Microfacies and stable isotope analysis of Kuldhar Member Limestone (Callovian–Oxfordian), Jaisalmer Basin, western Rajasthan: implications for depositional environment and diagenetic evolution

• Published in: Carbonates and evaporites Vol. 38; no. 4; p. 81
• Main Authors: Asjad, Shaikh, Khan, K. F., Quasim, M. A., Sachan, H. K., Javed, Aashna
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.12.2023; Springer Nature B.V
• Subjects: Algae; Calcite; Carbon 13; Carbonates; Cementation; Compaction; Corals; Diagenesis; Dissolution; Dissolving; Earth and Environmental Science; Earth Sciences; Foraminifera; Fossils; Fractures; Fracturing; Geology; Grain size; Isotopes; Jurassic; Lagoons; Limestone; Marine environment; Marine invertebrates; Marine molluscs; Mineral Resources; Mineralogy; Mollusks; Ooids; Original Article; Palaeogeography; Reservoirs; Shellfish; Shoals; Stable isotopes; Veins (geology); Jaisalmer Basin; Stable isotope; Microfacies analysis; Reservoir quality; Kuldhar member; Diagenetic evolution
• ISSN: 0891-2556; 1878-5212
• DOI: 10.1007/s13146-023-00905-6

Microfacies, diagenesis, and stable isotope analysis of Kuldhar Member Limestone (KML) has been carried out to reconstruct the depositional environment and palaeogeography as well as to evaluate the influence of diagenesis on its reservoir quality. The KML is characterized by thin bedding, a high abundance of fossils, and fine to medium grain size. The grains range from angular to well rounded and vary in their sphericity. The KML is composed of diverse array of skeletal grains such as brachiopods, echinoderms, bivalves, gastropods, corals, foraminifera, and bryozoans, as well as non-skeletal grains such as intraclasts, ooids, and peloids, with poor to well-sorted nature. Twelve microfacies were identified in the KML based on detailed petrographic studies, which are echinoderm grainstone (MF1), coated bioclastic grainstone (MF2), oncoid grainstone (MF3), oolitic wackestone (MF4), peloidal wackestone (MF5), ooidal grainstone (MF6), algal packstone (MF7), aggregate-grain grainstone (MF8), bioclastic packstone (MF9), bioclastic lithoclastic packstone (MF10), whole fossil wackestone (MF11), and bioclastic rudstone (MF12). The KML was deposited in shoal, lagoon, and open marine environments and inferred to be a product of fluctuating sea level and varying energy conditions which include shallowing as well as deepening of the sea throughout the deposition. Micritization, cementation, physical and chemical compaction, dissolution, fracturing, neomorphism, and precipitation of calcite veins in some fractures are the main diagenetic processes affecting the KML. The investigations of diagenetic aspects and stable isotopes (δ 13 C and δ 18 O) show that the KML was influenced by early marine, meteoric, and burial diagenesis. Micritization, cementation, neomorphism, physical compaction, and precipitated calcite veins had a detrimental effect on the reservoir quality. On the other hand, dissolution, fracturing, and chemical compaction had a positive impact and enhanced the reservoir quality, making the rocks conducive to hydrocarbon accumulation. This study could point to a potential carbonate resource and aid in future exploitation of the under-explored Jurassic carbonates in the Jaisalmer Basin.