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.

The Combined Effect of Tibetan Plateau Uplift and Glacial-Interglacial Cycles on the Quaternary Evolution of the East Asian Monsoon: Evidence from South China Sea Sediments

The siliciclastic sediments of the uppermost section of 185 mcd （meters composite depth） from ODP Site 1146 on the northern continental slope of the South China Sea （SCS） were partitioned according to their sources using end-member modeling on grain-size data.The goal was to evaluate the evolution of the East Asian monsoon over the past 2 million years.The siliciclastic sediments were described as hybrids of four end-members,EM1,EM2,EM3,and EM4,with modal grain sizes of 8-22 μm,2-8 μm,31-125 μm,and 4-11 μm,respectively.EM1 and EM3 are interpreted as eolian dust and EM2 and EM4 as fluvial mud.The ratio of eolian dust to fluvial mud （（EM1＋EM3）/（EM2＋EM4）） is regarded as an indicator of the East Asian monsoon.The variation in this ratio not only shows periodical oscillations consistent with oxygen isotope stages,but also exhibits a phased increasing trend corresponding with the phased uplifts of the Tibetan Plateau,indicating that the evolution of the East Asian Monsoon was controlled not only by glacial-interglacial cycles,but also by the phased uplifts of the Tibetan Plateau during the Quaternary.

The First Loess-Based Paleoclimatic Reconstruction over the Last Interglacial-Glacial Cycle in the Hunshandake Sandy Land

Objective Although extensive lakes and eolian sands within and surrounding the Hunshandake Sandy Land(HSL)are sensitive to paleoenvironmental variations in arid and semi-arid eastern Inner Mongolia(e.g.,Yang et al.,2013),these records are commonly confined to the last deglaciation,hampering a complete understanding of

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.

Impacts of climate change on glacial water resources and hydrological cycles in the Yangtze River source region,the Qinghai-Tibetan Plateau,China:A Progress Report

The Yangtze River Source Region has an area of 137,704 km2.Its mean annual runoff of 12.52 billion m3,which was recorded by the Chumda Hydrological Station in 1961–2000,accounts for only 0.13 percent of the Yangtze River's total annual streamflow.The extensive rivers,lakes,wetlands,glaciers,snow fields,and permafrost of the Yangtze River Source Region,as well as the region's vast alpine grasslands,play a critical role in storing and regulating the flow of water not only in the upper Yangtze River watershed of Qinghai,Sichuan,the Tibet Autonomous Region (TAR) (Tibet) and Yunnan,but also throughout the entire lower Yangtze River basin.Climate change has been the dominant factor in recent fluctuation in the volume of the Yangtze River Source Region's glacier resources.The Chumda Hydrological Station on the lower Tongtian River has registered a mean annual glacial meltwater of 1.13 billion m3 for the period 1961–2000,makes up 9 percent of the total annual runoff.Glacial meltwater makes up a significant percentage of streamflow in the Yangtze River Source Region,the major rivers of the upper Yangtze River Source Region:the Togto,Dam Chu,Garchu,and Bi Chu (Bu Chu) rivers all originate at large glaciers along the Tanggula Range.Glaciers in the Yangtze River Source Region are typical continental-type glaciers with most glacial meltwater flow occurring June–August;the close correlation between June–August river flows and temperature illustrates the important role of glacial meltwater in feeding rivers.Glaciers in the source region have undergone a long period of rapid ablation beginning in 1993.Examination of flow and temperature data for the 1961–2000 period shows that the annual melting period for glacial ice,snow,and frozen ground in the Yangtze River Source Region now begins earlier because of increasing spring temperatures,resulting in the reduction of summer flood season peak runoffs;meanwhile,increased rates of glacier ablation have resulted in more uneven annual distribution of runoff in the source region.The annual glacial meltwater runoff in the Yangtze River Source Region is projected to increase by 28.5 percent by 2050 over its 1970 value with the projected temperature increase of 2℃ and a precipitation increase of 29 mm.As a critical source of surface water for agriculture on the eastern Qinghai-Tibet Plateau and beyond,the mass retreat of glaciers in the Yangtze River Source Region will have enormous negative impacts on farming and livestock-raising ac-tivities in upper Yangtze River watershed,as well as on the viability of present ecosystems and even socioeconomic development in the upper Yangtze River Basin.

