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Research Articles: Deep Marine Sedimentation |
1 Stratigraphy Group, Department of Earth and Ocean Sciences, University of Liverpool, 4 Brownlow Street, Liverpool, L69 3GP, U.K.; hodgson{at}liverpool.ac.uk
2 Stratigraphy Group, Department of Earth and Ocean Sciences, University of Liverpool, 4 Brownlow Street, Liverpool, L69 3GP, U.K.
3 Stratigraphy Group, Department of Earth and Ocean Sciences, University of Liverpool, 4 Brownlow Street, Liverpool, L69 3GP, U.K.; present address: Basin and Stratigraphic Studies Group, School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Manchester, M13 9PL, U.K.
4 Schlumberger Cambridge Research, High Cross, Madingley Road, Cambridge, CB3 0EL, U.K.; present address: Chevron Corporation, Energy Technology Company, 1500 Louisiana Street, 17040B, Houston Texas 77002, U.S.A.
5 Statoil, Forushagen, Grenseveien 21, Stavanger, N-4035, Norway
6 Department of Geotechnology, Delft University of Technology, Mijnbouwstraat 120, 2628 RX Delft, The Netherlands
The integration of correlated outcrop and newly acquired core and wireline logs, extensive paleocurrent data, and accurately mapped surfaces has enabled a common model of the stratigraphic evolution to be developed of four Permian fine-grained submarine fan systems (Fans 1–4) from the Tanqua depocenter, SW Karoo Basin, South Africa. Additionally, this data has revealed the influence of subtle seabed topography on the fan systems' boundaries, internal facies architecture, and paleocurrent directions. Furthermore, the internal stratigraphy of individual fan systems are now known to be more complex than first believed.
Mapping high-frequency intrafan units reveals a progradational–aggradational–retrogradational stacking pattern common to each submarine fan, which allows the geographic and stratigraphic distribution of lithofacies and architectural elements to be predicted. Basinward of the main feeder system, fan axes are dominated architecturally by sheet turbidites with discrete zones of high amalgamation during progradational and aggradational phases, whereas isolated channel forms that cut thin-bedded turbidites are more common in the retrogradational phase. This change is interpreted to be due to local increase in the lower slope gradient through sediment aggradation increasing the potential for channel avulsion and the development of splay lobes during decreasing sediment supply.
The progradational, aggradational, and retrogradational phases are assigned to the early, middle, and late lowstand systems tract of a fifth-order sequence respectively. Each phase is built of higher-frequency (sixth-order) sequences so that each fan is a composite sequence. The overall basinward-to-landward stepping of the individual fans means that moving down dip in any basin-floor fan system, the lowermost sandstone preserved is progressively younger, whilst the uppermost sandstone is progressively older. This stacking pattern imparts an important predictable control on reservoir and seal geometries. This study aids the development of predictive models for fine-grained submarine fan initiation, growth, and abandonment, and lithofacies and architectural element distributions in space and time.
This article has been cited by other articles:
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  A. Saller, K. Werner, F. Sugiaman, A. Cebastiant, R. May, D. Glenn, and C. Barker Characteristics of Pleistocene deep-water fan lobes and their application to an upper Miocene reservoir model, offshore East Kalimantan, Indonesia AAPG Bulletin, July 1, 2008; 92(7): 919 - 949. [Abstract] [Full Text] [PDF]
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 F. Hadler-Jacobsen, M. H. Gardner, and J. M. Borer Seismic stratigraphic and geomorphic analysis of deep-marine deposition along the West African continental margin Geological Society, London, Special Publications, January 1, 2007; 277(1): 47 - 84. [Abstract] [PDF]
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 S. M. Luthi, D. M. Hodgson, C. R. Geel, S. S. Flint, J. W. Goedbloed, N. J. Drinkwater, and E. P. Johannessen Contribution of research borehole data to modelling fine-grained turbidite reservoir analogues, Permian Tanqua-Karoo basin-floor fans (South Africa) Petroleum Geoscience, May 1, 2006; 12(2): 175 - 190. [Abstract] [Full Text] [PDF]
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