Studies on Crescentic Fractures and Crescentic Gouges with the Help of Close-range Photogrammetry

Studies on crescentic fractures and crescentic gouges were carried out in the central part of the Alpine piedmont glaciation and the Quaternary Alpine mountain ice sheet. The test sites were situated in the pro-glacial area of the Hornkees south Berliner Hiitte (Oberer Zemmgrund, Zillertal, Tyrol, Austria). This is also the area of the former confluence with another glacier which flowed at about 90 0 to Hornkees during the late-glacial period. It was therefore possible to make a comparison between different older glacier systems, different flow directions, and different ice thicknesses. About 12 000 minor features were measured by close-range photogrammetry; the result was 240 pairs of stereophotographs which were interpreted on first-order equipment. The single forms were registered point by point by coordinates. It was therefore possible to obtain threedimensionally registered forms. One important result was that the late-glacial and the post-glacial glaciers of the Zemmgrund produced minor features with a large variation in size. A further result was the definition of possible glacier-flow directions by interpretation of the different directions of crescentic fractures and crescentic gouges. By this means it was possible to obtain several working reconstructions of the lateand post-glacial stream lines of the merged glaciers. RESUME. Etude des fentes de press ion et des coups de gouge en croissant a [,aide de la photogrammetrie rapprochee. Des etudes sur les fentes de pression et coups de gouges en croissant ont ete menees dans la partie centrale de la glaciation alpine de piemont et de la calotte glaciaire quaternaire des Alpes. Les zones test sont situees dans. la zone proglaciaire du Hornkees, au sud de la Berh~er Hiitte (Oberer Zemmgrund, Zittertal, Tyrol, Autnche). C'est aussi la zone de l'ancienne confluence avec un autre glacier qui s'ecoulait perpendiculairement au Hornkees durant la derniere periode glaciaire. Ceci rend possible la comparaison entre differents systemes glaciaires differentes directions d'ecoulement, et differentes epaisseur~ de glace. Environ 12 000 formes de detail ont ete mesurees