Abstract
An X-ray diffraction study of forty-six sediment samples and three oolitic limestone samples from the western continental shelf of India shows that aragonite is the dominant carbonate mineral (99% maximum), followed by low-magnesium calcite (77% maximum), and high-magnesium calcite (39% maximum). MgCO sub(3) in the high-magnesium calcite ranges from 5 to 21% (maximum in the limestone) with the most prominent mode at 13%, followed by lesser modes at 16, 9 and 6.5%. These modes are attributed to the presence of various organic constituents in the sediments and rocks. The sediments and the limestones are similar in mineralogy. Thus it is concluded that no diagenetic change has taken place in the limestones after their formation.