Quantitative geochemical reconstruction of Eocene paleoenvironment in Fushun Basin,northeast China

The quantitative estimation of key parameters of paleotemperature and paleoprecipitation is crucial for paleoclimate reconstruction.Geochemical data from mod-ern sediments are highly consistent with climate data,and their relationship can provide an important reference for the quantitative reconstruction of the paleoclimate.In this study,detailed inorganic geochemical analysis was carried out using high-precision sampling of the Paleogene(LFD-1 well)Guchengzi,Jijuntun and Xiloutian Formations in the Fushun Basin located in the mid-latitudes of the Northern Hemisphere.The Eocene Guchengzi Formation(54.51–47.8 Ma)and Jijuntun Formation(47.8–41.2 Ma)in the Fushun Basin were found to have been deposited under a humid climate.The lower(41.2–40.1 Ma)and upper(40.1–37.8 Ma)parts of the Xiloutian Formation were character-ized by semiarid and semihumid–semiarid climates,respec-tively,which is very similar to the paleoclimatic information reflected by organic carbon isotopes.The Eocene Thermal Maximum 2(ETM2,~53.7 Ma),Early Eocene Climatic Optimum(EECO,~53.1–46.5 Ma),Eocene Thermal Maxi-mum 3(ETM 3,~52.8 Ma),and Middle Eocene Climatic Optimum(MECO,~40.7–40.1 Ma)events significantly enhanced chemical weathering during these periods.The rapid increase in pCO_(2)concentration leads to an increase in temperature,precipitation,and surface runoff,exhibiting strong chemical weathering.The mean annual temperature(MATa)and mean annual precipitation(MAPa,MAPb,and MAPc)were estimated using parameters,such as the corrosion index without potassium(CIA-K),CaO/Al_(2)O_(3),and(Na_(2)O+K_(2)O)/Al_(2)O_(3).Comparing MAPa,MAPb,and MAPc with the MAP estimated using pollen data,MAPa and MAPb were found to be more sensitive to the climate during high precipitation periods(precipitation>1000 mm,Guchengzi Formation),and the recovered average precipi-tation was similar to MAP.In contrast,MAPc was more sensitive to the climate during low precipitation periods(precipitation<1000 mm,Jijuntun,and Xiloutian Forma-tions),with higher accuracy.To fully consider the influence of soluble inorganic salts Ca^(2+)and Na^(+),multivariate linear equations of CIA-K and CaO/Al_(2)O_(3)with CIA,and CIA-K and CaO/Al_(2)O_(3)with MAP were constructed,namely MAPd and MAPe.The results show that MAPe has the highest per-formance and can be effectively used to estimate the change of paleoprecipitation in Northeast Asia.

The Sword of Damocles behind the Curtain of the Earth’s Global Warming: A Review

The “mainstream” climatology (MSC)—i.e. which includes the Intergovernmental Panel on Climate Change (IPCC) community—considers the present day massive release of greenhouse gases into the atmosphere as the main cause of the current global warming trend. The main inference from this stance is that the increase in temperature must occur after the release of greenhouse gases originating from the anthropic activities. However, no scientific evidence has been provided for this basic notion. Earth paleoclimatic records document the antecedence of temperature over CO2 levels. For the past 65 Ma, the temperature parameter has controlled the subsequent increase in CO2. This includes the three rapid aberrant shifts and extreme climate transients at 55 Ma, 34 Ma, and 23 Ma REF _Ref159913672 \r \h \* MERGEFORMAT [1]. The simple fact of their existence points to the potential for highly nonlinear responses in climate forcing. Whatever these shifts and transients are, CO2 remains a second order parameter in their evolution through time. Confronted with the past, a suitable response must therefore be given to the unresolved question of whether the CO2 trends precede the temperature trends in the current period, or not. The assertion that the current global warming is anthropogenic in origin implicitly presupposes a change of paradigm, with the consequence (the increase in CO2 levels) that occurred in Earth’s past being positioned as the cause of the warming for its present day climatic evolution. The compulsory assumption regarding the antecedence of CO2 levels over the temperature trends is associated with the haziness of the methodological framework—i.e. the paradigm—and tightens the research fields on the likely origins of global warming. The possible involvement of an “aberrant” natural event, hidden behind the massive release of greenhouse gases, has not been considered by the MSC.

