LATE PRECAMBRIAN TILLITES OF BOLSHOY KARATAU: COMPOSITION AND AGE OF THE SOURCES OF DETRITAL MATERIAL
K.K. Kolesov1, E.F. Letnika1, A.V. Ivanov1, S.I. Shkolnik2, A.A. Zhdanov1
1Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
2Institute of the Earth's Crust of the Siberian Branch of the Russian Academy of Sciences, Irkutsk, Russia
Keywords: Tillites, Karatau-Dzhebagli block, Bolshoy Karatau, Kosshokinskaya Formation, Ulutau Series
Abstract
The definition of glacial deposits (tillites) in Precambrian sections is a difficult task due to the frequent similarity of their composition and structure with other sedimentary rocks. This is due to the fact that Precambrian sediments have been losing their inherent geomorphological and lithological features over their long history. Tillites are important markers of climate change and are widely used in stratigraphic correlations and geodynamic reconstructions. The research in this article is aimed at studying tillites within the Bolshoy Karatau ridge in order to substantiate the composition and age of rocks on the eroded surface during the movement of ancient glacier. The age values of detrital zircons from the tillite matrix form the main intervals of 740-856 million years (32 grains), 1950-2040 million years (14 grains) and 2200-2630 million years (26 grains) with age peaks of 765, 835, 924, 2030 and 2435 Ma. The following ages were obtained for boulders from the tillite horizon: 746±4 million years (9 grains); 778±4 million years (9 grains); 746±3 million years (13 grains); 788±3 million years (16 grains). The obtained dates for boulders from the tillite horizon have similar age analogues within the Middle Tien Shan, Karatau-Talas, Zheltau, Chu-Kendyktas, and Ulutau blocks.
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