Orbital cyclicity in sedimentary sequence and climatic indications of C-O isotopes from Lower Cretaceous in Qingxi Sag, Jiuquan Basin, NW China

Siding Jin; Haiyang Cao; Hua Wang; Michael Wagreich; Sylvain Richoz

doi:10.1016/j.gsf.2018.01.005

Volume 10 Issue 2

Jan. 2021

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Siding Jin, Haiyang Cao, Hua Wang, Michael Wagreich, Sylvain Richoz. Orbital cyclicity in sedimentary sequence and climatic indications of C-O isotopes from Lower Cretaceous in Qingxi Sag, Jiuquan Basin, NW China[J]. Geoscience Frontiers, 2019, 10(2): 467-479. doi: 10.1016/j.gsf.2018.01.005

Citation:

Siding Jin, Haiyang Cao, Hua Wang, Michael Wagreich, Sylvain Richoz. Orbital cyclicity in sedimentary sequence and climatic indications of C-O isotopes from Lower Cretaceous in Qingxi Sag, Jiuquan Basin, NW China[J]. Geoscience Frontiers, 2019, 10(2): 467-479. doi: 10.1016/j.gsf.2018.01.005

Citation:

Siding Jin, Haiyang Cao, Hua Wang, Michael Wagreich, Sylvain Richoz. Orbital cyclicity in sedimentary sequence and climatic indications of C-O isotopes from Lower Cretaceous in Qingxi Sag, Jiuquan Basin, NW China[J]. Geoscience Frontiers, 2019, 10(2): 467-479. doi: 10.1016/j.gsf.2018.01.005

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Orbital cyclicity in sedimentary sequence and climatic indications of C-O isotopes from Lower Cretaceous in Qingxi Sag, Jiuquan Basin, NW China

doi: 10.1016/j.gsf.2018.01.005

a State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Chengdu University of Technology, Chengdu 610059, China;
b College of Energy Resources, Chengdu University of Technology, Chengdu 610059, China;
c Institute of Sedimentary Geology, Center for Post-doctoral Studies, Chengdu University of Technology, Chengdu 610059, China;
d Key Laboratory of Tectonics and Petroleum Resources, China University of Geosciences, Wuhan 430074, China;
e Department of Geodynamics and Sedimentology, University of Vienna, Althanstrasse 14, 1090 Wien, Austria;
f Institute of Earth Sciences, NAWI Graz, University of Graz, 8010 Graz, Austria

Received Date: 2017-01-14
Rev Recd Date: 2017-12-27
Publish Date: 2021-01-07

Abstract

Abstract

Sedimentary deposits of the Lower Cretaceous Xiagou Formation form the most significant potential hydrocarbon reservoirs in the Qingxi Sag, Jiuquan Basin (NW China). Zircon U-Pb ages of the dated basalts at the top of the Xiagou Formation give an isochron age of 115.6 Ma, and the sedimentation interval of the Xiagou Formation was speculated to range from about 125/124 Ma to 115 Ma based on paleontological research and stratigraphic correlation analysis. Here we use GR logging data as a palaeoenvironmental and palaeoclimatic proxy to conduct a detailed cyclostratigraphic study of five selected wells. Power spectra, evolutionary fast Fourier transformation and wavelet analysis all reveal significant sedimentary cycles in the Xiagou Formation. The ratios of cycle wavelengths in these stratigraphic units are 33.82 m:7.91 m:3.06 m:1.79 m, which is similar to the ratio of orbital targets of 20:5:2:1. The ratio of 20:5:2:1 is interpreted as Milankovitch cycles of 405 kyr long eccentricity, 100 kyr short eccentricity, 37 kyr obliquity, and 22 kyr precession cycles respectively. A high-resolution astronomical time scale is constructed by tuning the stratigraphy into target curves of orbital cycles respectively. Based on the astronomical time scale, the absolute ages of 55 samples were estimated, which are used for subsequent stable carbon and oxygen isotope stratigraphy analysis. The analysis results of the five studied wells in the Qingxi Sag indicate: (1) a negative trend of δ¹³C values upwards in the Xiagou Formation, and (2) negative δ¹⁸O values with a positive trend upwards. Both relatively heavy values and pronounced covariances of δ¹³C values and δ¹⁸O values indicate an arid-evaporation-controlled climate during the sedimentary period of the Lower Cretaceous Xiagou Formation, Qingxi Sag, Jiuquan Basin. Moreover, positive covariances of SQK_1g2+3 indicate extremely high temperature, and negative covariances of SQK_1g1 indicate a relatively low temperature.
- Jiuquan Basin,
- Qingxi Sag,
- Xiagou Formation,
- Orbital cyclicity,
- Stable isotope

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References(75)

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