Quantitative Analysis of the Calcareous Nannofossil Assemblages from CIROS-1, Victoria Land Basin, Antarctica

• Main Author: Watkins, David K.
• Format: Text
• Language: unknown
• Published: DigitalCommons@University of Nebraska - Lincoln 2007
• Subjects: Antarctica; calcareous nannofossils; CIROS-1; Oligocene; Earth Sciences; Antarctic; Victoria Land; McMurdo Sound; Cape Robert; Antarc*
• Online Access: https://digitalcommons.unl.edu/geosciencefacpub/234; https://digitalcommons.unl.edu/context/geosciencefacpub/article/1235/viewcontent/Watkins_2007_JNR_Quantitative_Analysis_of_the_Calcareous_Nannofossil_Assemblages_from_CIROS_1_Victoria_Land_Basin_Antarctica.pdf

The lower portion of the CIROS-1 core (McMurdo Sound, Antarctica) has been cited as evidence for Late Eocene continental glaciation on Antarctica. A reassessment of this age determination is warranted in the face of mounting evidence from multiple proxies that continental glaciation was initiated by rapid ice-growth during the earliest Oligocene. Examination of calcareous nannofossil assemblages from this section confirmed very low fossil abundance, low species richness, and the presence of reworked taxa. A minimum of 37% of the total species richness in the section comprises reworked forms, including Late Cretaceous and latest Paleocene to Middle Eocene species. Quantitative analysis suggests a further 20-33% of the species were part of the reworked component. Given the very low abundance, sporadic occurrence, and predominance of demonstrably reworked species in the CIROS-1 section, coupled with the well-documented reworking in nearby Cape Robert Project Oligocene strata, the biostratigraphic integrity of the remaining species is clearly suspect. At best, a latest Eocene to Early Oligocene age assignment is justified. The large uncertainty in the age determination indicates that the CIROS-1 section cannot be used as evidence of a pre-Oligocene initiation of Antarctic continental glaciation.