δ^(13)C_(org) perturbations preserved by the interglacial Datangpo Formation in South China with implications for stratigraphic correlation and carbon cycle

Palaeoclimatic and palaeoenvironmental reconstructions of the Cryogenian Period have attracted attention in relation to the debated“Snowball Earth”hypothesis and the early evolution of metazoan life.The carbon cycle and redox conditions of the Sturtian-Marinoan non-glacial interval have been subjected to much controversy in the past decades because of the lack of a high-resolution stratigraphic correlation scheme.As one of the typical Sturtian-Marinoan interglacial deposits,the Datangpo Formation was widely distributed in South China with shales continuously deposited.The previous zircon dating data of the Datangpo Formation provide important ages for global constrain of the Sturtian-Marinoan non-glacial interval.Here we present a high-resolution straitigraphic study of the organic carbon isotopes of the Datangpo Formation from a drill core section in northern Guizhou Province.Based on measured episodicδ^(13)C_(org) perturbations,three positive shifts and three negative excursions are identified.Aδ^(13)C_(org)-based chemostratigraphic correlation scheme is proposed herein that works well for the Datangpo Formation regionally.Meanwhile,theδ^(13)C_(org) vertical gradients changed dynamically throughout the formation.This discovery implies that a significant ocean circulation overturn might have occurred in the upper Datangpo Formation,coinciding with the potential oxygenation.

A Multi-cycle Climatic Fluctuation Record of the Last Interglacial Period:Typical Stratigraphic Section in the Salawusu River Valley on the Ordos Plateau,China

The Last Interglacial Period strata in the Milanggouwan section in the Salawusu River valley on the Ordos Plateau, China, have 8.5 sedimentary cycles composed alternately of eolian dune sands, fluvio-lacustrine facies and paleosols. Based on comprehensive analyses on the distribution of magnetic susceptibility and CaCO3 and paleo-ecology indicated by fossils in the region, it is considered that the sedimentation cycles resulted from dry-cold and warm-humid climate fluctuations. Magnetic susceptibility values and CaCO3 contents in stratigraphic sectors I, III, V and II, IV basically respectively present peaks and low vales, and the former three can in time correlate with MIS5a, MIS5c and MIS5e successively and the latter two with MIS5b and MIS5d. In addition, some horizons of eolian dune sands and the low vales of their magnetic susceptibility and CaCO3 are also correlated with 6 periods of cooling events indicated by the higher content of foraminifer Neogloboquadrina pachyderma (S.) documented in the V29—191 drill in the North Atlantic and the cold events recorded by δ 18O in the ice cores in GRIP, especially with 9 periods of dust events in Chinese Loess Plateau.

CAS-FGOALS Datasets for the Two Interglacial Epochs of the Holocene and the Last Interglacial in PMIP4

Two versions of the Chinese Academy of Sciences Flexible Global Ocean-Atmosphere-Land System model(CASFGOALS),version f3-L and g3,are used to simulate the two interglacial epochs of the mid-Holocene and the Last Interglacial in phase 4 of the Paleoclimate Modelling Intercomparison Project(PMIP4),which aims to study the impact of changes in orbital parameters on the Earth’s climate.Following the PMIP4 experimental protocols,four simulations for the mid-Holocene and two simulations for the Last Interglacial have been completed,and all the data,including monthly and daily outputs for the atmospheric,oceanic,land and sea-ice components,have been released on the Earth System Grid Federation(ESGF)node.These datasets contribute to PMIP4 and CMIP6(phase 6 of the Coupled Model Intercomparison Project)by providing the variables necessary for the two interglacial periods.In this paper,the basic information of the CAS-FGOALS models and the protocols for the two interglacials are briefly described,and the datasets are validated using proxy records.Results suggest that the CAS-FGOALS models capture the large-scale changes in the climate system in response to changes in solar insolation during the interglacial epochs,including warming in mid-to-high latitudes,changes in the hydrological cycle,the seasonal variation in the extent of sea ice,and the damping of interannual variabilities in the tropical Pacific.Meanwhile,disagreements within and between the models and the proxy data are also presented.These datasets will help the modeling and the proxy data communities with a better understanding of model performance and biases in paleoclimate simulations.

