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101.
位于现代季风区边缘的沙漠-黄土边界带,具有高度不稳定性。末次间冰期以来历经多次北进南退移动和暖湿、冷干变化。依据古风成砂-黄土-古土壤叠覆更替的沉积序列和磁化率等气候代用指标分析,对末次间冰期以来,尤其是特征时期边界带的位置进行了讨论。其中,盛冰期时移动幅度最大,南界可能达30°N左右;末次间冰期和全新世气候鼎盛期最靠西北,南界在古长城以北。全球冰期-间冰期波动导致的气候变化以及东亚冬夏季风强弱变化是控制边界带移动和气候变化的根本因素。 相似文献
102.
103.
陇西黄土高原马兰黄土划分与末次冰期气候快速变化研究 总被引:9,自引:0,他引:9
陇西黄土高原马兰黄土内存在9个弱成壤组(层),记录末次冰期内多达22个间冰段气候的环境状况。马兰黄土中部古土壤是末次冰期大间冰段的记录,共有上、中、下3层古土壤,含11个亚层,尤以下层古土壤发育最好,表明当时气候较温暖湿润。 相似文献
104.
105.
Julie Brigham-Grette Lyn M. Gualtieri Olga Yu. Glushkova Thomas D. Hamilton David Mostoller Anatoly Kotov 《Quaternary Research》2003,59(3):386-398
The Pekulney Mountains and adjacent Tanyurer River valley are key regions for examining the nature of glaciation across much of northeast Russia. Twelve new cosmogenic isotope ages and 14 new radiocarbon ages in concert with morphometric analyses and terrace stratigraphy constrain the timing of glaciation in this region of central Chukotka. The Sartan Glaciation (Last Glacial Maximum) was limited in extent in the Pekulney Mountains and dates to 20,000 yr ago. Cosmogenic isotope ages > 30,000 yr as well as non-finite radiocarbon ages imply an estimated age no younger than the Zyryan Glaciation (early Wisconsinan) for large sets of moraines found in the central Tanyurer Valley. Slope angles on these loess-mantled ridges are less than a few degrees and crest widths are an order of magnitude greater than those found on the younger Sartan moraines. The most extensive moraines in the lower Tanyurer Valley are most subdued implying an even older, probable middle Pleistocene age. This research provides direct field evidence against Grosswald’s Beringian ice-sheet hypothesis. 相似文献
106.
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
107.
中国北方季风边缘区沙漠/沙地如何响应气候变化及其反馈研究对于理解干旱半干旱地区现代地表过程及其未来环境演变趋势有重要的科学意义。库布齐沙漠作为中国北方季风边缘区中东部唯一的以流动、半流动为主的沙漠,现代地表景观与周围沙地(如毛乌素沙地、浑善达克沙地、科尔沁沙地等)明显不同。晚第四纪以来库布齐沙漠与季风边缘区中东部沙地环境演化过程到底是否一致,其湿润期究竟发生于何时,尚存颇多争议。区域风成沉积和湖泊沉积记录研究得出的结论明显不同,存在中晚全新世和早中全新世湿度最优期的分歧。对库布齐沙漠风成沉积年代-岩性的概率密度分布(Probability Density Function,PDF)进行处理,与周边沙地风成沉积和湖泊沉积古环境记录进行了对比分析。结果表明:末次盛冰期以来库布齐沙漠与季风边缘区中东部沙地环境演化过程总体一致,27.6—10 ka和晚全新世(2—0 ka),风沙堆积强烈,气候相对干旱;早全新世(10—6 ka)古土壤渐次发育,沙丘逐渐被固定,湿度增加,环境状况有所改善;中全新世(6—2 ka)古土壤广泛发育,沙丘经历固定成壤,气候最为湿润。区域环境演变过程受控于低纬太阳辐射和高纬冰量变化的双重制约。 相似文献
108.
S. Mischke U. Herzschuh C. Zhang J. Bloemendal F. Riedel 《Global and Planetary Change》2005,46(1-4):337
Two sediment cores (length 13.94 and 12.93 m) have been drilled from the small alpine Lake Luanhaizi in the eastern central Qilian Mountains and correlated by means of magnetic susceptibility (MS). This paper focuses on the lithology and chronology of the longer core, on the results of loss on ignition (LOI), element concentration, thermomagnetic as well as magnetic hysteresis loop measurements, and on the ostracod record.The recovered sediments represent three types of depositional environment: a shallow intermittent lake, a deeper permanent lake and a true playa lake. Three stages of a higher lake level and permanence of the water body are reconstructed. The lowermost stage of a permanent lake and inferred favourable environmental conditions occurred probably about 45 14C ka BP. The second stage of a deeper permanent lake occurred either shortly before or, more likely, following the LGM. Most favourable environmental conditions and highest water levels were reconstructed for the uppermost stage comprising the Holocene. Considering the lake record, glaciers have not reached the lake site at 3200 m altitude during the LGM, providing further evidence against a large ice sheet on the Tibetan Plateau. 相似文献
109.
CHENG Jie ZHANG Xujiao TIAN Mingzhong YU Wenyang and YU Jiangkuan China University of Geosciences Beijing China TANG Dexiang Institute of Process Engineering Chinese Academy of Sciences Beijing China YUE Jianwei Institute of Geographic Sciences Natural Resources Research Chinese Academy of Sciences Beijing China 《山地科学学报》2005,2(3):193-201
Introduction The Tibetan Plateau, located in west China, was uplifted during the Cenozoic and became the most youthful plateau in the world. Some researches have also shown that it started to develop into the cryosphere in the beginning of the Middle Pleistocene and became one of the three global cryospheres (two other cryospheres being the Artic and the Antarctic) (SHI et al. 1996). Because of the cryosphere development in the Tibetan Plateau, many periglacial and permafrost geomorpholog… 相似文献
110.
Environmental changes in the northern Altai during the last millennium documented in Lake Teletskoye pollen record 总被引:1,自引:0,他引:1
Andrei A. Andreev Roberto Pierau Ivan A. Kalugin Andrei V. Daryin Lyubov G. Smolyaninova Bernhard Diekmann 《Quaternary Research》2007,67(3):394-399
A high-resolution pollen record from Lake Teletskoye documents the climate-related vegetation history of the northern Altai Mountain region during the last millennium. Siberian pine taiga with Scots pine, fir, spruce, and birch dominated the vegetation between ca. AD 1050 and 1100. The climate was similar to modern. In the beginning of the 12th century, birch and shrub alder increased. Lowered pollen concentrations and simultaneous peaks in herbs (especially Artemisia and Poaceae), ferns, and charcoal fragments point to colder and more arid climate conditions than before, with frequent fire events. Around AD 1200, regional climate became warmer and more humid than present, as revealed by an increase of Siberian pine and decreases of dry herb taxa and charcoal contents. Climatic conditions were rather stable until ca. AD 1410. An increase of Artemisia pollen may reflect slightly drier climate conditions between AD 1410 and 1560. Increases in Alnus, Betula, Artemisia, and Chenopodiaceae pollen and in charcoal particle contents may reflect further deterioration of climate conditions between AD 1560 and 1810, consistent with the Little Ice Age. After AD 1850 the vegetation gradually approached the modern one, in conjunction with ongoing climate warming. 相似文献