Controls on the sequence stratigraphic architecture of the Neogene Zagros foreland basin

Abstract

We investigated the sequence stratigraphic architecture of Neogene deposits in the Zagros region using 12 measured stratigraphic sections and performing strontium isotope measurements on 10 samples. We combined our data with 44 previous published Sr isotope measurements and five paleomagnetostratigraphic sections in order to place the foreland deposits in a chronostratigraphic framework. Two chronostratigraphic charts were created, and transgressive-regressive system tracts were identified in the western and eastern sectors of the Zagros. These results show that the southward migration of the Zagros fold-and-thrust belt led to broadly upward-coarsening, progradational sequences due to progressive uplift and seaward (southwestward) migration of the Zagros fold-and-thrust belt. In addition, we show distinct differences in the sequences between the eastern and western sectors. It can be inferred that, in the strike-parallel direction, the Zagros foreland basin did not respond in a simple manner to tectonics and global sea-level changes during the Neogene. The different architecture of the sequences and mismatch of Neogene sedimentary architecture with global sea-level curves imply different orogen-parallel evolutionary histories and strong impact of tectonics on the basin evolution as compared to eustasy. Finally, we present evidence for a retrogradational sequence related to a period of enhanced deformation and related crustal thickening during the middle Miocene in the eastern Zagros.

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