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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

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Geoscience Frontiers 2019年第2期10卷 467-479页

作者： Siding Jin Haiyang Cao Hua Wang Michael Wagreich Sylvain Richoz State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation Chengdu University of Technology College of Energy Resources Chengdu University of Technology Institute of Sedimentary Geology Center for Post-doctoral StudiesChengdu University of Technology Key Laboratory of Tectonics and Petroleum Resources China University of Geosciences Department of Geodynamics and Sedimentology University of Vienna Institute of Earth Sciences NAWI GrazUniversity of Graz

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 δ^(13)C values upwards in the Xiagou Formation, and(2) negative δ^(18)O values with a positive trend upwards. Both relatively heavy values and pronounced covariances of δ^(13)C values and δ^(18)O values indicate an arid-evaporationcontrolled climate during the sedimentary period of the Lower Cretaceous Xiagou Formation, qingxi Sag, Jiuquan Basin. Moreover, positive covariances of SQK_1g_(2+3) indicate extremely high temperature, and negative covariances of SQK_1g_1 indicate a relatively low temperature.

关键词： Jiuquan Basin qingxi Sag Xiagou Formation Orbital cyclicity Stable isotope

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Returned Diplomats,French Engineers,and the qingxi Ironworks:Self-Strengthening and Self-Representation in the Late Qing

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Frontiers of History in China 2019年第1期14卷 82-108页

作者： Ke Ren Department of History College of the Holy CrossWorcesterMA 01610USA

This article explores the history of the qingxi Ironworks in late Qing Guizhou.Instead of focusing on state-centered industrialization or technology transfer and scientific knowledge in Qing mining and coal enterprises,this study focuses on the individual ambitions and identity construction of two returned diplomats——Chen Jitong and Chen Mingyuan—who sought to claim authority over a mining interest in China's southwest interior.By leveraging their knowledge of the West to serve as intermediaries between state and foreign commercial interests,these cosmopolitan yet marginalized elites sought to convert their foreign expertise and avowed commitment to "selCstrengthening" into new forms of social and political capital.An examination of the personal networks and written accounts surrounding their entrepreneurial ventures sheds light on the opportunities and challenges experienced by a generation of "foreign affkirs" experts in repositioning themselves within the transforming Qing polity through participation in industrialization projects.

关键词： self-strengthening mining qingxi Guizhou province Chen Jitong Chen Mingyuan

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