Smectite Crystallinity and Composition in Pliocene-Pleistocene Sediments at the Continental Rise (ODP Site 1165), Prydz Bay, Antarctica
J. Junttila1,2* & K. Strand2
1Department of Geosciences, P.O. Box 3000, FIN-90014 University of Oulu - Finland
2Thule Institute, P.O. Box 7300, FIN-90014 University of Oulu - Finland
Received 18 October 2005; accepted in revised form 16 May 2006
Abstract - The main objective of this study was to provide information about the origin of smectite in Ocean Drilling Program (ODP) Site 1165 Pliocene-Pleistocene sediments from the continental rise off Prydz Bay. Crystallinity measurements and scanning electron microscope (SEM) analysis were used to study smectite composition. The smectites are flaky and detrital throughout the Pliocene-Pleistocene aged interval (0-50 mbsf). Smectite crystallinity is moderate to poor in the Pliocene sediments, but good to very good in the Pleistocene sediments. The smectites from the selected intervals of Plio-Pleistocene transition and the Mid-Pliocene are all dioctahedral and can be classified as Al-Fe smectites or ferriferous beidellites. They have been derived predominantly from East-Antarctic continental sources similar to the Battye Glacier Formation and transported to the final depositional site mainly by bottom currents during interglacials, especially during the Mid-Pliocene period of global warmth. The smectites in Pleistocene sediments sho higher crystallinity than those in Pliocene sediments. This may indicate a more restricted source and probably glacially eroded and reworked clay components transported from the continental shelf to final depositional site.
*Corresponding author (juho.p.junttila@oulu.fi)