LAKE BEDS. 183 



bed of the gulch at the entrance to the north branch of this amphitheater, 

 their northern and eastern continuations being found near the top of the 

 adjoining cliffs. 



Lake beds. — From a little south of the mouth of Weston's gulch north to 

 the valley of the East Arkansas, the gently-sloping, flat-topped, lower spurs 

 of the range are formed of the Lake bed deposits already described. Actual 

 outcrops of these are only found in the southern portion of this region, as 

 in the neighborhood of Leadville they are covered by rearranged moraine 

 material, which has received the local name of "Wash." The best oppor- 

 tunities for observing these within the area of the map are on a narrow 

 ridge south of Little Union gulch and along the south wall of Lower Empire 

 gulch. At the former locality is exposed a thickness of 300 feet of outcrop- 

 ping beds sloping regularly 3° to the westward, which is also the slope of 

 the adjoining mesa-like ridges. They con.sist of gravel and coarse sand, al- 

 ternating with beds containing' large subangular or partially rounded frag- 

 ments of the various rocks which make up the higher portions of the range. 

 On the top of the ridge facing lower Empire gulch they have been opened 

 by prospect holes, and show a conglomerate with lime cement overlying a 

 bed of granite sand, with one iron-stained streak between. Here the dip is 

 still 3° to the westward, but in the bed of Empire gulch, where the stream is 

 deflected from its course by a knob of Archean granite projecting about 150 

 feet above the valley, they are found to have a dip of 15° to the northeast, 

 showing that there has been some local movement since they were deposited. 

 There are several outlying j^atches of these beds left high up on the spurs 

 in the region shown on the Leadville map. Since the presence of the 

 beds within this area could only be proved by underground workings, the 

 outlines there given are necessarily somewhat hypothetical, and may be 

 subject to change when they shall have been pierced by shafts at other 

 localities. The highest points at which their existence has been proved 

 in this area are on the western slopes of Long and Derry and Printer Boy 

 Hills, respectively, where they extend up to the 11,000-foot curve. This 

 is just 1,000 feet above the outcrops between Little Union and Empire 

 gulches, -and higher than the dip of 3°, already a very considerable in- 

 clination for an average angle of deposition over a large area, would carry 



