The evolution of the terrestrial-terminating Irish Sea glacier during the last glaciation     

Richard Christopher Chiverrell  Geoff Stephen Powell Thomas  Matthew Burke  Alicia Medialdea  Rachel Smedley  Mark Bateman  Chris Clark  Geoffrey A. T. Duller  Derek Fabel  Geraint Jenkins  Xianjiao Ou  Helen Marie Roberts  James Scourse 《第四纪科学杂志》2021,36(5):752-779

Here we reconstruct the last advance to maximum limits and retreat of the Irish Sea Glacier (ISG), the only land-terminating ice lobe of the western British Irish Ice Sheet. A series of reverse bedrock slopes rendered proglacial lakes endemic, forming time-transgressive moraine- and bedrock-dammed basins that evolved with ice marginal retreat. Combining, for the first time on glacial sediments, optically stimulated luminescence (OSL) bleaching profiles for cobbles with single grain and small aliquot OSL measurements on sands, has produced a coherent chronology from these heterogeneously bleached samples. This chronology constrains what is globally an early build-up of ice during late Marine Isotope Stage 3 and Greenland Stadial (GS) 5, with ice margins reaching south Lancashire by 30 ± 1.2 ka, followed by a 120-km advance at 28.3 ± 1.4 ka reaching its 26.5 ± 1.1 ka maximum extent during GS-3. Early retreat during GS-3 reflects piracy of ice sources shared with the Irish-Sea Ice Stream (ISIS), starving the ISG. With ISG retreat, an opportunistic readvance of Welsh ice during GS-2 rode over the ISG moraines occupying the space vacated, with ice margins oscillating within a substantial glacial over-deepening. Our geomorphological chronosequence shows a glacial system forced by climate but mediated by piracy of ice sources shared with the ISIS, changing flow regimes and fronting environments.  相似文献   

Three-dimensional publication mode of Journal of Palaeogeography(Chinese Edition)          下载免费PDF全文

Li Xin-Po  Zhang Xi-Juan  Zheng Xiu-Juan 《古地理学报》2021,22(6):1233-1234

The network technology has provided impetus and channels for the development of sci-tech periodicals and promoted the transformation of the publication mode of Journal of Palaeogeography(Chinese Edition). Through the independent website construction,providing readers with diversified access to articles,diversified communication methods,personalized accurate article push,joining the OSID open science program,etc.,a three-dimensional publication mode adapted to the development of periodicals has been gradually formed.  相似文献   

陇东新近纪红粘土与第四纪黄土地球化学特征及其物源和风化指示意义     

綦琳  乔彦松  刘宗秀  王燕  彭莎莎 《地质力学学报》2021,27(3):475-490

甘肃省平凉市灵台县邵寨镇剖面风尘堆积底界年龄大约为5.23 Ma B.P.,通过对该剖面新近纪红粘土与第四纪黄土-古土壤序列的常量元素、微量元素、Nd同位素的测试,分析其在物源和风化方面的指示意义,发现新近纪红粘土与第四纪黄土具有相似的常量、微量元素UCC标准化曲线和稀土元素球粒陨石标准化曲线,指示二者皆来自广阔的物源区,经过了相似的搬运过程,并在搬运中得到充分混合。新近纪红粘土的MgO、Li、Cs、Bi含量较高,Na₂O、稀土元素La-Lu、Y含量较低。风化参数Na₂O/Al₂O₃、化学风化参数CIA以及Al₂O₃-CaO+Na₂O-K₂O (A-CN-K)图,均显示新近纪红粘土比第四纪黄土经历了更为强烈的风化过程。新近纪红粘土的稳定元素比值(TiO₂/Al₂O₃,SiO₂/Al₂O₃,SiO₂/TiO₂,Zr/Hf,Nb/Ta,Lu/Hf,Y/Ho,Th/Nb和Hf/Nb)、稀土元素总量、轻稀土与重稀土的分异程度、轻稀土内部分异程度、重稀土内部分异程度、Ce和Eu的异常程度、同位素ε_Nd(0) 值等,皆与第四纪黄土无太大差异,指示二者物质来源一致。粒度以及风化强度的差异,可能是导致新近纪红粘土与第四纪黄土常量和微量元素含量差异的主要原因。   相似文献   

