Modal analyses of thin-sections of sediment core CRP-1 (Table 1)

During the course of the 1997 drilling campaign, lithostratigraphic boundaries were assigned to the CRP-l core on the basis of perceived changes in lithology. The geologically most important boundary in the core, between the Miocene and overlying Quaternary sections, was placed at 43.55 mbsf. This horizon was described in the core logs (Cape Roberts Science Team, 1998) as a contact between muddy, finegrained sandstone (which were assigned a Lower Miocene age based on diatom biostratigsaphy) and overlying diamictons containing Quaternary diatoms. This boundary is a major unconformity, recognisable on seismic reflection records. As such, it has considerable significance in the ongoing scientific analysis of the drillcore. During a re-examination of the core, focusing on the archive half held at the Antarctic Geology Research Facility of the Florida State University at Tallahassee; the authors noted that the core across the published boundary (43.55 mbsf) did not show any lithological change, but logged a sharp contact between dark olive grey, muddy sandstone and overlying diamicton at 43.15 mbsf (Fig. l). We suggest, therefore, that the core log in appendix l of Cape Roberts Science Team (1998) is misleading over this interval. In order to test the veracity of the suggested boundary revision, a series of thin-sections was examined and point-counted for framework grain abundances.