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   

Climate change and population history in the Pacific Lowlands of Southern Mesoamerica   总被引：1，自引：0，他引：1  

Hector Neff  Deborah M. Pearsall  John G. Jones  Brbara Arroyo de Pieters  Dorothy E. Freidel 《Quaternary Research》2006,65(3):390-400

Core MAN015 from Pacific coastal Guatemala contains sediments accumulated in a mangrove setting over the past 6500 yr. Chemical, pollen, and phytolith data, which indicate conditions of estuarine deposition and terrigenous inputs from adjacent dry land, document Holocene climate variability that parallels the Maya lowlands and other New World tropical locations. Human population history in this region may be driven partly by climate variation: sedentary human populations spread rapidly through the estuarine zone of the lower coast during a dry and variable 4th millennium B.P. Population growth and cultural florescence during a long, relatively moist period (2800–1200 B.P.) ended around 1200 B.P., a drying event that coincided with the Classic Maya collapse.  相似文献   

Holocene paleoclimates of southern Arabia from lacustrine deposits of the Dhamar highlands, Yemen     

Caroline Pickens Davies   《Quaternary Research》2006,66(3):454-464

This paper presents new evidence from the Dhamar highlands, Yemen, of paleohydrologic response to fluctuations in Holocene climate. Stratigraphic, geochemical, and chronological analyses of highland peat and lacustrine deposits contribute to knowledge of the timing of early Holocene moisture changes on the Arabian Peninsula, providing a backdrop to understanding early cultural development in the Arabian highlands. The location of the Dhamar highlands, characterized by intermontane valleys surrounded by the highest mountains on the Arabian Peninsula and adjacent to the Indian Ocean is ideal for examining the influence of the Indian Ocean Monsoon (IOM) on the moisture history of this region. Fluctuations in the lacustrine and paleosol records of the Dhamar highlands reflect both local changes in paleohydrology and regional influences on the Holocene paleoclimatic conditions in southwest Arabia. In addition, a peat deposit with a radiocarbon age of 10,253 – 10,560 cal yr BP documents some of the earliest Holocene high moisture conditions on the Arabian Peninsula.  相似文献   

Diatom Paleolimnological Record of Holocene Climatic and Environmental Change in the Altai Mountains, Siberia     

Karlyn S. Westover  Sherilyn C. Fritz  Tatyana A. Blyakharchuk  Herbert E. Wright 《Journal of Paleolimnology》2006,35(3):519-541

The sedimentary diatom records of three shallow lakes in the Altai Mountains, southern Siberia, were examined to assess the nature and timing of Holocene environmental changes. Few paleoenvironmental records, especially reconstructions not based on pollen, have been reported from this region. The lakes differ in elevation, annual precipitation, and catchment vegetation. Diatom assemblages in all lakes were dominated for the entire period of record by small benthic species of Pseudostaurosira Williams & Round, Staurosira Ehrenberg, and Staurosirella Williams & Round. Planktonic taxa only occur in very low abundances (<5%). The most diverse diatom flora was found in Dzhangyskol, which is situated at the lowest elevation within a forested catchment. A lack of detailed information on the ecological preferences of the dominant taxa and the complexity of environmental drivers make direct interpretation of the diatom record difficult. However, other proxies suggest that dramatic shifts in dominance between Staurosira elliptica and Staurosirella pinnata in Grusha Ozero reflect millennial-scale variability in climate. Together, chironomids and diatoms provide evidence of a cooling possibly correlative to the Younger Dryas Stade and subsequent early-Holocene warming consistent with pollen evidence of afforestation, which also is likely linked to increased humidity. By ~6000 cal year BP, the transition to a cooler, more continental climate had begun. The diatom record of Akkol shows significantly less variation in diatom community composition, but biogenic silica accumulation rates, a proxy for diatom productivity, appear to reflect climatic variability driven by insolation trends over the past 8000 years. Long-term variability in Dzhangyskol is not clearly linked to climate.  相似文献   

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   

Bristlecone pine tree rings and volcanic eruptions over the last 5000 yr   总被引：1，自引：0，他引：1  

Matthew W. Salzer  Malcolm K. Hughes 《Quaternary Research》2007,67(1):57-68

Many years of low growth identified in a western USA regional chronology of upper forest border bristlecone pine (Pinus longaeva and Pinus aristata) over the last 5000 yr coincide with known large explosive volcanic eruptions and/or ice core signals of past eruptions. Over the last millennium the agreement between the tree-ring data and volcano/ice-core data is high: years of ring-width minima can be matched with known volcanic eruptions or ice-core volcanic signals in 86% of cases. In previous millennia, while there is substantial concurrence, the agreement decreases with increasing antiquity. Many of the bristlecone pine ring-width minima occurred at the same time as ring-width minima in high latitude trees from northwestern Siberia and/or northern Finland over the past 4000-5000 yr, suggesting climatically-effective events of at least hemispheric scale. In contrast with the ice-core records, the agreement between widely separated tree-ring records does not decrease with increasing antiquity. These data suggest specific intervals when the climate system was or was not particularly sensitive enough to volcanic forcing to affect the trees, and they augment the ice core record in a number of ways: by providing confirmation from an alternative proxy record for volcanic signals, by suggesting alternative dates for eruptions, and by adding to the list of years when volcanic events of global significance were likely, including the mid-2nd-millennium BC eruption of Thera.  相似文献   

