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Carbonate rocks exhibit significant heterogeneity as both a source rock and reservoir. Stylolite formation plays a crucial role in the enrichment of organic matter and the migration of geofluids within carbonate rocks. In order to study the enrichment mechanism of organic matter and the geofluid migration mode in the stylolites developed in carbonate rocks, stylolite-bearing core samples from the Dachigan structural belt in the eastern Sichuan Basin were collected. The stylolites and matrix were subjected to the total organic carbon (TOC) test and Rock-Eval pyrolysis, thin-section observation under fluorescent light, whole-rock X-ray diffraction, carbon and oxygen isotope analysis, and scanning electron microscopy. The organic matter occurring in the stylolites is mainly in the form of three types: soluble organic matter, pyrobitumen, and bitumen. This suggests that the organic matter within the stylolites mainly consists of secondary migrated organic matter. The stylolites also exhibit well-developed secondary dolomite and pyrite resulting from late-diagenetic recrystallization. These minerals contribute to the preservation of intercrystalline pore spaces and fractures, providing favorable conditions for oil and gas accumulation and migration. The strong cementation observed at the contact between the stylolites and matrix, along with the presence of secondary minerals nearby, may be attributed to the fractionation of light and heavy oil components during the migration of hydrocarbon fluids from the matrix to the stylolites. The thicknesses of the stylolites vary within the bulk, indicating severe diagenesis in thinner areas. Consequently, this leads to significant fractionation effects. The fractionation of crude oil components by stylolites poses challenges for the study of definitive oil–source correlations. To overcome these challenges, future research could investigate biomarker compounds to attempt oil–source correlations. Additionally, future efforts should take into consideration the spatial variation in the crude oil properties. Understanding the role of stylolites in organic matter enrichment and geofluid migration is crucial for optimizing exploration strategies in the Sichuan Basin, a region of growing importance in the energy industry. Moreover, our findings shed light on the complex interactions within stylolite-bearing rocks, which are not limited to this specific basin. These insights offer valuable contributions to the broader field of geology and reservoir characterization, enhancing our ability to predict and interpret similar geological formations globally. [ABSTRACT FROM AUTHOR]

In April 2023, a critically endangered plant species called Plantago fengdouensis was rediscovered on an island in the Yangtze River in Sichuan, China. This species is endemic to the Yangtze River Basin and was previously thought to be extinct in the wild due to the construction of the Three Gorges Dam. However, two previously unknown populations of the plant were found in January 2024 on two islands in the Yangtze River. Efforts are being made to protect these populations and conduct further surveys to locate any other wild populations. Seeds have been collected for ex situ conservation and genetic investigation, with the aim of potentially reintroducing the species. [Extracted from the article]

Nardostachys jatamans is an endemic herb in China, distributes mainly in Southeast Gansu, South Qinghai and West Sichuan of Qinghai-Tibet Plateau. In this study, the complete chloroplast genome (a typical quadripartite structure) sequence of N. jatamans was reported. The length of the DNA molecule was 155,268 bp with a large single-copy region (LSC: 87,263 bp), small single-copy region (SSC: 17,327 bp) and inverted repeats (IRa and IRb: 25,339 bp). The overall GC content was 38.56%. It has a total of 129 genes, containing 83 protein-coding genes, 38 tRNA genes, and eight rRNA genes. The phylogenetic analysis has shown that N. jatamans is sister to Valeriana offcinalis. The chloroplast genome provides the basis for development and utilization of N. jatamans in future. [ABSTRACT FROM AUTHOR]

In order to study the organic matter source in stylolite and its effect on hydrocarbon migration, carbonate rock core samples containing stylolites in the eastern Sichuan Basin were collected. The stylolite and matrix in the cores were analyzed by total organic carbon (TOC), Rock-Eval pyrolysis and gas chromatography-mass spectrometer (GC–MS) for the saturated fractions. The organic matter is more enriched in the stylolite than the matrix, and the stylolite have higher hydrocarbon expulsion efficiency than the matrix, which can be used as a supplement to the later generation of the source rock. The hydrocarbons formed by the matrix aggregated near the stylolites and cause the Hydrocarbon Index of the matrix which adjacent to the stylolites to become higher, this indicates that the stylolite is an important channel for hydrocarbon discharge of carbonate rocks. The ratios of close molecular biomarker in stylolite indicate that the deposition environment, biological origin and maturity of organic matter in the stylolites are consistent with the matrix, therefore, the organic matter in the stylolite should be inherited from the matrix, but the light to heavy molecular biomarker ratios of the stylolite indicate that component fractionation occurred when the hydrocarbons generated in the matrix migrated to the stylolite. Especially, a series of light to heavy molecule ratios of C 19 to C 23 tricyclic terpanes and C 14 to C 19 normal alkane of stylolite are lower than that of matrix, this indicates that the hydrocarbon fractionation in the course of hydrocarbon migration along the stylolite is more obvious than that in the matrix. • The organic-rich stylolite in low-abundance carbonate source rocks is an important supplement to the parent material for hydrocarbon generation. • The stylolite is important pathway for fluid migration in carbonate rocks. • The hydrocarbons in the matrix underwent a fractionation effect as they migrated from the matrix to the stylolite. • The hydrocarbon fractionation in the course of hydrocarbon migration along the stylolite is more obvious than that in the matrix. [ABSTRACT FROM AUTHOR]