Diagenesis processes of carbonate deposits of Shahbazan Formation (Sarkan anticline, South Lorestan)

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Abstract

The Shahbazan Formation is of middle to late Eocene age and extends over a wide area of ​​the Lorestan sedimentary basin. The studied area is located 75 km south of Khorram Abad city. In the studied area, the Shahbazan F ormation with thicknesses of 73 meters is placed on the Keshkan clastic formation as a slope and is discontinuously covered by the carbonates of the Asmari F ormation. The lithology of Shahbazan Formation in the studied section includes carbonate rocks, dolomitic carbonate rocks and dolomite. Petrographic studies on 63 thin sections led to the identification of several diagenesis processes, including micritization, neomorphism (increasing and decreasing), cementation (including isopachous rim cement , syntaxial , epitaxial , equant, blocky, dru s y and poikilotopic ), compression (mechanical, chemical), dissolution (dependent and independent of the fabric), replacement ( hemmatitization , silicification and dolomitization). The most important diagenesis process in Shahbazan Formation is dolomitization, which has occurred widely. These processes occurred in four paragenetic sequences (marine environment, fresh water, burial and uplift) and three stages of diagenesis e ogenesis, m esogenesis and t elogenesis have been interpreted for them. The reduction process of neomorphism has occurred in the stage of eugenesis and in the marine region . Isopachous rim cement and epitaxial cement are formed in the eugenesis stage and in the marine diagenesis region, while blocky, equant and poikilotopic cements are formed in the mesogenesis and telogenesis stage and in the region of shallow and deep burial diagenesis. The compression in eugenesis was created by the overburden pressure caused by the Shahbazan F ormation and then developed by the Asmari and Gachsaran formations. Part of the dissolution occurred during burial diagenesis and another part occurred during uplift and impact of meteoric diagenesis.

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History

  • Receive Date: 29 September 2023
  • Revise Date: 16 October 2023
  • Accept Date: 21 October 2023

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