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坝上高原安固里淖粒度年纹层与环境变化 总被引：9，自引：2，他引：9
在安固里淖湖心区获取一未扰动沉积物样柱，分析发现了由冬季风搬运物与湖心沉积共同形成的粒度年纹层，建立了纹层年表，恢复了安固里淖湖区8507aB.P，以来的环境变化过程。8507-5429aB.P。冬季风活动较弱，后期的所波动；5429-3244aB.P.冬季风活动较强，3244-2494aB.P。冬季风活动减弱；2494-1165aB.P。冬季风活动略有增强；1165aB.P以来，冬季风活动减弱。安固里小淖粒度年纹层反映的冬季风变化情况与我国北方地区同期的环境变化和海平面变化有很好的对应关系。 相似文献
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Melanie A. Riedinger Miriam Steinitz-Kannan William M. Last Mark Brenner 《Journal of Paleolimnology》2002,27(1):1-7
Lithostratigrahic and mineralogic analyses of sediments from hypersaline Bainbridge Crater Lake, Galápagos Islands, provide evidence of past El Niño frequency and intensity. Laminated sediments indicate that at least 435 moderate to very strong El Niño events have occurred since 6100 14C yr BP (7130 cal yr BP), and that frequency and intensity of events increased at about 3000 14C yr BP (3100 cal yr BP). El Niño activity was present between 6100 and 4000 14C yr BP (4600 cal yr BP) but infrequent. The Bainbridge record indicates that there has been considerable millennial-scale variability in El Niño since the mid-Holocene. 相似文献
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Jeannine-Marie St. Jacques Brian F. Cumming John P. Smol 《Journal of Paleolimnology》2008,40(2):733-744
We developed a fast, inexpensive, statistically rigorous method of varve verification that uses prospective varve layer-splitting
and seasonal pollen deposition. This method can be used on any sediment that contains seasonally deposited pollen, and avoids
the need for radio-isotopic, optical, or thermoluminescence dating. The method uses a χ2 test and non-parametric regression, together with recorded plant bloom times from pollen traps, to assess the differences
in pollen abundances in light/dark (i.e. summer/winter-spring) sediment layers. A statistical test is required because such
seasonally deposited data are inherently noisy, with a low signal-to-noise ratio. To illustrate this approach, visible laminations
of Lake Mina, Minnesota, USA, were assessed in two separate regions of a core spanning 900 years. Results show that the laminations
were deposited annually. 相似文献
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Meromixis has several powerful effects on lakes, yet there is no single definitive sediment indicator of meromixis. In this study three sediment indicators of meromixis were compared in Brownie Lake, Minneapolis, Minnesota, a small eutrophic lake that became meromictic around 1925. The results show that in Brownie the onset of laminations and changes in the iron to manganese ratio most likely occurred before the development of permanently anoxic bottom water and that changes in the diatom assemblage occurred later, most likely only when meromixis was well developed.This is the 11th 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
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The sustainable management of erodible pastoral hill country is a major focus of land use research in New Zealand. A multi-disciplinary study, using a high resolution lake sedimentation record, is being conducted to determine the role that cyclonic storms and natural and human-induced vegetation changes play in the erosion history of a landslide-prone hill country watershed.Sediment cores from Lakes Tutira and Waikopiro in northern Hawke's Bay were analysed to construct the magnitude-frequency history of storm-induced erosion since European settlement. Pulses of sediment representing individual storms can be clearly identified and are correlated to a storm history derived from analysis of a 93 year daily rainfall record. Correlation and dating are confirmed by pollen and diatom analysis,137Cs distribution, tephrochronology and reference to a well documented land use history. Annually laminated, organic rich deposits, which occur in the uppermost sediments and represent the annual decomposition of biogenic material associated with eutrophication, are also used to confirm the chronology.A high correlation was found between storm sediment thickness and total storm rainfall (R2=0.8). Although sediment producing storms (>150 mm) occur on a near annual basis, the two largest storms (>600 mm) contributed 54% of the total sediment thickness.The presence of well defined storm sediment pulses has enabled the lake storage component of a sediment budget to be calculated for Cyclone Bola (1988), the most recent and largest rainstorm on record. The integration of this budget with the storm-magnitude-frequency history will be used to develop watershed-based models to predict the impacts of land use changes and the erosion response to climate scenarios.This is the third paper in a series of papers published in this issue on high-resolution paleolimnology. These papers were presented at the Sixth International Palaeolimnological Symposium held 19–21 April, 1993 at the Australian National University, Canberra, Australia. Dr A. F. Lotter and Dr. M. Sturm served as guest editors for these papers. 相似文献
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沱沱河盆地通天河剖面渐新世雅西措群发现一套产于湖泛过程中的柱状叠层石。通过对叠层石纹层形态和显微组构的研究,发现这些叠层石具有典型的富藻纹层和富屑纹层交替的显微结构特征,发育三级生长节律,纹层对之间渐变接触,纹层带之间间断明显。采用激光微区取样的方法,针对4块样品的8个纹层对,系统采集了16对碳氧同位素数据,结果是富藻纹层同位素值整体上均高于富屑纹层,正相关性明显。这表明富藻纹层生长时期气候炎热湿润,富屑纹层生长时期相对寒冷干燥。认为湖相叠层石生长受周期性气候变化的控制,其韵律纹层记录了丰富的古气候信息。 相似文献
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ＡＮＮＵＡＬ ＬＡＭＩＮＡＴＩＯＮＳ ＩＮ ＴＨＥ ＳＥＤＩＭＥＮＴＳ ＯＦ ＨＯＮＧＦＥＮＧ ＬＡＫＥ， ＣＨＩＮＡＡＮＮＵＡＬＬＡＭＩＮＡＴＩＯＮＳＩＮＴＨＥＳＥＤＩＭＥＮＴＳＯＦＨＯＮＧＦＥＮＧＬＡＫＥ，ＣＨＩＮＡ￥ＷｕＦｅｎｇｃｈａｎｇ；Ｗａ... 相似文献
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