hoorn (1997). The early Mid-Miocene to Pliocene Stage IV sediments are furthersubdivided into seven sub-Stages (IVA – IVG), eachseparated by unconformities or their correlatabledisconformities. These unconformities [BMU (BaseMiocene Unconformity), DRU (Deep RegionalUnconformity), LIU (Lower IntermediateUnconformity), UIU (Upper IntermediateUnconformity), SRU (Shallow RegionalUnconformity), Hor III, Hor II and Hor I] are theresults of both local structural deformation and

regional tilting towards the northwest and/oreustatic sea-level variations. In general, they are

represented by erosional surfaces in the southeastof West Sabah passing into onlap surfaces ordisconformities towards the northwest. However,in detail, the seismic correlation of these stageboundaries between the shelf (Inboard) and thebasinal (Outboard) areas remains problematic.Nevertheless, these unconformities remain the bestmarkers for regional seismic correlation in theInboard area of offshore West Sabah (Lee, 2000,Figure 3).

Both the Cycle and Stage concepts have theirlimitations. The Cycles are found generally definedby diachronous transgressive surfaces and are noteasily recognizable, particularly in deepwaterareas. Therefore within the same cycle, distalsedimentary packages may not be necessarily age-

equivalent to their shelfal and onshorecounterparts, and this hinders the reliable time-stratigraphic correlation of sedimentary sequencesacross different geological provinces. Furthermore,the prograding/retrograding sedimentary packagesassociated with second order sea-level fluctuationswithin the same cycle have not been properlydescribed. The Stage concept on the other hand,suffered from correlation difficulties from shelfal to

deepwater area, also in relation to the recognitionof the unconformities/disconformities there.

The above shortfalls in Cycle and Stage conceptstherefore, warranted a new approach to thesubdivision of Tertiary sediments with theapplication of sequence stratigraphic principles.Recently there is a move towards using the global

sequences of Haq et al. (1988) in the regional studyof the NW Borneo area (e.g., Morisson and Wong,

2003). Nonetheless, acknowledging theirlimitations, we believe that the application of theCycle and Stage concepts remain useful especiallyfor correlating across the shelfal area, wheretectonic uplift of the Inboard area plays a moreprominent role than eustacy in determining the

environments and thus facies of the sedimentarysequences.It is also worth mentioning that in 2007, amonumental study entitled “ChronostratigraphicChart of the Cenozoic and Mesozoic basins ofMalaysia” was published by the Petroleum

Management Unit (PMU), PETRONAS (2007). Inthe chart, the problem of Sabah stages was alsohighlighted. The stages as defined by Bol and Thum (1981) have helped in decades of successfulexploration. But at present, due to expansion ofsections in deepwater exploration, Sabah ’s stratigraphic nomenclature varies amongcompanies and geoscientists. This lack ofuniformity reflects the complexity of Sabah’sstratigraphy and the difficulty in taking litho-stratigraphy from the Inboard area and projectingit offshore. Sabah stages offshore are difficult todefine; the regressive stages typical of deltaicsequences are not always present due to erosionby time transgressive unconformities as mentioned

earlier. Also, similar lithofacies over long periods ofgeologic time make it difficult to differentiate

stages. To help define stratigraphic traps, a moredetailed scheme based on biostratigraphy istherefore warranted and timely produced by PMUto facilitate better communications betweendifferent companies and geoscientists.

Stratigraphic correlationStratigraphic correlation in Sabah offshore areaswas, and remains a daunting task. Essentiallythree approaches have been applied throughoutthe years, and by various operating companies,

with variable success:

Correlation by means of unconformities andapplying the concept of sedimentation cycles; thisstratigraphic approach has worked with somesuccess in the Baram Delta, and somewhat less soin Sabah. Results, however, need to be taken withthe caveat that cyclicity is not always easy toestablish and that certain mapped reservoir unitsmay be of diachronous nature.

