塔北隆起早奥陶世碳酸盐岩沉积相与海平面变化

CARBONATE SEDIMENTARY FACIES AND SEA-LEVEL CHANGE IN EARLY ORDOVICIAN IN TABEI UPLIFT.

塔北隆起区下奥陶统碳酸盐岩可明显地划分为西部的浅水碳酸盐台地相区和东部的深水碳酸盐斜坡—盆地相区。台地相区以潮坪相最发育。深水斜坡—盆地相区明显受早奥陶世塔里木地块东缘的被动大陆边缘的构造背景所控制。区内碳酸盐沉积相模式可与Ｔｕｃｋｅｒ模式相比较。下奥陶统沉积旋回发育，并可进行区域对比，反映了这种沉积旋回是与海平面的升降变化有关。在浅水台地相区，沉积旋回的顶部往往出现短期沉积间断，导致碳酸盐沉积物经历大气淡水淋滤与溶解作用，形成溶蚀孔隙。但是，这种孔隙还受到后期成岩作用的影响与改造。

Lower Ordovician carbonate in Tabei uplift can be distinctively divided into two types of facies belts: shallow-water carbonate plateform in the west and deep-water carbonate slope-basin in the east. The former is dominated by tidal flat facies, and the latter is obviously controlled by the tectonic setting of the passive continental margin at the eastem margin of Tarim massif. Carbonate sedimentary facies medel correlates well with Tucker model. Lower Ordovician depositional cycles are abundant and regionally correlated indicating its dependence on sea-level change. Frequent short-time exposure at the top of the depositional cycle resulted in the formation of vugular-pore in carbonate deposits subjected to leaching and dissolution of meteoric fresh water. However, such pores were influnced and reworked in late diagenetic stage .