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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 49 (1965)

Issue: 3. (March)

First Page: 344

Last Page: 345

Title: Sediment Distribution on the Inner Continental Shelf, West Coast of Southern Africa: ABSTRACT

Author(s): John H. Hoyt, David D. Smith, B. L. Oostdam

Article Type: Meeting abstract


"Sparker" surveys show that the inner continental shelf along a 400-mile stretch of the west coast of South and South West Africa (Olifants River to Luderitz) consists of large areas of virtually sediment-free bedrock and two well-defined elongate bodies of unconsolidated sediment of probable Late Pleistocene-Holocene age.

The sediment distribution pattern is dominated by a strikingly continuous wedge-like body of silts and clays that averages 7 miles in width. This wedge has a maximum thickness of about 80 feet along its inshore edge which lies approximately 3 miles offshore in 200-300 feet of water. Location of the wedge is controlled by a marked steepening in slope of the bedrock surface which coincides with the contact between the Precambrian basement and a sedimentary section of unknown age which dips gently seaward. At the Orange River, the wedge merges with and is overwhelmed by the river's submerged delta.

A second sediment body of lesser extent is the 1 to 1½-mile-wide inshore lens which lies just seaward of the surf zone along a 90-mile stretch south of Luderitz. This inshore lens averages 20 feet in thickness and consists primarily of silty sand and shell material. Gravels, where present, are generally concentrated near the base of the section, and fill irregularities in the dissected bedrock surface. The inshore lens has accumulated shoreward of a series of low discontinuous ridges, and includes reworked

End_Page 344------------------------------

and possibly downwarped Pleistocene shoreline deposits exposed onshore farther south.

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Copyright 1997 American Association of Petroleum Geologists