Discussion on the applicability of Th/U ratio for evaluating the paleoredox conditions of lacustrine basins

Cao, Lei; Zhang, Zhihuan; Zhao, Junping; Jin, Xiao; Li, Hui; Li, Jiayang; Xiaodi, Wei

doi:10.1016/j.coal.2021.103868

Cited by 16 publications

(19 citation statements)

References 63 publications

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“…Thorium is generally present in seawater as Th(IV) in seawater and displays little response to changing redox conditions. The Th/U ratio has a long history of use as a redox proxy (Wignall and Twitchett, 1996;Algeo and Maynard, 2004;Cao et al, 2021). Generally, Th/U ratios ranging from 0 to 2 imply anoxic conditions, whereas ratios ranging from 2 to 7 indicate oxic conditions (Yao et al, 2014b).…”

Section: Redox Proxies and Changes Of Redox Conditionsmentioning

confidence: 99%

“…Yet only eight samples (SG8-16, SG8-27, SG8-28, SG8-29, SG8-33, SG8-34, SG8-35, and YT8-27) of both sections exhibit higher Th/U ratios that ranging from 2.007 to 3.909, are consistent with oxic or suboxic deposits. In contrast, Th/U ratios of remaining samples range from 0.003 to 1.962 (average = 0.671) suggesting that each section was primarily deposited under anoxic conditions (Figure 10; Cao et al, 2021).…”

Section: Redox Proxies and Changes Of Redox Conditionsmentioning

confidence: 99%

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Reconstruction of the paleo-marine environment during the Ediacaran-Cambrian transition: new insights from geochemical proxies, northern Tarim Platform, Northwest China

Fan,

Zhu

et al. 2024

Front. Earth Sci.

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The Cambrian Terreneuvian Yuertusi Formation of the Tarim Basin, regarded as a potential hydrocarbon source rock (TOCmax = 29.8 wt%), preserves the record of the Ediacaran to Cambrian Series 2 transition. This study presents a high-resolution multi-proxy investigation of the Sugaitebulake and Yutixi sections of the NW Tarim Basin. Evidence of hydrothermal activity and euxinic conditions in the earliest Cambrian has been delineated by samples from the lower part of the Yuertusi Formation group A, featured by weakly positive Ce anomalies (Ce/Ce*avg. = 0.46), extremely positive Eu anomalies (Eu/Eu*avg. = 26.39), Y/Ho ratios (Y/Hoavg. = 40.48) and several barite layers. Mo and U covariation suggests that the Yuertusi Formation group A and Xiaoerbulake Formation were deposited under sulfidic conditions, whereas the Ediacaran Qigebulake Formation, and Yuertusi Formation groups B and C and D accumulated under suboxic to anoxic conditions. The basin has been weakly restricted and characterized by elevated productivity (Ba-excessavg. = 6,410.42 ppm) during Terreneuvian time. Suboxic conditions in late Ediacaran time (Qigebulake Formation) became euxinic conditions in association with increased sea level and productivity sustained by hydrothermal activity and upwelling, which have been preserved in the organic-rich lower part of the Yuertusi Formation. Suboxic conditions were reestablished during the Cambrian Terreneuvian time as reflected in the geochemistry of the upper part of the Yuertusi Formation. Euxinic conditions were once again established early in Cambrian Series 2 Xiaoerbulake Formation. Euxinic conditions were coincident with transgressions of the South Tianshan Ocean during that interval. The accumulation and preservation of organic matter of the Early Cambrian northern Tarim Platform reflect the interaction of hydrothermal activity, coastal upwelling, and sea level change.

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Section: Redox Proxies and Changes Of Redox Conditionsmentioning

confidence: 99%

Section: Redox Proxies and Changes Of Redox Conditionsmentioning

confidence: 99%

Reconstruction of the paleo-marine environment during the Ediacaran-Cambrian transition: new insights from geochemical proxies, northern Tarim Platform, Northwest China

Fan,

Zhu

et al. 2024

Front. Earth Sci.

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“…In the light of U/Th, Taodonggou Group mudstone were deposited in an oxic environment, and according to V/Cr and V/(V+Ni), Taodong Group mudstone were deposited in a dyoxic environment. This is because U/Th cannot accurately identify the redox environment of the sediments under highly weathered conditions (Cao et al, 2021), so V/Cr and V/(V+Ni) were used in this study to identify the redox environment of Taodonggou Group mudstone. The cross plot of V/Cr and V/(V+Ni) shows (Fig.…”

Section: Location Of Parent Rockmentioning

confidence: 99%

Mineralogical and elemental geochemical characteristics of Taodonggou Group in Taibei Sag , Turpan-Hami Basin: Implication for Source sink system and evolution history of lake basin

