PALEOENVIRONMENTAL SIGNIFICANCE OF BONE-BEDS IN ORGANIC-RICH MUDSTONESUCCESSIONS - AN EXAMPLE FROM THE UPPER TRIASSIC OF SOUTH-WEST BRITAIN

Authors
Citation
Jhs. Macquaker, PALEOENVIRONMENTAL SIGNIFICANCE OF BONE-BEDS IN ORGANIC-RICH MUDSTONESUCCESSIONS - AN EXAMPLE FROM THE UPPER TRIASSIC OF SOUTH-WEST BRITAIN, Zoological journal of the Linnean Society, 112(1-2), 1994, pp. 285-308
Citations number
64
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Zoology
ISSN journal
0024-4082
Volume
112
Issue
1-2
Year of publication
1994
Pages
285 - 308
Database
ISI
SICI code
0024-4082(1994)112:1-2<285:PSOBIO>2.0.ZU;2-#
Abstract
A combined field-based/petrographic study to investigate the formation of Rhaetian 'bone-beds' from the Westbury Formation, Upper Triassic o f south-west Britain, has been undertaken. 'Bone-beds' in the Westbury Formation have been found at the top of coarsening upward successions , on flooding surfaces which underlie organic-rich mudstones. These 'b one-beds' are frequently found either overlying or amalgamated with 's hell-beds', and often contain large (up to cobble-sized) intraclasts. This work indicates that they formed during a period of relative sea-l evel rise, when the sediment was being reworked (forming a transgressi ve lag) and a condensed section had developed. Phosphate authigenesis is thought to have occurred at the oxic/Fe-reduction interface, where the pore waters were dysoxic, enriched with dissolved phosphate and re latively acidic. 'Bone-bed' formation was terminated when siliciclasti c mud prograded over the condensed section and 'normal' anoxic/suifidi c pore water conditions were established in the sediment.