CHAPTER II. 



AREA A— SAN MIGUEL AND DOLORES RIVERS— SAUCER 

 VALLEY— GYPSUM VALLEY— BASIN PLATEAU— PARA- 

 DOX VALLEY— SAN MIGUEL PLATEAU. 



Area A includes about 1,000 square miles, lying between the San 

 Miguel and Dolores Rivers, and bounded on the south by the parallel 

 of 380. (See map, plate VIII.) 



DRAINAGE. 



The drainage of the area is by branches of the San Miguel and Dolores. 

 The larger streams head in the Lone Cone group of mountains. The 

 general direction is toward the northwest, and the changes in course are 

 usually abrupt, many of the streams changing at right angles to their 

 former courses. This gives a zigzag appearance to the drainage. The 

 two general courses followed are northwest and northeast. 



KIO SAN MIGUEL. 



The Rio San Miguel was partially described in the Report for 1875, 

 and little need be added here, except what is necessary to make the de- 

 scription of the area complete. The river forms the eastern and a por- 

 tion of the northern boundary of the area. Where the Indian trail from 

 Muache Creek crosses the river, the canon is 800 feet in depth. The 

 massive sandstones of the Upper Dakota group (Cretaceous) form the 

 top of the canon wall. The more shaly beds of the Lower Dakota group 

 are exposed in places below, but are generally concealed by the debris, 

 which is overgrown with pines and cedars. Whether there are any 

 Jurassic layers outcropping it is impossible to say positively. Lower 

 down on the river they undoubtedly occur. The river-bottom is very 

 narrow, and in some places must disappear. There are cottonwoods 

 {Populus halsamifera) and the growth of shrubbery common along the 

 Western streams. The river is rapid, flowing over a rocky bottom. 



From the crossing it keeps an almost northerly course to the mouth 

 of Muache Creek, which comes in from the east. It then flows north- 

 west for three or four miles, when it turns to westward, keeping this course 

 for about seven miles. The next direction assumed is parallel to that of 

 the streams rising in the crest of the Uncompahgre Plateau, viz., south- 

 west. In this portion of its course the river emerges from its narrow 

 canon and flows through alluvial bottoms of considerable width — the 

 walls on either side not being over 400 feet in height — composed of the 

 Dakota sandstones, with cappings of the shales of the Middle Creta- 

 ceous. 



About a mile and a half below the mouth of Naturita Creek the San 

 Miguel turns to the northwest and flows in caiion to its mouth. The 

 caiion at the head is 400 feet deep, and at the mouth 1,000 feet or more. 



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