Earth’s atmosphere is overwhelmingly dominated by two types of gas: N₂ and O₂. The nitrogen(N₂)is primordial,and its presence and abundance are not driven by biological processes. In contrast,the oxygen(O₂)is continuously produced biologically via the oxidation of water driven by energy from the Sun. How did O₂,a gas critical to the evolution of animal life,become the second most abundant gas on Earth?The problem is not as simple as it might first appear. In order to understand this problem,we must know not only how and when O₂ was first generated,but also how it came to persist in high concentrations in the atmosphere. Two facts are known with certainty,that are,Earth’s earliest atmosphere was essentially devoid of oxygen;and today’s 21% of atmosphere is composed of oxygen. It should be emphasized that most geological indicators of ancient atmospheric oxygen levels imply only presence or absence and that most of the events that took place between those following two time points are highly uncertain. A battery of geological indicators suggests the timing of the rise of atmosphere oxygen occurred at following time points:(1)A shift from an anoxic to an oxic atmosphere some time between 2.5 and 2.0 billion years ago,which is known as the Great Oxidation Event(GOE);(2)A second‘Great Oxidation Event’ during the Precambrian-Cambrian transition between about 0.85 and 0.54 billion years ago(GOE-Ⅱ),which is herewith referred to as the Neoproterozoic Oxygenation Event(NOE). Both the GOE and the NOE lead to a prevailing view of atmospheric oxygen evolution over time that is marked by a three durations for the atmospheric oxygen level. Following important cognitions are gained with the further research. If the overall increase in atmospheric O₂,from negligible in the early Archaean to 21% today,was due to the increasing oxygen production as erosion and sedimentation became increasingly important relative to volcanic activity,so, the series of step increases in O₂, associated with periods of anomalously high sedimentation following supercontinent amalgamation,superimposed on this overall trend, which demonstrates that the rise of atmospheric oxygen is resulted from the sophisticated geobiological process that is closely genetically related to geodynamics. The stepwise rise for the atmospheric oxygen is further grouped into 7 events that can be correlated with the period after the supercontinent amalgamation in the history of the Earth,which provides a more clear view;importantly,enhanced sedimentation during these periods promoted the burial of a high fraction of organic carbon and pyrite,thus preventing their reaction with free oxygen,and leading to sustained increases in atmospheric oxygen. Both novel viewpoints and important cognitions provide many important thinking approaches and researching clues for the further understanding of the geobiological process for the rise of atmospheric oxygen. Therefore,tracing these research advances on the study of rise of atmospheric oxygen is helpful to drive new research that will unveil new truths about the evolutionary history of the atmosphere of our planet.

Deep-water carbonate rocks and its dolomitization of the Middle and Upper Ordovician Queerquek Formation in Kuluketage Mountain,northeastern Tarim Basin,is one of special types of deposition and diagenesis. By detailed observation and sampling of the Nanyaerdangshan section,we studied the sedimentary,petrological and geochemical features of the dolomitic beds. The deep-water carbonate rocks,which occurred in thrust-nappe or gravity-related sliding shapes in the stratigraphic column of the outcrop, is of yellow and dark grey,thin to medium bedding dolostone interbedded with mudstone,marl and shale,usually irregular and lenticle “knotty nodule”accompanied with turbidite of fine rocks debris either at the bottom or at the top. It is characterized by the planktonic faunas such as trilobite,siliceous sponge spicules and echinoderm fragments,and richness in poorly sorted terrigenous sediment attributed to grantite,volcanic and siliceous rocks. The carbonate rocks exhibited a certain rhythm structures such as dissolved-bedding,thin-horizontal bedding and few of algae laminae in primitive sediment. The main mineralogical peculiarities of dolostone composed of nine various types i.e.,near-micritic,giant ooids,fine-crystalline dolostone,bitumen-bearing algae poloid dolostone with residual bioclastics and silicification,and so on. The low and middle degree of order varies between 0.47-0.56 and 0.70-0.76, with a medium and extensive cathodluminescence(CL),indicating two-episodes strong dolomitization. The carbonate rocks have the abundance of SiO₂ and Al₂O₃, and richness of Mg、Mn、Fe、MnO and TiO₂. The value of δ³⁴S_V-CDT(-0.2-6.6) and REE(46.7×10^-6-67.4×10^-6) are similar to the shale on the “cap-form”distribution pattern of rare earth elements with positive europium(δEu)and negative cerium(δCe), indicating a relative reduction deep-water environment. The salinity index such as Na₂O+K₂O,Sr and Sr/Ba, are rather low,compared with those of typical terrace carbonate rocks. Since the higher ⁸⁷Sr/⁸⁶Sr ratio of the dolostone with rather low values ofδ¹⁸O_PDB δ¹³ C_PDB,it can’t be interpreted as a typical of isotopic feature of coeval seawater. Therefore,the deep-water carbonate rocks were developed in a shallowing-up parts of gentle-slope, then suffered two-episodes dolomitization at shallow buried or middle and deep buried respectively,and finally were thrusted or gravities-slided into outer continental shelf or lower parts of slope,with dolomite and calcite, hydrocarbon fillings in dissolved-vugs-fractures.

