Correlation and interpretation of paleosols and loess across European Russia and Asia over the last interglacial-glacial cycle     

Nathaniel W Rutter  Dean RokoshMichael E Evans  Edward C LittleJiri Chlachula  Andrei Velichko 《Quaternary Research》2003,60(1):101-109

Loess-paleosol sequences of the last interglacial-glacial cycle are correlated from European Russia to central Siberia and the Chinese Loess Plateau. During cold periods represented by marine oxygen isotope stages (OIS) 2 and 4, loess deposition dominated in the Russian Plain and the Loess Plateau. In central Siberia, loess deposition took place also, but five to seven thin, weakly developed paleosols are identified in both stages. OIS 3, in the Chinese Loess Plateau near Yangchang, consists of a loess bed that is flanked by two weakly developed paleosols. At Kurtak, Siberia, OIS 3 is represented by two distinct, stacked paleosols with no loess bed separating the paleosols. In the Russian Plain, OIS 3 consists of a single, possibly welded paleosol, representing upper and lower stage-3 climates. Brunisols and Chernozems dominate the profiles in China and Siberia, whereas Regosols, Luvisols, and Chernozems are evident in the northern and southern Russian Plain, respectively. OIS 5 is represented in China and the Russian Plain by pedo complexes in a series of welded soils, whereas in contrast, the Kurtak site consists of six paleosols with interbedded loess. The paleosols consist largely of Brunisols and Chernozems. Although the three areas examined have different climates, geographical settings, and loess source areas, they all had similar climate changes during the last interglacial-glacial cycle.  相似文献   

Paleovegetation of marine isotope stages 4 and 3 in northern new zealand and the age of the widespread rotoehu tephra     

Phil Shane  Anna Sandiford 《Quaternary Research》2003,59(3):420-429

Paleolake sediment, constrained by tephrochronology, from Onepoto basin volcanic crater in Auckland, Northern New Zealand (36° 48′S), provides one of the few uninterrupted records of paleovegetation for marine oxygen isotope stages (MIS) 4 and 3 (76,000–26,000 yr B.P.) in the region. This period was characterized by cool temperate conifer-hardwood forest that lacked some of the warmer taxa typical of the Holocene. The period 64,400–60,500 yr B.P. was marked by opening of forest canopy and expansion of small trees and shrubs, and correlates to the thermal minima of MIS 4. However, the landscape was never as open as the forest-shrubland mosaic of the MIS 2. The beginning of MIS 3 (60,500–50,500 yr B.P.) was marked by the dramatic expansion and then decline of conifer-hardwood forest dominated by Dacrydium cupressinum, a species that prefers wetter conditions. This forest was succeeded by the typically montane Nothofagus at 50,500 yr B.P., corresponding to a thermal decline. Thus, MIS 3 began with an abrupt change to moist cool conditions that lasted about 5000 yr, followed by gradual cooling and dryer conditions. This supports some interpretations from other parts of the southwest Pacific region, that MIS 3 was a period of increased precipitation. The widespread and stratigraphically important Rotoehu tephra, erupted from Okataina Volcanic Centre, has been variously dated at 45,000–65,000 yr B.P. At Onepoto, sedimentation rate and paleovegetation reconstruction imply an age of c. 44,300 yr B.P. The tephra provides a correlation horizon in the marine and terrestrial realms during a period (MIS 3) difficult to date by radiometric methods.  相似文献   

A fundamental Precambrian–Phanerozoic shift in earth's glacial style?     

