Clay mineralogy of sediment core CRP-1

Clay mineral assemblages in lower Miocene and Quaternary sediments recovered at the CRP-1 drillsite, McMurdo Sound shelf, Antarctica, were analysed in order to reconstruct source areas of the sediments and late Cenozoic Antarctic icedynamics. The assemblages are dominated by smectite, illite and chlorite. Kaolinite occurs in trace amounts only. The lower part of the drillcore, below c. 70 mbsf, is characterised by high illite and chlorite, but low smectite concentrations. This assemblage is typical of a source consisting mainly of granitic and metamorphic rocks, such as are widespread in the Transantarctic Mountains and on the East Antarctic craton. In contrast, the upper c. 70 mbsf of the core is characterised by three intervals with high smectite, but low illite and chlorite concentrations at around 59, 45 and 33 mbsf. The smectite-rich assemblage is typical of a hinterland composed of volcanic rocks, such as are found in the region of the present-day Ross Ice Shelf. The clay minerals are mainly detrital and therefore document the changing influence of different source areas through time. Correlation of the clay mineral record of CRP-1 with that of the CIROS-1 and MSSTS-1 cores implies that the oldest sediments at CRP-1 are younger than 21.8 Ma, and that there is no overlap between CRP-l and the other cores.