Based on the outcrops observation and survey, thin sections identification,geochemistry analysis and temperature measuring of fluid inclusions,we studied the lithofacies,geochemical characteristics and structural feature of the leopard limestone from the Members 4 and 6 of Ordovician Majiagou Formation(M4 & M6 intervals)in Ordos Basin. In the Jinsushan section of southern Ordos Basin,three parasequence sets are divided by the eustasy in the M6_B interval. The two parasequence sets in the lower part are mainly composed of leopard limestone,in which the continuity and ordering degree of the dolomite mottle are enhanced in ascending order. The dolomite mottle is comprised of euhedral to semihedral dolomites, with the relatively high value of δ¹³C, relatively low value of δ¹⁸C and ⁸⁷Sr/Sr⁸⁶, lower concentration of Fe and Mn, and higher salinity ratio and inclusion homogenization temperature. The results show that the leopard limestone of M4 & M6 intervals was mainly formed at the burial stage during which with the increasing buried depth and formation temperature, the dolomitization occurred by the evaprative seawater in the boriny pore refluxed at low sea-level period.

A set of gravity flow sediments is found in the Lower Permian Qudi Formation in Ni’ema Mountain of Rongma area,Tibet. According to the lithology,sedimentary structures and fossil records,9 rock types and 5 rock associations can well be identified. These rock types belong to the inner fan,the middle fan, and the outer fan respectively of submarine fan and can be subdivided into the main channel and inter-channel microfacies of inner fan,the branch channel,natural levee and inter-channel microfacies of middle fan,the leafy sand body and ending channel microfacies of outer fan,as well as the deep-sea basalt and mudstone. Therefore,it is fairly concluded that the Qudi Formation in the study area is an abyssal fan formed in a bathyal to abysmal settings. Obviously,this conclusion is different from the previous so called shallow marine Qudi Formation,and it can be illustrated that the sedimentary environment of the Qudi Formation in the Southern Qiangtang Basin is obviously different regionally in the west from in the east direction,which was gradually changed from the shallow marine in Ritu in the west to the abysmal-bathyal in Gaize and Nima in the east. It also shows that the Palaeotethys in the study area was at the mature evolutionary stage in the Early Permian,and the time when Qiangtang block rifted and drifted from the northern margin of Gondwana is earlier in the east than in the west. The discovery of the large set of deep water black gravity flow sediments of the Qudi Formation shows that it has a great significance of petroleum geology.

