塔里木盆地奥陶纪碳同位素波动特征与对比

Fluctuation characteristics and correlation of carbon isotope in Ordovician,Tarim Basin,China

在牙形石生物地层的基础上,利用塔里木盆地塔北隆起钻井全岩碳同位素数据,结合其他学者公布的碳同位素曲线,探讨了塔里木盆地奥陶纪碳同位素波动特征,并与世界其他地区进行对比。塔里木盆地奥陶纪特马豆克阶-达瑞威尔阶早期碳同位素波动较弱,缺乏可全球对比的波动标志。达瑞威尔阶中期和凯迪阶早期发育明显的碳同位素正漂移,分别对应于国际上的中达瑞威尔阶碳同位素正漂移(MDICE)和加顿伯格碳同位素正漂移(GICE),能够进行全球对比。桑比阶早期牙形石Pygodus anserinus带内发育波动幅度达1.4‰的正漂移,其可能仅在部分地区分布,暂时命名为早桑比阶碳同位素正漂移(ESICE)。凯迪阶中后期碳同位素波动特征目前还不清楚,晚奥陶世赫南特阶碳同位素正漂移(HICE)在塔里木盆地也未见报道。MDICE和GICE可作为塔里木盆地中上奥陶统的等时对比标志。

Based on conodont biostratigraphy,the whole-rock carbon isotope data from drilling core in Tabei uplift,combined with published carbon isotope curves,are used to investigate the carbon isotope fluctuation characteristics of Ordovician in Tarim Basin,and to correlate them with other regions of the world.It shows that Carbon isotope fluctuations from Tremadocian to early Darriwilian in Tarim Basin are weak,and can be correlated globally.However,carbon isotope positive excursions clearly develop in middle Darriwilian and early Kaitian,corresponding to middle Darriwilian carbon isotope excursion（MDICE）and Guttenberg carbon isotope excursion（GICE）respectively,also correlating globally.Carbon isotope positive excursions within conodont Pygodus anserinus zone develop in early Sandbian and the range of δ^（13）C are fluctuate up to 1.4‰.This positive excursion mayregionally distribute,and can be named early Sandbian carbon isotope excursion（ESICE）.The fluctuation characteristics of carbon isotope in middle-late Katian are unclear so far,and the Hirnantian carbon isotope excursion（HICE）of late Ordovician is also not reported in Tarim Basin.MDICE and GICE can be used as isochronous correlation markers of Middle-Upper Ordovician in Tarim Basin.