Environmental Distribution of Scleractinian Corals in the Jurassic of Kachchh, Western India

Scleractinian corals commonly occur at specific horizons and localities, in carbonate and in siliciclastic sediments, throughout the Jurassic (Bajocian to Oxfordian) of Kachchh as meatlows, biostromes, boulder beds and as scattered specimens. In rnany cases they are part of the autochthonous benthic fauna and in others they suffered short intra-basinal transport. Cerioid forms of low diversity (Amphiastraea Isastraea, etc.) abound in high-energy siliciclastic sediments. High diversity coral faunas, which include thamnasterioid (Microsolena, Dimorpharaea and Kobya) and solitary (Trocharaea and Trochoplegma) taxa with fenestrate septa and plocoid forms (Stylina), dominate in carbonate sediments deposited in low energy, deeper-water environments. The solitary Montlivaltia exhibits a great physiological tolerance of environmental stress. In all, eight coral assemblages have been recognized within the Early Bajocian to Late Callovian sediments of the Kachchh basin.

The distribution of scleractinian coral assemblages has been governed mainly by the rate of sedimentation and particularly by the influx of coarse siliciclastic material. As a consequence the distribution pattern reflects onshore offshore gradients and the general deepening of the Kachchh basin towards the Oxfordian.