GEOLOGY OF THE BROADALBIN QUADRANGLE 45 



The crest of the Grenville fault block, between Bald Bluff and 

 Batchellerville, rises to eighteen hundred feet or over within a mile 

 of the fault. On the downthrow side the Little Falls dolomite 

 lies at an altitude of seven hundred feet but the Precambric is 

 buried under the Potsdam and Theresa formations and a part of 

 the dolomite. The thickness of these formations here is not exactly 

 known but to say that the Precambric near the fault is buried three 

 hundred feet is approximately correct. This means that the Pre- 

 cambric on the downthrow side is now at an altitude of four hun- 

 dred feet or fourteen hundred feet lower than that on the upthrow 

 side. Thus if we allow for even a small amount of erosion along 

 the crest of the fault-block, the displacement is in the neighbor- 

 hood of fifteen hundred feet. 



A feature of interest in connection with this fault is the rapid 

 diminution of throw along the southern portion. On the western 

 side of Bald Bluff the throw reaches nearly its maximum, while, in 

 spite of the heavy drift, it is certain that the fault has completely 

 disappeared within two or three miles southward. 



EDINBURG FAULTS 



The faults here described are named from the fact that they 

 occur in the town of Edinburg and near the village of the same 

 name. The writer is indebted to Mr J. W. Latcher of Edinburg 

 for assistance in locating certain important outcrops in this vicinity. 

 That at least two dislocations occur approximately as shown on the 

 map is quite certain, but very accurate work is impossible because 

 of the deep drift and scarcity of exposures. 



Of these two faults the more prominent one follows along the 

 eastern base of Fraker mountain (Stony Creek sheet) and thence 

 strikes nearly southwest to cross Butler creek about one mile west 

 of Edinburg. Farther southward the region is heavily drift cov- 

 ered. North of Fraker mountain the fault has not been studied. 

 The upthrow side is on the west and the Grenville, in great ledges, 

 forms a pretty distinct fault-scarp. Heavy drift almost completely 

 conceals the downthrow side but the rock appears to be chiefly Little 

 Falls dolomite. A good dolomite outcrop occurs just below the 

 road crossing on a little creek near the map edge and two and one- 

 half miles north-northeast of Edinburg. This rock dips slightly 

 eastward and is within one-third of a mile of the fault at the base 

 of Fraker mountain. The thickness of the Paleozoics here is prob- 

 ably in the neighborhood of two hundred feet which means that the 