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.

Comparative population genomics reveals glacial cycles to drive diversifications in tropical montane birds(Aves,Timaliidae)

Many bird species are specialized to live in the broadleaved,evergreen forests in the mountain regions in Southeast Asia.These mountain habitats are not continuously distributed as the different mountain areas are separated by lowlands,which has restricted gene flow and thus contributed to the high biological diversity in this region.The degree of connectivity between mountain areas has fluctuated with the Pleistocene glacial cycles,being largest during the glaciations when the mountain forests spread to lower elevations.Here we study how the intermittent periods of restricted gene flow and connectivity between the populations of five montane species of babblers(Aves,Timaliidae)in Vietnam may be traced in their genomes.The results suggest that the babbler species in the Central Highlands have been isolated from their sister-populations in northern Vietnam for between ca.585 and 380 ky.For two species with populations in both the Central Highlands and the Da Lat region,we found that these split at more or less the same time(440–340 kya).We also found a significant statistical correlation between the time of the splits of these populations and the lowest altitude at which they are known to occur(no similar correlation was found with the geographic distances between populations).The populations in northern Vietnam show higher genetic variation than their counterparts in South-Central Vietnam,supporting the postulate that smaller populations may have lower genetic variation than larger.In accordance with this,we found the lowest genetic variation in the two species with the smallest populations in the Central Highlands.These two populations also show low levels of genomic heterozygosity.Our results show that the south-central populations of the studied babbler species are genetically distinct from their sister-populations in northern Vietnam,providing additional argument for the long-term protection of the evergreen mountain forests in Southeast Asia.

CO2 Air-Water Exchanges during Seasonal and Glacial Cycles

Based on the photosynthesis-respiration reversible reaction and the available statistics, we attempted to quantify the planetary seasonal exchanges of CO2 between air and water from 1970 and compared them to the glacial ACC cycles as reported from ice cores archives. In 2020, the overall continental absorption (AW) was 8.0 giga tonnes of carbon per year (GtC/y). Emissions into the atmosphere (EW) resulting from mineral degradation by respiration and combustion of biomass and fossil hydrocarbons were 14.7 GtC/y, an increase of 2.4% per year since 1970. The continental surplus balance (-AW+EW) of 6.7 GtC/y was shared between the atmosphere, which received 5.1 GtC/y (GATM), and the ocean which absorbed 1.6 GtC/y. This ocean contribution (OC) corresponded to 17% of the 9.2 GtC/y emissions by combustion of fossil hydrocarbons (EFOS). Analysis of the ACC oscillations during 2020 in the northern hemisphere showed that the ocean absorbed 11.1 GtC during the warm season and outgassed 9.5 GtC during the cold season. Assuming proportionality to world population, the ACC, 414 parts per million (ppm) in 2021, would reach 584 ppm in 2080, still growing at a rate of 0.6% per year. The gain of atmospheric CO2 (GATM) and its absorption by the ocean (OC) were expected to peak at 7.0 and 2.2 GtC/y, respectively, in 2080. This increase in the availability of atmospheric CO2 resulted in improved yields of agriculture which more than compensated for the reduction by half of food-producing areas per capita from 1970.

Palaeoclimatic Cycles, Global Environmental Changes and New Glacial Periods Induced by the Impact of Extraterrestrial Bodies

In terms of Earth\|Sun geometry, the Milankovitch theory has successfully explained most of the cyclic palaeoclimatic variations during the history of the Earth, especially in the Quaternary. In this paper, the authors suggest that the impact of extraterrestrial bodies on the Earth may be another mechanism to cause palaeoclimatic cycles, global environmental changes and new glacial periods. Based on geological and geochemical records in the boundary layers produced by six huge Cenozoic bolide\|impact events (65, 34, 15, 2.4, 1.1, 0.73 Ma B.P.), including those at 34, 15, 1.1 and 0.73 Ma B.P. which are represented by four famous tektite\|strewn fields, the process and mechanics of palaeoclimatic cycles and global environmental catastrophes induced by extraterrestrial impact are discussed in detail. Impact\|generated dust, soot and aerosol floating in the stratosphere could result in short\|term (<1 year), rapid drop in temperature immediately after impact. Through self\|regulation of the Earth’s climate system, the temperature at the surface slowly went up within 100a and maintained stable for a long time at 250K. If there were no other factors leading to the break\|down of the newly\|established equilibrium, a new glacial period would be initiated. Estimating from the thickness of \{δ\{\}\+\{13\}C\} and \{δ\{\}\+\{18\}O\} anomalies in sediments across the impact boundary layer and deposition rate, the duration of two stages of the palaeoclimate cycle in the form of cold weather—greenhouse effect—normal weather was 10\+4-10\+5a, respectively. The conclusion deduced from the above model is supported by palaeotemperature change recorded by oxygen isotope in sediments across the impact boundary layer.

