A Late Quaternary lake record from the Qilian Mountains (NW China): lake level and salinity changes inferred from sediment properties and ostracod assemblages

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.     

A Middle Pleistocene Glaciation Record from Lacustrine Sediments in the Western Tibetan Plateau and Discussion on Climate Change

The Tibetan Plateau is an important area for studying global climate change, but the answers to many scientific problems remain unknown. Here, we present new information from the lacustrine sedimentary record in the western Tibetan Plateau, related to the third most-recent glaciations. Continuous sediment data, including sporopollen, particle size, total organic carbon, mass susceptibility, CaCO3, CaSO4, BaSO4 contents and chronological data, were reconstructed and revealed that climate and environmental conditions obviously and distinctly changed between 600 and 700 thousand years ago. In comparison, the data obtained from the Guliya ice core in this area also corresponds to the global glacial climatic characteristics recorded in basin sediments in the eastern and southeastern regions of the plateau and to the information obtained from ice cores in the Antarctic and Arctic regions. In this study, we conclude that the main reason for the glaciations and new tectonic movement must be a geomagnetic polarity reversal 774 thousand years ago (from Matuyama to Brunhes). Indeed, the results of this study suggest that the described reversal event might have influenced the current global climate pattern and will continue to impact climatic changes in the future.     

闽南—台湾浅滩渔场微型硅藻的分类研究

利用透射电镜（ＴＥＭ）研究闽南－台湾浅滩渔场的微型硅藻时,鉴定出１４个在我国首次的种类,它们是：极小曲壳藻（Ａｃｈｎａｎｔｈｅｓ ｍｉｎｕｔｉｓｓｉｍａ）,分岐双壁藻（Ｄｉｐｌｏｎｅｉｓ ｄｉｖｅｒｇｅｎｓ）、槌棒脆杆藻（Ｆｒａｇｉｌａｔｉａ ｏｐｅｐｈｏｒｏｉｄｅｓ）、微细脆杆藻（Ｆｒａｇｉｌａｒｉａ ａｔｏｍｕｓ）、折断舟形藻（Ｎａｖｉｃｕｌａ ｆｒａｃｔａ）、虫瘿舟形藻（Ｎａｖｉｃｕｌａｇａ     

关于天然设计地震波的研究

本文讨论了天然设计地震波的调整问题.通过给出的工程计算实例,研究了产生天然设计地震波所采用技术的可行性和合理性.文中对塔吉克斯坦共和国杜尚别市鸟巢大厦结构隔震设计所需要的天然设计地震波进行了较为详细的研究,提供的结果可满足设计需求.同时文中还对天然设计地震波调整技术存在的问题进行了初步的讨论.     

谈谈地质资料档案的标准化著录

在简要论述地质资源档案标准化著录含义的基础上，详细阐述了地质资料档案的著录项目，著录根据，著录用标识符及使用说法，著录条目格式，著录标目法，以及题名目录，责任者目录，主题目录，分类目标的编制。意在引导地质资料档案管理部门，进一步做好地质资料档案著录这一基础性工作。     

净全辐射异常值的审核处理

针对近年来在省级质量控制数据R文件时净全辐射出现的问题,利用<地面自动站观测资料三级质量控制软件--省级软件>对净全辐射质量控制时数据异常原因进行举例分析,并采用人机交互方法对经质量控制后系统自动生成的疑误信息进行综合分析判断,同时结合有关规定和问题解答提出相应的处理方法,以确保净全辐射观测数据的真实、准确、可靠,进而为业务科研工作提供科学的、准确的数据.     

A multi-proxy lacustrine record of Holocene climate change on northeastern Baffin Island, Arctic Canada

Reconstructions of past environmental changes are critical for understanding the natural variability of Earth's climate system and for providing a context for present and future global change. Radiocarbon-dated lake sediments from Lake CF3, northeastern Baffin Island, Arctic Canada, are used to reconstruct past environmental conditions over the last 11,200 years. Numerous proxies, including chironomid-inferred July air temperatures, diatom-inferred lakewater pH, and sediment organic matter, reveal a pronounced Holocene thermal maximum as much as 5°C warmer than historic summer temperatures from 10,000 to 8500 cal yr B.P. Following rapid cooling 8500 cal yr B.P., Lake CF3 proxies indicate cooling through the late Holocene. At many sites in northeastern Canada, the Holocene thermal maximum occurred later than at Lake CF3; this late onset of Holocene warmth is generally attributed to the impacts of the decaying Laurentide Ice Sheet on early Holocene temperatures in northeastern Canada. However, the lacustrine proxies in Lake CF3 apparently responded to insolation-driven warmth, despite the proximity of Lake CF3 to the Laurentide Ice Sheet and its meltwater. The magnitude and timing of the Holocene thermal maximum at Lake CF3 indicate that temperatures and environmental conditions at this site are highly sensitive to changes in radiative forcing.     

Fire and drought as drivers of early Holocene tree line changes in the Peruvian Andes

Three pollen and charcoal records from three lakes lying at 3400 m elevation in southern Peru provided a record of landscape change spanning the last ca.18 000 cal. a BP. The tree line lay close to the site between ca. 16 000 and 12 000 cal. a BP, with Polylepis woodlands growing near the lakes. Progressively drying conditions led to increased fire after 12 000 cal. a BP, coinciding with a decline in Polylepis cover and Andean forest relicts as puna grasslands expanded. A strong decrease in the rate of sediment deposition between ca. 12 000 and ca. 4400 cal. a BP was interpreted to indicate the presence of sedimentary hiatuses. With the return of wet conditions after 4400 cal. a BP, forests did not reassemble around the lakes. Instead, fire‐maintained grasslands dominated the landscape. Humans probably induced the intensified fire activity during the late Holocene and thereby deflected local successions. The modern fragmented landscape, with Polylepsis woodlands existing in fire‐resistant pockets above the general limit of the Andean tree line, resulted from the intensification of human land use practices during the last 4400 cal. a BP. Copyright © 2011 John Wiley & Sons, Ltd.     

The role of diagenetic carbonate concretions in the preservation of the original sedimentary record

The Upper Cretaceous organic rich limestones and marls of the Tarfaya basin of southwest Morocco contain numerous calcite concretions, which formed during early diagenesis. Relative textural similarities are observed both in the concretions and in the host sediments. However, the biological content of the concretions is considerably higher than in the host marls and limestones. Evidence for fossil dissolution in the host marls, and the absence of concretions in some fossil-rich zones, suggest that the difference in fossil abundance between the concretions and host rock is a function of dissolution, rather than preferential precipitation in fossil-rich areas. Consequently, the carbonate concretions appear to represent the 'memory' of the sediment and allow quantification of the original biological components and are potential tools for estimating the original biological material deposited in the soft sediments.     

地震图数字化技术中的倾斜校正和波形分割

重点阐述了在对模拟地震图进行数字化处理过程中，利用图中水平线信息完成倾斜校正以及利用中值滤波增强信号、自适应提取信号的波形分割技术。