The morphology, geometry and depositional characterization of the Neogene-Quaternary shelf canyons in the Rakhine Basin, Northeast Bay of Bengal

Abstract

Submarine canyons are the most important conduits for funneling sediments from shelf to slope and basin floor. Shelf canyons can receive the shelf coarse-grained sediments and supply to the slope canyons and downslope continuation channel complexes. High resolution 2D & 3D seismic data covering the shelf area of the Rakhine Basin is used to analyze the scale, morphology and intra-seismic characteristics of the Neogene-Quaternary shelf canyon. Six shelf canyons with different scales which migrated westwards were developed in the Neogene-Quaternary in the study area. The maximum width and incised depth of the shelf canyons are up to 10km and 900m, respectively. The shelf canyon shows a large scale “U” or “V” erosional shape with variable internal seismic geometries. Seismic facies within shelf canyons can be classified into three types: SF1-low amplitude-transparent chaotic reflections, SF2-discontinuous, high amplitude seismic reflectors characterized by either vertically or laterally offset-stacked V- or U-shaped elements and SF3-medium – low amplitude hemi-continuous reflections. The planform and a series of proximal-distal transects through one of the main Pleistocene shelf canyons shows a number of features, including a series of tributary gullies in the head area, canyon margins affected by faulting strongly and predominantly fine-grained, with a combination of inside levees or canyon quiescent drape facies or collapse enveloping the various stacked channel elements. The petrology analysis from the well penetrating the margin of the Pleistocene canyon shows medium-good sorted, subangular – subrounded, fine grained-silt sandstones. The rock type is mainly lithic arkose. The petrology features of the filling sandstones in the canyon has similarities with the background delta front sandstones. The internal fillings in the shelf canyons can be divided into four stages: Stage Ⅰ-erosion and bypass; Stage Ⅱ-mixed erosion and deposition with lateral migration channels; Stage Ⅲ-dominantly vertical stacked channels generated by the canyon blocked by the particularly common slumps from the canyon margins; Stage Ⅳ-mudstone passive fillings.

AAPG Datapages/Search and Discovery Article #90336 ©2018 AAPG Asia Pacific Region, The 4th AAPG/EAGE/MGS Myanmar Oil and Gas Conference, Myanmar: A Global Oil and Gas Hotspot: Unleashing the Petroleum Systems Potential, Yangon, Myanmar, November 13-15, 2018