LE3 .A278 2010

2010

Robertson, Michael
Stanley, Cliff

Acadia University

Bachelor of Science

Honours

Physics

Physics

This study investigates the total magnetic field strength over the Bloody Creek bolide impact structure (BCS), located approximately 10 km south of Bridgetown, Nova Scotia. This 400 m diameter, slightly elliptical impact structure has been flooded by Nova Scotia Power's Bloody Creek hydroelectric reservoir, and thus is not directly available for study. Consequently, a ground magnetic survey was conducted over this site in the winter, when the reservoir was frozen. Measurements were standardized using a base station magnetometer, and a data quality assessment revealed that the data are highly reproducible. Results were evaluated using classical geostatistics, and a semivariogram was examined to understand the spatial variance structure of the data. Isotropic spherical and exponential functions with small nugget effects were chosen as appropriate models for subsequent kriging. Before kriging, the data were declustered at a scale approximating the sampling interval to ensure numerical stability in the kriging calculations. Ordinary kriging was undertaken, and two un-biased, minimum error variance surfaces describing the total magnetic field strength anomalies in the area were obtained. These surfaces were subjected to a number of empirical image analysis procedures to enhance any magnetic patterns that occur in the Bloody Creek area, including first and second derivative, and edge-detection maps. Interpretations of these surfaces reveal very subtle patterns that equivocally suggest the presence of an elliptical crater structure. The obscurity of the patterns suggests that the impact crater likely does not contain significant amounts of magnetic material (e.g., iron or chondrite meteor debris), and that impact did not substantially modify the low relief of the magnetic field in the granitic host rocks.

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https://scholar.acadiau.ca/islandora/object/theses:750