VALLEY FORGE NATIONAL PARK
Below is a simplified geologic map of Valley Forge National Park and the surrounding area. The geologic map shows the distribution, age and structural relationships of the major rock units. The various rock units are distinguished by different colors and different letter symbols. The letter symbols are abbreviations for the names of the geologic units and are keyed to the legend at the left. The capital letter refers to the age of the unit and the small-case letter refers to the formation name (for example, TRs = the Triassic Stockton formation). Dark lines are contact lines which separate different geologic units.
(Wiswall, C. Gil, 1993)