Although Paleogene warm climatic intervals have received considerable attention for atmospheric and oceanographic changes, the authigenic mineralization associated with these time spans remains overlooked. An extensive review of the literature reveals a close correspondence between the high abundance of glauconite and warm climatic intervals during the Paleogene period. The abundance of phosphorite, ironstone, lignite and black shale deposits reveals similar trends. Although investigated thoroughly, the origin of these authigenic deposits is never understood in the background of Paleogene warming climatic intervals. A combination of factors like warm seawater, hypoxic shelf, low rate of sedimentation, and enhanced rate of continental weathering facilitated the glauconitization. The last factor caused the excess supply of nutrients, including Fe, Si, K, Mg and Al through the rivers, the cations needed for the formation of glauconite. The excessive inflow of nutrient-rich freshwater into the shallow seas further ensured high organic productivity and stratification in shallow shelves, causing hypoxia. The consequent rapid rise in sea-level during the warm periods created extensive low-relief shallow marine shelves starved in sediments. Oxygen-deficiency in the shallow marine environment facilitated the fixation of Fe into the glauconite structure. The inflow of nutrient-rich water during the warm climatic intervals facilitated the formation of phosphorite, ironstone, and organic-matter-rich sedimentary deposits as well. Although global factors primarily controlled the formation of these authigenic deposits, local factors played significant roles in some of the deposits. Therefore, phosphorites formed in marine conditions with open circulation within the tropical zone. While lush growth of rainforest covers in the tropical belt facilitated the formation of coastal lignite.

The Middle Permian Lucaogou Formation in the Jimusar Sag, eastern Junggar Basin, NW China, was deposited in a salt lake within an intracontinental rift basin with intense hydrothermal activity. Hydrothermal-sedimentary dolomite in the form of three types of dolostones, namely, analcime-feldspar dolostone (AFD), silicic dolostone (SD) and buddingtonite-albite dolostone (BAD), related to syn-sedimentary hydrothermal activity at lake bottom was discovered. The characteristics and formation mechanism of the dolomite were studied based on micron-scale petrographic and isotopic geochemical research. The syn-depositional formation of these dolostones was indicated by their rock-mineral features and syn-sedimentary deformation stage. The dolomite was composed of relatively poorly ordered proto-dolomite crystals with micron-sized spherical or sub-spherical morphology and coexisted with hydrothermal minerals, including analcime, buddingtonite, albite and chalcedony. Albite clasts were replaced by the dolomite, indicating high-temperature conditions during formation. The remarkably low strontium isotopic compositions of the dolostones (⁸⁷Sr/⁸⁶Sr with an average of 0.705687) indicated that mantle-derived materials might have involved in the ore-forming fluid. The dolostones had positive δ¹³C_PDB values (with an average of 6.94‰) and negative δ¹⁸O_PDB values (with an average of -8.12‰). Based on the δ¹⁸O_PDB values, the formation temperatures of the dolomite were at least ~25ºC higher than those of the penecontemporaneous dolomite in the Lucaogou Formation in the study area. It is concluded that the dolomite precipitated from hydrothermal fluid erupting at the lake bottom. The possible genetic models are described. We suggest that the hydrothermal-sedimentary dolomite is an important genetic type, and this study may help increase the awareness of this understudied type of dolomite.

A comprehensive sedimentary and reservoir analysis was conducted based on seismic, well logging, core and relative test data, taking Members 1 and 2 of Shahejie Formation of the early Oligocene in the steep slope belt, eastern Shijiutuo Uplift (STU), Bohai Bay Basin (BBB) as a case. The study indicates that a near-shore mixed fan deposit formed in the study area and developed characteristics and pattern of a high-quality reservoir. The mixed clastic-carbonate rocks constitute Members 1 and 2 of Shahejie Formation which developed along the steep slope belt and is named as a near-shore mixed fan. The mixed fan of the study area is mainly composed of microfacies of proximal channel, mixed deposited channel, mixed clastic beach, mixed bioclastic (grain) beach, with vertical multi-stage superimposition feature, and basically a similar shape as modern near-shore fans. It constitutes a new depositional type developing in the steep slope belt of a characteristic and complex lacustrine rift basin in the study area. This mixed fan in the steep slope of eastern STU is controlled by comprehensive factors including tectonics, clastic material supply, climate, palaeogeomorphology and hydrodynamic conditions. The reservoir quality of Members 1 and 2 of Shahejie Formation of eastern STU is, however, actually controlled by the sedimentary environment and diagenesis processes. Coarse-grained mixed rocks of near-shore fans, rich in bioclastics, can form excellent reservoirs, characterized by resistance to compaction, easy to dissolution, little influenced by burial depth and high production of oil and gas, which enable them become key exploration targets of medium- deep strata of BBB. Analyses of high-quality reservoir, its controlling factors and the oil and gas exploration implications of the near-shore mixed fan developing in the study area give a deeper insight into discussions of the same type of mixed rocks of other lacustrine rift basins worldwide.

