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The middle Eocene Fulra Limestone Formation of the Kachchh Basin, western India was investigated to interpret depositional environments and sources of limestones based on facies analysis, mineralogy, and major, trace, and rare earth elements (REEs) geochemistry. Facies stacking pattern of the Fulra Limestone Formation exhibits an overall shallowing‐upward sedimentary succession developed in the middle to inner ramp to lagoonal set‐up. Staining of the thin sections and X‐ray diffraction patterns show dominance of calcite mineral. The CaO, ranging from 40.45% to 49.69%, is the dominant oxide among the major oxides followed by SiO2 (4.04–10.3%). The dominance of CaO over MgO suggests that the major mineral phase has been calcite and no dolomitization occurred during the deposition of the Fulra limestone. The low proportion of SiO2 and Al2O3 suggests low siliciclastic input during the precipitation of the Fulra limestone that is confirmed by the positive correlation of ∑REE with Al2O3, Fe2O3, Ni, Th, Sc, and Y and the negative correlation of SiO2, Al2O3, and Sr with CaO. The average value of REE contents in the Fulra Limestone Formation are lower (*16.02 ppm) than the average value of typical marine carbonates (*28 ppm). The Post‐Archean Australian Shale‐normalized REE + Y patterns of the Fulra limestone exhibit seawater like shale‐normalized REE + Y pattern, whereas slightly lower average value of Y/Ho ratio (34.60) than the typical seawater value (~44–74) suggests modification of the seawater, to some extent, by input of freshwater in a coastal environment. The REEs of the Fulra Limestone Formation have similarity with the carbonates of the Arabian Sea and/or shallow marine carbonates with exception of a few elements. It is envisaged from this study that the Fulra limestone was deposited in a shallow marine to coastal set‐up where mixing of the continental material in seawater was feasible. [ABSTRACT FROM AUTHOR]

The Al-Jawf area of northern Saudi Arabia provides spectacular outcrops of Early Devonian carbonate bioherms in the Wadi Murayr and Dumat Al-Jandal areas. These carbonate bioherms belong to the Qasr Member of the Late Pragian-Early Emsian Jauf Formation (~405 Ma) and are surrounded by a bioclastic carbonate succession. The Qasr Member is the first major carbonate unit of the Palaeozoic succession in Saudi Arabia that mainly consists of microbialite carbonates and metazoan reefs exhibiting distinct mound features. These bioherm complexes and their associated carbonate facies are pervasively dolomitized. Stratigraphic, petrographic and geochemical analyses were conducted to determine the facies distribution and interpret their depositional and diagenetic processes. A total of 11 facies are identified from a range of depositional environments within a carbonate platform system, ranging from tidal flats, lagoon, shoal, patch reefs to reef front. The main diagenetic processes are carbonate cementation and dolomitization. Dolomitization occurred as both fabric preserved (mostly in grain-dominated facies) and fabric destructive (mud-dominated facies). The microbialites and coralline sponges facies show poor reservoir with visual porosity less than 5%, but this succession may have a potential to serve as a good source for the underlying and overlying facies. Ooid and peloidal grainstone facies show fair to good visual porosity that locally exceeds 10% with intergranular porosity as the dominant type. However, in the most studied samples, vuggy and intraparticle porosities are observed as the dominant type. [ABSTRACT FROM AUTHOR]

The article reports on the meganodular limestone in South China. It highlights time-specific facies-based three-dimensional network structure of the Upper Ordovician Pagoda Formation in the country. It also outlines the basis of the analysis on the formation which involves the use of geochemical, paleontological and sedimentological information.