塔里木盆地中奥陶世一间房组沉积时期构造-沉积环境与原型盆地特征*

盆地原型研究有助于恢复盆地构造-岩相古地理和揭示盆山耦合,对油气勘探具有重要的指导意义。文中利用最新的钻井、地震及露头资料,以沉积相为研究实体,运用盆-山结合的思路,由点→线→面进行分析,重建了塔里木盆地中奥陶世一间房组沉积时期的构造-沉积环境,研究了原型盆地特征及性质。一间房组沉积时期,巴楚—塔中和塘南台内隆起为暴露剥蚀区;顺南—塘古巴斯—玉东台内洼地区发育低能的泥晶灰岩相;塔北和古城台地区发育大面积的台内颗粒滩相;柯坪台盆区发育深水瘤状灰岩—黑色页岩相;塔东深水盆地区经历了黑色页岩相→陆源碎屑浊积岩相的演变;库鲁克塔格—罗西台地区为继承发育的开阔台地相。该时期塔里木盆地构造-沉积格局具有由早奥陶世东西分异的台盆格局向晚奥陶世南北分异的隆坳格局过渡的特征,表现为塔西台地古地貌的分异和塔东深水盆地沉积性质的反转。该时期塔里木盆地整体具有克拉通内拗陷与边缘拗陷复合的性质,但在塔西克拉通内坳陷的南部叠加了前陆盆地的性质(塘南前隆和顺南—塘古巴斯—玉东后隆坳陷),在其西北部叠加了裂陷盆地的性质(柯坪克拉通边缘裂陷)。该时期塔里木盆地构造-沉积环境与原型盆地特征是其对周缘大地构造运动的响应。

Tectonic-depositional environment and proto-type basins during the depositional period of Middle Ordovician Yijianfang Formation in Tarim Basin

Proto-type basin analysis is of great use to uncover the tectonics-lithofacies palaeogeography and restore the basin-mountain coupling process and is of great significance for the guiding of petroleum exploration. Based on the newest data of drillings,seismic profiles and outcrops,with the analysis of sedimentary facies and the combination of basins and orogenic belts,this paper reconstructed tectonic-depositional environment during the depositional period of Middle Ordovician Yijianfang Formation in Tarim Basin and analyzed the features and properties of the basin,by employing the method of “point → line → planar”. During the depositional period of Yijianfang Formation,the Bachu-Tazhong and Tangnan intra-platform uplifts were the denuded zones;low-energy micrite facies were developed in the Shunnan-Tanggubasi-Yudong intra-platform sag;carbonate shoals facies were widely distributed in the Tabei and Gucheng platforms;deep-water nodular limestone and black shale facies were developed in the Kalpin intra-platform basin;the Tadong deep water basin transformed from black shale facies to terrigenous clastic turbidite facies and open platform facies were developed in Kuruktag-Luoxi area. The tectonic-depositional pattern of the Tarim Basin had the interim transition feature from the platform-basin pattern of the Early Ordovician to the uplift-depression pattern of the Late Ordovician,behaving as the palaeogeography differentiation of the Taxi platform and the reversal of the sedimentary properties of the Tadong deep water basin. We suggested that the Tarim Basin had a composite property of intracratonic and craton-margin depressions during the depositional period of Yijianfang Formation,yet overlapped by the foreland basin(Tangnan forbulge and Shunnan-Tanggubasi-Yudong back-bulge)at the southern part of the Taxi intracratonic depression and the extension basin(Kalpin craton-margin extension basin)at the northwestern part of the Taxi intracratonic depression. The tectonic-depositional environment and proto-type basin during the depositional period of Middle Ordovician Yijianfang Formation in Tarim Basin was a response to peripheral tectonic movements.