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Structure and Mesozoic tectonics of the Southeastern Taimyr fold and thrust belt

Zastrozhnov D., Khudoley A., Verzhbitsky V.

Geology, Geophysics and Environment

2012

Vol. 38, no. 4

557--558

The Taimyr fold and thrust belt (FTB) consists of several zones that show evidence for Precambrian, late Paleozoic (Hercynian), and Mesozoic tectonic events. Most scientists point to Precambrian and late Paleozoic compression as the most intense event, although Zonenshain et al. (1990) argued for a strong Mesozoic tectonic event. Our studies of the Central and Southern Taimyr done in 2005-2012 in the frame of projects supported by the State geological mapping program and by TGS-NOPEC Company also points to important role of the Mesozoic tectonics. The main results are summarized in the following points: 1.The only clear angular unconformity in the sedimentary succession of the Central and Southern Taimyr is between Vendian and underlying rocks. Vendian-Triassic succession does not contain unconformities, although some hiatuses may occur. 2.Pre-Rhaetian unconformity (previously interpreted as pre-Jurassic) may be related to extension event as well as to compression event. 3.Folds in Cambrian up to Upper Permian rock units have very similar geometry. 4.In the eastern part of Southern Taimyr (Tsvetkova Cape area) Permian to Jurassic rocks show similar structural style. 5.Stress axes orientation estimated from the fracture study in Riphean rocks in the Central Taimyr and Permian up to Upper Jurassic sediments in the eastern part of Southern Taimyr (Tsvetkova Cape area) is very similar. 6.Apatite fission track study of samples from the Tsvetkova Cape area point to ca. 150—125 Ma and 75-60 Ma uplift/erosion events. 7.In the eastern part of Southern Taimyr all compression-related structures were affected by a younger extension. In summary, our observations do not show evidence for a strong late Paleozoic compression in the Central and Southern Taimyr. Granite intrusions, previously interpreted as Carboniferous, are ca. 250 Ma and may be presumably linked to the Norilsk trap LIP magmatic event. Also worth noting is that there are no Paleozoic ophiolite complexes within Taimyr FTB. Similarity in fold geometry and stress axes orientation shows that Vendian and younger rocks up to Permian in the Central Taimyr as well as Permian and Mesozoic rocks of the Southern Taimyr were mainly deformed during Mesozoic (Early and/or Late Cretaceous) compressional event, also recognized by brittle fractures in the Riphean rock units. These events are approximately synchronous to major collisional processes occurred in latest Jurassic-Cretaceous time in the northeast Asia and may reflect a connection between Southern Taimyr and Mesozoic fold belts of the northeast Asia. The final extension best documented in the Tsvetkova Cape area likely reflects tectonic relaxation processes right after the compressional event and opening of the Laptev Sea rifted sedimentary basin in Late Cretaceous-Cenozoic.