塔里木盆地草湖凹陷侏罗系划分与对比

摘要

The Jurassic of Caohu depression in the Tarim basin developed fully, with large thickness,but the precision of stratigraphic division and correlation is lower,which is one of the important reason that restrict the exploration of oil and gas in this aera.According to the fossil material collected from drilling hole,established three palynological assemblages,there are Cyathidites-Osmundacidites-Piceites,Cyathidites-Neoraistrickia-Disacciatrileti and Cyathidites-Classopollis- Piceaepollenites,Aneuletes cucuma and A.stellerides-A.lufengensis.A.maxima-P.kucheensis.The Jurassic was divided into three series,five formations,From bottom to top are Ahe Formation and Yangxia Formation in lower series Kizilnur Formation and Qiakmak Formation in middle series and Qigu Formation in upper series(Kelazha Formation is lacuna).Lithological and logging characterastics are obvious in each member.the "coal stratification"at the lower and "black mudstone sagment" at the top of the Yangxia Formation,the "coal stratification" in the kizilnur Formation and the "red mudstone sagment" were regarded as the key bed in this research area.There is sedimentic absence in the Ahe Formation and the lower parts in the Yangxia Formation,denuded absence from Qiakmak Formation to Kelazha Formation in most aera.Jurassic was divided into three second-order and five third-order sequences,relied on the seismic sequence stratigraphy and borehole sequence stratigraphy,the detailded classification and correlation of Jurassic in the aera has been achieved,which based on biostratum and combined litology,sequence and logging strata.Those discoveries made it possible to analyze the tectonic evolution,sedimentary facies and hydrocarbon accumulation in Caohu sag and neighbouring regions.%塔里木盆地草湖凹陷侏罗系发育较全,沉积厚度大,但地层划分对比精度低,是制约该区油气勘探重要因素之一.本文据多口钻井样品获得丰富化石资料建立了3个孢粉组合,即Cyathidites-Osmundacidites-Piceites,Cyathidites-Neoraistrickia-Disacciatrileti与Cyathidites- Classopollis-Piceaepollenites组合;1个大孢子组合,即Aneuletes cucuma高含量组合；两个轮藻组合,即A.stellerides-A.lufengensis与A.maxima-P.kucheensis组合.将草湖凹陷侏罗系划分为3统6组,自下而上为下侏罗统阿合组、阳霞组,中侏罗统克孜勒努尔组、恰克马克组,上侏罗统齐古组(缺失喀拉扎组),各段岩电特征极明显.阳霞组下段煤层、上段黑色泥岩段,克孜勒努尔组煤层及齐古组红色泥岩段可作为区域地层对比标志层,指出大部分地区阿合组与阳霞组下部为沉积缺失,恰克马克组至喀拉扎组为剥蚀缺失.层序地层共划分为个3个Ⅱ级、5个Ⅲ级层序,以生物地层为依据,结合岩石地层、层序地层与测井地层,对该区侏罗系进行详细地层划分与对比,为沉积相、构造演化及油气成藏等深入研究奠定了地层学基础.