Sp 96 TOC and Abstracts

Dust jacket front:

Background image: modified from Lu and Shipp, Figure 2, page 201.

Upper image: from Posamentier and Martinsen, Figure 10C, page 16.

Lower image: modified from Posamentier and Martinsen, Figure 32E, page 30.

Dust jacket back:

Background image: modified from Lu and Shipp, Figure 2, page 201.

Upper figure: Modified from Algar et al., Figure 4, page 356.

Middle figure: Modified from Algar et al., Figure 5A, page 357.

Lower photo: from Posamentier and Martinsen, Figure 4, page 11.

Title page:

Photograph from King et al., Figure 7A, page 319.

Hard cover gold stamp:

Figure modified from Posamentier and Martinsen, Figure 3, page 10.

Mass-Transport Deposits in Deepwater Settings

R. Craig Shipp, Paul Weimer, and Henry W. Posamentier, Editors

CONTENTS

Overviews

Mass-transport deposits in deepwater settings: an introductionR. CRAIG SHIPP, PAUL WEIMER, AND HENRY W. POSAMENTIER ................................................................................................. 3

The character and genesis of submarine mass-transport deposits: insights from outcrop and 3D seismic dataHENRY W. POSAMENTIER, AND OLE J. MARTINSEN ......................................................................................................................... 7

Interplay of mass-transport and turbidite-system deposits in different active tectonic andpassive continental margin settings: external and local controlling factorsC. HANS NELSON, CARLOTA ESCUTIA, JOHN E. DAMUTH, AND DAVID C. TWICHELL, JR. ............................................... 39

Seafloor and Near-Subsurface Studies

Algerian margin sedimentation patterns (Algiers area, southwestern Mediterranean)GABRIELA DAN-UNTERSEH, BRUNO SAVOYE, VIRGINIE GAULLIER, ANTONIO CATTANEO,JACQUES DEVERCHERE, KARIM YELLES, AND THE MARADJA 2003 TEAM ............................................................................. 69

Upper Quaternary seafloor mass-transport deposits at the base of slope, offshore Niger Delta, deepwater NigeriaJASON P. SUTTON, AND ROBERT M. MITCHUM, JR. .......................................................................................................................... 85

Characterization of mass-transport deposits on a Pliocene siliciclastic continental slope, northwestern South China SeaMANGZHENG ZHU, STEPHAN GRAHAM, AND TIM MCHARGUE ............................................................................................. 111

3-D Seismic stratigraphic interpretation of Quaternary mass-transport deposits in the Mensa andThunder Horse intraslope basins, Mississippi Canyon, northern deep Gulf of Mexico, U.S.A.JORGE DIAZ, PAUL WEIMER, RENAUD BOUROULLEC, AND GEOFF DORN ........................................................................... 127

The Barrington submarine mass-transport deposit, western Scotian Slope, CanadaDAVID C. MOSHER, AND D. CALVIN CAMPBELL............................................................................................................................ 151

Late Neogene to Recent seafloor instability on the deep Pacific margin of the Antarctic PeninsulaVALENTINA VOLPI, DAVID AMBLAS, ANGELO CAMERLENGHI, MIQUEL CANALS,MICHELE REBESCO, AND ROGER URGELES ..................................................................................................................................... 161

Geohazards Studies

Processes of submarine slope failure and fluid migration on the Ebro Continental Margin:implications for offshore exploration and developmentJOSE FREY-MARTÍNEZ, CLAUDIA BERTONI, JEAN GÉRARD, AND HUGO MATÍAS.............................................................. 181

Impact of a large mass-transport deposit on a field development in the upper slopeof southwestern Sabah, Malaysia, offshore northwest BorneoHONGBO LU, AND R. CRAIG SHIPP ..................................................................................................................................................... 199

Descriptive Outcrop Studies

Stratal architecture and temporal evolution of a passive margin mass-transport deposit,Neoproterozoic Isaac Formation, Cariboo Mountains, British Columbia, CanadaR.W.C. ARNOTT, K. WALLACE, AND J. LAURIN ............................................................................................................................... 221

Submarine mass-transport deposits of the Permian Cutoff Formation, West Texas, U.S.A.: internal architectureand controls on overlying reservoir sand depositionROBERT AMERMAN, ERIC P. NELSON, MICHAEL H. GARDNER, AND BRUCE TRUDGILL ................................................. 235

Mass-transport deposits in the upper Paleocene Chicontepec Formation, MexicoSTEPHEN P.J. COSSEY ............................................................................................................................................................................ 269

Heterogeneity of internal structures in a mass-transport deposit, Upper Cretaceous to PaleoceneAkkeshi Formation, Hokkaido Island, northern JapanHAJIME NARUSE, AND MAKOTO OTSUBO ....................................................................................................................................... 279

Integrated Outcrops and Subsurface Studies

Mass-transport deposits: combining outcrop studies and seismic forward modeling to understandlithofacies distributions, deformation, and their seismic stratigraphic expressionMASON DYKSTRA, KATERINA GARYFALOU, VANESSA KERTZNUS, BEN KNELLER, JUAN PABLO MILANA, MATTEO MOLINARO, MAGDALENA SZUMAN, AND PHILIP THOMPSON .............................. 293

Outcrop and seismic examples of mass-transport deposits from a Late Miocene deep-water succession,Taranaki Basin, New ZealandPETER R. KING, BRADLEY R. ILG, MALCOLM ARNOT, GREG H. BROWNE, LORNA J. STRACHAN,MARTIN CRUNDWELL, AND KRISTIAN HELLE ............................................................................................................................... 311

Reservoir Studies

Mass-transport deposits of the deepwater northwestern Borneo margin (Malaysia)—characterization fromseismic-reflection, borehole, and core data with implications for hydrocarbon exploration and exploitationSAM ALGAR, CHRIS MILTON, HYWEL UPSHALL, JON ROESTENBURG, AND PAUL CREVELLO ..................................... 351

Lithofacies analysis and stratigraphic architecture of a deep-water carbonate debris apron: Lower Cretaceous(latest Aptian to latest Albian) Tamabra Formation, Poza Rica Field Area, MexicoROBERT G. LOUCKS, CHARLES KERANS, XAVIER JANSON, AND M. ALFREDO MARHX ROJANO .................................. 367

Reservoir characterization of sand-prone mass-transport deposits within slope canyonsLAWRENCE D. MECKEL, III, MATTHEW ANGELATOS, JOS BONNIE, RODERICK MCGARVA,TONY ALMOND, NEIL MARSHALL, LAURENT BOURDON, AND KAREN AURISCH ............................................................ 391

Reservoir characteristics and classification of sand-prone submarine mass-transport depositsLAWRENCE D. MECKEL, III .................................................................................................................................................................. 423

Topical Studies

Deformation versus deposition of sediment waves in the Bismarck Sea, Papua New GuineaGARY HOFFMANN, ELI SILVER, SIMON DAY, NEAL DRISCOLL, AND DANIEL ORANGE .................................................. 455

Biostratigraphy of an upper Miocene mass-transport deposit on Demerara Rise, northern South American marginWESLEY C. INGRAM, DAVID C. MOSHER, AND SHERWOOD W. WISE, JR. ............................................................................... 475

Properties of mass-transport deposits as inferred from dynamic modeling of subaqueous mass wasting: a short reviewFABIO V. DE BLASIO, AND ANDERS ELVERHØI .............................................................................................................................. 499

Hinlopen–Yermak Landslide, Arctic Ocean—Geomorphology, landslide dynamics, and tsunami simulationsMAARTEN VANNESTE, CARL B. HARBITZ, FABIO V. DE BLASIO, SYLFEST GLIMSDAL,JÜRGEN MIENERT, AND ANDERS ELVERHØI .................................................................................................................................. 509

THE CHARACTER AND GENESIS OF SUBMARINE MASS‐TRANSPORT DEPOSITS: INSIGHTS FROM OUTCROP AND 3D SEISMIC DATA

HENRY W. POSAMENTIER

Chevron Energy Technology Company, 1500 Louisiana Street, Houston, Texas 77002, U.S.A. e‐mail: [email protected]

AND

OLE J. MARTINSEN StatoilHydro Research, P.O. Box 7200, N‐5020 Bergen, Norway

e‐mail: [email protected] ABSTRACT: Extensive deep‐water mass‐transport deposits are observed in both slope and basin‐floor settings. A detailed understanding of mass‐transport deposits, in terms of emplacement processes, depositional products, and their stratigraphic and geographic distribution, is vital because they can constitute a significant portion of the stratigraphic section in deep‐water settings. In addition, mass‐transport deposits can play a significant role in hydrocarbon exploration, inasmuch as they can constitute seal, reservoir, and possibly source facies under the right circumstances. Different data types bring to light different aspects of mass‐transport deposits. This paper focuses on insights derived from seismic and outcrop data. Overall geometries and architecture of mass‐transport deposits are readily observable in 3D seismic data; however, features below seismic resolution that are vital for process and lithologic understanding need to be observed in outcrop. Integrating observations across a broad range of scales by linking seismic and outcrop observations constitutes an effective way of improving our understanding of when and where mass‐transport deposits are likely to form. In addition, this linkage sheds light on details of internal architecture that commonly characterizes these deposits. Mass‐transport deposits can comprise sheets, lobes, and channel fills, and can reach 150 m or more in thickness. Greater thicknesses are observed where successive flows are amalgamated. This paper documents both internal architectural or stratigraphic as well as external geomorphic attributes of such deposits, as expressed in outcrop and imaged by 3D seismic data. Recognition of mass‐transport deposits in outcrop is based on identification of bedding deformed by synsedimentary processes, with deformation ranging from minimal redistribution of large slide blocks to complete disaggregation typical of debris‐flow deposits. On seismic data, mass‐transport deposits can be recognized by certain geomorphologic as well as stratigraphic distinguishing characteristics: basal linear grooved and scoured surfaces, hummocky relief at the top, and internal chaotic to transparent seismic facies, with internal thrust faulting common.

