Structural architecture of Neoproterozoic rifting depression groups in the Tarim Basin and their formation dynamics

Abstract

The Tarim Basin is the largest oil-bearing superimposed basin in northwestern China. The evolution and tectonic properties of the initial Tarim Basin have been hotly disputed and remain enigmatic. The Neoproterozoic basin is covered by a vast desert, and a huge thickness of sedimentary strata has experienced multiple tectonic movements and has low signal-to-noise ratios (SNRs) of seismic reflection data, all of which have posed critical obstacles to research. We analysed four field outcrops, 18 wells distributed throughout the basin, 27 reprocessed seismic reflection profiles with higher SNRs across the basin and many ancillary local 2D and 3D profiles and aeromagnetic data. We found about 20 normal fault-controlled rift-related depressions of Cryogenian and Ediacaran age scattered throughout the basin, which developed on the Precambrian metamorphic and crystalline basement. The structural framework is clearly different from that of the overlying Phanerozoic strata. The rifting depressions consist of mainly half grabens, symmetrical troughs and horst-grabens. From the northeast to southwest of the basin, they are divided into three rifting depression groups with WNW, ENE, and NW-trends that are mainly controlled by normal faults. The maximum thicknesses of the strata are up to 4100 m. From the Cryogenian to Ediacaran, most of the main inherited faults were active and eventually ceased at the end of the Ediacaran or Early Cambrian, whereas subsidence subsidence centres appeared and migrated eastwards along the faults. They revealed that the different parts of the Tarim continental block were in NNE-SSW-oriented and NNW-SSE-oriented extensional paleo-stress fields (relative to the present) during the Neoproterozoic, and were accompanied by clockwise shearing. According to the analysis of the activities of syn-sedimentary faults, filling sediments, magmatic events, and coordination with aeromagnetic anomalies, the tectonic properties of the fault depressions are different and reflect primarily continental rifts or intra-continental fault-controlled basins. The rifting phases mainly occurred from 0.8-0.61 Ga. The formation of the rifting depression was associated with the initial opening of the South Altun-West Kunlun Ocean and the South Tianshan Ocean, which were located at the northern and southern margins of the Tarim Block, respectively, in response to the break-up of the supercontinent Rodinia and the initial opening of the Proto-Tethys Ocean.

Aeromagnetic-Imaged Basement Fault Structure of the Eastern Tarim Basin and Its Tectonic Implication

“…The block between F1 and F2 shows the highest susceptibility with 4,000 × 10 −5 SI, which is higher than the average susceptibilities of Archean metamorphic rocks with 2,300 × 10 −5 SI, but is consistent with the average susceptibilities of Ar 2 tg measured in the Vermiculite Mining Area located in Kuruktag. The Neoproterozoic rift center is located in the Northeastern Mangal Domain based on the seismic interpretation (Ren et al, 2017;He et al, 2019). If magmatic rocks related to the rift were the main factor to cause high magnetic anomalies, the Northeastern Mangal Domain would have the highest magnetic anomalies.…”

“…The Tarim Basin is located in the southern region of Xinjiang Uygur Autonomous Region, China, between Tianshan Mountains and Western Kunlun-Altun Mountains (Figure 1). The basin is a large marine-continental depositional compound basin after experiencing multistage tectonic activities (Xu et al, 2013;Wu et al, 2018;He et al, 2019;Xu et al, 2021). After the initial continental crustal evolution in the Archean, the Tarim Craton was developed during the Proterozoic and Paleozoic by the accretion of the Kunlun, Qaidam, Tarim block, and the Central/South Tian Shan block (Charvet et al, 2007;Lin et al, 2013;Zhang C.-L et al, 2013;Zhang P. Z et al, 2013;Li et al, 2018), and by the extensional activities from the Neoproterozoic to Ordovician (Dong et al, 2016;Zhu et al, 2017;Ren et al, 2018;Wu et al, 2018).…”

“…The beginning of sedimentary strata may be traced to the Late Paleozoic or the Neoproterozoic (Guo et al, 2015;Wu et al, 2018;He et al, 2019). According to the drilling and industry seismic data, the Eastern Tarim Basin deposited the marine Neoproterozoic, Cambrian, Ordovician, Silurian, Devonian, Carboniferous and the continental Jurassic, Cretaceous, and Cenozoic strata, but not Permian and Triassic strata (Zhang C.-L et al, 2013;Xu et al, 2014).…”

“…), it can be seen that the magnetic anomaly values and the susceptibilities do not decrease sharply from south to north in the Central Tadong Domain and Northeastern Mangal Domain. Furthermore, the disordered strikes of the northern boundary(Yang et al, 2012;Lin et al, 2015;He et al, 2019) of the Central Highly Magnetic Anomaly Belt reveal a possible extension in the Northeastern Mangal Domain. Considering the similar evolution history of the Northeastern Mangal Domain and Central Tadong Domain after…”

Analysis of proto-type Tarim Basin in the late Precambrian and the dynamic mechanism of its evolution

“…Tarim block had experienced several stages of tectonic evolution in the Precambrian, with both similarities and dissimilarities to the south and north Tarim blocks in many aspects [ 2 , 17 , 18 , 22 , 24 , 27 ]. Figuring out the plate tectonic history would help to understand how Tarim Basin came into being and how the subbasins inside Tarim Basin have evolved [ 20 , 28 , 29 ].…”