황해남동부 제4기 후기 퇴적층의 시퀀스 층서와 퇴적진화: 초기연구

Abstract

high-resolution seismic profiles and core sediment sampling have been conducted to investigate the sequence stratigraphy and depositional evolution of late Quaternary deposits in the southeastern YellowSea. Approximately (1060) line-㎞ data of chirp and sparker profiles was acquired. Along with seismic profiling, 15 piston core samples were collected. High-resolution seismic profiles show the Holocene mud deposit and the complex sedimentary structure. The late Quaternary deposits on the study area can be divided into three sequences (Unit A, B, and C, from oldest to youngest). The lowermost Unit A, overlying the acoustic basement, forms confused inner reflectors and incision-fills. The thickness of Unit A increases slightly toward southwest. Unit B is characterized by parallel reflections and ridge-and-swale topography. The uppermost Unit C displays acoustically transparent or sybparallel reflectors with homogeneous seismic facies, regionally including acoustic anomalies related to shallow gas.Core samples were analyzed for sediment texture (grain size, sand, silt and clay contents), physical properties (porosity, water content, bulk density, grain density and shear strength), and acoustic properties (compressional wave velocity and attenuation). The measured and calculated results are; mean grain size 2.14~8.43 phi (average: 5.29 phi), porosity 32.8~72.6% (average: 56.8%), water content 15.8 50.5% (Average 34.8%), wet bulk density 1.5~2.2 g/㎤ (average: 1.8 g/㎤), grain density 2.5~3.1 g/㎤ (average: 2.7 g/㎤), compressional wave speed 1362~1666 ㎧ (Average: 1514 ㎧). Unit A and Unit B comprise the sandy sediments with shell fragments, whereas Unit C is composed of homogeneous and soft mud, partially including the gassy sediments.