Fracture-correlated lineaments at Great Bay, southeastern New Hampshire
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Resource Abstract:
Analysis by remote-sensing techniques and observations of exposed bedrock structure were preliminary steps taken in a study
to locate potential bedrock-fracture zones that may store and transmit ground water near Great Bay, N.H. To help correlate
lineaments on the surface with fractures, structural measurements were made at exposed bedrock, largely along the shoreline
of the bay, and analyzed to identify fracture trends and fracture characteristics. With these fracture data, lineament-filtering
techniques, such as (1) buffer analysis around individual lineaments, (2) discrete-measurement analysis by domain, and (3)
spacing-normalized analysis by domain, identified 'fracture-correlated lineaments.' Of the 927 lineaments identified in the
study area (180 square kilometers), 406 (44 percent) were evaluated because they either were located within 305 meters of
an outcrop with fracture data or intersected one of five 3,300-meter-square grid domain cells that encompassed the fracture
data. Of the 406 lineaments, 190 (47 percent) are fracture correlated, although only 15 percent were correlated by more than
one filtering technique. The large number of lineaments found in areas of thin glacial overburden and high densities of fractured
outcrops suggests that filtering techniques are useful in these areas to selectively identify fracture-correlated lineaments.
Fractures parallel to bedding in the Kittery Formation are open locally and often associated with vugs, with up to 1-centimeter
aperture, and may provide appreciable secondary porosity in this rock unit. Discrete-measurement analysis by domain identified
fracture-correlated lineaments with orientations parallel to these open and vug-filled fractures. Fracture-correlated lineaments
related to closely spaced fractures were identified by the spacing-normalized analysis by domain. Analysis results may be
used to indicate the potential bedrock pathways for ground-water-discharge points along the shoreline of Great Bay.
Citation
Title Fracture-correlated lineaments at Great Bay, southeastern New Hampshire