天山冰碛物中的花粉组合及冰期环境   总被引：3，自引：0，他引：3  

阎顺  许英勤 《干旱区地理》1995,18(1):21-26

通过对天山乌鲁木齐河源区和天山南麓台兰河口区、木扎尔特河口区冰碛物中花粉分析，表明在冰期阶段不同区域的花粉组合均以灌木及为主，乔木含量很低，反映冰川所到之处距云杉林均大于５ｋｍ。冰期阶段，天山南北坡环境差异明显，北坡以草原为主，南麓带以荒漠草原为主，山地气候较现代干燥，山麓地带较现代略湿润。  相似文献   

华南末次冰期盛期最低海面问题   总被引：9，自引：0，他引：9  

黄镇国  徐起浩 《地理学报》1995,50(5):385-393

本文从陆架残留砂、水下海滩岩、陆架残留地貌、海底岩芯、珊瑚礁沉积间断、陆域侵蚀沉积反映等方面，综合考虑海面下降、陆架均衡沉降、构造活动、海流潮流波浪的再造作用等多种因素，认为华南末次冰期盛期的最低海南可能是－８０ｍ左右。  相似文献   

三万年来可可西里地区湖泊环境演化序列   总被引：9，自引：0，他引：9       下载免费PDF全文

胡东生  陈克造 《地质科学》1994,29(4):329-338

可可西里地区位于青藏高原的腹地,以可可西里地区综合科学考察资料为依据,通过湖泊沉积物层序-年龄事件与近代冰川活动遗迹的对比研究,建立了环境变化的物性柱综合剖面及其时序性,将32000aB.P.以来可可西里地区湖泊环境演化序列划分为7个旋,为深入认识青藏高原环境变迁提供新的信息。  相似文献   

国外末次冰期极盛期以来环境演变研究的主要特点     

任国玉 《地球科学进展》1994,9(2):65-69

国外对更新世末次冰期极盛期(LGM)以来环境演变的研究出现了一些新的趋势和特点。本文对此进行了归纳与分析，并指出它们对国内第四纪研究工作的启示意义。  相似文献   

漓江流域末次冰期以来气候环境变化研究进展     

殷建军  汪智军  唐伟  蓝高勇  李建鸿 《地质论评》2021,67(1):67020016-67020016

为更好地认识漓江流域过去气候环境变化,更好服务于漓江流域未来气候环境预测、生态环境建设及资源环境可持续发展,本文对漓江流域末次冰期以来的气候环境研究现状进行了总结和综述。总结了年代学、现代过程研究、古气候环境重建和古人类演化方面的进展及存在的问题,并对下一步的研究方向进行了分析和探讨。希望能促进华南地区过去气候环境变化研究,并对经济社会可持续发展提供借鉴和参考,助力桂林可持续发展创新示范区建设。  相似文献   

南华系建系问题探讨   总被引：6，自引：0，他引：6  

张启锐  储雪蕾 《地层学杂志》2007,31(3):222-228

南华系的研究与关于成冰系的研究配合不多,把南华系简单地理解为原震旦系下统,侧重于原震旦系下统底界年龄的测定,把国外给定的关于"成冰系"的起始年龄值(即850Ma)看得过重,忽略了它的不确定性。对于作为南华系主体的新元古代冰期地层的研究比较薄弱,与国际冰川沉积学研究水平差距大。为此,有必要根据界线层型剖面的要求开展建系工作,重点深入研究新元古代冰川沉积地层的基本特征,包括层序地层学、同位素地层学、磁性地层学、岩石地层学、化学地层学、生物地层学和年代地层学等,明确其内涵,寻找全球对比的界线标志。建议以贵州黎平肇兴剖面为代表开展候选层型剖面和层型点所需内容研究。  相似文献   

云南千湖山第四纪冰川发育特点与环境变化   总被引：2，自引：0，他引：2  

张威  刘蓓蓓  李永化  冯俊  张兵  王志麟  李大鹏 《地理学报》2012,67(5):657-670

千湖山(4249 m) 是横断山脉中段保存确切第四纪冰川遗迹的山地,受西南季风影响强烈。对于研究青藏高原边缘山地冰川发育与气候和构造之间的耦合关系具有十分重要的科学意义。在千湖山海拔3500 m以上保存着古冰川侵蚀与堆积地貌,冰川发育依托海拔4000~4200 m的夷平面及其支谷地形。冰川形态类型为小型的冰帽以及由冰帽边缘溢流进入山谷的山谷冰川。应用相对地貌法,光释光(OSL) 年代测试,本文确定千湖山地区的冰进系列:末次冰盛期(LGM,22.2±1.9 ka BP)、末次冰期中期(MIS3b,37.3±3.7 ka BP、45.6±4.3 ka BP45.6±4.3 ka BP)、末次冰期早期(MIS4)。千湖山冰川前进规模是MIS3b 阶段大于末次冰盛期,主要原因是末次冰期中期(MIS3b) 时本区气候相对湿润,而在末次冰盛期(MIS2) 时气候条件比较干燥。在总体相似的气候背景下,与横断山其它存在多期次冰川作用的山地相比,千湖山只发育末次冰期的冰川作用,其差异性说明该地区冰川发育主要受山体构造抬升控制。  相似文献   

