348 GLACIAL GRAVELS OP MAINE. 



describe the last part of the last g-lacial j)eriod. Eariier the lateral glaciers 

 may have been confluent in an ice-sheet which covered all the Arkansas 

 Valley from mountain to mountain. 



We also here have the same alluvial aprons we find in the San Juan 

 valleys. Not being- confined in a narrow valley, they take the characteris- 

 tic form of the alluvial cone radiating from the terminal moraines. The 

 aprons are somewhat distinct as far south as Buena Vista; then they merge 

 into a plain of coarse water-rounded matter that occupies the valley to a 

 point beyond Pueblo, except where it has disappeared owing to erosion. 

 Some of this water-rolled matter came from the Wet Mountains and the 

 Sangre de Christo Rang-e, but most of it came down the main Arkansas 

 River. 



The general law of frontal aprons of glacial gravel is that they become 

 finer as we go away from the principal terminal moraines. Fi'om tlie mouth 

 of Lake Creek to near Buena Vista there are multitudes of water-rounded 

 bowlders in the plain of rolled matter that here covers the eastern part of 

 the Arkansas Valley. Many of them are from 6 to 10 feet in diameter. 

 Of course it is not meant to assert that they were not glaciated before 

 being worn by the action of water. Below this point the material becomes 

 finer. 



Ennuons has described the so-called "Lake beds" at Leadville. I 

 have discovered there were local glacial lakes not far from Twin Lakes and 

 at other points in the valley. They formed between the tongues of ice 

 that then projected into the valleys and formed dams across it extending to 

 the main valley glacier. 



PIKES PEAK RANGE. 



Grlaciers formed in the valleys of some of the branches of West Beaver 

 Creek that were 3 to 4 miles in length; also in the deep canyon-like valley 

 that extends north from the peak, but I have not explored the latter system- 

 atically. A glacier formed on the south sloj)es of Pikes Peak in the valley 

 of East Beaver Creek. Its terminal moraines form the dams that confine 

 the Seven Lakes. The morainal matter is itself somewhat sandy and 

 water-washed, but the valley below here contains no overwash apron of 

 glacial gravel. Probably there was some rather fine sediment, but it has 

 now disappeared by erosion on a steep slope. The length of this glacier 

 was not far from 3 miles. 