Sedimentological Study of Alluvial Deposits on the Congolese Coast: Highlighting the Erosive Character of the Holocene Wet Climatic Phases

A granulometric, mineralogical, morphoscopic and exoscopic study and Rock-Eval analysis carried out on samples taken in the Loango Bay and at Kivesso on the Congolese coast have made it possible to highlight the highly erosive character of the well-documented wet phases ca 9000 - 3000 years B.P. and ca 320 B.P. in the sub-region. Supported by carbon-14 dating, total organic carbon analyses highlight two major phases of peat deposit emplacement. The first, ca. 7000 years B.P., corresponds to the beginning of the deposition of the yellow formation in the entire Loango Bay;the second, ca. 320 years B.P., is contemporary with the deposition of peat in the Kivesso sector. The granulometric analysis of the sediments shows that they are essentially sandy-clay and very poor in silt, alternating with beds of silty clay sometimes rich in organic matter. These sands have a predominant mode of 0.200 mm and an average varying between 0.150 and 0.300 mm. They constitute the flood phase of the carrier current. They are associated with a population of mode 0.125 mm sometimes 0.050 mm with an average varying between 0.100 mm and 0.126 mm which corresponds to the settling phase. Morphoscopic examination showed several varieties of quartz that argue for a source of supply close to the depositional sites.

Latest Neogene Paleoclimate Variation in Yunnan,Southwest China,Revealed by Fossil Leaf Physiognomy

Yunnan Province,located in the southeastern margin of the Tibetan Plateau,can provide important information on how climate change was influenced by global cooling.However,its variation patterns in temperature and precipitation during the latest Neogene are not well-understood.Based on the 357 specimens assigned to 31 morphotypes of plant fossils from the upper Pliocene Ciying Formation in Yiliang County,Yunnan Province,Southwest China,paleoclimate was estimated by Leaf Margin Analysis and Climate Leaf Analysis Multivariate Program.Compared to the present climate,the mean annual temperature and coldest month temperature have not changed significantly since the late Pliocene,whereas the warmest month temperature has decreased significantly.All precipitation-related parameters have decreased,particularly winter precipitation.Combined with the climatic data of the same period in other areas of Yunnan,the western and eastern Yunnan has shown a similar pattern in temperature variation since the late Pliocene except for central Yunnan;whereas the variation in precipitation does not follow a common law except for a consistent decrease in winter precipitation.Our study reinforced the fact that under the background of global cooling and intensified monsoon systems,different areas of Yunnan exhibit different climatic responses to these changes because of their topographic heterogeneities.

Middle Eocene terrestrial paleoweathering and climate evolution in the midlatitude Bohai Bay Basin of eastern China

The middle Eocene climatic optimum(MECO,ca.-42 Ma)is a key time period for understanding Cenozoic cooling of the global climate.Still,midlatitude terrestrial records of climate evolution during MEcO epoch are rare.In this study,continuous high-resolution record of shale sediments in mid-Eocene Shahejie Formation(MES shales)in the Bohai Bay Basin were performed with major-element and wavelet analysis.The midlatitude paleoweathering and paleoclimatic evolution during MEcO epoch were analyzed in this study.The MES shales experienced weak-moderate paleoweathering under a subtropical monsoon paleoclimate with mean annual temperature of 8.3-12.9℃ and mean annual precipitation of 685-1100 mm/yr.The MES shales record a mixed provenance involving intermediate igneous rocks,and low compositional maturity.The nutrient-rich environment led to enrichment in organic matter in the MES shales.Wavelet analysis revealed good periodicity about the paleoclimate and weathering during MECO epoch.In the stage I of MES shales depositional process,the paleolake was high in nutrients,and the MES shales experienced high chemical weathering due to a relatively warmer and more humid climate.In contrast,the climate in stage II was relatively cold and dry,and the maturity of the MES shales was relatively high during this stage,suggesting a relatively stable tectonic background.This work provides more terrestrial records of MEco epoch for midlatitude region,and is benefit for better understanding of the palaeoenvironment when MES shales formed.The implication of organic matters enrichment in this study is meaningful for the shale oil/gas exploration in Nanpu Sag.

