PHYSIOGRAPHIC DEVELOPMENT IN COLORADO 



T-2>3 



preserve the form of those that might have existed and probably 

 were too fissile to allow the production of potholes on the scale 

 to which they appear to have been developed in the granite. 



4. Interrupted and reorganized drainage lines. — The interrupted 

 and reorganized drainage lines are directly the result of the ice 

 occupation of units 2 and 4. 



The diagrams in figures 6 and 7 suggest a possible analysis of 

 the drainage before and after the early glaciation. The valley of 



Fig. 6. — Diagram of the present drainage of the area showing influence of early 

 and late glaciation on the present drainage lines. 



Muggins Gulch is suggested as the outlet of the upper Thompson 

 in preglacial times. The North Fork is shown as the headwaters to 

 the lower part of the Thompson of today. Small tributaries to 

 each occupied the present course of the Big Thompson between 

 Estes Valley and Drake and were separated by a low col. 



The early ice gathered on the highlands to the west and moved 

 down the Estes Valley as far east as Mount Olympus, while small 

 valley glaciers filled in Black Canyon and the valleys around 

 Ol3anpus and Pisgah. Probably Park Hill and Muggins Gulch were 

 also full of ice, and possibly all of the Estes Valley south to include 



