Lime mud in continental shelf edge and slope off Kachchh

Abstract

Occurrence of lime mud (about 3200 km2 in extent and > 2.3 m thick) is being reported in the continental shelf edge and upper slope domains off Kachchh. Lime mud is amorphous, homogeneous, creamy white and consists of skeletal matter, white ooids and mud aggregates. It is overlain by a 40 cm thick grey clay carpet. The lime mud bearing cores exhibit gradual grain size reduction from bottom to top. The lime mud has 94% CaCO3 in the shelf edge to 71% in lower slope. The chief constituents of the clay fraction of the lime mud are aragonite and calcite as revealed by the X RD analysis. The relict carbonate shoal at 100 m isobath in the outer continental shelf is probably the source for the lime mud. Mechanical disintegration of skeletal matter, slope failure due to glacio-eustatic changes and physiographic barriers in the upper continental slope are responsible for the production and localisation of lime mud.