Seismic structure of the Proterozoic on Melville Island, Canadian Arctic Archipelago

Abstract

About 800 km of 8 and 10 s reflection seismic data from Melville Island have been newly processed, migrated and interpreted with emphasis on mid- and deep crustal horizons. A few additional tie lines, totalling 70 km, extend to only 6 s. The seismic sections are of excellent quality with many reflecting horizons to depths of 28 km. A seismic stratigraphic investigation of the sections suggests a thick sedimentary succession in this part of the crust. Some strong reflections beneath these units at depths of 25–28 km may reveal the position of the Archaean(?) crystalline basement. The uppermost 10 km part of the crust consists of Ordovician to Devonian sequences on the Arctic Platform (western Dundas Peninsula) and in the Parry Islands Foldbelt. In the Sverdrup Basin (Sabine Peninsula) these strata are covered with sediments of the Upper Palaeozoic and Mesozoic successions. The Cambrian and Proterozoic formations are tectonically distinct from the remaining Palaeozoic and Mesozoic sequences. Their stratified structure on the seismic lines indicates thick, 15–20 km sedimentary sequence under the major Ordovician detachment zone. Beneath a well stratified, 4–5 km thick Cambrian succession there is a major unconformity. This is, most likely, the top of the Proterozoic section. The surface of this unconformity has a gentle dip towards the north and northeast in the study area. Its depth ranges from 10 to 14 km. The lower and middle part of this Proterozoic sequence underwent orogenesis and the whole sequence preserves several major unconformities. Features due to successive compressional and extensional tectonism are remarkable. The interpretation of the deeper reflections provides a tectonic and stratigraphic history of the Proterozoic on eastern Melville Island. The appropriate model indicates alternating periods of calm sedimentation and intensive or long-lasting erosion interrupted by a major compressional and probably by a milder extensional period. Several significant unconformities are recorded by the seismic sections beneath and on the presumed top of the Proterozoic section.