Der nacheiszeitliche Bergsturz im Kandertal (Schweiz): Alter und Auswirkungen auf die damalige Umwelt     

Willy Tinner  Petra Kaltenrieder  Michael Soom  Peter Zwahlen  Martin Schmidhalter  Adriano Boschetti und Christian Schlüchter 《Eclogae Geologicae Helvetiae》2005,98(1):83-95

Zusammenfassung. Beim Bau des neuen AlpTransit Lötschberg Basistunnels wurden unter murgangartig verschwemmten Ablagerungen der alten Bergsturzmasse des Kandertals Stillwasserablagerungen mit zahlreichen organischen Resten und Torflagen gefunden. Die ¹⁴C-datierten Resultate der Pollen, Makrorest-, Holz- und Holzkohleanalysen ermöglichten eine Rekonstruktion der lokalen bis regionalen Umweltgeschichte. Ein Gewässer, vermutlich ein kleiner See, begann beim Tellenfeld in Frutigen um 8800 kal. Jahre v. Chr. zu verlanden. In der näheren Umgebung wuchs von 8800 v. Chr. bis 8000 v. Chr. ein Föhrenwald (Pinus silvestris), der reichlich mit Hasel (Corylus avellana) und anderen wärmeliebenden Gehölzen (Ulmen, Linden, Eichen; Ulmus, Tilia, Quercus) und Birken (Betula) durchsetzt war. Diese für die Nordalpen sehr frühe Bedeutung der Hasel ist durch ¹⁴C-datierte Corylus-Nussfragmente (9310±50 ¹⁴C BP, 8722–8337 v. Chr.) belegt. Nach 8500 v. Chr. drängte die Hasel die Waldföhre allmählich zurück. Auf Grund der paläoökologischen Resultate muss angenommen werden, dass die Wälder um 7600 v. Chr. durch ein katastrophales Ereignis stark gestört wurden. Als Reaktion darauf kam es zu einer starken Zunahme der Waldbrände und es breiteten sich zuerst Farne und Gräser sowie wenig später Waldföhren aus. Das Gewässer wurde um 7100 v. Chr. durch verschwemmtes Bergsturzmaterial zerstört. Der geomorphologische Befund deutet darauf hin, dass diese Ereignisse in engem Zusammenhang mit dem Hauptbergsturz im Kandertal stehen, der aussergewöhnliche Ausmasse hatte (ca. 800 Millionen m³). Die Zerstörung der lokalen ökosysteme als Folge des Bergsturzes um 7600–7100 v. Chr. fiel in ein frühes holozänes Wärme- und Sonneneinstrahlungsmaximum, in dem es, wie vorgängige Untersuchungen in den Alpen und in anderen Gebirgen belegen, zu überdurchschnittlich vielen Hanginstabilitäten kam.

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During the construction of the new AlpTransit railway line wetland sediments containing numerous fossils and peat layers were found below rockfall masses transported by debris flows. Radiocarbon-dated results of pollen, macrofossils, wood, and charcoal along with radiocarbon dating analysis were used to reconstruct the environmental history of the site. The wetland, originally probably a small lake, started to accumulate sediments at about 8800 cal. yr BC at Frutigen Tellenfeld. A pine forest (Pinus silvestris) admixed with hazel (Corylus avellana), other thermophilous arboreal taxa (Ulmus, Tilia, Quercus) and birch (Betula) grew in the surroundings of the lake. This very early importance of hazel is documented by ¹⁴C-dated Corylus nut fragments (9310±50 ¹⁴C yr BP, 8722–8337 yr BC). After 8500 BC hazel expanded on the costs of pine. The palaeo records suggest that the forests were severely disturbed by a catastrophic event at around 7600 BC. In response, forest fires strongly increased and ferns and grasses expanded and then pine stands established. At ca. 7100 BC the lake was abruptly destroyed by rockfall masses transported by a debris flow. The geomorphic situation suggests that these events were closely related with the main Kander valley rockfall, which had an exceptional size (800 millions m³). Local environmental catastrophes as a consequence of the rockfall at 7600–7100 BC occurred during an early Holocene thermal and solar irradiation maximum. As documented by previous investigations, this period was characterised by pronounced slope instabilities in the Alps and elsewhere.

