Keyes—Meteorites on the Painted Desert. 135 © 
The so-called lake-beds are mainly composed of coarse 
silts. Their great thickness and uniform lithologic char- 
acter might be difficult to explain were it not for the fact 
that other depressions exist in the vicinity that still re- 
tain their waters. A single local ‘‘cloud-burst’’ may fill 
with water such an enclosed basin to a depth of a dozen 
or a score of feet, as shown in the sudden rise in the level 
of the Laguna del Perro in eastern New Mexico,'! the 
overflow of the Rio Carmen in the San José bolson in 
Chihuahua, Mexico,’* and the appearance of the ephem- 
eral lakes in the Rio San Juan valley in Tamalipas state. 
Zuni Salt-Lake, a few miles east of the Coon Butte, occu- 
pies a similar crateriform depression in the plain and 
out of its waters rise two small ash-cones. 
The filling of such ephemeral pools and other bodies 
of water in the desert must be exceedingly rapid. The 
well-known playa formations are one phase. Certain of 
the so-called Tertiary lake deposits of western United 
States are another. Desert soil accumulations some- 
times are a third sort. In physical characteristics the 
resemblance of all of these deposits to the loess is as re- 
markable as it is genetically suggestive. 
Wind-blown dusts of the desert are caught and retained 
by bodies of water, and under favorable conditions enor- 
mous deposits are rapidly built up. The vast boracif- 
erous clays, 5000 to 8000 feet in thickness, of southern 
California are thus explained.!* The great inland sea, 
or arm of the Pacific ocean, once covering the deep Death 
valley, the Mojave basin and the Santa Clara valley is 
regarded as long in drying up. The disappearance of 
the water may have been more rapid tlian the great thick- 
ness of the terranes at first thought suggests, for the 
reason that as an accompaniment of the evaporation of 
the waters in an excessively dry climate there must have 
been a filling-up of the basin by the prodigious quantities 
™ Journ. Geol. 16:434. 1908. 
” Am. Jour. Sci. IV. 16:378. 1903. 
*% Trans. Amer. Ins. Mining Eng. 40:674. 1909. 
