Triassic deposits of Chukotka, Wrangel Island and Mendeleev Rise, Arctic Sea: sedimentology and geodynamic implications

摘要

Upper Triassic sandstones from Mendeleev Rise were analyzed and compared to turbiditic sandstones of the same age from Wrangel Island and Chukotka, Arctic Sea region. Medium-grained lithic arenites dominate all of these. The quartz content is higher in the sandstones from Mendeleev Rise than in those from Wrangel Island and Chukotka. Abundant quartz grains with microfractures and kaolinized feldspar are characteristic of the samples from Mendeleev Rise, whereas such features are lacking in the other areas. Quartz with microfractures is less abundant in Triassic turbidite sandstones of Chukotka and Wrangel and kaolinized feldspar is not present. Upper Triassic sandstones of Mendeleev Rise are characterized by a high Chemical Index of Alteration indicating intensive weathering in the source province. All sandstones have Th/Sc ratios <= 1. The chemical composition of sandstones suggests a quartzose sedimentary province for sandstones of Mendeleev Rise, an intermediate igneous province for Wrangel Island sandstones, and a mafic igneous provenance for Chukotka sandstones. Detrital zircon populations are similar in all Upper Triassic sandstones samples with a dominance of Paleozoic zircon. Facies studies of Triassic deposits in the Eastern Arctic of Russia indicate that sandstones from Mendeleev Rise were located near a continent and formed in a shallow or coastal-marine setting. Triassic deposits of Wrangel Island and Chukotka were deposited in a deeper marine environment.