INTERPLAY OF MASS‐TRANSPORT AND TURBIDITE‐SYSTEM DEPOSITS IN DIFFERENT ACTIVE TECTONIC AND PASSIVE CONTINENTAL MARGIN SETTINGS: EXTERNAL AND LOCAL CONTROLLING FACTORS

C. HANS NELSON Instituto Andaluz de Ciencias de la Tierra, CSIC–University of Granada, Granada, 18002, Spain

e‐mail: [email protected]

CARLOTA ESCUTIA Instituto Andaluz de Ciencias de la Tierra, CSIC–University of Granada, Granada, 18002, Spain


JOHN E. DAMUTH Department of Earth and Environmental Sciences, University of Texas at Arlington,

P.O. Box 19049, Arlington, Texas 76019‐0049, U.S.A. e‐mail: damuth @uta.edu

AND

DAVID C. TWICHELL, JR. U.S. Geological Survey, 384 Woods Hole Road, Quissett Campus, Woods Hole, Massachusetts 02543‐

1598, U.S.A. e‐mail: [email protected]

ABSTRACT: The volume and interplay of mass‐transport (MTD) and turbidite‐system deposits varies on different continental margins depending on local and external controls such as active‐margin or passive‐margin tectonic setting and climatic and/or sea‐level change. Erosion and breaching of local grabens at the shelf edge of the southern Bering Sea produce giant, gullied canyons and MTD sheets that dominate the basin‐floor deposition and disrupt development of turbidite systems. In contrast, external controls of great earthquakes (> 8 Mw) along the Pacific active tectonic continental margins of Cascadia and northern California cause seismic strengthening of the sediment, which results in minor MTDs compared to turbidite‐system deposits. Messinian desiccation of the Mediterranean Sea caused a deeply eroded Ebro subaerial canyon and an unstable central segment with an MTD sheet, whereas other stable Ebro margin segments have only turbidite systems. In the northern Gulf of Mexico, the delta‐fed Mississippi Fan and intraslope mini‐basins contain MTDs and turbidites that are equally intermixed from the largest scales with MTD sheets hundreds of kilometers long to the smallest scales with beds centimeters thick. In the Antarctic Wilkes Land margin, global climate cooling caused a late Oligocene to middle Miocene time of temperate continental ice sheets that resulted in massive deposition of MTDs on the margin, whereas later polar ice sheets favored development of turbidite systems. Our case studies provide the following new insights: (1) MTDs can dominate entire margins, dominate segments of a margin, be equally mixed with turbidites, or dominate a margin during some geologic times and not others; (2) on active tectonic margins with great earthquakes, the maximum run‐out distances of MTD sheets across abyssal‐basin floors are an order of magnitude less (~ 100 km) than on passive‐margin settings (~ 1000 km), and the volumes of MTDs are limited on the abyssal sea floor along active margins; (3) where the most precise radiocarbon ages are available, major MTD episodes of deposition are correlated with the most rapid falls or rises of sea level; (4) gullied canyons feeding MTD sheets have irregular and steep axial gradients (5–9°), whereas canyons feeding turbidite systems have a regular graded profile and less steep gradients (1 to 5°). Our examples of MTD and turbidite systems provide analogues to help interpret ancient systems.

ALGERIAN MARGIN SEDIMENTATION PATTERNS (ALGIERS AREA, SOUTHWESTERN MEDITERRANEAN)

GABRIELA DAN‐UNTERSEH IFREMER, Géosciences Marines, Laboratoire Environnements Sédimentaires, Plouzané, France

AND Université de Bretagne Occidentale, IUEM‐CNRS UMR6538, 29280 Plouzané, France

[email protected]

BRUNO SAVOYE (DECEASED)

VIRGINIE GAULLIER LEGEM, Université de Perpignan, 66860 Perpignan, France

ANTONIO CATTANEO

IFREMER, Géosciences Marines, Laboratoire Environnements Sédimentaires, Plouzané, France

JACQUES DEVERCHERE Université de Bretagne Occidentale, IUEM‐CNRS UMR6538, 29280 Plouzané, France

KARIM YELLES

CRAAG, Centre de Recherche en Astronomie, Astrophysique et Géophysique, Bouzaréah, Alger, Algérie

AND

MARADJA 2003 TEAM Abstract: The present study provides an overview of recent sedimentation patterns on the central Algerian continental margin. Recent sedimentation patterns were assessed from morphological analysis, which is based on swath bathymetry and echo‐facies mapping. It appears that sedimentation along the Algerian margin is controlled by two processes: (1) gravity‐induced processes, including both masstransport deposits and turbidity currents, and (2) hemipelagic sedimentation. Mass‐transport deposits occur on the Algerian margin at the canyon heads and flanks, in the interfluve areas between canyons, along the seafloor escarpments, and on the flanks of salt diapirs. Masstransport deposits (MTDs) sampled by coring consist of a variety of soft and hard mud‐clast conglomerate and turbidite deposits. MTDs are mostly localized at the toes of steep slopes, where thrust faults were previously identified and mapped. Analysis of the spatial distribution of MTDs and their recurrence in time help reconstruct the main predisposing factors and triggering mechanisms, and evaluate their impact on evolution of the Algerian margin.

UPPER QUATERNARY SEAFLOOR MASS‐TRANSPORT DEPOSITS AT THE BASE OF SLOPE, OFFSHORE NIGER DELTA, DEEPWATER NIGERIA

JASON P. SUTTON

RWE Dea UK, 90 High Holborn, London WC1V 6LJ, U.K. e‐mail: [email protected]

AND

ROBERT M. MITCHUM, JR. Chevron Corporation, 1600 Smith Street, Houston, Texas, 77002, U.S.A.

e‐mail: [email protected] ABSTRACT: Deepwater mass‐transport deposits (MTDs) are associated with Upper Quaternary seafloor leveed‐channel complexes at the mouth of a large canyon at the base of slope of the offshore Niger delta. They make excellent analogs for interpreting older subsurface features and reservoirs, and for geohazard analysis. These leveed‐channel complexes and mass‐transport deposits are assessed within a 3D seismic survey, using detailed images of seafloor maps and stratal surfaces, artificially digitally colored, and vertically exaggerated to create optimal imaging. A large canyon head incises the present‐day shelf margin of the Niger delta and traverses down the upper and lower slope for 45 km towards the southeast. At the canyon mouth, a large apron of leveed‐channel complexes covers the slope and basin plain for a distance of 30 km within the seismic survey. Large sediment waves occur on outer levees of channel bends, attaining heights of 200 m. In some areas, synclinal limbs of individual sediment waves have been deformed by numerous rotated blocks along small listric faults to form small mappable MTDs. Other mass‐transport deposits occur associated with and above the leveed‐channel complexes. Lengths of the MTDs range from 1 km to over 16 km, and thicknesses commonly range from 100 m to 200 m. Headward escarpments are well imaged in both map and cross‐section views. Proximal facies of the MTDs includes rotated blocks and large angular glide blocks. These pass distally into smaller glide blocks and chaotic seismic facies inferred to be debrites. Intermediate parts of the MTDs have longitudinal linear features parallel to inferred flow direction. Distal patterns consist of transverse compressive ridges. Other MTDs too large to be completely imaged within the 3D survey show internal facies, consisting of large angular glide blocks in a matrix of seismically visible smaller blocks and chaotic facies inferred to be debrites. Multiple causes of MDTs in this area are probable. In possible order of importance, these include tilting and oversteepening of sediments because of tectonic uplift, high sedimentation rates at the mouth of the canyon, and eustatic falls of sea level.

