Depositional environments of the organic-rich shales from the Lower Cretaceous Dalazi Formation in the Yanji and Luozigou Basins of Northeast China

doi:10.1016/j.marpetgeo.2025.107437

IVPP-IR

	Depositional environments of the organic-rich shales from the Lower Cretaceous Dalazi Formation in the Yanji and Luozigou Basins of Northeast China
	Zhao, Xiangdong 1,2; Wang, Wei 2; Liu, Hanlin 3; Hu, Yongliang 2; Zhao, Xianye 2,4; Song, Chenran 2; Guan, Chengguo 2; Zheng, Daran 2; Zhang, Haichun 2
	2025-09-01
发表期刊	MARINE AND PETROLEUM GEOLOGY
ISSN	0264-8172
卷号	179 页码:12
通讯作者	Wang, Wei(wwang@nigpas.ac.cn) ; Liu, Hanlin(LHLDMC@163.com)
摘要	The organic-rich shales from the Lower Cretaceous Dalazi Formation in northeastern China are well known for their rich terrestrial fossils and significant hydrocarbon potential. However, the exact depositional environments of these shales remain unclear. Here, integrated geochemical proxies, including iron speciation (Fe-HR/Fe-T, Fe-py/Fe-HR), pyrite sulfur isotopes (delta S-34(py)), and major- and trace-element enrichments were carried out on these organic-rich shales from the Zhixin section of the Yanji Basin and the Beigou section of the Luozigou Basin in Northeast China. This study aims to provide insights into the contemporaneous continental chemical weathering intensities accompanied with the lake redox conditions during the deposition of the Dalazi Formation shales. Low chemical index of alteration (CIA) values were detected in the shales, indicating low weathered continental environments during the depositional period of the shales. The reduced water availability under dry climate evidenced by plant fossils likely contributes to limiting the intensity of chemical weathering with low CIA values. All samples exhibit Fe-HR/Fe-T ratios >0.38 and Fe-py/Fe-HR ratios far below 0.7, displaying the water column characterized by anoxic ferruginous conditions with limited HS- availability during the shale deposition. The reconstruction of redox condition is consistent with the observations of the low pyrite contents, minimal well-formed framboidal pyrite crystals and covariation patterns of Mo-EF and U-EF in the shales. With low CIA values, the less continental input to the lake probably gives rise to the anoxic ferruginous deep-water conditions via limiting sulfate availability, which is consistently supported by high delta S-34(py) values (12.2 +/- 9.6 parts per thousand), low pyrite contents, and the remarkable negative correlation between the CIA and delta S-34(py) values. Considering the high content of organic matter up to 6.38 wt% and abundant fossil collections in the shales, this finding highlights the beneficial role of a sustained and stable anoxic ferruginous environment for preserving organic matter and carbonaceous fossils in the Dalazi Formation.
关键词	Ferruginous conditions The Dalazi Formation Iron speciation Organic-rich shales Cretaceous
DOI	10.1016/j.marpetgeo.2025.107437
关键词[WOS]	JILIN PROVINCE ; FERRUGINOUS CONDITIONS ; SEDIMENTARY-ROCKS ; OCEAN CHEMISTRY ; SULFUR ; MOLYBDENUM ; REDUCTION ; MATTER ; IRON ; PRESERVATION
收录类别	SCI
语种	英语
资助项目	Strategic Priority Research Program (B) of the Chinese Academy of Sciences[XDB0850000] ; National Natural Science Foundation of China[42402012] ; National Natural Science Foundation of China[42072036] ; National Natural Science Foundation of China[42288201] ; National Natural Science Foundation of China[41921002] ; National Natural Science Foundation of China[42130207]
项目资助者	Strategic Priority Research Program (B) of the Chinese Academy of Sciences ; National Natural Science Foundation of China
WOS研究方向	Geology
WOS类目	Geosciences, Multidisciplinary
WOS记录号	WOS:001487981700001
出版者	ELSEVIER SCI LTD
引用统计
文献类型	期刊论文
条目标识符	http://119.78.100.205/handle/311034/24662
专题	中国科学院古脊椎动物与古人类研究所
通讯作者	Wang, Wei; Liu, Hanlin
作者单位	1.Chinese Acad Sci, Inst Vertebrate Paleontol & Paleoanthropol, Key Lab Vertebrate Evolut & Human Origins, Beijing 100044, Peoples R China 2.Chinese Acad Sci, Nanjing Inst Geol & Paleontol, State Key Lab Palaeobiol & Stratig, Nanjing 210008, Peoples R China 3.PetroChina Res Inst Petr Explorat & Dev, Beijing 100083, Peoples R China 4.Vrije Univ Brussel, Archaeol Environm Changes & Geochem Grp, B-1050 Brussels, Belgium
推荐引用方式 GB/T 7714	Zhao, Xiangdong,Wang, Wei,Liu, Hanlin,et al. Depositional environments of the organic-rich shales from the Lower Cretaceous Dalazi Formation in the Yanji and Luozigou Basins of Northeast China[J]. MARINE AND PETROLEUM GEOLOGY,2025,179:12.
APA	Zhao, Xiangdong.,Wang, Wei.,Liu, Hanlin.,Hu, Yongliang.,Zhao, Xianye.,...&Zhang, Haichun.(2025).Depositional environments of the organic-rich shales from the Lower Cretaceous Dalazi Formation in the Yanji and Luozigou Basins of Northeast China.MARINE AND PETROLEUM GEOLOGY,179,12.
MLA	Zhao, Xiangdong,et al."Depositional environments of the organic-rich shales from the Lower Cretaceous Dalazi Formation in the Yanji and Luozigou Basins of Northeast China".MARINE AND PETROLEUM GEOLOGY 179(2025):12.