Characteristics Of Sedimentary And Fill Sequence In Cretaceous Of Sunwu-Jiayin Basin

Sunwu-Jiayin basin locates the north of Heilongjiang Province, covers the area of E126°31′～130°41′,N48°00′～49°58′.Sunwu- Jiayin basin lies in north of Songnen landmass. The east border of the basin is the Jiayin-Mudanjiang fault and adjacent to Jimusi landmass. South-Southwest of the basin and the Song liaobasin are divided by the Xiao Hinggan Mountains. The west border of the basin is the Erlian-Heihe suture zone and adjacent to Hinggan landmass. The basin is linked together with Jeya-Breya basin with the total area of the basin is 75102km2. Sunwujiayin basin accounts for only small part of the total basin area, about 20102km2.The land facies sedimentary palaeogeo graphical of Northeast area have obvious orderliness: The area between the Nenjiang lithosphere fault and Jia-Yi fault is main the land facies source bed sedimentary of the Cretaceous. Sunwu-Jiayin basin and Songliao basin also lie in this area and there are much comparability in the main formations of these two basins. Sunwu-Jiayin basin's formations include: Ningyuancun formation and Taoqihe formation in Lower Cretaceous, Yongancun formation, Taipinglinchang formation and Yuliangzi formation in Upper Cretaceous.Because of structure compression in late Lower Cretaceous, the basin has a depositional break period, which losts some stratum corresponding with Quantou formation and Qing- shankou formation of the Songliao basin.This fact reflects the tectonic movement of Sunwu-Jiayin basin was still frequently and intensively.We initially analyses the sequence stratigraphy of the basin by using the core in- formation and well log information of the two drilling wells(JiaD1 well, JiaD2 well), 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 3 second order sequences(structure sequence) and 9 third order sequences. We also analyse the development characteristic of the different order sequencesWe totally identify 5 kinds sedimentary facies: fluvial facies, fan-delta facies, delta facies, lacustrine facies and sublacustrine fan facies,11 kinds subfacies, 25 kinds microfacies by using information of outcrop,core,loging and seismic, associating with slice grading analysis. The sedimentary period of Ningyuancun formation's mainly develops lacustrine facies-sublacustrine fan facies cliping volcanic rock sedimentary system also including intermediate acidity volcanic rock and athrogenic rock; The sedimentary period of Taoqihe formation's mainly develops fan-delta facies-sublacustrine fan facies-lacustrine facies sedimentary system; The sedimentary period of Yongancun formation's mainly develops (fan)delta facies -lacustrine facies sedimentary system; The sedimentary period of Taipinglinchang formation's mainly develops lacustrine cliping density current facies-delta facies sedimentary system. The sedimentary period of Yuliangzi formation's mainly develops braid river facies sedimentary system. We emphasize on completing the slice grading analysis and summary the each subfacies'size parameter variety of the sublacustrine fan facies.The sedimentary and tectonic evolution of the basin is very similar with Songliao basin except losting some stratum corresponding with Quantou formation and Qingshankou formation. From Ningyuancun formation in Lower Cretaceous to Yuliangzi formation in Upper Cretaceous, the basin's vertical fill experienced lacustrine facies- sublacustrine fan facies clipping volcanic rock-lacustrine facies- sublacustrine fan facies-(fan)delta facies, lacustrine facies-lacustrine cliping density current facies,delta facies-braid river facies, corresponding with the tension-crack and rift-uplift-depression and subsidence-extruding and abortion of the basin's tectonic evolution.By using clastic rock light and heavy minerals array, Dinkinson illustration and clastic rock geochemistry manner and associating with regional geology formation, we can conclude that the basin's mother rock of provenance are main granitic rock, intermediate acidity volcanic rock and low grade metamorphic rock, also including medium-high metamorphic rock and sedimentary rock. The tectonic structure attribution of provenance is main active continental margin and continental arc, also including ocean arc. According to above, we confirm that Xiao Hinggan Mountains and Jimusi landmass is the two main provenance of Sunwu-jiayin basin. From Taoqihe formation in Lower Cretaceous to Taipinglinchang formation in Upper Cretaceous, Sunwu-jiayin basin connected with Songliao basin in the period of Taipinglinchang formation lower section(the first section and second section of Nenjiang formation) and the two basins were always divided and independent basins in other time; Jimusi landmass had been a main provenance at East of Sunwu-jiayin basin all the time in Cretaceous,while Xiao Hinggan Mountains had also been a main provenance of Sunwu-jiayin basin all the time in Cretaceous except in the period of Taipinglinchang formation lower section(the first section and second section of Nenjiang formation).