CHARACTERIZATION OF MASS‐TRANSPORT DEPOSITS ON A PLIOCENE SILICICLASTIC CONTINENTAL SLOPE, NORTHWESTERN SOUTH CHINA SEA

MANGZHENG ZHU

Chevron Corporation, 6001 Bollinger Canyon Road, D 1236, San Ramon, California 94583, U.S.A. Present address: NEOS GeoSolutions, Inc., 6201 Stoneridge Mall Road, Suite 450, Pleasanton, California

94568 U.S.A. e‐mail: [email protected]

STEPHAN GRAHAM

Stanford University, Department of Geological and Environmental Sciences, Braun Hall, GES Building 320, Room 118, Stanford, California 94305, U.S.A.


AND

TIM MCHARGUE Stanford University, Department of Geological and Environmental Sciences, Braun Hall,

GES Building 320, Stanford, California 94305, U.S.A. e‐mail: [email protected]

ABSTRACT: The characteristics, evolutionary history, and triggering mechanisms of successive siliciclastic mass‐transport deposits (MTDs) of late Cenozoic age on the northwestern South China Sea margin were studied using borehole and 2D/3D reflection seismic data. Multiple mass‐transport deposits of various scales and morphologies formed from Pliocene to Holocene time in high‐slope‐gradient and high‐sedimentation‐rate parts of the Qiongdongnan and Yinggehai basins. In plan view, MTDs documented by 3D seismic data, deposited between 3 and 2 Ma, are 1 to 11 km wide and 4 to 29 km long. Two seismic geomorphologic characteristics of a typical MTD comprise a basal surface and displaced masses of sediments. Internal seismic facies of the displaced mass consist of extensional wedge facies in upslope areas, thrusted facies in intermediate areas, and chaotic or mounded facies in distal downslope areas. These MTDs likely were triggered by a combination of mechanisms. Seafloor oversteepening, rapid accumulation of thick sedimentary deposits, overpressure, and a tectonically active basin setting provide a background favoring formation of MTDs. Additionally, seismicity, abrupt increase of sedimentation rates, rapid slope progradation, and release of gas contributed to triggering mass‐transport deposition in the study area.

3‐D SEISMIC STRATIGRAPHIC INTERPRETATION OF QUATERNARY MASSTRANSPORT DEPOSITS IN THE MENSA AND THUNDER HORSE INTRASLOPE BASINS, MISSISSIPPI CANYON, NORTHERN DEEP GULF OF

MEXICO, U.S.A.

JORGE DIAZ Saudi Aramco, P.O. Box 1142, Dhahran 31311, Saudi Arabia

PAUL WEIMER

Energy and Minerals Applied Research Center, Department of Geological Sciences, University of Colorado, Boulder, Colorado 80309‐0399, U.S.A.


RENAUD BOUROULLEC Energy and Minerals Applied Research Center, Department of Geological Sciences,

University of Colorado, Boulder, Colorado 80309‐0399, U.S.A.

AND

GEOFF DORN TerrraSpark, 2525 Arapahoe Ave, Unit E4 PMB 544, Boulder, Colorado 80302‐6746, U.S.A.

ABSTRACT: The stratigraphic evolution of the Quaternary mass‐transport deposits (MTDs) in the Mensa and Thunder Horse intraslope basins, Mississippi Canyon, northern deep Gulf of Mexico, was interpreted based on based on 378 square miles (970 square km) of 3‐D seismic data in water depths ranging from 5300 to 6500 feet (1617 to 1983 m). Seven depositional sequences were defined in the study area between 1.3 Ma to the present. Allochthonous salt systems had bathymetric expression and influenced sediment thickness and location of depositional systems. Six MTDs are present in five of the depositional sequences. MTDs overlie erosional boundaries—up to 30 m of the underlying section has been eroded at the base of the deposits. These deposits consist primarily of chaotic, rotated, and thrusted seismic reflections. They vary in size and areal distribution from elongated to more equidimensional. The oldest MTD is in sequence 1, overlies the 1.3 Ma condensed section, and underlies a series of five east‐trending channels. This MTD has an easterly trend and represents the initial deposition after a major reorganization of the slope system. In the underlying Miocene–lower Pleistocene sequences, channels trended from the northwest to southeast. Sequences 2 and 3 consist of seven additional channels that trend primarily from west to east. The second MTD is present in sequence 3, trends to the southeast, and truncates four channels. A series of stacked condensed sections (ca. 0.6 to 0.08 Ma) form a thin unit and separate sequences 3 and 4. Sequence 4 consists primarily of hemipelagic and overbank deposits. Four MTDs are present in the sequences 5–7. Multiple sets of these deposits have channelized into and stacked on one another. These MTDs appear to have been sourced primarily from the west, similar to the channels in the underlying sequences. This case study illustrates the many variations in MTDs that are present in the same intraslope setting. These variations can occur in their size, shape, thickness, seismic facies, the amount of erosion at their base, and their timing of formation within different positions of sea level.

THE BARRINGTON SUBMARINE MASS‐TRANSPORT DEPOSIT, WESTERN SCOTIAN SLOPE, CANADA

DAVID C. MOSHER Natural Resources Canada, Geological Survey of Canada – Atlantic, 1 Challenger Dr.,

Dartmouth, Nova Scotia, B2Y 4A2, Canada e‐mail: [email protected]

AND

D. CALVIN CAMPBELL Natural Resources Canada, Geological Survey of Canada – Atlantic, 1 Challenger Dr.,

Dartmouth, Nova Scotia, B2Y 4A2, Canada e‐mail: [email protected]

ABSTRACT: A large submarine‐slide deposit from the western Scotian Slope off eastern Canada was imaged on a 3D seismic reflection dataset in the Barrington exploration block. The mass‐ transport deposit (MTD) forms a tongue‐shaped body that is 25 km long and 8 km wide, with a run‐out distance from the headscarp of 41.5 km and a total volume of 12.5 km3. In profile, it consists of a chaotic seismic facies. This facies forms a highly rugose top surface morphology, suggesting that the flow consisted of an abundance of intact angular blocks. Its base reveals evidence of erosion typical of submarine MTDs, with linear downslope‐trending gouges and excavation of a pit 50‐m‐deep. The source area and headscarp of the Barrington MTD are somewhat obscured by postdepositional erosion. Additionally, high‐resolution seismic profiles show that the deposit is draped by approximately 30 m of late Pleistocene and Holocene sediment, providing an age estimate of 30 ka for the failure. Despite this drape, the modern seafloor above the MTD still has a highly rugose morphology, echoing the top surface of the deposit. Seismic profile data show a series of stacked MTDs underlying the Barrington MTD, suggesting that mass‐failure recurrence is common on geologic time scales. Although it is difficult to attribute mass‐failure triggering mechanisms, high sedimentation rates due to proximal shelf glaciers and intense erosion causing oversteepening, and likely established preconditions for instability. Local seismicity, possibly a result of glacial rebound, is the most probable initiating factor.

LATE NEOGENE TO RECENT SEAFLOOR INSTABILITY ON THE DEEP PACIFIC MARGIN OF THE ANTARCTIC PENINSULA

VALENTINA VOLPI Istituto Nazionale di Oceanografia e di Geofisica Sperimentale, Borgo Grotta Gigante, 42/C, 34010

Sgonico (TS), Italy e‐mail: [email protected]

DAVID AMBLAS GRC Geociències Marines, Dept. d’Estratigrafia, Paleontologia i Geociències Marines, Universitat de

Barcelona, C/Martí i Franques, s/n, Campus de Pedralbes, E‐08028 Barcelona, Spain e‐mail: [email protected]

ANGELO CAMERLENGHI ICREA and Depart. D’Estratigrafia, P. y. Geosciènces Marines Universitat de Barcelona, C/Martì i

Franques, s/n, E‐08028 Barcelona, Spain e‐mail: [email protected]

MIQUEL CANALS GRC Geociències Marines, Dept. d’Estratigrafia, Paleontologia i Geociències Marines, Universitat de

Barcelona, C/Martí i Franques, s/n, Campus de Pedralbes, E‐08028 Barcelona, Spain e‐mail: [email protected]

MICHELE REBESCO Istituto Nazionale di Oceanografia e di Geofisica Sperimentale, Borgo Grotta Gigante, 42/C, 34010

Sgonico (TS), Italy e‐mail: [email protected]

AND

ROGER URGELES Institut de Ciencies del Mar, CSIC, Passeig Maritim de la Barceloneta, 37‐49, 08003 Barcelona, Spain

e‐mail: [email protected] ABSTRACT: Sediment mass transport in the Pacific margin of the Antarctic Peninsula is strongly influenced by its peculiar tectonic and sedimentary evolution. Analysis of swath bathymetry and multichannel seismic reflection data shows that this setting reflects the passage from an active to a passive margin, and the transition from river‐dominated to glacier‐dominated sedimentation. Only contouritic sedimentation persisted throughout the late Neogene on the continental rise, while rapid progradation of steep wedges composed of glacial diamicton occurs on the slope. Gravitational instability and mass‐transport processes, which occur on the continental rise, appear to relate to physical properties of contourite sediments deposited in this high‐latitude setting. Other than minor erosional gullies on the upper slope, there is no evidence of major incisions such as channels, canyons, or slide scars on a steep continental slope (averages 13°). This situation results from high shear strength of the slope‐forming diamicton delivered by grounded ice sheets. Short‐run‐out mass failures were the main sediment transport process to the slope. Turbidity currents, most likely originated by downslope evolution of mass flows, were able to generate large deep‐sea channel systems at the base of the continental slope.

