sgr ms thesis - University of Maine

eaction processes were involved in the formation of the Shatter Zone, so a D r
value greater than 1.25 would not be expected (Jebrak, 1997; Lorrileaux et al.,
2002).
5.3.5. Clast Circularity Analysis
Although it is not a fractal property, circularity is directly influenced by the
degree of abrasion, dilation, and transport that occurs in the development of a
breccia, and it could prove important in comparing modified and unmodified
clasts (e.g. Dellino and Volpe, 1996, Clark, 1990). The greater the wear on the
clast, the more circular it will become owing to loss of high surface-area corners.
Circularity is a measure of the compactness of a shape, unlike boundary analysis
which is meant to quantify the complexity of surface patterns. Because a circle is
the most compact two-dimensional geometry, a shape’s compactness is
compared to the circle as the ratio
(5.7)
To calculate circularity of a clast, its area and perimeter must be determined.
Consider the area of a circle:
(5.8)
To define the area of a circle as a function of a given perimeter (the perimeter of
the noncircular clast), r must be replaced with p:
(5.9)
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