高雄外海末次冰盛期以來之高解析地質構造研究

To understand the revolution of sedimentary system tracts during sea level rise, and to analyze seabed topography and shallow geological structure distributions off Kaohsiung since the Last Glacial Maximum (LGM). This study will apply high-resolution seafloor topography, seismic profile and sub-bottom profile to figure out above research issues. In the study area, previous study shown that the sea level has dropped to about -137.5 meters from the current sea level in the LGM. It is reasonable to collect sparker high-resolution seismic data in the offshore area above 200 meters depth should be able to fully describe the sedimentary systems since the end of the LGM.According to the newly collected seafloor topography data, some individuals in the semicircular depression structure located at 140 meters in the study area already show complete geomorphological features. On the sedimentary cross-sections on both sides of the semicircular depression structure, there are mainly overlying horizontal sedimentary sequences, and there is an obvious pseudo-integrated surface 20 to 30 meters below the seabed. This study speculates that this layer may be the position of the Maximum Flooding Surface (MFS) after LGM. In the eroded area of the depression structure, a wide range of erosion and fold structures appeared in the strata. Therefore, this study preliminarily speculates that these fold structural belts are actually ancient semicircular depression structures. They are located in the active area of the deformation front. Therefore, when the overlying horizontal sedimentary sequence is eroded and washed out, the fold structures which caused by plate movement are exposed to the seabed. In addition, in the west side of the Gaoping Canyon, the sub-bottom profile (SBP) data collected in this study were compared with the Spark seismic data by previously studied. The results show that the SBP can clearly observe the stratum boundary of the MFS in the area where the water depth is more than 40 meters. However, the SBP data shallower than 40 meters cannot confirm the interface distribution of the MFS due to the penetration depth, which may be related to the seabed sediments biased towards sandy and affect the penetration depth of the SBP profile.Therefore, this study will also collect numerous SBP data for comparison with sparker seismic data, and clarify the sedimentary system tracts to which the shallow sedimentary sequence belongs, and the geological structure distribution and genesis of the shallow strata. It is also expected that coring will be carried out on the outcrops of the continental shelf, shelf break and depressions, to analyze the changes in grain size from different sedimentary systems, and the correlation between sedimentary facies and sedimentary environment. Previous studies have pointed out that there is the possibility of groundwater discharge into the sea along the coast of Kaohsiung; the past studies in the Baltic Sea have also confirmed that the semicircular depressions are related to the submarine groundwater discharge (SGD). Therefore, this study will further explore the relationship between the semicircular depressions on the seabed and the SGD.