Full-fit reconstruction of opening of Labrador Sea and Baffin Bay: A special focus on continental deformation
Reconstructing the pre-rift configuration of Greenland and North America, and the early tectonic evaluation within the Labrador Sea and Baffin Bay, raises several issues. Some models treat linear magnetic anomalies adjacent to the continental margins of the Labrador Sea as 28-33 seafloor-spreading isochrones. However, more recent seismic data suggest that so-called "transitional crust" extends much further seaward. In addition, various authors have proposed that treating Greenland and North America as rigid plates leads to unreasonable gaps and overlaps in full-fit reconstructions. Extension within Hudson Bay, or large strike-slip motions within Greenland, has been suggested as possible explanations. To address these issues, we investigate the full-fit configuration of Greenland and North America using an approach that considers continental deformation in a quantitative manner, in contrast to traditional models that treat continents as rigid blocks. This new method has been applied in this region to derive new poles of rotation for full-fit plate reconstruction. This method takes in to account the landward limit of thinning and extension in continental crust of the rift margins. We first generate a crustal thickness map using a gravity inversion method, calibrated against all available crustal thickness information from seismic refraction profiles and receiver functions from onshore seismic stations. We also define the extent of the limit of stretched continental crust along each margin. The continental-oceanic boundary (COB) is located using interpreted seismic profiles and revising COBs previously proposed for both margins. Restoration of COBs was accomplished by generating small circle motion paths between UCCL and COB lines. Crustal thickness was extracted along each profile to calculate its length before subjected to stretching. Major corrections in the extent of stretched continental crust, and it's pre-rift thickness were taken into account to achieve the best fitting restored COBs. We also tested models in which the crustal thickness grid was revised to account for the amount of igneous material, ascribed to the influence of the Iceland Plume, added to the lower crust in the Davis Strait. We tested end-member restorations considering the transitional crust as oceanic or continental according to our interpretation of previously studied seismic lines in this region. Fitting the margins and computing total-fit Euler poles was carried out by two different methods: a Visual fitting technique with GPlates software and the quantitative least-squares Hellinger methodology. Conjugate Precambrian bedrock units and structural features onshore of both margins were then correlated and the scenario that showed the maximum compatibility with these observations was most highly ranked. The proposition of the Ungava fault zone in the Davis Strait as a leaky transform fault partly resolves problems in this region in alternative reconstruction scenarios, reducing overlap in the Davis Strait and gaps in the Labrador Sea. These more robust plate reconstructions form the basis for generating topological deforming meshes that represent the kinematic evolution of Greenland-North America rifting.
AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- 8109 TECTONOPHYSICS / Continental tectonics: extensional;
- 8157 TECTONOPHYSICS / Plate motions: past