Comparison of Climate and Environment Change of the Last Interglacial Period and Holocene in Beijing Area, China

Research on climate changes between the last interglacial period and Holocene renders a speculation on the tendency of present climate. Fully understanding the nature of the changes will play a significant role in a better understanding of global climate change. This work discussed the climate change of the last interglacial period and Holocene in Beijing area to discover the mechanism of local palaeo-climate change. The palaeo-vegetation of the last interglacial period in Xishan Mountain of Beijing was reconstructed by pollen analysis and thermo-luminescence dating to represent the change of palaeo-climate and palaeo-environment. Palaeo-vegetation indicators demonstrated that the climate change of the last interglacial period included 6 stages and was homologous to that reflected by the records from deep sea depositions and polar ice cores, respectively corresponding to Marine Isotope Stage (MIS) 5e, 5d, 5c, 5b, 5a and the interim from MIS5 to MIS4 from the early to the late. Millennial climate abrupt events occurred in MIS 5e, which had an agreement with the records of GRIP. In addition, a climate warming event appeared in the interim from MIS5 to MIS4 and it also was found in other regions of the world. Compared with the vegetation and environment indicators of Holocene in Beijing area, it was found that the vegetation, climate and environment of the last glacial period were better than those of Holocene. The climate abrupt events not only appeared in the last interglacial period and MIS 5e, but also occurred in Holocene, whose mechanism and pattern were analogical. After analyzing the records of millennial climate abrupt change events from this work, Ice Cores and others, it was concluded that climate was instability in the interglacial period.

Impact of Dust Aerosol on Glacial–Interglacial Climate

The temperature anomaly and dust concentrations recorded from central Antarctic ice core records display a strong negative correlation. The dust concentration recorded from an ice core in central Antarctica is 50-70 times higher during glacial periods than interglacial periods. This study investigated the impact of dust aerosol on glacial-interglacial climate, using a zonal energy balance model and dust concentration data from an Antarctica ice core. Two important effects of dust, the direct radiative effect and dust-albedo feedback, were considered. On the one hand, the direct radiative effect of dust significantly cooled the climate during the glacial period, with cooling during the last glacial maximum being as much as 2.05℃ in Antarctica. On the other hand, dust deposition onto the ice decreased the surface albedo over Antarctica, leading to increased absorption of solar radiation, inducing a positive feedback that warmed the region by as much as about 0.9℃ during the glacial period. However, cooling by the direct dust effect was found to be the controlling effect for the glacial climate and may be the major influence on the strong negative correlation between temperature and dust concentration during glacial periods.

Multiple enrichment mechanisms of organic matter in the Fengcheng Formation of Mahu Sag,Junggar Basin,NW China

Based on core and thin section data,the source rock samples from the Fengcheng Formation in the Mahu Sag of the Junggar Basin were analyzed in terms of zircon SIMS U-Pb geochronology,organic carbon isotopic composition,major and trace element contents,as well as petrology.Two zircon U-Pb ages of(306.0±5.2)Ma and(303.5±3.7)Ma were obtained from the first member of the Fengcheng Formation.Combined with carbon isotopic stratigraphy,it is inferred that the depositional age of the Fengcheng Formation is about 297-306 Ma,spanning the Carboniferous-Permian boundary and corresponding to the interglacial period between C4 and P1 glacial events.Multiple increases in Hg/TOC ratios and altered volcanic ash were found in the shale rocks of the Fengcheng Formation,indicating that multiple phases of volcanic activity occurred during its deposition.An interval with a high B/Ga ratio was found in the middle of the second member of the Fengcheng Formation,associated with the occurrence of evaporite minerals and reedmergnerite,indicating that the high salinity of the water mass was related to hydrothermal activity.Comprehensive analysis suggests that the warm and humid climate during the deposition of Fengcheng Formation is conducive to the growth of organic matter such as algae and bacteria in the lake,and accelerates the continental weathering,driving the input of nutrients.Volcanic activities supply a large amount of nutrients and stimulate primary productivity.The warm climate and high salinity are conducive to water stratification,leading to water anoxia that benefits organic matter preservation.The above factors interact and jointly control the enrichment of organic matter in the Fengcheng Formation of Mahu Sag.

