Analysis of brittle Paleogene structures in the Svea region, eastern Spitsbergen, Svalbard
During the Paleogene rifting of Svalbard and Greenland along a dextral transform, deformation occurred in two stages. Initial transpression, which formed a fold-and-thrust belt in western Spitsbergen and a foreland basin in central Spitsbergen, was followed by transtensional rifting. Small-scale brittle structures are observed in the subhorizontal Paleogene strata on the foreland basin’s eastern edge. This study analyzes the orientations and paleostress regimes of these structures in order to determine their tectonic origins. Orientation data from faults, joints, and slickenlines were collected within the Svea Nord mine and the surrounding area in order to resolve the paleostress regimes of these structures. An analysis of lineament orientations from aerial imagery was conducted to solidify these initial findings, based on the assumption that these linear erosional features are related to pre-existing bedrock fractures. Results show two populations of faults: NNW-SSE striking, west-dipping thrust faults and ENE-WSW striking normal faults. Joint orientation measurements reveal two dominant subvertical joint set orientations: ENE-WSW and NNW-SSE. The lineament data show a major NE-SW trend, and a minor NW-SE trend. Paleostress orientations of these structures suggest ENE-directed compression and NNW-SSE extension for the thrust faults and normal faults respectively. Both the joints and lineaments indicate a strike-slip setting. Given the age constraints on the faults and fractures, their orientations and paleostress determinations, they can be correlated with previously documented structures associated with fold-and-thrust belt deformation. That these small-scale extensional structures are likely related to the fold-and-thrust belt suggests that they formed in response to the larger dextral transpressive tectonic setting.