Glacial Thermohaline Circulation and Climate:Forcing from the North or South?

Based on the evidence available from both observations and model simulations, the author proposes a view that may provide a unified interpretation of the North Atlantic thermohaline variability. Because of the slow response time of the Southern Ocean （millennia） and the relatively faster response time of the North Atlantic （centuries）, the North Atlantic thermohaline circulation is controlled predominantly by the climate forcing over the Southern Ocean at the long glacial cycle timescales, but by the North Atlantic climate forcing at the short millennial timescaies.

四川盆地及周缘前震旦系裂谷特征与油气地质意义

四川盆地及周缘已被证实发育较大规模的前震旦系裂谷,但其在盆地内部的展布及发育特征尚不明确,因此在一定程度上制约了对盆地深部构造格局的认识。为此,在前人研究的基础上,利用最新的重磁电资料,通过联合解译和小子域滤波等新技术对新元古界构造形态进行了研究,同时结合区域地震大剖面的精细解释并辅以航磁资料进行验证,分析了新元古代裂谷的特征及其对上覆地层的沉积控制作用。研究结果表明:①盆地内部自西北至东南共发育3条近乎平行的前震旦系裂谷,其中以川中裂谷规模最大;②裂谷内部发育一系列与裂谷走向近平行的次级正断层,将裂谷内部结构复杂化,形成一系列断陷;③裂谷内断层在平面上呈平行/斜列式、相向/相背平行式及同向平行式组合,对应在剖面上呈阶梯式、垒堑式、地堑式及铲式半地堑式等组合特征;④盆地东北部盆缘露头揭示南华系—陡山沱组在裂谷内发育冰期—间冰期交互沉积,主要为三角洲、陆棚与斜坡盆地相碎屑岩和冰碛岩。结论认为,应用重磁联合解译+井震资料修订+露头剖面验证的新方法,证实四川盆地前震旦系裂谷的存在,且南华纪裂谷边界(主干)断裂控制了上覆地层沉积古地理格局和坡折带的发育,部分裂谷控制了寒武系或早古生界沉积中心的分布,并对后期沉降中心、构造圈闭的形成以及含油气系统有着极为重要的影响。

Western Pacific in glacial cycles: Seasonality in marginal seas and variabilities of Warm Pool

A serics of low-latitude marginal seas, ranging from the southern South China Sea in the north to the Arafura Sea in the south, are located within the Western Pacific Warm Pool. As shown by rnicropaleontological, isotopical and organic geochemical analyses, the sea surface temperatures in the marginal seas at the last glacial maximum were much cooler than those in the open Western Pacific Ocean. The emergence of extensive shelves of the marginal seas at the glacial low sea-level stand and the decrease of surface temperatures in their deeper water parts resulted in a remarkable reduction of the ability of vapor and heat transport to the atmosphere, causing variabilities to the Warm Pool in the glacial cycles. The intensification of winter monsoon at the glacial stages not only led to a decrease of the surface water temperature and hence to an enhanced seasonality, but also carried moisture from the sea to the tropical islands, giving rise to the downward shift of snowline and mountainous vegetation zones there. It may offer a new alternative in solution of the “Tropical Ocean Paleo-temperature Enigma”.

