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How does a giant rift basin begin? No precise examples describe this issue. Based on 7108 m of continuous coring data recovered from the whole stratigraphy of the Songliao Basin (SLB), an attempt has been made to answer this question. Through comprehensive geological, geochemical and seismic research it has been found that there is a triangular extensional domain (TED) beneath the sedimentary cover in the basement at the rift center, from where the initial rupture of the giant rift was created. The basement detachment fault (DF), rift onset unconformity (ROU), and overlying basin fills are interrelated elements of a sedimentary basin and are the key to interpreting the geological archives recorded in the basin. The interaction processes between them determine the location of the basin center and the style of basement subsidence, which reflect the tectonic properties of the basin. This interaction may have a coevolutionary relationship with the deep magmatic activities beneath the basin. The basement of a basin typically consists of a series of strata that the lower strata age older. The uppermost basement sequence of the Triassic in the SLB is particularly important for the overlying basin formation and evolution. The surface topography controlled the thickness of the overlying Cretaceous cover. An ROU and DF developed at the top and bottom of the Triassic, respectively. The long-term uplift, denudation, and subsequent volcanic deposition may be common features of an ROU in a volcanic rift basin. More so, DF is the controlling factor for basin subsidence in the syn-rift stage of basin evolution. The frequent intrusive association with graben faults suggests that sublithospheric mantle flow may affect the accommodation space of the overlying basin by cutting the basement blocks via feeder dykes and shaping the graben pattern on top of the basement. • The world deepest continuous continental scientific drill project (ICDP) coring provides new insight into the Songliao Basin. • Rift onset unconformity, decollement and basin fills are interrelated elements. • Multi-layered downward aging basement successions may be found in any basin. • Triangle extensional domain (TED) beneath the sedimentary cover created rift centre. • Sublithospheric mantle flows affect accommodation space of overlying basin by dykes. [ABSTRACT FROM AUTHOR]

Two ice-rafted dropstones were discovered in the Yaojia Formation (early Santonian) of wells Ao14 and F247 in the Songliao Basin, northeastern China. The dropstone from well Ao14 was further studied using computed tomography (CT) scanning, sporopollen, carbon and oxygen isotope, and zircon U–Pb isotope analyses. The results show that the dropstone is composed of quartz monzonite and has an age of 178.0 ± 3.3 Ma. Based on the bedrock age analysis around the Songliao Basin, it is suggested that the dropstone in well Ao14 may have originated from the Zhangguangcai Range. The palynoflora assemblage indicates a mixed survival of cold and warm palynomorphs. The carbon and oxygen isotope compositions of the synsedimentary calcareous clasts surrounding the dropstone exhibit obvious negative biases, suggesting that glacier meltwater flowed into the paleo-lake, probably due to the significant topographic height difference between the Songliao Basin and adjacent areas during the early Santonian. Additionally, it can be inferred that coastal mountains formed in the Zhangguangcai Range area, which is located southeast of the Songliao Basin, and the dropstones derived from this region. During the cold season, the dropstones may be transported to the edge of Songliao Lake by avalanche and mixed with carbonate debris. As the seasons changed, the lake ice broke into pieces and carrying the dropstones and carbonate debris into the deep lake area. The present research provides direct evidence of a brief global cold event and the presence of high mountains in the southeastern Songliao Basin during the early Santonian in the Cretaceous greenhouse world. • The Late Cretaceous Santonian dropstone was first discovered in the Yaojia Formation, Songliao Basin. • The dropstone was transported to the center of the lake by ice rafts due to seasonal changes. • A short global cold event and the existence of high mountains in the southeastern Songliao Basin during the early Santonian. [ABSTRACT FROM AUTHOR]

Natural fibrous gypsum is a kind of high-quality gypsum resources, whose high-value added utilization pathway is to be transformed to α -calcium sulfate hemihydrate (α -HH), a cementitious material that can react with water to form pastes with mechanical strength. In this work, α -HH was prepared from natural fibrous gypsum in KCl mediated glycerol-water solution under mild condition. KCl played a simultaneous function on regulating the phase-transition kinetics, morphology and comprehensive strength of α -HH. Addition of low concentration of KCl prominently retarded the nucleation and growth rate of α -HH and decreased its aspect ratio due to the formation of syngenite on the side faces. While further increase of KCl concentration accelerated the nucleation and growth rate and decreased the crystal sizes. In the presence of 0.04 M KCl, the prepared α -HH presented a hexagonal prism shape with a length / width of 257.69–579.71 μm / 13.13–36.61 μm, and its dry comprehensive strength had reached 38.1 MPa that was comparable to those prepared in commercial, chloride and nitrate system. Altogether, the foreign ion-free glycerol-water solution contributed to transforming natural fibrous gypsum to α -HH with high purity and high mechanical strength. • Transformation of natural fibrous gypsum to α -HH in glycerol-water solution. • Regulation of KCl on phase-transition kinetics, morphology and mechanical strength. • Hexagonal prism shape α -HH with high aspect ratio presents high mechanical strength. • α -HH paste with high mechanical strength has a compact microstructure. [ABSTRACT FROM AUTHOR]

