Abstract

MOOSAVIZADEH, Seyed Mohammad Ali; ZAND-MOGHADAM, Hamed  and  RAHIMINEJAD, Amir Hossein. Palaeoenvironmental reconstruction and sequence stratigraphy of the Lower Cretaceous deposits in the Zagros belt, SW Iran. Bol. Soc. Geol. Mex [online]. 2020, vol.72, n.2, 00003.  Epub Dec 28, 2020. ISSN 1405-3322.  https://doi.org/10.18268/bsgm2020v72n2a060919.

Depositional environments and sequence stratigraphy of the Lower Cretaceous deposits of the Dariyan Formation were studied in the Zagros belt, SW Iran. The Dariyan Formation was investigated in the Interior Fars and the Izeh Zone in the SE margin of the Kazhdumi intra-shelf Basin, which has not been previously studied. Based on the benthic foraminifera, the Dariyan Formation is early Aptian to early Albian in age. The studies show that the Dariyan Formation was deposited in deep open-marine, shallow open-marine, shoal, and lagoonal settings on a homoclinal ramp. Three third-order depositional sequences (Ds1, Ds2, and Ds3) and three type 2 sequence boundaries (SB2) were recognized. The depositional sequences in the Dariyan Formation comprise three transgressive systems tracts (TSTs) and two highstand systems tracts (HSTs). During sea-level rise in the earliest Aptian, the Dariyan Formation was deposited on top of the the Barremian Gadvan Formation. Deep open-marine subsidence and sea-level rise led to deposition of radiolarian-bearing facies of the Dariyan Formation during the earliest Aptian. Subsequently, HSTs resulted in deposition of orbitolinid-rich facies in the deep open-marine setting (late early Aptian). Planktic foraminifera-bearing deposits were deposited during the subsequent sea-level rise (early late Aptian). Sea-level fall subsequently resulted in progradation of platform top (shallow open-marine, shoal, and lagoon) deposits into the deep open-marine setting (latest Aptian). Finally, sea-level rise resulted in deposition of the Albian Kazhdumi Formation on the Dariyan Formation during the early Albian. The sea-level changes recorded for the Dariyan Formation are consistent with Early Cretaceous sea-level patterns recognized else-where on the Arabian Plate.

Keywords : Facies; sequence stratigraphy; Dariyan Formation; Aptian- Albian; Zagros fold-thrust belt.

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