南沙中部海域沉积地层特征及其构造成因

Characteristics of Sedimentary Strata in Central Nansha Sea Area and Its Tectonic Origin

为了深入了解南沙中部海域的沉积特征及构造演化过程,选取了该区具代表性的02N02测线对其进行详细的构造和地层解释.发现研究区南部存在一整套厚度较大的中生代甚至更老的地层,该地层普遍发生了强烈的褶皱作用,褶皱翼部存在一系列NE-NEE向断裂,控制沉积明显,背斜顶部多被剥蚀,翼部为充填沉积.新生代地层Tg(中始新世)到T40(中中新世)界面之间,为裂谷充填和披覆沉积,层内控制沉积的断裂普遍发育,而T40界面之上为平整的盖层沉积,断裂作用极少,地层厚度变化不大.结合以上特征对比区内与02N02测线相交的87N4测线、临近的90N9等测线,以及横穿该区的94N2测线,分析了南沙中部海域中、新生代地层的构造成因,并进一步探讨了其中、新生代地层的演化过程.

To further understand the characteristics and tectonic evolution of sedimentary in the central waters of the Nansha,we select typical survey line 02N02 in this area and present detailed interpretation of its structure and stratigraphy.It finds that there is a set of thick Mesozoic or even older strata in the area,especially in the southern area,which generally has strong folding,and there is a series of NE-NEE-trending faults controlling the deposition obviously in the wings of folds.Anticline has been eroded at the top,deposited in the wings.The filling and coating deposition between Cenozoic Tg（the top of Middle Eocene） and T40（the bottom of Middle Miocene） interface in rift valleys were controlled by faults,and the formation of cap rock above T40 with little change in stratigraphic thickness were less controlled by faults.Combining these features above and comparing the line 87N4 intersecting with line 02N02 and the line 90N9 nearby the line 02N02 to the east,and the line 94N2 crossing this area,we analyze the Mesozoic and Cenozoic tectonic origin of the central Nansha Sea area,and further discuss its evolution.