Coryphoid palms from the K-Pg boundary of central India and their biogeographical implications:Evidence from megafossil remains

Ten palm leaf impressions are documented from the latest Maastrichtian(late Cretaceous) to early Danian(earliest Paleocene) sediments(K-Pg,c.66-64 Ma) of the Mandla Lobe of the Deccan Intertrappean Beds,Madhya Pradesh,central India.The palmate leaf shape along with a definite wellpreserved costa support their placement in the subfamily Coryphoideae of the family Arecaceae.We place all recovered palm leaf specimens in the fossil genus Sabalites,report seven species of coryphoid palms and describe two new species namely,Sabalities umariaensis sp.nov.and Sabalites ghughuaensis sp.nov.The fossils indicate that coryphoid palms were highly diverse in central India by the latest Cretaceous.These and earlier reported coryphoid palm fossils from the same locality indicate that they experienced a warm and humid tropical environment during the time of deposition.These discoveries confirm the presence of a diversity of Coryphoideae in Gondwana prior to the India-Eurasia collision and provide information about coryphoid biogeographical history over geological time.Based on megafossil remains,we trace coryphoid palm migration pathways from India to mainland Southeast(SE) Asia and other parts of Asia after the docking of the Indian subcontinent with Eurasia early in the Paleogene.

Geochemistry of the Aptian bituminous limestones in Gümuü?hane area,Eastern Black Sea region:new insight into paleogeography and paleoclimate conditions

Aptian is characterized by widespread deposition of organic-rich sediment.The Aptian bitumen limestone horizon,which is thin decimetre-thick sequences,locally crops out in the Kircaova area,Eastern Black Sea Region(Eastern Pontides).They are well correlated with Aptian bitumen limestone in the other Tethys Reams.They are proposed as episodes of increased organic matter.However,background factors controlling organic matter enrichment are poorly known.In this study,we present new inorganic geochemistry,including trace elements,rare earth elements(REE),redox-sensitive elements(RSE),stable-isotopes(δ~(18)O andδ~(13)C),and total organic carbon(TOC).We integrated new geochemical data with existing stratigraphy,paleontology,and organic chemistry data to provide new insight into the depositional environment and paleoclimate conditions during Aptian.The lacustrine bitumen limestone(LBL)samples have variedδ~(13)C(ave.-1.45‰)andδ~(18)O(ave.-4.50‰).They possess distinct REE patterns,with an average of REE(ave.14.45 ppm)and Y/Ho(ave.35)ratios.In addition,they have variable Nd/YbN(0.28-0.81;ave.0.56)and Ce/Ce*(0.68-0.97;ave.0.86),and relatively high Eu^(*)/Eu(1.23-1.53;ave.1.35).They display seawater signatures with reduced oxygen conditions.The enrichment in RSE(Mo,Cu,Ni,and Zn)and the low Mo/TOC(0.70-3.69;ave.2.41)support a certain degree of water restriction.The high Sr/Ba,Sr/Cu,Ga/Rb,and K/Al records of the LBL facies suggest hot house climatic conditions.The sedimentary environment was probably an isolated basin that is transformed from the marine basin.In addition to depositional conditions,the regional parameters such as the climate,increased run-off period,nutrient levels,alkalinity level,and dominant carbonate producers favored the enrichment in organic matter of LBL facies.Thus,extreme greenhouse palaeoclimate conditions have an important role in organic matter enrichment in the isolated basin.Our results are conformable with the published data from marine,semi-restricted basin,and lacustrine settings in the different parts of the Tethys margin.Thus,this approach provides the first insight into the Aptian greenhouse paleo-climate conditions of the Eastern Black Sea Region,NE Turkey.

