Clay mineralogy of Cape Roberts sediment cores

• Main Authors: Ehrmann, Werner, Setti, Massimo, Marinoni, L
• Format: Other/Unknown Material
• Language: English
• Published: PANGAEA 2005
• Subjects: 14.2 km at 096° true from Cape Roberts; 16 km ENE Cape Roberts; Cape Roberts Project; Core wireline system; CRP; CRP-1; CRP-2; CRP-2A; CRP-3; CWS; off Cape Roberts; Ross Sea; Antarctica; Priority Programme 1158 Antarctic Research with Comparable Investigations in Arctic Sea Ice Areas; Sampling/drilling from ice; Sampling/drilling ice; SPP1158; Antarc*; Antarctic; McMurdo Sound; Sea ice
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.738196; https://doi.org/10.1594/PANGAEA.738196

The clay mineral assemblages of the ca. 1600 m thick Cenozoic sedimentary succession recovered at the CRP-1, CRP-2/2A and CRP-3 drill sites off Cape Roberts on the McMurdo Sound shelf, Antarctica, were analysed in order to reconstruct the palaeoclimate and the glacial history of this part of Antarctica. The sequence can be subdivided into seven clay mineral units that reflect the transition from humid to subpolar and polar conditions. Unit I (35-33.6 Ma) is characterised by an almost monomineralic assemblage consisting of well crystalline, authigenic smectite, and therefore does not allow a palaeoclimatic reconstruction. Unit II (33.6-33.1 Ma) has also a monomineralic clay mineral composition. However, the assemblage consists of variably crystallized smectite that, at least in part, is of detrital origin and indicates chemical weathering under a humid climate. The main source area for the clays was in the Transantarctic Mountains. Minor amounts of illite and chlorite appear for the first time in Unit III (33.1-31 Ma) and suggest subordinate physical weathering. The sediments of Unit IV (31-30.5 Ma) have strongly variable smectite and illite concentrations indicating an alternation of chemical weathering periods and physical weathering periods. Unit V (30.5-24.2 Ma) shows a further shift towards physical weathering. Unit VI (24.2-18.5 Ma) indicates strong physical weathering under a cold climate with persistent and intense illite formation. Unit VII (18.5 Ma to present) documents an additional input of smectite derived from the McMurdo Volcanic Group in the south.