The Paleozoic tectonic evolution of the northern edge of North America: A structural study of Northern Ellesmere Island, Canadian Arctic Archipelago

Abstract

On Ellesmere Island, the Clements Markham fold belt of the Franklinian mobile belt is flanked to the northwest by a Caledonian terrane, Pearya. On the basis of the Proterozoic to mid‐Ordovician stratigraphic and structural similarities with Spitsbergen and on the mid to late Silurian relationship between Pearya and Ellesmere Island, some strike‐slip displacement must have been involved in the accretion of Pearya to its present position. However, the structural style of the Clements Markham fold belt on Ellesmere Island is characterized by chevron folds with axial planar cleavage (flexural folding) and shallow plunging fold axes. The present terrane boundary faults show steeply plunging lineations indicating a vertical component of motion strongly predominating the strike‐slip component. Thus the first detailed structural study of the area has produced no positive structural evidence for late Silurian transcurrent shear or transpression. Therefore decoupling of a strike‐slip component of plate motion from a distributed compressive component is suggested for northern Ellesmere Island. Accretion of Pearya most likely occurred along one of the major fault zones to the southeast of the thrust faults marking the present terrane boundary. However, indications of strike‐slip displacement have not yet been observed along these faults possibly due to later thrust faulting. The Silurian Imina and Lands Lokk formations form an accretionary wedge of orogen‐derived turbidites which were deposited on oceanic or highly attenuated continental crust. Thus the time interval spanning the deposition and deformation of the turbidite formations dates the period of accretion and of predominantely orthogonal continental convergence. In the light of current ideas concerning the episodic and diachronous development of orogenic belts, the Silurian deformation in northwestern Ellesmere Island may be interpreted as the beginning of the orogenic cycle that culminated in the Late Devonian ‐ early Carboniferous Ellesmerian event.