Analiza tempa depozycji materiału detrytycznego w basenach sedymentacyjnych zachodnich Karpat zewnętrznych jako wskaźnik aktywności tektonicznej ich obszarów źródłowych

Abstract

Tectonic activity of sediment source areas for theWestern Outer Carpathian basins—constraints from analysis of sediment deposition rate.S u m m a r y. Analysis of deposition rate were performed for synthetic sections, representing the upper Jurassic to lower Miocene sedimentary fill of the Western Outer Carpathian (WOC) basins. Calculated deposition rates differs in a range of a few orders of magnitude. During Tithonian to Berriasian-early Valanginian tectonic activity of the source areas supplying the Silesian Basin was related to the mechanism of syn-rift extensional elevation and erosion of horsts. General decay of source area activity in Valanginian to Cenomanian time was caused by regional post-rift thermal sag of the WOC. The Barremian to Albian phase of compressional uplift of the source area located north of the WOC lead to increase of deposition rate in some zones of the WOC basin. In Turonian to Paleocene time thick-skinned collision and thrusting took place south and south-west (in the recent coordinates) of the Silesian Basin causing very rapid, diachronous uplift of this zone, referred to as Silesian Ridge, resulting with high deposition rate in the Silesian Basin. At that time supply of sediments to the Magura Basin from south was relatively low, and the Pieniny Klipen Belt was presumably zone of transfer of these sediments. In Eocene the zone of collisional shortening in the WOC system was relocated to the south, causing rapid uplift of the Southern Magura Ridge and intense supply of detritus to the Magura Basin. Thrusting in the Southern Magura Ridge and collisional compression resulted with flexural bending of its broad foreland, being the reason for decrease of activity of both the Silesian Ridge and the source area at the northern rim of the WOC. The Eocene evolution of the Silesian Ridge is interpreted as controlled by both episodic tectonic activity and eustatic sea level changes. Contrasting development of the Southern Magura Ridge and the northern rim of Central Carpathians during Eocene stands for a palaeographic distance between the two domains at that time. During Oligocene and early Miocene a significant increase of deposition rates is observed for the basin in which sediments of the Krosno beds were deposited. This was caused by tectonic uplift of the source at the northern rim of the WOC, as well as the Silesian Ridge and the partly formed Magura nappe. The Miocene molasse of the WOC foredeep basin is characterised by notably higher maximum deposition rates than ones calculated for the flysch deposits of the WOC.