The paleoclimatic environment reconstruction of Lop Nur in NW China in UAV spectroscopy

The change in the ecological environment in the arid core area is a critical issue in the context of global warming.To study the paleoclimate evolution,precise identification of minerals deposited in Asia’s arid hinterland,Lop Nur Salt Lake,NW China was conducted.The hyperspectral data of the salt crust was sampled to identify the species and content of sedimentary minerals,and the multispectral photos were used to reconstruct the salt crust morphology using the unmanned aerial vehicles platform.The SUnSAL(sparse unmixing by variable splitting and augmented Lagrangian)method was employed to inverse the sedimentary mineral components along the shoreline.The heterogeneity of salt and clay minerals in bright and dark ear-shaped strips was evaluated.The paleoclimatic environment associated with salt lake extinction was reconstructed by analyzing paleoclimate records of sediments,spectral reflectance and morphology of the salt crust.Results show that:(1)the variations in the micro-geomorphology of the salt crust are obviously the reason for the formation of bright and dark ear-shaped strips and the differences in the species and relative content of the sedimentary minerals are the microscopic reason.The high ratio of sedimentary salt minerals to clay minerals(RS/C)contributes to the high reflectivity,and the salt crust presents a bright texture.The low RS/C results in the low reflectivity,salt crust presents a dark texture;(2)the bright and dark ear-shaped strips represent warm-arid and cold-humid climates.The shape of the Lop Nur Lake shoreline evolved due to alternating warm-dry and cold-humid paleoclimate changes.

Leachate Lithium Characteristics of Loess-paleosol Sequences on the Chinese Loess Plateau and their Paleoclimatic Significance

The geochemical components of the leachate from loess-paleosol deposits can provide information about climaterelated post-depositional processes.For example,leachate lithium([Li]_(leachate))is a potential paleoclimate proxy because lithium is a typical lithophile element that is readily adsorbed by clay minerals during weathering and pedogenesis,and thus stratigraphic variations in[Li]leachatecan reflect these processes.We investigated the[Li]leachatevalues of two loess-paleosols profiles(the Luochuan and Weinan sections),on a north-south climatic gradient on the Chinese Loess Plateau.Independent paleoclimate information was provided by measurements of magnetic susceptibility,grain size,Rb/Sr ratios,and clay mineral content.During the last glacial-interglacial period,[Li]leachateincreased from 0.39 to 1.97μg/g at Luochuan and from 0.67 to 2.45μg/g at Weinan,mainly due to increasing pedogenesis.Based on these results we developed a conceptual model to explain the variations in[Li]leachate,Li^(+)within loess layers is mainly derived from dust input and the decomposition of primary minerals,influenced by the East Asian winter monsoon,while in paleosol layers Li is mainly derived from clay mineral adsorption during pedogenic processes,influenced by the East Asian summer monsoon.

Late Quaternary fluvial terrace formation in the Luan River drainage basin,north China and its possible linkages with climate change and tectonic activation

