Tectonostratigraphic units and stratigraphic sequences of the nonmarine Songliao basin, northeast China
Tectonostratigraphic units and stratigraphic sequences of the nonmarine Songliao basin, northeast China
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DOI：
10.1111/j.1365-2117.2009.00445.x
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发表时间：
2010-02-01
期刊：
影响因子：
3.2
通讯作者：
Cross, Timothy A.
中科院分区：
文献类型：
--
作者：
Feng Zhi-qiang;Jia Cheng-zao;Cross, Timothy A.
通过对松辽非海相陆内盆地的构造地层学分析，确定了地幔上升流、裂谷、裂谷后热沉降和构造反转4期变形。这些事件与区域地球动力学和板块运动有关。每一段都与特定的地层特征有关。第一次变形发生在中晚侏罗世，软流圈上升流加热、变薄和拉伸岩石圈。这些事件可能是由鄂霍次克海的俯冲变窄造成的。这种变形的特点是穹隆、伸展、广泛的火山活动和侵入以及侵蚀。火山指间带冲积扇和冲积平原相体系域。第二次裂谷期开始于侏罗纪晚期，一直持续到白垩纪早期。形成了大量孤立的北北东向“盆岭”断块。裂谷可能是由伊扎那吉板块和太平洋板块的形成和俯冲引起的。断块盆地发育含煤河流、洪泛平原、湖相、扇三角洲地层和广泛分布的火山岩。裂谷期盆地火石岭组和营城组厚达数百~数千米的火山地层记录了多次侵入事件。这些事件与东北地区的入侵和火山喷发事件同时发生。从下白垩统登娄库组开始的第三期区域性走后变形沉降是由岩石圈冷却和伸展引起的，受多次挤压事件的调节。与蒙古和东北亚其他白垩系盆地不同，松辽盆地的沉降使其形成了较厚的后裂谷沉积。鄂霍次克缝合带的发育和太平洋板块的俯冲形成了3次挤压期，间断性地中断了长期的冷却沉降。早白垩世，鄂霍次克海的闭合形成了明显的挤压作用，形成了大兴安岭山脉，为盆地北部提供了沉积物。在晚白垩世，太平洋边缘的挤压强度随着时间的推移而增加，导致沉积中心向西迁移，东部隆升，直到白垩纪末期。裂谷后地层厚度一般为3000 ~ 4000 m，最大厚度可达6000 m，延伸至断陷块体之外，覆盖盆地边缘，形成一个大型均匀盆地。早期热沉降地层包括冲积扇、河流、漫滩、浅湖相和三角洲相带，上覆大型三角洲和湖泊相。晚后期环境以盆地中心的大型湖泊为特征，周围为三角洲、河流和洪泛平原环境。反射地震剖面显示，该地区褶皱和隆升等强烈的构造反转始于白垩纪末。白垩纪末期主挤压应力场由NW向NWW转变，导致褶皱方向发生变化。在裂谷期，河流三角洲地层与储层火山岩、河流三角洲砂岩、扇三角洲砂岩中形成多套含气储层与含煤烃源岩相结合。后裂谷期沉积于深湖的厚而广布的泥岩含有丰富的有机质，是重要的烃源岩和区域盖层。良好的储层产于三角洲和河流地层。由于幕式挤压事件交替引起沉降和隆起，储层夹在烃源岩之间，提供了从烃源岩到储层的直接流体通信。
Through tectonostratigraphic analysis of the nonmarine, intracontinental Songliao basin in northeast China, four episodes of deformation are recognized: mantle upwelling, rift, postrift thermal subsidence and structural inversion. The episodes are related to regional geodynamics and plate motions. Each episode is associated with a specific stratigraphic signature. The first period of deformation occurred during the Middle and Late Jurassic when asthenospheric upwelling heated, thinned and stretched the lithosphere. These events may have been caused by the narrowing of the Okhotsk Sea through subduction. This deformation is characterized by doming, extension, widespread volcanism and intrusion, and erosion. Volcanics interfinger with alluvial fan and alluvial plain facies systems tracts. The second rifting episode began in the latest Jurassic and continued into the Early Cretaceous. It resulted in the formation of a large number of isolated, NNE-trending fault blocks of 'basin-and-range' style. Rifting may have been caused by the formation and subduction of the Izanagi and Pacific Plates. Coal-bearing fluvial, floodplain, lacustrine and fan-delta strata and widespread volcanic rocks filled the fault-block basins. Volcanic strata hundreds to several thousand meters thick in the Huoshiling and Yingcheng Formations record multiple intrusive events during the rifting stage in the basin. These events were concurrent with episodes of intrusion and volcanic eruption in northeast China. The third phase of regional postrift deformation and subsidence, which began with the Lower Cretaceous Denglouku Formation, was caused by lithospheric cooling and extension, modulated by multiple compressional events. Subsidence in the Songliao basin permitted accumulation of thick postrift deposits, in contrast with other Cretaceous basins in Mongolia and northeast Asia. Three compressional episodes, which episodically interrupted the long-term cooling subsidence, originated from development of the Okhotsk suture and subduction of the Pacific plate. In the Early Cretaceous, pronounced compression originated from closure of Okhotsk Sea, forming the mountain ranges of Daxinganling, which provided sediment to the northern part of the basin. In the Late Cretaceous, the intensity of compression from the Pacific margin increased through time, causing westward migration of depocentres and uplift in the east until the end of Cretaceous. Postrift strata, typically 3000-4000 m thick with a maximum thickness of 6000 m, extend beyond the rift blocks and onlap the basin margins to form a large uniform basin. Early thermal subsidence strata include alluvial fan, fluvial, floodplain, shallow lacustrine and delta facies tracts, overlain by large deltaic and lacustrine facies. Late postrift environments featured by large lakes in the basin centre rimmed by delta, fluvial and floodplain environments. Reflection seismic profiles show that strong structural inversion, including folding and uplift, began at the end of the Nenjiang Formation and culminated at the end of the Cretaceous. The main compressional stress field changed from NW to NWW at the end of the Cretaceous, which caused changes in the direction of folding. During the rifting stage, several sets of gas-bearing reservoirs formed in association with coal-bearing source rocks in fluvial and deltaic strata with reservoir-quality volcanics and fluvial and fan-delta sandstone.Thick, widespread mudstone deposited in deep lakes during the postrift stage contains abundant organic matter, and is an important source rock and rgional cap rock. Good reservoirs occur in deltaic and fluvial strata. Because of the episodic compressional events that alternately caused subsidence and uplift, reservoirs are sandwiched between source rocks, providing direct fluid communication from source to reservoir.