Impacts of Early Pleistocene glacial vicariance among refugial lineages and Mid-Late Pleistocene interglacial dispersal and expansion on forging population genetic structure of the giant clam Tridacna squamosa(Bivalvia:Cardiidae:Tridacninae)across the Red Sea and Indo-West Pacific oceans

This study aims at identifying the microevolutionary processes responsible for the onset of the remarkable phylogeographic structure already recorded for the endangered giant clam Tridacna squamosa across its distribution range.For this purpose,the evolutionary,biogeographic and demographic histories of the species were comprehensively reconstructed in a mitochondrial dataset comprising nearly the whole available published cytochrome c oxidase 1 gene sequences of T.squamosa.Relatively higher level of genetic diversification was unveiled within T.squamosa,in comparison to earlier macro-geographic investigations,whereby five mitochondrial clusters were delineated.The resulting divergent gene pools in the Red Sea,western Indian Ocean,Indo-Malay Archipelago and western Pacific were found to be driven by Early Pleistocene glacial vicariance events among refugial lineages.Accentuated genetic diversification of the species across the Indo-Malay Archipelago was successively triggered by historical dispersal event during the Mid-Pleistocene MIS19c interglacial.This latter historical event might have also enabled genetically distinct giant clams from the Indo-Malay Archipelago to subsequently colonize the western Pacific,accounting for the genetic diversity hotspot detected within this region(comprising three divergent mitochondrial clusters).Late Pleistocene demographic expansion of T.squamosa,during the Last Interglacial period,could have contributed to forging spatial distribution of the so far delineated genetic entities across the Indo-Western Pacific.Overall,being resilient to major climate shifts during the Pleistocene through adaptation and consequent diversification,T.squamosa could be used as a model species to track the impact of climate change on genetic variability and structure of marine species.In particular,the new information,provided in this investigation,may help with understanding and/or predicting the consequences of ongoing global warming on genetic polymorphism of endangered coral reef species among which Tridacna sp.are listed as ecologically important.

Instability characteristics of the East Asian Monsoon recorded by high-resolution loess sections from the last interglacial (MIS5)

The selection of high-resolution loess sections is needed in order to determine the climatic variability of the East Asian Monsoon during the last interglacial. Two sequences of S1 on the eastern and west-ern sides of the Liupan Mountain were both composed of five paleosol layers and four loess layers,indicating that there were five strong summer monsoon events and four strong winter monsoon events in MIS5. This corresponds with other records of the East Asian Monsoon,along with NGRIP and the North Atlantic records,implying that the climate of the Northern Hemisphere was very instable during the last interglacial. Two layers of paleosols and one layer of loess had developed during MIS5a and MIS5c. Compared with MIS5e,the climate in MIS5a and MIS5c fluctuated more intensively on a millen-nial scale,whereas the climate was relatively stable in MIS5e.

An abrupt cooling event early in the last interglacial in the northern South China Sea

The high-resolution quantitative analysis of the planktonic foraminifera and the δ18O records of the section between 96.49– 137.6 mcd at ODP Site 1144 on the continental slope of northern South China Sea reveals an abrupt cooling event of sea surface temperature (SST) during the last interglacial (MIS 5.5, i.e. 5e). The dropping range of the winter SST may come to 7.5°C corresponding to 1.2‰ of the δ18O value of sea surface water. This event is comparable with those discovered in the west Europe and the northern Atlantic Ocean, but expressed in a more intensive way. It is inferred that this event may have been induced by middle- to low-latitude processes rather than by polar ice sheet change. Since the Kuroshio-index speciesPulleniatina obliquiloculata displayed the most distinct change at the event, it may also be related to the paleoceanographic change of the low-latitude area in the western Pacific Ocean. This event can be considered as one of “Younger Dryas-style coolings” and is indicative of climate variability of the last interglacial stage.

