Depositional Environment Analysis and the Relationship Between Sedimentary Facies and Diagenetic Processes in the upper deposits of the Dalan Formation, Central and Western Parts of the Qatar-Fars Arc
Subject Areas :L. Samadpour 1 , Hosein Mosaddegh 2 , B. Biranvandb 3 , H. Rahimpour Bonab 4 , A. Yahyaei 5
1 - Associate Professor, Department of Geology, Faculty of Erath Sciences, Kharazmi University, Tehran
2 -
3 -
4 -
5 -
Keywords: Upper Dalan, Diagenesis, Microfacies, Depositional Environment.,
Abstract :
The Dalan Formation of upper Permian age, is considered one of the most significant reservoir rocks in the Zagros region and the Persian Gulf. In this study, facies characteristics and influential diagenetic factors affecting facies variations are investigated in three wells from three fields in the western Qatar-Fars Arc. Based on microfacies analysis of 252 thin sections, eleven microfacies were identified, including massive to layer anhydrite, fabric fenestral dolomudstone, stromatolite bindstone, dolomitic mudstone, bioturbation mudstone, bioclastic wackestone/ packstone with green algae and benthic foraminifera, ooid/ ploid packstone to grainstone, ooid grainstone, intraclast/ bioclastic grainstone, bioclastic/ intraclast wackestone to packstone and bioclastic mudstone. These microfacies represent environments ranging from upper intertidal zones, lagoon, shoal, open marine, to mid-ramp settings. The gradual transition of microfacies, absence of large barrier reef structures, lack of turbiditic deposits, and presence of skeletal allochems such as benthic foraminifera, green algae, bivalves, brachiopods, and echinoderms indicate deposition in a homoclinal carbonate ramp platform. The study's findings reveal that diagenetic processes, including micritization, cementation, dissolution, neomorphism, dolomitization, and physical and chemical compaction, are observed across the studied intervals. These diagenetic processes occurred in four different settings: marine, meteoric, burial, and uplift and influenced the sediments throughout the eogenetic, mesogenetic, and telogenetic stages. Cementation is primarily associated with low-energy, intertidal facies but also occurs within high-energy facies, such as bioclastic packstone or ooid grainstone, which are characteristic of lagoonal and shoal environments.