TERTIARY LAKE BASIN OF FLORISSANT 151 



Many of our smaller mountain "parks" or meadows in Colorado 

 are the result of the silting up and drainage of glacial lakes, though 

 if stratified deposits were formed in the lakes, they have usually been 

 almost wholly worked over and destroyed by the subsequent mean- 

 dering of the streams. Such parks in many respects resemble the 

 Florissant valley. Compared with Estes Park, South Boulder Park, 

 Nederland meadows, and other more northerly valleys which are 

 becoming well known to the traveling public, the Florissant basin 

 is more open, not as well defined, and presents an aspect of greater 

 age. The surrounding mountains are neither as high nor as abrupt, 

 being for the most part rounded into gentle slopes, without deep, sharp, 

 V-shaped gorges. The highest point within a radius of several miles 

 is only i,ooo feet above the village of Florissant, which is situated 

 on the present floor of the valley, a little over 8,000 feet above sea- 

 level. 



Two other Tertiary lake basins are noted on the maps of the Pike 's 

 Peak foho, but they are of later origin, being considered Neocene. 

 One is called Alnwick Lake, the other High Park Lake. They are 

 a few miles south of Florissant, one immediately northwest and the 

 other southwest of Cripple Creek. Their deposits are very different 

 from those of Florissant, consisting of sandstones and conglomerates, 

 and seem to be devoid of fossils. 



EXPLANATION OF FIGURES 



Fig. I.— Outline map of Florissant Tertiary lake basin, following Folio No. 7, 

 Geological Atlas oj the United States. The present extent of lake beds is indicated 

 by dotted area. Drainage at present is shown by the courses of the streams. 



Fig. 2.— a, original slope of valley floor. B, water level at beginning of over- 

 flow at northwest end. C, valley floor after supposed tilting. D, valley floor 

 after cutting down of barrier and draining of lake. E, dotted line represents the 

 possibility of the axis of deformation having divided the lake near the southern 

 extremity. Vertical scale is greatly exaggerated. Left of figure is southeast; 

 right of figure is northwest. 



Fig. 3.— Fossil Sequoia stump. The framework was erected at the time that 

 an attempt was made to cut sections of the stump for exhibition. 



