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Evidence for basement reactivation during the opening of the Labrador Sea from the Makkovik Province, Labrador, Canada : insights from field data and numerical models.

Peace, Alexander and Dempsey, Edward and Schiffer, Christian and Welford, J. and McCaffrey, Ken and Imber, Jonathan and Phethean, Jordan (2018) 'Evidence for basement reactivation during the opening of the Labrador Sea from the Makkovik Province, Labrador, Canada : insights from field data and numerical models.', Geosciences., 8 (8). p. 308.

Abstract

The onshore exposures adjacent to modern, offshore passive continental margins may preserve evidence of deformation from the pre-, syn-, and post-rift phases of continental breakup that allow us to investigate the processes associated with and controlling rifting and breakup. Here, we characterize onshore brittle deformation and pre-rift basement metamorphic mineral fabric from onshore Labrador in Eastern Canada in the Palaeoproterozoic Aillik Domain of the Makkovik Province. Stress inversion (1) was applied to these data and then compared to (2) numerical models of hybrid slip and dilation tendency, (3) independent calculations of the regional geopotential stress field, and (4) analyses of palaeo-stress in proximal regions from previous work. The stress inversion shows well-constrained extensional deformation perpendicular to the passive margin, likely related to pre-breakup rifting in the proto-Labrador Sea. Hybrid slip and dilatation analysis indicates that inherited basement structures were likely oriented in a favorable orientation to be reactivated during rifting. Reconstructed geopotential stresses illuminate changes of the ambient stress field over time and confirm the present paleo-stress estimates. The new results and numerical models provide a consistent picture of the late Mesozoic-Cenozoic lithospheric stress field evolution in the Labrador Sea region. The proto-Labrador Sea region was characterized by a persistent E–W (coast-perpendicular) extensional stress regime, which we interpret as the pre-breakup continental rifting that finally led to continental breakup. Later, the ridge push of the Labrador Sea spreading ridge maintained this general direction of extension. We see indications for anti-clockwise rotation of the direction of extension along some of the passive margins. However, extreme persistent N–S-oriented extension as indicated by studies further north in West Greenland cannot be confirmed.

Item Type:Article
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Status:Peer-reviewed
Publisher Web site:https://doi.org/10.3390/geosciences8080308
Publisher statement:This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).
Date accepted:15 August 2018
Date deposited:22 August 2018
Date of first online publication:20 August 2018
Date first made open access:22 August 2018

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