This study has determined the period of sedimentation of the Lingshui Formation as the Oligocene (Rupelian-Chattian) through biostratigraphic data, including planktonic foraminifera zonation. The astronomical timescale framework for the Lingshui Formation was accurately constructed by integrating geophysical logging data and employing a multidisciplinary approach that includes time series analysis, cyclostratigraphy, astronomical dating, and Power Ratio Accumulation (PRA) methods. Sensitivity analysis of PRA has shown that natural gamma (GR) is the optimal paleoclimatic proxy, laying the foundation for subsequent analyses. The optimal sedimentation rate for the Lingshui Formation, determined by combining the coefficient of correlation (COCO) method with PRA analysis, is 5–5.4 cm/kyr. The duration of the Lingshui Formation was established at 5.02 Ma (28.52 Ma–23.5 Ma) based on time series analysis and astronomical tuning. The sediment noise model has revealed that the ~1.2 Myr obliquity modulation period has a significant impact on sea-level changes, further confirming the stratigraphic control of astronomical forcing on the sedimentation rate of the Lingshui Formation. This study establishes a high-precision astronomical timescale framework for the Lingshui Formation and provides a robust methodology, offering scientific basis for the research in astronomical chronostratigraphy and cycle stratigraphy, which has significant potential implications.

The Azigan Formation and the Lower Member of the Tahaqi Formation, dating to the Late Pennsylvanian, are pivotal exploration targets within the Tarim Basin. This region exhibits extensive siliciclastic-carbonate mixed sediments. However, the lack of high-resolution sequence stratigraphic frameworks significantly limits advanced petroleum geological research. Using principles of sequence stratigraphy and cyclostratigraphy and leveraging outcrop and thin section data alongside GR series analysis, this study systematically investigates the lithological, cyclic, and sequence stratigraphic characteristics of these formations. A total of 12 different lithofacies were identified, and 3 third-order sequences, 15 fourth-order sequences, and 16 long eccentricity cycles were delineated. A 1.2 Ma long slope signal was also identified. An astronomical timescale was established with 298.9 Ma as the anchor, defining the boundary between the upper and lower members of the Tahaqi Formation, revealing a link between long eccentricity cycles and the formation of fourth-order sequences. Moreover, the relationship between the 1.2 Ma long obliquity cycle and third-order sequences, as well as its role in driving sea-level changes in southwestern Tarim, is explored. The interplay between long obliquity and eccentricity cycles influenced the region’s mixed siliceous clastic and carbonate deposition. Warm and humid climatic conditions coupled with sea-level rise enhanced the input and transport of clastic materials, facilitating large-scale mixed sedimentation.

In this study, we elucidate the genesis and distribution patterns of Silurian hot shale hydrocarbon source rocks by utilizing a comparative analysis of the evolutionary characteristics of plate tectonic activity in the Paleo–Tethys Ocean and the sedimentary filling characteristics of key basins in North Africa, the Middle East, and South China. We propose an explanation for the sedimentary genesis of world-class Silurian hydrocarbon source rocks in the Paleozoic craton basin of the ancient Tethys tectonic domain. This is achieved by scrutinizing the plate tectonic activity and evolution of the ancient Tethys Ocean and combining these findings with the paleotectonic sedimentation background of North Africa, the Middle East, and South China. Additionally, we compare Silurian hydrocarbon source rocks from these regions. The deep-water stagnant environment of the land shelf favors the preservation of organic matter, thereby forming high-quality hydrocarbon source rocks. Conversely, the shallow-water body of the land shelf is more turbulent, thus resulting in the poorer preservation of organic matter and, consequently, lower-quality hydrocarbon source rocks.

Sub-sag 21 in the eastern Yangjiang Sag, Pearl River Mouth Basin, South China, contains a thick lacustrine source-rock interval within the lower Wenchang Formation and is a major exploration target on the northern margin of the South China Sea. However, the timing of deposition during the early to middle Eocene remains poorly constrained, and the applicability of quantitative palaeoclimate reconstruction methods in low-latitude lacustrine basins requires further evaluation. In this study, we analyzed mudstones from the lower Wenchang Formation in Well E1. Using cyclostratigraphic constraints, we applied AstroGeoFit to construct an astronomically tuned age model, and combined palynological coexistence analysis with geochemical weathering proxies and linear–regression calibration to quantitatively reconstruct and cross-validate mean annual temperature and mean annual precipitation. Within this time-calibrated framework, we further quantified organic-carbon burial to evaluate the relationship between palaeoclimate evolution and organic-matter enrichment. The AstroGeoFit results indicate that the top of the lower Wenchang Formation in Well E1 is constrained to 44.563 Ma, and that the studied succession spans 50.249–44.563 Ma. Palynological coexistence analysis identifies three palaeoclimate phases within this interval. Method evaluation shows that the temperature reconstruction based on major-element geochemistry agrees well with the pollen-based temperature record, whereas one precipitation reconstruction based on weathering proxies shows the most robust agreement and stability relative to the pollen-based precipitation record. Reconstructed mean annual temperature ranges from 10.77 to 22.20 °C, and reconstructed mean annual precipitation ranges from 1188.27 to 1871.89 mm. Correlation analyses on the tuned timescale show that precipitation is more strongly associated than temperature with organic-matter accumulation parameters, including total organic carbon and organic carbon accumulation rate, indicating that organic carbon burial in the eastern Yangjiang Sag lake basin was mainly controlled by hydrological forcing. During the Early Eocene Climatic Optimum, carbon burial in low-latitude lakes was, therefore, not a simple response to elevated temperature, but instead reflected the integrated effects of precipitation, runoff, stratification, material supply, transport, and preservation. The evolutionary sequence further suggests that early high productivity was diluted by rapid sedimentation, reducing total organic carbon; subsequent cooling, lake deepening, and strengthened stratification enhanced organic matter preservation; and finally, tectonic subsidence together with regional humidification promoted the development and long-term preservation of high-quality lacustrine source rocks.

