Triassic

摘要： In the Triassic marine sediments, an obvious enrichment of lithium has been found. The source and enrichment mechanism of lithium is unknown. Here, we report trace and rare earth element and isotope analyses for Triassic sedimentary samples from core ZK601, recovered from the Huangjinkou anticline in the Xuanhan basin. Lithium concentrations from the Leikoupo and Jialingjiang formations are much higher than the average concentrations in the crust of eastern China and in other marine sediments. Lithium concentrations are highest at depths of 3300–3360 m(in argillaceous marine sediments), and Li is positively correlated with Rb, Ga, Zr, Nb and other trace elements. The range of δ^(7)Li values in our samples is consistent with that in other Triassic marine carbonate rocks. Lithium concentrations and isotope ratios are negatively correlated in the argillaceous dolomite samples at depths of 3300–3360 m. We compared the results in this study with trace and rare earth elements in the clay from Sichuan and Chongqing, and propose that the clay in the argillaceous marine evaporites from Huangjinkou formed via the hydrolysis of volcanic ash during Early–Middle Triassic volcanic eruptions into brine basins, during which clay adsorbed Li from the brine and formed Li-rich argillaceous dolomites. The addition and hydrolysis of volcanic ash in the evaporative brine is also related to the formation of a new type of polyhalite.

摘要： Based on field geological survey,interpretation of seismic data and analysis of drilling and logging data,the evolution of geological structures,stratigraphic sedimentary filling sequence and sedimentary system around the Bogda Mountain were analyzed according to the idea of"structure controlling basin,basin controlling facies and facies controlling assemblages".The tectonic evolution of the basin around the Bogda Mountain can be divided into nine stages.The Middle-Late Permian–Middle-Late Triassic was the development stage of intracontinental rift,foreland basin and inland depression basin when lake,fan delta and braided river delta sedimentary facies developed.Early intracontinental rifting,late Permian tectonic uplift,and middle-late Triassic tectonic subsidence controlled the shape,type,subsidence rate and sedimentary system evolution of the basin.The Bogda Mountain area was the subsidence center and deposition center of the deep water lake basin in the Middle Permian with mainly deep-water deposition and local gravity flow deposition.This area had tectonic inversion in the Late Permian,when the Bogda Mountain uplifted to form a low bulge and a series of fan delta sand bodies.In the Middle-Late Triassic,subsidence occurred in the Bogda low uplift,characterized by extensive development of braided river delta deposits.

摘要： 1.Objectives In the Indosinian duration,series of Gondwana-related plates pieced together and formed the geological sketch of China for the first time,i.e.the Yangtze,Sino Korean,Tarim plates,and other sub-plates that had been isolated for a long time.Subduction and collision among the Tarim,Qaidam,and Qiangtang blocks in Triassic,as well as the closure of the Paleo-Tethys Ocean,reactivated Late Paleozoic suture zones in the Tianshan orogen region(Hendrix MS et al.,1992).

摘要： The Late Triassic Nurzhanov flora is characterized on the basis of the material originated from the S.Nurzhanov-509 borehole disposed in the northern part of the Fore-Caspian depression,near the City of Atyrau,Republic of Kazakhstan.Taxonomic composition of the Nurzhanov flora includes equisetophytes Neocalamites sp.,ferns Phlebopteris hazarensis Naugolnykh et Pronin,Todites sp.,Cladophlebis sp.,ginkgophytes Ginkgoites spp.,conifers Podozamites sp.Palaeophytogeographic status of the Nurzhanov flora is discussed.According to the data obtained,this flora belongs to a transitional zone(an ecotonous belt),which existed between the Euro-Sinian and the Siberian-Canadian palaeofloristic realms during most of the Mesozoic time.