On the continental rise, relatively good sorting and a high accumulation rate of sediments forming sediment drifts favored slope failure even on gentle slopes. Coalescent headscarps that form the drift crest were produced by undercutting of steeper flanks of drifts. This process formed the walls of turbidity‐current channels, flowing in low‐relief areas between drifts. Failure along stratal weak layers on the gentle sides of sediment drifts produced either relatively small, concave slide scars in the margin‐proximal drift or long, rectilinear scars in distal locations.

PROCESSES OF SUBMARINE SLOPE FAILURE AND FLUID MIGRATION ON THE EBRO CONTINENTAL MARGIN: IMPLICATIONS FOR OFFSHORE EXPLORATION AND DEVELOPMENT

JOSE FREY‐MARTÍNEZ

Statoil ASA, TNE SST GGP RGE, NO‐4035, Stavanger, Norway e‐mail: [email protected]

CLAUDIA BERTONI

Repsol, Exploration New Ventures, Pº Castellana, 280, 4th Floor, Madrid, 28046, Spain e‐mail: [email protected]

JEAN GÉRARD

Repsol, Disciplinas Geológicas, Pº Castellana, 280, 1st Floor, Madrid, 28046, Spain e‐mail: [email protected]

AND

HUGO MATÍAS Repsol, Exploration Spain, Pº Castellana, 280, 1st Floor, Madrid, 28046, Spain

e‐mail: [email protected] ABSTRACT: This paper uses three‐dimensional seismic data to investigate the typologies, genetics, and mechanisms of soft‐sediment deformational processes on the Ebro Continental Margin (offshore northeastern Spain). The study focuses on the two major types of soft‐sediment deformation in the region: slope failure and fluid‐escape structures. Such processes have operated almost continuously throughout the post‐Pleistocene history of the Ebro Continental Margin, and have played a critical role in its overall evolution and construction. This study shows that vertical stacking patterns of submarine canyons create preferential pathways for fluid migration and slope failure. In these areas, three‐dimensional seismic analysis reveals a potential cause‐and‐effect relationship between focused fluid migration and repeated slope failure. The proposed model is that focused fluid flow from sands within stacked submarine canyons leads to overpressure generation and reduction of sediment shear strength, making sediment susceptible to failure. The presence of a widespread region of fluid‐escape structures and slope failures on the Ebro Continental Margin has important implications for offshore facilities. The relatively high resolution provided by the seismic data has been sufficient to be used for a geohazard assessment study, aimed at exploratory well design and field development. The results from this study have led to a detailed program of seafloor and near‐surface evaluation over a proposed area in the area.

IMPACT OF A LARGE MASS‐TRANSPORT DEPOSIT ON A FIELD DEVELOPMENT IN THE UPPER SLOPE OF SOUTHWESTERN SABAH, MALAYSIA, OFFSHORE NORTHWEST BORNEO

HONGBO LU

Shell Exploration and Production Company, HOU‐EPC A2020, 150 North Dairy Ashford, Houston, Texas 77079, U.S.A.


AND

R. CRAIG SHIPP Shell International Exploration and Production Incorporated, 200 North Dairy Ashford, Houston,

Texas 77079, U.S.A. e‐mail: [email protected]

ABSTRACT: Offshore of northwest Borneo, the occurrence of distinct submarine mass failures on the upper continental slope poses a substantial challenge to deepwater operations for the energy industry. These features are part of a complex of mass‐transport deposits (MTDs) that occur in the near‐surface interval across most of the upper continental slope, including a large area undergoing field development for hydrocarbon production. In the study area, the shallowest and most prominent feature discernible on conventional 3D seismic data is MTD 1, which has a profound influence on the present‐day seafloor topography. This feature has a distinctive fan‐like outline in plan view, a maximum strike dimension of approximately 6 mi (10 km), a dip extent up to 24 mi (40 km), and a maximum thickness up to 570 ft (176 m). The fan‐like external form and the presence of a dip‐oriented erosional keel suggest that the depositional process was a less coherent debris flow, with little to no original internal stratigraphy preserved. The less coherent nature of this feature is further supported by a key observation that this MTD overran an area of substantial high bathymetric relief, which is located in the area considered for a field development. Locally overlying MTD 1 are a series of younger near‐seafloor features, termed “canyon‐to‐fairway” corridors that display a confined updip to less confined downdip plan‐view morphology. These unique features locally erode and smooth the rugose top surface of the near‐surface MTD 1 and can be interbedded with the lower intervals of the usually overlying draped sediments. Development of these late Pleistocene canyon‐to‐fairway corridors suggests that these features probably formed during a period of sea‐level fall or at a lowstand. A blanket of three distinct intervals of draped sediments cap this entire sequence, composed mostly of muddy turbidites grading upward into hemipelagic deposits. The present hummocky seafloor topography mimics the rugose top surface of the shallowly buried MTD 1, except along its northeast lateral margin and where smoothed by canyon‐to‐fairway corridors. Internally within MTD 1, physical properties probably vary substantially both laterally and vertically, because draped sediments, turbidites, and occasional channelized sediments were incorporated in the failed matrix of this feature. Some of the geohazards, potentially affecting a field development, are a direct a result of the ubiquitous occurrence of MTD 1 in the study area. These potential geohazards include local steep slopes, seafloor scarps, and variable near‐seafloor soil conditions. Understanding the impact of each of these potential geohazards, caused primarily by the presence of MTD 1, on a field development is vital input for selection of production well‐site locations and placement of subsea infrastructure.

STRATAL ARCHITECTURE AND TEMPORAL EVOLUTION OF A PASSIVE MARGIN MASS‐TRANSPORT DEPOSIT, NEOPROTEROZOIC ISAAC FORMATION, CARIBOO MOUNTAINS, BRITISH COLUMBIA, CANADA

R.W.C. ARNOTT

Department of Earth Sciences, University of Ottawa,140 Louis Pasteur Pvt., Ottawa, Ontario, K1N 6N5, Canada


K. WALLACE Department of Earth Sciences, University of Ottawa,140 Louis Pasteur Pvt., Ottawa, Ontario, K1N 6N5,

Canada Present address: Imperial Oil Ltd., 237 4 Avenue SW, Calgary, Alberta T2P 3M9, Canada

AND

J. LAURIN Department of Earth Sciences, University of Ottawa,140 Louis Pasteur Pvt., Ottawa, Ontario, K1N 6N5,

Canada ABSTRACT: Deep‐marine strata of the Windermere Supergroup, which currently are exposed in an area over 35,000 km2 in the southern Canadian Cordillera, were deposited on the passive margin of Neoproterozoic western North America. In the Isaac Formation at the Castle Creek study area, stratigraphic evidence of slope instability occurs as mass‐movement (slump and slide) and cohesive‐debris‐flow deposits that crop out locally through the 1.5‐km‐thick succession. These deposits are particularly common in a mass‐transport deposit (MTD) up to 110 m thick that occurs sandwiched between two major channel complexes. Interstratified within these deposits are common coarse‐grained channel fills that preferentially infilled irregular topography on the seafloor. In many instances, this irregular topography was most probably related to earlier emplacement of debris‐flow and slump and slide deposits. Important stratigraphic characteristics in this succession suggest that this particular MTD represents a major change in the nature of sediment supply and transport and depositional processes within the basin. These changes are interpreted to be controlled principally by changes of relative sea level, which had a first‐order control on sediment supply, sediment caliber, and sediment composition to the slope and more distal basin floor.

