Tectonic Characteristics And Tectonic Evolution Of Erlian Basin Bayindulan Depression

In order to choose most favorable oil exploration zone and reduce oil exploration risk, this project uses merged 3-Dimensional seismic data; In addition, it combines with logging and drilling data, guided by the principle of structural geologyfor the research of the sag tectonic characteristics and evolution.Bayindulan depression administrative region belongs to the west part of Dongwuqi in the Inner Mongolia Autonomous Region. Regional tectonic Bayindulan sag is located in the northeast part of Manite sag; on the north uplift is Bayinbaolige, nearly 80 km long and 16-20 km wide. The area is about 1200km2. In the plane, it is divided into south, central and north secondary sag that performed southeast fault and westnorth side over lappedtilt-block basin depression tectonic framework. The research showed that:(1) Generally, depression is a tilt-block basin structure with a double-break feature in the early stage and it controls the distribution of lake basin;(2) The depression is mainly developed three important fault – 1-level eastern subbasin-controlling faults, sediment-controlling faults of slope zone and 2-level central tectonic zone-controlling fault that controls trending and evolution of tectonic zone.(3) Depression mainly went through four tectonic movements. Rift faulting expansion in Aershan period is followed by volcanic activity and depression faulting transition of is followed by tectonic inversion are two important period of depression development and formation.(4) The depressions are divided into four secondary level tectonic units according to the principle of fault-controlling tectonic and sediment-controlling evolution. Each tectonic unit has a significant different.(5) The tectonic evolution characteristic is nearly similar between Bayindulan depression and the other depression of Erlian basin. It was a long-term, inheritance development and preserved relatively intact depression. Depression is emerged in the late Jurassic. Latterly, due to the influence of orogeny in the Yanshanian, the uplift of depression led to current tectonic structure. Depression began with the effect of rifting in the mid-period of Yanshanian movement. The west-east separate zone of depression tectonic framework is decided by continued developmentfrom northeast to boundary fault, west faulting and east-overlapping with tilt-block basin structure is formed. The period of Bayanhua group sedimentary in Cretaceous is the heyday period of depression development. According to the character of tectonic evolution and sediment-controlling, tectonic evolution development divides into four stages: early period of rift, rift development period, fault depression development period and atrophy period.(6)The research area is a fault depression developed over the substrate of Paleozoic. It mainly deposited a set of clastic rocks of Low Cretaceous. The Low Cretaceous generally constituted a completely sedimentary cycle with the style of large thick- thin – thick. During this period it experienced Late Jurassic, A fourth member later period of sedimentary of Cretaceous, the sedimentary late period of Teng first member, the sedimentary late period of Teng second member and sedimentary tectonic events in sedimentary later period of Saihantala group. It formatted large regional unconformity and sedimentary discontinuity for five times. Plate can be divided into five large phase like fan delta, lake, subaqueous fan, rivers and so on.