D. A. D. Evans   《Tectonophysics》2003,375(1-4):353

It has recently been found that Neoproterozoic glaciogenic sediments were deposited mainly at low paleolatitudes, in marked qualitative contrast to their Pleistocene counterparts. Several competing models vie for explanation of this unusual paleoclimatic record, most notably the high-obliquity hypothesis and varying degrees of the snowball Earth scenario. The present study quantitatively compiles the global distributions of Miocene–Pleistocene glaciogenic deposits and paleomagnetically derived paleolatitudes for Late Devonian–Permian, Ordovician–Silurian, Neoproterozoic, and Paleoproterozoic glaciogenic rocks. Whereas high depositional latitudes dominate all Phanerozoic ice ages, exclusively low paleolatitudes characterize both of the major Precambrian glacial epochs. Transition between these modes occurred within a 100-My interval, precisely coeval with the Neoproterozoic–Cambrian “explosion” of metazoan diversity. Glaciation is much more common since 750 Ma than in the preceding sedimentary record, an observation that cannot be ascribed merely to preservation. These patterns suggest an overall cooling of Earth's longterm climate, superimposed by developing regulatory feedbacks involving an increasingly complex biosphere.  相似文献   

中国热带第四纪气候波动幅度问题   总被引：2，自引：2，他引：2  

黄镇国  张伟强 《热带地理》2005,25(1):1-4,9

根据40多个有关气候波动的实例分析，中国热带第四纪几个特征时段比今升温的幅度为1.0～3.0℃：降温幅度较大者为3．0～7．0℃，较小者为1．0—3．0℃。而中国热带地区现代理论雪线高度约为4300m；北半球长年冻土地带南界的年均温为-6．0～-8．0℃。因此，中国热带除台湾岛外，第四纪不具备形成冰川或冰缘现象的气候条件。  相似文献   

山西临汾盆地黄土及其形成古环境   总被引：2，自引：1，他引：2       下载免费PDF全文

王克鲁  盛学斌 《地震地质》1996,18(4):339-348

叙述了临汾盆地黄土地层分布特征，并根据王绪典型黄土剖面孢子花粉、颗粒成分、古土壤特点以及磁化率变化，将王绪剖面划分为１８个气候组及１９个温暖期和２０个干冷期，每个干湿期构成一个气候旋回，这些旋回均可同深海沉积物所揭示的古气候旋回对比  相似文献   

江苏建湖地区全新世孢粉组合及其地质、古地理意义   总被引：3，自引：0，他引：3  

吴学忠  王绍鸿  赵希涛 《地理科学》1996,16(3):252-259

对江苏建湖地区若干全新世剖面进行了系统的孢粉分析，划分出６个孢粉组合带，恢复了本地区自早全新世以来的古植被演替与古气候古环境变迁，探讨了本区全新世地层时代划分与对比  相似文献   

Solar variability and the levels of Lake Victoria,East Africa,during the last millenium   总被引：1，自引：0，他引：1  

J. Curt?StagerEmail author  David?Ryves  Brian F.?Cumming  L. David?Meeker  Juerg?Beer 《Journal of Paleolimnology》2005,33(2):243-251

A new diatom series with 1–6 year resolution from Lake Victoria, East Africa, shows that lake level minima occurred ca. 820–760, 680–660, 640–620, 370–340, and 220–150 calendar years BP. Inferred lake levels were exceptionally high during most of the Little Ice Age (ca. 600–200 calendar years BP). Synchrony between East African high lake levels and prolonged sunspot minima during much of the last millenium may reflect solar variabilitys effects on tropical rainfall, but those relationships reversed sign ca. 200 years ago. Historical records also show that Victoria lake levels rose during every peak of the ca. 11-year sunspot cycle since the late 19th century. These findings suggest that, if these apparent tropical sun–climate associations during the last millenium were real, then they were subject to abrupt sign reversals.Electronic Supplementary Material to this article is available at .  相似文献   

