Lower Cretaceous Provenance and Sedimentary Deposition in the Eastern Carpathians: Inferences for the Evolution of the Subducted Oceanic Domain and its European Passive Continental Margin

摘要

Reconstructing orogenic systems made up dominantly by sediments accreted in trenches is challenging because of the incomplete lithological record of the subducted oceanic domain and its attached passive continental margin thrusted by collisional processes. In this respect, the remarkable similar to 600 km long continuity of sediments exposed in the Eastern Carpathian thin-skinned thrust and fold belt and the availability of quantitative reconstructions for adjacent continental units provide excellent conditions for a paleogeographical study by provenance and sedimentological techniques constraining sediment routing and depositional systems. These sediments were deposited in the Ceahlau-Severin branch of the Alpine Tethys Ocean and over its European passive continental margin. We report sedimentological, paleomagnetic, petrographic, and detrital zircon U-Pb data of Lower Cretaceous sediments from several thin-skinned tectonic units presumably deposited in the Moldavides domain of the Eastern Carpathians. Sedimentological observations in the innermost studied unit demonstrate that deposition took place in a deepwater basin floor sheets to sandy turbidite system. Detrital zircon age data demonstrate sourcing from internal Carpathian basement units. The sediment routing changes in more external units, where black shales basin floor sheets to sandy mud turbidites were sourced from an external, European continental area. Although some degree of mixing between sources located on both margins of the ocean occurred, constraining a relatively narrow width of the deep oceanic basin, these results demonstrate that the internal-most studied unit was deposited near an Early Cretaceous accretionary wedge, located on the opposite internal side relative to the passive continental margin domain of other Moldavides units.