摘要
根据“实验2”号调查船1987年4月在南海南部进行的多道反射地震测量结果,结合前人发表的资料,对分布于曾母盆地中的三套构造层的地震相变化、沉积、构造特征及时代属性作了分析研究。文中还探讨了古新世以来该区的构造运动与古地理环境演变。
The Zengmu Basin is located in the southern region of the South China Sea. Three tectonic sequences can be divided by Tg and Th regional unconformities which generally exist within the basin indicated by the multiple-channel seismic profilers. The occurence of the upper tectonic Sequence appears to be level and smooth belonging to the period from Oligocene to Recent. The thickness of the upper tectonic sequence ranges 3-6km with a maximum of more than 9km, which is a matine sedimentary sequence with the feature of infilled model in the bottom Section and predominately sheet-like superposition in the mediate and upper section. The delta-littoral, neritic facies marine clastic rocks and terrace-biological reef and carbonatite have been developed within the southern tract of the basin. The abyssal turbidity current and suspended argillaceous, deposits seem to be predominately identified within the mediate and northern tract of the basin. The smoothly wave-like folding structure is developed within the mediate tectonic sequence in the feature of obviously tilted fault-block belonging to the period of Paleocene-Eocene, of which the sub-parallel and divergent reflection could be found to be predominant, and thickness is more than 4.5km thinning to north and absent in some local areas. Which is estimated to be composed of unmetamor-phic neritic clastic deposits. The lower tectonic sequence is obviously folded and deformated, and interpreted to be Pre-Tertiary metamorphic sedimentary or igneous rocks.The basic variation of the paleogeographic framework occurred in Oligocene, which estimated that Nansha old land existed in north and further northern area of the basin before Oligocene. The main body of the Zengmu Basin were uplifted in L.Eocene and then has been subsiding Since Oligocene and the Nansha old land might be block-fractured and subsided into the abyssal sea.
出处
《热带海洋》
CSCD
1990年第2期23-30,共8页
