Morphology of submarine channel-levee systems in the eastern Bay of Bengal near Andaman region

Abstract

Multibeam echo-sounder (MBES), sub-bottom profiler, singlebeam tracks and public-domain bathymetry geophysical datasets were analyzed in a Geographic Information System (GIS) for accuracy assessment and further used to update the previous map (Curray et al. Mar Pet Geol 19: 1191–1223, 2003) of submarine channel-levee systems in the eastern Bengal Fan near the Andaman region. Comparative analysis of singlebeam with MBES indicated 2.8 % of root-mean-square difference in bathymetry, and could clearly bring out distinct submarine channel profiles. The channel map revealed that the previously named E6 [updated as E7(1a)] and E7 [updated as E7(1b)] channels emanate from the middle and lower Bengal Fan, respectively and merge together at 91.28°E, 10.64°N where they form a second order channel [E7(2)] that flows southward along the east of Ninety-east Ridge. Similarly, two first order channels [E6(1a) and E6(1b)] emanate from the lower Bengal Fan which merge together at 88.78°E, 06.92°N to form a second order channel [E6(2)] that flows along the west of Ninety-east Ridge towards the equator. This channel was previously thought to be linked to the middle Bengal Fan. High-resolution MBES tracks over the channel shows extensive meandering patterns with the channel gently deepening and widening towards south. Variations in the morphology and stratigraphy indicate that the E7 channel is characterized by a curvilinear course, with higher observed sinuosity wherever gradient decreases.