Abstract
Fracture traces visible on aerial photographs are natural linear-drainage, soiltonal, and topographic alignments which are probably the surface manifestation of underlying zones of fracture concentration. The relationship between fracture traces and occurrence of ground water was studied in Nittany Valley of Central Pennsylvania, U.S.A., an area underlain by folded and faulted Lower Paleozoic carbonate rocks with interbedded sandstones. Several bore-hole caliper surveys were run to determine if fracture zones underlying fracture traces localized cavernous openings. Three caliper logs, obtained from wells drilled on fracture traces, showed that numerous cavernous openings were penetrated by wells extending to 350 feet in depth, while four logs obtained from wells drilled in interfracture trace areas showed few cavernous openings. Specific capacities, unadjusted for variations in well diameter, pumping period, and well losses, were determined for eleven wells drilled in dolomite and sandy dolomite and for three wells drilled in limestone. The specific capacities were divided by the total depth of saturated rock penetrated by each well to obtain the specific capacity in gallons per minute per foot of drawdown per foot of saturated rock penetrated. These values ranged from .0008 and .002 for two wells drilled in dolomite in interfracture trace zones to .02, .04, .04, .07, .08 and .09 for six wells drilled on or near a single fracture trace in dolomite, 1.52 and 1.23 for two wells drilled on a single fracture trace in limestone, .11, .12 and .17 for three wells drilled in dolomite at or near the intersection of two fracture traces and 3.27 for a single well drilled at the intersection of two fractures in limestone. These data support the concept that fracture traces reflect underlying fracture concentrations and are useful as a prospecting guide in locating zones of increased weathering, solutioning and permeability.
Published Version
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