Palaeoclimatic influence on lake palaeoenvironment and organic matter accumulation in the Middle Jurassic Shimengou formation (Qaidam basin, NW China)

Kai Zhou; Minfang Yang; Jing Lu; Ran Gao; Lihong Tong; Lusheng Yin; Peixin Zhang; Wanqing Wang; Hongqing Liu; Longyi Shao; Jason Hilton

doi:10.1016/j.geoen.2023.212581

Palaeoclimatic influence on lake palaeoenvironment and organic matter accumulation in the Middle Jurassic Shimengou formation (Qaidam basin, NW China)

Kai Zhou, Minfang Yang, Jing Lu^*, Ran Gao, Lihong Tong, Lusheng Yin, Peixin Zhang, Wanqing Wang, Hongqing Liu, Longyi Shao, Jason Hilton

^*Corresponding author for this work

Earth and Environmental Sciences

Research output: Contribution to journal › Article › peer-review

Abstract

The formation and accumulation of lacustrine organic-rich shales are strongly related to palaeoclimate and palaeoenvironmental conditions. Middle Jurassic organic-rich lacustrine shales in the Qaidam Basin, NW China, are important source rocks for unconventional oil and gas exploration, but factors controlling their organic matter (OM) abundance and preservation are unclear. To understand how palaeoclimate and palaeoenvironmental conditions influenced depositional processes and elucidate the factors controlling OM accumulation of lacustrine organic-rich shales, we investigated total organic carbon (TOC), mineral compositions, and element geochemistry the Shale Member of the Middle Jurassic (J2s2) Shimengou Formation from the Yuqia Coalfield in the Qaidam Basin. From the bottom to the top, the Shale Member includes three significant stages based on their average TOC values of 5.45% (Stage I), 9.90% (Stage II), and 1.10% (Stage III). Paleoclimate proxies including C-values and Rb/Sr ratios indicate that in Stage I the lake developed under warm and humid conditions, while in Stage II climate changed to hot and arid/semiarid conditions before returning to warm and humid climates in Stage III. Correlation analysis among proxies for palaeoclimate, terrestrial influx (Al2O3 and TiO2 contents), sedimentation rate ((La/Yb) N ratios), palaeosalinity (Sr/Ba ratios and B/Ga ratios), palaeoproductivity (P/Ti ratios and Sibio contents), redox conditions (Corg/P ratios), and TOC values revealed that palaeoclimate had little direct impact on OM accumulation, with palaeoenvironmental conditions the main controlling factor for OM accumulation. OM accumulation in Stage I was primarily controlled by redox conditions, followed by palaeoproductivity, terrigenous influx, and sedimentation rate. In Stage II, high palaeoproductivity and anoxic bottom water conditions controlled OM accumulation, resulting in the deposition of oil shales with abundant hydrocarbon potential. In Stage III, poor OM preservation related to oxic redox condition was the primary controlling factor for OM accumulation. We suggest that variations in lake palaeoenvironments induced by palaeoclimate change controlled OM accumulation and petroleum potential.

Original language	English
Article number	212581
Journal	Geoenergy Science and Engineering
Early online date	13 Dec 2023
DOIs	https://doi.org/10.1016/j.geoen.2023.212581
Publication status	E-pub ahead of print - 13 Dec 2023

Bibliographical note

Acknowledgements
The authors express their great thanks to the “No. 105 Exploration Team, Qinghai Bureau of Coal Geology” for support with borehole data. This research was supported by the National Natural Science Foundation of China (Grants 42302191, 42172196, 41772161, and 41472131) and the National Key Research and Development Program of China (Award 2021YFC2902000).

