Provenances of possible turbidites and volcanoclastic sediments in the northern part of Narcondam-Barren Basin, Andaman Sea

Turbidity currents are marine avalanches consisting of dilute mixture of sediment and water. These deposits are known as turbidite deposits or turbidites. Seismo-turidites are indicative of submarine landslide caused due to ground shaking associated with great earthquake. Evidence for turbidite and volcanic deposits is observed on subsurface sediments from a gravity core collected at a water depth of 1689 m in the northern part of Narcondam-Barren Basin, Andaman Sea during the present study. To constrain the mode of sediment transport, global bathymetric model (GBM) data was used to generate digital bathymetric model (DBM). The bathymetric model shows two active channels: one in Martaban Canyon, along Sagaing Fault (drainage A), and the second one in the western part (drainage B). The moderately sinuous nature with channel-levee system of drainage B is also identified in high-resolution MBES grid model. Coarse fraction (+230 ASTM) studies of the core reveal the presence of multiple sand layers at different levels. SEM-EDAX and electron probe microanalysis (EPMA) studies confirmed subangular quartz-rich layers at 114–116 and 166–169 cm with transparent nature and subrounded amphibole-rich layer at 151–155 cm. The source of these anomalous sand layers observed in the core is from the outer shelf relict sand. These relict sand brought to the Narcondam-Barren Basin by drainage B, which formed by slumping/sliding material in the outer Ayeyarwady shelf induced by ground shaking/earthquake. Geochemical studies show a low Ca/Fe ratio and high Sr values in GC-01 where there is a high terrigenous percentage which implies a seismo-turbidite deposit. On the other hand, the geochemical studies clearly show that pumice at 25–40 cm is volcanic derivatives during Holocene. Since some of the mega-scale slumps are tsunamigenic, such studies are significant to locate submarine slump/slides.