Canada Basin and Lomonosov Ridge: Inferences Based on Precambrian and Lower Paleozoic Geology of Canadian Arctic Islands: ABSTRACT

Abstract

Canada basin truncates and post-dates a belt of north-trending structures in the central part of the Arctic Islands. The trends, though exhibited by Phanerozoic strata, are interpreted as rejuvenated Precambrian basement features because they cut across Phanerozoic basin axes and parallel exposed Precambrian structures on the south. The maximum possible age of the Canada basin, therefore, is the age of these trends--about 1.7 b.y. A geanticline, characterized by volcanism and plutonism, rose out of a late Proterozoic and occupied the northern rim of the Arctic Islands and adjacent present offshore region, from Cambrian to Devonian time. What lay beyond the geanticline is unknown, and speculations about that region depend on the tectonic model used. If present concepts of plate tectonics are applied, it appears that Canada basin (or some predecessor) opened in middle to late Proterozoic time with a developing on the newly formed continental margin. The floor of the basin was thrust beneath the from latest Proterozoic or Cambrian to Devonian time, and produced a geanticline above and southeast of the postulated Benioff zone. Ridge: A belt of north-trending structures in northernmost Ellesmere Island lines up with the southern extremity of Ridge. The structures, formed in sialic metasedimentary and metavolcanic rocks, are partly pre-late Middle Ordovician. The belt aligned with Ridge was elevated relative to terrane on the east during 2 Paleozoic orogenies, but not during the Tertiary orogeny. A short distance inland, the north-trending belt terminates against west-trending structures subparallel with the axis of the Franklinian geosyncline. The zone of intersection, marked by ultrabasic intrusions, was a site of repeated crustal extension on a scale of miles. If the Ridge has oceanic crust the apparent alignment would be coincidental. If it has continental crust, two interpretations are possible: (1) the north-trending belt represents an early Paleozoic Lomonosov geosyncline that joined the Franklinian; (2) both Ridge and the north-trending belt in Ellesmere Island are controlled by meridional Precambrian basement trends, but these trends were rejuvenated in a different manner, and perhaps at different times, on Ellesmere Island and in the present Arctic Ocean. This hypothesis is favored. End_of_Article - Last_Page 2509------------