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Cite this

Zhou, K., Yang, M., Lu, J., Gao, R., Tong, L., Yin, L., Zhang, P., Wang, W., Liu, H., Shao, L., & Hilton, J. (2023). Palaeoclimatic influence on lake palaeoenvironment and organic matter accumulation in the Middle Jurassic Shimengou formation (Qaidam basin, NW China). Geoenergy Science and Engineering, Article 212581. Advance online publication. https://doi.org/10.1016/j.geoen.2023.212581

@article{9173ff75761243a38b21944cbb97ab39,

title = "Palaeoclimatic influence on lake palaeoenvironment and organic matter accumulation in the Middle Jurassic Shimengou formation (Qaidam basin, NW China)",

abstract = "The formation and accumulation of lacustrine organic-rich shales are strongly related to palaeoclimate and palaeoenvironmental conditions. Middle Jurassic organic-rich lacustrine shales in the Qaidam Basin, NW China, are important source rocks for unconventional oil and gas exploration, but factors controlling their organic matter (OM) abundance and preservation are unclear. To understand how palaeoclimate and palaeoenvironmental conditions influenced depositional processes and elucidate the factors controlling OM accumulation of lacustrine organic-rich shales, we investigated total organic carbon (TOC), mineral compositions, and element geochemistry the Shale Member of the Middle Jurassic (J2s2) Shimengou Formation from the Yuqia Coalfield in the Qaidam Basin. From the bottom to the top, the Shale Member includes three significant stages based on their average TOC values of 5.45% (Stage I), 9.90% (Stage II), and 1.10% (Stage III). Paleoclimate proxies including C-values and Rb/Sr ratios indicate that in Stage I the lake developed under warm and humid conditions, while in Stage II climate changed to hot and arid/semiarid conditions before returning to warm and humid climates in Stage III. Correlation analysis among proxies for palaeoclimate, terrestrial influx (Al2O3 and TiO2 contents), sedimentation rate ((La/Yb) N ratios), palaeosalinity (Sr/Ba ratios and B/Ga ratios), palaeoproductivity (P/Ti ratios and Sibio contents), redox conditions (Corg/P ratios), and TOC values revealed that palaeoclimate had little direct impact on OM accumulation, with palaeoenvironmental conditions the main controlling factor for OM accumulation. OM accumulation in Stage I was primarily controlled by redox conditions, followed by palaeoproductivity, terrigenous influx, and sedimentation rate. In Stage II, high palaeoproductivity and anoxic bottom water conditions controlled OM accumulation, resulting in the deposition of oil shales with abundant hydrocarbon potential. In Stage III, poor OM preservation related to oxic redox condition was the primary controlling factor for OM accumulation. We suggest that variations in lake palaeoenvironments induced by palaeoclimate change controlled OM accumulation and petroleum potential.",

author = "Kai Zhou and Minfang Yang and Jing Lu and Ran Gao and Lihong Tong and Lusheng Yin and Peixin Zhang and Wanqing Wang and Hongqing Liu and Longyi Shao and Jason Hilton",

note = "Acknowledgements The authors express their great thanks to the “No. 105 Exploration Team, Qinghai Bureau of Coal Geology” for support with borehole data. This research was supported by the National Natural Science Foundation of China (Grants 42302191, 42172196, 41772161, and 41472131) and the National Key Research and Development Program of China (Award 2021YFC2902000).",

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T1 - Palaeoclimatic influence on lake palaeoenvironment and organic matter accumulation in the Middle Jurassic Shimengou formation (Qaidam basin, NW China)

AU - Zhou, Kai

AU - Yang, Minfang

AU - Lu, Jing

AU - Gao, Ran

AU - Tong, Lihong

AU - Yin, Lusheng

AU - Zhang, Peixin

AU - Wang, Wanqing

AU - Liu, Hongqing

AU - Shao, Longyi

AU - Hilton, Jason

N1 - Acknowledgements The authors express their great thanks to the “No. 105 Exploration Team, Qinghai Bureau of Coal Geology” for support with borehole data. This research was supported by the National Natural Science Foundation of China (Grants 42302191, 42172196, 41772161, and 41472131) and the National Key Research and Development Program of China (Award 2021YFC2902000).