A slightly more recent approach spearheaded by

Shell attempted to apply sequence stratigraphybased on global sea-level changes (e.g., Morrisonand Wong, 2003); however this approach faces the

difficulty of applying eustacy in an area which isknown both for rapid changes in subsidence, andtectonic uplift, respectively. For this and otherreasons such as difficulties in seismic correlationfrom mini-basin to mini-basin over structuralhighs, the sea-level curve-based stratigraphy failedto produce reliable results. It turned out to bealmost impossible to map sequence boundaries(SB) and third order sequences (TB sequences) ofHaq et al. (1988) regionally, with the consequence

they were often mis-applied as seismic horizons oninterpretations instead of true sequenceboundaries. By doing so the information that isvested in seismic data was discounted. In anutshell, sea-level changes might have only playeda minor role in shaping


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stratigraphy in the offshore Sabah shelf margin,and should be treated accordingly.

Another approach was to develop localstratigraphy in a given theater, such as the Sabahshelf or the Sabah deepwater. Although suchapproaches lead to practical solutions, it did notresolve correlation of sediment bodies over largedistances. Looking back on some 50 years ofstratigraphy in offshore Sabah, the originalapproach of describing sequences byunconformities (DRU, LIU, etc.) has stood the testof time, whereas the intra-unconformity sequencesencountered might be described best by localparameters. The problem of correlating sedimentsin Sabah also stems from the rather uniquegeology attributed to Borneo Island and thesurrounding offshore. The NW Borneo Foredeepoffers four distinct belts that need to be put inregional context:

The exhumed Rajang/Crocker Basin , formed bymeta-sediments of Upper Cretaceous (KU) to Lower Tertiary (TL) age, in the hinterlands and on theshallow shelf north of Kota Kinabalu.

The Sarawak/Brunei/Sabah Shelf, Cycles IV/V

(Stages IVA-E) strongly inverted in part, and

mainly formed by deltaic sand/claystonesequences. These sequences have been drilled bymany (albeit commonly “old”) exploration wells,but on seismic lack good, correlative reflectors.

The Slope, with only a few well penetrations;these wells here were often abandoned early in thelight of significant overpressure being encountered,and forcing an early well TD; seismic is often poorin these areas too.

The Deepwater, formed by a pile of tectonic

imbricates with turbidite fans and mass transportcomplexes, encountered within the imbricates(“older systems”), as well as enveloping these as

post-tectonic sediments.

Seismic examplesOn the following pages, we discuss various aspectsof the development of the shelf – slope transitionzone or shelf edge in these areas:

In northern Sabah, the Middle to Late Mioceneshelf lay essentially parallel to the present-daycoastline; however there were indentations andoutliers of the shelf edge linked to strike-sliptectonics and clay injection (Figure 4).

Figure 4. Map showing the Stage IVC shelf edge, slope scars and locations of associated slope canyons inNW Sabah. The palaeo-shelf edge ran in parallel to the present-day coastline; however we see local“ anomalies ” caused by strike-slip tectonism as well as clay diapirism. Note the rapid NW progradation to theStage IVD shelf edge. The coloured dots represent points, where the transition from topset facies to foreset

(sigmoidal onlap facies) was picked on seismic.


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The shelf edge remained more or less stationaryduring Stages IVA to IVC (Cycles IV to Mid Cycle V)times (Figure 5).

At the central Sabah edge, distal shelf depositsare often trapped in mini-basins, and the shelfedges are formed by truncation/onlap against clay-cored anticlines (Figure 6).

In the area of the Sabah/Brunei border, themargin is controlled by faults and minor depo-centers (Figure 7).

THE SEDIMENTS IN OUTCROPS

Field and outcrop data complement seismic

observations, and NW Borneo is rich in fresh (un-weathered) outcrops associated with new road cutsand construction sites. In such way a linkbetween the areas of sediment supply, the older(and often reworked) stratigraphy, shelf and

deepwater sediments can be attempted.

