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The AAPG/Datapages Combined Publications Database

AAPG Bulletin

Abstract


Volume: 53 (1969)

Issue: 2. (February)

First Page: 468

Last Page: 468

Title: Sedimentation in Santa Barbara Basin, California: ABSTRACT

Author(s): Andrew Soutar

Article Type: Meeting abstract

Abstract:

The Santa Barbara basin off California (depth, 575 m) obtains its surface water from the California Current, which brings cold, nutrient-rich waters from the north and from the subsurface through upwelling. This combination of events causes a high level of plankton productivity. The deep basin water is derived from the oxygen-minimum zone below the California Current, which is centered between 500 and 1,000 m depth and which is a consequence of in situ oxygen depletion by decay and respiration processes and of advection of oxygen-poor water. The bottom water of the basin is trapped below sill depth (480 m) and is nearly depleted of oxygen, because the only exchange is with low oxygen water and because the sediments have high organic content.

Burrowing animals therefore are absent in the center of the basin and sediment deposition is undisturbed. Sediments come from two sources, plankton and land detritus. The winter rains increase the supply of terrigenous detritus, whereas summer production supplies organic material. This biannual variation is recorded in the sediment as annual layers or varves.

Varves develop only below sill depth, and sediments away from the central region show progressively less stratification. Freeze coring and other new sampling techniques, as well as X-radiography, show that the varving extends from the surface to at least a 2-m depth in the central basin sediments, except where turbidite layers disturb the sequence. The characteristics of varved sediments may be useful in reconstructing the history of ancient anaerobic basins.

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