Provenance and palaeogeography of uppermost Triassic and Lower Cretaceous terrigenous rocks of central Iran: Reflection of the Cimmerian events

Abstract

The “Jurassic Gap” between Upper Triassic and Lower Cretaceous siliciclastic strata at the southwestern margin of the Central East Iranian Microcontinent (CEIM) represents the Cimmerian orogenic events. However, the provenance of siliciclastic rocks above and below this prominent unconformity is poorly known, negatively affecting our ability to reconstruct paleogeography and orogenic dynamics. Here, we analyze the provenance of the uppermost Triassic Qadir Member of the Nayband Formation and the red beds of the Lower Cretaceous siliciclastic succession in central Iran, based on conglomerate clast composition, sandstone modal analysis and sandstone geochemistry. Based on the notable compositional variation, we assign the Qadir Member to a transitional continental-tectonic setting and the red beds of the Lower Cretaceous siliciclastic rocks to a recycled-orogen setting. Geochemical analyses shows that the parent rocks of the Qadir Member were intermediate igneous, felsic and metamorphic rocks; and were sedimentary quartz, felsic igneous and metamorphic rocks for the Lower Cretaceous red beds. The modal analysis also indicates semi-humid weathering conditions in the Late Triassic but more humid conditions during the Lower Cretaceous which the strata were largely influenced by the deposition of recycled Jurassic sediments. We infer the Sanandaj–Sirjan Zone (SSZ) to the south to be the main provenance region for both stratal packages. © 2018 E. Schweizerbart’sche Verlagsbuchhandlung, Stuttgart, Germany.