PUNCTUATED DRAINAGE OF AN ICE-DAMMED QUATERNARY LAKE IN SOUTHERN SOUTH AMERICA     

C.M. BELL 《Geografiska Annaler: Series A, Physical Geography》2008,90(1):1-17

A chain of east‐west elongated lakes fringes the eastern flank of the Andes Mountains between 39 and 52°S in southern Chile and Argentina. These deep lakes fill valleys left by the retreat of outlet glaciers of the Patagonian Icefield about 16000 years ago. Two of the lakes, Lago General Carrera/Buenos Aires and Lago Cochrane, represent the shrunken remnants of a much larger lake (called here the predecessor lake) that developed in a moat alongside the icefield. A series of seven stepped lacustrine braid deltas on the southeastern shore of Lago General Carrera/Buenos Aires mark the progressive, punctuated drainage of the predecessor lake. The deltas were formed by the build‐out of fans of sand and gravel into the lake. They have the form of Gilbert deltas, with virtually flat subaerial topset beds and steeply inclined subaqueous foreset beds. The exposed delta fronts are marked by a series of small terraces produced by wave erosion during falling lake levels. On either side of the fans are embayments with beaches formed by deposition in the lee of the pro‐grading fans. These embayments are filled with ridges of well‐sorted gravel deposited by wave‐driven long‐shore drift. About 13 000 years ago the regional drainage underwent a remarkable change. Rivers flowing eastwards into the Atlantic reversed their direction to flow westwards through the Andes Mountains and into the Pacific Ocean. The watershed moved some 200 km to the east. The cause of this change, and the falling lake levels, was melting of the Patagonian Icefield. As the ice retreated the icefield split into north and south components. This broke the ice dam that impounded the western end of the predecessor lake. The stepped, progressive fall of the lake level suggests that as the ice melted a series of lower overflow sills of hard rock were exposed. Each of the major episodes of sudden drop in lake level was followed by a long period of up to thousands of years when lake level remained constant. Terraces on the delta fronts indicate that each major episode of fall in the lake level was punctuated by up to ten minor episodes possibly representing major storm events or annual cycles of freezing and melting, blocking the overflow sills.  相似文献   

THE LAST GLACIATION OF SHETLAND, NORTH ATLANTIC   总被引：1，自引：0，他引：1  

N.R. GOLLEDGE  A. FINLAYSON  T. BRADWELL  J.D. EVEREST 《Geografiska Annaler: Series A, Physical Geography》2008,90(1):37-53

Evidence relating to the extent, dynamics, and relative chronology of the last glaciation of the Shetland Islands, North Atlantic, is presented here, in an attempt to better illuminate some of the controversies that still surround the glacial history of the archipelago. We appraise previous interpretations and compare these earlier results with new evidence gleaned from the interpretation of a high resolution digital terrain model and from field reconnaissance. By employing a landsystems approach, we identify and describe three quite different assemblages of landscape features across the main islands of Mainland, Yell and Unst. Using the spatial interrelationship of these landsystems, an assessment of their constituent elements, and comparisons with similar features in other glaciated environments, we propose a simple model for the last glaciation of Shetland. During an early glacial phase, a coalescent British and Scandinavian ice sheet flowed approximately east to west across Shetland. The terrestrial land‐forms created by this ice sheet in the north of Shetland suggest that it had corridors of relatively fast‐flowing ice that were partially directed by bed topography, and that subsequent deglaciation was interrupted by at least one major stillstand. Evidence in the south of Shetland indicates the growth of a local ice cap of restricted extent that fed numerous radial outlet glaciers during, or after, ice‐sheet deglaciation. Whilst the absolute age of these three landsystems remains uncertain, these new geo‐morphological and palaeoglaciological insights reconcile many of the ideas of earlier workers, and allow wider speculation regarding the dynamics of the former British ice sheet.  相似文献   

POST-DRAINAGE ICE DAM RESPONSE AT LAKE MERZBACHER, INYLCHEK GLACIER, KYRGYZSTAN   总被引：1，自引：0，他引：1  

C. MAYER  A. LAMBRECHT  W. HAGG  A. HELM  K. SCHARRER 《Geografiska Annaler: Series A, Physical Geography》2008,90(1):87-96

The Inylchek glacier system in Central Tian Shan, Kyrgyzstan, comprises a large glacier‐dammed lake which usually drains once a year through a subglacial drainage system. Detailed GPS measurements on the ice dam and the analysis of Aster scenes from several subsequent years provide insight into the post‐drainage dam response and the changed ice dynamic conditions. We demonstrate that during high water levels in the lake a large part of the ice dam is afloat, lifting the ice surface up to almost 20 m in the central dam region. During this phase of extensive flotation strong calving is facilitated, which is supported by the high density of ice debris in the lake. In general, surface ice velocities are about 1.5‐2 times higher during summer than winter. Closer to the lake, however, ice velocities increase considerably after the drainage event, showing values more than three times the annual mean. The increased mass flux during the phase of high lake level needs to be compensated by replenishment of the lost ice from the dam. Therefore the ice velocities show compressive flow during the remaining part of the year. These results show that Southern Inylchek glacier is strongly influenced by the existence of the lake.  相似文献