Clay and smectite analysis of sediment core CRP-2A

• Main Author: Ehrmann, Werner
• Format: Dataset
• Language: English
• Published: PANGAEA 2000
• Subjects: 14.2 km at 096° true from Cape Roberts; Cape Roberts Project; Core wireline system; CRP; CRP-2; CRP-2A; CWS; DEPTH; sediment/rock; Grain size; sieving/settling tube; off Cape Roberts; Ross Sea; Antarctica; Sampling/drilling from ice; Size fraction < 0.002 mm; clay; Smectite; integral width; Smectite/standard ratio; X-ray diffraction TEXTUR; clay fraction; Antarctic; Southern Ocean; East Antarctica; McMurdo Sound; Pacific; Cape Roberts; Roberts Cape; Antarc*
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.56138; https://doi.org/10.1594/PANGAEA.56138

Sediments of the CRP-2/2A drill core from the continental shelf of McMurdo Sound in Ross Sea, Pacific sector of the Southern Ocean, have been investigated for their clay mineral assemblages, especially for the smectite contents and smectite crystallinities. Highest smectite amounts and best crystallinities occur in three intervals below 485 mbsf in CRP-2/2A. They indicate deposition of sediments during a time when chemical weathering was active on large ice-free areas on the nearby Antarctic continent. In he upper part of the core, smectite contents are much lower and crystallinities are worse. This clay mineral composition indicates deposition of sediments during a time when physical weathering prevailed on an ice-covered continent. At deep-sea sites around Antarctica the shift from smectite-dominated to smectite-poor and illite-rich assemblages is well dated as earliest Oligocene, 33.9-33.1 Ma, and documents the onset of continental glaciation in East Antarctica. At CIROS-1 a corresponding shift in the clay mineralogy was observed at a depth of 425-445 mbsf.