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The AAPG/Datapages Combined Publications Database

AAPG Bulletin

Abstract


Volume: 64 (1980)

Issue: 5. (May)

First Page: 702

Last Page: 702

Title: Bivalve Trace Fossils in British Silesian: ABSTRACT

Author(s): R. M. C. Eagar

Article Type: Meeting abstract

Abstract:

In the English Pennines, Pelecypodichnus Seilacher, a bivalve burrow, is common in silty to sandy sediments of Carboniferous age from near the top of the Kinderscoutian Stage of the Namurian deltaic succession to the lower part of the Westphalian A. At the base of this sequence burrows are short, typically inclined to the bedding, and were primarily resting places of the marine bivalve Enevillia variabilis Eagar MS (formerly cf. Sanguinolites Hind non M'Coy). In the lower part of the succeeding Marsdenian Stage the burrows become longer to form escape structures. These tend to be more nearly vertical to the bedding, straighter, and more numerous, their longer horizontal axes being broadly aligned to prevalent currents. Carbonicola, a nonmarine genus, first appears in the iddle of the Marsdenian, evidently having evolved from Enevillia. Escape shafts associated with Carbonicola are indistinguishable from earlier ones and reach their maximum length near the top of the Namurian, where there was probably selection for elongate shells with low obesity. The latter, being more successful "risers" under heavy sedimentation on the prodelta, ultimately reached low-energy environments as the delta advanced southward. Thus the delta invaded the paleoenvironments of the bivalves, which moved upward or perished. Recent evidence has shown that rising of Enevillia was preceded by downward burrowing to a nearly vertical position, anterior end downward, and that this position was in turn sometimes preceded by a ploughing movement connected to escape shafts as seen in trai s of cf. Chevronichnus Hakes (cf. movement of the living Margaritifera). In Westphalian B Stage Pelecypodichnus is sometimes associated with the nonmarine bivalve Anthracosia.

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