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 two-phase source rocks deposited during the Lower Cretaceous in the Persian Gulf Basin play a pivotal role in the regional hydrocarbon system. However, previous studies have lacked a macroscopic perspective constrained by the Tethyan Ocean context, which has limited a deeper understanding of their developmental patterns and hydrocarbon control mechanisms. To address this issue, this study aims to clarify the spatiotemporal evolution of the two-phase source rocks and their hydrocarbon control effects, with a particular emphasis on the critical impact of terrestrial input on the quality improvement of source rocks. Unlike previous studies that relied on a single research method, this study employed a comprehensive approach, including time series analysis, sequence stratigraphy, lithofacies, well logging, well correlation, seismic data, and geochemical analysis, to systematically compare and analyze the depositional periods, distribution, and characteristics of the two-phase source rocks under different sedimentary facies in the region. The goal was to reveal the intrinsic relationship between the Neo-Tethyan Ocean context and regional sedimentary responses. The results indicate the following: (1) the late Tithonian–Berriasian and Aptian–Albian source rocks in the Northern Persian Gulf were deposited during periods of extensive marine transgression, closely aligning with the global Weissert and OAE1d anoxic events, reflecting the profound impact of global environmental changes on regional sedimentary processes; (2) in the early stages of the Neo-Tethyan Ocean, controlled by residual topography, the Late Tithonian–Berriasian source rocks exhibited a shelf–intrashelf basin facies association, with the intrashelf basin showing higher TOC, lower HI, and higher Ro values compared to the deep shelf facies, indicating more favorable conditions for organic matter enrichment; (3) with the opening and deepening of the Neo-Tethyan Ocean, the Aptian–Albian source rocks at the end of the Lower Cretaceous transitioned to a shelf–basin facies association, with the basin facies showing superior organic matter characteristics compared to the shelf facies; (4) the organic matter content, type, and thermal maturity of the two-phase source rocks are primarily controlled by sedimentary facies and terrestrial input, with the Aptian–Albian source rocks in areas with terrestrial input showing significantly better quality than those without, confirming the decisive role of terrestrial input in improving source rock quality. In summary, this study not only reveals the differences in the depositional environments and hydrocarbon control mechanisms of the two-phase source rocks, but also highlights the core role of terrestrial input in enhancing source rock quality. The findings provide a basis for facies selection in deep natural gas exploration in the Zagros Belt and shale oil exploration in the western Rub’ al-Khali Basin, offering systematic theoretical guidance and practical insights for hydrocarbon exploration in the Persian Gulf and broader tectonic domains.

Shallow-water deltas are a subject of sedimentary research and represent a significant target for oil and gas exploration. The Yanchang Formation of the Triassic in the Ordos Basin comprises numerous shallow-water delta blocks. This paper addresses the core issues pertaining to the sedimentary facies, sedimentary characteristics and sand body distribution of the Chang 9 oil layer formation of the Upper Triassic in the Ordos Basin. Guided by the relevant theories and methods of contemporary sedimentology and sedimentary geology, the reservoir characteristics are described and studied in detail through ordinary thin sections, cast thin sections, graphical representations of particle size and scanning electron microscopy experiments. The experimental results indicate that the porosity in the study area ranges from 3% to 12% and that the permeability is between 0 and 1.5 × 10⁻³ μm², which is consistent with classification as an ultra-low-porosity and ultra-low-permeability reservoir. The Chang 9 sandstone is composed of feldspar sandstone and lithic feldspar sandstone. The average content of quartz is low, at less than 31%, while the average content of feldspar is high, at more than 34%. The average content of rock debris is between 10% and 20%. Therefore, the compositional maturity of the Chang 9 sand body is generally low. The particle size distribution exhibits a positive deviation, indicating that the sediments in the sand body are primarily coarse-grained components. The kurtosis of the particle size–frequency curve is observed to vary from flat to very sharp. The Chang 91 lake is classified as a shore shallow lake with basin subsidence and lake transgression. The Chang 9 period saw the development of the Chang 91 sedimentary facies into a semi-deep lake–deep lake environment. The vertical structural style of the Chang 9 oil layer formation in the basin can be roughly summarized into three basic structural types: the sedimentary structures observed in the area include box-shaped upward thinning, bell-shaped upward thinning and funnel-shaped upward thickening. The delta front area in Chang 9 is notable for its size and the prevalence of underwater distributary channel microfacies. The sand body distribution is stable, with sand layer thicknesses ranging from 15 to 30 m. The evaluation and summary of the sedimentary characteristics of the Chang 9 oil layer formation provide a geological basis for future exploration and development in the study area.

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.

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.

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.