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The AAPG/Datapages Combined Publications Database

AAPG Bulletin

Abstract


Volume: 64 (1980)

Issue: 5. (May)

First Page: 704

Last Page: 704

Title: Trace Fossils and Stagnation of Deep-Sea Basins: ABSTRACT

Author(s): A. A. Ekdale

Article Type: Meeting abstract

Abstract:

The patterns and intensity of bioturbation of marine sediment are useful indicators of the response of benthic organisms to fluctuating oxygen levels in the bottom water. Trace fossil assemblages in mid-Cretaceous (Barremian-Albian) DSDP core sections from the central and southern Atlantic were examined to document the activities of burrowing infauna relative to episodes of stagnation in deep Atlantic basins during that time.

The mid-Cretaceous anoxic horizons in DSDP cores typically are dark, homogeneous or laminated, organic muds, which alternate with moderately to heavily burrowed facies containing less organic carbon. Bioturbation intensity and trace fossil diversity appear to correlate inversely with the amount of unoxidized carbon in the sediment, suggesting that the more organic-rich facies were deposited under conditions where oxygen was a limiting factor for benthic macro-organisms.

The ichnogenus Chondrites commonly occurs, sometimes to the exclusion of all other kinds of burrows, immediately above and/or below unburrowed, laminated mud. It also occurs in heavily burrowed limestones containing rich trace fossil faunas, including Zoophycos. Therefore, mid-Cretaceous Chondrites apparently were created by animals possessing broad oxygen tolerances; the presence of Chondrites alone in an organic-rich deposit probably indicates dysaerobic conditions.

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