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Title: Faunal, sedimentological and geochemical indicators of dysoxia in Cretaceous marine sediments
Author: Weavers, Ellen Louise
ISNI:       0000 0004 2686 1175
Awarding Body: University of Greenwich
Current Institution: University of Greenwich
Date of Award: 2010
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This project compares palaeo-oxygenation related features of lower Cretaceous rocks from the shallow sea muds of the Gault Clay (south east England) and Niveau Pacquier and Briestroffer sequences (south east France), and the Tarfaya Basin upwelling-zone Amma Fatma sediments (Morocco). The palaeo-oxygenation indicators investigated include: sedimentological proxies, including ichnology, sedimentology, taphonomy and pyrite framboid size distribution; faunal proxies including macrofaunal properties, and biofacies models; and geochemical proxies, including trace-element abundances [Mo, V, Ni, Mn], element ratios and parameters [U/Th, authigenic U (Ua), V/Cr, Ni/Co, Ni/V, (Cu+Mo)/Zn, V/Sc and V/(V+Ni)] and Fe-S-C systematics [Total Organic Carbon (TOC), Total Sulphur/TOC ratio, Degree of Pyritisation and the Indicator of Anoxia]. The presence of lamination is a key sedimentological indicator of restricted bottom water oxygenation conditions. New descriptive categories of pyrite morphology are proposed. Interpretation of faunal proxies can be limited by poor preservation, but taphonomy-related indicators correlate well with proposed palaeo-oxygenation conditions. Molybdenum is the most reliable of the trace-metal enrichment proxies studied and altered numerical boundaries are proposed for Ua, U/Th, V/Cr and Ni/Co. Of the Fe-S-C systematics indicators, Total Organic Carbon and the Indicator of Anoxia to provide the greatest definition between palaeo-oxygenation data sets. Combinations of trace metal and Fe-S-C indicators such as [Molybdenum Enrichment Factor x Indicator of Anoxia], and plots of Ua against TOC provide the strongest palaeo-oxygenation proxies and distinguish between oxic/dysoxic, anoxic and euxinic conditions.
Supervisor: Wray, David ; Gale, Andrew Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QD Chemistry ; QE Geology