新疆塔里木盆地西北缘晚奥陶世疑源类

LATE ORDOVICIAN ACRITARCHS FROM THE NORTHWEST EAN MARGIN OF THE TARIM BASIN,XINJIANG,CHINA

新疆塔里木盆地西北缘阿克苏和柯坪地区达瑞威尔期末期至凯迪期中期地层发育良好,大湾西沟剖面、四十场剖面和铁热克阿瓦提剖面地层保存良好的疑源类组合。该组合包括20属36种疑源类,以棘刺类、光球类和梭形类占优势。塔里木盆地西北缘疑源类组合与国内、外同期组合对比表明晚奥陶世疑源类古地理分区性减弱,部分疑源类分子分布仅限于晚奥陶世,且古地理分布广泛,具有生物地层学对比的潜力。新疆塔里木盆地西北缘数条剖面疑源类组成和多样性变化的不同可能与小环境的差异有关。本研究中疑源类属种组成及多样性变化趋势和柯坪地区海平面变化一致,反映了萨尔干组到其浪组下部有一次海侵过程。

Upper Darriwilian to middle Katian(Ordovician)outcrops are well exposed in the Aksu and Kalpin area,northwest margin of the Tarim Basin,Xinjiang,China.The Dawanxigou,Sishichang and Tierekeawati sections,near the Dawangou section in the Kalpin area,yield well-preserved acritarchs.This acritarch assemblage is dominated by acanthomorph,Leiosphaeridia and netromorph with 36 species assigned to 20 genera.Comparison of the acritarch assemblage with the coeval assemblages elsewhere suggests a breakdown of the acritarch provincialism during the Late Ordovician.Several acriatchs from northwestern margin of the Tarim Basin are restricted to the Late Ordovician,and worldwide spread,which gives them have the potential for global biostratigraphical corrlelation.The acritarch assemblages from the northwestern Tarim Basin show a slightly different composition,possibly due to the slightly different facies.The diversity and compositional changes of the acritarch assemblages,combined with the sedimentological evidence,suggests a transgressive sequence from the Sargan Formation to the Qilang Formation.