LINEAMENTS AND FRACTURE TRACES, DECATUR COUNTY, INDIANA By Theodore K. Greeraan U.S. GEOLOGICAL SURVEY
Lineanents and fracture traces have been mapped throughout Decatur County, Indiana. These lineaments and fracture traces may indicate that solutionenlarged vertical fractures in the limestone and dolonite aquifers underlie most of the county. The use of lineament and fracture-trace maps in selecting bedrock-drilling sites results in a significant increase in the number of usable sites. Bedrock wells drilled on or near mapped lineaments and fracture traces have a higher average yield than veils drilled into interfracture areas. Parts of Decatur County and several adjacent counties are economically restricted by inadequate water supplies. The Greensburg ffanicipal Water Works, supplying 35 percent of the county's population, obtains 25 percent of its water from six wells in Greensburg. The remaining 75 percent is pumped from the Flat Rock River. This water is piped 8.25 miles and lifted 183 feet to the treatment station. Although the Flatrock River has adeduate flow to supply Greensburg's water needs, a ground-water supply can probably be developed nearer the treatment plant. Pleistocene till covers most of the nearly horizontal bedrock. Although averaging about 50 feet thick, this unconsolidated unit does not seem to inhibit the mapping of lineaments and fracture traces. Bedrock is middle Paleozoic limestone, dolomite, and shale. Two sequences of limestone and dolomite, separated by a thin shale unit, constitute the principal aquifer. The extremely variable well yields from this aquifer indicate that the bedrock permeability is also variable. Well placement is important in a fractured bedrock terrane, as fractures are a principal source of water to the well. Here, the most productive bedrock wells are at the mapped intersection of two or more fracture traces or lineaments and at the lowest local altitude. Use of a fracture-trace map will not guarantee a sufficient supply of ground water but will reduce the chance of drilling an inadequate well.
Lineaments on Skylab photographs: Detection, mapping, and hydrologic significance in central Tennessee
The author has identified the following significant results. Lineaments were detected on Skylab photographs by stereo viewing, projection viewing, and composite viewing. Sixty-nine percent more lineaments were found by stereo viewing than by projection, but segments of projection lineaments are longer; total length of lineaments found by these two methods is nearly the same. Most Skylab lineaments consist of topographic depression: stream channel alinements, straight valley walls, elongated swales, and belts where sinkholes are abundant. Most of the remainder are vegetation alinements. Lineaments are most common in dissected areas having a thin soil cover. Results of test drilling show: (1) the median yield of test wells on Skylab lineaments is about six times the median yield of all existing wells; (2) three out of seven wells on Skylab lineaments yield more than 6.3 1/s (110 gal/min): (3) low yields are possible on lineaments as well as in other favorable locations; and (4) the largest well yields can be obtained at well locations of Skylab lineaments that also are favorably located with respect to topography and geologic structure, and are in the vicinity of wells with large yields.
EFFECT OF SAMPLE PREPARATION ON WATER TREE RESISTANCE OF XLPE/SEBS BLENDS
The effects of an aromatic polymer, such as poly[styrene-b-(ethylene-co-butylene)b-styrene] (SEBS), and its preparation processes on water tree resistance, morphology, crystallinity, dielectric constant and dielectric loss tangent of crosslinked polyethylene (XLPE)/SEBS and XLPE/SEBS/ethylene vinyl acetate (EVA) blends were investigated. The XLPE/SEBS samples were characterized by means of differential scanning calorimetry, scanning electron microscopy, dielectric spectral analysis and the accelerated water treeing experiment. The results clearly showed that although SEBS was partially compatible with LDPE and it was dispersed evenly in XLPE matrix, the blends demonstrated excellent dielectric performances, such as dielectric constant and dissipation factor. The crystallinity of XLPE/SEBS blends was decreased with increase in SEBS content and it was further decreased with the addition of EVA. SEBS could effectively improve the water-tree resistance of XLPE and both SEBS and EVA were found to improve the water tree resistance of XLPE synergistically as expected. The differences in sample preparation processes could change the phase morphology and dielectric performance of the blends, and could also influence the dispersion of SEBS in XLPE matrix as well as the crystallinity of the blends. Different preparation processes led to different water tree resistance behaviours of the samples. The improvement of SEBS dispersion in XLPE matrix helped to improve the water tree resistance of XLPE.