The Permian Taiyuan and Shanxi formations exposed in Shandong Province, eastern North China, contain abundant spores and pollen. In this study, a total of 42 genera and 146 species of spores and pollen from these Permian formations, native to northern China, are identified and related to the three epochs of the Permian Period (Cisuralian, Guadalupian, and Lopingian Epochs) as two assemblages: Assemblage I — the Laevigatosporites-Granulatisporites assemblage, inferred as the Cisuralian (~298.9-272.9 Ma); and, Assemblage II — the Gulisporites-Sinulatisporites assemblage, inferred as the Guadalupian (~272.9-259.1 Ma). Assemblage I represents growing ferns, whereas Assemblage II represents gymnosperms. The assemblage division and analysis indicated that the palaeoclimate of the study area during Early-Middle Permian time was dominated by warm and humid conditions, and later in the Middle Permian changed into moderately dry conditions.

Sichuan Basin is very famous for the Mesozoic reptiles, especially the Jurassic dinosaurs. Here, we report some isolated plesiosaurian teeth and vertebrae newly excavated from the Middle Jurassic Xintiangou Formation in Yunyang county, Chongqing City, the northeastern region of the Sichuan Basin, southwestern China. The specimens are referred to Pliosauroidea based on the combination of the following features: the circular cross-section of the tooth crown, apicobasal ridges fully covering the enamel surface and reaching to the apex, the short and amphicoelous centrum, the centrum shorter than wide or tall, and the absence of a keel on the lateral surface of the cervical centrum. With the fragmentary nature, it is undetermined whether the Yunyang specimens belong to a known taxon or represent a new species of Plesiosauria. These plesiosaurian specimens further demonstrate that the freshwater plesiosaurians are common in the Jurassic deposits of the Sichuan Basin. For a comprehensive knowledge of the plesiosaurians of the basin in origin, distribution and diversity, to discover new and more complete specimens is necessarily the first priority.

The problematic calcareous microfossil Halysis is abundant in the Middle Ordovician Darriwilian Stage of the western edge of the Ordos Basin, North China. The rich and well-preserved specimens of Halysis in this area facilitate detailed studies for its skeletal construction and tube microstructure. Halysis differs from calcified cyanobacteria and calcareous red and green algae in morphology, skeletal construction and microstructure, as well as reproduction mode. Halysis typically consists of multiple juxtaposed parallel tubes arranged in sheets (‘multiple-tube' type) or is just composed of one tube (‘single-tube' type). In ‘multiple-tube' Halysis, tube fission by bifurcation results from the insertion of a microcrystalline wall at the center of a mother tube. This study demonstrates for the first time that the tube walls of Halysis have a laminofibrous (fibronormal) microstructure, composed of fibrous calcite perpendicular to wall surface, and recognizes the ‘single-tube' type Halysis composed of one tube; in addition, for the first time, this study finds out that ‘multiple-tube' Halysis develops buddings from the conjunction of two tubes and ‘single-tube' Halysis shows wide-angle Y-shaped branchings. Based on these findings, this study further compares Halysis with tabulate corals. Halysis appears stratigraphically earlier than Catenipora and Aulopora, and has a smaller tube size. ‘Multiple-tube' Halysis resembles Catenipora and ‘single-tube' Halysis resembles Aulopora in skeletal construction and microstructure, and in their tube walls of laminofibrous microstructure composed of fibrous calcite perpendicular to the tube wall surface. Catenipora and Halysis are both characterized by the absence of septal spines. The similarities suggest that Halysis may be the ancestor of Catenipora-like and Aulopora-like tabulate corals.

Zircons are abundant in the beach sediments. In this study, surface microtexture, mineralogy, bulk sediment geochemistry, trace element composition and U−Pb isotopic geochronology of detrital zircons collected from the Riachuelos and Palma Sola beach areas, southwestern Gulf of Mexico were performed to infer the sediment provenance and palaeoenvironment. The zircon microtexture was categorized as mechanically- and/or chemically-induced features. The weathering index values for the Riachuelos (~72−77) and Palma Sola (~71−74) beach sediments indicated moderate weathering of both of the two source areas. The major and trace element data of bulk sediments suggested passive margin settings for the two areas. The trace elemental ratios and chondrite-normalized rare earth element (REE) patterns of bulk sediments revealed that the sediments were likely sourced by felsic and intermediate igneous rocks. And the zircon Th/U ratios (mostly more than 0.2) and zircon REE patterns (with negative Eu and positive Ce anomalies) suggested a magmatic origin for both of the beach sediments from these two areas. Two distinct zircon age peaks respectively belonging to the Paleozoic and the Cenozoic were identified both in the Riachuelos and Palma Sola beach sediments. Zircon geochronology comparison research between the Riachuelos−Palma Sola beach sediments and potential source areas in SW Gulf of Mexico revealed that the source terrane supplied the Paleozoic zircons of this study was identified as the Mesa Central Province (MCP), and the Cenozoic zircons were transported from the nearby Eastern Alkaline Province (EAP). Moreover, although the Precambrian zircons were very few in the studied sediments, their geochronology and geochemistry results still could infer that they were contributed by the source terranes of Grenvillian igneous suites in the Oaxaca and the Chiapas Massif Complexes.