中国农业气象模式(CAMM1.0)构建与应用          下载免费PDF全文

马玉平  霍治国  王培娟  俄有浩  邬定荣  房世波  谭凯炎  张祎  孙琳丽  杨建莹  赵俊芳  周梦子  赫迪  徐嘉昕  毛飞  姜朝阳 《应用气象学报》2019,30(5):528-542

为发展适宜中国区域农业种植特点的农业气象模式,基于国外作物生长模拟方法,通过模式机理过程改进或重构以及应用方式革新,建立了中国农业气象模式（Chinese AgroMeteorological Model version 1.0,CAMM1.0）。CAMM1.0利用平均温度和土壤水分改进了作物发育进程模式,利用土壤水分改进了作物叶片光合作用、干物质分配和叶面积扩展过程模式,通过蒸发比法扩展了作物蒸散过程模式;自主建立了基于发育进程的冬小麦株高、基于遥感信息的作物灌溉、遥感数据同化、作物长势与灾害评价等模式。基于互联网技术构造了实时运转平台,主要功能包括作物生长过程实时常规模拟与用户个性化定制模拟。CAMM1.0的部分子模式采用多种方法构造,便于多模式集成。CAMM1.0对作物发育进程、光合过程、株高的模拟效果较好,但对土壤水分变化过程的拟合略差,模拟产量略偏低。CAMM1.0评价淮河流域夏玉米年际干旱减弱而涝渍增加的趋势与实际基本相符。  相似文献   

Simulation and Validation of the Aerosol Optical Thicknessover China in 2006     

ZHANG Hu  ZHANG Min  CUI Zhenlei  WANG Yuesi  XIN Jinyuan 《Acta Meteorologica Sinica》2012,26(3):330-344

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Development,evolution and drainage of glacial Lake Naskaupi during the deglaciation of north‐central Quebec and Labrador     

《第四纪科学杂志》2017,32(8):1121-1137

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三峡水库汛期控制水位及运用条件   总被引：2，自引：2，他引：2       下载免费PDF全文

王俊  郭生练 《水科学进展》1990,31(4):473-480

随着长江上游梯级水库的陆续建成投运，三峡水库的水文情势和功能需求与设计条件相比发生了显著变化，仍维持固定的汛限水位运行已不能适应新形势需求。本文通过辨析三峡水库设计阶段汛限水位的设置条件，挖掘流域洪水特性和洪水遭遇规律，论证三峡水库汛期运行水位动态控制的可行性。结果表明：① 三峡水库设计推求的汛限水位145 m的适用条件是应对流域性大洪水，而流域性洪水发生概率小且特征明显，可以通过水文水情分析提前预判。② 根据流域洪水类型、洪水分期和遭遇规律，预判发生区域性大洪水时，三峡水库6月初至梅雨期结束汛限水位按145 m设置，从梅雨期结束后逐渐提高水位，8月20日后过渡到155 m。③ 在考虑上游水库群联合调度和气象水文预报的配合下，正常年份三峡水库汛期运行水位可在155 m上下浮动，并考虑提前蓄水。④ 三峡水库汛期运行水位动态控制，不会增加防洪风险和库区淤积风险，对中下游江湖关系和水文情势有利，可显著提高发电、航运、生态保护和供水等综合利用效益。  相似文献   

Post glacial lacustrine event sedimentation in an ancient mountain setting: Carboniferous Lake Malanzán (Western Argentina)     

Luis Alberto Buatois  Maria Gabriela Mángano 《Journal of Paleolimnology》1995,14(1):1-22

