西南极长城湾NG93-1沉积柱样碳、氧、锶、铅同位素地球化学研究及其古环境意义   总被引：1，自引：1，他引：1  

陈毓蔚  桂训唐  韦刚健  罗又郎 《地球化学》1997,(3)

对西南极西北海域乔治王岛和纳尔逊岛之间长城湾浅水海区柱长８３ｃｍ的沉积柱样ＮＧ９３－１进行了矿物学、Ｓｒ、Ｐｂ、Ｏ、Ｃ等同位素地球化学研究。揭示了沉积物以陆源碎屑物为主，证实南设德兰群岛火山岩是该海区沉积物的重要控制源。Ｏ、Ｃ同位素记录了早全新世以来两次冰期，一次高温的气候变动信息，并指出Ｓｒ、Ｐｂ同位素组成的剖面变化具有气候演变的示踪意义。  相似文献   

网纹红土中的植硅石组合及其环境意义的初步研究   总被引：9，自引：1，他引：9       下载免费PDF全文

李长安  顾延生 《地球科学》1997,22(2):195-198

长江中下游地区网纹红土中的古气候记录，在第四纪全球变化研究中具有十分重要的意义，阐述了江西修水网纹红土的岩性特征和形成时代，重点讨论了网纹红土中的植硅石及其古气候信息，根据植硅石形态的环境意义，结合因子分析，将修水剖面网纹红土所含的植硅石划分为１２个组合带。并将其与黄土－古土壤气候旋回和深海氧同位素气候旋回进行了对比，提出网纹红土也是第四纪全球变化的良好信息载体。  相似文献   

玛纳斯湖的形成和演变     

王道经 《遥感学报》1991,(4)

据根卫星影像图解译,结合其他资料分析,论述玛纳斯湖的形成和演化,它既受地质构造和古气候的制约,也受人类活动的影响。玛纳斯古湖盆形成于中更新世柯克台不爽冰期,晚更新世开始退缩,全新世进而萎缩、解体,以致衰竭、消亡。  相似文献   

Vegetation and climate of the last glacial-interglacial cycle in Southern Illinois,USA     

Hong Zhu  Richard G. Baker 《Journal of Paleolimnology》1995,14(3):337-354

Raymond Basin and Bald Knob Basin, Montgomery County, Illinois, formed as kettles during Illinoian time. Fossil pollen from these basins provides information on vegetation and climate during the last glacial-interglacial cycle. The pollen profile at Raymond Basin contains an expanded Sangamonian section and an early Wisconsinan section, but both are missing the late Wisconsinan. The ages for the following pollen zones are estimated by correlation with the deep-sea ¹⁸O record.In the late Illinoian,Picea-Pinus pollen zone 1, dating from about 150–130 ka, represents an apparently closed boreal coniferous forest indicating a cold late-glacial climate. The Sangamonian includes three major pollen zones ranging from about 130–75 ka. The early Sangamonian is represented byQuercus-Ulmus-Carya-Fagus dominance in zone 2, indicating vegetation comparable to the modern deciduous forest and climate that was warm and moist. The middle Sangamonian in zone 3, which is characterized byAmbrosia-Poaceae-Cupressaceae-Quercus pollen, suggests a savanna vegetation and a warm, dry climate. The late Sangamonian is subdivided into aQuercus-Ulmus-Carya subzone (4a) that indicates a mesic forest and greater precipitation; aQuercus-Ambrosia subzone (4b) that suggests drier climate and savanna conditions; and aQuercus-Liquidambar-Carya subzone (4c), containing the southeastern forest element,Liquidambar, suggesting the peak in warmth and moisture. The early Wisconsinan is represented by a transitionalPicea-Chenopodiineae zone (5). This unusual assemblage suggests a cool prairie-like vegetation, perhaps with scatteredPicea trees at the end of that depositional interval. The Middle Wisconsinan is marked by the return of high percentages ofPicea andPinus pollen in zone 6. The latest pollen zone (7) is dominated by Chenopodiineae pollen and is absent at Raymond Basin. It is most likely Holocene in age, and probably represents prairie conditions and warm, dry climate.Apparent surface-temperature and apparent effective-moisture curves were derived from the first detrended correspondence analysis (DCA) axis of the pollen data. The first axis correlates well with the normalized deep-sea ¹⁸O curve of sea surface temperature, and the second is controlled mainly by precipitation. The interglacial vegetation differs from that predicted by models driven by orbitally-induced insolation curves.This is the 9th in a series of papers published in this special AMQUA issue. These papers were presented at the 1994 meeting of the American Quaternary Association held 19–22 June, 1994; at the University of Minnesota, Minneapolis, Minnesota, USA. Dr Linda C. K. Shane served as guest editor for these papers.  相似文献   

Deciphering some unique paleotemperature indicators in halite-bearing saline lake deposits from Death Valley, California, USA     

Sheila M. Roberts  Ronald J. Spencer  Wenbo Yang  H. Roy Krouse 《Journal of Paleolimnology》1997,17(1):101-130

