Abstract:
Highresolution shallow seismic surveys using boomer were carried out off the Minjiang Estuary. Depositional sequences since the end of MIS 6 were revealed with the maximum thickness of about 90 m. The reflection configurations of seismic sequences of MIS 5 and MIS 3 were studied and types of depositional morphology were identified based on seismic facies analysis. Combined with sea-level curves (SLC) of Marine Oxygen Isotope, sedimentary environments, special morphology and stages of system tracts were described. Finally, apparent intensity (apparent height) of transgressions and its affective factors were discussed. During MIS 5, the area studied was mainly an offshore-shallow sea environment where a subaqueous delta of Saijiang River (Jiaoxi Stream), tidal sand ridges and offshore bars were locally developed in MIS 5.3 and MIS 5.1. It was the land environments at its beginning and low sea-level stages, resulting in channels of Minjiang River and Saijiang River. During M3, the area was generally submerged under sea and dominated by offshore-shallow sea environments, a subaqueous delta lobe of Minjiang River and tidal sand ridges were locally developed. According to SLC, sea-level during MIS 5 was much higher than that of MIS 3, but typical seismic profiles show that the transgressive apparent intensity (apparent height) of the former was lower than the latter. It is inferred that this phenomenon was mainly related to tectonic subsidence and sediment compression to a certain extent as well, which may also explain why Minjiang River channels during MIS 5.2 in the southern area appeared much lower than the sea level at that time.