Carboniferous Sedimentation Facies And Sedimentation System Of The Northeastern Qaidam Basin

Based on field geology, sedimentation, stratigraphic paleontology, structure geology of the Qaidam basin, this paper focus on the Carboniferous sedimentation and distribution pattern in the northeastern Qaidam basin.Through sedimentation discrimination and systemic analysis of key section, which can reflect the vertical change of sedimentation, five sedimentation systems(i.e.,barrier bank; perezone, shallow sea, delta) and ten sedimentary ficies have been distinguished in the northeastern part of Qaidam basin. Carboniferous perezone platform sedimentation are well developed. Based on these features and two key section analysis, a "saddle model" , with two side rifted and continue sedimentation in the center, can be used to describe the distribution pattern of Carboniferous sedimentation in the northeastern part of Qaidam basin. These features indicate that a limited marine invasion in Early Carboniferous time, which is characterized by fill and level up. From Middle Carboniferous to Late Carboniferous time, the Qaidam basin experience a sequence of perezone, tidal platform, and platform with limited marine regression.Geological and sedimentation data of the Carboniferous system in the Qaidam basin indicate a good combination of hydrocarbon-source rocks, reservoir and cap rocks, Early Carboniferous argillaceous limestone and hermatbiolitho are good hydrocarbon source rocks, Late Carboniferous platform and marsh facies dark pelite is also good hydrocarbon source rocks. Early Carboniferous Amunike formation and Late Carboniferous Keluke formation constitutes a delta-perezone clastic reservoir, Early Carboniferous pelleted limestone constitute carbonate reservoir. Argillutites and argillaceous limestone in the study area constitute good cap rocks. Good cap rocks developed in overlying Mesozoic and Cenozoic layers.