Origin of abnormal pressure in the Upper Paleozoic shale of the Ordos Basin, China

2019 ◽  
Vol 110 ◽  
pp. 162-177
Author(s):  
Jun Li ◽  
Jingzhou Zhao ◽  
Xinshan Wei ◽  
Mengna Chen ◽  
Ping Song ◽  
...  
Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Jiaxuan Song ◽  
Hujun Gong ◽  
Jingli Yao ◽  
Huitao Zhao ◽  
Xiaohui Zhao ◽  
...  

The Paleozoic strata are widely distributed in the northwest of the Ordos Basin, and the provenance attributes of the basin sediments during this period are still controversial. In this paper, the detrital zircon LA-MC-ICPMS U-Pb age test was conducted on the drilling core samples of the Shanxi Formation of the Upper Paleozoic in the Otuokeqi area of the Ordos Basin, and the provenance age and the characteristic of the Shanxi formation in the Otuokeqi area in the northwest were discussed. The cathodoluminescence image shows that the detrital zircon has a clear core-edge structure, and most of the cores have clear oscillatory zonings, which suggests that they are magmatic in origin. Zircons have no oscillatory zoning structure that shows the cause of metamorphism. The age of detrital zircon is dominated by Paleoproterozoic and can be divided into four groups, which are 2500~2300 Ma, 2100~1600 Ma, 470~400 Ma, and 360~260 Ma. The first two groups are the specific manifestations of the Precambrian Fuping Movement (2.5 billion years) and the Luliang Movement (1.8 billion years) of the North China Craton. The third and fourth groups of detrital zircons mainly come from Paleozoic magmatic rocks formed by the subduction and collision of the Siberian plate and the North China plate. The ε Hf t value of zircon ranges from -18.36 to 4.33, and the age of the second-order Hf model T DM 2 ranges from 2491 to 1175 Ma. The source rock reflecting the provenance of the sediments comes from the material recycling of the Paleoproterozoic and Mesoproterozoic in the crust, combined with the Meso-Neoproterozoic detrital zircons discovered this time, indicating that the provenance area has experienced Greenwellian orogeny.


Energies ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2694
Author(s):  
Guanqun Yang ◽  
Wenhui Huang ◽  
Jianhua Zhong ◽  
Ningliang Sun

The detailed characteristics and formation mechanisms of organic-rich clasts (ORCs) in the Upper Paleozoic tight sandstone in the northeastern margin of the Ordos Basin were analyzed through 818-m-long drilling cores and logging data from 28 wells. In general, compared with soft-sediment clasts documented in other sedimentary environments, organic-rich clasts in coal-bearing tight sandstone have not been adequately investigated in the literature. ORCs are widely developed in various sedimentary environments of coal-bearing sandstone, including fluvial channels, crevasse splays, tidal channels, sand flats, and subaqueous debris flow deposits. In addition to being controlled by the water flow energy and transportation processes, the fragmentation degree and morphology of ORCs are also related to their content of higher plants organic matter. The change in water flow energy during transportation makes the ORCs show obvious mechanical depositional differentiation. Four main types of ORC can be recognized in the deposits: diamictic organic-rich clasts, floating organic-rich clasts, loaded lamellar organic-rich clasts, and thin interlayer organic-rich clasts. The relationship between energy variation and ORCs deposition continuity is rarely studied so far. Based on the different handling processes under the control of water flow energy changes, we propose two ORCs formation mechanisms: the long-term altering of continuous water flow and the short-term water flow acting triggered by sudden events.


2012 ◽  
Vol 3 (6) ◽  
pp. 863-873 ◽  
Author(s):  
Xuan Tang ◽  
Jinchuan Zhang ◽  
Yansheng Shan ◽  
Jinyu Xiong

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