晚更新世冰期旋回成因的南大洋机制及其对北极冰盖形成的启示

目前,学术界普遍认为南大洋对调节晚更新世冰期/间冰期大气二氧化碳分压(pCO_(2))变化发挥了重要作用。在晚更新世,冰期大气pCO_(2)比间冰期大气pCO_(2)下降约90×10^(−6)。而在约2.7 Ma,随着北极冰盖快速扩张(intensification of Northern Hemisphere Glaciation,iNHG),冰期旋回振幅增大,大气pCO_(2)也骤降。探究晚更新世冰期及iNHG时期大气pCO_(2)下降的原因,对构建完整的冰期旋回理论意义重大。本文综合晚更新世冰期南大洋北部的亚南极区(Subantarctic Antarctic Zone,SAZ)和南部的南极区(Antarctic Zone,AZ)的洋流、海冰、生产力等记录,分析了两个区域在晚更新世冰期可能的储碳机制,并结合iNHG时期各项地质记录,讨论南大洋洋流、碳储库在iNHG期间所发生的变化。结果认为,SAZ和AZ使冰期大气pCO_(2)下降的机制不完全相同,铁肥输入增强导致SAZ生物泵效率增强,增加了海洋固碳,而在AZ,深水通风减弱、海冰扩张、深海分层增强是加强深海碳封存的关键机制。同时,iNHG时期洋流、碳储库等记录表明,南源水向北大西洋、北太平洋深部显著扩张,南大洋海冰扩张,铁肥输入增强,太平洋碳储库增大,暗示iNHG时期南大洋机制可能是大气pCO_(2)下降的原因,直接造成了晚上新世北极冰盖的最终形成。

Preliminary reconstruction of the desert and sandy land distributions in China since the last interglacial period

The desert and sandy land are the products of arid climate. The spatial distribution of modern deserts and sandy land in China and their relation to climate show following characteristics: arid and hyper-arid desert zones, at isohyet of less than 200 mm, are dominated by mobile dunes; semi-arid steppe and arid desert steppe with the precipitation between 200?00 mm, are dominated by semi-fixed and fixed sand dunes; the precipitation of sub-humid forest grassland and humid forest zones with scattered fixed sand land is higher than 400 mm. With this as reference, in combination with considerable amount of paleoclimatic data in desert regions and adjacent regions, the distributions of desert and sandy land in China during the last intergla-cial period, the last glacial maximum (LGM), and the Holocene megathermal, were preliminarily reconstructed. The results compared with that of today show that the distribution of desert and sandy land in China was greatly dwindled during last interglacial period, and the mobile dune area was about two-thirds of that of today's, but greatly expanded during LGM. However, the dwindling area of desert and sandy land in the Holocene megathermal was smaller than that in the last interglacial period. The forcing mechanism was mainly related to the changes of East Asian winter and summer monsoon, south-northward swing of the westerlies and the variations of the Qinghai-Tibet Plateau monsoon intensity caused by global climate changes during the cold and warm intervals since the last interglacial period.

Late Quaternary glacial cycle and precessional period of clay mineral assemblages in the Western Pacific Warm Pool

Variability of clay mineral assemblages in the Western Pacific Warm Pool(WPWP) over the past 370 ka shows the prominent glacial-interglacial cyclicity.Smectite(62%-91%) is the dominant clay mineral,with decreased contents during interglacials while increased in glacials.In contrast,variations in chlorite(4%-21%),illite(4%-12%),and kaolinite(2%-10%) share a similar pattern with higher contents during interglacials than glacials,mirroring to that of smectite.The results indicate that the smectite-dominated clay minerals derive mainly from the river detrital inputs of New Guinea.The glacial-interglacial cycle of clay mineral assemblages well correspond to the fluctuation of sea level.When the sea level was low,the river materials can travel more easily across the narrow shelf off the island of New Guinea,inject directly into the subsurface currents flowing westwards,then merge into the Equatorial Undercurrent(EUC),and eventually deposit on the central part of WPWP.Precessional periods of the smectite content indicate the intensity of mechanical erosion in its provenance of New Guinea,responding to the river runoff and precipitation,and this could also be linked to the meridional migration of the Intertropical Convergence Zone(ITCZ).

Calcium carbonate pump during Quaternary glacial cycles in the South China Sea

The preservation and dissolution of calcium carbonate (namely calcium carbonate pump) controls the pH of seawater in global oceans by its buffer effect, and in turn plays a significant role in global changes in atmospheric CO2 concentration. The results from measured carbonate con-tents over the past 2 Ma at ODP Site 1143 in the South China Sea provide high-resolution records to explore the process of the calcium carbonate pump during Quaternary glacial cy-cles. The results indicate statistically that the highest car-bonate accumulation rate leads the lightest d 18O by about 3.6 ka at transitions from glacials to interglacials, and that the strongest carbonate dissolution lags the lightest d 18O by about 5.6 ka at transitions from interglacials to glacials. The calcium carbonate pump releases CO2 to the atmosphere at the glacial-interglacial transitions, but transports atmos-pheric CO2 to deep sea at the interglacial-glacial transitions. The adjustable function of the calcium carbonate pump for the deep-sea 23CO- concentration directly controls parts of global changes in atmospheric CO2, and contributes the global carbon cycle system during the Quaternary.

