The purpose of this paper is to present certain general facts respecting the conditions of Appalachian sedimentation which have come to light chiefly through the study of the Pottsville floras. A portion of the results of this study, concerning in particular the nature of the basal Pottsville unconformity and the measures of relative sedimentation, has already been presented in the writer’s papers on the fossil plants. The more advanced stage of the paleobotanical work now permits the revision of certain of the conclusions earlier published while further extending their scope in the realm of the physical geography of the period. The present paper is, however, to be regarded as preliminary, or as a mere report of progress, and therefore subject to further revision on the completion of the paleobotanical studies.
The existence of an unconformity at the base of the Pottsville series in the Appalachian trough . . .