南黄海Heuksan盆地的地震地层学研究

南黄海中的南HEUKSAN盆地是一个介于矩形到菱形之间、大小大致为32 km×13 km的盆地.这个盆地有两个最厚的沉积中心;一个在盆地西部中央,地震双程到时2.2 s的部位;另一个在盆地东部中央位置.二者之间以中央隆起相隔.盆地的地震剖面可以进一步划分为古生代到三叠纪时期的前地堑相沉积,新生代的地堑充填沉积及中新世到上新世时期的的内凹沉积.地堑充填时期的沉积可以分为两个地震层序A和B.层序A和B又可以进一步划分为3到4个亚层序.在南HEUKSAN盆地利用地震层序学的方法对上始新统地震剖面进行了较为详细的分析.认为古水流大部分是从盆地的西部流入的.因此推断其沉积物源主要来自西北部地区,其次来自于盆地的北部.顶积层为三角洲相.根据反射地震剖面的连续性、振幅和反射频率等在上始新统的地震剖面上划分出4个地震相带.地震相A区主要位于两大沉积中心部位.为三角洲前缘泥砂.相带B位于沉积区的西北边缘为平坦三角洲的沙砾.相带C2沿着南部的盆地边缘断裂带分布,为冲积扇.结论认为:始新统的地震解释剖面表明当时主要为三角洲沉积.主要沉积物来自西北的陆源区和南HEUKSAN盆地的西北部.在盆地的南部边缘,沿着盆地的边界断层发育有冲积扇的沉积环境.

Seismic stratigraphy of the Heuksan Basin in the South Yellow Sea

The south-Heuksan basin in the South Yellow Sea was delineated as rectangular to rhombic shape and a di mension of 32×13 km.The basin has two depocenters;0ne is at 2.2 sec in two-way travel time in the western central part and another at 1.7 sec in the eastern central part and they are separated by a central highIand.The sediimen tary section of the basin is subdivided into pre-graben phase deposited during the period from Paleozoic to Trassic time,graben-fill phase deposited in the early Cenozoic period,and interior sag phase of Miocene and Pliocene age.The sedimentary rocks of graben-fill phase is divided into two seismic sequences of A and B.It is inferred that the ma ior sediment source came from the northwestern area and the second source came from the nonhem part of the basin. Sediments have been transported in delta type based on the existence of topsets.F0ur seismic facies groups are distiin guished in seismic-reflection profiles of upper Eocence sedimentary sections based onthe analysis of continuity,ampli tude and frequency of reflectors.A seismic facies area is located on the two-depocenters and interpreted as delta fron tal margin sand and mud.The B seismic facies are located in the northwestern edge of the depression is inferred as delta plain sand and graveL The C2 seismic facies area is scatted along the basin-bounding fault in the south depres sion and is interpreted as an alluvial fan.In conclusion,Eocene sedimentary section was deposited as a deltaic deposi tion flowed from the northwestern to northern terrigenous area into the northwestern of the Soth-Heuksan basin.The alluvial fan deposition environment was developed along the basin-bounding fault in southern margin of the basin.