辽宁新元古代各阶段升降界面的再认识

【研究目的】辽宁地区位于华北板块东北缘,传统观点认为华北板块自吕梁-四堡运动之后直至古生代末期,一直处于构造稳定期,没有受到明显的构造运动影响。近年来研究结果表明,辽宁地区新元古代时期构造运动相对较为频繁。前人根据大连地区1/25万区调(2001)确认的风化夷平面,将辽宁新元古代时期的构造运动统称为晋宁运动,并划分为四个次一级构造运动,分别为万福升降运动(相当芹峪升降运动)、驼山升降运动、茶叶沟升降运动和大连升降运动,其中驼山升降运动和茶叶沟升降运动的划分定义存在不准确性,其命名有待商榷,需进一步研究探讨。【研究方法】本文以辽宁地区的新元古代地层为研究对象,以区域地质调查资料为基础,结合同位素测年资料对辽宁省新元古代升降运动进行了重新划分与定义。【研究结果】通过区域对比研究划分出晋宁运动和大连运动两个旋回和七个次一级的升降运动,并将其对应于三次冰期、两次间冰期以及冰期前和冰期后。七个次一级的降运动分别命名为芹峪升降、殷屯升降、大孤山升降、太子河升降、复州升降、南关岭升降和大连升降。殷屯升降、大孤山升降、太子河升降、复州升降和南关岭升降等五个次一级构造运动,本次统称之为晋宁运动,代表新元代早期的构造运动;新元古代中晚期(约890~541 Ma),辽宁地区缺失原兴民村组之上地层,代表新一期构造运动抬升的产物,本次将该期运动称之为大连运动,与西北的柯坪运动和南方的澄江运动基本相当。芹峪升降界面标志着四堡运动的结束和晋宁运动的开始;青白口系周家崴子组和王家坦子组之间的沉积间断称为南关岭升降,南关岭升降界面标志着晋宁运动的结束和大连运动的开始;大连升降界面(约541 Ma)的确认,标志着新元古代大连运动的结束和早古生代兴凯运动的开始。【结论】辽宁地区新元古代早期构造运动较为频繁,存在三次冰碛作用和多处平行不整合界面,可划分为晋宁运动和大连运动两个旋回以及七个次一级的升降运动,为区域地层研究对比提供重要参考资料。

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.

Palaeoclimatic cycles and new glacial periods induced by the impact of extraterrestrial bodies

THE consequence of "nuclear winter" induced by nuclear war and climatic catastrophe induced by extraterrestrial impact were widely studied for fear of the potential danger of the basic nuclear war (the totalexplosive equivalent 5 000Mt TNT). Using zero-dimensional energy balance model authors reportedthe short-term climatic effect induced by six huge Cenozoic bolide-impact events (65, 34, 15, 2.4,1.1, 0.73 MaBP). However, only the direct climatic effect of dusts yielded by the impact was considered in the previous study. In this note, based on the previous simulation results the effect of variance ofglobal reflectance with temperature on the long-term climatic change was further taken into consideration.Combined with the strata records of palaeoclimatic change the relationship of impact energy with its in-

Late Quaternary eolian records in the northwest Pacific with glacial cycles: a comparison

Two deep-sea cores in the northwest Pacific have been analysed for sedimentology, mineralogy and environmental magnetism. The results show that after eliminating the interference from volcanism, several proxies such as quartz content, mass susceptibility and anhysteretic magnetic remanence can be used to indicate the eolian deposit from East Asia, and provide information on paleo-atmospheric circulation. A comparison of eolian record in Cure RC10-175 with its oxygen isotopic curve has revealed that the peaks of eolian accumulation occurred at the climatic “optimum” of the Holocene and the last interglaciation, showing the fairly complex nonlinear relationship between continental/pelagic eolian records and the global glacial cycles as well as within the climatic and environmental system.