TOWARDS A NARES STRAIT SOLUTION - STRUCTURAL STUDIES ON SOUTHEASTERN ELLESMERE ISLAND AND NORTHWESTERN GREENLAND

Debate about structures in Nares Strait and plate tectonic models of the Paleogene Eurekan Orogen in the Greenland-eastern Arctic Archipelago region has been rekindled by publication of several hypotheses that are inconsistent with geological information and based on inconclusive geophysical data. The structural style of the orogen has been established by geological mapping of this region, while geophysical data from the Labrador Sea have provided constraints on timing of plate motions and resulting structures. However, in the Nares Strait area, geophysically detected features are of uncertain age and significance and are of limited value in assessment of tectonic models, whereas observed geological criteria provide close constraints. Mapped structures and stratigraphy from both sides of the strait limit sinistral strike-slip faulting in and immediately adjacent to Nares Strait to 25 ± 20 km, restrict reverse motion to about 20 km along one segment of the strait and preclude any significant normal displacement. Geophysical data, whose resolution is substantially less, neither support nor contradict these estimates. There is no geological evidence whatsoever for plate subduction in this region. The vicinity of the strait is aseismic at present. Neither subduction nor large transcurrent motion along Nares Strait is a necessary consequence of the opening of the Labrador Sea. A consistent model of plate motions and interactions can be achieved by a combination of: (1) 100 km of north-south extension from Hudson Strait to southern Ellesmere Island (such extension is supported by numerous structures on land and considerable seismic data offshore); and (2) between 100-200 km east-west intraplate shortening of the partly attenuated North American craton underlying western Greenland, and Ellesmere and Axel Heiberg islands. Such shortening probably occurred on several major thrust faults as well as on numerous intervening reverse faults and folds. Shortening of the whole crustal section may have occurred on deep-seated faults (originally normal faults developed during Sverdrup Basin rifting) which were reactivated as reverse faults. © 1990.