羌塘盆地那底岗日地区中侏罗世层序地层与碳、氧、锶同位素响应

Carbon,Oxygen and Strontium Isotopic Responses of Carbonate Rocks and the Middle Jurassic Squence Stratigraphy in the Nadigangri Area,Qiangtang Basin

羌塘盆地那底岗日地区中侏罗世沉积了一套稳定的滨浅海相碳酸盐岩与碎屑岩地层 ,通过层序地层研究划分出五个三级层序。对其中四个层序内碳酸盐岩碳、氧、锶稳定同位素测试分析得出 ,不同层序、层序界面及层序内不同体系域的δ13 C、δ18O、N(87Sr/86Sr)值均有明显的差异 ,并具规律性变化 ,整体上反映出研究区中侏罗世发生了多次海平面升降变化和气候、构造活动的演变 ,为层序地层研究提供了定量的地质地球化学依据。

A series of steady carbonate and clastic rocks of coastal-shallow sea facies were deposited in the Nadigangri area,Qiangtang Basin,during the middle Jurassic. The middle Jurassic can be divided into five 3rd-graded sequences through sequence interpretation . On the basis of C, O and Sr isotopic compositions of four of those, δ~ 13 C,δ~ 18 O and N (~ 87 Sr /~ 86 Sr) values are all of distinct difference and regularity among different sequences, sequence boundaries and systems stracts. It is suggested that the going up and down of sea level occurred many times and the climate and tectonics change during the middle Jurassic, which controlled the formation and evolution of the middle Jurassic sequences. As a result, C, O and Sr isotopes can provide some quantitative geological and geochemical evidence for analyzing the middle Jurassic sequence.