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Geosciences 2018, 8(8), 308; https://doi.org/10.3390/geosciences8080308

Evidence for Basement Reactivation during the Opening of the Labrador Sea from the Makkovik Province, Labrador, Canada: Insights from Field Data and Numerical Models

1
Department of Earth Sciences, Memorial University of Newfoundland, St. John’s, NL A1B 3X5, Canada
2
School of Environmental Sciences, University of Hull, Hull HU6 7RX, UK
3
Department of Earth Sciences, Durham University, Durham DH1 3LE, UK
4
Department of Earth Sciences, Uppsala University, 752 36 Uppsala, Sweden
*
Author to whom correspondence should be addressed.
Received: 26 July 2018 / Revised: 13 August 2018 / Accepted: 15 August 2018 / Published: 20 August 2018
(This article belongs to the Special Issue Stress Quantification in Sedimentary Basins)
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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. View Full-Text
Keywords: rifting; passive margin; continental breakup; stress inversion; plate tectonics; geopotential stress; numerical modelling; field geology rifting; passive margin; continental breakup; stress inversion; plate tectonics; geopotential stress; numerical modelling; field geology
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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).
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Peace, A.L.; Dempsey, E.D.; Schiffer, C.; Welford, J.K.; McCaffrey, K.J.W.; Imber, J.; Phethean, J.J.J. 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 2018, 8, 308.

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