Small patches, or long linear areas (running parallel to ridgetops)
Usually lower- to middle-elevation slopes, but sometimes on upper slopes and wide ridges, as on Maryland Heights
Dry to moderately dry; relatively high in base elements that support plant growth, such as calcium and magnesium
Varies: Harpers Formation, Weverton Formation, Tomstown Formation, and Antietam Formation
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As hinted at by its name, the Basic Oak - Hickory Forest grows in areas where the pH of the soil is relatively basic, which promotes plant growth. Ecobit: Defining Terms: Acidic and Basic
Typically, basic soils are underlain by bedrock that contains plenty of base elements. For example, the Tomtown formation is limestone, which is made of calcium carbonate. The Harpers Formation (a metamorphosed siltstone) contains calcium- or magnesium-rich minerals such as mica, chlorite, and/or feldspar.
However, on Maryland Heights, geologic maps show that this natural community is underlain by Weverton Formation quartzite, a rock made primarily of quartz—which does not contain calcium, magnesium or other base elements. So how can the soil be fertile enough to support the Basic Oak - Hickory Forest?
Perhaps the Weverton quartzite on Maryland Heights contains thin layers of metamorphosed siltstone. . . or it may be that there are places the quartzite contains not just quartz but also calcium-rich feldspar.
