Major Aquifer Material Types in Pennsylvania

In the simplest terms, the four aquifer material types are distributed across Pennsylvania as shown in the following map. Carbonate aquifers are made up of limestone and dolomite and, when at or near the land surface, are the most vulnerable to contamination. The noncarbonate aquifers are: crystalline aquifers typically comprised of schists or other metamorphic or igneous rocks; siliciclastic aquifers commonly comprised of sandstones, siltstones, and shale; and surficial aquifers often comprised of unconsolidated sands and gravels.