安徽石台上奥陶统稳定碳同位素地层研究及其意义北大核心CSCD

华南奥陶纪地层发育连续,出露广泛,是开展相关地层学研究的理想地区。对皖南池州石台地区上奥陶统大田坝组、宝塔组及汤头组开展了详细的稳定碳同位素地层学研究,研究表明碳同位素曲线在宝塔组中下部显示一次明显的正漂移。根据前人关于该地区宝塔组的牙形类生物地层学研究结果,本碳同位素漂移事件应为GICE(Guttenberg Isotope Carbon Excursion)事件。基于碳同位素变化趋势与华南及全球其他地区进行对比,完善了华南扬子区奥陶系GICE的记录,进一步证实这次碳同位素漂移事件具有较好的区域和全球对比意义。     

西藏岗巴晚白垩世锶同位素曲线的地层学意义及问题讨论

地质历史时期古海洋中的锶同位素组成具有全球基本一致的演化规律 ,并主要受全球性海平面变化影响。根据从西藏岗巴宗山上白垩统剖面中 6 3个海相碳酸盐样品获得的锶同位素测试数据建立了锶同位素演化曲线 ,与北美同时代锶同位素曲线进行了对比 ,证明晚白垩世有一次全球性海平面升降事件 ,在宗山剖面宗山组近底部的年龄值为 89.4 Ma,并讨论了西藏岗巴宗山地区晚白垩世地层划分对比中的一些问题。     

江汉盆地SKD1深钻记录的古新世—始新世极热事件时期的古气候

古新世—始新世极热事件(PETM,～56 Ma)是发生古新世与始新世界线附近的一次快速增温事件,研究PETM事件的气候变化及驱动机制对应对全球变暖对气候和生态系统带来的影响至关重要.然而目前PETM记录较少且其气候效应仍存在很大争议.本文基于江汉盆地SKD1钻孔材料,利用湖泊自生碳酸盐矿物及其氧同位素组成,并结合岩芯岩...     

奥陶系无机碳同位素地层学综述北大核心CSCD

近四十年来,化学地层学,如碳同位素地层学,在古生界地层的划分与对比中获得了广泛的应用,特别是在不同岩相、生物相的地区间对比时发挥了极其重要的作用。目前,在欧洲大陆和美洲大陆均已获得了较为详细的奥陶系无机碳同位素数据,建立了较为可靠的区域和全球对比关系,并据此初步绘制出全球奥陶系δ13Ccarb标准化曲线,共识别出16个同位素事件,其中3个为负漂事件。近年来,在中国华南和塔里木地区也先后识别出个别重要的无机碳同位素事件,但总体来看,还需基于连续露头或钻井、高精度采样建立完整的无机碳同位素曲线,从而建立准确的区域和全球对比。碳同位素作为一种重要的地层对比手段,在奥陶系长时间尺度的区域和全球高精度地层对比中正逐渐发挥重要作用。同时,碳同位素记录在地质历史中生物与环境协同演化研究中也具有不可替代的意义。     

中国西南地区中－晚全新世降温事件的石笋记录

通过对桂林响水洞、荔波董歌洞和云南宁蒗泸沽湖拉家仙人洞3根石笋进行高精度的TIM S-U系测年和氧同位素分析,建立了西南地区6000a B. P.以来的古气候变化时间序列。研究结果表明,西南地区6000a B. P.以来石笋记录的冷暖事件所反映出的古季风变化,大致可分为3个阶段: ( 1) 6000～ 4000a B. P. 间的中全新世气候适宜期,显示东亚夏季风由强盛逐渐变为减弱,气候温暖湿润;( 2) 4000～ 2100a B. P.间的中全新世晚期,是气候冷事件的突变或转换期,显示东亚冬季风增强,太阳辐射强度减弱,气温降低,气候变化幅度增大,特别是在4000～ 3500a B. P.发生的降温事件可能是新仙女木事件( Y. D)以来最为寒冷的一次降温过程,也是历史时期以来最具影响力的一次小冰期,是全新世气候演化过程中的一次重要转变, 标志着气候最适宜期的结束和晚全新世(新冰期-Neog lacial)的开始。( 3) 2100～ 130aB. P.间的晚全新世,是气候相对波动的降温期,在其内包括若干个由干冷到暖湿或由暖湿到干冷的气候变化亚期。      

