川西地区中二叠统一下三叠统碳酸盐岩碳氧同位素特征

Carbon and oxygen isotope composition of carbonatic rock from the Middle Permian-Lower Triassic in Chuanxi area

针对川西地区中二叠统一下三叠统碳酸盐岩,通过分析3个剖面的碳氧同位素数据,计算Z值及古温度,并结合沉积相、古生物等,对该区域碳酸盐岩碳氧同位素演化特征及古环境进行了系统研究。结果表明,川西地区中二叠统一下三叠统碳酸盐岩的δ^(13)C值为-3.90‰~2.80‰,主要值域为-2.80‰~2.80‰,均值为-0.04‰;δ^(18)O值为-9.70‰^-1.80‰,主要值域为-8‰^-4‰,均值为-6.60‰。研究区古环境基本处于海相环境,东北边缘水体相对较深,西南边缘水体相对较浅,海水温度为8.8~68.4℃,主要值域为16~33℃,属于温暖或炎热的亚热带气候,经历了栖霞期—茅口期、吴家坪期—长兴期、飞仙关期—嘉陵江期3次大的海平面变化旋回,且其间各有若干次次级旋回。

For the Middle Permian-Lower Triassic marine carbonate rocks in Chuanxi area, the author analyzed the carbon and oxygen isotope three cross-sectional data and calculated the Z value and the ancient temperature in combination with sedimentary facies and paleo organisms to systematically study the carbon and oxygen isotopic characteristics of carbonate rocks in the region and the paleo environment. The results show that the value of 61℃varies from 3.90‰to 2.80‰ in the study area, mainly concentrated between-2.80 and 2.80‰, and-0.04‰ on average; The value of 6l50 varies from-9.70‰ to- 1.80‰, mainly concentrated between -8‰ and -4‰, and -6.60‰ on average. Through calculation and analysis of the Z value and the paleo temperature it can be seen that Middle Permian-Lower Triassic in Chuanxi area was basically in the marine environment with seawater temperature between 8.8 and 68.4℃ and the main distribution range 16 to 33℃. The study area basically belonged to the warm or hot tropical climate and experienced three major cycles of sea level changes： Qixia period to the Maokou period, Wujiaping middle period to Changxin period, and Feixianguan period to Jialingjiang period.