Ooids and peloids in the continental shelf off Kachchh, west coast of India - Inferences to palaeosealevel oscillations

Abstract

Grey ooids (0.05 to 0.125 mm size) around 60 m depth, white ooids (0.125 to 0.0625 mm size) around 110 m depth and pale brown peloids (0.125 to 0.0625 mm size) around 90 m depth occur in the continental shelf off Kachchh. In cross sections, grey ooids with five and white ooids with three concentric growth rings are observed. In grey ooids an internal black growth ring with Fe and S as revealed by EMP studies suggest pyritization after regression. White ooids do not show any elemental variation. Peloids contain organic matter. The following inferences are drawn (1) grey ooids are considered older. than the white ooids though they occur at shallow depth or (2) few reversals of sea level took place around 60 m level during Holocene, which caused formation and pyritization of ooids.