Saline lake deposits are arguably the best source of mid- to low-latitude terrestrial paleoclimate data. Alternating clastic sediments and evaporites of different chemical composition have long been recognized as sensitive records of changes in inflow and aridity related to a variety of climate parameters. Several sources of paleotemperature information from a halite-bearing saline lake deposit are described here – pseudomorphs of a cold-temperature evaporite mineral, homogenization temperatures of fluid inclusions in halite, and stable-isotope compositions of fluid inclusions in halite. Examples of these paleoclimate data come from analysis of the lower half of a 185-m core drilled in Pleistocene saline lake deposits at Death Valley, California. Daily and seasonal temperature variations in saline lake waters create conditions for the appearance and disappearance of temperature-dependent mineral phases. In the Death Valley core, hexagonal-shaped halite crystals, probable pseudomorphs of the cold-temperature hydrous mineral, hydrohalite (NaCl2H₂O), provide evidence of brine temperatures below about 0 °C. Homogenization temperatures of fluid inclusions in primary halite offer an actual (not proxy) record of surface-brine temperatures. Samples with primary fluid-inclusion textures are carefully selected and handled, and data are collected from single-phase aqueous-brine inclusions chilled to nucleate vapor bubbles. Temperature variations are observable at scales of individual halite crystals (hours to days), single halite beds (weeks to months or years), and multiples of beds to entire facies (hundreds to tens of thousands of years). A ¹⁸O/D stable isotope record from the minute quantities of brines in fluid inclusions in halite is accessible using a method recently developed at the University of Calgary. The stable isotope record from the Death Valley core, a complex response to climate variables including temperature, humidity, storm patterns or seasons, and inflow sources, compliments and expands the interpretation emerging from the stratigraphy and homogenization temperatures.  相似文献   

Environmental magnetism: an introduction   总被引：31，自引：0，他引：31  

Dekkers  M.J. 《Geologie en Mijnbouw》1997,76(1-2):163-182

In environmental magnetism, the properties of magnetic minerals are used as proxy parameters for many purposes. Examples are paleoclimate analysis, paleoceanographic studies, provenance studies of sediments, studies of anthropogenically-induced pollution, and archeological investigations. Mineral-magnetic techniques are sensitive, require little sample preparation, are rapid, often grain-size indicative, and usually non-destructive. These techniques involve bulk properties which makes them complementary to geochemical micro-analytical techniques. Measurements include the field- and temperature-dependence of various types of induced and remanent magnetizations. Mineral-magnetic methods are continuously being improved. The underlying causal relations between observed mineral-magnetic properties and the processes that led to those properties, are becoming increasingly better understood, and the extended use of such properties as proxy parameters for many processes is foreseen. The following environmental magnetic applications are reviewed: the analysis of paleoclimatic variations in loess and other sediment types, the untangling of sedimentary features in piston cores, and the interpretation of the anthropogenic impact on the environment, in archeological studies and in studies of present-day pollution. The pathway between the provenance area and depositional site is shown to have a crucial impact on the magnetic properties.  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   

Determining the drivers of long‐term aridity variability: a southern African case study          下载免费PDF全文

Manuel Chevalier  Brian M. Chase 《第四纪科学杂志》2016,31(2):143-151

This paper highlights the importance of differentiating between precipitation amount and moisture availability (‘humidity’/‘aridity’) when considering proxy records of climate change. While the terms are sometimes used interchangeably, moisture availability is determined by both (i) precipitation amount and (ii) temperature, through its influence on potential evapotranspiration. As many palaeoenvironmental proxies reflect changes in this water balance rather than purely precipitation amount, it is important to distinguish between the potential relative influences of precipitation and temperature if those records are to be interpreted in terms of climate mechanisms and/or compared with model outputs. As a case study, we explore how precipitation and temperature have determined moisture availability in South Africa's summer rainfall zone over the last 45 000 years. Using quantitative reconstructions of mean annual temperature, summer rainfall amount and an aridity index, our analysis reveals strong spatiotemporal variability in the relative influences of precipitation and temperature on aridity. Temperature is shown to have exerted a considerable and even dominant influence on moisture availability, resulting in elevated humidity during the last glacial period, despite significant reductions in precipitation amount.  相似文献   

闽中沿海若干沉积物样品的孢粉组合   总被引：1，自引：0，他引：1  

吴学忠 《台湾海峡》1994,13(1):94-100

本文选择福建沿海中段莆田，惠安，泉州等地，晚更新世以来１０个露头剖面沉积物样品进行孢粉研究，得出本地区晚更新世以来的１０个孢粉组合，根据＾１４Ｃ测年结果，划分了各孢粉组合所相应的地质时代，探讨了不同地质时代粉组合所反映的古植被，古气候。  相似文献   

闽北沿岸晚第四纪孢粉组合,古植被和古气候   总被引：3，自引：0，他引：3  

陆继军 《海洋地质与第四纪地质》1994,14(1):23-33

福建北部沿岸晚第四纪地层中的孢粉化石含有八个综合孢粉带，即八个古值被和古气候演替阶段。其中阶段１冷而干燥（Ｑ３＾２－１）；阶段２暖而湿润（Ｑ＾２－２）；阶段３冷而干燥（Ｑ３＾３）；阶段４暖而稍湿（Ｑ４＾１）；阶段５暖而稍干（Ｑ４＾１）；阶段６热而湿润（Ｑ４＾２－１）；阶段７温暖略干（Ｑ４＾２－２）；阶段８气候状况接近现代（Ｑ４＾３）。  相似文献