桂林地区44 ka洞穴石笋碳酸钙(盐)δ13C的同位素组成与大气CO2浓度估算

洞穴石笋碳酸钙(盐)δ13C的同位素记录表明,其与δ18O同位素记录一样,均能反映气候环境的冷暖旋回变化,也具有急速的突变事件记录.本文利用近期或古老的洞穴石笋碳酸钙(盐)δ13C的同位素组成,对桂林地区44 ka以来的大气CO2浓度进行了尝试性的估算,估算结果表明,它可与近期所测量的以及冰岩芯气泡组分分析和北方黄土碳酸盐δ13C估算的大气CO2浓度值基本接近,可以进行相互对比,说明利用洞穴石笋碳酸盐δ¨C同位素组成对大气CO2浓度进行估算的方法是可行的.研究表明,洞穴石笋碳酸盐δ13C同位素的记录,对地质时期的冷事件具有独特的敏感性,特别是对新仙女木冷事件和北大西洋Heinrich的H1至H5冷事件反映较为明显,在干冷期δ13C同位素快速升高,总体上与大气CO2浓度的变化呈反比,大气CO2浓度的变化与全球性的气候波动大体一致,但存在明显的区域性变化特征.     

四川江油石炭纪锶同位素曲线—年代地层对比和海平面变化

据从采自四川江油马角坝石炭系剖面中的未蚀变海相岩石样品中获得的22个锶同位素测试数据，建立了剖面的石炭纪锶同位素演化曲线。马角坝剖面的锶同位素曲线与我们在贵州惠水、Denison等在北美建立的同时代锶同位素曲线总体上是一致的，表明了锶同位素曲线对海相地层进行年代地层划分对比的重要性，根据对比结果，讨论了马角坝石炭系剖面的年代地层划分和海平面变化。     

以气候变化为标志的中国第四纪地层对比表

随着新技术方法的不断引入和地层学多元划分理论的提出,除了传统的岩石地层、生物地层和年代地层,又开拓了地貌地层、磁性地层、土壤地层、同位素地层、事件地层和旋回地层等新的分支。高分辨率古气候研究的需要,促使我们去探索第四纪地层,特别是陆相地层新的划分方案。本文作者在各自对不同的成因类型的第四纪沉积物的研究中,都或多或少参照深海氧同位素阶段进行过地层的划分和对比的尝试,自然就产生了以氧同位素阶段为参照的划分和对比第四纪地层的设想。我们“抛砖引玉”,提出了中国第四纪ＭＩＳ地层表,只求“有”,尚不能求“准”,希望我们的工作能够推进我国第四纪地层的研究,对第四纪科学的发展作出贡献。     

安徽石台上奥陶统稳定碳同位素地层研究及其意义

华南奥陶纪地层发育连续,出露广泛,是开展相关地层学研究的理想地区。对皖南池州石台地区上奥陶统大田坝组、宝塔组及汤头组开展了详细的稳定碳同位素地层学研究,研究表明碳同位素曲线在宝塔组中下部显示一次明显的正漂移。根据前人关于该地区宝塔组的牙形类生物地层学研究结果,本碳同位素漂移事件应为GICE(Guttenberg Isotope Carbon Excursion)事件。基于碳同位素变化趋势与华南及全球其他地区进行对比,完善了华南扬子区奥陶系GICE的记录,进一步证实这次碳同位素漂移事件具有较好的区域和全球对比意义。     

末次冰期贵州七星洞石笋高分辨率气候记录与Heinrich事件

通过对贵州都匀七星洞Q4、Q6石笋进行高精度的TIMS-U系测年和氧同位素分析,建立了末次冰期60．5kaB P以来都匀凯酉地区高分辨率的古气候变化时间序列。通过与格陵兰GISP2冰心的δ^18O曲线对比分析,初步揭示并探讨了末次冰期以来反映的短时间尺度气候快速变化的D-O旋回事件1-18和Heinrich事件H1～H5在黔南七星洞中的石笋记录,并对冷事件发生的年代给出了界定。研究表明,黔南60．5kaB P以来石笋记录冷暖事件所反映出的古季风环流变化,明显受北大西洋气候振荡的影响,显示与北极地区存在着古     

