260 ELWOOD S. MOORE 
have not as a rule suffered extensive erosion. Few fossils have 
so far been found in the lower portion of this series and only a 
few distinct gastropods in the upper portion. ‘There are, there- 
fore, differences of opinion regarding the geological age of this 
series but it should probably be regarded as a transition stage 
between the Cambrian and the Ordovician. 
Above this transition series, which is exposed only in the eroded 
crests of the anticlines, there are several thousands of feet of 
fossiliferous limestones which may be regarded as typically Ordo- 
vician and these are overlain by about five hundred feet of Utica 
shale of the Upper Ordovician. Following the shale are the 
Medina conglomerate and sandstone, which occupy the synclines 
of the original folds and cap the present mountains. 
THE TRANSITION SERIES 
The greatest interest in this area centers around the transition 
series. It shows very frequent alternations of dark, crystalline, 
magnesian limestone through odlitic limestone, arenaceous and 
very fine grained, white limestone to calcareous and also nearly 
pure white sandstone. With these strata occur numerous beds 
of chert and siliceous odlite, some iron ore and cherty sandstone, 
the latter due to secondary infiltration of silica and iron. Many of 
the limestone beds show numerous cavities which have been formed 
by solution and these are often partly filled with quartz or calcite, 
indicating extensive transportation of mineral matter. 
The mixture of sand and limestone has produced conditions 
favorable for a great amount of water circulation and chemical - 
activity and the ready disintegration of this series of rocks, with the 
result that vast quantities of loose sand, and fragments of chert 
and sandstone have been left on the surface, destroying the agri- 
cultural possibilities where the series is exposed and producing the 
area locally known as the “ Barrens.” 
CONCRETIONARY STRUCTURES 
There are a variety of concretions occurring in the region under 
discussion. In the Utica shale there are many limonite concretions 
consisting very largely of argillaceous material but often containing 
