Introduction to the Khalij Limestone Member Type Section in the Gadvan Formation of Iran: A Comprehensive Analysis Utilizing 38 Exploration and Development Wells and 1 Surface Section of Gadvan

Abstract

The Khalij limestone member, well-known for its abundant benthic facies, is situated in the middle segment of the Gadvan shaly formation, boasting an average thickness of approximately 14 meters. This specific member is exclusively found below the surface, devoid of any exposed outcrops, and is characterized by the presence of easily identifiable orbitolinid limestone. Well logging techniques, such as Gamma Ray and Density measurements, prove particularly effective in identifying this distinct layer. The primary objective of this study was to conduct a comprehensive analysis of the lithostratigraphy and microstratigraphy within the Gadvan formation, with a specific emphasis on the Khalij limestone member. A regional stratigraphic assessment covered an extensive area of about 100,000 square kilometers in the Fars and Dezful regions within the Zagros region. To achieve this, data from 38 exploration and development wells were utilized, and approximately 1,400 microscopic thin sections from the Gadvan formation were meticulously examined. The paramount contribution of this research lies in the establishment of a representative type section for the Khalij limestone member, characterized by a thickness of 13 meters. Detailed microscopic analysis has revealed that this member predominantly comprises wackestone carbonate, featuring microfossils, particularly foraminifera from the orbitolindae family. Based on the observed species index, it has been determined to be of Barremian age and linked to a lagoon-like depositional environment.