Provenance of the Neoproterozoic and Upper Paleozoic Siliciclastic Complexes of the Eastern Taimyr: Petrographic, Geoche
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enance of the Neoproterozoic and Upper Paleozoic Siliciclastic Complexes of the Eastern Taimyr: Petrographic, Geochemical, and Geochronological Data N. S. Priyatkinaa, b, *, A. K. Khudoleya, and A. V. Kuptsovaa aSt.
Petersburg State University, St. Petersburg, 191023 Russia b The University of Newcastle, Newcastle, Australia *e-mail: [email protected]
Received October 1, 2019; revised March 26, 2020; accepted May 17, 2020
Abstract—The results of petrographic, geochemical, and isotopic studies of the Neoproterozoic and Upper Paleozoic sandstones of the Eastern Taimyr complement the available data on their genesis and confirm their molassic origin. The sandstones and mudstones of the Neoproterozoic Stanovaya and Posadochnaya formations formed mostly from the erosion products of the magmatic and metamorphic complexes with ages of ~970–800 Ma and from older siliciclastic rocks. The Upper Paleozoic sandstones of the Byrranga, Sokolinaya, and Turuza formations are characterized by a somewhat lower degree of maturity. Most of them formed from erosion products of magmatic and metamorphic complexes with ages of ~500 and ~300 Ma, although sediments sourced from an older provenance were also encountered. The ages of the youngest detrital zircon grains from the Upper Paleozoic sandstones are close to the depositional ages in some cases and differ by more than 100 m.y. in other cases. This suggests that one should be cautious about using the maximum depositional ages for establishing the tectonic setting of sedimentary basin formation. Keywords: Arctic, Taimyr, Neoproterozoic, Paleozoic, sandstone, molasse, detrital zircon DOI: 10.1134/S0869593820060088
INTRODUCTION Siliciclastic rocks contain important information about the sources of detrital material supply and tectonic settings that existed during their accumulation. Various aspects of the tectonic interpretation of their mineral, geochemical, and isotope composition are discussed in the vast literature (e.g., Cawood et al., 2012; Dickinson et al., 1983; Gehrels, 2012, 2014; McLennan et al., 1993, 2003; Maslov et al., 2015, 2016). Consisting of destruction products of the growing Taimyr fold and thrust (orogenic) belt, the Neoproterozoic and Upper Paleozoic–Mesozoic siliciclastic sequences, which are enclosed in the belt and are usually classified as molasses (Vernikovsky, 1996), are important sources of information about the age and composition of its constituent blocks. This, in its turn, can be used for testing or updating paleogeographical reconstructions involving the Taimyr orogenic belt and for the adjustment of its geological relations with the other large tectonic structures (e.g., Pease et al., 2001; Vernikovsky et al., 2013). The Taimyr orogenic belt surrounds the Siberian Craton from the north (Fig. 1a) in such a way that the westward extension of the orogen is apparently hidden beneath the Barents Sea. It is possible that the Taimyr
orogenic belt is an independent geological structure. At the same time, a number of geophysical and geological data
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