SUBMARINE MASS‐TRANSPORT DEPOSITS OF THE PERMIAN CUTOFF FORMATION, WEST TEXAS, U.S.A.: INTERNAL ARCHITECTURE AND CONTROLS ON OVERLYING RESERVOIR SAND DEPOSITION

ROBERT AMERMAN Department of Geology and Geological Engineering, Colorado School of Mines, 1516 Illinois Street,

Golden, Colorado 80401, U.S.A. Present address: Noble Energy, Inc., 1625 Broadway, Suite 2200, Denver, Colorado 80202, U.S.A.

email: [email protected]

ERIC P. NELSON Department of Geology and Geological Engineering, Colorado School of Mines, 1516 Illinois Street,

Golden, Colorado 80401, U.S.A. e‐mail: [email protected]

MICHAEL H. GARDNER Department of Earth Sciences, Montana State University, P.O. Box 173480. Bozeman, Montana 59717,

U.S.A. e‐mail: [email protected]

AND

BRUCE TRUDGILL Department of Geology and Geological Engineering, Colorado School of Mines, 1516 Illinois Street,

Golden, Colorado 80401, U.S.A. e‐mail: [email protected]

ABSTRACT: The Williams Ranch Member of the upper Cutoff Formation in the Guadalupe and Delaware Mountains, west Texas, U.S.A., consists of six offlapping lithologic units. The deposits formed during carbonate turbidite deposition across a drowned Early Permian carbonate platform. They have an areal extent of more than 20,000 km2 and reach a maximum thickness of at least 113 m. At the terminal margin of the older platform, the carbonate turbidites were partially redistributed by mass‐transport events (MTEs) onto the slope and basin floor. Deposits formed during individual mass‐transport events (MTE bodies) comprise the bulk of the Williams Ranch Member basinward from the drowned margin for at least 28 km along a transect oblique to depositional dip. MTE bodies are interbedded with undeformed carbonate turbidites and contain soft‐sediment folds, faults, and extensional and shortening lineations, as well as termination surfaces (beds terminated from above and/or below). Turbidite deposition and subsequent mass transport caused general basinward thickening of the Williams Ranch Member from the drowned margin, where the Cutoff Formation is missing, to the basin floor.

Deposition responded to, and modified, inherited bathymetric relief. Compared to isopach thins, isopach thicks formed in bathymetric lows and locally formed bathymetric highs. Isopach thicks contain more undeformed strata and show more soft‐sediment folds. These relationships suggest better preservation of strata in structurally controlled inherited bathymetric lows. In general, MTE bodies are preferentially deposited in these paleobathymetric lows. A minimum of six vertically stacked MTE bodies are recognized in the main study area with thicknesses ranging from less than one to tens of meters. MTE bodies show a general S‐to‐SSE paleotransport direction, with significant local variation, reflecting either underlying bathymetric relief and/or different source locations. Repeated MTEs resulted in a reduction of the overall basin gradient and created local positive bathymetry. Sand fairways and ponded sheet deposits in the overlying Brushy Canyon Formation are focused in bathymetric lows, and sands thin and onlap onto bathymetric highs.

MASS‐TRANSPORT DEPOSITS IN THE UPPER PALEOCENE CHICONTEPEC FORMATION, MEXICO

STEPHEN P.J. COSSEY Cossey and Associates Inc., P.O. Box 1510, Durango, Colorado 81302, U.S.A.

e‐mail: [email protected] Abstract: The Paleocene and Eocene Chicontepec Formation crops out along the western margin of the Tampico–Misantla basin, located in northeastern Mexico in the states of Veracruz, Hidalgo, and San Luis Potosí. This succession records deposition in a deep‐marine, foreland basin between the Cretaceous Golden Lane Atoll and the Tertiary Sierra Madre Oriental. In the northern part of this outcrop belt, slope deposition is recorded primarily by deformed and undeformed thin‐bedded turbidites with occasional sand‐rich lobes, channel fills, and debrites. Sediment transport and slumping direction in this area was to the east and southeast. The slumped, thin‐bedded turbidites show the complete spectrum of deformation, including coherent slumps, semi‐coherent, faulted, boudinaged, and chaotic slumps. More than one of these types of slumps can occur in a single outcrop. All the slumps have extremely flat upper surfaces, indicating that the tops of the slumps were probably eroded during subsequent bypass sedimentation. An unusual, flat‐topped toe thrust is also preserved at one of the outcrops. A large, spectacular 26‐m‐thick debrite has faulting at its erosional margin, pressure ridges on its top, and strong evidence that the debris flow did not create the void that it occupies. These spectacular outcrops provide a unique opportunity to study the detailed internal characteristics and allow evaluation of the reservoir quality in terms of continuity and connectivity. Evidence from these outcrops indicates that sub‐seismic‐scale coherent, semicoherent, and faulted slumps can be extremely complex, and hence, difficult to identify with typical oil‐industry technology, such as 3D seismic, core, and image logs.

HETEROGENEITY OF INTERNAL STRUCTURES IN A MASS‐TRANSPORT DEPOSIT, UPPER CRETACEOUS TO PALEOCENE AKKESHI FORMATION, HOKKAIDO ISLAND, NORTHERN JAPAN

HAJIME NARUSE

Division of Earth and Planetary Science, Graduate School of Science, Kyoto University, Kitashirakawa‐oiwakecho, Sakyo‐ku, Kyoto 606‐8502, Japan

Present address: Department of Earth Sciences, Faculty of Science, Chiba University, 1‐33 Yayoicho, Inage‐ku, Chiba 263‐8522, Japan

e‐mail: [email protected]‐u.jp

AND

MAKOTO OTSUBO Research Center for Deep Geological Environments, National Institute of Advanced Industrial Science and

Technology, Tsukuba Central 7, 1‐1, Higashi 1‐Chome, Tsukuba‐shi, Ibaraki‐ken, 305‐8567 Japan e‐mail: otsubo‐[email protected]

ABSTRACT: Analysis of a deep‐sea mass‐transport deposit exposed as a nearly 1.6 km continuous outcrop reveals heterogeneous internal structures and existence of a compressional stress field during transportation and deposition. Deposit of gravelly mudstone, containing large deformed sedimentary blocks (long axis from tens of centimeters up to 100 m), occurs in the Upper Cretaceous (Maastrichtian) to Paleocene Akkeshi Formation, Hokkaido Island, northern Japan. The outcrop was photographed and sketched, and clast sizes were measured to study quantitatively the internal structure of this mass‐transport deposit. The size distribution of sedimentary blocks exhibits a power‐law distribution, but mean size and concentration of blocks exhibit highly variable, local fluctuations. This mass‐transport exposure exhibits three facies, based on size and spatial arrangement of accumulated blocks. Facies A consists of relatively small blocks (long axes approximately 1 to 10 m), supported by a gravelly mudstone matrix. Facies B consists of clast‐supported moderate blocks (long axes < 30 m). Generally, blocks in Facies B are deformed significantly. Facies C comprises mainly large blocks with long axes up to 100 m. Considering the evidence of turbidites in blocks of Facies C, these blocks not only slid but also rotated both horizontally and vertically. In some cases, original stratigraphy found within these blocks is inverted. Facies A and B alternate downcurrent, while Facies C occurs only at the more distal end of the exposure. Usually, long axes of blocks are oriented parallel to the bedding surface, suggesting a laminar state of flow. In addition, application of the multiple inverse method to mesoscale faults observed in the blocks reveals possible internal paleostress fields that existed before deposition. This analysis suggested two different stress fields: (1) a uniaxial compressional stress field, where the σ1 axis is oriented normal to bedding surface, and (2) a triaxial compressional stress field, where the σ1 axis is oriented parallel to the paleocurrent direction. This mass‐transport deposit apparently experienced the first stress field when it moved downslope, thereby expanding its surface area. It then experienced the second stress field as it decelerated, because of compression parallel to paleocurrent direction. A heterogeneous nature of internal structures and compressional stress fields appear to be common features of mass‐transport facies of deposits.

MASS‐TRANSPORT DEPOSITS: COMBINING OUTCROP STUDIES AND SEISMIC FORWARD MODELING TO UNDERSTAND LITHOFACIES DISTRIBUTIONS, DEFORMATION, AND THEIR SEISMIC STRATIGRAPHIC

EXPRESSION

MASON DYKSTRA Department of Geology and Geological Engineering, Colorado School of Mines, 1615 Illinois St., Golden,

Colorado 80401, U.S.A. e‐mail: [email protected]

KATERINA GARYFALOU Department of Geology and Petroleum Geology, University of Aberdeen, Aberdeen AB24 3UE,

Scotland, U.K. e‐mail: [email protected]

VANESSA KERTZNUS Department of Geology and Petroleum Geology, University of Aberdeen, Aberdeen AB24 3UE,

Scotland, U.K. Current address: Shell Exploration New Ventures and Business Development, Shell International

Exploration and Production, Inc., 150 Dairy Ashford, Houston, Texas 77079, U.S.A. e‐mail: [email protected]

BEN KNELLER Department of Geology and Petroleum Geology, University of Aberdeen, Aberdeen AB24 3UE,

Scotland, U.K. e‐mail: [email protected]

JUAN PABLO MILANA CONICET and Instituto de Geología, Universidad Nacional de San Juan, Ave. I. de la Roza y Meglioli, 5400

San Juan, Argentina e‐mail: [email protected]

MATTEO MOLINARO Shell International Exploration and Production B.V., Rijswijk, The Netherlands


MAGDALENA SZUMAN AND PHILIP THOMPSON Department of Geology and Petroleum Geology, University of Aberdeen, Aberdeen AB24 3UE,

Scotland, U.K. e‐mail: [email protected]; [email protected]

ABSTRACT: Mass‐transport deposits may act as barriers or baffles to fluid flow in the subsurface, or may conduct fluids via internal structures or lithological connectivity. Conventional seismic and borehole data present radically different scales of observation to assess the likely fluid‐flow behavior of mass‐transport deposits. Seismic‐scale outcrops and high‐resolution seismic data bridge this scale gap. Exceptional outcrops of large mass‐transport deposits are used to develop strategies to relate core‐ and seismic‐scale observations for the purposes of subsurface prediction of reservoir, baffle, or seal potential, and for prediction of fluid flow through mass‐transport deposits in the subsurface. We present here an outline of our approach, and some preliminary results based on two systems of contrasting styles. One is a > 120‐m‐thick debrite of Carboniferous age in northwest Argentina; the other is an approximately 300‐m‐thick slide complex of Jurassic–Cretaceous age in Antarctica. Differences in these two systems are

assessed by evaluating the internal structure and seismic expression of the deposits, based on forward modeling of the outcrop architecture. Topography on the top surface of mass‐transport deposits is defined by very localized (a few meters wavelength and amplitude), localized (a few tens of meters wavelength, a few meters to ~ 10 m amplitude), and subregional (kilometers in wavelength, tens of meters in amplitude) “ponding” or partial confinement of turbidite beds immediately above the mass‐transport deposits. Strain histories and strain distributions are complex and variable within deposits, implying that inferences based on limited well data are likely to yield incorrect conclusions regarding direction of movement and slope orientation. This observation is clearly illustrated by the non‐coaxial deformation, which is visible in high‐resolution seismic data.

