Mineral Industries and Geology of Certain Areas - Vermont Agency ...

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P 78 REPORT OF THE VERMONT STATE GEOLOGIST. quartzites of Hanover and Lebanon; a rock lithologically identical with the Lower Cambrian quartzites of western Vermont. After renewed investigation I was successful in finding unquestioned differences and to photograph the same. These phenomena can be seen in illustration, Plate XV, Northfield slate quarry. The large distinct lines dipping 8o° east are the superinduceci planes of cleavage. The less distinct lines at the low angle of 300 to 350 west are planes of original bedding. It is along these planes that many graptolites may yet be discov - ered. Hitherto the search has been futile; in part, because made along lines of cleavage, while the true bedding was unknown; and in part, because the strata have become tilted and broken enough to obliterate many traces of Lower Trenton organisms. This discovery of the true dip is deemed of vast importance in leading to the conclusion that this band of Trenton slate lies unconformably upon the Huronian terranes flanking it upon the west. In a quarry one-fourth mile farther south similar deviations were discovered. The planes of bedding at a low angle to the west are clearer than the lines of fissility. This variation does not hold true in all the quarries, for, occasionally distorted pebbles lie in the lines of cleavage. In such cases the planes of fissility and bedding are parallel. At Barnard, where the western member terminates, is the best locality to searEh for fossils. The eastern member extends interruptedly through the State. In East Barnet it becomes very narrow, crosses the Passumpsic River, and with a strike of north 100 east traverses Waterford Mountain. The slate widens rapidly to the north. South from Barnet the band becomes lost until in the northern part of Newbury it reappears as a narrow band. It is possible that for this short interval the slate underlies the \Vashington limestone; but more probably, as the beds are from 100 to i,000 feet in thickness, it has been eroded. About two miles north of Round Pond in Newbury this band suddenly increases its width threefold ana extends south to PJ .\ir. X V Sabni Slare Quarry. Northfiejd. Strike N. iF E. Dip of Cleavage 75-80' W.
REPORT OF THE VERMONT STATE GEOLOGIST. C) C) 0 C) U within one mile of Bradford Village. Here the slate terminates abruptly and the Huronian rocks take its place. It does not clip under the Washington limestone, for that rock lies io miles to the west; nor under the Bradford schist, for the strike of the Bradford schist is parallel with the slate, viz, north and south. The Huronian rocks are laid bare to the west until they touch directly the Bradford schist. It may be that here is the beginning of the great fault that lies farther up Waits River valley. Excluding the fault theory, the slate must suddenly increase in thickness, and disintegration and erosion must have obliterated the last relic of the slate. Five miles to the south in Fairlee the deposit is 1,000 feet in thickness. Instead of a uniform cleavage dip to the east, I find a svnclinal trough. It first makes its appearance a short distance north of Lake Morey. The lake is three miles long arid one-half mile wide. Nearly all of it lies in the synclinal trough. Its greatest depth is 500 feet. It was here that Captain Morey's crude boat, the immediate forerunner of Robert Fulton's success on the Hudson, was sunk. Near the north end of the lake on the east side the dip is 600 west. Directly opposite, on the west side, the dip is 85 ° east. At the southwest corner of the lake the dip is 6o° west, at the southeast there is a little bunch of distorted argillite with strike east and west, clip 8 ° north. Plate XVI shows the lake with the hills of slate rising hundreds of feet above it to the west. About one-half mile north of the head of the lake is the Fairlee gold mine, situated on the farm of Mrs. S. A. Davis. The vein of quartz carrying the ore is 7 feet wide; its length and depth is unknown. The analysis yields gold to the valtie of $9 per ton and silver $30. The vein is also well mineralized with galena and chalcopyrite. A little south of the center of the lake, far up among the hills on the west side, is situated the beautiful cascade known as Glen Falls. The perpendicular descent of this babbling brook is now 25 feet. The stream has worn a channel through the
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