Characteristics Of Sedimentary And Evolution Of Sanjiang Basin In Eastern Heilongjiang Province

Sangjiang basin locates the northeast of Heilongjiang Province,covers the area of E130°10′～135°00′,N 46°25′～48°25′.The basin is linked together with Zhongemuer basin with the total area of the basin is 90370km~2.Sanjiang basin accounts for only small part of the total basin area,about 33730 km~2.The main body of Sanjiang basin lies in Jimusi landmass.The west border of the basin is adjacent to Zhangguangcai Mountain drape orogenic belt in Paleozoic which belong to Tianshan- Hinggan drape orogenic belt.The east border of the basin is nadanhada Mountain drape orogenic belt in Mesozoic.Sanjiang basin's formations include:Suibin formation and Dongrong formation in Jurassic,Didao formation,Chengzihe formation,Muleng formation and Dongshan formation in Lower Cretaceous,Houshigou formation,Hailang formation,Qixianghe formation and Yanwo formation in Upper Cretaceous. Baoquanling formation and Fujin formation in Tertiary.The relationship between Suibin formation,dongrong formation and Didao formation,Chengzihe formation is angular unconformity;The relationship between Muleng formation and Dongshan formation is also angular unconformity,and the same as the relationship between baoquanling formation in Tertiary and yanwo formation in Cretaceous.We initially analyses the sequence stratigraphy of the basin by using the core in- formation and well log information of the seven drilling wells,a little seismic and field outcrop information.According to the basin's sedimentary characteristic, the identification sign of the sequence interface and systems tract classified in the sequence inner,we establish the sequence stratigraphy framework of Sunwu-Jiayin basin.We totally identify 5 second order sequences(structure sequence)and 16 third order sequences.We also analyse the development characteristic of the different order sequences.The sedimentary facies in Sanjiang basin is mainly composed of continental facies,and still including marine event sediments in the background of continent, which form the rich and colorful sedimentary systems of the area.We totally identify 6 kinds sedimentary facies:fluvial facies,fan-delta facies,delta facies, lacustrine facies,sublacustrine fan facies and marine facies,16 kinds subfacies, 31kinds microfacies by using information of outcrop,core,loging and seismic, associating with slice grading analysis.The sedimentary period of Suibin formation and Dongrong formation's mainly develops offshore and shallow marine facies;The sedimentary period of Didao formation,Chengzihe formation and Muleng formation's mainly develops fan-delta facies-shallow lake facies sedimentary system;The sedimentary period of Dongshan formation's mainly develops(fan)delta facies-shallow lake-semi-lake sedimentary systems;The sedimentary period of Upper Cretaceous and Tertiary mainly develops alluvial fan -fluvial facies- shallow lake sedimentary system.By using elastic rock light and heavy minerals array and elastic rock geochemistry manner and associating with regional geology formation,we can conclude that the basin's mother rock of provenance are main metamorphic rock, intermediate acidity volcanic rock-intermediate basic volcanic rock,also including sedimentary rock.The tectonic structure attribution of provenance is main active continental margin and continental arc.According to above,we confirm that Huanan upheaval,eastern Sanjiang aera and Xiaoxinganling aera are the three main provenances of Sangjiang basin. According to stratigraphic unconformity,Late Mesozoic basins would be divided into four Structural layers,The evolution of the basin have three extension stages in different structural settings and three tectonic inversion stages.The formation and evolution of Heilongjiang eastern basins are impacted by Mongolia-Okhotsk Sea collision and closure,and which also are controlled by the subduction of the eastem Pacific plate and matching among some foreign bodies. The local mantle convection and significant lithospheric thinning caused by the subduction from the Pacific Plate to the mainland are mainly basin-formed dynamics mechanism.