GEOLOGY OF MOUNT MARCY 55 



of the Keene valley and evidently indicating a powerful fault. The 

 crushed rock was still visible in 1914, although the exposure was not 

 so fresh and clear. The fault seems to bear into the hill somewhat 

 to the west of the valley as one goes north. 



To the south of this exposed and visible fault the East branch of 

 the Ausable is in a deep, rocky postglacial gorge as described and 

 illustrated by H. L. Ailing in subsequent pages. The river has a 

 zigzag course because it uses sometimes east and west faulted and 

 crushed zones, sometimes others north and south. The crushed 

 zones can be detected at times in the hard gneisses, and one east 

 and west one is occupied by a trap dike, 5 feet in width, which on 

 the place exposed runs true with the stream. The stream turns 

 to the north and follows the direction of a north and south crush 

 which can be seen in the highway on the east bank where a strong 

 fault breccia of gneiss is exposed. The locality is just in the edge 

 of the sheet next the Lake Placid quadrangle on the north. The fault 

 breccia consists of fragments of green, syenitic gneiss cemented by 

 comminuted fragments stained by chlorite. The north and south 

 lines of brecciation and crushing, we are justified in prolonging to 

 the south in the depressions, less well exposed. 



On the east side of the Keene valley along the highway whose 

 extension formerly ran on the south side of Baxter motmtain, and 

 about a mile from the East branch of the Ausable river, is Beede's 

 rotten stone quarry. On the north side of the road, sheeted, crushed 

 and decomposed anorthosite is quarried and used for macadam with 

 excellent results. The decomposed belt, as exposed, is nearly 100 

 feet broad and has knots of less altered rock in it. The strike of 

 the sheeting is almost due east and west, referred to the true north, 

 and dips 45° to 55° north. It would supply a line of weakness for 

 the development of an east and west valley, such as the one on 

 whose side it appears. 



From the positive and well-exposed lines of east and west and 

 north and south crushing, we are justified in inferring a series of 

 faults with these strikes. We note, also, that their direction corre- 

 sponds to some pronounced features of the relief, such as the Keene 

 valley and the valley of Elk lake. 



Study of the map will also bring out the fact that the crushed 

 and decomposed exposure at Beede's rotten stone quarry is at the 

 junction of the east and west fault-lines with one which comes to it 

 in a southwest direction from the pass immediately southeast of 

 Baxter mountain proper and which is prolonged farther to the south- 



