Paleoenvironmental evolution and organic matter accumulation in an oxygen-enriched lacustrine basin: A case study from the Laizhou Bay Sag, southern Bohai Sea (China)

Liang, Hongda; Xu, Guoce; Xu, Fanghao; Yu, Qilin; Liang, Jiaju; Wang, Deying

doi:10.1016/j.coal.2019.103318

Cited by 12 publications

(9 citation statements)

References 95 publications

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“…Unlike typical positive correlations between the primary productivity index (e.g., P/Ti) and TOC contents in most studies [17,75], TOC contents in the present study display a negative relationship with the P/Ti ratio (r = −0:70; Figure 14(d)). This result may suggest that the preservation conditions instead of primary productivity are much more important for the enrichment of OM and, also, reflect that the primary OM inevitably experienced some degree of postdepositional oxidation.…”

Section: Geofluidscontrasting

confidence: 96%

“…Organic-rich mudstones in lacustrine basins can be regarded as favorable hydrocarbon source rocks or direct unconventional petroleum resources (e.g., shale oil and shale gas) [14,15]; however, their formation processes are much more complicated than those in marine basins, since terrigenous influx and paleoclimate can exert a substantial influence on the evolution of restricted lacustrine basins [16,17]. Fortunately, continuous geochemical data of lacustrine sediments are used to reconstruct the depositional paleoenvironments at that time, which contributes to a better understanding of OM enrichment in lacustrine basins [9,12,[18][19][20].…”

Section: Introductionmentioning

confidence: 99%

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Organic-Inorganic Geochemical Characteristics of the Upper Permian Pusige Formation in a High-Saline Lake Basin, Tarim Basin: Implications for Provenance, Paleoenvironments, and Organic Matter Enrichment

Wang

Zhu

et al. 2021

Geofluids

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The third member (M3) of the Upper Permian Pusige Formation is a prominent organic-rich lacustrine mudstone sequence within the Yecheng-Hetian Sag, Tarim Basin, hosting major petroleum resources. However, its depositional history and organic matter (OM) enrichment mechanism have received little attention. Therefore, various organic and inorganic geochemical analyses were performed on thirty-four core samples from the Well DW1, to elucidate their depositional paleoenvironments, provenance, and tectonic setting, as well as the controlling factors of OM enrichment. Results showed that the M3 mudstones are classified as poor- to fair-quality hydrocarbon source rocks with mature type II-III kerogen, considering their low organic geochemical parameters. Paleosalinity indexes (e.g., Beq, Sr/Ba, and B/Ga) indicated the typical high-saline lacustrine water body, in which redox state was the oxic-dysoxic as suggested by multiple indicators. Many paleoclimate and weathering proxies suggest a dominant semiarid condition and low weathering degree in the Yecheng-Hetian Sag, which led to that weathered felsic rocks from the West Kunlun Orogen to the southwest of basin were quickly transported into the lake basin. Detrital materials carrying nutrient elements finally promoted the development of relatively high paleoproductivity indicated by fairly high P/Ti and Ba/Al ratios. The negative relationship between P/Ti and total organic carbon (TOC) indicates that paleoproductivity was not the main controlling factor. The correlations among TOC and P/Ti and other multiple proxies suggest that the OM enrichment can be interpreted as both the “preservation model” and “dilution model.” Although the water body was relatively oxygen-riched, high sedimentation rate could largely shorten the exposure time of OM with oxygen, thus decreased the decomposition of OM. In particular, the high-saline, stratified lake water may also restrain the degradation of OM. Furthermore, detrital dilution exerted a potential effect on TOC abundances. On the basis of the above results, a developing model was established to decipher the formation mechanism of OM in these M3 mudstones.

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Section: Geofluidscontrasting

confidence: 96%

Section: Introductionmentioning

confidence: 99%

Organic-Inorganic Geochemical Characteristics of the Upper Permian Pusige Formation in a High-Saline Lake Basin, Tarim Basin: Implications for Provenance, Paleoenvironments, and Organic Matter Enrichment

Wang

Zhu

et al. 2021

Geofluids

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“…Previous studies − have found that the warm and humid paleoclimate environment is conducive to the survival and reproduction of aquatic organisms and terrestrial higher organisms, and it will also cause the water body to deepen and form a reducing environment, which is conducive to the preservation of organic matter. On the contrary, the arid paleoclimate is not conducive to the survival and reproduction of aquatic organisms, which leads to the decline of organic matter abundance.…”

Section: Discussionmentioning

confidence: 99%

Geochemistry and Organic Petrology of Middle Permian Source Rocks in Taibei Sag, Turpan-Hami Basin, China: Implication for Organic Matter Enrichment

et al. 2021

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The Taodonggou group of Middle Permian is an important source rock in Taibei sag of Turpan-Hami basin. Due to its deep burial, drilling has only been revealed in recent years. Based on organic petrology and organic geochemistry experiments, this paper studies the organic petrology, organic geochemistry, sedimentary environment, and hydrocarbon generation potential of source rocks in Taibei sag, Turpan-Hami basin, and reveals the influence of the sedimentary environment on the organic matter abundance of source rocks. The results are as follows: (1) The organic matter of the Middle Permian source rocks in Taibei sag of Turpan-Hami basin is mainly sapropelite and exinite. The vitrinite is mainly vitrodetrinite, and the exinite is mainly lamalginiite. (2) The total organic carbon content value is 0.55–6.08 wt %, and the average value is 2.58 wt %. The PG value ranges from 0.78 mg HC/g to 30.86 mg HC/g, and the average value is 4.88 mg HC/g. Chloroform asphalt “A” is 0.046–0.8767 wt %, and the average value is 0.285 wt %. The types of organic matter are mainly III and II–III, and the R o value is 0.628–1.49 wt % (average = 0.988 wt %). The T max distribution is 329–465 °C. The average temperature is 434.7 °C, which is in the mature stage (oil window stage). The Middle Permian source rocks are mainly very good to excellent source rocks with a good hydrocarbon generation potential. (3) The source rocks are deposited in a semihumid and semiarid climate. Organic matter is input as a mixed source. The early and late stages is dominated by terrestrial higher plants. The middle stage is dominated by lower aquatic organisms, and the sedimentary environment consists of weak reduction and weak oxidation environments. (4) In the study area, the abundance of organic matter has a weak negative correlation with CPI and a positive correlation with Pr/Ph and ∑C21–/∑C22+. Under the coaction of paleoclimate, organic matter input, and redox environment, the enrichment model of organic matter with high productivity and weak oxidation environment characteristics can also form excellent source rocks. This study is of great significance and provides theoretical guidance for the exploration of deep oil and gas resources.

