Trace fossils in the Mesozoic sediments of Kachchh Western India

The Mesozoic succession of Kachchh, western India, is a classic example of the value of trace fossils in the interpretation of depositional sequences. Because this sequence has traditionally been referred to as Gondwana and because the previous emphasis has been on body fossils, a misconception has been established concerning this fascinating nearshore sequence. Preliminary investigations of generally well-preserved physical and biogenic structures in the Mesozoic rocks of Kachchh reveal that the entire succession represents deposition in a shallow marine coastal setting, i.e., lagoons, embayments, tidal flats, estuarine channels, shoals and shallow shelf. The Patcham Formation shows poor preservation of trace fossils due to lack of appropriate lithologies. The Chari Formation contains a rich ichnofauna. Of special interest are horizons of "bioconglomerates" showing reworked fillings of Thalassinoides burrows and pholad borings. The Katrol Formation exhibits a diversified and well-preserved assemblage of burrows, including an unusual feeding burrow here recorded for the first time. The Umia Formation though devoid of body fossils contains a rich and varied assemblage of ichnofossils. The uppermost part of this unit, the Bhuj Member, contains several thick horizons of densely Rhizocorallium-bioturbated sand, which supports a marine setting contrary to the general belief of its fluvial origin