GUTTER CASTS FROM THE PROTEROZOIC BIJAYGARH SHALE FORMATION, INDIA - THEIR IMPLICATION FOR STORM-INDUCED CIRCULATION IN SHELF SETTINGS

The orientations of elongate gutter casts occurring in inner shelf sto rm deposits of the Proterozoic Bijaygarh Shale Formation, India reveal a modal population oriented roughly parallel to the average trend of the associated wave ripples. Assuming that the wave ripple trend appro ximately represents the orientation of the contemporary shoreline, the shore-parallel gutters appear to have been formed by the geostrophic current. Some gutters oriented at high angles to the inferred shorelin e presumably represent incision by wave orbital currents in a storm-in duced combined flow regime. The gutters also show variations in the st yle of incision and infill, which may be useful in distinguishing betw een gutters formed by wave orbital and geostrophic currents, independe ntly of their orientation pattern with respect to the palaeo-shoreline .