Bulk oxygen and carbon isotopic variation in the Late Cretaceous along with morphometric analysis of biserial planktonic foraminifera
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[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] Expected δ13C shifts are absent in Tanzanian samples that span the majority of the Turonian Age (93.5 - 89.3 Ma). The δ13C values of bulk carbonate and organic carbon were measured throughout the Turonian section and showed only relatively subtle δ13C variation and those variations do not match distinctive isotopic changes documented in deposits of the same age from the North Atlantic and Tethyan Oceans. The lack of expected isotopic patterns cannot be explained as an artifact of changing sources of organic matter, based on biomarker analyses, and suggest δ13C variations are not globally expressed. The absence of expected δ13C patterns in the Turonian has made accurate correlation among sites difficult. Thus, a second phase of this project was examination of the phylogenetic history of Cretaceous biserial planktonic foraminifera. Recent efforts to develop an evolutionary classification of the biserial taxa have led to a radical revision of their species and genus level taxonomy. The high-quality of shell preservation of foraminiferal assemblages from Tanzania makes Tanzanian specimens ideal for testing previously proposed revisions to the Late Cretaceous biserial taxonomy and phylogeny. To investigate proposed taxonomic concepts we use SEM and X-ray images of over 200 biserial specimens and identify five distinct lineages.
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