OUTCROP AND SEISMIC EXAMPLES OF MASS‐TRANSPORT DEPOSITS FROM A LATE MIOCENE DEEP‐WATER SUCCESSION, TARANAKI BASIN, NEW ZEALAND

PETER R. KING GNS Science, P.O. Box 30 368, Lower Hutt, New Zealand


BRADLEY R. ILG GNS Science, P.O. Box 30 368, Lower Hutt, New Zealand

Present address: Crown Minerals, Ministry of Economic Development, P.O. Box 1473, Wellington 6140, New Zealand

MALCOLM ARNOT AND GREG H. BROWNE GNS Science, P.O. Box 30 368, Lower Hutt, New Zealand

LORNA J. STRACHAN School of Earth, Atmospheric, and Environmental Sciences, The University of Manchester, United

Kingdom Present address: University of Auckland, PB 92019, Auckland Mail Centre 1142, New Zealand

MARTIN CRUNDWELL GNS Science, P.O. Box 30 368, Lower Hutt, New Zealand

AND

KRISTIAN HELLE Department of Earth Sciences, University of Bergen, Bergen, Norway

Present address: StatoilHydro, Research Centre, Sandsliveien 90, Bergen, Norway

ABSTRACT: In north Taranaki, New Zealand, spectacular examples of deep‐water mass‐transport deposits (MTDs) are exposed in coastal cliffs and imaged in nearby offshore seismic reflection data. The MTDs are Late Miocene (Tortonian) in age, and lie within successively overlying successions of volcaniclastic sandstone‐dominated basin‐floor turbidites (Mohakatino Formation), epiclastic sandstone‐ and siltstone‐dominated basin‐floor turbidites (Mount Messenger Formation), and siltstone‐dominated slope deposits (Urenui Formation).

Seismic‐scale MTDs are exposed north of Awakino River and also between the Mohakatino and Tongaporutu river mouths. These MTDs incorporate a range of original deep‐water lithofacies that subsequently have been dramatically deformed into highly chaotic packages during re‐emplacement in mid‐bathyal to lower bathyal water depths near to or beyond the base of slope. There does not appear to be any stratigraphic or lithologic control on the types of beds incorporated into these particular MTDs, and the deformed strata are potentially derived from several original submarine‐fan depositional units.

These seismic‐scale MTDs are in places at least 50 m thick and appear to extend for a few kilometers, although lateral stratigraphic correlation is made difficult by the complex MTD deformation and by postdepositional normal faulting. It is possible that two different MTDs are represented in the outcrop section between Mohakatino and Tongaporutu, and together they may form a larger composite MTD or mass‐transport complex.

At least two large MTD successions are revealed on seismic reflection profiles located offshore, relatively near to the coastal outcrop section. They extend for several tens of kilometers in length, and are up to 330 m (250 ms two‐way travel time (TWTT) thick. These MTDs are in approximately the same stratigraphic interval as those in outcrop (Mohakatino and lower Mount Messenger Formations). At least one of these MTDs extrapolates up structural dip to where an MTD is exposed onshore, but an absolute correlation between the two MTDs is precluded by the lack of seismic data in the intervening coastal transition zone. MTD intervals equivalent to those exposed are also imaged in high‐resolution behind‐outcrop seismic reflection lines, and are recorded by anomalous biostratigraphic signatures in the nearby Pukearuhe‐1 exploration well.

Siltstone‐dominated MTDs of subseismic scale (up to 15 m thick) are evident in central parts of the outcrop section, within fine‐grained intervals near the tops of inner‐fan depositional cycles. They are also present in southern parts of the section (retrogradational and progradational slope), within fine‐grained intervals that lie stratigraphically close beneath incised slope channels infilled with sandstone. Whilst these MTDs are only 5–15 m thick, they could thicken away from the outcrop transect.

The magnitude and styles of deformation within the various exposed MTDs may reflect differing transportation processes or triggering mechanisms. The larger, seismic‐scale MTDs appear to be the product of massive slope failure and downslope translation of strata, or relatively local tectonic movement of the sea bed. The ordered stratigraphic position of the sub‐seismic‐scale MTDs near the tops of inferred depositional cycles suggests that changes in relative base level may have controlled their development.

MASS‐TRANSPORT DEPOSITS OF THE DEEPWATER NORTHWESTERN BORNEO MARGIN—CHARACTERIZATION FROM SEISMIC‐REFLECTION, BOREHOLE, AND CORE DATA WITH IMPLICATIONS FOR

HYDROCARBON EXPLORATION AND EXPLOITATION

SAM ALGAR Murphy Exploration and Production Co., 16290 Katy Freeway, Suite 600, Houston, Texas 77094, U.S.A.


CHRIS MILTON AND HYWEL UPSHALL Murphy Sabah Oil Co. Ltd., Level 26, Tower 2, Petronas Twin Towers,

Kuala Lumpur City Centre, Kuala Lumpur, 50088, Malaysia

JON ROESTENBURG Geotransformations Pty Ltd., 19 Adelaide Crescent, Helena Valley, Western Australia, 6056, Australia

AND

PAUL CREVELLO BPC Limited, 28 Cumberland St., Nassau, N‐1991, The Bahamas

ABSTRACT: A regional study of deepwater northwest Borneo indicates that within the Late Miocene to Recent deepwater thrust belt, up to 50% of the sediments comprise large‐scale, remobilized units interpreted as mass‐transport deposits (MTDs). More than 6000 km2 of 3D seismic data, 20 exploration and appraisal wells, and more than 600 m of core were examined as part of this integrated study. The MTDs are 10 to 200 m thick, and are composed predominantly of claystone, though subordinate sands and siltstones are present. Intercalated with the MTDs are turbidites, which form sandstone reservoirs of the petroleum discoveries found in the area. Intriguingly, the thickest sands are often found immediately overlying the MTDs, and there is evidence to suggest that the topography on top of the MTD may influence sand distribution. There is also seismic‐stratigraphic evidence suggesting that MTDs may be locally erosive and could also form lateral and vertical seals and even contain source rocks. In the study area, core and borehole image logs are the most reliable data types to identify the MTDs, although the overcompaction of the MTDs often means that simple borehole density, sonic, and resistivity logs can also be used. A variety of MTD lithofacies indicate a continuum from debritic claystones with extremely variable, incoherent, dip architectures in the image logs to more simply folded claystones, which have more coherent dips. Overcompaction of the MTDs relative to the overlying and underlying turbidites often creates an impedance contrast that can be mistaken for that of a sandstone–claystone interface in the turbidites. Hence, seismic interpretation in areas with MTDs is more challenging and potentially misleading than in areas without MTDs.

LITHOFACIES ANALYSIS AND STRATIGRAPHIC ARCHITECTURE OF A DEEP‐WATER CARBONATE DEBRIS APRON: LOWER CRETACEOUS (LATEST APTIAN TO LATEST ALBIAN) TAMABRA FORMATION, POZA RICA

FIELD AREA, MEXICO

ROBERT G. LOUCKS Bureau of Economic Geology, John A. and Katherine G. Jackson School of Geosciences,

The University of Texas at Austin, Austin, Texas 78713‐8924, U.S.A. e‐mail: [email protected]

CHARLES KERANS Department of Geological Sciences, John A. and Katherine G. Jackson School of Geosciences, University Station C1100, The University of Texas at Austin, Austin, Texas 78712‐0254, U.S.A.


