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Paleocene and Maastrichtian calcareous nannofossils from clasts in Pleistocene glaciomarine muds from the northern James Ross Basin, western Weddell Sea, Antarctica

January 17, 2007

Site NBP0602A-9, drilled during the SHALDRIL II cruise of the RV/IB Nathaniel B. Palmer, includes two
holes located in the northern James Ross Basin in the western Weddell Sea, very close to the eastern margin of the
Antarctic Peninsula. Sediment from both holes consists of very dark grey, pebbly, sandy mud, grading to very dark
greenish grey, pebbly, silty mud in the lower 2.5 m of the second hole. In addition to abundant pebbles found
throughout the cores, both holes contain numerous sedimentary clasts. Biostratigraphic analysis of diatom assemblages
from the glaciomarine muds yields rare to few, poorly preserved diatoms. The mixed assemblage consists mostly of
extant species, but also includes reworked taxa that range to the Miocene. The absence of Rouxia spp., however,
suggests the sediment is late Pleistocene in age. The sedimentary clasts, on the other hand, are nearly barren of diatoms,
but contain rare, moderately to well-preserved calcareous nannofossils. The clasts contain three distinct assemblages.
Two clasts are assigned an early Maastrichtian age based on the presence of Biscutum magnum and Nephrolithus
corystus, while one clast yields a late Maastrichtian age based on the presence of Nephrolithus frequens. These samples
also contain other characteristic Late Cretaceous species, including Biscutum notaculum, Cribrosphaerella daniae,
Eiffellithus gorkae, Kamptnerius magnificus, and Prediscosphaera bukryi. Two samples yield an early Paleocene
assemblage dominated by Hornibrookina teuriensis. The Maastrichtian assemblages are similar to those found in the
López de Bertodano Formation on Seymour and Snow Hill Islands, making it the likely source area for the Cretaceous
clast material. Although no calcareous nannofossils have been reported from Paleocene formations on these islands, the
occurrence of calcareous foraminifers suggests other calcareous plankton may be present; thus the Paleocene clasts
likely also originated from the Seymour Island area.

Publication Year 2007
Title Paleocene and Maastrichtian calcareous nannofossils from clasts in Pleistocene glaciomarine muds from the northern James Ross Basin, western Weddell Sea, Antarctica
DOI 10.3133/ofr20071047SRP019
Authors D.K. Kulhanek
Publication Type Report
Publication Subtype USGS Numbered Series
Series Title Open-File Report
Series Number 2007-1047-SRP-019
Index ID ofr20071047SRP019
Record Source USGS Publications Warehouse