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TitreNewly identified "Tunnunik" impact structure, Prince Albert Peninsula, northwestern Victoria Island, Arctic Canada
AuteurDewing, K; Pratt, B R; Hadlari, T; Brent, T; Bédard, J; Rainbird, R H
SourceMeteoritics and Planetary Science 2013 p. 1-13,
Séries alt.Secteur des sciences de la Terre, Contribution externe 20120214
Documentpublication en série
Mediaen ligne; numérique
ProvinceTerritoires du Nord-Ouest
SNRC88A/06; 88A/07; 88A/10; 88A/11
Lat/Long OENS-115.0000 -113.0000 72.7500 72.2500
Sujetscratères; cratères météoriques; analyses structurales; structures circulaires; caractéristiques structurales; roches sédimentaires; fractures coniques; géologie extraterrestre; géologie structurale; stratigraphie; Précambrien; Protérozoïque; Paléozoïque; Cambrien; Ordovicien; Silurien
Illustrationslocation maps; photographs; plots; photomicrographs
ProgrammeBassin sédimentaire Sverdrup, GEM : La géocartographie de l'énergie et des minéraux
Résumé(disponible en anglais seulement)
Regional geological mapping of the glaciated surface of northwestern Victoria Island in the western Canadian Arctic revealed an anomalous structure in otherwise flatlying Neoproterozoic and lower Paleozoic carbonate rocks, located south of Richard Collinson Inlet. The feature is roughly circular in plan view, approximately 25 km in diameter, and characterized by quaquaversal dips of approximately 45°, decreasing laterally. The core of the feature also exhibits local vertical dips, low-angle reverse faults, and drag folds. Although brecciation was not observed, shatter cones are pervasive in all lithologies in the central area, including 723 Ma old dikes that penetrate Neoproterozoic limestones. Their abundance decreases distally, and none was observed in surrounding, horizontally bedded strata. This circular structure is interpreted as a deeply eroded meteorite impact crater of the complex type, and the dipping strata as the remnants of the central uplift. The variation in orientation and shape of shatter cones point to variably oriented stresses with the passage of the shock wave, possibly related to the presence of pore water in the target strata as well as rock type and lithological heterogeneities, especially bed thickness. Timing of impact is poorly constrained. The youngest rocks affected are Late Ordovician (approximately 450 Ma) and the impact structure is mantled by undisturbed postglacial sediments. Regional, hydrothermal dolomitization of the Ordovician limestones, possibly in the Late Devonian (approximately 360 Ma), took place before the impact, and widespread WSW-ENE-trending normal faults of probable Early Cretaceous age (approximately 130 Ma) apparently cross-cut the impact structure.