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The Sicilian Thrust System (STS) is a south-verging (Africa-verging) fold-and-thrust belt including a Mesozoic-Paleogene sedimentary sequence. This thrust stack owes its origin to the deformation of pre-orogenic strata deposited in different palaeogeographic domains belonging to passive margins of the African plate. The STS was deformed during the Neogene, following the closure of the Tethys Ocean and the continental collision between the Sardo-Corso Block and the north Africa margins. The thrust pile was detached from the underlying basement during the Miocene-Pleistocene. The regional-scale structural setting recognized allows us to reconstruct the tectonic evolution of the STS as follows: I - piggy-back thrusting from the Late Oligocene to the Langhian, inducing the building of the Inner Sicilian Chain (ISC); II - piggy-back thrusting from the Langhian to the Tortonian, inducing the formation of the Middle Sicilian Chain (MSC); III - generalized extensional deformation in the chain-foredeep-foreland system from the Tortonian to the Early Pliocene; IV-a new onset of piggy-back thrusting after the Early Pliocene allowed the building of the Outer Sicilian Chain and out-of-sequence thrusting in the previously developed ISC and MSC.
Although no undoubted oceanic crustal rock complexes of Penninic affinity participate in the present surface structure of the Western Carpathians, indirect lines of evidence suggest prolongation of the South Penninic-Vahic oceanic tract into the ancient Carpathians. The sedimentary record of both the syn-rift and syn-orogenic clastic deposits reveal their origin between the outer Tatric (Austroalpine) and the inner Oravic (Middle Penninic) margins. The rifting regime is exemplified by the normal fault-related scarp breccias of the Jurassic Borinka Unit in the Male Karpaty Mts., which are characterized by local, gradually denuded source areas. Two other regions provide examples of a contractional regime, both related to shortening and closure of the Vahic oceanic domain. The Belice Unit in the Povazsky Inovec Mts. includes Upper Jurassic-Lower Cretaceous eupelagic, mostly siliceous deposits and a thickening-upwards Senonian sequence of turbiditic sandstones, conglomerates and chaotic breccias. It is inferred that this succession represents the sedimentary cover of oceanic crust approaching a trench, its incorporation in the accretionary complex and finally underthrusting below the outer Tatric margin. In the Oravic units of the Pieniny Klippen Belt, deep-marine conglomerate/breccia bodies with olistoliths indicate collision-related thrust stacking that started from the Maastrichtian (Gregorianka Breccia of the Sub-Pieniny Unit) and terminated with the Lower Eocene Milpos Breccia in the Saris Unit. In addition, a tentative recycling scheme of “exotic” clastic material from mid-Cretaceous conglomerates of the Klape Unit to various Klippen Belt units is outlined. This material is considered to be unrelated to the Vahic oceanic realm and its closure, and likely represents erosional products of more distant orogenic zones.
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