云南华坪全新世大暖期百年尺度的季风气候的石笋记录

通过对云南华坪葫芦洞FL4石笋进行高精度的ICP—MS—230Th/U测年和高分辨率的碳、氧同位素分析,建立了该地区6 060-4 185 a BP间高分辨率的西南季风气候变化时间序列,进而揭示了该时段发生的3次季风减弱事件。 这3次百年尺度（持续时间为90～240a）的干旱寒冷事件,分别发生在6 060－5 950 a BP、5 380－5 140 a BP、4 810-4 620 a BP,呈台阶状演变;而石笋的碳同位素记录揭示了2次强降水事件,分别发生在5 503－5 443 a BP和4 210-4 185 a BP,持续时间分别为25a和60a。石笋碳、氧同位素记录的西南季风减弱以及强降水事件明显受太阳辐射强度的控制。分辨率为3~10 a的碳、氧同位素记录表明,在百年尺度的西南季风气候变化上,叠加了一系列十年尺度的气候突变事件,呈锯齿状的高频波动。这些短时间尺度的季风气候波动事件与树轮14C 残差、冰芯记录极为相似,反映低纬度地区石笋记录的季风气候与高纬度及北极地区的气候具有极好的可比性,可能主要是受中低纬度太阳辐射强度以及北半球大气环流的影响,太阳辐射强度的变化是控制印度季风的快速推进或退出(萎缩)以及百年尺度上的气候波动的主要动因。      

青藏高原东缘都江堰湖相沉积MIS3a阶段的快速气候变化记录

深海氧同位素第3阶段晚期(MIS3a)是青藏高原较为特殊的暖湿时期, 为了解这一时期高原东缘的气候变化细节, 利用AMS14C定年和粒度、总有机碳、正构烷烃等环境代用指标提取了四川都江堰湖相沉积剖面的相应记录.经过校正后的日历年龄显示此剖面沉积于43.6~34.6 kaBP期间, 记录了千年尺度的D-O旋回事件, 其分布时段分别为: DO11(43.6~41.8 kaBP), DO10(41.8~39.2 kaBP), DO9(39.2~37.7 kaBP), DO8(37.7~35.5 kaBP), DO7(35.5 kaBP~未见顶).该剖面总有机碳曲线与南京葫芦洞石笋和格陵兰冰心(GRIP)氧同位素曲线的对比表明, 该区域气候记录对全球高纬地区的冰量变化和亚洲季风演化具有响应; 而中纬度太阳辐射岁差对该区域气候波动的控制作用较强导致了细节上存在差异.      

A radiometric calibration of the SPECMAP timescale

The astronomical theory of climate change asserts that Earth's climate is affected by changes in its orbit, which vary the seasonal and latitudinal distribution of solar radiation. This theory is the basis of the orbitally tuned SPECMAP timescale. A key constraint for this important chronology was the mid-point of the Penultimate Deglaciation, initially dated to 127,000 years ago. Recent work suggests this event may be considerably older, casting doubt on the astronomical theory, the SPECMAP timescale, and the accuracy of orbitally tuned chronologies. Difficulties with U/Th coral dating of sea-level events have impeded progress on this problem, because most corals are not closed systems. Here, we use a new approach to U/Th dating that corrects for open-system behavior and produces a sea-level curve of sufficient resolution to confidently correlate with SPECMAP over the last 240,000 years, permitting a reassessment of both this critical chronology and a central tenet of climate change theory. High-precision ages for 24 oxygen isotope events provide a 240,000-year chronology for marine δ¹⁸O records that is independent of orbital tuning assumptions. Although there appear to be significant differences between the radiometric and orbitally tuned timescales near the lastglacial maximum and at the Marine Isotope Stage 7/6 boundary, a comparison of radiometric and SPECMAP ages for identical isotope events suggest that the SPECMAP timescale is quite accurate and that its errors were, in general, overestimated. Despite suborbital complexity, orbital cyclicity is clearly evident in our record. High-amplitude sea-level oscillations at periods greater than 20,000 years are very close in phase to summer insolation in the Northern Hemisphere. Although sea-level changes cannot be uniquely tied to a specific season or latitude of insolation forcing, the simplest explanation is that long-period, high-amplitude sea-level change is linked to Northern Hemisphere insolation forcing. These results validate the principles of orbital tuning and suggest such timescales are generally robust.     

