Skip to main content

Lund University Publications

LUND UNIVERSITY LIBRARIES

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

Jin, Siding ; Cao, Haiyang ; Wang, Hua ; Wagreich, Michael and Richoz, Sylvain LU (2019) In Geoscience Frontiers 10(2). p.467-479
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... (More)


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-evaporation-controlled climate during the sedimentary period of the Lower Cretaceous Xiagou Formation, Qingxi Sag, Jiuquan Basin. Moreover, positive covariances of SQK
1
g
2+3
indicate extremely high temperature, and negative covariances of SQK
1
g
1
indicate a relatively low temperature.

(Less)
Please use this url to cite or link to this publication:
author
; ; ; and
publishing date
type
Contribution to journal
publication status
published
keywords
Jiuquan Basin, Orbital cyclicity, Qingxi Sag, Stable isotope, Xiagou Formation
in
Geoscience Frontiers
volume
10
issue
2
pages
13 pages
publisher
China University of Geosciences (Beijing) and Peking University
external identifiers
  • scopus:85050865130
ISSN
1674-9871
DOI
10.1016/j.gsf.2018.01.005
language
English
LU publication?
no
id
814246f0-6cf2-4bf8-bf74-07223f12409c
date added to LUP
2019-05-09 15:03:05
date last changed
2022-04-25 23:23:09
@article{814246f0-6cf2-4bf8-bf74-07223f12409c,
  abstract     = {{<p><br>
                                                         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                             <br>
                            <sup>13</sup><br>
                                                         C values upwards in the Xiagou Formation, and (2) negative δ                             <br>
                            <sup>18</sup><br>
                                                         O values with a positive trend upwards. Both relatively heavy values and pronounced covariances of δ                             <br>
                            <sup>13</sup><br>
                                                         C values and δ                             <br>
                            <sup>18</sup><br>
                                                         O 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                             <br>
                            <sub>1</sub><br>
                                                         g                             <br>
                            <sub>2+3</sub><br>
                                                          indicate extremely high temperature, and negative covariances of SQK                             <br>
                            <sub>1</sub><br>
                                                         g                             <br>
                            <sub>1</sub><br>
                                                          indicate a relatively low temperature.                         <br>
                        </p>}},
  author       = {{Jin, Siding and Cao, Haiyang and Wang, Hua and Wagreich, Michael and Richoz, Sylvain}},
  issn         = {{1674-9871}},
  keywords     = {{Jiuquan Basin; Orbital cyclicity; Qingxi Sag; Stable isotope; Xiagou Formation}},
  language     = {{eng}},
  month        = {{03}},
  number       = {{2}},
  pages        = {{467--479}},
  publisher    = {{China University of Geosciences (Beijing) and Peking University}},
  series       = {{Geoscience Frontiers}},
  title        = {{Orbital cyclicity in sedimentary sequence and climatic indications of C-O isotopes from Lower Cretaceous in Qingxi Sag, Jiuquan Basin, NW China}},
  url          = {{http://dx.doi.org/10.1016/j.gsf.2018.01.005}},
  doi          = {{10.1016/j.gsf.2018.01.005}},
  volume       = {{10}},
  year         = {{2019}},
}