In the LDS, the DOM comprises bioclastic wacke-pack-floatstones, bioclastic oolitic wacke-pack-floatstones, calcareous siltstones, bioclastic-oolitic siltstones, and stromatolitic oolitic siltstones, almost distributed evenly. However, the organic matter rich micritic matrix forms about 25% of the rock. Only a dark-colored insoluble residue could be observed as matrix in most of the samples owing to the compaction and dissolution. The micritic and argillaceous matrix is present only in intergranular porosity. The rocks of the Dhosa Sandstone Member are marly/argillaceous coarse silt-fine sandstones and contain varying abundance of bioclasts. The matrix is micritic, organic rich, and shows calcite sparitization. Very few micritized echinoderm fragments are also observed. The peloids are subangular to subrounded and are poorly to moderately sorted. They show mouldic nature and are filled with fine to medium sized spar.

Other bioclasts are lath shaped and angular. The bioclasts, particularly finer ones, show completely micritized character. The monocrystalline quartz silt is randomly oriented, lenticular and equant in shape, angular, sorted, and confined within fine to very fine silt size classes. The bioclastic arenaceous packstones are composed of 50% grains and 50% argillaceous and micritic matrix. In the LDS, this member is represented by very finely laminated, marly/argillaceous very fine silt. Bedding parallel dark insoluble residue/organic matter, lenticular quartz grains, and angular bioclasts are observed frequently. The rock shows discontinuous, but bedding parallel quartz rich (<40%) and mud-rich layers. These interlayers are found without any break in sedimentation and resulted by increased influx of bioclasts of bivalves and echinoderms. The Gypsiferous Shale Member is composed of bioclastic calcareous very fine silt interspersed with bioclastic arenaceous packstone and occasional arenaceous peloidal bioclastic packstone. (A) Lodai section (B) Fakirwari section (C) Jumara section (D) Jara dome Tr. Lithologs of the three studied sections and position of geochemical samples. The Jumara section (JMS) is located at about 20В km northeast of Matanomadh close to the Jumara village and exposes the DOM and basal part of the Katrol Formation ( Fig. The Fakirwari section (FWS) is located at about 6В km south of Bhuj, along the road to Mundra, exposing the DOM and other members of the Chari Formation ( Fig. The rocks are exposed close to the road 3В km south of Lodai, over a lateral distance of 320В m, showing the occurrences of the Gypsiferous Shale, Dhosa Sandstone, and DOMs of the Chari Formation and basal part of the Katrol Formation ( Fig. The Lodai section (LDS) is a composite section located at northeast of Bhuj in the Habo dome ( Fig. Among various exposures examined, three sections located in Lodai, Fakirwara, and Jumara that contain condensed sections of the DOM are discussed in this paper. This surface is a chronological boundary between Callovian-Oxfordian ( FГјrsich etВ al., 2001) and also a transgressive systems tract surface ( Pandey etВ al., 2009). The DOM rests over the Dhosa Sandstone Member with a distinct erosional/nondepositional surface. Good exposures are found in Jara, Jumara, Keera, Jhura, and Habo domes/areas, located between southeast of Lakhpat and east of Bhuj ( Fig. It is easily recognizable in the field by its red-colored, well-cemented cap rock and massive amorphous iron crusts at top. The DOM is exposed for about 100В km along its strike direction in the Kachchh mainland.

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