ABSTRACTS AND DISCUSSIONS OF PAPERS 81 



LANDSLIPS AND LAMINATED LAKE GLAYS IN THE BASIN OF LAKE BASCOM 



BY FRANK B. TAYLOR 



(Abstract) 



Lake Bascom was a sprawling glacial lake which filled the valley of Hoosick 

 River and its branches in northwestern Massachusetts, southwestern Vermont, 

 and adjacent parts of New York. The lake was 500 feet deep near Williams- 

 town and slightly deeper toward Pownal. Many landslips have occurred around 

 the sides of the main deep part of the lake and a few in ravines which held 

 narrow bays. Laminated pebbleless lake clay and silt covers a considerable 

 part of the lake floor around Williamstown and eastward toward North Adams, 

 •and it also occurs between North Adams and Briggsville and northward and at 

 Petersburg and near North Pownal. During some of the later, lower stages of 

 the lake, pebbleless clay and silt were deposited near Hoosick, around Hoosick 

 Falls and North Hoosick and near North Bennington. Other laminated clays 

 on the Owl Kill and on the Hoosick below Eagle Bridge are not related to 

 landslips. 



At its highest level Lake Bascom stood at an altitude of 1,125 or 1,130 feet 

 above sealevel. With three or four exceptions, all the landslips observed in 

 this region occur in the basin of Lake Bascom at some distance beloAV its 

 highest level. Some of the largest slips are very old. surely Pleistocene in age. 

 In all probability they occurred soon after the fall of the lake waters. They 

 are now represented by a series of steplike benches at certain places on the 

 hillsides. Other slips are more recent and some are still in active movement. 

 In one place they are just beginning, the bluff back of the edge of a previous 

 slip being riven by deep cracks. 



Nearly all of these landslips are related to underlying beds of laminated 

 pebbleless lake clay and silt. The slips generally occurred on steep slopes 

 where a stream was cutting at the bottom and where the underlying beds at 

 or above the stream level were lake clay and silt. Some, however, are not 

 related to any stream. The weakness of these beds, increased by softening in 

 seasons of prolonged rain, caused a yielding and a slipping down of the heavy 

 overlying masses. In some slips the laminated beds are partly exposed in ver- 

 tical sections in the bluff at the back of the slipped mass ; in others the clay 

 beds are exposed in the banks or bed of the stream, where they are generally 

 distorted. 



A few landslips of a different character, perhaps more appropriately called 

 landslides, occurred recently (August 20, 1901) on the east face of Mount 

 Greylock. These were much smaller masses than some of the slips in Lake 

 Bascom, but the amount of their descent was much greater, being in one case 

 1,500 feet. These slides occurred after a prolonged wet period and have no 

 relation to lake clays. 



Presented in abstract extemporaneously. 



Discussion 



Mr. George C. Martin stated that Lake Bascom was evidently very similar 

 to some of the marginal lakes on the borders of the existing Alaskan piedmont 