摘要： Monazite is an important accessory mineral in the pelitic granulites(Weihai area,Sulu orogen),and is also a powerful monitor for understanding the metamorphic evolution of the granulites.The pelitic granulites incongruously occur as lenses in granitic gneisses.The lithologies of the lenses gradually change from core to margin:The undeformed coarse-grained granulite,the foliated fine-grained granulite,the garnet-biotite-gneiss,and the migmatized granulite.The lens cores mostly preserve a peak granulite-facies metamorphic mineral assemblage of garnet+plagioclase(antiperthite)+quartz+sillimanite+biotite with accessory minerals of rutile,zircon,and monazite.The lens margins display a fluid-induced retrogression.In order to decipher the metamorphic processes of the pelitic granulites,a combined study of BSE imaging,U-Pb dating,and trace element composition for the monazites from the metapelitic lens were conducted.Monazites from the undeformed coarse-grained granulite only record a Paleoproterozoic age(1832±7 Ma,n=40).Monazites from the other lithologies yield the inherited Paleoproterozoic age and Triassic overgrowth age.For example,monazites from the migmatite yield intercept ages of 1818±10 and 211±22 Ma(n=56)with Triassic concordant age of 223.8±2.9 Ma.The Paleoproterozoic monazites are characterized by remarkable depletion in HREE and Y with obviously negative Eu anomalies,indicating their formation equilibrated with garnet and feldspar under granulite-facies conditions.During Triassic fluid modification,the monazite bright rims assimilated Th and Si but released U,HREE,Y,and P.This process resulted in that the Triassic overgrowth monazites have higher HREE and Y contents,and lower Th and U contents with relatively low Th/U ratios.Thus,the monazites in the pelitic granulites recorded a Paleoproterozoic metamorphic event and Triassic fluid modification.The Weihai pelitic granulites might have a tectonic affinity with the North China Craton.Therefore,the Paleoproterozoic pelitic granulites were mechanically drawn into the orogen during the Triassic continental collision,and subsequently were remoulded by the fluids during its exhumation.

摘要： Based on geochemical analysis results of core samples from the Triassic Chang 7 Member of Well Feng 75 drilled in the northwest margin of Ordos Basin,combined with geological characteristics of this region,the formation environment of the black shale and its control on shale oil enrichment are comprehensively studied.From the Chang 73 to Chang 71 Sub-members,the black shale have organic carbon contents decreasing from 5.70%to 3.55%,hydrogen indexes decreasing from 345 mg/g to 269 mg/g,while the oxygen indexes increasing gradually from 6 mg/g to 29 mg/g,indicating that the sedimentary environment during the depositional period of Chang 72 and Chang 73 Sub-members was anoxic.Biomarkers in the black shale change regu-larly,and have an obvious“inflection point”at the depth of 2753–2777 m in the Chang 73 Sub-member,indicating that the input of terrigenous organic matter increased.However,there is a negative drift about 2%of organic carbon isotopic composition near the“inflection point”,which is in conflict with the results of biomarker compounds.This is because the extreme thermal and anoxic events caused by continental volcanic activity in the ancient Qinling region caused negative drift of carbon isotopic composition of the black shale in the Ordos Basin.The volcanic activity caused rise of temperature,polluted air,extreme weathers,more floods and thus more input of terrigenous organic matter,and gave rise to extremely anoxic environment con-ducive to the preservation of organic matter.Terrigenous organic matter is more conducive to the formation of light oil than aquatic organic matter,so these sections in Yanchang Formation are major“sweet spots”for shale oil enrichment.

摘要： The Triassic rocks are widespread in China, and both marine and terrestrial strata are well developed. The Triassic stratigraphic architecture of China is very complex in both spatial variation of the so-called "South Marine and North Continental", i.e. the southern areas of China occupied mostly by marine facies while the northern China by terrestrial facies during the Triassic Period, and temporal transition of the "Lower Marine and Upper Continental", i.e. the lower part of the Triassic System composed mainly of marine facies and the upper part of terrestrial strata especially in South China. Although the Global Stratotype Section and Point(GSSP) of the Permian-Triassic boundary is located in South China, the Triassic of China except for some marine Lower-Middle Triassic depositions shows significantly local characteristics and is hardly correlated with the global chronostratigraphic chart. Consequently, the Triassic of China contains not only the international research hotspots but also difficult points in stratigraphic study. This paper aims to present a brief review of the Triassic in China, including chronostratigraphy, biostratigraphy, magnetostratigraphy and chemostratigraphy, and summarize an integrated Triassic stratigraphic framework of China. Accordingly, a stratigraphic correlation is proposed for the lithostratigraphic sequences among the three tectono-paleogeographic stratigraphic regions. The comprehensive study indicates that ammonoids are the classic index fossils in Triassic biostratigraphy but conodonts are more advantageous in the study and definition of the Triassic chronostratigraphic boundaries. China still has the potential to optimize the GSSPs of the Induan-Olenekian boundary and Olenekian-Anisian boundary. The correlation of the Permian-Triassic boundary between marine and terrestrial facies might be achieved with the help of the Permian-Triassic "transitional bed" and its related biotic and environmental events in association with the biostratigraphic study of conchostracan, vertebrate and plant fossils. In addition, the carbon isotopes have been proved to be one of the powerful methods in marine Triassic stratigraphic study, whereas the oxygen and strontium isotopes may be additional important bridges to establish the correlation between the marine and terrestrial strata, but as yet lacking of relevant studies in terrestrial strata. Considering the most stratigraphic intervals of the Triassic and the terrestrial Triassic in China are difficult to be correlated to the global chart, the proposed Chinese(regional) Triassic chronostratigraphic chart of marine and terrestrial stages would be of importance to the study of Chinese Triassic stratigraphy and related aspects, but the stages must be conceptually in line with international standards and studied as soon as possible in order to finalize the definition.

