920 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1946: 
hand, even without the presence of pyroclastic material, fluorine-bear- 
ing gases from the known volcanic vents may have furnished some 
fluorine to the Dakota as it was being deposited. From this source 
and from fluorine-bearing detrital minerals in the sediments, un- 
usually large amounts of fluorine might be released by the unusually 
large amounts of pyrite. 
In other areas for which the fluorine-yielding aquifers are known, 
it has not in general been possible to discover any specific conditions 
that might account for the fluorine concentration. In Illinois the 
Dresbach, St. Peter, and Niagara formations, and in some places the 
glacial drift, have been identified as sources of toxic amounts of 
fluorine. In Oklahoma, waters from the Arbuckle, Clear Fork- 
Wichita, and Ogallala formations, and from recent alluvium are all 
rich in fluorine. The Ogallala sandstone, of Tertiary age, presents an 
interesting case. Throughout the Panhandle area of Texas and Okla- 
homa it is the chief aquifer, but since erosion has cut it off from rainier 
areas in the Rocky Mountains region to the west, its water must all be 
derived from local rainfall. Well water from the Ogallala typically 
has a toxic fluorine concentration, part of which may be acquired from 
the Ogallala itself, which contains some layers of volcanic ash. Some 
of the fluorine, however, must certainly be derived from the overlying 
materials through which the water has to pass to reach the Ogallala. 
Dr. Edward Taylor, director of dental health, Texas State Board of 
Health, reports * that in Deaf Smith County, Texas, the topsoil con- 
tains 250 p. p. m. of fluorine. At a depth of 8 feet this increases to 
2,500 p. p.m. A number of volcanoes in New Mexico, active in 
Pleistocene time and erupting ash that was deposited throughout the 
Great Plains,” were probably the source of this fluorine. Perhaps 
similar conditions, with fluorine being supplied from overlying for- 
mations, may exist for some of the other aquifers which are appar- 
ently rich in fluorine but for which no explanation of the fluorine 
content is evident. 
CLIMATE AND THE FLUORINE CONTENT OF WATER 
Ockerse 8 reports that in South Africa the areas of low rainfall 
“have, generally speaking, a higher fluorine content in their under- 
ground water than the high-rainfall areas * * *. The soils and 
rocks in the low-rainfall areas have not been leached of their minerals 
to the same extent as those in the high-rainfall areas.” Such a re- 
lationship can of course be demonstrated only for surface and shallow 
well waters, since artesian aquifers are not subject to climatic in- 
fluences. In the United States in general the surface and shallow 
26 Letter, December 6, 1945. 
71 Landes, K. K., Voleanic ash in Kansas, Bull. Geol. Soc. Amer., vol. 39, pp. 931-940, 1928. 
28 Ockerse, T., Endemic fluorosis in South Africa, Union of South Africa Dep. Publ. Health, 
p. 12, 1944, 