XAVIER JANSON Bureau of Economic Geology, John A. and Katherine G. Jackson School of Geosciences,

The University of Texas at Austin, Austin, Texas 78713‐8924, U.S.A. e‐mail: [email protected]

AND

M. ALFREDO MARHX ROJANO PEMEX Production and Exploration Company of Mexico


ABSTRACT: Deep‐water carbonate debris aprons adjacent to shallow‐water platforms are complex depositional features that are produced by density‐flow and suspension processes. Sediment is supplied from the platform margin and from biota living in the shallower part of the open sea. The Lower Cretaceous (latest Aptian to latest Albian) Tamabra Formation in the Poza Rica field area of eastern Mexico is a debris apron deposited adjacent to the western side of the Tuxpan Platform in east‐central Mexico. Its stratal architecture is well defined by 3‐D seismic, cores, and wireline‐log data, allowing analysis of depositional processes that created the lithofacies and sequence stratigraphic controls on depositional architecture and patterns. Within the Tamabra debris apron, an orderly pattern of depositional units reflects the control of relative sea‐level changes on the availability of source material and types of density flows generated. Thick intervals of debris‐flow and mud‐flow deposits, composed of platform‐ and slope‐derived carbonate muds, skeletal grains, and clasts, are interpreted as being deposited during sea‐level lowstands and transgressions or during early highstands when the platform was rapidly aggrading, whereas thick intervals of hyperconcentrated to concentrated density‐flow and turbidite deposits, composed of skeletal sands, are interpreted as having been deposited when the platform was flooded and shedding during highstands of sea level. The Tamabra debris apron is an excellent analog for comparing with other carbonate debris aprons and for use in deciphering other debris aprons having poor data control.

RESERVOIR CHARACTERIZATION OF SAND‐PRONE MASS‐TRANSPORT DEPOSITS WITHIN SLOPE CANYONS

LAWRENCE D. MECKEL, III Woodside Energy Ltd., Perth, Western Australia, Australia

Present addrsss: Tately N.V., Plaza Bapindo, Mandiri Tower, 21st. Floor, Suite 2102, Jln. Jend. Sudirman Kav. 54‐55, Jakarta 12190, Indonesia


MATTHEW ANGELATOS Woodside Energy Ltd., Perth, Western Australia

Present address: Petroleum Development Oman, P.O. Box 81, Post Code 100, Mina Al Fahal ‐ Muscat, Sultanate of Oman

JOS BONNIE Shell International Exploration and Production, Perth, Western Australia

Present address: Sakhalin Energy Investment Company, Sfera Office Building, 78 Chekhov Street, Yuzhno‐Sakhalinsk 693008, Russian Federation

RODERICK MCGARVA TASK Geoscience Ltd., Unit F11, Exploration House, Aberdeen Science & Energy Park,

Bridge of Don, Aberdeen, AB23 8GX, U.K.

TONY ALMOND Woodside Energy Ltd., Perth, Western Australia

Present address: Woodside Energy (U.S.A.), Inc., 5151 San Felipe, Suite 1200, Houston, Texas 77056, U.S.A.

NEIL MARSHALL Woodside Energy Ltd., Woodside Plaza, 240 St. Georges Terrace, Perth, Western Australia, Australia

6000

LAURENT BOURDON Shell International Exploration and Production, Perth, Western Australia

Present address: Shell Development (Australia) Proprietary Limited, QV1 Building, 250 St. Georges Terrace, Perth WA 6000, Australia

AND

KAREN AURISCH Woodside Energy Ltd., Perth, Western Australia

Present address: Origin Energy Ltd, Level 2, South Tower, John Oxley Centre, 339 Coronation Drive, Milton, Queensland, Australia 4064

ABSTRACT: Oil‐ and gas‐bearing sands occur at multiple stratigraphic levels within the fill of an unidentified mid‐slope submarine canyon. Sand‐to‐shale ratio of the canyon fill is approximately 15% (calibrated to an average gross thickness of ~ 200 m), based on seismic and well control. Individual sand‐prone intervals, which vary in thickness from 1 to 25 m, can have excellent reservoir properties (average net‐to‐gross from base sand to top sand of ~ 70%; average porosity ~ 30%; average permeability ~ 1500 mD). On seismic displays, sands have podor tongue‐shaped geometries in plan view, with linear to curvilinear internal discontinuities. Sands display a backstepping architecture, although there is a degree of vertical overlap and compensational stacking. Sinuous channel‐form geometries, which characterize

reservoirs in many slope canyons, are not evident. Seismic cross sections show that sands, visualized as single seismic loops, have flat bases and rugose tops, and occur above a characteristically chaotic, low‐amplitude seismic facies. Well logs and whole‐rock cores over each of these three reservoir‐prone intervals indicate that there is a preferred facies association. This association is a muddy debrite (corresponding to the chaotic seismic facies) overlain by massive sands and composite sandy and/or mixed‐lithology breccias, in turn overlain by thin‐bedded turbidites, culminating in thin‐bedded hemipelagic sediments. Conglomerates punctuate the stratigraphic column but are most prevalent in the lowermost part of the succession.

RESERVOIR CHARACTERISTICS AND CLASSIFICATION OF SAND‐PRONE SUBMARINE MASS‐TRANSPORT DEPOSITS

LAWRENCE D. MECKEL, III

Woodside Energy Ltd., Perth, Western Australia, Australia present addrsss: Tately N.V., Plaza Bapindo, Mandiri Tower, 21st. Floor, Suite 2102,

Jln. Jend. Sudirman Kav. 54‐55, Jakarta 12190, Indonesia e‐mail: [email protected]

ABSTRACT: Mass‐transport deposits are remobilized sedimentary successions that are common in the deepwater stratigraphic record. Because mass‐transport deposits are typically mud‐prone, few industry geoscientists consider sand‐prone mass‐transport deposits to merit significant attention. However, recent studies confirm that mass‐transport deposits can act as significant reservoirs in oil and gas fields. Furthermore, these features can also represent geohazards that warrant consideration in deepwater drilling programs. Identifying and characterizing such deposits accurately in the subsurface allows better understanding of their spatial continuity, prediction of reservoir performance, and generation of models with representative rock properties away from control points. These implications are especially important given ever‐increasing costs associated with the development of deepwater fields. Moreover, this underappreciated play type provides underexplored greenfield and brownfield potential in many continental‐slope trends. This paper uses personal observations, as well as published examples from producing fields, the seafloor and shallow subsurface, outcrops, and flume‐tank experiments to illustrate specific criteria that aid in the recognition of sand‐prone mass‐transport deposits in the subsurface. None of these criteria is sufficient by itself to distinguish between a mass‐transport deposit and a turbidite system; however, in aggregate, these criteria are sufficiently diagnostic to identify mass‐transport deposits that are likely to be reservoir‐prone. Specifically, mass‐transport deposits can be differentiated from turbidites by seismic morphology, core‐scale sand‐body architecture, and petrophysical properties, while sand‐prone mass‐transport deposits can be differentiated from more common mud‐prone mass‐transport deposits by relative size, associated vertical facies assemblages, and well data.

DEFORMATION VERSUS DEPOSITION OF SEDIMENT WAVES IN THE BISMARCK SEA, PAPUA NEW GUINEA

GARY HOFFMANN Earth Sciences Dept., University of California, Santa Cruz, California 95064, U.S.A.


ELI SILVER Earth Sciences Dept., University of California, Santa Cruz, California 95064, U.S.A.


SIMON DAY Aon Benfield Hazard Research Centre, Department of Earth Sciences, University College London,

Gower Street, London WC1E 6BT, U.K. e‐mail: [email protected]

NEAL DRISCOLL Scripps Institution of Oceanography, La Jolla, California 92093, U.S.A.


AND

DANIEL ORANGE AOA Geophysics, Castroville, California 95012, U.S.A.

Current address: Black Gold Energy LLC, Jalan Kemang Timur #22, Plaza City View 5th Floor, Kemang, Jakarta 12510 Indonesia


ABSTRACT: We examine four fields of undulating sediment in the Bismarck Volcanic Arc, Papua New Guinea, to assess causal mechanisms. The possible mechanisms include deformation, episodic turbidity currents, and continuous bottom currents. Two of the fields, one off the coast of Dakataua caldera and one in Kimbe Bay, display an arcuate and irregular morphology similar to one another in multibeam imagery. In sidescan imagery, each of these fields is proximally associated with downslope scour features and other evidence of turbidity‐current activity. There is no evidence of significant bottom‐current activity in these regions. We suggest that these two fields were formed by a combination of extensional deformation and repeated turbidity currents, based on a quantitative analysis of their morphologies and the evidence for turbidity currents in each location. In particular, the Kimbe Bay and Dakataua fields are morphologically distinct from a field of turbidity‐current sediment waves mapped nearby in Hixon Bay (Torkoro Trough field). Also in Hixon Bay, an irregular depression north of Lolobau Island that may be a slide scar appears to have provided the initial topography for a small turbidity‐current sediment‐wave field growing within it. Although flows that formed the sediment‐wave fields in the study area are not specifically defined as mass‐transport processes, the processes that preconditioned all of these field sites for subsequent sediment‐wave formation clearly are. In the Dakataua and Kimbe Bay fields, the mass‐transport process of sediment creep in conjunction with turbidity currents is the necessary combination of mechanisms to generate the morphology of the sediment waves observed. Likewise in the Hixon Bay fields, a slide scar exhumed by an earlier extensive mass‐failure event was required to create the necessary seafloor morphology to appropriately funnel the subsequent sediment‐wave‐forming turbidity currents.

