Mineral assemblage of basement clasts of sediment core CRP-1

Heavy minerals from the lower Miocene and Quaternary sediments of the CRP-1 drillcore have been investigated in order to characterise the mineralogical composition of the sediments and to reconstruct their source areas. The sediments are dominated by very high concentrations of pyroxenes. Hornblende, stable heavy minerals (zircon, garnet, epidote. titanite and apatite), opaque and altered minerals are quantitatively minor. The downcore distribution of the pyroxenes indicates 5 cycles. Each cycle starts with diamictites and proximal glacimarine sediments containing maximum concentrations of pyroxenes of up to 80% in the heavy mineral fraction, and grades into distal glacimarine sediments, with a lower pyroxene content. The heavy minerals indicate a mixed source for all CRP-1 sediments. The proximal sediments consist mainly of minerals derived from a crystalline basement and clastic sedimentary rocks, such as are widespread in the Transantarctic Mountains. However, they also contain a minor component derived from volcanic rocks. The distal sediments, in contrast, are dominated by a volcanic source, which was probably situated to the south of the drillsite, in the region of the present-day Ross Ice Shelf.