Abstract--An approximately 0.4 km diameter elliptical structure formed in Devonian granite in southwestern Nova Scotia, herein named the Bloody Creek structure (BCS), is identified as a possible impact crater. Evidence for an impact origin is based on integrated geomorphic, geophysical, and petrographic data. A near-continuous geomorphic rim and a 10 m deep crater that is infilled with lacustrine sediments and peat define the BCS. Ground penetrating radar shows that the crater has a depressed inner floor that is sharply ringed by a 1 m high buried scarp. Heterogeneous material under the floor, interpreted as deposits from collapse of the transient cavity walls, is overlain by stratified and faulted lacustrine and wetland sediments. Alteration features found only in rim rocks include common grain comminution, polymict lithic microbreccias, kink-banded feldspar and biotite, single and multiple sets of closely spaced planar microstructures (PMs) in quartz and feldspar, and quartz mosaicism, rare reduced mineral birefringence, and chlorite showing plastic deformation and flow microtextures. Based on their form and crystallographic orientations, the quartz PMs consist of planar deformation features that document shock-metamorphic pressures ≤25 GPa.The age of the BCS is not determined. The low depth to diameter ratio of the crater, coupled with anomalously high shock-metamorphic pressures recorded at its exposed rim, may be a result of significant post-impact erosion. Alternatively, impact onto glacier ice during the waning stages of Wisconsinian deglaciation (about 12 ka BP) may have resulted in dissipation of much impact energy into the ice, resulting in the present morphology of the BCS.

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The North structure is a discontinuous, partially flooded elliptical basin 250 m in diameter and defined by arcuate scarps. It is located in Annapolis County, Nova Scotia, approximately 1 km north of the Bloody Creek structure, a possible 400 m-diameter elliptical impact crater. Geophysical surveys indicate that raised scarps border a broadly elliptical basin with depth/diameter ratios similar to those at the Bloody Creek structure. Percussion coring and probing indicated that the basin is in-filled with 3.5 m of lacustrine sediment and peat overlying post-glacial alluvial sediment and diamicton. Samples collected proximal to the rim of the structure contain kink-bands in feldspar and biotite and possible planar microstructures in quartz and feldspar. The elliptical nature and similar, anomalous morphometries of the North and Bloody Creek structures indicate that two, low-angled, genetically linked impacts may have taken place at the site. Both structures are interpreted to be post-Pliocene (<2.6 Ma), based on the unlikelihood of their preservation during Cretaceous-Paleogene regional peneplanation. RÉSUMÉLa structure d'impact du North Group est une cuvette elliptique discontinue et partiellement inondée d'un diamètre de 250 mètres, définie par des escarpements arqués. Elle se situe dans le comté d' Annapolis, en Nouvelle-Écosse, à environ 1 km au nord de la structure de Bloody Creek, un possible cratère d'impact de forme elliptique mesurant 400 mètres de diamètre. D'après les levés géophysiques, les escarpements soulevés bordent une cuvette largement elliptique dont les rapports entre la profondeur et le diamètre sont semblables à ceux de la structure de Bloody Creek. Les activités de carottage à percussion et de sondage d' exploration ont permis de savoir que l'intérieur de la cuvette était rempli d'une couche de 3,5 mètres de sédiments lacustres et de tourbe, qui recouvrent du diamicton et des sédiments alluvionnaires d' origine post-glaciaire. Le contenu des échantillons prélevés dans le milieu proximal de la bordure de la structure révèle des bandes froissées dans le feldspath et la biotite et de possibles microstructures planaires dans le quartz et le feldspath. Si l' on se fie à la nature elliptique et à la morphométrie anormale similaire des structures du North Group et de Bloody Creek, il se pourrait que deux impacts d'un angle peu prononcé et génétiquement liés aient eu lieu à cet endroit. Les deux structures seraient, d'après les interprétations, postérieures au Pliocène (<2,6 Ma), car les probabilités qu' elles aient été préservées pendant la pénéplanation régionale du Crétacé-Paléogène sont plutôt faibles.[Traduit par la redaction] ATLANTIC GEOLOGY 51, 044-050 (2015) 0843-5561|15|00044-050 $1.80|0