T. N. Dale — Algonkian-Camhrian Boundary. 121 



the first period of disturbance; a later one induced in the rock 

 the regional schistosity of the range striking JSf. 10° to 15° E." 



The gist of Mr. Keith's note is that the Cambrian quartzite 

 and conglomerate of Vermont uneonformably overlie a great 

 thickness of schist, dolomite, graywacke, quartzite and con- 

 olomerate and that " these older sediments bounded above 

 and below by conglomerate and unconformities are properly 

 classed as Algonkian." 



Structure. — While at many points along this boundary the 

 rocks on both sides of it appear to be conformable, at others 

 the divergence between the strike of the foliation of the pre- 

 Cambrian gneiss (and the bedding of the rocks associated with 

 it) and that of the bedding of the Cambrian beds amounts to 

 from 18° to 140°. The pre-Cambrian strike ranges from 

 N. 30°-90° W., averaging N. 70° W. The Cambrian from 

 N. 12 p W. to N. 50° E., averaging N. 30° E. 



These structural relations can be observed at the following 

 points : In the town of Jamaica, in the deep E.-W. cut made 

 by the West River, two miles north of Jamaica village, the 

 granite-gneiss strikes N. 30° W. and the Cambrian micaceous 

 quartzite a few hundred feet east strikes N. A mile south on 

 the hill west of Ball Mountain the granite-gneiss strikes 

 N. 4:0° W. and the quartzite near on the northeast strikes 

 N. 20° E. 



In the town of Andover, 12-15 miles north of the Jamaica 

 cut, the granite-gneiss of the north and south humps of Ter- 

 rible Mountain strikes N. 35° to 70° W., but the Cambrian 

 schist along the east base of Terrible Mountain strikes 

 N. 12° W./N. 10° W., K, N. 12° E. 



In the town of Ludlow, 5 miles farther north, on the east 

 side of Ludlow Mountain, where the boundary doubles over on 

 itself for several miles, exposing a tongue of pre-Cambrian up 

 to a mile in width, the granite-gneiss strikes !N\ 45°-90° W., 

 but the Cambrian schist and quartzite east and west of the 

 tongue strike N. 10° to 35° E. 



In the town of Sherburne, 13J miles further north, in the 

 Falls Brook, at the falls two miles E.SE. of Killington Peak, a 

 pre-Cambrian arkose strikes JNT. 30°-40° W., but the Cambrian 

 schist and dolomite a little east of it strike N. 40°-50° E. Six 

 miles further north in the same town, If miles JS T .NW. of 

 Sherburne village, in a small tributary of the Ottaquechee 

 River, pre-Cambrian quartzite and arkose strike N. 35°-40° 

 W. but the Cambrian schist at the foot of the falls and also on 

 the east side of the river strikes N. Two miles further north 

 in the mass east of North Sherburne the pre-Cambrian granite 

 gneiss strikes JS". 57°-70° W. and various sedimentary rocks 

 associated with it strike N. 30°-70 W., but the Cambrian schist 

 east of them strikes N. 



