NEW METHED OF CALCULATING DATE OF GLACIAL EPOCH 735 



NEW M£1TH0D OF CALCULATiyO THE DATE OF THE GLACIAL EPOCH 

 BY BUFUS M. BAGG, JR. 



(Abstract) 



The antiquity of the lee age can possibly be determined by the rate of peat 

 formation upon Block Island. The peat beds lie in practically unchanged 

 glacial kettle hole basins which are believed to have begun to form imme- 

 diately upon the recession of the ice margin in New England. These basins 

 have been undisturbed by natural drainage and afford unusual facilities for 

 calculating the date of the Ice epoch based upon the peat infilling overlying the 

 glacial till of the island. 



The paper dealt with the problem of peat formation in a limited manner, 

 laying particular stress upon the time factor under conditions known to exist 

 in New England. 



The reasons why this method would not hold in other localities were set 

 forth in the paper as submitted. 



PHYSIOGRAPHIC STUDIES IN THE SAN JUAN DISTRICT OF COLORADO 

 BY WALLACE W. ATWOOD 



(Abstract) 



After a brief season in the core of the San Juan Mountains during the 

 season of 1909, plans were made for a detailed physiographic survey, in 1910, 

 of the southern and southwestern slopes of the range. Remnants of an an- 

 cient peneplain have been mapped. Thej^ have an elevation of about 8,000 

 feet in the mesa-plateau district bordering the range and increasing elevations 

 up to at least 11,000 feet on the mountains. Small beautifully rounded peb- 

 bles rest at many places on the peneplain remnants in the mountains, but 

 south and southwest of the range the peneplain remnants are mantled by a 

 coarse boulder-gravel formation. The boulder-gravel formation extends at 

 least 50 miles from the base of the range, and may prove to be an important 

 horizon in correlating the physiographic histories of the San Juan range and 

 the Colorado plateau. Later stages of erosion and glaciation are recorded by 

 appropriate features and deposits. The physiographic studies may make cer- 

 tain important contributions to the interpretation of the late Tertiary and 

 Quaternary deformations of the San Juan dome. 



Discussion 



Mr, Rich : Along the northern flank of the Uinta Mountains Is a gravel- 

 covered peneplain probably to be correlated with the higher peneplain of the 

 San Juan area. The general characteristics and age relations confirm Mr. 

 Atwood's suggestion that peneplains similar to the San Juan may be found in 

 connection with other Rocky Mountain ranges. 



Prof. W. M. Davis remarked on the nicely rounded pebbles of the peneplain 

 surface. 



