The Tectonic Framework of Northern Baffin Bay: A New Model for Plate Reconstructions of the Nares Strait Region

Gordon N. Oakey¹ and James A. Chalmers^2
1Atlantic, Geological Survey of Canada, Dartmouth, NS, Canada.
²Geophysics, GEUS, Copenhagen, Denmark.

A single pole of rotation for Eocene motion of the Greenland Plate relative to North America has been calculated using the fracture zone geometry in Baffin Bay and Labrador Sea. Paleocene motion (Chrons 27N-26N-25N) is also modeled with a single pole of rotation. A third pole of rotation is required to accommodate a rapid re-orientation of the Greenland Plate between Chron 25N and 24N corresponding with initiation of seafloor spreading between Greenland and Europe when Greenland moved as an independent plate. Due to the close proximity of this accommodation pole, the flow-line vectors calculated for the Greenland Plate are significantly different in the Labrador Sea and the Nares Strait region. In the south, the flow-line vector is similar to the Eocene direction of motion, while in the north the vector is similar to the Paleocene direction. The significance of this difference is that the apparent timing for the change in direction seafloor spreading in the Labrador Sea (Chron 25N) is not the same timing for the initiation of the convergent phase of the Eurekan Orogeny (Chron 24N) in the Nares Strait Region.

The new 3-pole kinematic model has been used to integrate known geological constraints of regional deformation associated with the Eurekan Orogeny to produce a new framework for plate reconstructions. In the Nares Strait region, the model predicts 200 km of NE sinistral motion of Greenland relative to Ellesmere Island during the Paleocene followed by 250 km of NNW-oriented plate convergence during the Eocene. Magnetic data in central Baffin Bay have been reinterpreted to define the extent of both Eocene and Paleocene oceanic crust, and a previously unknown fracture zone has been identified in northern Baffin Bay. Gravity models show that significant crustal thinning occurred beneath the Lancaster Basin and that little or no thinning occurred beneath the Jones Sound Basin. We propose that the Lancaster Sound is a failed rift-arm of the Eocene spreading system, and that Eocene motion along the newly defined (Bower) fracture zone extended along an (extensional?) strike-slip boundary through Jones Sound which links to the Grinnell Range-Douro Range fold and thrust belt on western Devon Island. Additionally, published interpretations of magnetic data over central Nares Strait indicate that Archean basement structures extend from Ellesmere Island to Greenland with no observed offset. As such, a simple linear “Wegener Fault” along Nares Strait cannot explain the required strike-slip motion of Greenland relative to Ellesmere Island during the Paleocene. We have incorporated estimates of crustal shortening across the central Ellesmere fold and thrust belt, distal crustal folding within the Sverdrup Basin, and inversion of Cretaceous(?)-Paleocene basins in northern Baffin Bay to demonstrate that the Eocene convergence phase of the Eurekan Orogeny can be accounted for in the plate reconstructions.

AAPG Search and Discovery Article #90130©2011 3P Arctic, The Polar Petroleum Potential Conference & Exhibition, Halifax, Nova Scotia, Canada, 30 August-2 September, 2011.