Pteropod Occurrence in the Quaternary Sediments off Narcondam Island in Andaman Sea and Its Preservation Behavior With Depth

Pteropod commonly occurs in the Andaman Sea but their presence is restricted within the certain bathymetric level of the sea floor due to their fragile nature in the seabed sediments. Quantitative pteropod study from the seabed samples shows a characteristic relation to the nature of sediments and physiographic set up of the North Andaman basin. Systematic taxonomic study of about 2700 specimens of pteropod specimens from 54 seabed samples indicates the presence of 23 pteropod species in the study area which belongs to nine genera, three families and two suborders. The degree of preservation of the dissolution prone pteropod tests and their numerical abundance at various water depths in the seabed samples are utilized to determine the Aragonite Compensation Depth (ACD) in this region. It lies at about 1150 m isobaths. Results are displayed by ACD map and pteropod dissolution profile which are plotted against the water column to illustrate the relationship of pteropod preservation behavior with depth in the craggy volcanic arc domains of the Andaman basin.