Based on the outcrop, drilling and seismic data, the sedimentary successions, evolution and hydrocarbon exploration potential of the Neoproterozoic rift basin in the northern Tarim were firstly analyzed. Due to assembly and breakup of the Rodinia supercontinent, the Tabei paleocontinent and the Tarim paleocontinent were developed in the Tarim craton with an EW-trending back-arc rift basin between them during Neoproterozoic time; very thick marine clastic rocks, carbonate rocks and volcanic rocks (including tillite) were deposited in the Kuruktag and Aksu area of the northern Tarim, which experienced deep sea, bathyal sea and littoral sea environments with transitional delta and ice-sea. During the Early Cryogenian and the Late Ediacaran, the northern rift basin evolved from the deep sea to the littoral-neritic sea, while the lithology changed from clastic rocks to carbonate rocks. According to the field and production data, the formation and preservation of the source rocks and reservoirs indicate a good exploration potential of the Neoproterozoic rift basin.
Abstract: In January 2010, the Suining M s5.0 earthquake occurred in central Sichuan Basin, with the epicenter in Moxi‐Longnvsi structural belt and a focal depth of 10 km. Based on structural interpretations of seismic profiles in this area, we recognized a regional detachment fault located at a depth of 9–10 km in the Presinian basement of the Suining area, transferring its slipping from NW to SE orientation. This detachment fault slipped from NW to SE, and underwent several shears and bends, which caused the basement to be rolled in and the overlaying strata fold deformation. It formed a fault‐bend fold in the Moxi area with an approximate slip of 4 km. Correspondingly, the formation of the Moxi anticline is related to the detachment fault. With the earthquake's epicenter on the ramp of the detachment fault, there is a new point of view that the Suining earthquake was caused by re‐activation of this basement detachment fault. Since the Late Jurassic period, under the influence of regional tectonic stress, the detachment fault transfered its slip from the Longmen Mountains (LMS) thrust belt to the hinterland of the Sichuan Basin, and finally to the piedmont zone of southwest Huayingshan (HYS), which indicates that HYS might be the final front area of the LMS thrust belt.
The Tarim Craton, China, records several significant events in the history of the Rodinia supercontinent, including Neoproterozoic glaciations and rift evolution. In this study, we use geochronological, geochemical, and geophysical data from the Aksu region, northwest Tarim Craton, to investigate the rifting history and three discrete Cryogenian glaciations in the Tarim Craton. A total of 268 concordant zircon U–Pb ages were obtained from three samples in the lowermost unit of the Cryogenian Xifangshan Formation. These ages define four Neoproterozoic populations of ca. 975–900, 885–810, 795–755, and 740–720 Ma, which reflect magmatic events in the Rodinia supercontinent. The age of the Xifangshan Formation is constrained by two maximum depositional ages of 739 ± 9 Ma and 719 ± 7 Ma, suggesting a stratigraphic correlation with the Cryogenian Baiyisi Formation in the Kuruktag region, northeast Tarim Craton. Field and geochemical evidence identify three discrete Cryogenian glaciations in the Aksu region, which are the Xifangshan, Qiaoenbrak, and Youermeinark glaciations that can be chronologically correlated with the Baiyisi, Altungal, and Tereeken glaciations in the Kuruktag region, respectively. The northern rift basin in the Aksu region formed at ca. 740 Ma and is filled by a thick Cryogenian volcanic–sedimentary succession. This rift basin gradually expanded to entire northern Tarim Craton, with sediments being unconformably deposited on underlying formations. Although large-scale deformation occurred in the late Ediacaran, corresponding to the Pan-African orogeny, the Aksu rift depocentre was covered with a series of deep-water rocks in the Early Cambrian and Ordovician.
