塔里木板块上元古界阿勒通沟组和黄羊沟组:新识别的冰期和间冰期?

The Neoproterozoic Altungol and Huangyanggou formations in Tarim plate:Recognized newly glaciation and interglaciation?

通过库鲁克塔格地区孜厄肯—厄格孜达坂一带实测地层剖面研究重新建立了阿勒通沟组和黄羊沟组的地层层序。阿勒通沟组含三层冰成杂砾岩,为冰川沉积与滨-浅海沉积交替发育,代表海相环境下的冰川沉积。黄羊沟组底部白云岩具负的δ^(13)C 同位素值,下部以火山岩、上部以细碎屑岩和碳酸盐岩为主,沉积环境具有向上变深的特征,代表了阿勒通沟冰期结束后温暖环境下的海平面上升。结合冰成杂砾岩的特征、"盖帽碳酸盐岩"的分布、碳同位素和化学蚀变指数方面的证据,可将两者分别确定为独立的冰期和间冰期,并分别沿用阿勒通沟冰期和黄羊沟间冰期的称呼。阿勒通沟冰期的划分使得库鲁克塔格地区晚元古代冰期达到四次。根据库鲁克塔格地区已有的同位素年龄,阿勒通沟冰期可能与 Sturtian 冰期对比,贝义西冰期可能与 Kaigas 冰期而不是与 Sturtian 冰期对比。

Sequences of the Altungol and Huangyanggou formations are reset according to research of the stratigraphic sections in Zieken-Eghzidaban area, Quruqtagh, Tarim Plate. The Ahungol Formation contains three layers of diamictite. The sequence of glacial and littoral-neritic deposits of the Altungol Formation suggests an oceanic glacial sedimentation. Dolostone at the base of Huangyanggou Formation shows negative δ^13 C values. Lower and upper parts of the Huangyanggou Formation mainly consist of volcanic rocks and fine clastic rocks, respectively, suggesting npwarding deeper sedimentary environment, representing sea level rise in warm environment after Ahungol glaciation. Considering the characteristics of diamictites, distribution of the cap carbonate, evidence from the C isotopic composition and the chemical index of alteration, the Altungol and Huangyanggou formations could be identified as independent glaciation and interglaciation, called Altungol glaciation and Huangyanggou interglaciation, respectively. Recognition of the Ahungol glaciation adds a new ice age to the Newproterozoic in Quruqtagh, which means there were four ice ages during the Neoproterozoic in Quruketagh area. Age data analyses related with glaciation indicate that the Ahungol glaciation could be correlated with the Sturtian glaciation and the Beiyixi glaciation, with the Kaigas glacitaion.