The formation and spatial distribution of sedimentary systems in rift-lake basins are jointly controlled by multiple factors, including sediment supply rates from source areas, clastic sediment transport pathways, and basin geometry and intrabasinal structural configuration (e.g., accommodation zones and faults), which strongly influence the architecture of depositional systems and basin filling processes. The Wenliu Formation (Wenliu Member, Late Paleogene) of the Wenchang Group in the Enping 20/21 Depression of the Yangjiang East Sag, Pearl River Mouth Basin, developed a multi-source and multi-channel sand-transport system; however, the matching relationships and coupling mechanisms among different source areas, transport pathways, and depositional systems remain poorly understood. Based on three-dimensional seismic data, drilling, and well-log information, combined with heavy mineral assemblages and detrital zircon U–Pb age spectra, this study comprehensively investigates the source areas, paleochannel clastic sediment transport pathways, and depositional systems of the Wenliu Member, systematically establishing the source-to-sink (S2S) framework. The results indicate that sediments of the Wenliu Member were supplied from four main source areas, including the northwestern Yangchun Uplift, northeastern Enyang low uplift, and southwestern Yangjiang low uplift, with nine major paleochannel clastic sediment transport pathways identified. The different source zones show distinct variations in area, slope characteristics, and sediment supply modes, corresponding to differentiated paleochannel types and paleodrainage configurations. The study area overall exhibits a typical multi-channel convergence depositional pattern, dominated by braid-delta and fan-delta systems. The Enyang low-slope source zone generated the largest braid-delta deposits, whereas fault-transformed source zones produced fan-delta deposits adjacent to active faults and along basin-margin fault systems. Quantitative analysis further indicates that depositional-system scale is significantly correlated with source-area size, paleodrainage development, and paleochannel geometric parameters. Large depositional bodies are more likely to form when the source area exceeds ~60 km², the paleochannel width exceeds ~1.4 km, and the cross-sectional area exceeds ~10 km². Integrating the spatial relationships among source areas, transport pathways, and depositional systems, four source-to-sink subsystems are identified, which can be further classified into two typical depositional patterns: a long-source gentle-slope braid-delta pattern and a proximal-source rapid-accumulation fan-delta pattern. This study elucidates the coupling relationships among source areas, clastic sediment transport pathways, and depositional sinks in a multi-source rift-lake basin, providing a geological basis for predicting sedimentary systems and guiding hydrocarbon exploration in the study area.

This study focuses on the upper section of the Zhujiang Formation in the Enping Sag of the Zhujiangkou Basin in the South China Sea, investigating the mechanisms by which astronomical orbital cycles drive paleoclimate, sea-level fluctuations, and sedimentary development. In this study, a cyclic stratigraphic analysis was performed using natural gamma-ray logging data and geochemical proxies (Chemical Index of Alteration (CIA); Al₂O₃ content) in combination with depositional noise modeling (DYNOT Dynamic Orbital Tuning Model and ρ1 noise factor). High-resolution time series analysis revealed three key findings: (1) a 15.98–19.09 Ma astronomical timescale was established through the identification of Milankovitch cycles including 405 kyr eccentricity, 100 kyr eccentricity, 40 kyr obliquity, and 20 kyr precession; (2) sea-level changes exhibited 405 kyr eccentricity-driven cyclicity, with high-eccentricity phases corresponding to warm-humid climates and transgressive mudstone deposition, and low-eccentricity phases reflecting arid conditions and regressive sandstone development; and (3) orbital-scale precession modulation regulated sediment source-to-sink processes through climate–sea level coupling. This work provides a quantitative framework for predicting astronomical cycle-controlled reservoirs, offering critical insights for deepwater hydrocarbon exploration in the Zhujiangkou Basin.