The main tectonic events, depositional history, and the palaeogeography of the southern Urals during the Riphean-early Palaeozoic

摘要: Abstract Investigation of former and new sections in the classic Riphean region Bashkirian Anticlinorium (BA) revealed that this Palaeozoic segment passive margin East European Platform (EEP), during its Proterozoic history was initially formed as an intracratonic aulacogen basin which developed inter-cratonic half-structure only after Early Ordovician opening Uralian palaeo-ocean. The originally opposite may have been located either on Afro-European part Gondwana or along margins Siberian Craton, elsewhere, but definitely not conjugate Permian collision suture with Kazakh Block Mugodzhary microcontinent. ca. 1150 Ma (1635 to 488 Ma) depositional Basin punctuated several times due major tectonic events (folding, downfaulting, uplift, magmatic intrusions, metamorphism) caused extended periods erosion non-deposition. Furthermore, numerous cyclothems unknown regional extent are incorporated into enormous time span involved evolution 12–15-km-thick sequence. Riphean-Vendian sedimentary assemblages reflect alternating shallow-marine peritidal continental (fluviatile?) environments, distribution is illustrated sets palaeogeographic maps. Angular unconformities seen at base Lower Ai Formation (dated 1635 Ma), Middle Mashak 1340 Upper Zilmerdak (approx. 1000 below middle quartzites containing shelly fossils overlie steeply folded slightly metamorphosed suites southeastern Anticlinorium. During Vendian interval eastern parts well regions further north Urals were subjected strong diastrophism, probably related Cadomian Baikalian Orogeny. Later on, Ordovician, western half-part turned a marginal thus modified by early stages oceanic development.