Ellesmerian tectonism in the Canadian Arctic Islands: the end of the Franklinian Passive Margin

The Canadian Arctic Islands are situated on the northern margin of the North American continent. The region is reported to have undergone a complete Wilson cycle from the Neoproterozoic to the Devonian. In the Neoproterozoic, rifting occurred along the northern margin Laurentia, and the Franklinian passive margin formed. Sedimentation along this margin was continuous from the Cambrian to the early Devonian. Middle to late Devonian clastic strata, interpreted as a southwest prograding clastic wedge, are preserved across much of the Canadian Arctic Islands. The onset of clastic wedge sedimentation represents a switch from a passive margin depositional setting to a foreland basin depositional setting which formed following the Silurian accretion of Pearya, an exotic terrane, to the passive margin in northern Ellesmere Island. Sedimentation along the entire Franklinian margin ceased altogether when much of the Franklinian succession was deformed and uplifted during the late Devonian to early Carboniferous Ellesmerian Orogeny. However, the extent and timing of Ellesmerian tectonism in the wider circum-Arctic region are uncertain. Furthermore, evidence for many of the processes usually involved in orogenesis, such as metamorphism, a collisional core zone and post-tectonic magmatism are absent in the Canadian Arctic. So what was the geodynamic cause of the Late Devonian to early Carboniferous tectonism?

CASP fieldwork in 2009 and 2010 targeted two areas on Ellesmere Island: the Lake Hazen area in the northeast and the Raanes Peninsula area in the southwest. These two areas, approximately 500 km apart, contain very different sections through the Franklinian succession. At Lake Hazen, polydeformed Cambrian rocks are in fault contact with Permian to Cretaceous strata of the Sverdrup Basin. On the Raanes Peninsula, folded Ordovician to Devonian strata are unconformably overlain by, and in fault contact with, Carboniferous to Cretaceous strata of the Sverdrup Basin.

A comparison of the structural geology of the field areas visited by CASP provides constraints on the extent and timing of the Ellesmerian deformation documented on Ellesmere Island. Comparison with other areas in the circum-Arctic is the key to generating a model that explains the geodynamic cause of this enigmatic orogeny.