(Table 1) Detrital modes for sand grains in sediment core CRP-2/2A

Dynamic provenance variations are deduced from sand-grain detrital modes in samples obtained from the CRP-2/2A drillcore. Below an important unconformity at 307 metres below sea floor (mbsf), sand grains in most of the sequence were dominantly derived from Beacon sandstone and Ferra dolerite sources, although alternating with subordinate thicknesses of strata derived from a predominantly granitoid source (Granite Harbour Intrusive Complex; GHIC). Above the 307 mbsf unconformities, the reverse situation occurs, with most sediments dominantly sourced in the GHIC. Contributions from other sources (e.g. Jurassic Kirkpatrick basalt lavas and Proterozoic metamorphic basement) are also persistent but minor. An input of fresh volcanic detritus commenced at 307 mbsf and is ubiquitous in all the younger sediments. At least three (probably four) episodes of volcanism are identified, each lasting 1-2 M.yr in duration. The initial influx at 307 mbsf corresponds to the initiation of the McMurdo Volcanic Group (MVG) at c. 25 Ma and is much younger than estimates made previously by other workers for the oldest MVG volcanic activity in the McMurdo Sound region (Eocene?). Simultaneous major changes in the proportion of clast lithologies in CRP-2/2A suggest that the 307 mbsf unconformity is the most important petrological break within the cored sequence. It is speculated that the petrological contrasts across the unconformity are genetically associated with important climatic changes and/or rapid uplift episode(s) in the Transantarctic Mountains