Abstract

Middle and Upper Devonian clastic strata of the Canadian Arctic Archipelago were deposited in a foreland basin which developed in front of the southward advancing Ellesmerian Orogeny. Three unconformity-bounded sequences are recognized in the preserved clastic wedge and are early Eifelian-earliest Frasnian, early Frasnian-late Frasnian, and late Frasnian-mid Famennian in age. The sequences are interpreted to reflect major tectonic episodes in the adjacent Ellesmerian Orogenic Belt. Each sequence was initiated by the widespread occurrence of accelerated subsidence related to crustal shortening and loading in the adjacent orogenic belt. The unconformities which cap the sequences are interpreted to have formed during times of tectonic quiescence when regional uplift took place due to forebulge expansion and crustal rebound related to the removal of tectonic loads by erosion. The orogenic front advanced southwestwards with each tectonic pulse and the fluvial-deltaic plain expanded in that direction with the progradation of deltaic deposits along the foreland basin.

Vitrinite reflectance values up to 1.1 in the youngest preserved strata (early-mid Famennian) indicate that a thick succession of late Famennian-Tournaisian strata formed the final deposits of the foreland basin, with a depocentre in the western Banks Island area. The concluding stage of the Ellermerian Orogeny occurred in latest Famennian-Tournaisian and resulted in deformation and uplift of the foreland basin.

Plate reconstruction reveals that the Ellesmerian Orogenic Belt had a sinuous shape through Arctic North America, extending from northern Greenland to a terminus in northern Yukon. This shape generally follows the original configuration of the lower Paleozoic continental margin. Oblique plate collision, implied by diachronous foreland sedimentation, along this margin resulted in the southwesterly migration of tectonism from Middle Devonian to earliest Carboniferous.