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“…Under reducing environments, with free HS − , Mo is converted to particle reactive thiomolybdates (Algeo and Tribovillard, 2009), and U is mainly carried out in the form of absorption by the sediment-water interface in a reducing environment. This study on U and Mo uses ‗enrichment factors' (EF), where X EF = [(X sample /Al sample )/(X PAAS /Al PAAS )], and X and Al stand for the weight concentrations of elements X and Al, respectively (Algeo and Tribovillard, 2009;Liang et al, 2020), and additionally, uses PAAS for normalization (Taylor and McLennan, 1985). Furthermore, the patterns of U-Mo covariation were established to identify the reducing degree of bottom water and determine the redox conditions (Tribovillard et al, 2012;Liang et al, 2020;Li et al, 2022).…”

Section: Redox Conditionsmentioning

confidence: 99%

“…This study on U and Mo uses ‗enrichment factors' (EF), where X EF = [(X sample /Al sample )/(X PAAS /Al PAAS )], and X and Al stand for the weight concentrations of elements X and Al, respectively (Algeo and Tribovillard, 2009;Liang et al, 2020), and additionally, uses PAAS for normalization (Taylor and McLennan, 1985). Furthermore, the patterns of U-Mo covariation were established to identify the reducing degree of bottom water and determine the redox conditions (Tribovillard et al, 2012;Liang et al, 2020;Li et al, 2022). However, this method was first proposed in the reconstruction of marine systems, and the U-Mo covariation of lacustrine systems has not yet been proven; several studies suggested that the aqueous concentrations of U and Mo in lakes are lower than those in marine systems (Chappaz et al, 2010;Smedley and Kinniburgh, 2017).…”

Section: Redox Conditionsmentioning

confidence: 99%

Paleoenvironmental Characteristics of Paleogene Lacustrine Source Rocks in the Western Bozhong Sag, Bohai Bay Basin, China: Evidence from Biomarkers, Major and Trace Elements

WANG,

LIU,

SONG

et al. 2024

Acta Geologica Sinica (Eng)

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The organic matter (OM) enrichment mechanisms and depositional environment characteristics of lacustrine source rocks in western Bozhong Sag, Bohai Bay Basin (BBB) remain controversial. To address these issues, based on Rock‐Eval pyrolysis, kerogen macerals, H/C and O/C ratios, GC‐MS, major and trace elements, the Dongying Mbr 3 (E3d3), the Shahejie Mbrs 1 and 2 (E2s1+2), and the Shahejie Mbr 3 (E2s3) source rocks in the western Bozhong Sag were studied. The above methods were used to reveal their geochemical properties, OM origins and depositional environments. The results indicate that the E2s1+2 and E2s3 are excellent source rocks, and the E3d3 of the second good quality. E3d3 source rocks were formed under a warm and humid climate, mainly belong to fluvial/delta facies, the E3d3 sediments have formed under weakly oxidizing and freshwater conditions. Comparatively, the depositional environments of E2s1+2 source rocks were arid and cold climate, representing saline or freshwater lacustrine facies, and the sediments of E2s1+2 belong to anoxic or suboxic settings with large evaporation and salinity. During the period of E2s3, the climate became warm and humid, indicating the freshwater lacustrine facies, and E2s3 was characterized by freshwater and abundant algae. Moreover, compared with other intervals, the OM origin of E3d3 source rocks has noticeable terrestrial input. The OM origin of the E2s1+2 and E2s3 are mainly plankton and bacteria. Tectonic subsidence and climate change have affected the changes of the depositional environment in the western Bozhong Sag, thus controlling the source rocks distribution, the geochemical characteristics in the three intervals of lacustrine source rocks have distinct differences. Overall, it is effective to evaluate the paleoenvironmental characteristics of source rocks by biomarkers, major and trace elements. The established models may have positive implications for research of lacustrine source rocks in offshore areas with few drillings.

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Paleoenvironmental evolution and organic matter accumulation in an oxygen-enriched lacustrine basin: A case study from the Laizhou Bay Sag, southern Bohai Sea (China)

Cited by 12 publications

References 95 publications

Organic-Inorganic Geochemical Characteristics of the Upper Permian Pusige Formation in a High-Saline Lake Basin, Tarim Basin: Implications for Provenance, Paleoenvironments, and Organic Matter Enrichment

Organic-Inorganic Geochemical Characteristics of the Upper Permian Pusige Formation in a High-Saline Lake Basin, Tarim Basin: Implications for Provenance, Paleoenvironments, and Organic Matter Enrichment

Geochemistry and Organic Petrology of Middle Permian Source Rocks in Taibei Sag, Turpan-Hami Basin, China: Implication for Organic Matter Enrichment

Paleoenvironmental Characteristics of Paleogene Lacustrine Source Rocks in the Western Bozhong Sag, Bohai Bay Basin, China: Evidence from Biomarkers, Major and Trace Elements

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