The diagram below is a generalized geologic map of Pennsylvania, modified from Map 7 of the Pennsylvania Geologic Survey. The green circle represents the location of Bucknell University, in Union County. The geology of Pennsylvania may be subdivided into three broad categories: - Flat to gently folded strata of the western and northern portions of the state. These sedimentary rocks were deposited from 400 to 250 million years before present and contain a vast resource of bituminous coal;
- Moderately to tightly folded strata of central Pennsylvania. These sedimentary rocks were deposited from 570 to 290 million years ago and contain valuable reserves of anthracite coal.
- Metamorphic and igneous rocks of southeastern Pennsylvania. These rocks record a complex history of mountain building and opening of the present day Atlantic Ocean. They range in age from nearly 1 billion years to 140 million years before present.
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