Post-glacial mud depocentre in the southern Beibu Gulf: acoustic features and sedimentary environment evolution

Abstract

Abstract This study documents the Southern Beibu Gulf Mud Depocentre (SBGMD) for the first time using high-resolution sub-bottom seismic reflection profiles. The SBGMD is located near the southern mouth of the Beibu Gulf in water depths of 50–80 m, and covers an area of more than 11 000 km 2 . The acoustic architecture of the SBGMD is characterized by a homogenous seismic unit surrounded by an erosive area where gullies and sand/mud waves occur. The SBGMD unconformably overlies a parallel-bedded seismic unit. Based on 14 C-dating, together with acoustic, lithological and geochemical analysis of gravity core SO31, which was sampled within the high-sedimentation-rate area of the SBGMD, the post-glacial sedimentary history may be summarized as follows: (1) from 12.8 to 11.6 cal ka BP, the SBGMD was deposited in a low-energy, brackish/freshwater and intensely terrestrial-influenced environment; (2) from 11.6 to 8.4 cal ka BP, the SBGMD underwent marine transgression; and (3) from 8.4 cal ka BP to present, a continuous shallow-marine environment has prevailed. Comparing the age and depth of the SBGMD base with the established sea-level curve, lacustrine sedimentation is predicted to have occurred in the SBGMD area before 12.8 cal ka BP.