PROCEEDINGS OF THE ACADEMY AND AFFILIATED 



SOCIETIES 



THE GEOLOGICAL SOCIETY OF WASHINGTON 



The 304th meeting assembled in the lecture room of the Cosmos 

 Club on February 9, 1916, and immediately adjourned out of respect 

 to the memory of Dr. C. Willard Hayes, past President. 



The 305th meeting was held in the lecture room of the Cosmos Club 

 on February 23, 1916. 



REGULAR PROGRAM 



Charles Butts: Faults of unusual character' in central Pennsyl- 

 vania (Illustrated). In the vicinity of Henrietta, in the southeast 

 corner of the Hollidaysburg quadrangle, Pennsylvania, a wedge-shaped 

 block 8 to 10 miles long and 2 miles wide at base is thrust up between 

 younger rocks. The maximum throw is at the point of the wedge 

 at the north end where the Waynesboro formation, of Middle Cambrian 

 age, is in contact with dolomite of Beekmantown age. The relations 

 resulting from the converging faults are abnormal for the Appalachian 

 valley. The fault block is overthrust along the west fault and rela- 

 tively downthrown along the east fault. The west fault is the major 

 one and seems to extend northward for a long distance. It, or one in 

 the same line of disturbance, is revealed in a cut of the Pennsylvania 

 Railroad at Birmingham, Pennsylvania, where the fault plane dips 

 eastward about 15? 



Several possible explanations were given for the abnormal relations 

 along the fault on the west side of the wedge: First, that it is a nor- 

 mal fault downthrown on the east; second, that it was formed long 

 subsequent to the west fault and after deep erosion, the movement 

 being along the bedding plane of the base of the Beekmantown lime- 

 stone; and third, that it took place along a second original fissure 

 east of that along which the main overthrust occurred, at a time 

 when the arch was completely overturned in such a way as to bring 

 the second fissure into line with the direction of the maximum pressure 

 of the overthrusting force. 



Laurence LaForge: Resume of the geology of southeastern New 

 England in the light of field work since 1908 (Illustrated). No abstract. 



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