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Lower Cretaceous benthic foraminifera of the Indian Ocean

Holbourn, Ann EL; (1996) Lower Cretaceous benthic foraminifera of the Indian Ocean. Doctoral thesis (Ph.D), UCL (University College London). Green open access

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Abstract

A comprehensive documentation of Berriasian to Albian benthic foraminiferal assemblages from Indian Ocean DSDP and ODP sites is compiled, which provides a unified taxonomic data base for the Indian Ocean. The benthic foraminiferal assemblages are strongly cosmopolitan, but differ from typical low latitude Tethyan assemblages by the rarity or absence of some characteristic Tethyan lineages. Marked faunal differentiation or endemism is suggested in the Cuvier Basin by the unique composition of agglutinated assemblages at Site 263, which include five new species and numerous taxa not recorded at other Indian Ocean sites. The chronostratigraphy of DSDP and ODP Indian Ocean sites is revised. New ages are determined, which considerably improve the stratigraphic resolution of intervals, previously dated as undifferentiated Aptian or Albian. An older Valanginian to Barremian age is also established for the base of Hole 263. None of the existing benthic foraminiferal zonal schemes are found to be applicable in the Lower Cretaceous of the Indian Ocean. A new biostratigraphic scheme is proposed, which enables the correlation of Lower Cretaceous sedimentary sequences in the Indian Ocean. Palaeoecological interpretations, derived from quantitative analyses of benthic foraminiferal distribution patterns and morphogroup analyses, indicate a marked differentiation in palaeoenvironments along the western and northwestern margins of Australia. Diversity and specific distribution appear strongly influenced by margin subsidence, oceanic circulation patterns, and inferred changes in the depth of the CCD during the Early Cretaceous. Three main transgressive pulses are detected in the Barremian, late Aptian and late early Albian. Productivity fluctuations in the Aptian and Albian probably reflect changes in deep-water circulation and in the nutrient and oxygen budget of an ocean already susceptible to dysoxia. Well ventilated conditions became established during the late early to mid Albian, when a significant drop in CCD occurred, before dysoxic conditions returned to some marginal sites in the late Albian.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: Lower Cretaceous benthic foraminifera of the Indian Ocean
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Thesis digitised by ProQuest.
Keywords: Earth sciences
URI: https://discovery.ucl.ac.uk/id/eprint/10101157
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