Volcanism is a natural climate force that causes variations in temperatures. The Aptian Oceanic Anoxic Event 1a (OAE-1a) was preceded by a prominent negative C-isotope excursion attributed to major volcanism of the Ontong Java plateau (OJP), which presumably resulted in a pCO 2 increase and a climatic change. However, the OJP alone may not adequately explain some important isotopic signatures such as the negative strontium-isotope excursion from 125 Ma to 113 Ma that is recorded in the corresponding marine deposits. We present an independent and hitherto undocumented case, the giant Aptian volcanism in the Songliao Basin and northeast Asia (SB-V) on the Cretaceous active continental margin between the Eurasian and the Pacific plates, which covered an area of ca. 2.3 × 10 6 km 2 , nearly matching the simultaneous case of the OJP. Intensive strong, explosive volcanic eruptions of the SB-V occurred at 121–109 Ma and introduced a large volume of fine-grained volcanic ash and degassing volatiles into the atmosphere. The Aptian isotopic ratios ( 87 Sr/ 86 Sr, 206 Pb/ 204 Pb, 207 Pb/ 204 Pb, and 208 Pb/ 204 Pb) of marine carbonates from the Mid-Pacific shift in values between their Barremian pre-excursion high values and the negative magmatic values of the SB-V. The transient global cooling at the onset of the OAE-1a coincided with the beginning of the violent acidic eruption of the SB-V (119.9–120.2 Ma). We therefore infer that the SB-V must have played a role in the Aptian global climatic changes and OAE-1a through the heavy fall of volcanic dust and the outgassing of aerosol and greenhouse gases. [ABSTRACT FROM AUTHOR]

This study attempts to augment geology and potential hydrocarbon play system database not only in the Maamba Coalfield basin of southern Zambia but in other similar continental non-marine Karoo rift basins in the region as well. Geological analyses were conducted through extensive outcrops and exposures and subsurface boreholes. Six (6) major lithofacies (diamictites, conglomerates, sandstones, siltstones, coal and mudstones) represents Lower Karoo Group sequence. Four (4) mudstone core samples were prepared for thin section petrography. In addition, six (6) samples of sandstones obtained from outcrops, exposures and cores were impregnated with blue epoxy before thin sectioning in order to facilitate easy recognition of porosity. Quantification of framework grain composition and porosity was achieved by point counting a total of 300 points per thin section. The identification of diagenetic constituents and pore types was made possible by the use of scanning electron microscopy (SEM). Rock-Eval pyrolysis analyses utilised 35 core samples of mudstones and coal. According to results of the analyses, three (3) deposition settings which include; alluvial, fluvial-lacustrine and lacustrine setting are envisaged. . Fluvial-lacustrine deposits are host to mudstones and coal source rocks and sandstone reservoir rocks. Mudstones and coal source rocks gave the total organic carbon (TOC) that is well above the recommended thresholds of 0.5 wt % and 2.5 wt % of gas and oil generation respectively. The hydrogen index (HI) values are mostly below 200 mg HC/g TOC, indicating fair quantities of type III kerogen. The thermal maturity readings measured by temperature T max range from 440 to 485 °C in agreement with calculated vitrinite reflectance (Ro calc ) range of 0.76–1.57% indicating mature to post mature stages. This maturation is attributed to the burial temperatures and near-surface heat flows by faults. Production Index (PI) values are less than 0.1 suggesting some hydrocarbon expulsion possibly gases and gas condensates. Sandstones are moderate to poor sorted sublitharenites. Total porosity in sandstones range between 0 and 6.3%, averaging 2.5%, and is mainly secondary porosity resulting from dissolution of labile minerals and fracture. Deposition and diagenetic related controls influenced much of the reservoir quality in sandstones. Lacustrine mudstones are the potential seal rocks. The major Structural traps are faults (e.g. normal and reverse faults) and the stratigraphic traps are sandstones. In this study, our area of focus is in the north and central part of Maamba Coalfield Basin where coal mining and exploration activities are currently taking place. The southernmost part of the basin is under developed such that the hydrocarbon play system potential is still unknown. However, recent coal exploration drilling has revealed the presence of source rocks at depth overlain by extensive overburden seal rocks. Based on the play concept analysis, it is possible to find more encouraging results from this area. [ABSTRACT FROM AUTHOR]