Climatic variation during the Last Interglacial Period recorded in the lake carbonate deposit, eastern Qinghai-Xizang Plateau

THE climatic instability was found by the oxygen isotope record in Greenland ice core（Green-land Ice Project（GRIP））during the Last Interglacial Period.It is regarded as greatprogress in research on the past global climatic change.The δ18O record reveals that thereexist two obvious cold events in the Eemian period,equivalent to substage 5e,and they werefurther confirmed by the lake record from Europe.But these shifts are not found in the icecore GISP2 and in the North Atlantic deep-sea sediment,casting doubt on whether

The Marine Redox Change and Nitrogen Cycle in the Early Cryogenian Interglacial Time: Evidence from Nitrogen Isotopes and Mo Contents of the Basal Datangpo Formation, Northeastern Guizhou, South China

Cryogenian Datangpo Formation was deposited during the interglacial time between the Sturtian and Marinoan ice ages. We studied nitrogen isotope compositions and contents of Mo of the black shales from the basal Datangpo Formation in northeastern Guizhou, South China, for an attempt to reconstruct the marine redox change and nitrogen cycle during the interglacial time. Based on lithostratigraphy as well as geochemical profiles, the basal black shales can be divided into four intervals： Interval 1 has the lowest δ^（15）N value（＋5.0‰）; in interval 2, δ^（15）N values vary between ＋6.4‰ and ＋7.4‰（the first peak）; interval 3 records stable values of δ^（15）N around ＋6‰; and interval 4 is characterized by its higher δ^（15）N values, between ＋6.7‰ and ＋7.8‰（the second peak）. The values of enrichment factor of Mo decrease from 56.8 to 2.6 with the ascending stratigraphic trend. It indicated that immediately after the Sturtian glaciations, the marine seawater above the transitional zone between the shelf to slope of the southern margin of the Yangtze Platform was stratified, with shallow seawater being oxic but deep water being sulfidic. Subsequently, high denitrification rates prevailed in expanded suboxic areas in spite of a short emergence of an oxic condition in the surface seawater, and the deep seawaters were still anoxic or even euxinic.

Environmental and rock magnetic studies of rapid fluctuations of Asian summer monsoon during the last interglacial maximum(MIS 5e)

A systematic environmental rock magnetic study of a century-millennial scale loesspaleosol sequence of the last interglacial in the Jiuzhoutai well section, Lanzhou, on the western Loess Plateau demonstrates that Asian summer monsoon experienced fast and large oscillations manifesting as three peaks and two valleys lasling about 1—2 ka. Valley 4 with a central age of 120.5 ka is the most evident, suggesting that summer monsoon was weakened nearly to a level in glaciations. This indicates that summer monsoon has a nature of instability in centurymillennial scale change in the last interglacial.

Palaeomonsoon vicissitudes in eastern desert region of China since last interglacial period

Based on the geological records, the palaeomonsoon in eastern desert region of China is divided into three major evolution stages, i.e. summer monsoon prevailing stage of last interglacial period (130-70kaB.P.), winter monsoon prevailing stage of last glacial period (70-10 kaB.P.), and unstable summer monsoon prevailing stage of postglacial period (10 kaB.P. to present) and further divided into several substages. The conversion between summer monsoon and winter monsoon in the region is dominated by the sudden change process. The north limit of summer monsoon in the region retreated to the north limit of sandy loess zone of the Loess Plateau in the last glacial period from the Mazong Mts.-Ulan Bator of last interglacial period, then it entered Shandan-Yabrai region in the optimum period of the Holocene, and finally it retreated to the present extended line from north piedmont of the Yinshan Mts to Hulun Buir. This shows that the summer monsoon caused by East Asian monsoon circulation tends to be weakened fluctuationally. However, the factors affecting the monsoon vicissitudes are complex, so special attention should be paid to the study of the short-period climatic fluctuations of the Holocene.

A climatic reversal at the last interglacial-last glacial transition recorded in the loess section at Zhaitang, Beijing

A weakly developed paleosol was identified at S1-L1 transition of the loess section of Zhaitang, Beijing. This paleosol may represent a climatic reversal which is associated with the strengthening in summer monsoon and correlated well with the climatic regression event documented in the paleoclimate records from Greenland ice, marine sediments and European pollen at the last interglacial-last glacial transition.

