( 1 P R A RY 
OF THE. 
UHlVERSITYoMLLINOIS. 
THE 
AMERICAN GEOLOGIST 
Vol. XXI. MARCH, 1898. No. 3 
GEOLOGY OF THE ST. CROIX DALLES. II. 
By Charles P. Berkey, Minneapolis. 
(Plates XII and XIII.) 
Part II.— MINERALOGY. 
Chapter I. Litliology of the Sedimentary Roeks. 
Magnesia)! Series. A description summarizing thi' 
lithologic character of the Jordan sandstone and St. Law- 
rence shales has been pubhshed by Hall and Sardeson." 
There are few things of sufficient note, in the very limited 
extent of these rocks within this area, to demand extended 
discussion. The St. LawTence. however, at this locality pre- 
sents a splendid development of alternating bands of sand and 
green shale, as illustrated in an accompanying figure. The 
hand specimens from which the photograph was taken were 
obtained at the foot of the falls at Osceola and belong to the 
St. Lawrence formation. It is especially noticeable that the 
sandstone bands are quite ])ure and in sharp contrast with the 
green shale bands. This contrast holds good even where the 
bands are very irregular. It seems to indicate that the orig- 
inal material came either from two very different sources, or 
at very different rates of accumulation, or that this was the 
scene of greatly disturbed sedimentation, such as might be 
occasioned by an unstable ocean current or in a shallow bay 
subject to violent storms. 
*Bull. Geological Society of AiiK-rica, vol. Ill, 1892, p. 345. 
