Combined effect of tectonism, eustasy, and sediment supply on the depositional-sequence history of the western offshore, South Africa

Conference · Fri Mar 01 00:00:00 EST 1991 · AAPG Bulletin (American Association of Petroleum Geologists); (United States)

OSTI ID:5676897

Jungslager, E H.A. ^[1]

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1. Soekor Ltd., Parow (South Africa)

Interpreted seismic profiles and maps of depositional systems tracts highlight variations in basin-fill architecture and their inferred causes along western offshore South Africa. Sequence-stratigraphic concepts developed by Exxon were used to interpret 10,000 km of seismic data and logs from 31 exploration boreholes within an area of 90,000 km{sup 2}. Lower frequency second-order supercycles (5-10 Ma) are attributed to changes in the rate of subsidence and are expressed either by predominantly progradational or aggradational depositional supersequence. In addition to these long-duration, basin-wide stratigraphic packages, component depositional sequences that formed in response to third order (1-5 Ma) and higher frequency cycles vary with structural setting within the depobasin, namely depocenter, basin flanks, shelf-edge, and slope systems. High-order sequences are attributed to eustatically driven, high-frequency, base-level changes and/or localized tectonic events (i.e. slope failure, gravity faulting). Variations in the areal distribution of lowstand and shelf-margin systems tracts document lateral shifting sediment supplies and the presence of entrenched feeder-canyons linked to incised valley systems on the shelf. Many canyons, however, terminate updip and may be related to slope failure and headward erosion. The tentative correlation of regionally developed unconformities of the west coast based on microfaunal dating of a limited number of marine condensed sections points to a remarkable correspondence with the Exxon global sea-level chart.

• OSTI ID: 5676897
• Report Number(s): CONF-910403-; CODEN: AABUD
• Journal Information: AAPG Bulletin (American Association of Petroleum Geologists); (United States), Vol. 75:3; Conference: Annual meeting of the American Association of Petroleum Geologists (AAPG), Dallas, TX (United States), 7-10 Apr 1991; ISSN 0149-1423
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
CONTINENTAL SHELF
SEISMIC SURVEYS
STRATIGRAPHY
TECTONICS
SOUTH AFRICA
DEPOSITION
EXPLORATORY WELLS
GEOLOGIC HISTORY
OFFSHORE SITES
SEA LEVEL
SEDIMENTARY BASINS
SEDIMENTS
SUBMARINE CANYONS
VARIATIONS
WELL LOGGING
AFRICA
CONTINENTAL MARGIN
DEVELOPED COUNTRIES
GEOLOGIC STRUCTURES
GEOLOGY
GEOPHYSICAL SURVEYS
LEVELS
SURVEYS
WELLS
580000* - Geosciences