GEOLOGIC AGE AND GEOGRAPHIC DISTRIBUTION. 43 
Analysis of pink clay from Wittsburg. 
[Specimen dried at 110°-115° C. R. N. Brackett, analyst.] 
Silica (Si0 2 ) 69. 55 
Alumina (A1 2 3 ) 15. 20 
Iron oxide (Fe 2 3 ) 8. 10 
Lime (CaO) 58 
Magnesia (MgO) 97 
Potash (K 2 0) 52 
Soda (Na 2 0) 50 
Phosphoric acid (P 2 5 ) 20 
Loss on ignition 5. 72 
101. 34 
Water at 110°-115° C 2. 24 
Air-dried fine white sand 25. 48 
QUATERNARY CLAYS. 
The Quaternary deposits of Arkansas occupy a large area east and 
south of the Paleozoic group. South of Arkansas River these depos- 
its, except along the larger streams, are comparatively thin, and 
between them lie many outcrops of the underlying Tertiary and Creta- 
ceous sediments. North of Arkansas River the Quaternary deposits 
are much thicker. In all the flat country of northeastern Arkansas 
Quaternary deposits completely cover all the older formations. Ter- 
tiary rocks outcrop along the base and sides of Crowleys Ridge. 
Crowleys Ridge enters the State in Clay County and runs due 
south to Helena, in Phillips County. The country traversed by this 
ridge is low and, from a geologic point of view, somewhat monoto- 
nous. Its geology as related to the clays and clay industries can be 
presented most conveniently by a brief statement of the geologic 
features of Crowleys Ridge itself. 
The Quaternary clays of the Crowleys Ridge region are either (1) 
loess or ridge clays, or (2) ridge-land clays, found west of Crowleys 
Ridge. 
The first of these soil and clay groups is found mainly on the 
higher portions of Crowleys Ridge. The second occurs only on the 
more elevated portions of the low country, but its chemistry and 
distribution present certain peculiar and interesting facts that call 
for its separation from the soils of the lowlands proper. 
From Helena nearly to Jonesboro the loess is the characteristic 
soil of the higher portions of Crowleys Ridge. At some places where 
ravines are eroded along the eastern margin of the ridge, at right 
angles to its trend, this material forms precipitous walls, the bot- 
toms of which rest on gravels and sands. In other localities loess 
soils overspread the slopes of the hills to varying depths. These 
redeposited loess soils are not so homogeneous as the undisturbed 