The Luan River is the most important water system in north-eastern Hebei Province,China and is located in the transitional zone of the Eastern Yan Mountains,North China Plain and Songliao Plain.The well-developed river terraces of its tributary,the Yixun River,provide excellent information for studying neotectonics and climate change.There are seven terraces in the lower reaches of the Yixun River,numbered T7-T1.The optically stimulated luminescence dating results of 23 samples show that terraces T7-T2 formed at 111.36±5.83 ka,78.20±4.45 ka,65.29±4.15 ka,56.44±3.07 ka,40.08±2.66 ka,and 13.14±0.76 ka,respectively.A comparison with the oxygen isotope curves of deep-sea sediments reveals that the sediment formation of each terrace corresponded to cold periods of marine isotope stages MIS 4 and MIS 2 and the relatively cold periods of MIS 5e,MIS 3,and MIS 1.Since the Late Pleistocene,the incision rate of the Yixun River has ranged from 0.371-1.740 mm/a.During the formation of T7-T6,T5-T4,T4-T3,and T3-T2,the incision rate was low.However,in the two stages during which T6-T5 and T2-T1 formed(13.14±0.76 ka to 0.58±0.08 ka and 10.79±0.64 ka to 0.16±0.01 ka),these rates reached 1.554 mm/a and 1.592-1.740 mm/a,respectively.At approximately 30 ka,the activity of the Langying Fault increased,leading to footwall uplift.The river gathered in the north of Langying to form the ancient Erdaowan Lake,which resulted in the drying of the river in the lower reaches of the Yixun River during the last glacial maximum without forming river deposits.In the Early Holocene,headward erosion in the lower reaches of the Yixun River was enhanced,which resulted in the disappearance of the lake,and incised meandering formed due to increased neotectonism.Based on the analyses of river incision and the formation of ancient lakes and incised meandering,it was inferred that there have been three periods of strong tectonism in the river basin since the Late Pleistocene.

Mineralogy and element geochemistry of the Sohnari rocks of Early Eocene Laki Formation in the Southern Indus Basin,Pakistan:Implications for paleoclimate,paleoweathering and paleoredox conditions

The Sohnari Member of the Early Eocene Laki Formation is massively deposited in the Southern Indus Basin of Pakistan and is considered a potential source rock to generate hydrocarbons.However,the detailed paleoclimatic,paleoweathering,and depositional conditions of the Sohnari Member have not been studied earlier.This research mainly discusses the detailed mineralogical(bulk and clay)and elemental geochemistry of the Laki Formation from two outcrop sections(Jhimpir and Lakhra)in the Southern Indus Basin,Pakistan.The bulk minerals,including quartz(low),hematite,calcite,halite,gypsum,and clay minerals such as kaolinite,chlorite,smectite and illite have been discussed here.These results demonstrate the paleo-environment of studied area was arid with enhanced saline and weak to strong oxidizing depositional conditions.The chemical index of alteration(CIA)values in Jhimpir and Lakhra sections are in the ranges of 41.30-97.93 and 22.30-96.19,respectively,indicating that the Sohnari sediments experienced weak to intense chemical weathering in the source area.The interpretation of the A-CN-K ternary diagram is consistent with the clay mineral contents in the studied sediments,which is characterized by the predominance of kaolinite,gibbsite and chlorite,demonstrating the weak to strong weathering state under warm and humid climatic conditions.The chemical indices such as Sr/Ba,δU,V/Cr,Ni/Co,and Cu/Zn,U/Th and Ba/Ga show that Sohnari rocks of Early Eocene Laki Formation underwent strong evaporation,oxic water column with warm to humid and minor contact of cold climatic conditions.Based on our present data,it can be concluded that the sediments of Sohnari Member of Laki Formation from Jhimpir and Lakhra areas of Southern Indus Basin in Pakistan are related to Indio-Eurasian collision and came from the Indian shield rocks that were deposited in a brackish water body with a minor contact of the freshwater oxidizing paleo-environment depositional conditions.

Study on Geological Genesis and Sedimentary Model of Complex Low Resistivity Reservoir in Offshore Oilfield — A Case of NgIII Formation of X Oilfield in Bohai Sea

In order to study the micro genetic mechanism and main geological controlling factors of low resistivity reservoir in NgIII formation of X oilfield in Bohai sea in China, the clay mineral composition, irreducible water saturation, salinity and conductive minerals of low resistivity reservoir were studied by using the data of core, cast thin section and analysis, and compared with normal resistivity reservoir. At the same time, the control effect of sedimentary environment on low resistivity reservoir was discussed. The results show that the additional conductivity of high bound water content and high montmorillonite content in the reservoir together leads to the significant reduction of reservoir resistivity, which is the main microscopic cause of the formation of low resistance, and is mainly controlled by the sedimentary background such as paleoclimate and sedimentary cycle. During the deposition period of NgIII formation, the paleoclimate was dry and cold, and it was at the end of the water advance of the medium-term sedimentary cycle. The hydrodynamic force of the river channel was weak, the carrying capacity of the riverbed was weak, and the river channel swayed frequently, resulting in fine lithologic particle size, high shale content and complex pore structure of the reservoir, resulting in significant reduction of reservoir resistance. The research conclusion would have strong guiding significance for the development of low resistivity reservoirs in this area.