Based on core observation, well logs and 3-D seismic data, the research in the “source-to-sink” system of the Lower Member 3 of Paleogene Shahejie Formation in the steep slope zone of Western Chezhen sub-sag of Chezhen sag, Bohai Bay Basin, is conducted. The results show that:(1)The Lower Member 3 of Shahejie Formation is a third-order sequence which can be divided into three system tracts, including the lowstand system tract, transgressive system tract and highstand system tract, and in the steep slope zone, 11 gravity flow rock types and deep-lacustrine mudstone can be identified,and the gravity flow rock types include matrix-supported medium-grained conglomerates,clast-supported medium-grained conglomerates,matrix-supported fine-grained conglomerates,clast-supported fine-grained conglomerates,sandy conglomerate,conglomeratic sandstones,coarse sandstones,medium sandstones,fine sandstones,graded bedding sandstones and slumps,they are all the typical characteristics of the near-shore subaqueous fan. The evolution tendency of fan scales is from increasing to decreasing,and then increasing again as a whole. (2)Six provenance supplying systems can be identified in the steep slope zone of Western Chezhen sub-sag,and they can be divided into two types,namely,gully-dominated provenance supplying systems and slump-dominated provenance supplying system. The slump structure are much more widely developed in the fans associated with the slump-dominated provenance supplying systems than the fans associated with the gully-dominated provenance supplying systems,in addition,the scale of slump near-shore subaqueous fans is smaller than the fans associated with gully. (3)The further study on the “source”area’s characteristics shows that,the parent rock developed in the depositional period of the Lower Member 3 of Shahejie Formation of the source area was mainly the carbonate rocks; under the action of strong tectonic activities and warm-wet climate,the source area may developed stony desertification palaeogeomorphology and strong erosion,which would cause frequent seasonal gravity to be transported into the lacustrine and form the near-shore subaqueous fans; the scale difference of the fans developed in different system tracts were mainly controlled by the climatic variation and vegetation cover of the source area.

Exploration for petroleum in the Paleozoic marine carbonate rocks is of great significance to China’s energy security. Based on the analysis of the newest data for oil-gas fields,this study attempts to document the geological features and distribution patterns of giant marine carbonate rock oil-gas fields in the Paleozoic throughout the world. A total of 89 giant marine carbonate rock oil-gas fields in the Paleozoic had been discovered in 15 basins in the world by the end of 2013. Recoverable oil and gas reserves in these giant fields amount to 495.9×10⁸ t oil equivalent,which make up 20.9% of the total recoverable reserves in all marine carbonate rock fields in the world. Results show that giant oil-gas fields mainly occur in the Middle East,former Soviet Union,North America and Asia Pacific,of which, giant oilfields are mainly distributed in former Soviet Union and North America,while giant gas fields are mainly confined to the Middle East and Asia Pacific. The peak discovery of giant gas fields occurred in 1970s. Oil and gas in the giant oil-gas fields were largely derived from the Paleozoic source rocks. In terms of relative importance,the most important source intervals are the Silurian, Carboniferous, Permian and Devonian. The source rocks are dominated by mudstones and shales,bituminous mudstones and shales and bituminous carbonate rocks. Evaporites and clastic rocks are the dominant seal rock. Stratigraphically,the reserves are concentrated in three stratigraphic units: the Permian, Carboniferous and Ordovician. Dolostone and reef reservoirs are of particular significance. The petroleum reserves are largely accumulated in three stratigraphic units of burial depths: 2500~3000,m(hosting 52.6% of the total),3500~4000,m(15.9%),and 4000~4500,m(9.5%). Structural traps are the main trap types for the giant oil-gas fields,but the proportion of non-structural traps has increased for the newly discovered giant oil-gas fields. For marine hydrocarbon exploration in China,it is suggested that a greater attention should be paid to dolostone reservoirs. More importantly,the studies of hydrocarbon accumulation mechanism and controlling factors for hydrocarbon distribution in deep marine carbonate strata should be strengthened.

Biyang sag,located in the southeast margin of the Nanxiang Basin,is a continental faulted basin and shallower in the northwest than in the southeast. In the central part of Anpeng area,dolostones with huge thickness developed in the Paleogene. The main ore deposits occurred in the upper Member 3 and the lower Member 2 of the Hetaoyuan Formation,and is closely related to dolomitic strata. Based on cores,logging and seismic data,the alkaline rock series stratum of the Paleogene Hetaoyuan Formation can be divided into three second-order cycles,and further can be divided into eight third-order cycles. The trona ore seam is located at the top of the basic sequence and the upper parts of the second-order cycle or third-order cycle,and the alkali rock stratigraphic sequence varies regularly from the laminated dolostone to the trona ore seam. According to trona ore seam vertical change rule, prospecting prediction and predicting seam position in drilling have made good effect. And according to the research of the salt mineral depositional cycle,there may be a potassic salt at the top of the first-order cycle,which indicates the possibility of discovery of potash deposits.

