Terrestrial records of Early Cretaceous paleoclimate fluctuations in the Yin'e Basin, northern China: Evidence from sedimentology and palynomorphs in lacustrine sediments

Self Cite

The Bayingebi Formation in the northeast of the Yin'e Basin developed abundant oil shale resources. A better understanding of the formation mechanism of these oil shales is of great significance for reconstructing the palaeogeographic environment of the Early Cretaceous in Northwest China and exploring potential unconventional oil and gas resources. In this study, a large amount of drilling data was used to reconstruct the sedimentary sequence stratigraphic framework, and the plane distribution of sandstone bodies and sedimentary facies in different system tracts was recovered. The lower member of the Bayingebi Formation (K 1 b 1 ) is identified as a developing low-stand system tract. The upper member (K 1 b 2 ) contains three system tracts, including a transgressive system tract (TST), a high-stand system tract (HST), and a regressive system tract (RST). Thick oil shale developed in the HST and the terrigenous detrital supply of the lake mainly came from the south and southwest. Petrology and organic geochemistry are used here to characterize the oil shale and mudstone. The oil yield of oil shale is primarily distributed between 3.5 and 6.5 wt %, and it is mainly type I kerogen (including lamalginite and telalginite). The oil yield of mudstone is lower than 3.5 wt %, and it is mostly type II 1 kerogen (including sporinite and telalginite). According to the analysis of provenance and paleoclimate from element geochemical indicators, the parent rocks of the Bayingebi Formation oil shale and mudstone are mainly of Permian andesite, which represent the tectonic background of a continental island arc. During the transition from the TST to HST, the paleoclimate changed from cool-semidry to warm-semihumid, the paleotemperature increased about 10 °C, the lake level gradually increased, and the degree of chemical weathering gradually strengthened. The early Aptian continental paleoclimate change in the Yin'e Basin coincides with coeval rising global paleotemperature. This study provides a basis for the response of continental paleolakes to the oceanic anoxic event (OAE 1a) and provides a reference for the organic matter enrichment mechanism of the black shale of the Bayingebi Formation.

Section: Discussionsupporting

confidence: 93%

Section: Tectonic Background Of Parent Rockmentioning

confidence: 99%

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Lacustrine Oil Shale Formation of Lower Cretaceous Bayingebi Formation in the Northeast of the Yin’e Basin: Implications from Lake Evolution, Provenance, and Paleoclimate

Liu

Li³

et al. 2022

Self Cite

“…Obviously, marl is of both sedimentary and chemical origin, and its initial organic matter content is difficult to estimate, but identifying it is an effective means of indirectly determining the productivity of ancient lakes through nutrient elements. For example, P, Cu, Zn, and Ba, which are common essential elements in organisms, are widely used in the qualitative analysis of productivity and initial organic matter content in sediments. − The results reveal a significant positive correlation between the siderite content and P content in the samples (Figure d) but a significant negative correlation between each of Cu and Zn and FeO in the samples. Such contradictory results make it difficult to assess the contribution of the initial organic matter content in sediments to siderite formation.…”

Section: Discussionmentioning

confidence: 98%

Characteristics, Genesis, and Hydrocarbon Aspects of Lacustrine Siderite-Rich Marl (Early Jurassic): A Case Study in the Dachanggou Basin, Xinjiang, Northwest China

Bai

Wang

Liu

2023

Thinly bedded marls are widely developed in the oil shalebearing series of the Lower Jurassic Badaowan Formation in the Dachanggou Basin (Northwest China). In this study, the characteristics, genesis, and hydrocarbon prospects of marls in a lacustrine organic-rich shale series were analyzed via X-ray diffractometry, element geochemistry, carbon and oxygen isotope analysis, total organic carbon content analysis, rock pyrolysis, and sedimentary analysis. The results show that the main carbonate component of marl is siderite, which is mainly present in areas with lithologic changes at the top and bottom of organic shale, and that the development of a thick siderite-rich marl is closely related to the presence of the thick oil shale. The elemental indicators of the sedimentary environment show that the low initial organic matter abundance and low clastic input were conducive to the formation of siderite and that the water body in the marl development period provided an oxic−suboxic environment, although the formation of siderite was still disturbed by oxygen in the relatively reduced bottom sediments. The carbonate carbon isotopes in the marl are clearly positive, indicating that δ 13 C-rich carbonate provided by methanogens decomposing sedimentary organic matter contributed to the siderite formation. These siderite-rich marls formed in a relatively restricted environment; i.e., they were deposited close to a rich organic layer, with a sufficient methanogenic metabolite CO 2 content and a small amount of terrigenous clastic input. These factors reached an appropriate balance, thus forming a narrow zone (partial shallow lake and delta front facies). Although the hydrocarbon generation potential of the marl is low relative to that of other source rocks, the thin marl that is widespread in continental shallow-water organic-rich sedimentary systems can improve the fracturing ability of shale reservoirs, which is of far-reaching significance for the development of shale oil and gas in continental shallow-water sedimentary systems.

“…Organic-rich fine-grained sedimentary rocks are closely related to regional climate evolution and can even correspond to global climate events. − The thick coal deposits in the Fushun Basin provide a good opportunity for studying element enrichment, occurrence forms, and influencing factors in coal seams. Many researchers have conducted detailed studies on the source of organic matter, sedimentary environment, and extreme climate of coal seams in the Fushun Basin, providing a preliminary basis for this study. − However, only few studies have investigated element enrichment, occurrence forms, and sources of coal seams in the Fushun Basin.…”

Section: Introductionmentioning

confidence: 99%

Occurrence Patterns and Enrichment Influencing Factors of Trace Elements in Paleogene Coal in the Fushun Basin, China

Zhang

Wei

Zhang

et al. 2022

The occurrence forms of trace elements in coal are of great significance for the clean utilization, abnormal enrichment, and recovery of beneficial elements in coal. The Fushun Basin in Northeast China has thick coal deposits which provide a good opportunity for studying their geochemistry. This study aims to estimate the element enrichment of Paleogene coal seams and their influencing factors during deposition based on statistical and geochemical analyses. Compared with world hard coals, coals in the Fushun Basin feature enrichment of Ga and Sb (CC > 5), slight enrichment of V, Cr, Co, Ni, As, Rb, Zr, Nb, and Cd (2 < CC < 5), and depletion of B, Tl, Bl, and U (CC < 0.5). The CC values of the remaining elements (0.5 < CC < 2) are close to the average values for world hard coals. The main carriers of Ga, Co, Rb, Mo, As, Se, Pb, V, and Li are potassium, iron, and sulfate minerals and those of Cd, Cr, Ni, Sb, Th, Sn, U, Hf, Zr, Cs, Ta, and Nb are clay minerals. The CIA, Sr/Cu, Rb/Sr, and Ga/Rb values suggest that the studied coal seam formed under humid/warm climatic conditions. The coal seam is mainly derived from intermediate source rocks and sandstone or mudstone source rocks which were exposed to intensive chemical weathering and deposited in a freshwater setting. Additionally, paleoweathering, paleoclimate, detrital input, and provenance all contributed to the enrichment of geochemical elements in the studied Paleogene coal. The results of this study are preliminary, and the authors will continue to conduct mineralogical analysis.