Preliminary study on the summer monsoon climate of Chinese Loess Plateau during the last interglacial period

Research on long-term climatic variation on the Chinese Loess Plateau has demonstrated that loess is mainly the dust deposits transported by the northern wind of the winter monsoon, and that the paleosol accreted by rather slow dust accumulation was closely related to a strengthened summer monsoon. The climate over the Chinese

Eco-environmental changes in the Chinese Loess Plateau during low-eccentricity interglacial Marine Isotope Stage 19

Eco-environmental changes during interglacials with an astronomical background similar to that of the Holocene are potentially helpful for understanding the future climatic evolution.Marine oxygen isotope stage(MIS)19 is similar to the Holocene in astronomical background,both being characterized by a low eccentricity of the Earth’s orbit.However,MIS 19 has attracted research attention only recently and therefore less is known about eco-environmental changes during this interval,especially based on terrestrial records.In the Chinese Loess Plateau(CLP),the S7 paleosol can provide valuable terrestrial paleoclimatic and paleoenvironmental record for MIS 19.Here,high-resolution terrestrial snail records from the L8–L7 strata of the Huining,Xifeng and Luochuan sequences in the CLP were analyzed in order to characterize spatio-temporal changes in climate and eco-environment during MIS 20–18.The results show that in all three sections the late part of MIS 20 was dominated by abundant cold-aridiphilous mollusc species,indicating that cold and dry climatic conditions prevailed across the entire CLP,under the strong influence of the winter monsoon.The mollusc fauna of MIS 19 were dominated by warmth-loving and thermohumidiphilous species that enable the definition of two climatic stages.The early part of MIS 19(~790–778 ka)was marked by warm and humid conditions,as evidenced by high abundances of warmth-loving and thermo-humidiphilous species.This interval was slightly warmer than today and it lasted for^12 kyr.The climate of the later part of MIS 19(~778–761 ka)was more moderate,and increased proportions of cold-aridiphilous and warmth-loving species were recorded.The warmth of this period was similar to that of today,but the climatic fluctuations were stronger.During the early part of MIS 18(~761–745 ka),the Xifeng and Luochuan sections in the eastern CLP still maintained high abundances of warmth-loving and thermo-humidiphilous species,indicating that the moderate climatic conditions during late MIS 19 continued during early MIS 18,lasting for another^15 kyr,and that the influence of the summer monsoon remained strong in the eastern CLP during early MIS 18.However,in the western CLP,cold-aridiphilous species in the Huining section became dominant during early MIS 18,reflecting the prevalence of a cold and dry glacial climate,with the strong influence of the winter monsoon.These findings indicate that a steeper climatic gradient and a pronounced regional environmental difference existed between the eastern and western CLP during the early part of MIS 18.Comparison of our mollusc results with the variation of Earth orbital parameters suggested that climate changes in the CLP during MIS 20–18 were likely controlled mainly by insolation changes forced by the configuration of Earth orbital parameters.The unique orbital configuration during the low eccentricity interglacial-to-glacial transition could have strengthened the East Asian summer monsoon which favored the amelioration of the eco-environment in the CLP,especially in the eastern CLP where the summer monsoon exerted a strong influence.Thus we speculate that,under natural climatic conditions,the climate of the CLP may remain in a warm,humid state for another 30 kyr,although climatic instability and the seasonal differences between winter and summer could strengthen.

Petroleum geological conditions and exploration importance of Proterozoic to Cambrian in China

The discovery of the giant Anyue gas field in Sichuan Basin gives petroleum explorers confidence to find oil and gas in Proterozoic to Cambrian.Based on the reconstruction of tectonic setting and the analysis of major geological events in Mesoproterozoic-Neoproterozoic,the petroleum geological conditions of Proterozoic to Cambrian are discussed in this paper from three aspects,i.e.source rocks,reservoir conditions,and the type and efficiency of play.It is found that lower organisms boomed in the interglacial epoch from Mesoproterozoic-Neoproterozoic to Eopaleozoic when the organic matters concentrated and high quality source rocks formed.Sinian-Cambrian microbial rock and grain-stone banks overlapped with multiple-period constructive digenesis may form large-scale reservoir rocks.However,because of the anoxic event and weak weathering effect in Eopaleozoic-Mesoproterozoic,the reservoirs are generally poor in quality,and only the reservoirs that suffered weathering and leaching may have the opportunity to form dissolution-reconstructed reservoirs.There are large rifts formed during Mesoproterozoic-Neoproterozoic in Huabei Craton,Yangtze Craton,and Tarim Craton in China,and definitely source rocks in the rifts,while whether there are favorite source-reservoir plays depends on circumstance.The existence of Sinian-Cambrian effective play has been proved in Upper Yangtze area.The effectiveness of source-reservoir plays in Huabei area depends on two factors:(1)the effectiveness of secondary play formed by Proterozoic source rock and Paleozoic,Mesozoic,Cenozoic reservoir rocks;(2)the matching between reservoirs formed by reconstruction from Mesoproterozoic-Neoproterozoic to Eopaleozoic and the inner hydrocarbon kitchens with late hydrocarbon generation.As for Tarim Basin,the time of Proterozoic and the original basin should be analyzed before the evaluation of the effective play.To sum up,Proterozoic to Cambrian in the three craton basins in China is a potential exploration formation,which deserves further investigation and research.