Sources of sand The Rajang and Crocker meta-sediments are at thecore of an inverted turbidite basin that formed inKU-TL times under deep marine conditions(Hutchison, 2005). The Crocker appears to beformed by distal fan complexes (Figure 8), notunlike the Rajang Group beds (Kelalalan/BelagaFormation, Figures 9-10).

There are several good onshore outcrop locationswhich enable completion of the picture described

in the previous section. During the Mid-Miocene,the shelf was formed by muddy sediments,generally referred to as Setap Shale (Figure 11).

They are commonly lean in organic matter andcontain minor turbidite sequences, as well as

carbonate shoals (Sibuti Formation). This can leadin places to the development of oyster reefs andmarly mud-wackestone sequences (Simon et al.,2014). The narrow sandy shelf that may haveexisted in Sarawak (but which has never beenfound), was located well in-land some hundreds ofkilometers from the present coastline. In the LongLama area of Sarawak (TM in Figure 2), the SetapShale contains many slumped folds and the

occasional slump block of sandy material (Kessler,2009). In Limbang (Li in Figure 2), outcrops show

a thin-bedded turbidite sequence (Figure 12). Sofar, not a single good oil and gas reservoir hasbeen found in Cycle III deposits.

Sediments of Cycles IV and V (Stages IVA toIVE)Seen from a reservoir standpoint, the Middle toLate Miocene shelfal sands of the Cycles IV/Vsequences look very similar; indications of calcitecementation being seen only at the eastern limit ofthe Sabah shelf. Otherwise the lithologiesencountered are clean sandstone and (often coaly)shale. The first commercial oil field discovered in

shelfal deposits was the Miri Field. In addition topenetrations in many Sabah and Sarawak wells,

the Lower Cycle V (Stage IVA) sequence is wellexposed in coastal outcrops in Sarawak (Figure13).

Figure 5. Seismic profile from the greater South Furious Field area showing the geometries of the shelf edge(orange line) in the interval from Stages IVA-D. The sediments in the syncline between the two clay-cored

highs contain very little sand.


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Figure 7. Portion of a seismic profile through outer shelf deposits near to the Sabah/Brunei border. Theseismic line runs NE-SW slightly obliquely through the Stage IVC (TB 3.1) outer shelf depocenter in the

Kinabalu Field hanging wall block. The Stage IVC sequence (below upper green marker, and down to brokenyellow facies-divide line) reaches here a thickness exceeding 1300 m. Such distal shelf deposits are mostly

fine-grained, and clay content within the gross package exceeds 60 %.

Figure 8.

Originally anchi- metamorphic,but now stronglyweatheredsandstone/shalesequencesbelonging tothe ?EoceneWest Crockerunit qualify asthe most likelycandidate as thesource for Middleto Late Miocenesands on theSabah shelf.


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Figure 9. Distal turbidites of the Belaga Formation, which appear to be chevron-folded, Baram River nearLong Lama. The sand is mostly fine-gained. The folding appears to be mainly the result of compressive

tectonic.

Figure 10. Quartzitic and very hard heterolithic conglomerate, which may have originated as a debris

flow. Top right inset is a sample from the rock face. Scale in cm.


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Figure 11. Middle Miocene sequences (Cycle III, TB 2.2, 2.3) below the Late Miocene are characterizedby mainly shale-dominated outer neritic environments. These occasionally contain thin-bedded Bouma-

type turbidite silt and sandstone beds, as shown here in an outcrop from Kampung Limbang (KL).

Figure 12. Outcrop of gray Setap Shale (~ Sibuti Formation) with two prominent turbidite sandbeds ca. 5 cm and 12 cm thick, respectively, on the old Beluru Road, Bukit Peninjau, in Sarawak.This sequence is typically lean in sand, containing only few isolated, thin-bedded and distalturbidites. Occasional calcareous fossils are found. The Setap Shale underlies fluvio-deltaicsediments of the Lambir Formation, Cycle IV (Stage IVA) in Sarawak.