Abstract The Bayin River, the largest river in the northeastern Qaidam basin, plays an important role in the source‐to‐sink system and landscape evolution at the basin‐mountain boundary between the Qilian Mountains and the Qaidam basin in the northern Tibetan Plateau. In this study, we conduct field observation, topographic analysis, zircon U–Pb dating, and apatite (U–Th)/He dating to constrain the landscape and tectonic evolution of the Bayin River watershed. Bedrock zircon U–Pb dating indicates the age group of 420–450 Ma for far‐source sediments and the age group of >1,700 Ma for near‐source sediments in the Bayin River watershed. Detrital zircon U–Pb dating results from the Mesozoic and Cenozoic strata in the Bayin River watershed reveal that the most important source transition occurred during the Cretaceous. The Zongwulong Mountains gradually uplifted throughout the Cenozoic, along with decreasing far source and increasing near source based on detrital zircon U–Pb dating. Rapid uplift occurred across the Qilian Mountains during the late Cenozoic, leading to high normalized steepness indices, young apatite (U–Th)/He ages, and deep incised valleys at the basin‐mountain transition zone. The knickpoints caused by the latest headward erosion just reach an elevation of ~3,800 m on the river longitudinal profiles, indicating that the latest uplift magnitude is ~300–400 m relative to the basin surface of the Qaidam basin. Elevation distribution and apatite (U–Th)/He ages reveal that river incision leads to high relief in the Zongwulong Mountains and influences its tectonic evolution.
According to the distribution and transfer directions of thrust displacements under which the size, shape and pattern of thrust belt are controlled, the foreland thrust belts are classified into four types in middle and western China: (1) Type I, all the fault displacements in the thrust belt transfer from the mountain front to the basin along detachment. This type is the most popular in central and western China and can be divided into three subtypes: Kuche type, southwestern Sichuan type and Jiuquan type. (2) Type II, represented by southern Junggar Basin, in which there are fault displacements transferring to both basin and orogenic belt directions. (3) Type III, represented by Fusha thrust belt in southwestern Tarim Basin, in which all the fault displacements transfer toward the mountain front as deep structural wedges propagating toward the basin direction. (4) Type IV, represented by southwestern and northern Qaidam Basin, in which the transfer of fault displacements is restrained by the size, shape and boundary of the basin, and the stable foreland part and typical wedge sedimentary structure not produced. On basis of the above four types and the modeling of complicated structures, four new exploration areas are identified: the deep imbricate structural wedges in southern Junggar Basin, late Paleozoic passive continental margin sequence under the reverse Cambrian nappe in northwestern Sichuan, under-coal structures in middle and eastern Kuche, and footwall covered structures in northwestern Junggar Basin.
Using field geological survey, drilling and seismic data, combined with the study of regional tectonic evolution and structural deformation, as well as lithological and sedimentary analysis, we reconstructed the basin filling process and paleo-geography of north Tarim Basin in Early Cambrian, aiming to analyze the factors controlling the distribution and spatial architecture of the subsalt reservoir and source units and to define the favorable exploration direction. The Late Sinian tectonic activities in the northern Tarim Basin were characterized by different patterns in different areas, which controlled the sedimentary pattern in the Early Cambrian. The boundary faults of Nanhuaian rift basin in the south slope of Tabei uplift and the north slope of Tazhong uplift became reactivated in the Early Cambrian, forming two NEE and EW striking subsidence centers and depocenters, where the predicted thickness of the Yurtusi Formation could reach 250 meters. In the Xiaoerbulake period, the weak rimmed platform was developed in the hanging wall of syndepositional fault. Whereas the Nanhuaian rift system in the Tadong and Manxi areas were uplifted and destroyed in the Late Sinian, and appeared as gently slope transiting toward the subsidence center in the Early Cambrian. The former had the sedimentary features of hybrid facies platform and the latter had the sedimentary features of ramp platform. The black shale of the Yurtus Formation in the footwall of syndepositional fault and the reef bank of Xiaoerbulake Formation platform margin in the hanging wall in Early Cambrian constitute a predicable source-reservoir combination. The activity intensity of syndepositional fault controlled the thickness of black shale and the scale of the reef bank. It is suggested carrying out high accuracy seismic exploration to determine the location of Early Cambrian syndepositional faults, on this basis, to search the reef bank of Xiaoerbulake Formation along the faults westward, and then drill risk exploration wells at sites where traps are shallow in buried depth.
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