The Early Triassic,as an interval following the mass extinction at the Permo-Triassic boundary,representing the ecosystem reconstruction and recovery after the end-Permian biotic crisis,has been garnered much attention in the geological fields. In order to approach carbon isotopic composition and evolution of Early Triassic seawater,we examined the δ¹³C value of 258 carbonate samples from the Early Triassic(including adjacent strata)from Dukou section in Xuanhan County and Beibei section in Chongqing City,Sichuan Basin. Most of the samples preserve the initial carbon isotopic composition of seawater,but the original signal in the second and fourth Members of Jialingjiang Formation is much more poorly preserved than that of Feixianguan Formation and first and third Members of Jialingjiang Formation. Based on the principle that the oxygen isotope is more sensitive to alternation during the diagenetic process,the relationship between δ¹³C and δ¹⁸O was analyzed,and 200 samples with the δ¹⁸O <-7.5‰ were selected to construct the carbon isotopic evolution curve of the Early Triassic. This isotopic evolution curve shows finely comparable patterns with the coeval curve originating from Guizhou Province. The curve presents larger fluctuations in δ¹³C value of Early Triassic seawater. There are two complete ascending and descending cycles. The cycle 1 consists of Feixianguan Formation,and the first Member of Jialingjiang Formation;while the cycle 2 consists of the second and third Members and part of the fourth Member of Jialingjiang Formation,as well as several sub-cycles. According to the pattern of the curve,the lithostratigraphic unit is correlated with chronostratigraphic unit from the coeval curve of Guizhou Province originating from literatures,and further shows that the Feixianguan Formation is in accordance with the Induan Stage,the first Member of Jialingjiang Formation is corresponding to the Smithian substage,the second and third Members and part of the fourth Member of Jialingjiang Formation would be correlated to Spathian substage. Thus,the green-bean rock,as the boundary of Middle and Lower Triassic,is probably distributed in the Middle Triassic. The fluctuations of Early Triassic carbon isotopic curve,both in frequency and amplitude,would result from the perturbations of ecologic environments. The thriving of bacteria and algae in ocean ecosystems results in high burial efficiency of organic carbon and positive excursion of δ¹³C value. The negative excursion of δ¹³C might be the consequences of the hydrates methane release. The carbon isotopic evolution shows the tendency of commonly higher δ¹³C value in dolomite beds than in limestone beds,suggesting the interrelation among activity of microorganism,formation of dolomite and elevation of δ¹³C of seawater. The formation of dolomites in the Early Triassic,especially in the second Member of Jialingjiang Formation,might be originated from activity of microorganism,also as the main source for organic carbon burial. The hydrocarbon in dolomites of the second Member of Jialingjiang Formation is characterized by “in situ reservoir” to some degrees.

In the twenty-first century,with the rapid development of the internet,database and GIS techniques,the palaeogeographical research and the making of palaeogeographic maps also face new opportunities and challenges,gradually transferring from qualitative to quantitative,from single factor or single discipline to integrated. Comparing with traditional qualitative and manual palaeogeographic maps,the new-generation maps,which represent the major direction of palaeogeographic mapping,cover broader range of subjects,involve much larger dataset,provide more precisions,and support the integration of results of quantitative research. The huge data resources of stratigraphy and palaeontology in the Geobiodiversity Database(GBDB),as well as the section-based data structure,make the GBDB most suitable as an open platform for carrying out palaeogeographic research and mapping.We collect a comprehensive dataset of hundreds of sections from South China through the GBDB platform. All the data were standardized and verified by stratigraphic and palaeontolotical experts. The verified dataset was then used to create the late Katian(Late Ordovician)palaeogeographic map of South China with GIS technique. The map shows that,during the late Katian of the Late Ordovician,the Yangtze Platform was mostly deposited by the black shales of the Wufeng Formation,while the other areas,such as the northwestern or southwestern margins of the Yangtze Platform,southern and central Hunan Province,and the southeastern Lower Yangtze Platform received sediments of other lithofacies. Most areas in the south part of South China and the central Sichuan Province were uplifted above the sea level and lacked of sediments of this period. Overall,South China showed a distinct palaeogeographic pattern of a platform surrounded on three sides by oldlands during the late Katian.