Sedimentary Environment and Sequence Stratigraphy of the Lower Cretaceous Deposits in the Bideshk Area, at North of Esfahan, Iran

Abstract

Background/Objectives: Rocks of the Mesozoic era in Iran, especially Cretaceous period, have been studied frequently from stratigraphic point of view, but little research has been done from sedimentology viewpoint. This study aims to restore the sedimentation condition and the conditions governing the sedimentary basins during that period (lower Cretaceous). Methods: One stratigraphic section was measured along the outcrop in Bideshk Area, at North of Esfahan. 63 thin sections samples were studied to determine the facies and a polarized microscope was used for the procedure. Findings: Based on lithological properties, 3 lithostratigraphic units have identified in the area. Facies analysis and field observations led to identification of 10 carbonate facies, 4 terrigenous facies and also 4 mixed (terrigenous and carbonate). Bideshk area was deposited on a homoclinal ramp setting within four zones including Continental, tidal flat, lagoon and bar environments. Sequence stratigraphic analysis identified three third-order depositional sequences in the studied area. Lower boundary in the first sequence is unconformity first-type boundary (SB1) (with Jurassic deposits) and consists of Transgressive Systems Tract (TST). Sequence number 2 consists of Low stand Systems Tract (LST), Transgressive Systems Tract (TST) and High stand Systems Tract (HST). Sequence 3 also consists of LST, TST and HST. Application: These results could be used for comparison with other worldwide localities and provide additional data for lower Cretaceous paleogeographic reconstructions.