LE3 .A278 2012

2012

Spooner, Ian
Williams, Peter

Acadia University

Bachelor of Science

Honours

Geology

Earth & Environmental Sciences

Virtually all terrestrial impact craters exhibit a circular geometry in plan-form; only three impact sites exhibiting non-circular, elongate forms have been identified on Earth. One of these exceptional sites is the Bloody Creek Crater located in southwestern Nova Scotia, an approximately 0.42 km long-axis crater first identified in 1987 during a regional air photo survey and confirmed as an impact crater in 2009. The structure’s rare deviation from circular symmetry, pristine definition, preservation through shock metamorphic features of anomalously high pressures at the rim, low depth-to-diameter ratio, and age remain ambiguous and complicate the interpretation of the origin and evolution of the crater. The purpose of this study was to quantify the form of the feature in order to better understand the nature and age of impact. To achieve this objective, analytical software was used to assess the shape of the crater rim. An extensive review of the literature was also performed to understand the controls on crater formation as well as to synthesize a model for the geomorphic evolution of the site that would aid in the interpretation of the age of the structure. Results demonstrate that the form of the crater rim is best approximated by an ellipse. This conclusion has resulted in the exclusion of a number of proposed impact models. Though elliptical craters may be formed by the erosion of circular impact features, the tectonic and/or geomorphic scenarios required to produce this outcome are inconsistent with models of evolution of the site. It is concluded that the Bloody Creek Crater was formed by very low angle impact into a nearly level target with minimum cover. Impact occurred after peneplanation of the South Mountain Batholith and after renewed uplift and erosion in the Tertiary, likely constraining the maximum age of impact to Pliocene. The pristine nature and nearly complete preservation of the rim structure may indicate a much younger pre- or syn-glacial age.

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https://scholar.acadiau.ca/islandora/object/theses:888