Bureau of Topographic and Geologic Survey

Pennsylvania Folds Map and GIS Data Available Online      

Folds (such as those shown in the photo above) are a prominent structural feature of the rocks in most of Pennsylvania, and although there have been hundreds of maps showing these folds, there has never been a comprehensive, regional map of Pennsylvania folds until now. The Pennsylvania Geological Survey is pleased to announce the publication of Open-File General Geology Report 11–01.0, Folds of Pennsylvania—GIS Data and Map. The fold axial traces and structural fronts included in the dataset and map were compiled over many years by structural geologist Rodger T. Faill, a geologist supervisor (now retired) at the Survey. The GIS data and map are 1:500,000 scale, and as such, folds at outcrop scale and many folds less than 1 kilometer long are not included in the dataset. On the map PDF, folds less than 3 kilometers long are not shown. Likewise, where mapped fold axial traces were closely spaced, Faill showed them as one line.

The fold axial traces in the GIS geodatabase are attributed for names (most are unnamed) and types of folds (anticline, syncline, anticlinorium, synclinorium, dome, or multiple folds). Named folds have additional information associated with them, including fold measurements and a list of the source maps and reports that showed or referred to the folds. On the map, folds longer than 30 kilometers have been labeled where space permits, and color has been used to identify the fold type.