Miao

Guo

Wang

et al. 2023

Preprint

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Abstract. The Middle Permian is an important basin-forming period in the Turpan-Hami Basin. Based on mineral characteristics and elemental geochemistry of the Taodonggou Group mudstone we analyze the parent rock type, source area location, sedimentary environment and source area tectonic background for this mudstone. On this basis we are able to reconstruct the source-sink system and lake basin evolution of the Taodonggou Group. We find the following: (1) Taodonggou Group mudstone minerals are mainly clay and quartz, and can be classified into four petrographic types according to mineral fraction. (2) The Taodonggou Group mudstone was deposited in a warm, humid and hot paleoclimate, with strong weathering. The parent rocks of the Taodonggou Group mudstone are two types of felsic volcanic rocks and andesites, with weak sedimentary sorting and recycling and with well-preserved source information. (3) The Taodonggou Group mudstone were deposited in dyoxic freshwater-brackish water in intermediate-depth or deep lakes with stable inputs of terrigenous debris but at slower deposition rates. Deposition of the middle of Taodonggou Group was influenced by hydrothermal activity; the tectonic setting of the Taodonggou Group source area was a continental island arc and an oceanic island arc. (4) The evolution of the Middle Permian Lake basin in the Turpan-Hami Basin can be divided into three stages: In the early part of the deposition of Taodonggou Group the depocenter was in the Bogda area. At this time the area that became Mt Bogda was not exposed and a succession of high-quality type-III source rocks was widely deposited in the basin. In the middle of the deposition of the Taodonggou Group the depocenter gradually migrated to the Taibei Sag. At this time the Mt Bogda area underwent uplift, and, together with hydrothermal activity, a succession of type-II source rocks was widely deposited in the basin. In the late part of the Taodonggou Group, uplift of the Mt Bogda area ceased and the depocenter transferred entirely to the Taibei Sag.

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“…This complexity, as well as uncertainty, is largely rooted in the fact that the chemical composition of sediments is largely determined by a wide variety of factors including the initial weathering provenance composition, transport distance, as well as the processes of weathering, erosion, deposition, and burial diagenesis (Johnsson, 1993). All the time, some scholars tried to improve the reliability of these indicators via kinds of methods (Wei and Algeo, 2020;Cao et al, 2021), for instance, the proposal of the enrichment factor (EF) (Algeo and Maynard, 2004;Tribovillard et al, 2012). However, this cannot solve the above problems once and for all.…”

Section: Introductionmentioning

confidence: 99%

Formation conditions and enrichment mechanisms of the Jurassic lacustrine organic-rich shale in the East Fukang Sag, Junggar Basin, NW China: A reassessment based on organic geochemistry

et al. 2023

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Chemical composition of sediments is often used to evaluate paleoclimate condition, provenance, tectonic setting, depositional condition, and paleoproductivity. However, the validity of these proxies has long been questioned. The comprehensive use of organic and inorganic multi-indicators in combination when interpreting issues related to terrestrial shales should be advocated. The paleodepositional environment, origin of organic matter (OM) and factor controlling OM accumulation in the Early Jurassic Badaowan (J1b) and Sangonghe (J1s) as well as Middle Jurassic Xishanyao (J2x) lacustrine shales in the East Fukang Sag are reassessed by using organic geochemical characteristics of the OM. Some previous knowledge is updated, and some knowledge is further supported by more evidence. The typical clay-rich shale developed under a lacustrine sedimental environment, and the thermal maturity of these organic-rich shales has entered the oil window and formed economic hydrocarbon potential for the tight-oil and shale-oil reservoirs. The paleoclimate conditions of the study area were warm and humid from the Early to Middle Jurassic periods but were colder and drier after the Middle Jurassic period. The salinity of the water column ranged from freshwater to brackish conditions. The J2x Formation was deposited under oxic conditions, while J1b and J1s formations developed under suboxic and reducing environmental conditions. The J2x Formation OM mainly derived from higher plants was deposited in a terrestrial environment,while the OM of J1b and J1s formations was a mixed OM derived from higher plants and bacteria with little algae deposited under bay/estuary environments alternated with terrestrial environments. It is effective to reflect the paleoclimate by element index and judge the salinity by the updated element thresholds, but it is not effective to evaluate the paleoredox conditions by common elemental ratios and to evaluate the paleoproductivity by Ba in the study area.

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Discussion on the applicability of Th/U ratio for evaluating the paleoredox conditions of lacustrine basins

Cited by 16 publications

References 63 publications

Reconstruction of the paleo-marine environment during the Ediacaran-Cambrian transition: new insights from geochemical proxies, northern Tarim Platform, Northwest China

Reconstruction of the paleo-marine environment during the Ediacaran-Cambrian transition: new insights from geochemical proxies, northern Tarim Platform, Northwest China

Mineralogical and elemental geochemical characteristics of Taodonggou Group in Taibei Sag , Turpan-Hami Basin: Implication for Source sink system and evolution history of lake basin

Formation conditions and enrichment mechanisms of the Jurassic lacustrine organic-rich shale in the East Fukang Sag, Junggar Basin, NW China: A reassessment based on organic geochemistry

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