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Figure 13. Stratigraphic log of measured outcrop section at Entulang showing thetransition from a very fossiliferous Sibuti Formation (after Wannier, 2011, p. 160) to thesandy Lambir Formation [(Lower Cycle V (Stage IVA), Serravallian]. There is an

unconformity at the base of the sand, with a tentative hiatus of 0.5 Ma.


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The reservoir facies in Cycles IV/V (Stages IVA toIVE) can be divided as follows:

Lower coastal plain. On low resolutionseismic, these beds often appear as sheet sands. Inreality and on sub-seismic scale however, there iswidespread channeling, which can lead tounexpected lower reservoir continuity than onewould foresee. This facies is characterized by tidalchannel fills, mouth bar and beach deposits, veryoften rich in peats and coals. Channel sands oftendisplay cross-bedded geometries (Figures 14-16).

Inner to middle shelf deposits arecharacterized by relatively continuous sheet sands,

and grain-size is usually fine; these are stackedwith siltstone and shale packages that can formsealing barriers between sandstone units (Figure17).

Following a rapid transition from the inner

to the outer neritic shelf, the sand content of theCycle IV/Stage IVA interval drops very rapidly; theshelf break can be defined here as the point atwhich topset seismic facies is replaced bysigmoidal onlap.

Figures 18-19 show potential distribution of sandon the NW Borneo shelf during Stage IVA (Cycle VI)and Stage IVC (Mid Cycle V), respectively.

Characterization of reservoirs The presence of reservoir sandstones in NWBorneo hinges on the processes that led to their

formation; this relationship and their propertiescan be seen in Table 2. Dykstra-Parsons

coefficient of permeability variation is a commondescriptor of reservoir heterogeneity. It measures

reservoir uniformity by the dispersion or scatter ofpermeability values. A homogeneous reservoir hasa permeability variation that approaches zero,while an extremely heterogeneous reservoir wouldhave a permeability variation approaching one.

The provenance of sand

Although it was proposed above that the CyclesIV/V (Stages IVA to IVE) sands are essentiallyreworked metamorphics from the Rajang/Crockerhinterlands, the question poses itself from wherethese sand prone clastics came from in the firstplace. According to van Hattum et al. (2013), thereis good evidence, based on heavy mineralassemblages, that the origins of most if not allRajang/Crocker deposits are located in the greaterSchwaner Mountains area of south-westernBorneo. They proposed therefore, that the CrockerFan sandstones were derived from nearby sourcesin Borneo and nearby SE Asia, rather than fromdistant Asian and Himalayan sources. The

Crocker Fan sandstones have a maturecomposition, but their textures and heavy

mineralogy indicate they are first-cycle sandstones,mostly derived from nearby granitic source rocks,with some input of metamorphic, sedimentary andophiolitic material. In the Eocene sandstones,Cretaceous zircons dominate and suggestderivation from granites of the SchwanerMountains of southern Borneo. According to thesame authors, the provenance of the TajauSandstone Member of the Lower Miocene KudatFormation in north Sabah is strikingly differentfrom other Miocene and older sandstones. This

sediment was derived mainly from granitic andhigh-grade metamorphic rocks.

Figure 14.

Eastern slope ofCanada Hill in Miri(Location M), LowerCycle V (StageIVA), with normal

faulting. The rock face shownbelongs to asection of the MiriOil Field that wasuplifted, andexhumed in LatePleistocene-

Holocene time.Some sand layersstill contain traces

of residual oil.


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Figure 15. Upper Cycle IV/Lower Cycle V (Stage IVA) sequence from Bukit Song (Location BS, Lambir Hills,Sarawak) showing a stacked sequence of sandstone and shale layers. Minor channeling is seen within thethick sandstone units. Sands are mostly fine- to medium-grained, but larger pebbles can be found in rare

con lomeratic beds.

Figure 16. A rare cross-bedded conglomeratic bed isseen in Cycle IV deposits at Bukit Song. Theconglomerate pebbles are mainly composed of whitequartz, possibly originating from quartz dykes in the

Rajang Group.

