HUMBOLDT VALLEY. 741 



For this reason, the Pliocene beds are represented on the geological 

 map as forming a continuous belt along the river, although the outlines of 

 formations are not definitely known. 



Except in one or two places, where the river cuts a deep channel into 

 the strata, there are no very good exposures, much better sections being 

 found in the high bluffs on the Carson and Truckee Rivers. The best ex- 

 posures, however, are seen east of Rye Patch Station, where the river for 

 several miles flows in an exceedingly narrow channel, with nearly precip- 

 itous sides eroded in the Humboldt Pliocene beds, the walls having an 

 average height of 200 feet, and in places reaching over 300 feet. The sec- 

 tion shows a regular horizontal series of sands and finely-comminuted 

 arenaceous clays, interstratified with indurated clays, but no beds of coarse 

 conglomerate. Very similar bluffs occur just north of Oreana. No fossils 

 were found. Directly west of Oreana, and extending thence southward to 

 Ijovelock's Knob, there is an exposure for 10 miles of the upper members 

 of the Humboldt Pliocene, which here also are made up of clays and fine 

 lands, as shown in the eroded ravines and basins. Abundant evidences are 

 seen of the La Hontan Lake terraces, with a series of well-marked, succes- 

 sive beach-lines descending nearly to the level of the desert, scattered over 

 which are fragments of the old lake tufas. 



Organic remains are quite rare from the Humboldt Pliocene : the only 

 vertebrate bones, so far as known, that have ever been found were taken 

 from a cream-colored earth near Fairbank's Point, at the end of the Haval- 

 lah Range, and have been pronounced by Prof 0. C. Marsh as belonging 

 to the Pliocene horse. Invertebrate remains seem equally rare, and have 

 only been observed in an isolated patch of light-colored limestone, which 

 rests unconformably upon the Star Peak beds, just south of Mill City, Its 

 relations with the other Pliocene strata are quite unknown, similar beds 

 not having been recognized in the valley. Prof F. B. Meek, to whom 

 they were referred, regarded them as undoubtedly fresh- water Pliocene 

 forms. 



In the middle of the broad valley west of Humboldt Station, there is an 

 interesting locality of basalt, rising out of which are numerous low domes 

 and crater-like mounds of vesicular basalt, having all the appearance of 



