THE ORIGIN OF CERTAIN PALEOZOIC SEDIMENTS 233 
carried away. The soluble constituents, on the other hand, and 
particularly the lime carbonate, were being carried away in solu- 
tion. This furnished the material for the thick calcareous deposits 
of early Ordovician time. 
After this calcareous material was carried to the sea, the ques- 
tion arises as to how it was separated from solution and deposited 
as limestone. Marine animals could have done the work, but 
these deposits are strikingly unfossiliferous except at very widely 
separated horizons, and there are many peculiarities of the rock 
which cannot be explained upon this basis. Chemical precipita- 
tion has been suggested as a possible explanation, but this, too, is 
inadequate, as will be presently shown. The object of the present 
paper is to outline the probable course of events in Upper Cambrian 
and Lower Ordovician time which, it is thought by the author, will 
best explain the origin of these deposits and some of the peculiar 
physical characters which they now possess. The observations 
and deductions here recorded are largely based on field investiga- 
tions carried on in the vicinity of Bellefonte and State College, 
Center County, Pa. 
Rocks ranging in age from the Upper Cambrian through the 
Ordovician are exposed in an unsymmetrical eroded anticline which 
extends in a northeast-southwest direction across the Bellefonte 
quadrangle between the Bald Eagle Mountains on the northwest 
and Nittany Mountain on the southeast. This anticline pitches 
toward the northeast. Its northwestern limb is generally almost 
vertical and in some places even overturned by a few degrees. 
The southeastern limb, on the other hand, has very gentle dips, 
generally ranging from 8 to 15 degrees. 
The lowest beds exposed are composed of limestone of variable 
character containing Cryptozoon proliferum in abundance and 
trilobites of Upper Cambrian age, the latter limited to thin fossil- 
iferous layers. The fossiliferous layers are frequently oélitic and 
other odlitic layers occur. In addition to these, occasional layers 
of a peculiar conglomerate are found. This conglomerate is com- 
posed of broad, thin pebble-like structures ranging from half an 
inch or less up to three or four inches in diameter, and generally 
less than half an inch thick. The edges are rounded, the outline 