Authigenic titanite in weathered basalts: Implications for paleoatmospheric reconstructions

The stability of titanite is sensitive to temperature and partial pressure of CO2.The finding of authigenic titanite grains in weathering regolith formed on Parana basalts,Brazil,under tropical climatic conditions,reveals the thermodynamically-driven conversion from calcite to titanite at elevated ambient temperatures.Being unusual nowadays,this phase transition provides important implications for the understanding of silicate weathering in earlier geological epochs.Two types of secondary titanites were identified in the weathering profile of the study area.The tiny grains of 10 μm are forming in the microscopic voids in the rock.Also,large fractures filled with Fe-rich clay minerals contain bigger specimens of up to 170μm.The titanites of second type often coexist with chalcedony and barite.No carbonate minerals were found in the weathering profile.Weathering sphene can be discriminated from other titanite types by its strong positive Eu anomaly,increased Al2 O3 content and low content of trace elements.Its specific chemical composition and reactive transport modeling link this secondary mineral with dissolution of plagioclase.The titanite precipitation is controlled by slow diffusion in poorly-aerated,highly-alkaline pore fluids.The subaerial weathering of basaltic rocks provides a significant reservoir for atmospheric CO2.However,the deposition of carbonate minerals is thermodynamically avoided at the stability field of titanite.We demonstrate a complex feedback between CO2 and soil carbonates.The rise in pCO2 triggers the precipitation of calcite in the weathering regolith,but the greenhouse effect increasing the temperature can cease carbonate deposition.Secondary titanites were found in several paleosols and at least a part of them can be of weathering origin.

A 3600 YEARS PALEOCLIMATIC CHANGE INFERRED FROM ORGANIC δ^(13)C AND TOC/TN OF THE GUCHENG LAKE SEDIMENTS, SOUTHEAST CHINA

A 6.2 m thick core of Gucheng Lake sediment provided a 3600 years record of climate change. The contents of the TOC in the core changed from 2.63% to 8.48%, and the δ13C values of organic matter were from - 21.54% to - 27.3%. The TOC/TN ratios indicated that the organic materials in sediments were from lake plankton and land-derived plants.The 2.9-22 m core interval with high TOC/TN ratios, low δ13C values and low contents of TOC indicated a cold climate Stage. The 6.2-5.5 m and 0.4-0.1 m intervals were characterized by low TOC/TN ratios, highδ13C values and high contents of TOC and reflcted temperate climate stages.

Primary Study on Quantitative Reconstruction of Middle-Late Eocene Climate in Jianghan Basin

This paper reports our primary effort in the quantitative reconstruction of paleoclimate based on the thrine in phytoecology of the affinity parent plants in the stratigraphic pollen records. The Eocene pollen data come from our former study on the Mingjia borehole 1 in the Jianghan basin. The fluctuating trend in the parameter curve of climate shows that the climate in the Middle Eocene in the Jianghan basin was more or less comparable with that of the present 22°-26°N, characteristic of a humid, semi humid central southern subtropical climate. The annual temperature at that time dropped by 1 ℃-4 ℃ in the Late Eocene, approximately equal to that of the present 23°-28°N of northern central subtropical climate. However, the climate composite at that time, characterized by higher temperature, small annual range and big fluctuation in precipitation, was quite different from the present one. The average temperature in January in the Middle Eocene, higher than that of today, ranged between 5 ℃ and 9 ℃, indicating that no effect of winter monsoon occurred in the Middle Eocene, though such an effect may have occurred occasionally in the Late Eocene. Major temperature decline is recognized at the depth of 2 100 m in the borehole, as was indicated by the decline in average January temperature, the increase in annual range, and the increase in the deciduous broad leaved types of trees in the spore pollen assemblage. The sharp fluctuation in the annual precipitation, usually raging from 300 to 1 700 mm, was favorable for the migration and accumulation of salty deposit. When the precipitation was lower than 1 000 mm, ephemera shrub increased at the same depth as that of the salty deposit. It is, therefore, deduced that the formation of the salty deposit was attributed mainly to the dry and hot environment in the high mountains and deep basins. The small annual precipitation and the intense fluctuation are favorable for the sustainable accumulation of the salts, which is different from the present salty accumulation in the Northwest China.

