Quaternary sediments of the Shirokostan peninsula

Investigations on the Shirokostan Peninsula (the Laptev Sea coast) were carried out to solve the problem of genesis and paleogeographic conditions of the formation of Quaternary sediments in the NorthEast of Russia. Heteroghronous sediments were discovered in the reference section of the Etrykansky Yar. The relief is formed on the Middle Pleistocene sediments of the Kuchchuguj formation, on either side of which there are the Upper Pleistocene deposits of the Oyogos formation lying on the lower hypsometric level. The sediments of these formations differ in the amount of ice, the proportions of the polygonal wedge ice (PWI), that produces different in size and shape bajdzherahs after thawing. This could be a distinction when compiling a geomorphologic map of both the territory under study and all areas of ice complex occurrence. The sediments of the Oyogos formation inherited the granulometric and mineralogical composition of the Kuchchuguj deposits, indicating not far off re-deposition of the latter.

The alas complex is represented by formations of three ages (Kazancevsky, Karginsky and the Holocene), which are characterized by a similar structure. For the first time it became possible to trace the facial changes, cryogenic and post-cryogenic formations in Kazancevsky sediments, from the ice-covered areas with ice veins to totally melted ice complex with a system of pseudomorphoses. The freezing of all types of sediments was both syngenetic and epigenetic. Moreover, the alas deposits of the Kazancevsky age could freeze both from above and bottom-up if they were covered by sediments of the Oyogos formation. The age of the sediments is proved by their position, as well as by spore-pollen and macrofaunistic analyses. The absolute age of the sediments is determined by the dating of neighboring areas (the Oyogos Yar, Big Lyahovsky Island etc.) and coordinated with the data on other coastal lowlands of the Northeast Russia.

The results of spore-pollen analysis show well-defined climate changes during the Quaternary period. This is also confirmed by the occurrence of cryogenic and post-cryogenic formations in different genetic types of sediments.

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