Lacustrine deposits of the Malanzán Formation record sedimentation in a small and narrow mountain paleovalley. Lake Malanzán was one of several water bodies formed in the Paganzo Basin during the Late Carboniferous deglaciation. Five sedimentary facies have been recognized. Facies A (Dropstones-bearing laminated mudstones) records deposition from suspension fall-out and probably underflow currents coupled with ice-rafting processes in a basin lake setting. Facies B (Ripple cross-laminated sandstones and siltstones) was deposited from low density turbidity currents in a lobe fringe environment. Facies C (Massive or graded sandstones) is thought to represent sedimentation from high and low density turbidity currents in sand lobes. Facies D (Folded sandstones and siltstones) was formed from slumping in proximal lobe environments. Facies E (Wave-rippled sandstones) records wave reworking of sands supplied by turbidity currents above wave base level.The Lake Malanzán succession is formed by stacked turbidite sand lobe deposits. These lobes were probably formed in proximal lacustrine settings, most likely relatively high gradient slopes. Paleocurrents indicate a dominant direction from cratonic areas to the WSW. Although the overall sequence shows a regressive trend from basin fine-grained deposits to deltaic and braided fluvial facies, individual lobe packages lack of definite vertical trends in bed thickness and grain size. This fact suggests aggradation from multiple-point sources, rather than progradation from single-point sources. Sedimentologic and paleoecologic evidence indicate high depositional rate and sediment supply. Deposition within the lake was largely dominated by event sedimentation. Low diversity trace fossil assemblages of opportunistic invertebrates indicate recolonization of event beds under stressed conditions.Three stages of lake evolutionary history have been distinguished. The vertical replacement of braided fluvial deposits by basinal facies indicates high subsidence and a lacustrine transgressive episode. This flooding event was probably linked to a notable base level rise during postglacial times. The second evolutionary stage was typified by the formation of sand turbidite lobes from downslope mass-movements. Lake history culminates with the progradation of deltaic and braided fluvial systems  相似文献   

Inland saline lakes with lagoonal biota: some reflections on the concept and nature of athalassic (non-marine), paralic and marine saline waters     

Jean-Pierre Perthuisot 《International Journal of Salt Lake Research》1995,4(2):79-94

First, some inland basins with lagoonal (or paralic) biota are brieffly described. The different kinds of saline aquatic environments are then defined and the composition of their biota are discussed. Finally, the still unknown microbiogeochemical composition of concentrated inland waters is discussed. Under arid and endorheic conditions, it seems that the wider and the more geologically complex a hydrological basin is, the more biogeochemically similar to seawater is the water of its terminal lake. The evolution of the microbiogeochemical complexity of seawater through geological times is considered.This paper has been the subject of considerable discussion among referees. Not all of the views expressed by the author are accepted by them.  相似文献   

Radiometric dating of lake sediments from Signy Island (maritime Antarctic): evidence of recent climatic change   总被引：4，自引：0，他引：4  

P. G. Appleby  V. J. Jones  J. C. Ellis-Evans 《Journal of Paleolimnology》1995,13(2):179-191

Sediment cores from three lakes (Moss, Sombre and Heywood) in the maritime Antarctic (Signy Island, South Orkney Islands) have been successfully dated radiometrically by²¹⁰Pb and¹³⁷Cs. The core inventories of both fallout radionuclides are an order of magnitude higher than that which can be supported by the direct atmospheric flux at this latitude. The elevated values may be explained by fallout onto the catchment during the winter being delivered directly to the lakes during the annual thaw. Two of the lakes (Sombre and Heywood) show marked increases in sediment accumulation afterc. 1950. This appears to be associated with a documented rise in temperature in the South Orkney Islands, which has caused extensive deglaciation at Signy Island.This is the tenth of a series of papers to be published by this journal following the 20 ^th anniversary of the first application of²¹⁰Pb dating of lake sediments. Dr P.G. Appleby is guest editing this series.  相似文献