ABSTRACT 



Topographicaily the northern Arabian Sea can be divided into 

 two basins separated by the northeast- southwest trending 

 Murray Submarine Ridge. The northwest Gulf of Oman Basin 

 exhibits a more irregular topography, particularly along the con- 

 tinental margin, than does the southeast Arabian Sea Basin, 

 which is dominated by the large sediment cone of the Indus 

 River. Sediments with median grain sizes in the sand and silt 

 range are largely restricted to the continental shelves and up- 

 per continental slopes. Basin sediments are calcareous (17 to 

 51 percent calcium carbonate) and become more so to the 

 south. A band of relatively pure carbonate materials is present 

 on the outer Indian shelf. Detrital grains of dolomite and cal- 

 cite are present in small amounts in most samples, and frosted, 

 pitted quartz grains are common in the coarse fraction of sedi- 

 ments from the northwest basin. The non-carbonate coarse 

 fraction of the sediments contains much feldspar and an un- 

 stable heavy mineral suite of both metamorphic and igneous 

 origin. Dust is an important source of sediments over the entire 

 area. The dust contribution is relatively more important, and 

 the overall rate of sedimentation is lowest in the Gulf of Oman 

 Basm '-• — '^- — *— ^= — '"n Basin. 