湖泊沉积物色度在短尺度古气候研究中的应用   总被引：15，自引：0，他引：15  

吴艳宏  李世杰 《地球科学进展》2004,19(5):789-792

在ODP对大西洋海洋沉积物的研究中,色度作为最直观和简便的指标被普遍用于反映千年尺度的气候环境变化。能否用湖泊沉积物色度反映短时间尺度的气候环境变化？利用CIE／L a b表色系,通过青藏高原可可西里苟仁错湖泊沉积物的 L、a和 b值与有关地球化学指标的统计相关关系分析,对湖泊色度指标在短尺度古气候研究中的意义进行了探讨,并据此分析了 1440年以来苟仁错地区的古气候演变。研究表明,L值（亮度）与沉积物 碳酸盐含量正相关,L高时,气候冷干,碳酸盐含量较高;反之,气温上升,湿度增加;a值（红-绿彩度）与沉积物中Mg含量相关,高 a值对应于沉积物中高MgO含量和高Mg／Ca比值,反映气温较高;b（黄-蓝彩度）值与三价铁的含量相关,较高的 b值代表了湖泊处于较强的氧化条件下,因此 b值可以用于反映湖水深度变化,反映有效湿度的变化,b值高,湖水浅,氧化作用增强;苟仁错沉积物 a值和 b值曲线镜像对称进一步反映了冷干-暖湿的气候组合特征。根据沉积物的色度意义,判断苟仁错地区自 1430年进入小冰期,至1890年结束。近40年来气候变化与邻近气象站的器测相吻合。  相似文献   

Late Pleistocene and Holocene climate and geomorphic histories as interpreted from a 23,000 C yr B.P. paleosol and floodplain soils, southeastern West Virginia, USA     

Steven G. Driese  Zheng-Hua Li 《Quaternary Research》2005,63(2):136-149

Field, micromorphological, pollen, whole soil (XRF), and stable isotope geochemical methods were used to evaluate the latest Pleistocene to Holocene climate record from a floodplain-terrace system in southeastern West Virginia. A late Pleistocene (22,940 ± 150 ¹⁴C yr B.P.) silt paleosol with low-chroma colors formed from fluviolacustrine sediment deposited during the last glacial maximum (Wisconsinan) and records a cooler full-glacial paleoclimate. Fluvial gravel deposited between the latest Pleistocene and earliest Holocene (prior to 6360 ± 40 ¹⁴C yr B.P.) was weathered in the middle Holocene under warmer, drier climate conditions, possibly correlated with the Hypsithermal and Altithermal Events of the eastern and southwestern United States, respectively. The glacial to interglacial climate shift is recorded by: (1) changes from a poorly drained landscape with fine-textured soil, characterized by high organic C and redoximorphic features related to Fe removal and concentration, to a well-drained, coarse-textured setting without gley and with significant argillic (Bt) horizon development; (2) changes from a high Zr and Ti silt-dominated parent material to locally derived, coarse fluvial gravels lower in Zr and Ti; (3) a shift from dominantly conifer and sedge pollen in the paleosol to a modern oak/hickory hardwood assemblage; and (4) a shift in δ¹³C values of soil organic matter from −28‰ to −24‰ PDB, suggesting an ecosystem shift from cooler, C3-dominated flora to one that was mixed C3 and C4, but still predominantly composed of C3 plants. A root-restrictive placic horizon developed between the late Pleistocene silt paleosol and the overlying fluvial gravel because of the high permeability contrast between the two textures of soil materials. This layer formed a barrier that effectively isolated the Pleistocene paleosol from later Holocene pedogenic processes.  相似文献   

晚第三纪以前形成古土壤的鉴别、分类及其在古环境研究中的应用   总被引：3，自引：0，他引：3  

黄成敏  王成善 《地球科学进展》2006,21(9):911-917

晚第三纪以前形成的古土壤可以揭示地质时期的古环境。辨识古土壤的主要标志包括野外形态特征、微形态特征、地球化学特征等。当前古土壤分类一般基于现代土壤的系统分类体系，即采用诊断层和诊断特征，辅之以古土壤总体的化学性质等指标划分古土壤类型。形成于晚第三纪以前的古土壤可以重建全球范围的古气候变化历史，同时揭示前寒武纪时期古大气O2分压以及后寒武纪时期古大气CO2浓度水平的演化过程；古土壤具有空间和时间等多重信息，能反映流域或区域的古景观、古地貌、古水文特征。但目前缺乏一个广为接受的古土壤分类系统,成岩作用对古土壤特征的影响以及古土壤记录的古环境信息机制与解译等方面也还需要深入探讨。今后必须加强成岩作用对古土壤特性的影响以及现代土壤与其环境的对应关系的研究。  相似文献