Cretaceous-Paleogene Foraminiferida of the Victoria Land Basin (Cape Roberts Project)

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Abstract This award supports efforts to characterize the foraminifera in drill core recovered by the Cape Roberts Project (CRP). The CRP will drill four holes, from a sea-ice platform in up to 500m of water, in the southwest Ross Sea. Geophysical site surveys suggest that the four drill holes will provide an aggregate thickness of about 1500m of core and span about 100 to about 30 Ma (Cretaceous-Paleocene). This interval of geological time is not yet documented by in situ stratigraphic sections in either the Ross Sea or East Antarctica. The nearest comprehensive data sources for the Cretaceous and Paleocene) occur in New Zealand, the northern Antarctic Peninsula and the southern ocean. Benthic and planktic Foraminiferida from the core will be used, together with data from other fossil groups, to provide on-site age and stratigraphic control as drilling progresses. Age correlations will be made with DSDP/ODP biostratigraphy from southern Ocean drill sites, and also with New Zealand planktic and benthic zonal/stage schemes. A principal task of this work is to document in the project's initial report, a comprehensive accounting of foraminiferal material present so as to assist planning of post-drilling investigations. Basic information to be recorded on the foraminifera will include: presence, abundance, preservation, species dominance and diversity, stratigraphic distribution, levels of endemism or cosmopolitanism in faunas, and completeness or fragmentation of population structures, et cetera. These data will be used to address a variety of geological problems. Disconformities and acoustic reflectors which extend across the rift system basins and are also expected to be encountered in the drill hole will be dated. Major basin subsidence/uplift trends resulting from compaction and/or rift margin faulting will be deduced from benthic foraminiferal bathymetric indicators. More subtle cyclicity in the stratigraphic distribution of benthic species will be u sed to recognize and document phases of transgression and regression, which in turn may indicate a relationship between sea level oscillation and terrestrial glacial events. The Cretaceous- Paleocene was an interval of time during which the final disintegration of Gondwanaland occurred, specifically the northward movement of New Zealand and Australia away from Antarctica. Foraminifera from the CRP drill holes will contribute to an understanding of the paleogeography and paleoceanography between the highlands and Pacific margin of East Antarctica (the location of the proto-Transantarctic Mountains), and the West Antarctic Rift System basins between this suspected island chain and the highlands of West Antarctica. This will help answer the question as to whether the marine margin of East Antarctica, in the vicinity of the planned drill holes, was located in a Cretaceous cul-de-sac, or whether it occupied, at times, a position on a major oceanic circulation pathway between the SW Indian Ocean, SW Pacific, and SW Atlantic Oceans.