Browse Map

Explore away

Explore Map Collection

Check out our basemaps

Print a Map Plus

Generate a high-quality PDF

Field Guide

Discover local flora, fauna, geology, and more

Local Flora & Fauna

Learn the ecology of your area

Local Geology

Learn the geologic formation at your feet

Get Started or Sign In

Welcome

Continue with Apple

Already have an account? Sign In

MAP

Topo

Measure

Topo

Ecoregions

Public Lands

...

BASEMAPS

Default Weather

Temperature

Smoke

...

WEATHER

Oranda Formation

Geologic Formation in VA, WV

Print Map

Generate High-Quality PDF

Lithology

Shale

Sandstone

Siltstone

Other (961 mi²)

Geologic Age

Ordovician (487.3 Ma – 445.3 Ma ago)

Geologic Unit Label

Martinsburg Formation (Geiger and Keith, 1891). Three lithologic packages are recognized in the Martinsburg (in ascending order): black shale and limestone; sandstone and shale; and sandstone (Rader and Biggs, 1976). The lower unit consists of 200 to 250 feet of black calcareous shale, black aphanic, argillaceous limestone; and thin, light-brown K-bentonites. The bulk of the formation, more than 2800 feet, is composed of olive-green to gray, fine- to medium-grained, lithic sandstone and greenish-gray shale and siltstone. These lithologies occur in base-truncated Bouma cycles. Graded bedding, flute casts, and load casts are common. The upper unit, about 170 feet thick, is brownish-gray, medium- to coarse-grained, quartz sandstone. The lower two-thirds of this sandstone contains near-shore, marine fossils. Oranda Formation (Cooper and Cooper, 1946). Limestone and siltstone. Limestone, medium- to dark-gray, fine-grained, very argillaceous. Siltstone, black to dark-gray; both lithologies silicified where in contact with a K-bentonite. Five K-bentonites identified in the type section (Rader and Read, 1989).

— USGS

Taxonomy

Classified As

Geologic Formation