REDEPOSITION OF THE MIDDLE MIOCENE DIATOMITES IN THE UPPER QUATERNARY SEDIMENT OF THE SOUTHERN SCOTTIA SEA (ANTARCTIC)

Abstract

The article is devoted to results of studying of siliceous microphytofossils from surface deposits of a southern part of the Scotia Sea (Western Antarctic). The micropaleontologic researches have allowed to detect presence of many redeposition valves of the Middle Miocene diatom species in the Upper Quaternary sediments of Site K97-18. On diatom data, the Core deposits have been divided into two intervals. The diatom assemblages consists of the Upper Quaternary species in the top interval (0-0,38 m), and the Upper Quaternary and the Middle Miocene species mixture in the bottom one (0,38-0,5 m). The age of Core sediments is 0-0,56 Ma (Thalassiosira lentiginosa zone). The top interval deposits were accumulated in the deep and open sea with an ice-cover in winter and a melt-stratified surface water in spring. The Middle Miocene frustules in diatom assemblages of Core bottom part are due to presence of a many little pieces of diatomite which are composed of the same species. It is the evidence of the Miocene diatomites redeposition in the Late Quaternary time.A drifting sea ice of the Last Antarctic Glaciation was the main transporter of terrigenous sediment in the Scotia Sea in Late Pleistocene. Temporary currents direction had shown ways of diatomite clasts migration and primary localisation of diatomite layers near the area of the Southern Orkney Islands, the Northern Antarctic Peninsula and subantarctic islands. The age of diatomite forming was defined as the Middle Miocene about 14.2-12.3 Ma (Denticulopsis simonsenii zone). On the analysis of the Miocene diatom assemblages and lithology of deposits it was determined the diatomite forming conditions. It was accumulate in an open deep sea without ice. Through the Antarctic Ice Sheet formation the amount of terrigenous material was a little. On the base of taxonomic composition of diatom assemblages the sources and ways of the Middle Miocene sedimentary matter were defined. This new information is important to the studying of the Antarctic Neogene-Quaternary deposition changes were induced by the global polar glaciation.