EMBANKMENTS IN CUUllCHILL VALLEY. 



121 



On the west side of the gap through which the Carson River leaves 

 Churchill Valley there is a group of curved bars that were built out from a 

 small butte, once an island in Lake Lahontan, by currents flowing out of 

 Churchill Valley. A note-book sketch of these structures is reproduced 

 below, on a scale of about 500 feet to 1 inch, which will serve to indicate the 

 character of the phenomena found at this locality. 



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Fig. 21.— Sketch of gravel embankiuents iu Cburcbill Valley, Nuvad.i. 



These bars or embankments are quite similar to those near Allen's 

 Springs (see Plate XIX), and, as is so frequently the case, have been built 

 from the bottom up; the higliest in the series is the youngest. Iu examples 

 of this nature, however, the deposits made as the waters fell may have been 

 added to the surfaces of the older structures. This is indicated in the ex- 

 ample shown in the sketch, by the fact that the outer scarp of the higher 

 terrace a has been cut away, the material removed being spread out over 

 the embankments c and d. In the illustration, a is about 20 feet below the 

 Lahontan beach, while h is 20 feet lower. The surface of c is 25 feet lower 

 than h, and on the same general level and Both c andd decline gradually 

 in elevation towards the distal extremity. The longest of the bars has been 

 truncated bv the erosion of the waters whicli sometimes flow down the 

 arroyo shown in the sketch 



In the northern part of the Lahontan basin, fine examples of water- 

 built fjravel embankments mav be seen at the nortliern end of the Slumber- 



