Géologie de la région située entre Tigssaluk fjord et Sermiligârssuk fjord (partie médiane), SW-Groenland

Abstract

The investigations, the results of which are described in the present work, were conducted during two distinct stages, from 1957 to 1960: 1) the field work, including the drawing of the geological map at a scale of 1:20000 and the collecting of numerous samples; this was made possible by the organization and facilities put at our disposal by the Geological Survey of Greenland, 2) the examination of the collected material, which was conducted in the laboratories of geology and petrography of the University of Lausanne. The area which we have studied is composed of an ensemble of gneiss, schists, dykes and massifs of various age and composition; it is situated in the SW part of Greenland, about 30 km NNW of Ivigtut (Fig. 1 and Plate 1). The limits of this territory are the following: to the N, Sermiligârssuk fjord and the glacier of Sioralik; to the E, a depressed zone occupied by lakes; to the S, Tigssaluk fjord and a faultzone oriented approximately E-W; lastly, to the W, an ideal N-S line which marks the western limit of the maps at al: 20000 scale of the Geodætisk Institut that we used for the geological map. No geological investigations had been conducted in the area; the only published information concerns the region as a whole, and is to be found in the works of N.V. Ussing (1912), C.E. Wegmann (1938 and 1947), J. Bondam (1956) and A. Berthelsen (1960 and 1961). Let us also mention the unpublished reports of our companions, the geologists of the Geological Survey of Greenland. Apart from a few small zones which were examined in detail, the geological mapping of the region was conducted in an exploratory manner with a view to establishing rather a chronology as precise as possible than a detailed map at a 1:20000 scale. The chronology, the main lines of which we are now going to put forward, represents an attempt at a synthesis based on observations made in our territory as well as in the entire region of Ivigtut; here we have the opportunity of seeing the deep zones of a mountain chain in which are visible traces of all the phenomena which follow each other during the evolution of a "drame-type", such as H. and G. Termier (1956), for example, have described it.