摘要： The dominating hypothesis stated that angiosperms originated in the Early Cretaceous, there were no pre-Cretaceous angiosperms, and carpels (the basic units of gynoecium) were derived from former megasporophylls bearing ovules/seeds along their margins through longitudinally folding and enrolling. However, there are increasing evidences of pre-Cretaceous angiosperms, the assumed megasporophyll actually does not exist, and the Cretaceous-only history of angiosperms appears much shorter than suggested by molecular clocks. Here I will integrate new knowledge of living and fossil plants to give a plausible explanation for the origin and early evolution of angiosperms. Several lines of evidence indicate that the ancestor of angiosperms may well have been present in the Triassic. The former gap between angiosperms and gymnosperms is artificial. Some Triassic fossils playing a role intermediate between angiosperms and gymnosperms seem to favor the Unifying Theory.

摘要： Oxygen isotope (δ18O) serves as paleothermometer,and provides paleotemperature for carbonates. δ18O signature was used to estimate the temperature of fractionation of dolomite and calcite in Montney Formation, empirically calculated to have precipitated, between approximately 13°C to ±33°C during Triassic time in northeastern British Columbia, Western Canada Sedimentary Basin (WCSB). Measurements of stable isotopes (δ13C and δ18O) fractionation, supported by quantitative X-ray diffraction evidence, and whole-rock geochemical characterization of the Triassic Montney Formation indicates the presence of calcite, dolomite, magnesium, carbon and other elements. Results from isotopic signature obtained from bulk calcite and bulk dolomite from this study indicates depleted δ13CPDB (-2.18‰ to -8.46‰) and depleted δ18OPDB (-3.54‰ to -16.15‰), which is interpreted in relation to oxidation of organic matter during diagenesis. Diagenetic modification of dolomitized very fine-grained, silty-sandstone of the Montney Formation may have occurred in stages of progressive oxidation and reduction reactions involving chemical elements such as Fe, which manifest in mineral form as pyrite, particularly, during early burial diagenesis. Such mineralogical changes evident in this study from petrography and SEM, includes cementation, authigenic quartz overgrowth and mineral replacement involving calcite and dolomite, which are typical of diagenesis. High concentration of chemical elements in the Montney Formation?-Ca and Mg indicates dolomitization. It is interpreted herein, that calcite may have been precipitated into the interstitial pore space of the intergranular matrix of very fine-grained silty-sandstone of the Montney Formation as cement by a complex mechanism resulting in the interlocking of grains.

摘要： Among small sized gastropods found in Aqaba (Jordan), Sansonia occurs relatively common with Sansoniacebuana which is recognized from the the fringing reef near the Marine Biological Station at Aqaba, while Mecoliotia and Chrystella are rare. Mecoliotia aqabaensis n. sp and Chrystella shinaqi n. sp are described with the later resembling Chrystella finckhi. They are compared with other members of the Pick-worthiidae, of which a new species of Discrevina from Indonesia is described. A species of Aqabarella new genus resembles in shape of its teleoconch members of the Pickworthiidae but its protoconch is distinct in ornament of the larval shell and shape of the aperture and it is placed in it own family, Aqabarellidae. Aqabarella urdunensis is relatively more common than the rare Aqabarella pulchella. Similar larval shells are found in Vanikoridae, Planaxidae and Cerithiidae, those of Littorinidae and Rissoidae are more distinct and all of them differ from those of the Aqabarellidae, while some ancient small species from the Triassic tropical Tethys had a similar protoconch.