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对塔里木板块中央隆起区3口钻井及巴楚露头区南一沟剖面采集的139个碳同位素样品进行分析对比,查明中上奥陶统碳同位素组成及演化特征。鹰山组δ13 CPDB值均<0,分布范围在-2.50‰~-0.5‰之间,平均值约-1.5‰;一间房组δ13 CPDB值均接近0‰,分布范围在-0.40‰~0.6‰之间,平均值约为0;恰尔巴克组—良里塔格组δ13 CPDB值均>0,分布范围在0.40‰~2.9‰之间,一般在1‰上下,平均值不低于1.2‰。三者δ13 CPDB值差异明显,可作为该区地层划分对比依据。中央隆起区中上奥陶世发生过2次大的δ13 C正漂移,第一次正漂移发生于中奥陶世大坪期(O12)末到达瑞威尔期(O22)初期,δ13 CPDB变化幅度在1‰以上;第二次正漂移发生于中奥陶世达瑞威尔期(O22)末到晚奥陶世桑比期(O13)初期,δ13 CPDB变化幅度接近2‰。2次正漂移导致鹰山组、一间房组、恰尔巴克组以及良里塔格组碳同位素值出现明显差异,这一变化特征与达坂塔格一间房露头区相应层位一致,与贵州桐梓红花园剖面也很相似,与柯坪露头区大致相似。
A total of 139 carbon isotope samples collected from 3 wells in the central uplift area of Tarim block and from the Nanyugou section of Bachu outcrop area were analyzed and compared to determine the carbon isotopic compositions and evolution characteristics of the Middle-Upper Ordovician. The δ13 CPDB values of Yingshan Formation were all <0 and the distribution range was between -2.50 ‰ and -0.5 ‰, and the average value was about -1.5 ‰. The δ13 CPDB values of one-house group were all close to 0 ‰ and the distribution range was -0.40 ‰ ~ 0.6 ‰, and the average value is about 0. The δ13 CPDB values of the Qia’er Bake Formation-Lianglitage Formation are both> 0, ranging from 0.40 ‰ to 2.9 ‰, generally 1 ‰, with an average of not less than 1.2 ‰. The difference between the three δ13 CPDB values is obvious, which can be used as the basis for stratigraphic division in this area. There are two large δ13C positive excursions in the middle uplift in the central uplift area. The first positive excursion occurred at the end of the Middle Ordovician period from O12 to the beginning of the Revel stage (O22). The δ13 CPDB variation At 1 ‰ or above. The second positive shift took place at the beginning of the Orthodontic Darwinian period (O22) to the late Ordovician Sambi period (O13), and the δ13 CPDB changed by nearly 2 ‰. The results show that there is a significant difference in carbon isotope values between Yingshan Formation, Yifefang Formation, Qiaerbuck Formation and Lianglitage Formation, which is consistent with the corresponding horizon of an outcrop of Dabantag, And Guizhou Tongzi red garden section is also very similar, and king outcrop area roughly similar.