桂林地区水南洞14～25万年石笋的碳氧同位素记录和古气候重建

通过对桂林水南洞石笋进行高精度的热电离质谱(TIMS－U)测年和碳氧同位素分析,建立了桂林地区245.20 ka BP至147.90 ka BP间的古气候变化时间序列,确定了石笋记录的时段B与时段C分界的年龄为242.5±6.4 ka BP(相当于深海岩芯氧同位素标准曲线时段7与时段8分界的年龄)、时段A与时段B分界的年龄为 192.6±3.9 ka BP(相当于深海岩芯氧同位素标准曲线时段6与时段7分界的年龄)。桂林地区245.20～147.90 ka BP石笋记录的冷暖事件所反映出的古气候变化,大致可分为3个气候变化阶段:(1) 245.2～242.6 ka BP, 相当于深海岩芯氧同位素标准曲线阶段8的末期;(2) 242.5～192.6 ka BP,相当于深海岩芯氧同位素标准曲线时段7;(3)192.6～147.9 ka BP间的倒数第2次冰期, 相当于深海岩芯氧同位素标准曲线时段6的早中期。石笋的TIMS－U测年和碳氧同位素记录揭示,桂林地区245.2～147.9 ka BP的古气候演变历史与深海岩芯时段8末期、时段7和时段6的氧同位素,深海岩芯中记录的孢子花粉组合、CaCO3含量、海平面的升降变化以及与中国北方黄土、古土壤中记录的孢子花粉组合、成壤程度、全铁富集程度、磁化率变化、原生碎屑CaCO3含量和淋溶强度等所揭示的古气候和古季风变化具有极好的对应关系,表明桂林地区中更新世晚期以来的古气候演变既有全球性特征,又有着强烈的区域性特征。     

Climatic Character of Marine Isotope Stage (MIS) 5e in the Representative Regions of the World: A Review

The Last Interglacial or Marine Isotope Stage (MIS) 5e, is of great interest because it serves as an analog for the Holocene. The climate change and duration during Marine isotope stage (MIS) 5e are considerably well understood for recent and future climate. Despite great interest in this subject over many years, a number of issues concerning the climate circumstances of MIS 5e are by no means resolved. We analyzed 35 published palaeoclimate records with reliable chronologies and robust proxies in typical region of the world to evaluate climate change during MIS 5e. These data indicate that: ① The duration of this warm phase is thought to range from (128±2) ka to (116±2) ka. The climate of MIS 5e was likely relatively stable with a number of abrupt, weak amplitude, cool and/or arid events. And the difference between regions is noticeable for the occurrence, amplitude, onset and duration of these events. For example, marine records from the North Atlantic indicate that the climate of MIS 5e was relatively stable, however the records from Norwegian sea show that the climate of MIS 5e had a significant changes at the beginning and cold event in the Mid-Eemian; The δ¹⁸O, δD and CH₄ in the ice cores from Greenland and Antarctica imply that climate was relatively stable during the last interglacial period, while in Europe from the north to the south the duration of this phase became shorter and the intensity of climatic events became stronger. In addition, the climatic conditions of MIS 5e reconstructed by climate proxy from China are various and have the subject of some controversy. ②The global climate response to the insolation forcing would have been uniform on suborbital timescale. Nevertheless, as a result of regional sundry climatic forcing factors, global millennial-scale/century-scale climate oscillations were marked by significant local features during stage 5e. ③ Based on the better chronological controls, the estimation of climate parameters, the high-resolution climate records, and precise knowledge of the phase relationship between climate changes in global, the earlier depiction for climate circumstances and environment change during Marine Isotope Stage 5e should be refined and our understanding of the climate dynamics and mechanism and climate modelling should be improved.     

Climate records and changes in deep outflow from the Norwegian Sea ∼150–55 ka

In order to contribute to our understanding of the linkage between climate and ocean circulation we have studied benthic foraminifera from near the northern end of the Faeroe–Shetland Channel covering isotope stages 6 to lower stage 3 (∼150–55 ka). Our records demonstrate shifts between recurring assemblages, which on millennial timescales monitor the outflow history of Norwegian Sea Deep Water. The records show that the outflow is closely linked to the climate of the region as documented in the Greenland ice cores. Outflow was relatively strong during all major warmer interstadials whereas there was no outflow during the colder stadials. During isotope substage 5e outflow was stable for ∼10–12 kyr with significant changes at the beginning and end only.     

