High-frequency redox variations of the Eocene cyclic lacustrine sediments in the Yingxi area, western Qaidam Basin, China

Jiang, Qicai; Ma, Yan; Shen, Yun; Rongtao, Guo; Gao, Xiangyun; Liu, Bo; Cui, Jun; Wu, Kunyu

doi:10.1016/j.jseaes.2018.11.025

Cited by 12 publications

(5 citation statements)

References 63 publications

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“…Therefore, the concentrations of Mn and Sr and the ratio of Mn/Sr were used to determine the degree of diagenetic alteration. In general, carbonates with Mn/Sr < 10 retained their original seawater geochemical conditions, especially for Mn/Sr < 2-3 [58,59]. In this study, the average Mn/Sr ratio of all the samples was 0.114 (far less than 2), which indicated that their geochemical data could represent the original redox conditions of depositional environments.…”

Section: Redox-sensitive Trace Elementsmentioning

confidence: 57%

Section: Redox-sensitive Trace Elementsmentioning

confidence: 99%

“…Th/U, V/V+Ni, and Ni/Co were used to determine palaeo-redox conditions [59][60][61][62]. Concretely speaking, Th/U ratios < 1.5 imply anoxic conditions, Th/U ratios ranging from 1.5 to 3 manifest dysoxic conditions, and Th/U ratios > 3 suggested oxic conditions [59][60][61]. Hatch and Leventhal [60] suggested V/(V + Ni) ratios > 0.84 for euxinic conditions, 0.54-0.82 for anoxic waters, and 0.46-0.60 for dysoxic conditions.…”

Section: Redox-sensitive Trace Elementsmentioning

confidence: 99%

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Sedimentary and Diagenetic Features and Their Impacts on Microbial Carbonate Reservoirs in the Fourth Member of the Middle Triassic Leikoupo Formation, Western Sichuan Basin, China

et al. 2020

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In recent years, the discovery of two gas fields in the fourth member of the Leikoupo Formation in the Western Sichuan Basin of SW China confirmed the exploration potential of microbial carbonates. The aim of the present study is to clarify the formation mechanism of the microbial reservoirs in the Leikoupo Formation. For this purpose, lithofacies, depositional environments, and diagenesis analyses were performed in samples collected from cores of 12 wells. The climate of study area was arid during Anisian time, and the water body was restricted. In such a climate, an evaporitic environment was developed, where ten types of lithofacies, dominated by microbial carbonates and gypsum rocks, were recognized. Thrombolites and stromatolites are the main high-quality reservoirs rock types in the fourth member of the Leikoupo Formation in the Western Sichuan Basin of SW China, which developed as microbial mounds, with reservoir space of microbial inter-clot pores, intra-clot pores, fenestral pores, inter-crystalline pores, and cracks. The microbial inter-clot pores are the main reservoir space, formed by trapping and binding of marls by benthic microbial communities. These pores were partially filled with evaporites because of the arid climate, which were subsequently dissolved (mainly gypsum) in the syn-depositional period, thus greatly improving the quality of reservoirs. Although some pores were occluded by multi-stage cements during the burial stage, major pores were well preserved own to the early dolomitization, rapid burial of the Leikoupo Formation, and early charging of hydrocarbon. The early dolomitization enhanced the anti-compaction ability of microbial carbonates during the burial stage. Rapid burial of the Leikoupo succession slowed down early cementation, and it also accelerated the maturation and expulsion process source rock to promote early charging of hydrocarbon in pores, which created a closed system, inhibiting strong burial cementation.

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Section: Redox-sensitive Trace Elementsmentioning

confidence: 57%

Section: Redox-sensitive Trace Elementsmentioning

confidence: 99%

Section: Redox-sensitive Trace Elementsmentioning

confidence: 99%

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Sedimentary and Diagenetic Features and Their Impacts on Microbial Carbonate Reservoirs in the Fourth Member of the Middle Triassic Leikoupo Formation, Western Sichuan Basin, China

et al. 2020

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“…In the study of mixed sediments from the Yingxi area of the Qaidam Basin, ref. [83] demonstrated that the high-frequency deposition sequences were largely influenced by lake level changes resulting from paleoclimate variations. The lithological and geochemical evidence presented in this study further confirms the highfrequency periodic variations in water properties and paleoclimate during the Eocene in the Qaidam Basin.…”

Section: Synthesized Paleoclimate-sedimentary Modelmentioning

confidence: 99%

“…The lithological and geochemical evidence presented in this study further confirms the highfrequency periodic variations in water properties and paleoclimate during the Eocene in the Qaidam Basin. Hence, building upon the variations in the lake level and corresponding paleowater properties in the Eocene western Qaidam Basin, and considering previous research on lacustrine mixed rocks in the Qaidam Basin [12,26,83], we established a synthesized paleoclimate-sedimentary model in lacustrine mixed rocks for three consecutive periods within a whole high-frequency cycle (Figure 11).…”

Section: Synthesized Paleoclimate-sedimentary Modelmentioning

confidence: 99%

High-Frequency Lacustrine Lithological and Geochemical Variations in the Eocene Qaidam Basin: Implications for Paleoenvironment Reconstruction

Wu,

Tan,

Liu

et al. 2024

Minerals

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Lacustrine sedimentary processes exhibit high sensitivity to paleoenvironmental changes, often manifesting as high-frequency sedimentary cycles that control the complex variations in sedimentary structure, mineral composition, and element distribution. However, the intricate co-variation mechanism among paleoclimate and paleowater properties at a high precision level (centimeter to meter scale) is still controversial. This study focuses on conducting a high-frequency cycle analysis of lacustrine mixed rocks from the Eocene Lower Ganchaigou Formation (LGCG) in the Qaidam Basin, employing petrology, mineralogy, organic geochemistry, and elemental geochemistry techniques. The lithological variation was characterized by the superposition of three lithofacies types from the bottom to the top with a single sequence: massive sandstone, laminated silty shale, and bedded calcareous dolostone. Geochemical data revealed cyclical variations in the paleoenvironment in the vertical profile, which conformed to the high-frequency lithofacies cycles. Based on the reconstruction of the lake level and paleowater properties, a synthesized paleoclimate–sedimentary model that comprised three consecutive periods within an individual sequence was established. From the bottom to the top of each cycle, the Eocene paleoenvironment varied from reduction and desalination to oxidation and salinization, which was controlled by a decline in the lake level resulting from a transformation of the paleoclimate from warm and humid to cold and arid. The variations in petrology and geochemistry observed in the Eocene Qaidam Basin play a crucial role in comprehending the sedimentary response to paleoenvironmental changes at high precision levels within lacustrine settings.

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Nonstationary analysis of water and sediment in the Jinsha River Basin based on GAMLSS model

Jin,

Zhong,

Liu

et al. 2023

Stoch Environ Res Risk Assess

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High-frequency redox variations of the Eocene cyclic lacustrine sediments in the Yingxi area, western Qaidam Basin, China

Cited by 12 publications

References 63 publications

Sedimentary and Diagenetic Features and Their Impacts on Microbial Carbonate Reservoirs in the Fourth Member of the Middle Triassic Leikoupo Formation, Western Sichuan Basin, China

Sedimentary and Diagenetic Features and Their Impacts on Microbial Carbonate Reservoirs in the Fourth Member of the Middle Triassic Leikoupo Formation, Western Sichuan Basin, China

High-Frequency Lacustrine Lithological and Geochemical Variations in the Eocene Qaidam Basin: Implications for Paleoenvironment Reconstruction

Nonstationary analysis of water and sediment in the Jinsha River Basin based on GAMLSS model

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