Gravitational Collapse of Anteclises and Its Probable Impact on the Neotectonics of Platforms and Passive Continental Margins (by the Example of the East European Platform)

Abstract

Abstract —Structural and geological research has shown that the extension of the Russian Plate caused a neotectonic transition of the deformed material from the Voronezh and Volga–Kama anteclises to neighboring syneclises, primarily the deepest Peri-Caspian syneclise. The resulting geologic structures and landforms morphologically resembled landslides, but their large (up to many hundreds of kilometers) lateral sizes excluded the influence of exogenous processes and made it necessary to treat this event as a gravitational collapse involving a significant crustal mass. This phenomenon was previously considered for orogens only, but the conditions for its appearance here existed too: In the late Cenozoic, the East European Platform experienced a collisional pressure from the southern boundary of the Eurasian Plate, which led to a gravitationally unstable uplift. The collapse was best manifested in the zones of junction of anteclises and syneclises, where lenses of the thickened continental crust are thinned beneath anteclises. This fact, along with the published modeling data, gave grounds to state that the platform collapse was favored by the lenticular crustal structure: The light crustal lenses forming anteclises floated up under compression and diverged under subsequent decompression. Gravitational extension and subsidence in the anteclise apexes was compensated by compression near the syneclises, where folded dislocations and neotectonic ramparts formed. It has been established that a gravitational collapse results in a specific paragenesis of platform structures and morphostructures, which can help to identify its manifestations in other places and to estimate the relationship between the relief formation and tectonics. In general, the data obtained suggest a relationship between the recent activity of passive continental margins and the gravitational collapse of the largest lenses of the continental crust.