Modeling the Past and Current Distribution and Habitat Suitability for Ablepharus grayanus and A. pannonicus(Sauria: Scincidae)

Study of the climate variability in the past and present, and correlating those with changes in the distribution range of species has attracted considerable research interest. The genus Ablepharus consists of 10 recognized species, of which A. bivittatus, A. grayanus and A. pannonicus are documented from Iran. In the present study, we modeled with MaxEnt the potential distribution areas and determined the suitable habitats in past （mid-Holocene [MH], and the Last Interglacial [LIG]） and their current distribution for two species of snake-eyed skinks （A. grayanus and A. pannonicus） separately. Models of the species indicated good fit by the average high area under the curve （AUC） values （A. grayanus = 0.929 4- 0.087 and A. pannonicus = 0.979 4- 0.007）. Precipitation of the driest quarter of the year, mean temperature of the coldest quarter of the year, and precipitation of the driest month variables made important contributions to A. grayanus. Two important climate variables contributed importantly to A. pannonicus; temperature seasonality, and mean temperature of the wettest quarter of the year, and one topographic variable, slope. We conclude that these variables form a natural barrier for species dispersal. The MH and the LGM models indicated a larger suitable area than the current distribution.

A warmer but drier Marine Isotope Stage 11 during the past 650 ka as revealed by the thickest loess on the western Chinese Loess Plateau

Marine Isotope Stage 11（MIS 11; ca. 423-362 ka） is generally considered to be the best analogue for the present interglacial（Holocene）, and investigation of it will improve our understanding of current climate variability and assist in predictions of future climate change. However, many recent studies primarily focus on the structure and duration of MIS 11. Little research has focused on climate warmth and stability recorded in the Chinese loess-paleosol sequences（LPS） during the S4 paleosol formation（equivalent to MIS 11）. On the basis of previous work, this study presents a high-resolution record（ca. 75 a/cm） that spans from MIS 1 to MIS 15, as preserved in the thickest known Jingyuan loess section on the western Chinese Loess Plateau（CLP）. This LPS is almost 165 m thick and was sampled from the upper part of L6 to the modern soil at 2-cm depth intervals. Measurements of magnetic susceptibility, mean grain size and ＆gt;63 μm particle content, carbonate content, total organic carbon, and soil color of samples were made to reconstruct the paleoclimate variation, and a grain-size age model was used to constrain the chronological framework. The primary results show that a generally warm-humid climate dominated the S4 paleosol development, but the climate condition was extremely unstable during the whole of MIS 11. Two obviously different climate regimes controlled the MIS 11 climate variation： the early part of MIS 11 was extremely warm and stable, but the latter part was relatively cool（non-glacial） and unstable. This climate pattern was consistent with records on the central CLP and wavelet analysis suggested that it was forced by the 65°N insolation variability modulated by a quasi-100-ka cycle. In addition, a multi-proxy comparative study on the climate conditions during S0 to S5 paleosol development indicates that the period of S4 development might be the warmest interglacial of the past 650 ka. However, the climate condition during S4 development was not the most humid episode as recorded in Xifeng and Luochuan loess sections on the central CLP. On the contrary, it was drier than both the MIS 15 and the present interglacial on the western CLP, which is somewhat similar to the present climate pattern on the central CLP.

Sea Level Records on Ouvéa Island in New Caledonia

Ouvéa Island in New Caledonia emerges as a new sea level standard. It has excellent morphological records of former sea level positions at interglacial high-stands as well as records of Holocene changes in sea level from a maximum at about +1.5 m via a significant +70 cm level of sub-recent, probably 17th century, age to a stable to falling sea level in present time.