ALBERT

Description: The mineralogy of the lower Oligocene (to possibly upper Eocene) sediments of core CRP-3 drilled on the continental shelf of McMurdo Sound in the Ross Sea, Antarctica, has been examined by the X-ray diffraction method. Quartz, plagioclase K- feldspar and pyroxene are the most important non-clay minerals. Amphibole occurs in minor amounts. The composition of the sediments points exclusively to an origin in the Transantarctic Mountains for the detrical components. There, the plutonic and metamorphic rocks of the basement, the sediments of the Beacon Supergroup and the volcanic rocks of the Ferrar Supergroup could serve as possible source lithologies. The distribution of the detrital minerals reflects a longterm history of successive erosion and beginning valley incision. During the deposition of the lowest part of the Cenozoic sediments of CRP-3, the majority of detrital minerals was probably derived from the sediments of the upper Beacon Supergroup (Victoria Group) and the Ferrar Supergroup, as indicated by the high quartz and pyroxene concentrations. Only a very minor proportion probably was contributed by basement rocks. From c. 620 to c. 420 mbsf the sandstone-dominated Taylor Group of the Beacon Supergroup probably acted as the main source rock and was responsible for maximum quartz concentrations and the strongly lowered feldspar and pyroxene amounts in the CRP-3 core. Above c. 420 mbsf the erosion in the valleys cutting through the Transantarctic mountains reached the level of the basement rocks and therefore the amount of basement-derived minerals like K-feldspar and amphibole in the CRP-3 sediments became more important.