Formation of band ogives and associated structures at Bas Glacier d’Arolla, Valais, Switzerland
Formation of band ogives and associated structures at Bas Glacier d’Arolla, Valais, Switzerland
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瑞士瓦莱州巴斯冰川达罗拉的带状尖顶和相关结构的形成
DOI：
10.3189/172756502781831494
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发表时间：
2002
影响因子：
3.4
通讯作者：
N. Glasser
中科院分区：
文献类型：
--
作者：
B. Goodsell;M. Hambrey;N. Glasser
摘要利用构造冰川学、沉积学和地球物理技术，对瑞士阿罗拉冰川带及其伴生构造的形成提供了新的认识。沉积层理、裂隙痕迹和横向面理在下冰川和冰川舌中被识别为平面结构。层化和裂缝痕迹逐渐变形为冰川舌中的横向叶理，并增强了这种横向叶理。利用探地雷达确定了三维几何图形，它描绘了四个主要特征：(1)被解释为冰/床界面的深层反射体；(2)被解释为椭圆形的反射丰富区和反射贫乏区；(3)向上倾斜冰川的反射体，被解释为平面结构；以及(4)来源不明的下降冰川倾斜反射体。在冰川表面，每个卵带都由一条亮带和一条暗带组成。暗带包含更强烈的叶理作用，在不同的风化作用下，会捕获细小的碎屑。深色卵形带内的碎屑和透明的基性冰表明，基冰已经上升到冰川表面。最适用于阿罗拉冰川带形成的模型是对Posamentier(1978)的“反向断裂”假说的改进。在这种情况下，形成了多个剪切带，通过这些剪切带，基冰被抬升到冰川表面，产生黑色的叶状卵形带。这个模型与从其他冰川报道的观测结果相吻合。
Abstract Structural glaciological, sedimentological and geophysical techniques are used to provide new insight concerning the formation of band ogives and associated structures at Bas Glacier d’Arolla, Switzerland. Sedimentary stratification, crevasse traces and transverse foliation are identified as planar structures in the lower icefall and glacier tongue. Stratification and crevasse traces are progressively deformed into, and enhance, the transverse foliation found in the glacier tongue. Three-dimensional geometry has been defined using ground-penetrating radar, which portrays four main characteristics: (i) deep reflectors interpreted as the ice/bed interface, (ii) alternating reflection-rich and reflection-poor zones interpreted as ogives, (iii) up-glacier-dipping reflectors, interpreted as planar structures, and (iv) down-glacier-dipping reflectors of uncertain origin. At the glacier surface, each band ogive consists of a light and dark band. The dark bands contain more intense foliation which, on differential weathering, traps fine debris. Clasts and clear ice of basal character within dark ogive bands suggest that basal ice has been raised to the glacier surface. The most applicable model for the formation of band ogives at Bas Glacier d’Arolla is a refinement of Posamentier’s (1978) “reverse faulting” hypothesis. In this context, multiple shear zones are formed, through which basal ice is uplifted to the glacier surface to produce the dark, foliated ogive bands. This model fits observations reported from other glaciers with band ogives.