Slope stability assessment is a critical concern in construction projects. This study explores the use of multivariate adaptive regression splines (MARS) to capture the intrinsic nonlinear and multidimensional relationship among the parameters that are associated with the evaluation of slope stability. A comparative study of machine learning solutions for slope stability assessment that relied on backpropagation neural network (BPNN) and MARS was conducted. One data set with actual slope collapse events was utilized for model development and to compare the performance of BPNN and MARS. Research results suggest that BPNN and MARS models can model the relationship between the safety factor and the slope parameters. Also, the MARS model has the advantages of computational efficiency and easy interpretation.

The Permian Chert Event is of great significance to understanding the geological evolution of the entire Permian; however, the origin of widespread chert formation is debated. We report new geochemical data from deep-marine siliceous rocks of the upper Permian Da-long Formation, Lower Yangtze region, southeastern China. Their geochemical results show that these thin-bedded siliceous rocks have a clear biologic origin, with rare to no evidence of hydrothermal influence. The values of Al/(Al + Fe + Mn) and Eu/Eu* are 0.60–0.84 (mean = 0.72) and 0.45–1.08 (mean = 0.77), respectively, and Mn/Ti ratios are relatively low (mean = 0.72). The correlations of La_N/Ce_N, La_N/Yb_N, and Fe₂O₃/TiO₂ with Al₂O₃/(Al₂O₃ + Fe₂O₃), along with the Ce anomaly, indicate that the Da-long siliceous rocks were deposited at a transitional zone between a continental margin and the open ocean; i.e., relatively close to terrestrial sediment input and far from hydrothermal activity. The accumulation of chert is related to its unique paleogeographic location in an equatorial setting with many submarine paleo-highlands. Intense upwelling and frequent local volcanism are the main factors that promoted the development of siliceous rocks in the studied area. Ocean acidification triggered by large-scale volcanism (Large Igneous Province) during the late Permian led to extensive silica precipitation and preservation.

The Chang-8 and Chang-6 members of the Upper Triassic Yanchang Formation (lower part) are regarded as the main oil producing members of the Ordos Basin. Recently, new hydrocarbon discoveries have been made in the upper part of the Yanchang Formation (e.g., Chang-3) in the southwestern Ordos Basin, implying that this interval also has a good potential for hydrocarbon exploration. However, studies on the origin of the high-quality reservoir, hydrocarbon migration, and accumulation patterns remain insufficient. In this study, integrated petrological, mineralogical, and fluid inclusion tests are employed to evaluate reservoir characteristics, and reconstruct the history of hydrocarbon migration and accumulation during oil and gas reservoir formation. The results reveal that the Yanchang Formation is characterized by low porosity (8 − 14%), medium permeability (0.5 − 5 mD), and strong heterogeneity; the reservoir properties are controlled by secondary porosity. Two types of dissolution are recognized in the present study. Secondary pore formation in the lower part of the formation is related to organic acid activity, while dissolution in the upper part is mainly influenced by atmospheric fresh water associated with the unconformity surface. The Yanchang Formation underwent hydrocarbon charging in three phases: the early Early Cretaceous, late Early Cretaceous, and middle Late Cretaceous. A model for hydrocarbon migration and accumulation in the Yanchang reservoirs was established based on the basin evolution. We suggest that hydrocarbon accumulation occurred at the early stage, and that hydrocarbons migrated into the upper part of the Yanchang Formation by way of tectonic fractures and overpressure caused by continuous and episodic hydrocarbon expulsion during secondary migration, forming potential oil reservoirs during the later stage.

China’s marine-continental transitional facies shale gas resources are abundant with shale gas resources of about 19.8 trillion cubic meters, while the exploration and development of these shale gas resources are still in the initial stage. The Upper Permian Longtan coal series shale is one of the most important transitional shales in the Yangtze platform, China. In this study, the comprehensive methods of mineralogy and organic geochemistry are used to discuss the characteristic of organic matter and sedimentary environment of the Longtan coal series shale in western Guizhou Province, South China. The results show that (1) the total organic carbon (TOC) content of this shale ranges in 0.6%-28.21%, mainly in 3%-12%, indicating a “good-excellent” hydrocarbon source rock, and its vitrinite reflectance () ranges from 1.48% to 2.93%, indicating a high-overmature organic matter; (2) the organic matter in this shale is multiorigin, and most of them come from the terrestrial higher plant while the rest come from the plankton; (3) type index (TI) of organic matter is from -65 to 41, indicating most of the kerogens which are II₁-III types; and (4) the sedimentary environment of this shale is dominated by suboxic-anoxic fresh water environment, which provides a favorable condition for the preservation of organic matter. In addition, the warm and humid climate during the Late Permian in the Yangtze platform promotes plant growth, and as a result, the Longtan coal series shale is rich in organic matter and has great potential of shale gas exploration and development.

Shock metamorphism of minerals in meteorites could help to understand the shock history of its parent body and also provide a window into the interior of the Earth. Although shock features in olivine have been well known within and adjacent to shock melt veins and shock melt pockets in meteorites, there are processes that are not yet completely understood. Ringwoodite is formed by crystallization from olivine melts or solid-state phase transformation of olivine. Typically, olivine clasts with a ringwoodite rim around an olivine core have been documented from only a handful of meteorites. Here we report results from GRV053684, a highly shocked L6 chondrite that was collected by Chinese Antarctic Research Expedition in 2006 to Antarctica. The investigations of the shock pressure history and the transformation mechanism of olivine to ringwoodite use optical microscope, electron probe microanalyzer (backscattered electron images, major element quantitative analyses, and quantitative wavelength-dispersive spectrometry elemental X-ray maps), and Raman spectrograph. Ringwoodite in the shock melt vein generally displays as Fe-rich (Fa_37-43) polycrystalline rims around Fe-poor (Fa_11-20) olivine core and as small individual clasts embedded in shock melt vein matrix. The difference in FeO between ringwoodite rim and olivine core implies that Fe was preferentially partitioned to ringwoodite. The occurrence of maskelynite (An₁₇) indicates a shock pressure ~30 GPa. The FeO and MgO diffusion indicates the transformation process of olivine to ringwoodite is a diffusion-controlled incoherent nucleation and growth. The spatial association between ringwoodite and the shock melt vein matrix suggests that high temperature plays a key role in prompting phase transformation.