The area studied is part of a separate Silurian province which extends south of the coal measures from the Schuylkill River to southeastern New York. It is divided into two parts, southern and northern, each characterized by distinctive faunas and lithology.
Numerous sections are studied embracing beds from the Silurian Bloomsburg to the base of the Middle Devonian Onondaga; their formations are described, faunas given, and beds correlated.
The Middle Devonian Palmerton sandstone and Bowmanstown chert of the southern area, long designated Oriskany, are correlated with the Esopus shale of the northern area. The underlying Oriskany sandstone is present in different facies in the southern and northern areas.
The Helderberg and Keyser groups differ in facies in the two areas. They are briefly described and correlated.
The Silurian Poxono Island shale and Bossardville limestone are present in both areas. They are similar to, and homotaxial with, the Wills Creek shale and Tonolo-way limestone, respectively, of central Pennsylvania and Maryland but lie in a different province, and the corresponding formations differ in their time limits. Both are believed to be later than the Wills Creek shale.
The formations above the Bloomsburg thin progressively and disappear southwest-ward, but the Bloomsburg is continuous throughout the area.
The Keyser limestone presents both Silurian and Devonian aspects. It is tentatively made Silurian, but the determination of its true age must await further study of its relation to the European sequence.