Formation of band ogives and associated structures at Bas Glacier d'Arolla, Valais, Switzerland

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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 dArolla, 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 dArolla 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.
Original languageEnglish
Pages (from-to)287-300
Number of pages14
JournalJournal of Glaciology
Volume48
Issue number161
DOIs
Publication statusPublished - Mar 2002

Keywords

  • Europe
  • Switzerland
  • Geometrical structure
  • Three dimensional structure
  • Radar observation
  • Glacier crevasse
  • Models
  • Debris
  • Interface
  • Basal ice
  • Glacial tongue
  • Stratification
  • Glacier

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