Manuskript eingegangen 9. Februar 2004 Revidierte Fassung angenommen 17. Januar 2005  相似文献   

Late Quaternary deformation history of the volcanic edifice of Panarea,Aeolian Arc,Italy     

F. Lucchi  C. A. Tranne  N. Calanchi  P. L. Rossi 《Bulletin of Volcanology》2007,69(3):239-257

A series of raised palaeoshorelines is documented along the emergent coastal slopes of Panarea and surrounding islets at elevations of 115 (palaeoshoreline Ia) and 100 m a.s.l. (Ib), 62.5 m (II), 35 m (III), 12 m (IV), 10–12 (Va) and 5 m (Vb). According to stratigraphic constraints and cross-cutting relationships, these palaeoshorelines are correlated with discrete high sea-level stillstands during marine oxygen-isotope stages (MIS) 5e, 5c, 5a and 3. Coastal elevation changes suggest the occurrence of a long-term, sustained uplift trend of the volcanic edifice since the last interglacial (last 124 ka). The uplift rates are not constant but display a progressive deceleration from maximum values of 1.5–1.58 m/ka, in the period between 124 and 100 ka, down to the lowest values of 0.66–0.69 m/ka, which tend to be constant starting from 81 ka BP. The long-term deformation pattern of Panarea suggests that a transitory, volcano-related component of uplift interplayed with the regional tectonic component affecting the sub-volcanic basement, which has undergone a persistent and widespread uplift since the mid-Pleistocene. The volcano-related component of uplift, prevailing between 124 and 100–81 ka, is interpreted as the result of visco-elastic deformation mechanisms which characterize the progressive re-equilibration of the shallow magmatic system following the incoming quiescence of the volcanic edifice. The long-term uplift values at Panarea are higher than in the main portion of the western-central Aeolian Arc, where a mean uplift rate of 0.34 m/ka was estimated since the last interglacial (last 124 ka). Such a pattern of deformation on a regional scale may be a response to active deformation processes connected with the southeastward rollback of the subducting Ionian slab which is still active only in correspondence with the eastern sector of the Aeolian Arc (including Panarea). In the short-term, a localized submergence trend has been documented at the nearby islet of Basiluzzo for the last 2,000 years, likely connected to neo-tectonic movements along main NE–SW trending faults.  相似文献   

库车坳陷东秋里塔格断裂晚第四纪活动和滑动速率   总被引：1，自引：0，他引：1       下载免费PDF全文

吴传勇  沈军  陈建波  谢天  李军  向志勇  宋正娜  王翠 《地震工程学报》2007,29(2):129-132

东秋里塔格断裂是库车坳陷内活动最为强烈的断裂之一,断错了波斯坦托克拉克河两岸的各级阶地。利用全站仪对河西岸的阶地变形进行了精确测量,得到Ⅰ、Ⅱ、Ⅲ级阶地形成以来东秋里塔格断裂的垂直断错量分别为12.5 m、20 m和24.5 m,并根据前人资料和区域类比的方法对各级阶地年龄进行了估计,计算得到晚第四纪以来该断裂的平均垂直滑动速率为1 mm/a左右,所引起的地壳缩短速率为(1.97~2.13)mm/a。  相似文献   

Quaternary stress regime change in the Hatay region (SE Turkey)   总被引：1，自引：0，他引：1  

Semir Över  Ulvi Can Ünlügenç  Olivier Bellier 《Geophysical Journal International》2002,148(3):649-662

  相似文献   

银川盆地CK1孔第四纪孢粉资料的数值分析   总被引：1，自引：0，他引：1  

杨振京  刘志明  彭朝华  童国榜  阳小兰 《地理与地理信息科学》2001,17(2):71-76,91

以银川盆地北部重点井CK1孔 (深 30 0 .39m)第四纪孢粉分析为例 ,采用R型因子分析、R型系统聚类、模糊分类等数值分析方法进行了孢粉组合带的划分及孢粉资料数值分析 ,根据对应分析结果进行古环境解释  相似文献   

The Geography of Mutual Fund Assets     

William Graves 《The Professional geographer》1998,50(2):243-255

Mutual funds are the primary investment vehicle for individual retirement savings, but the spatial aspects of mutual fund investments have not been examined. This paper discusses the characteristics of the mutual fund industry and compares them to other financial industries. Previous studies of the financial industry and quaternary location theory are used to formulate three hypotheses predicting the distribution of mutual fund assets: (1) mutual fund assets will concentrate in the largest urban centers; (2) mutual fund assets will become increasingly concentrated in financial centers over the 1986-1996 period; and (3) the distribution of mutual fund assets will be similar to the distribution of other financial activities. Examination of mutual fund asset data from 1986 and 1996 did not fully support any of the three hypotheses. These findings suggest that the standard elements of quaternary location theory may need to be reevaluated.  相似文献   

