Age and Stratigraphic Position of Sedimentary Sequences of the Bagrush Mountains (Southern Urals) Based on the Results o
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Age and Stratigraphic Position of Sedimentary Sequences of the Bagrush Mountains (Southern Urals) Based on the Results of U–Pb Dating (LA–ICP–MS) of Detrital Zircons T. V. Romanyuka, N. B. Kuznetsovb,c, f*, Corresponding Member of the RAS V. N. Puchkovd, N. D. Sergeevae, V. I. Powermana,f, V. M. Gorozhanine, and E. N. Gorozhaninae Received March 13, 2019; revised May 19, 2020; accepted May 21, 2020
Abstract—In order to determine the provenance and age of terrigenous-carbonate stratified units exposed in the region of Bagrush Mountains, Bashkirian uplift, U–Pb dating of detrital zircons from these units has been carried out. A comparison of the data results with analogous data on five stratigraphic levels within the Riphean section of the Bashkirian uplift has shown that the studied sequence should be, most likely, correlated to the uppermost Lower Riphean or the lowermost Middle Riphean. Keywords: Southern Urals, Bagrush Mountains, Riphean, detrital zircons, U–Pb dating DOI: 10.1134/S1028334X20080188
In the western part of the southern epi-Paleozoic Uralian thrust-and-fold belt, an extensive outcrop of Precambrian rocks—the Bashkirian mega-anticlinorium (BMA)—is located [8, 15]. In its eastern part, hereinafter referred to as the Bashkirian uplift (BU), Upper Precambrian sequences are widespread; the integrated sections of these sequences—Burzyan, Yurmaty, and Karatau series—are assumed to be stratotypical sequences of the Early, Middle, and Upper Riphean, respectively [7, 14, 15] (Fig. 1). In the northern BU, within the areas to the west of the town of Kusa (in the Bagrush Mountains, in the interfluve of the Bolshoi and Malyi Bargrush rivers, and further to the southwest along the Kalgan-Salgan Range), Upper Precambrian terrigenous and carbonate rocks are widespread (Fig. 2). The stratigraphic position of this sequence has long been debated. In the a Schmidt
Institute of Physics of the Earth, Russian Academy of Sciences, Moscow, 123995 Russia b Geological Institute, Russian Academy of Sciences, Moscow, 119017 Russia c Gubkin Russian State University of Oil and Gas, Moscow, 119991 Russia d Zavaritsky Institute of Geology and Geochemistry, Ural Branch of the Russian Academy of Sciences, Yekaterinburg, 620016 Russia e Institute of Geology, Ufa Federal Research Center, Russian Academy of Sciences, Ufa, 450077 Russia f Institute of the Earth’s Crust, Siberian Branch, Russian Academy of Sciences, Irkutsk, 664033 Russia *e-mail: [email protected]
medium-scale geological maps compiled by M.I. Garan’ in the late 1950s and early 1960s, layered sequences of this area had been referred to the Avzyan Formation of the uppermost Yurmaty series. In the modern medium-scale geological maps [1, 6], these rocks are referred to the Satka Formation from the middle part of the Burzyan series. Finally, in the modern map of the scale of 1 : 1 000 000 [2], these units are included in the Zil’merdak Formation of the lowermost Karatau series. In the northern Bagrush Mountains, the stratified sequences mentioned are intruded by vein-
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