千百年尺度气候快速变化及其数值模拟研究进展   总被引：1，自引：0，他引：1  

靳立亚  陈发虎 《地球科学进展》2007,22(10):1054-1065

千百年尺度全球气候快速变化是古气候研究中的一个重要内容。研究发现，末次冰期和全新世都存在着千年、百年尺度的快速气候变化，其变化幅度可以达到典型的地质变化或天文因子所造成的冰期/间冰期的气候振荡幅度，同时这些古气候事件具有全球性。对冰期和全新世气候变化的数值模拟揭示了气候系统对地球轨道参数变化的响应以及海洋、植被、冰盖、温室气体等反馈因子的重要性,其中大洋温盐环流对北大西洋淡水注入的敏感性与末次冰期和全新世气候快速变化密切相联。利用中等复杂程度的气候模式（EMIC）CLIMBER 2模拟了末次冰期典型时段（60~20 ka BP）D/O和Heinrich事件以及东亚气候的响应过程。模拟研究揭示了全新世青藏高原冰雪环境对亚洲—非洲季风气候的显著影响。今后的古气候模拟研究将在改进模式分辨率、结合古气候代用资料确定更加符合历史时期边界条件以进一步改善气候模式的基础上,更加注重气候突变机制的研究以及加强全球变化背景下的区域气候的长期变化研究。  相似文献   

The pollen record from El’gygytgyn Lake: implications for vegetation and climate histories of northern Chukotka since the late middle Pleistocene     

A. V. Lozhkin  P. M. Anderson  T. V. Matrosova  P. S. Minyuk 《Journal of Paleolimnology》2007,37(1):135-153

Three types of pollen assemblages (shrub-dominated, mixed herb- and shrub-dominated, and herb-dominated) characterize the ~ 300,000 year palynological record from El’gygytgyn Lake. Despite major changes in global climatic forcings, all pollen spectra, with a few isolated exceptions, have strong to possible analogs in the modern plant communities of Northeast Siberia and Alaska. Paleoclimatic reconstructions based on squared chord-distance analog analyses indicate two periods (~8600–10,700 ¹⁴C year B.P. and OIS 5e) when summers were perhaps ~2 to 4°C warmer than modern. January temperatures were also warmer than present, and both July and January were wetter than today. Palynological data remain inconclusive as to the establishment of forests near El’gygytgyn Lake at these times. The wettest Julys occurred during OIS 5 d. July temperatures were near modern, and Januarys were colder and drier than now. January temperatures, even into the Middle Pleistocene, generally show little variability, suggesting that the suppression of arboreal taxa during glaciations was likely caused by cool summers with low effective moisture and not by frigid winters. Because age schemes that correlate magnetic susceptibility to variations in summer insolation or ∂¹⁸O have cool plant taxa persisting in warm times (and vice versa), we propose an alternative age model based on the palynological data. Electronic Supplementary Material Supplementary material is available to authorised users in the online version of this article at . This is the first in a series of eleven papers published in this special issue dedicated to initial studies of El’gygytgyn Crater Lake and its catchment in NE Russia. Julie Brigham-Grette, Martin Melles, Pavel Minyuk were guest editors of this special issue.  相似文献   

<Emphasis Type="Italic">An Inconvenient Truth</Emphasis>: the scientific argument     

John W. Nielsen-Gammon 《GeoJournal》2007,70(1):21-26

The movie An Inconvenient Truth is a powerful portrayal of global warming and its impacts. The main scientific argument presented in the movie is for the most part consistent with the weight of scientific evidence, but with some of the main points needing updating, correction, or qualification. The detailed argument relies almost entirely on past and current evidence and neglects almost all information that can be gained from computer models, perhaps because such information would be difficult for a lay audience to grasp, believe, or connect with emotionally. This places an undue weight on current events as signs of ongoing climate change: some such events are apparently not related at all to climate change, while for other specific events the role of global warming is difficult or impossible to establish.  相似文献   

中国历史文献档案中的古环境记录   总被引：14，自引：1，他引：14  

张德二 《地球科学进展》1998,13(3):273-277

我国的历史文献记录是古气候、古环境信息的重要来源，对古全球变化（PAGES）研究计划的目标时段——近2000年（人文记录和自然记录并存的时段）来说，尤其具有重要的科学价值。介绍了我国古文献中的古气候、古环境记录的概况和各项记录如水、旱、雨、雪等的数量统计，综述了这些记录被用于重建定量的气候序列、绘制历史气候复原图、编制古环境事件年表、获取高分辨率的古气候信息诸方面的主要进展。  相似文献