不同链长烷基季铵离子在蒙脱石层间域内排列方式的对比   总被引：13，自引：2，他引：13  

朱建喜  何宏平  郭九皋  杨丹  谢先德 《矿物学报》2003,23(3):193-198

选用含不同烷基长链的三种季铵盐——十二烷基三甲基溴化铵(DDTMAB)、十四烷基三甲基溴化铵(TDTMAB)、十六烷基三甲基溴化铵(HDTMAB)，对河北钠交换蒙脱石进行了有机柱撑实验，以X射线衍射分析方法对实验产物进行了对比研究。结果表明，由于烷基链中所含的碳原子数目不同，三种长链季铵离子对蒙脱石的柱撑效果不同，DDTMA^ 在蒙脱石层间域内可形成平卧单层、平卧双层和假三层三种不同排列方式；TDTMA^ 与DDTMA^ 在低浓度条件下形成的前两种排列方式相同，而第三种则不同，为倾斜单层排列；HDTMA^ 有机柱撑产物中除了具有前两者的排列方式外，还具有倾斜双层排列方式。不同排列方式的复合产物可以多相共存。此外，随着柱撑剂浓度的增加，三种长链烷基季铵离子在蒙脱石层间域内的排列方式及其演化是不同的。  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   

Environmental Characteristics of Lake Tecocomulco, northern basin of Mexico, for the last 50,000 years     

Margarita Caballero  Socorro Lozano  Beatriz Ortega  Jaime Urrutia  Jose Luis Macias 《Journal of Paleolimnology》1999,22(4):399-411

Paleoenvironmental studies have documented the late Pleistocene to Holocene evolution of the lakes in the central and southern parts of the basin of Mexico (Texcoco and Chalco). No information was available, however, for the lakes in the north-eastern part of this basin. The north-eastern and the central and southern areas represent, at present, different environmental conditions: an important gradient exists between the dry north and the moister south. To investigate the late Pleistocene to Holocene characteristics of the north-eastern lakes in the basin of Mexico two parallel cores (TA and TB) were drilled at the SE shore of Lake Tecocomulco. Stratigraphy, magnetic properties, granulometry, diatom and pollen analyses performed on these sediments indicate that the lake experienced a series of changes between ca. > 42,000 yr BP and present. Chronological control is given by five radiocarbon determinations. The base of the record is represented by a thick, rhyolitic air-fall tephra that could be older than ca. 50,000 yr BP. After this Plininan event, and until ca. 42,000 yr BP, Lake Tecocomulco was a moderately deep, freshwater lake surrounded by extended pine forests that suggest the presence of cooler and moister conditions than present. Between ca. 42,000 and 37,000 yr BP, the lake became shallower but with important fluctuations and pollen suggests slightly warmer conditions. Between ca. 37,000 and 30,000 yr BP the lake experienced two relatively deep phases separated by a dry interval. A second Plinian eruption, represented in the sequence by a dacitic an air-fall tephra layer dated at 31,000 yr BP, occurred in the area by the end of this dry episode. Between ca. 30,000 and 25,7000 yr BP Tecocomulco was a fresh to slightly alkaline lake with a trend towards lower level. After ca. 25,700 yr BP very low lake levels are inferred, and after ca. 16,000 yr BP the data indicate the presence of a very dry environment that was persistent until the middle Holocene. After 3,500 yr BP lacustrine conditions were re-established and the vegetation cover shows a change towards higher percentages of herbaceous taxa.  相似文献   

横断山地区的黄土及意义   总被引：3，自引：0，他引：3  

汪阳春  柴宗新 《山地学报》1999,17(4):300-304

研究了横断山地区的黄土的分布特点和理化特征,根据黄土的热释光测年数据并结合冰期划分,横断山地区的黄土主要开始沉积于大约１０万ａ前的晚更新世,要晚于青藏高原冰冻圈的极盛期,这种滞后的效应是由于高原隆起的阶段性和差异性所引起的。  相似文献