An alkaline lake in the Late Paleozoic Ice Age (LPIA): A review and new insights into paleoenvironment and petroleum geology

Cao, Jian; Xia, Liuwen; Wang, Tingting; Zhi, Dongming; Tang, Yong; Li, Wenwen

doi:10.1016/j.earscirev.2020.103091

Cited by 160 publications

(128 citation statements)

References 55 publications

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“…The Fengcheng Fm (309–292 Ma) was deposited contemporaneously with the late Paleozoic Gondwanan glaciation (Soreghan et al., 2019). The Fengcheng strata contain minerals such as eitelite [Na 2 Mg 2 (CO 3 ) 3 ] and shortite [Na 2 Ca 2 (CO 3 ) 3 ], which are indicative of a warm climate, but lack natron [Na 2 CO 3 ·10H 2 O], which is indicative of a cold climate (Cao et al., 2020). Research shows that these minerals were mainly formed during the (syn)deposition with a few in penecontemporaneous stages, such that the diagenetic alterations seem to be negligible (Wang et al., 2020).…”

Section: Discussionmentioning

confidence: 99%

A new constraint on the antiquity of ancient haloalkaliphilic green algae that flourished in a ca. 300 Ma Paleozoic lake

et al. 2020

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It is established that green algae and land plants progressively colonized freshwater and terrestrial habitats throughout the Paleozoic Era, but little is known about the ecology of Paleozoic saline lakes. Here, we report lipid biomarker and petrographic evidence for the occurrence of a green alga as a major primary producer in a late Paleozoic alkaline lake (Fengcheng Formation; 309–292 Ma). A persistently saline and alkaline lacustrine setting is supported by mineralogical and lipid biomarker evidence alongside extremely enriched δ15Nbulk values (+16 to +24‰) for the lake depocenter. The prominence of C28 and C29 steroids, co‐occurring with abundant carotene‐derived accessory pigment markers in these ancient rocks, is suggestive of prolific primary production and elevated source inputs from haloalkaliphilic green algae. The high C28/C29‐sterane ratios (0.78–1.29) are significantly higher than the typical marine value reported for late Paleozoic rocks (<0.5) and thus are associated with certain groups of chlorophytes. Adaptation to such extreme lacustrine environments, aided by enhanced biosynthesis of certain cell membrane lipids, likely played an important role in the evolution and physiological development of ancient green algae.

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Section: Discussionmentioning

confidence: 99%

A new constraint on the antiquity of ancient haloalkaliphilic green algae that flourished in a ca. 300 Ma Paleozoic lake

et al. 2020

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“…Currently, lacustrine carbonate source rocks have also been noted during recent years (Liu et al 2019). For example, the carbonate source rocks might have act as important oil contributors in the lacustrine Mahu sag (Cao et al 2019). Although the study case in this study is for marine carbonate rocks, based on the principle and methods of mass balance, the identification of effective lacustrine carbonate rocks is also applicable.…”

Section: Methods Verificationmentioning

confidence: 99%

Method for identifying effective carbonate source rocks: a case study from Middle–Upper Ordovician in Tarim Basin, China

Chen

Pang

et al. 2020

Pet. Sci.

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Hydrocarbon expulsion occurs only when pore fluid pressure due to hydrocarbon generation in source rock exceeds the force against migration in the adjacent carrier beds. Taking the Middle–Upper Ordovician carbonate source rock of Tarim Basin in China as an example, this paper proposes a method that identifies effective carbonate source rock based on the principles of mass balance. Data from the Well YW2 indicate that the Middle Ordovician Yijianfang Formation contains effective carbonate source rocks with low present-day TOC. Geological and geochemical analysis suggests that the hydrocarbons in the carbonate interval are likely self-generated and retained. Regular steranes from GC–MS analysis of oil extracts in this interval display similar features to those of the crude oil samples in Tabei area, indicating that the crude oil probably was migrated from the effective source rocks. By applying to other wells in the basin, the identified effective carbonate source rocks and non-source rock carbonates can be effectively identified and consistent with the actual exploration results, validating the method. Considering the contribution from the identified effective source rocks with low present-day TOC (TOCpd) is considered, the long-standing puzzle between the proved 3P oil reserves and estimated resources in the basin can be reasonably explained.

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“…Several structural units occur in the Junggar Basin (Figure 1(a)), and the Mahu Sag is one of the largest depressions in the basin (Figure 1(a)) [54]. The slope of the Mahu Sag is the most favorable hydrocarbon accumulation area, where nearly one billion tons of oil have been discovered (Figure 1(b)).…”

Section: Geological Settingmentioning

confidence: 99%

Chemically Active Elements of Reservoir Quartz Cement Trace Hydrocarbon Migration in the Mahu Sag, Junggar Basin, NW China

et al. 2021

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Element exchange and enrichment during fluid-rock interactions are common, providing potentially novel proxies to trace hydrocarbon migration in addition to the traditional organic geochemistry tracers. However, the processes, mechanisms, and geological and geochemical fingerprints of these interactions are complex, hampering the applications of hydrocarbon migration tracers. To investigate such interactions, we conducted a petrological, mineralogical, and in situ and bulk geochemical study of authigenic quartz and whole-rock samples from the Mahu Sag, northwestern Junggar Basin, northwest China. We found that dissolution, clay and chlorite formation, and overgrowth occurred on quartz grains in hydrocarbon fluid migration pathways, suggestive of strong fluid-rock interactions. In situ quantitative elemental analysis of quartz grains revealed elemental enrichment (e.g., Mn, Fe, Al, Sr, and W) in quartz overgrowth rims compared with their cores, indicating that migration of hydrocarbon-bearing fluids in reservoirs may promote elemental exchange between fluids and minerals. Whole-rock geochemical analysis showed that decreasing contents of some elements may reflect the direction of hydrocarbon-bearing fluid migration and can be monitored with three geochemical proxies, which are the MnO contents and MnO/Zr and Y/Ho ratios. Our data provide new constraints on fluid-rock interactions in petroleum reservoirs and have implications for using inorganic geochemical methods to trace hydrocarbon migration.

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An alkaline lake in the Late Paleozoic Ice Age (LPIA): A review and new insights into paleoenvironment and petroleum geology

Cited by 160 publications

References 55 publications

A new constraint on the antiquity of ancient haloalkaliphilic green algae that flourished in a ca. 300 Ma Paleozoic lake

A new constraint on the antiquity of ancient haloalkaliphilic green algae that flourished in a ca. 300 Ma Paleozoic lake

Method for identifying effective carbonate source rocks: a case study from Middle–Upper Ordovician in Tarim Basin, China

Chemically Active Elements of Reservoir Quartz Cement Trace Hydrocarbon Migration in the Mahu Sag, Junggar Basin, NW China

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