The Edinburg Formation is an Ordovician-age geological formation in Virginia. It is primarily composed of basinal (deep sea) limestone and

shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4) and tiny fragments (silt-sized particles) of other minerals, especial ...

, and is one of the younger units in the "Middle Ordovician" sequence of the

Shenandoah Valley The Shenandoah Valley () is a geographic valley and cultural region of western Virginia and the Eastern Panhandle of West Virginia. The valley is bounded to the east by the Blue Ridge Mountains, to the west by the eastern front of the Ridge- ...

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

facies In geology, a facies ( , ; same pronunciation and spelling in the plural) is a body of rock with specified characteristics, which can be any observable attribute of rocks (such as their overall appearance, composition, or condition of formatio ...

encompassed by the Edinburg Formation. The more abundant Liberty Hall facies consist of evenly bedded black limestone and shale. In a few areas, the Liberty Hall facies intertongue with the

Lantz Mill Lantz Mill, also known as Lantz Roller Mill, is a historic grist mill located at Lantz Mills, near the town of Edinburg in Shenandoah County, Virginia. It was rebuilt in 1865, after being destroyed by Union troops in 1864 during "The Burning", an A ...

facies. The Lantz Mill facies are grainy or cobbly wackestone which weathers to a buff brown color. Fossils are diverse, including graptolites, brachiopods, and trilobites.

References

Ordovician geology of Virginia {{Virginia-geologic-formation-stub