Figure 17. ?Cycle IV-V sequence in Labuan, LocationL, with predominantly fine-grained sandstone

deposited in lenses between continuous claystonebeds. Layered sequences of fine-grained sandstoneand claystone are often interpreted as shelf margindeposits. The sediment composition is beinginvestigated by A/Prof. Dr. Nagarajan, Curtin

University Sarawak.


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No such rocks existed at the surface in Borneo

during the Early Miocene, but potentialmetamorphic sources from an elevated region arepresent on Palawan, to the north of Borneo andcould have supplied sediment to north Sabah. Ifso, this may indicate that the Lower MioceneKudat Formation (usually the deepest formationdrilled in Sabah offshore exploration) has notreceived any recycled clastics from the Crocker,which in turn suggests that the latter had not beenuplifted and exhumed yet.

The provenance of sands and muds of the MioceneSibuti Formation was studied by Nagarajan et al.

(2013), based on the mineralogy, major and traceelement geochemistry data. The X-ray diffraction(XRD) and scanning electron microscopy-energydispersive spectrometry (SEM-EDS) data revealedthat the sandstones and mudstones containabundant in quartz, pyrite, clay, and heavyminerals such as zircon, rutile, and some detritalcassiterite. Elemental ratios such as La/Sc, Th/Sc,Cr/Th, La/Co and Th/Co suggest sediments to bederived from the felsic rocks. Also, the provenancediscrimination diagrams suggest that these clasticsediments are of a recycled continental nature and

are mostly derived from a meta-sedimentarysource (of the Rajang/Crocker Formation).

Discriminant-function diagrams for the tectonicdiscrimination of siliciclastic sediments revealedthat the sediments of Sibuti Formation werederived from a collision zone, which is consistentwith the geology of the study area as described byvan Hattum et al. (2013). However, a turbiditereservoir potential within this sequence couldnever be demonstrated.

HOW MUCH UPLIFT CAN BE ESTABLISHEDFOR THE BORNEO HINTERLAND?

Gravity field and steady-state OceanCirculation Explorer (GOCE) satellite gravity(Figure 20) images show a strong regional anomalyof the Earth’s geoid in SE Asia, pointing to crustal

uplift. Possibly, this area of crust started to risewhen subduction commenced in the LateCretaceous off Java, leading to accretion ofterranes, and thickening of the crust betweenSundaland and Australia (Hall, 2013). Areas ofBorneo as well as others, such as New Guinea and

in particular Sulawesi (pers. comm., Robert Hall)have seen spectacular uplift especially since thePliocene.

Recent research sponsored by JX-Nippon,and carried out by Curtin University Sarawak hasindicated that the Sarawak coastline rose by some75 m in the Miri area (on Miri’s Canada Hill 150m) since the Late Pleistocene, when including andcompensating for the Holocene sea-level rise(Kessler and Jong, 2014a and 2014b). This makesa case for a recent uplift, probably including amuch longer and older component. The recentuplift is dwarfing sea-level changes by a factor of

3:1. The coastline south of Miri is elevated by some

20 m above the current sea-level (Figures 21-22).

Vitrinite samples (VRM 0.42) obtained fromcoaly Pliocene Tukau sediments, now 30 m and 50m above sea-level; suggest that some 600 m ofsediments have been removed during the lastcouple of million years.

A comparative study (vitrinite, seismic andother) on Bukit Enkabang near Marudi (Table 3)concluded that this area saw a Pliocene uplift inthe order of 500 m. From folding considerations, itis commonly assumed that folds and thrusts of

sedimentary basins commonly originate in theshallow subsurface, given it is easier to create folds

and thrusts when the overburden is minimal. Thenature of folds also implies steep dips in the coresections, and smaller dips in the crestal (top)section. This means that a deeply eroded fold-corewill show steeply dipping beds (such as the Tudandome north of Miri, for instance), whilst weak dipswould emphasize a section of the roof, with theimplication that erosi

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