PY - 2023/12/13

Y1 - 2023/12/13

N2 - The formation and accumulation of lacustrine organic-rich shales are strongly related to palaeoclimate and palaeoenvironmental conditions. Middle Jurassic organic-rich lacustrine shales in the Qaidam Basin, NW China, are important source rocks for unconventional oil and gas exploration, but factors controlling their organic matter (OM) abundance and preservation are unclear. To understand how palaeoclimate and palaeoenvironmental conditions influenced depositional processes and elucidate the factors controlling OM accumulation of lacustrine organic-rich shales, we investigated total organic carbon (TOC), mineral compositions, and element geochemistry the Shale Member of the Middle Jurassic (J2s2) Shimengou Formation from the Yuqia Coalfield in the Qaidam Basin. From the bottom to the top, the Shale Member includes three significant stages based on their average TOC values of 5.45% (Stage I), 9.90% (Stage II), and 1.10% (Stage III). Paleoclimate proxies including C-values and Rb/Sr ratios indicate that in Stage I the lake developed under warm and humid conditions, while in Stage II climate changed to hot and arid/semiarid conditions before returning to warm and humid climates in Stage III. Correlation analysis among proxies for palaeoclimate, terrestrial influx (Al2O3 and TiO2 contents), sedimentation rate ((La/Yb) N ratios), palaeosalinity (Sr/Ba ratios and B/Ga ratios), palaeoproductivity (P/Ti ratios and Sibio contents), redox conditions (Corg/P ratios), and TOC values revealed that palaeoclimate had little direct impact on OM accumulation, with palaeoenvironmental conditions the main controlling factor for OM accumulation. OM accumulation in Stage I was primarily controlled by redox conditions, followed by palaeoproductivity, terrigenous influx, and sedimentation rate. In Stage II, high palaeoproductivity and anoxic bottom water conditions controlled OM accumulation, resulting in the deposition of oil shales with abundant hydrocarbon potential. In Stage III, poor OM preservation related to oxic redox condition was the primary controlling factor for OM accumulation. We suggest that variations in lake palaeoenvironments induced by palaeoclimate change controlled OM accumulation and petroleum potential.

AB - The formation and accumulation of lacustrine organic-rich shales are strongly related to palaeoclimate and palaeoenvironmental conditions. Middle Jurassic organic-rich lacustrine shales in the Qaidam Basin, NW China, are important source rocks for unconventional oil and gas exploration, but factors controlling their organic matter (OM) abundance and preservation are unclear. To understand how palaeoclimate and palaeoenvironmental conditions influenced depositional processes and elucidate the factors controlling OM accumulation of lacustrine organic-rich shales, we investigated total organic carbon (TOC), mineral compositions, and element geochemistry the Shale Member of the Middle Jurassic (J2s2) Shimengou Formation from the Yuqia Coalfield in the Qaidam Basin. From the bottom to the top, the Shale Member includes three significant stages based on their average TOC values of 5.45% (Stage I), 9.90% (Stage II), and 1.10% (Stage III). Paleoclimate proxies including C-values and Rb/Sr ratios indicate that in Stage I the lake developed under warm and humid conditions, while in Stage II climate changed to hot and arid/semiarid conditions before returning to warm and humid climates in Stage III. Correlation analysis among proxies for palaeoclimate, terrestrial influx (Al2O3 and TiO2 contents), sedimentation rate ((La/Yb) N ratios), palaeosalinity (Sr/Ba ratios and B/Ga ratios), palaeoproductivity (P/Ti ratios and Sibio contents), redox conditions (Corg/P ratios), and TOC values revealed that palaeoclimate had little direct impact on OM accumulation, with palaeoenvironmental conditions the main controlling factor for OM accumulation. OM accumulation in Stage I was primarily controlled by redox conditions, followed by palaeoproductivity, terrigenous influx, and sedimentation rate. In Stage II, high palaeoproductivity and anoxic bottom water conditions controlled OM accumulation, resulting in the deposition of oil shales with abundant hydrocarbon potential. In Stage III, poor OM preservation related to oxic redox condition was the primary controlling factor for OM accumulation. We suggest that variations in lake palaeoenvironments induced by palaeoclimate change controlled OM accumulation and petroleum potential.

U2 - 10.1016/j.geoen.2023.212581

DO - 10.1016/j.geoen.2023.212581

M3 - Article

JO - Geoenergy Science and Engineering

JF - Geoenergy Science and Engineering

M1 - 212581

ER -

Palaeoclimatic influence on lake palaeoenvironment and organic matter accumulation in the Middle Jurassic Shimengou formation (Qaidam basin, NW China)

Abstract

Bibliographical note

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