Abstract

Evidence is reviewed in this paper for the existence, on the polar margin of Canada and Greenland, of 12 regionally correlative depositional sequences that range from the Danian to the Pleistocene in age. Sequences are dated using foraminifera, dinoflagellates, miospores, land mammals and other macrofauna, magnetostratigraphy, and various radiometric methods. However, the present resolution of biostratigraphic schemes generally falls short of that provided by low latitude localities of similar age. The last seven cycles of the Cenozoic, those younger than 47 Ma, have been profoundly influenced by global climate variation. No such climate effect is recognizable in the earlier five sequences (65 to 47 Ma) for which a tectonic explanation is invoked. Rift-related deformation has affected depositional patterns for the later Cretaceous and Danian of the Labrador Sea and Baffin Bay region. This rift system is also inferred to have developed across the eastern Arctic Islands and to have included coeval volcanics and dyke swarms of northernmost Ellesmere Island and North Greenland. The Eurekan Orogeny evolved through various phases from the early Late Paleocene (Selandian) to at least the end of the Eocene. These phases involved the simultaneous emplacement of one or several plumes from a migrating hotspot, first beneath West Greenland, later beneath East Greenland, and finally beneath the North Atlantic and ancestral Iceland. The eastward migration of the plume jet is matched in time by the apparently diachronous westward expansion of the Eurekan Orogen and progressive rotation of tectonic transport directions; from northeasterly- and northerly-directed in the mid-Late Paleocene to northwesterly-directed in the latest Paleocene and Early Eocene, to westerly- and southwesterly-directed in the Middle and Late Eocene. A fundamental driving force for orogeny is considered to have been gravitational potential and spreading forces created by sublithospheric underplating and plume-induced regional uplift acting on the ancestral Greenland microplate. The orogenic transport directions of the Middle and Late Eocene are roughly parallel to those which acted to extend the eastern Arctic Islands and Baffin Bay region in the Cretaceous and Danian. Thus northwesterly-striking extension faults and northerly-striking sinistral faults, all active during the rifting phase, were converted into thrust inversion structures and dextral strike-slip faults, respectively, during the later stages of the Eurekan Orogeny. This conclusion, together with a presumed Late Paleocene and Early Eocene age for oceanic crust in northern Labrador Sea, promises to help resolve some of the long-standing issues surrounding the Nares Strait debate. Plume-head push acting on the Labrador and Baffin margins of North America, beginning at about 61 Ma, may also partly account for the simultaneous development of the Beaufort Foldbelt and other Laramide thrust belts of the North American Cordillera.

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