Modelling the January and July Climate of 9000 Years before Present

ＭｏｄｅｌｌｉｎｇｔｈｅＪａｎｕａｒｙａｎｄＪｕｌｙＣｌｉｍａｔｅｏｆ９０００ＹｅａｒｓｂｅｆｏｒｅＰｒｅｓｅｎｔ￥ＷａｎｇＨｕｉｊｕｎ（王会军）（ＬＡＳＧ，ＩｎｓｔｉｔｕｔｅｏｆＡｔｍｏｓｐｈｅｒｉｃＰｈｙｓｉｃｓ，ＣｈｉｎｅｓｅＡｃａｄｅｍｙｏｆ...

Shuram-Wonoka carbon isotope excursion:Ediacaran revolution in the world ocean's meridional overturning circulation

The late Ediacaran Shuram-Wonoka excursion, with δ^(13)C_(carb) values as low as-12‰(PDB) in marineshelf deposits and spanning up to 10 Myr, is the deepest and most protracted δ^(13)C_(carb) negative anomaly recognised in Earth history. The excursion formed on at least four continents in low(≤32°) palaeolatitudes, and in China is associated with a major phosphogenic event. Global and intrabasinal correlation, magnetostratigraphy, isotope conglomerate tests and further geochemical data are consistent with a primary or syn-depositional origin for the excursion. Continental-margin phosphorites are generated by oceanic upwelling driven by surface winds, and δ^(13)C_(carb) negative anomalies are explicable by oceanic upwelling of 13 C-depleted deep oceanic waters, arguing that a feature common to these exceptional Ediacaran events was unprecedented perturbation of the world ocean. These events occurred during the transition from an alien Proterozoic world marked by low-palaeolatitude glaciation near sea level and strong seasonality to the familiar Phanerozoic Earth with circum-polar glaciation and temperate climate, suggesting that the Shuram-Wonoka excursion is related to this profound change in Earth's climate system. Of various hypotheses for Proterozoic low-palaeolatitude glaciation, only the high obliquity(>54°) hypothesis, which posits secular decrease in obliquity to near the present-day value(23.5°) during the Ediacaran, predicts an unparalleled revolution in the Ediacaran world ocean. The obliquity controls the sense of the world ocean's meridional overturning circulation, which today is driven by the sinking of cold, dense water at the poles and upwelling driven by zonal surface winds.When the decreasing obliquity passed the critical value of 54° during the Ediacaran the meridional temperature gradient reversed, with the equator becoming warmer than the poles and Hadley lowlatitude(<30°-35°) atmospheric zonal circulation reversing. This reversal of the temperature gradient is unique to the Ediacaran Period and caused reversal of the oceanic meridional overturning circulation,with upwelling of anoxic, 13 C-depleted deep oceanic waters producing a deeply negative and protractedδ^(13)C_(carb) signature on late Ediacaran marine-shelf deposits.