Oxygen isotope evidence of Little Ice Age aridity on the Caribbean slope of the Cordillera Central, Dominican Republic

Climate change during the so-called Little Ice Age (LIA) of the 15th to 19th centuries was once thought to be limited to the high northern latitudes, but increasing evidence reflects significant climate change in the tropics. One of the hypothesized features of LIA climate in the low latitudes is a more southerly mean annual position of the Intertropical Convergence Zone (ITCZ), which produced more arid conditions through much of the northern tropics. High-resolution stable oxygen isotope data and other sedimentary evidence from Laguna de Felipe, located on the Caribbean slope of the Cordillera Central of the Dominican Republic, support the hypothesis that the mean annual position of the ITCZ was displaced significantly southward during much of the LIA. Placed within the context of regional paleoclimate and paleoceanographic records, and reconstructions of global LIA climate, this shift in mean annual ITCZ position appears to have been induced by lower solar insolation and internal dynamical responses of the global climate system. Our results from Hispaniola further emphasize the global nature of LIA climate change and the sensitivity of circum-Caribbean climate conditions to what are hypothesized to be relatively small variations in global energy budgets.     

Climatic changes since the last deglaciation inferred from a lacustrine sedimentary sequence in the eastern Nanling Mountains,south China

Two sediment cores recovered from Dahu Swamp, which is located in eastern Nanling Mountains in south China, were selected for investigation of palaeoclimatic changes. Multi‐proxy records of the two cores including lithological variation, organic carbon isotope ratio, dry bulk density, organic matter content, magnetic susceptibility, humification degree, median grain size and geochemical proxies reveal that during the last deglaciation three drier phases correspond to the Oldest, Older and Younger Dryas cooling events, and the intercalated two wetter phases synchronise with the Bølling and Allerød warming events. The Holocene Optimum, which was resulted from a strengthening of the East Asian (EA) summer monsoon, occurred in the early and mid Holocene (ca. 10–6 cal. ka BP). In the mid and late Holocene (ca. 6–3 cal. ka BP), a prevailing dry climate suggested a weakening of the EA summer monsoon. The general trend of Holocene climatic changes in this study agrees with the 25° N summer solar insolation, suggesting that orbitally induced insolation may have played an important role in the Holocene climate in the study region. Copyright © 2010 John Wiley & Sons, Ltd.     

Trends,rhythms and events in Plio-Pleistocene African climate

We analyzed published records of terrigenous dust flux from marine sediments off subtropical West Africa, the eastern Mediterranean Sea, and the Arabian Sea, and lake records from East Africa using statistical methods to detect trends, rhythms and events in Plio-Pleistocene African climate. The critical reassessment of the environmental significance of dust flux and lake records removes the apparent inconsistencies between marine vs. terrestrial records of African climate variability. Based on these results, major steps in mammalian and hominin evolution occurred during episodes of a wetter, but highly variable climate largely controlled by orbitally induced insolation changes in the low latitudes.     

古里雅冰芯氧同位素地层学

在冰芯研究中,氧同位素比率不仅是气温的一种代用指标,而且其变化又是冰芯年层划分的依据之一。本文着重阐述了青藏高原古里雅３０９ｍ冰芯中δ^１８Ｏ记录研究的一些结果。对于该冰芯上部１２０ｍ,根据δ^１８Ｏ等的季节变化特征可划分出２０００多个年层,这是该冰芯高分辨率气候环境记录恢复的基础。借助于放射性物质（３６ＣＩ）测年等手段,建立了该冰芯下部的时间标尺。据此恢复了０．１２５Ｍａ以来古里雅冰芯中１８Ｏ记录,将其与深海沉积中的氧同位素变化相比较,可划分出阶段 １,２,３,４和５,其中阶段５又可划分出 ５个业阶段,即ａ,ｂ,ｃ,ｄ和ｅ亚阶段。古里雅冰芯１８Ｏ记录的一个突出特征就是其升高和降低的幅度都很大,这反映了青藏高原对于气候变化的响应是极为敏感的。５ｅ时古里雅冰芯中δ^１８Ｏ所记录的升温幅度达５℃,高于全球平均升温值２～３℃。