南海新生代沉积建造的基本特征

BASIC CHARACTERS OF CENOZOIC SEDIMENTARY FORMATION IN THE SOUTH CHINA SEA

根据大地构造特征，我们把南海的新生代沉积建造划分为代表稳定陆壳区的稳定型、代表被动陆缘区的次稳定型和代表主动陆缘的不稳定型三大类，并由不整合面特征，把其沉积建造划分为下旋回（古新统—始新统）和上旋回（渐新统—第四系）。南海南部陆缘和北部陆缘均发育有上、下两个旋回，然而，南海中央海盆则仅发育了上旋回。通过对沉积建造特征的分析，认为南海的下旋回大多属充填式沉积，主要由河流一湖泊相沉积组成；上旋回属超覆沉积，主要由浅海相或深海相沉积组成。结合其大地构造环境，认为南海及其邻区的盆地类型共有五种，即克拉通型盆地（如北部湾盆地）、陆缘裂谷型盆地（如珠江口盆地、台西南盆地）、海底扩张型盆地（如中央海盆）、前陆型盆地（如曾母盆地）和岛弧型盆地（如吕宋中央河谷盆地），其中，中央海盆形成于中渐新世之后。由于菲律宾岛弧的推覆和仰冲，以及加里曼丹陆块的逆时针旋转，最终导致古南海的关闭和消亡。

The sedimentary formation of the South China Sea in Cenozoic can be classified into into stable,substable and unstable types by tectonic environments,and divided into low-er(E_1──E_2)and upper(E_3 Q)cycles by the unconformity of the late Middle Eocene. Both north and south continental margins have two sedimentation cycles,but Central O-cean Basin only has the upper one.By analyses of the sedimentary formation,we suggested that the lower cycle was mostly fill sediments,and mainly fluvial-lacustrine facies;the upper cycle was onlap sedi-ments,and was mainly turned to shallow marine or deep ocean facies,It indicates that Central Ocean Basin has been formed since Mid-Oligocene,And the nappe and obduction of Philippine island arc and the counterclockwise rotation of Kalimantan resulted in thegradual closing of the Paleo-South China Sea.