Deep Continental Scientific Drilling Engineering Project in Songliao Basin:progress in Earth Science researcha

The Songke No.2 well (eastern hole)(referred to as Well SK-2),one of the "two wells and four holes"of the Deep Continental Scientific Drilling Engineering Project in the Songliao Basin,is in Anda City, Heilongjiang Province,and was officially completed on May 26,2018.Tlie scientific goals of Well SK-2 cover four aspects:paleoclimate research,resource and energy exploration,primary geological research, and development of deep earth exploration techniques.Since the official commencement of drilling in 2014,the Well SK-2 scientific drilling engineering team has organized and implemented drilling for coring,in situ logging,chemical analysis of core elements,and deep structural exploration around the well.Currently,the following preliminary scientific research progress has been made:4334.81 m in situ core data has been obtained;the centimeter-level high-resolution characterization of the most complete and continuous Cretaceous continental strata ever unearthed has been completed,and the standard profile of continental strata has been initially established;the unconventional natural gas resources and basin-type hot dry rocks in the deep Songliao Basin were found to have good prospects for exploration and development;the climatic evolutionary history of the Cretaceous continental strata was rebuilt for the first time,covering hundreds of thousands to millions of years,and the major events of Cretaceous climate fluctuations have been discovered;all these reveal strong evidence for the subduction and aggregation of paleo-ocean plates,providing a theoretical basis for the re-recognition of the genesis of the Songliao Basin and for deep earth oil and gas exploration.The implementation of the Deep Continental Scientific Drilling Engineering Project in the Songliao Basin is of great significance for exploring the mysteries of the Earth and solving major problems such as those related to the deep energy environment.It is a solid step along the road of "going deep into the Earth".

COMPOSITIONS OF δ^(18)O AND δ^(13)C IN VARIOUS CARBONATES OF CORE RM IN THE ZOIGê BASIN AND CLIMATIC SIGNIFICANCE

The hole RM, the deepest one fully obtained core in the Qinghai-Xizang Plateau, situated in the depositional center of the Zoire Basin (33°57′N; 102°21′E) in the northeastern QinghaiXizang Plateau with a depth of 310.46 m. From 14C dating and Paleomagnetic stratigraphic study,the core RM can date back to 900 ha B.P.. In this paper we analyzed the compositions of δ18O and δ13C in various carbonates can date (snail, obstrode, chemical Cabonate) in core RM and discussed preferably the paleoclimatic record by the proxies of δ18O and δ13C Of chemical carbonate (authicalbonate) from core RM in the past 140 ka. The results showed that the values of δ18O in various carbonates are generally identical, and the values of δ13C in it are inconsistent, while there exist better relativity. The studies also demonstrated that there was a negative correlation between δ18O and δ13C of authicabonate in core RM in the past 140 ka, showing that the changes of δ18O values were mainly relative to the water temperature. According to above, the climatic evolutionary sequence were rebuilt in the past 140 ka in the region.

Paleoglacial and paleoclimate reconstructions during the global Last Glacial Maximum in the Longriba area, eastern Tibetan Plateau

Owing to the remoteness of the Longriba area and the lack of dating records,it is extremely challenging to reconstruct the chronology and extent of the paleoglaciers in this area.In this paper,we combined limited observational data with automated modelling for paleoglacial reconstructions.We first identified a broadly distributed paleoglacier from satellite imagery and field investigation based on the sediment-landform assemblage principle and dated it to 23.1±1.4~19.5±1.2 ka by ^(10)Be exposure dating,corresponding to the global Last Glacial Maximum(gLGM).Then,we reconstructed the extent and ice surface of 171 paleoglaciers formed during the similar period based on geomorphological evidence and‘ice surface profile’modelling.The results showed that the paleoglacial coverage was 426.5 km2,with an ice volume of 38.1 km^(3),in the Longriba area.The reconstructed equilibrium line altitudes(ELAs)based on modelled ice surfaces yielded an average of 4245±66 m above sea level(asl),~725±73 m lower than the present ELA(4970±29 m asl).The temperature was~5.51-6.68℃lower,and the precipitation was~30-34%less in Longriba,during the gLGM compared to the present day.This glacial advance was mainly driven by colder climate that was synchronous with Northern Hemisphere cooling events.