BIOSTRATIGRAPHY OF AN UPPER MIOCENE MASS‐TRANSPORT DEPOSIT ON DEMERARA RISE, NORTHERN SOUTH AMERICAN MARGIN

WESLEY C. INGRAM Department of Geological Sciences, Florida State University, Tallahassee, Florida 32306‐4100, U.S.A.

Present address: Devon Energy Corporation, 20 North Broadway, Oklahoma City, Oklahoma 73102‐8260, U.S.A.


DAVID C. MOSHER Natural Resources Canada, Bedford Institute of Oceanography, Dartmouth,

Nova Scotia B2Y 4A2, Canada e‐mail: [email protected]

AND

SHERWOOD W. WISE, JR. Department of Geological Sciences, Florida State University, Tallahassee, Florida 32306‐4100, U.S.A.


ABSTRACT: The Demerara Rise is a deep‐water plateau situated off the coast of South America in the equatorial Atlantic. Its geographic position makes its sedimentary record a desirable target to investigate tectonic and paleoceanographic signals in the Atlantic Ocean. Numerous mass‐transport deposits (MTDs) were interpreted from seismic reflection profiles on the outer reaches of the plateau. One such MTD was drilled and sampled during Ocean Drilling Program Leg 207, Site 1261. This MTD overlies a regionally correlated middle to late Miocene unconformity that resulted from extensive erosion that caused removal of up to 220 m of sediment down to Eocene strata. Calcareous nannofossils were analyzed to determine the age of the 59‐m‐thick MTD lithologically described as slope conglomerate. Its age and corresponding stratigraphic sequence are used to infer possible causative factors in its emplacement. The slope conglomerate contains highly colored sandy carbonate clasts and silty–sandy turbidite rocks supported in a nannofossil‐rich hemipelagic claystone matrix. The carbonate clasts are early Miocene (nannofossil Zone NN4), and the claystone matrix is late Miocene (Subzone NN11b) in age; stratigraphic relationships place the slope conglomerate sequence within nannofossil Subzone NN11b (7.2–5.5 Ma). A normal listric growth fault is located 5 km upslope of the drill site. These stratigraphic and structural relationships suggest causative mechanisms for sediment mass failure and generation of the MTDs. The age of the studied slope conglomerate provides an upper age limit (7.2 Ma) for the regional Miocene unconformity. The unconformity correlates in time with deepening of Fram Strait off Greenland, shoaling of the Isthmus of Panama, and establishment of polar glaciations. These changes resulted in intensification of bottom water currents and enhanced upwelling along continental margins throughout the Atlantic. This current intensification possibly led to increased erosion and generation of locally steep slopes along the flanks of Demerara Rise. Probable seismic activity, as indicated by the proximal shallow fault, initiated sediment mass failure and emplacement of the studied conglomerate. Similar erosion and mass‐transport activity is reported throughout the Atlantic during this period of time, indicating the importance of these paleoceanographic changes to continental‐margin development.

PROPERTIES OF MASS‐TRANSPORT DEPOSITS AS INFERRED FROM DYNAMIC MODELING OF SUBAQUEOUS MASS WASTING: A SHORT REVIEW

FABIO V. DE BLASIO Department of Geosciences, University of Oslo, P.O. Box 1047, Blindern, N‐0316 Oslo, Norway


AND

ANDERS ELVERHØI International Centre for Geohazards, Norwegian Geotechnical Institute, P.O. Box 3930, Ullevål Stadion,

N‐0806 Oslo, Norway e‐mail: [email protected]

Abstract: We discuss recent attempts to investigate some features of mass‐transport deposits (MTDs) from a dynamic and numerical modeling viewpoint. We selected some study examples, such as the problem of the large mobility of submarine mass wasting, emplacement of erratic blocks, and possible change of rheologic properties during flow. Some lubrication mechanisms are needed to explain mobility of submarine slides, and in this respect we discuss hydroplaning and shear wetting models. We show that hydroplaning could explain several features of small, cohesive debris flows such as the Finneidfjord landslide in Norway, and emplacement of outrunner blocks in the Nigerian basin or the Faeroe Islands. However, larger submarine slides usually scour the sea bottom and need a much higher velocity to hydroplane. For this reason, additional mechanisms must be invoked to explain dynamics of the largest submarine slides. In relation to the giant Storegga slide off Norway, we discuss possible effect of the high shear rates due to friction with ambient water on the surface of a submarine slide. This may result in strength loss of sediments and remolding, with consequent increase in mobility. At times, a mobile debris flow may raft huge blocks along its path, providing a further clue as to velocity, impact forces, and block resistance. In this respect, we discuss a couple of examples from the Arctic Sea and the Balearic Basin. We argue that a better understanding of geometry and sedimentologic characteristics of MTDs will require more dedicated studies on submarine slide dynamics in the subaqueous environment. In turn, this should be achieved with an integrated approach between field data, experimental activity, and numerical simulations.

HINLOPEN–YERMAK LANDSLIDE, ARCTIC OCEAN—GEOMORPHOLOGY, LANDSLIDE DYNAMICS, AND TSUNAMI SIMULATIONS

MAARTEN VANNESTE NGI – International Centre for Geohazards (ICG), P.O. Box 3930, Ullevål Stadion, N‐0806 Oslo, Norway


CARL B. HARBITZ NGI – International Centre for Geohazards (ICG), P.O. Box 3930, Ullevål Stadion, N‐0806 Oslo, Norway

FABIO V. DE BLASIO Department of Geosciences, University of Oslo – International Centre for Geohazards (ICG),

P.O. Box 1053 Blindern, N‐0316 Oslo, Norway

SYLFEST GLIMSDAL NGI – International Centre for Geohazards (ICG), P.O. Box 3930, Ullevål Stadion, N‐0806 Oslo, Norway

JÜRGEN MIENERT Department of Geology, University of Tromsø, Dramsveien 201, N‐9037 Tromsø, Norway

AND

ANDERS ELVERHØI Department of Geosciences, University of Oslo – International Centre for Geohazards (ICG),

P.O. Box 1053 Blindern, N‐0316 Oslo, Norway

ABSTRACT: Swath bathymetry data from the glacier‐fed northern Svalbard margin reveal geomorphological details of a large submarine landslide, the Hinlope–Yermak Landslide. Multiple planar escarpments have several hundreds of meters of relief, with a maximum headwall height exceeding 1400 m at the mouth of the Hinlopen cross‐shelf Trough. Within the slide‐scar area, this landslide created a rugose seabed geomorphology, with little mass‐transport deposition in the immediate vicinity of major escarpments. Beyond a pronounced constriction, occurrence of semitransparent acoustic units on seismic profiles indicates that mass‐transport deposits are likely the accumulation of remolded and/or fluidized debris flows that are in places hundreds of meters thick. The surface expression of the mass‐transport deposits is hummocky with flow structures, arcuate pressure ridges, and rafted blocks. Smaller debris lobes close to landslide sidewalls are the result of secondary, marginal failures. At the outer rim of extensive mass‐transport deposits, numerous rafted blocks rise from the semitransparent sediment unit, and tower hundreds of meters above the surrounding debris. Maximum remobilized volume from the slide‐scar area, estimated from pre‐landslide bathymetric reconstruction, is approximately 1350 km3. Headwall heights, the ratio of excavated volume and slide scar area, and the height of rafted blocks are large, compared to other landslides documented on siliciclastic margins. The position, thickness, and shape of the mass‐transport deposits illustrate high mobility of sediments involved in submarine landsliding. Their dimensions require numerical modeling to understand landslide dynamics and potential to generate tsunamis. In simulations of sediment dynamics, large blocks are rafted by a loose debris flow, derived from disintegrating landslide material in the headwall area. The main failure process finishes after approximately 1 hour. The upper slide scar is probably not the source area for large rafted blocks.

The Hinlopen–Yermak landslide most likely created a significant tsunami, considering that remobilized sediment volume, initial acceleration, maximum velocity, and possible retrogressive development govern landslide‐generated tsunamis. Steep waves, implying dispersive and nonlinear effects, probably were more pronounced than for most other tsunamis induced by submarine landslides. These features exist because of the combination of high speed and substantial thickness of mass transport. Propagation and coastal impact of the tsunami is simulated by a weakly nonlinear and dispersive Boussinesq model. Close to the landslide area, simulations return sea‐surface elevations exceeding 130 m, whereas sea‐surface elevations along coasts of Svalbard and Greenland are on the order of tens of meters.

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