It is primarily composed of basinal (deep sea) limestone and shale, and is one of the younger units in the "Middle Ordovician" sequence of the Shenandoah Valley.

However, fossils have shown that it actually was deposited in the early part of the Late Ordovician.

The more abundant Liberty Hall facies consist of evenly bedded black limestone and shale.

The Lantz Mill facies are grainy or cobbly wackestone which weathers to a buff brown color.

[2][3] This article about a specific stratigraphic formation in Virginia is a stub.