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The AAPG/Datapages Combined Publications Database

AAPG Bulletin

Abstract


Volume: 64 (1980)

Issue: 5. (May)

First Page: 703

Last Page: 703

Title: Lebensspuren of Dysaerobic, Bathyal Basin, California Borderland: ABSTRACT

Author(s): Brian D. Edwards

Article Type: Meeting abstract

Abstract:

The low oxygen waters and bathyal depths of Santa Cruz basin provide harsh conditions for marine life, yet the basin supports a surprisingly high density and diversity of macrofauna. In contrast, biogenic sedimentary structures are low in density. Bottom photographs from 117 stations show a biogenically produced micro-hummocky topography with few resolvable biogenic traces. Recognizable lebensspuren are of three main classes: tracks and trails, depressions, and fecal matter. Echinoderms, the most abundant epifauna on the slope and adjacent basin floor, produce most of the large tracks and trails. Significantly, many tracks and trails are less distinct than similar markings of the abyss owing to the soupy, thixotropic nature of the basinal sediment. Depressions made by ast roids, regular urchins, and bottom-dwelling fish are most common at relatively shallow depths. A characteristic, circular depression made by a feeding, tubicolous polychaete is restricted to the lowermost slope and adjacent basin floor. Holothurian fecal strands dominate the photographically resolvable feces of this bathyal environment. These holothurian feces take the "clothes-line" form common to the abyss.

X-ray radiography and photography of box-core sediment slabs reveal an indistinct burrow mottling resulting from the thixotropic response of the sediment to biogenic disturbance and lack of density contrast for radiography. Although open burrows are common in bottom photographs, few are recognizable in box-core slabs. Similarly, surface lebensspuren have poor preservation potential. When lithified, this bathyal sediment will probably be bioturbate-textured.

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