东昆仑—阿尼玛卿地区早二叠世的沉积古地理

Depositional Palaeogeography in East Kunlun and Animaqing during Early Permian

东昆仑—阿尼玛卿地区早二叠世古海洋自北而南可分为东昆仑半局限海、托索湖—花石峡礁岛链和阿尼玛卿洋三部分。托索湖—花石峡礁带的主体由块状的礁相灰岩和生物碎屑灰岩所组成 ;东昆仑南坡半局限海中以短轴型的礁岛或碳酸盐建隆及相对较深的岛间盆地相沉积为特征 ;阿尼玛卿洋中则主要以深海软泥及放射虫硅质岩沉积为主 ,同时也点缀一些碳酸盐建隆高地。东昆仑南坡半局限海中的礁岛及碳酸盐建隆在分布上缺乏明显的规律性 ,但该区生物礁较发育。阿尼玛卿洋中碳酸盐建隆的规模小、分布零星、生物礁相对不发育 ,但这些碳酸盐建隆在面上多呈断续的串珠状分布 ,具有较明显的规律性。东昆仑南坡半局限海中的岛间盆地相主体以中薄层灰岩夹黑色板岩沉积为特征 ,同时也有一些深水软泥沉积 。

During Early Permian, the palaeo ocean in East Kunlun and Animaqing area was composed of three depositional regions. They are the back arc basin in the southern slope of East Kunlun, reef island belt from Tuosuo Lake to Huashixia and deep ocean in Animaqing. The reef island belt from Tusuo Lake to Huashixia is mainly composed of massive reef limestone and bioclastic limestone. The back arc basin in the southern slope of East Kunlun was widely scattered by short dimension reef islands or carbonate buildups and relatively deep basins among the reef islands. However, the Animaqing ocean was dominated by deep ocean ooze and radiolarian chert. Carbonate palaeo-seamounts can also be found in Animaqing ocean. Although there are many well developed reefs in the southern slope of East Kunlun, the reef islands and carbonate buildups were distributed irregularly in this area. Carbonate palaeo seamounts in Animaqing ocean are relatively smaller and reef limestone is less developed, but the palaeo seamounts usually range like a string of beads. Basin sediments between the reef islands in the southern slope of East Kunlun are mainly composed of middle thin layer of limestone embedded with black slate, and basin ooze with different color can also be found in some places. Basin sediments in Animaqing ocean is characterized by widely distributed deep ocean ooze. However, blue green ooze can be found more easily in the southern slope of East Kunlun than in Animaqing.