Effects of the Little Ice Age on avalanche boulder tongues in the French Alps (Massif des Ecrins)

Lichens of the subspecies Rhizocarpon geographicum s.l were measured on 25 avalanche boulder tongues in the Massif des Ecrins to elucidate the Little Ice Age history of avalanche activity. Results show: (1) an increase of lichen size from the median to the distal zone of deposits, and a decrease from the edges to the centre; (2) three types of lichen settlement. From the uppermost to the median zone, lichens are absent, because avalanche activity is very active. Down‐slope, lichens occur in two different zones: the median zone is colonized by 5–20 mm size lichens on sides of blocks protected from the abrasional action of avalanches, while in the distal zone lichen diameters are largest (>30 mm) and occur on all sides of the blocks. The spatial distribution of the lichens and their size according to elevation make it possible to distinguish different phases during which avalanche activity has increased. At high elevation, the avalanche activity was at a maximum before ad 1650 and between ad 1730 and 1830. During these two periods avalanches had suf?cient magnitude to reach the basal zone of the deposits. At low elevation since ad 1650 the magnitude and frequency of avalanches have declined. Copyright © 2004 John Wiley & Sons, Ltd.     

东阿尔卑斯原-古特提斯构造演化

新生代阿尔卑斯是非洲和欧洲之间的陆陆碰撞造山带。强烈的造山作用使大量前中生代基底出露地表,尽管这些基底被强烈逆冲推覆和走滑叠置,但是仍保留较丰富的前中生代基底演化信息。结合近几年对东阿尔卑斯原-古特提斯的研究,本文梳理和重建了阿尔卑斯前中生代基底的构造格局,认为前阿尔卑斯基底受原特提斯、南华力西洋、古特提斯洋构造体系影响而经历了多期造山过程。新元古代-早古生代的原阿尔卑斯作为环冈瓦纳地块群的组成部分,受原特提斯洋俯冲的制约,是新元古-早古生代环冈瓦纳活动陆缘的组成部分,其中,海尔微-彭尼内基底组成外缘增生系统,包括卡多米期地壳碎片在内的陆缘弧/岛弧以及大量增生楔组成内缘增生系统。早奥陶世瑞亚克洋打开,随后原阿尔卑斯从冈瓦纳陆缘裂离,在泥盆纪-石炭纪受南华力西洋控制,海尔微-彭尼内-中、下奥地利阿尔卑斯从冈瓦纳分离。在早石炭世(维宪期)南阿尔卑斯(或与之相当的冈瓦纳源地块)与北部阿莫里卡地块群拼贴增生于古欧洲大陆南缘,共同组成华力西造山带(广义),华力西期缝合带保留在绍山-科尔山南侧。晚石炭世-早二叠世,阿尔卑斯受古特提斯洋的俯冲影响,在华力西造山带南侧形成安第斯山型活动大陆边缘,古特提斯洋在阿尔卑斯的演化至少持续到早三叠世,消亡遗迹保留在中奥地利阿尔卑斯基底的Plankogel杂岩中。     

Modelling alpine permafrost distribution,Val de Rechy,Valais Alps (Switzerland)

The spatial distribution of the alpine permafrost is modelled in the uppermost part of Val de Rechy (Valais Alps, Switzerland) with the use of a geographical information system (GIS). Two empirical-statistical models are compared and their validity tested by a set of bottom temperature of winter snow (BTS) measurements carried out in the field. One model can simulate the spatial distribution of the permafrost facing ground warming consecutive to climatic change. Local/regional maps of simulated permafrost distribution as presented in this paper can be useful in the context of a preventive approach for natural hazards management.     

Fusulinid biostratigraphy of the Lower Permian Zweikofel Formation (Rattendorf Group; Carnic Alps,Austria) and Lower Permian Tethyan chronostratigraphy

The Zweikofel Formation of the Rattendorf Group in the Carnic Alps (Austria) is 95–102 m thick and consists of a cyclic succession of thin‐ to thick‐bedded fossiliferous limestone and intercalated thin intervals of siliciclastic sediment. The siliciclastic intervals were deposited in a shallow marine nearshore environment. The variety of carbonate facies indicates deposition in a shallow neritic, normal‐saline, low‐ to high‐energy environment. The Zweikofel Formation is characterized by a paracyclic vertical arrangement of facies and represents sedimentary sequences that are not well understood elsewhere in the Tethys. Fusulinids and conodonts from the upper Grenzland and Zweikofel formations in the Carnic Alps clearly suggest that what has been called ‘Sakmarian’ in the Tethys includes both the Sakmarian and Artinskian stages of the Global Time scale. Fusulinids from the lower part of the Zweikofel Formation at Zweikofel closely resemble those of the Grenzland Formation and approximately correlate with the upper part of the Sakmarian and lower part of the Artinskian of the Global Time scale. The upper part of the Zweikofel Formation correlates approximately with the lower‐middle (?) parts of the Artinskian Stage of the Global Time scale. A new regional Hermagorian Stage of the Tethyan scale is proposed between the Asselian and Yakhtashian. The lower boundary of the Hermagorian Stage is proposed to be located at the base of bed 81 in the 1015 section of Darvaz (Tadzhikistan). The boundary between the Hermagorian and Yakhtashian stages is placed at the base of bed 73 in the Zweikofel section at Zweikofel, Carnic Alps. In the Darvaz region, Tadzhikistan, the type area for the Yakhtashian Stage, this boundary has never been precisely defined. The entire fusulinid assemblage of the upper part of the Grenzland and Zweikofel formations reported herein includes 62 species of 18 genera, of which one subgenus and 12 species and subspecies are new. Copyright © 2012 John Wiley & Sons, Ltd.