Abstract: The spinicaudatan (conchostracan) Dictyestheria, originally recovered from the Yaojia Formation, is recognized to occur also in the basal part of the overlying Nenjiang Formation. This means that the Dictyestheria elongata (= D. ovata) Zone extends from the Yaojia Formation into the upper Turonian basal part of the First Member of the Nenjiang Formation and underlies the Halysestheria yui Zone at Yaojia Railway Station, Dehui City, Jilin Province, northeast China. The fossil record shows that the basal part of the Halysestheria yui Zone is dominated by Plectestheria songhuaensis in the study area. The diagnoses of Dictyestheria and Plectestheria are revised on the basis of an examination of specimens under a scanning electron microscope. In both genera the radial lirae on the growth bands near the umbo are long and relatively widely spaced. There is a fine reticulum between them in the umbonal part of the carapace and cross-bars occur on the ventral surface. The ornament of both genera indicates that they can be assigned to the family Halysestheriidae rather than to the Jilinestheriidae, in which they have been placed previously. The discovery of serration along the lower margins of growth lines in Plectestheria indicates its close relationship with Orthestheria (Migransia), supporting an interpretation of parallel evolution of O. (Migransia) to Plectestheria in East Asia and Bauruestheria in South America. [Copyright &y& Elsevier]

• Triassic paleobiogeography of PSCS was constrained by both Pacific and Tethys oceans. • Triassic PSCS subjected to tectonic overprints of Pacific and Tethyan tectonic regimes. • Early–Middle Jurassic paleobiogeography of PSCS was controlled by the Pacific Ocean. • Late Jurassic–Cretaceous PSCS was in a semi-closed environment. • Jurassic–Cretaceous PSCS was part of the Paleo-Pacific slab. The Proto-South China Sea (PSCS) represents the lithosphere that formerly occupied the region southeast of South China where the present-day South China Sea is located. The subduction and demise of the PSCS have attracted wide attention, whereas the pre-subduction history (particular the Mesozoic) of the region remains relatively neglected. In this paper, the radiolarian paleobiogeography of the region is analyzed to identify the paleobiogeographic affinity and paleo-connectivity of the PSCS with the Pacific and Tethys oceans during the Mesozoic. Then the continent–ocean configuration and tectonic evolution of the PSCS and adjacent areas are discussed through the integration of paleobiogeographical results and associated paleomagnetic, stratigraphic, and petrologic data. The main conclusions are as follows: (1) During the Triassic, the PSCS was situated in the transition zone between the Pacific and Tethys oceans, and its paleobiogeography was influenced by both oceans. The PSCS was characterized by complex tectonic overprinting by the Pacific and Tethyan tectonic regimes. (2) In the Early–Middle Jurassic, the PSCS was well connected to the Pacific Ocean but poorly connected to the Tethys Ocean, consistent with the paleobiogeography of the PSCS being mainly constrained by the Pacific Ocean. The PSCS was part of the Paleo-Pacific slab. (3) During the Late Jurassic–Cretaceous, the PSCS was in a semi-closed environment. The Late Jurassic–early Late Cretaceous PSCS was part of a west-facing Andean-type subduction zone, and the late Late Cretaceous PSCS was situated in an extensional tectonic setting. [ABSTRACT FROM AUTHOR]

We discuss the types, capacity, formation mechanisms, and main controlling factors of oil and gas reservoir spaces in Early Cretaceous acidic volcanic rocks of the Hailar Basin, NE China, where asphalt-bearing volcanic rocks are exposed at the surface. We have made systematic observations and analyses on macroscopic (outcrop) and microscopic (optical microscope, SEM, and fluorescence analyzer) scales. Acidic volcanic reservoirs contain reservoir spaces comprising primary and secondary porosity, which are dependent on primary and secondary processes during their formation. Primary porosity typically accounts for a large contribution to enhanced reservoir quality. More importantly, it is a prerequisite for migration, alteration, and filling by inorganic fluids and petroleum, which provides a foundation for the development of secondary porosity. The development of secondary porosity, especially alteration-related pores, can significantly modify the petrophysical characteristics of a rock. In addition to the processes of porosity formation, the quality of volcanic reservoirs is influenced by factors such as lithology, lithofacies, and tectonism. Lithological differences result in variations in the type and intensity of pore development. Pyromeride and glassy lava commonly exhibit high reservoir capacities. The porosity of different lithofacies typically follows the order of conduit facies > extrusive facies > effusive facies > explosive facies. Tectonism is necessary for the formation of reservoir spaces and for the migration, permeation, and accumulation of oil and gas. Reservoir quality is often positively correlated with the size and density of tectonic fractures. [ABSTRACT FROM AUTHOR]