ENVIRONMENTAL DISTRIBUTION OF TRACE FOSSILS IN THE JURASSIC OF KACHCHH (WESTERN INDIA)

Trace fossils occur abundantly in Middle Jurassic rocks of the Kachchh Basin. They are found in environments ranging from beach sequences do wn to central parts of the basin. For stratinomic reasons, they are pa rticularly well preserved in storm deposits. Their distribution patter n exhibits a clear relationship to the hydrodynamic conditions and, se condarily, to bathymetry, and follows the classic ichnofacies concept of SEILACHER (1967). High energy nearshore areas and submarine shoals are represented by members of the Skolithos ichnofacies such as Ophiom orpha nodosa, Arenicolites, Diplocraterion parallelum, and Rhizocorall ium jenense. The storm-influenced ramp contains both members of the Cr uziana ichnofacies (e.g. Rhizocorallium irregulare, Thalassinoides sue vicus, Taenidium serpentinum, Chondrites) and the Skolithos ichnofacie s tin particular Ophiomorpha). The former were produced during interst orm phases, the latter are of post-storm origin. Carbonate ramp enviro nments of low to intermediate energy also contain members of the Cruzi ana ichnofacies, whilst equivalent siliciclastic environments are char acterized by a low-diversity Zoophycos ichnofacies. Low energy basinal environments of fine-grained substrates contain an impoverished Cruzi ana ichnofacies consisting of Chondrites, Trichichnus and Thalassinoid es suevicus. 32 ichnotaxa are briefly described, among them Sphaerichn us lobatus ichnogen. et ichnosp .nov.