102 
ROLLIN D. SALISBURY 
Areas beyond the Limit of Glaciation,” which was set forth in 
a long special chapter of R. Ellsworth Call’s report on the region, 
as one of the monographs of the Arkansas Geological Survey un¬ 
der the directorship of Dr. John C. Branner. The scope of the 
thesis was briefly but clearly stated: “In the central part of the 
basin of the Mississippi River, below the latitude of glaciation, the 
difference between the deposits made by the waters originating in 
the melting ice and the subjacent strata appears to be much less 
obvious than in many other regions. In consequence, the recog¬ 
nition of the Pleistocene formations along the course of the Missis¬ 
sippi south of the limit of the general drift sheet, and therefore 
the correlation of the northern and southern Pleistocene forma¬ 
tions has not been free from difficulties. Crowley’s Ridge, run¬ 
ning from Helena northward to the northern boundary of the 
State and beyond, lies within the region where correlation is most 
difficult. 
Northern Glacial drift does not exist on Crowley’s Ridge at 
any point, nor does the northern terminus of the Ridge reach the 
southern limit of ice-action during the age of ice. Nevertheless 
the Ridge was affected by one of the agencies operative in the 
Glacial Period. In common with the other highlands bordering 
the Mississippi Valley, Crowley’s Ridge is essentially covered by 
loess. With minor interruptions due to erosion subsequent to the 
deposition of the loess, this formation is laterally continuous with 
the loess which reaches northward to and beyond the southern 
limit of Glacial drift, where the relations of the two formations 
are easily determinable. This continuous sheet of loess, in its 
relationship to the drift, which underlies it at the north, and to 
extra-drift formations which underlie it at the south, furnishes 
one of the best means now at command for determining the rela¬ 
tions between the Pleistocene and pre-Pleistocene formations in 
the area south of the limit of glaciation.” 
This was a masterly attempt to derive from the same source 
genetically the southern loess mantle along the Mississippi River 
and the northern Glacial drift sheets. But in that day no such 
thing as a special desert geology was dreamed of, nor was the 
loess and the black loams of the prairies yet connected with the 
gray adobe soils of the arid regions, the exported dusts from the 
deserts. The chief arguments urged for the origin of the loess 
