Apparent Brecciation Gradient, Mount Desert Island, Maine

1
Apparent Brecciation Gradient, Mount Desert
Island, Maine
Amber T Hawkins Scott E Johnson
Department of Earth Sciences, University of
Maine, Orono, ME 04469 amber.hawkins_at_umit.ma
ine.edu
Presentation Number V21A-03
Summary A cross-section through the magmatic
breccia surrounding the Cadillac Mountain Pluton
on Mount Desert Island, Maine, was examined using
digital mosaic mapping and fractal analysis at
representative outcrops. The data indicate a
spatial and possibly temporal brecciation
gradient from the incipient stages preserved
approximately 3 km from the magma chamber to the
final stages adjacent to the chamber. Our data
and observations suggest that a catastrophic
volcanic event was the driving force for breccia
formation.
1 m
1 m
Clast Supported
1 m
Matrix Supported
1 m
Fractal Analysis The fractal dimension (Fd) of
each clast was calculated using NIH Image and a
Euclidean distance mapping method described by
Bérubé and Jébrak (1999) to quantify the
morphology of the fragments, or the complexity of
the outline. The more complex the fragment
outline, the higher the fractal dimension,
indicating that the fragment is less "mature" or
has had less exposure to erosional processes,
such as the injection of an igneous matrix
(Jébrak 1997). A manual, Analyse D'Image pour
les Nuls (Ross, 2001), and a macro written by
Bérubé (attained through pers. comm. M. Jébrak)
guided the analysis. The diagram at left
demonstrates the preparation of the data. Only
clasts that were fully imaged by the digital map
and that were sufficiently visible were used in
the calculations. Results are shown to the right.
Sols Cliffs breccia has an average Fd of 1.125,
Seeley breccia 1.052, Dubois 1.047, and Great
Head breccia has an average Fd of 1.040. NIH
Image was also employed to calculate the percent
matrix of the digital maps. Results are shown on
the far right.
Author on Bar Harbor Formation
Data preparation for fractal analysis
Appropriate clasts were sorted by size and saved
in separate files
References