"Celebrating the Richness of Paleontology through Fossil Hunting"

fossilera logo
Guide to Fossil Hunting in the Mahantango Formation


Guide to Fossil Hunting in the Mahantango Formation

Devonian Mahantango

Guide To The Mahantango Formation: A Fossilized Devonian Coral Reef

Central PA, and West Virginia
Middle Devonian, ~387 Million Years Old

A large Dipleura trilobite found in the Mahantango Formation of Central PA.

View of Mahantango Fossil Brachiopods, freshly split from the siltstone.

A grammysioidea bivalve from the Mahantango

About The Devonian Mahantango Formation

The Mahantango is a very large middle Devonian formation that runs through many North Eastern states, including Pennsylvania, Marlyand, and West Virginia. It's the major middle Devonian formation in Pennsylvania and is part of the Hamilton Group.

Many oil experts know this formation because it sits directly on top of the Marcellus shale (which is now a household name). The Mahantango is sandwiched between the Marcellus shale on the bottom, and in many places, the Tully limestone on the top. In Western New York, the Mahantango of the Hamilton group is replaced by mainly the Moscow and Ludlowville shale. (Here is a link to the Western New York Fossil Page). The thickness of the Mahantango ranges from 1200 to 2200 feet and is comprised of shale, siltstones, and sandstones arranged in nested coarsening-upward cycles (Harper 1999).

It is an organic fossil bearing sequence of rock that was formed from the shallow Kaskaskia Sea which fluctuated in depth over time. The finer grained sediments come from shallow sea environments, while the coarser grained sediments indicate near shore environments, such as tidal areas, beaches, and deltas. Many of these near shore sediments contain deposits from violent storms. The slow transgression and regression of the sea levels caused these coarsening cycles that created the different subdivisions and layering in the formation. This is common in most marine and delta deposits, including the nearby Brush Creek Formation in Eastern PA.

Fossil sites from the Catskil Delta and Kaskaskia Sea include: Red Hill (Fossils Preserved in Freshwater lakes in the Castskill Delta), Lost River (Needmore Formation), Mahantango Type Locality (Hamilton Group), Western New York Sites (Hamilton Group), Sylvania, Ohio (Silica Formation), and the Clarita Oklahoma (Haragan Formation).

This is a rough map of the Eastern U.S. during the middle Devonian. It shows the shallow Kaskaskia Sea, the Catskill Delta, and the Acadian Mountains. As the Acadian Mountains eroded, sediments washed into the delta and out into the shallow sea.

The Mahantango was a typical tropical shallow sea environment. It contains a preserved middle Devonian reef system. Fossils of corals, brachiopods, cephalopods, and trilobites are commonly found. The fossil genera are very similar to the Hamilton group fossils of Western New York and the slightly older and very soft fossils from the Needmore formation of Pennsylvania, Virginia, and West Virginia.

This image shows a cross section of Devonian Strata from New York to Tennessee. Notice, in the North (New York), The Hamilton Group is on top of the Marcellus Shale, and is mainly composed of the Moscow and Ludlowville formations, in Pennsylvania (toward the middle) it is the Mahantango Formation, in West Virginia it is the Needmore Formation.

This image is from the USGS Scientific Investigations Report 2006-5198 by Boughton, Carol J., McCoy, Kurt J. (2006), and is Public Domaion in the U.S.

Harper, J. A., 1999, Chapter 7: Devonian, p. 108-127, in Shultz, C. H., ed., The Geology of Pennsylvania. Pennsylvania Geological Survey, 4th series, Special Publication 1, 888 p.

Fossil Collecting Locations in the Mahantango Formation:

The fossil rich shale and siltstone are very fissile and usually break into many pieces. As a result many of the fossils are very fragile and are often broken when found. Lots of care and glue are often needed when trying to extract intact fossils.

A roadside exposure of the fossil bearing Magantango formation.

Since the Mahantango formation is so expansive, there are numerous fossil collecting sites. Most are road cuts and roadside quarries spanning central Pennsylvania, the panhandle of West Virginia, North East Maryland, and Northern Virginia.

Jasper Burns lists eleven Mahantango collecting locations in his "Fossil Collecting in the Mid-Atlantic States" book alone... Many of which still exist. This book is also great because it has countless identification diagrams of fossils from the Mahantango and other nearby formations.

Here are 4 Mahantango Locations to get you started:

1. Pennsylvania - Danville:

The Montour Fossil Pit in Danville, PA. This is part of the PPL Montour Environmental Preserve. On the preserve is an old borrow pit that digs into the Mahantango formation. Fossil collecting is allowed at the Fossil Pit, there is even a big sign that says "Montour Fossil Pit". The preserve is open from sunrise to sunset - no pets allowed.

2. Pennsylvania - Swatara St. Park:

Swatara State Park, the east side of the park has a borrow pit called the "Suedberg Fossil Site." The pit exposes the Mahantango formation. You are allowed to fossil collect at the fossil pit.

3. West Virginia - Wardensville:

A few large road cuts on Route 55 starting around 2 miles east of Wardensville, West Virginia. The Gray shells contain fossils while the Black shales are relatively barren. Different layers will have different types and amounts of fossils.
There is one large pulloff at one of the roadcuts and a few areas with a very wide shoulder to park.

4. West Virginia - Delray:

Around 1.5 miles south of Delray in West Virginia. The rocks along the road and along the bank of the North River are from the Magantango formation. Different layers will have different types and amounts of fossils.

Sample of Fossils Found in the Mahantango Formation:

There are many different types of fossils found in the Magantango. This is just a sample of the more common fossils one can find. Click on any of the images below to go to the Magantango Fossil Identification Page.

Trilobite Fossils TRILOBITES

Brachiopod Fossils BRACHIOPODS

Bivalve Fossils BIVALVES

Coral Fossils CORAL

Gastropod Fossils GASTROPODS

Cephalopod Fossils CEPHALOPODS

Crinoid Fossils CRINOIDS

Recommended Books for Devonian Fossils:

101 American Fossil Sites You've Gotta See
By Albert B Dickas, 2018
This is a great updated fossil sites book with at least one fossil site in each state. Each site is broken into 2 pages. One has detailed information, such as directions, GPS coordinates, formation information, etc... The other is dedicated to images of the site and the fossils found there. It also gives information on fossil 'viewing' sites such as dinosaur trackways, museums, and active excavations.

This book is great for both beginning and expert fossil collectors. Beginners will find fossil hunting much easier with this book and experts will find it to be a great reference.
Plus, my fossil photos are peppered throughout this book!

Here is a link to my Review of the book.

Fossil Collecting in the Mid-Atlantic States: With Localities, Collecting Tips, and Illustrations of More than 450 Fossil Specimens
This book is a must for West Virginia! It's also a classic!
Out of the 45 fossil collecting sites, 22 are from West Virginia, and another 10 or so are just across the border! Although the book is getting old, many of the sites are roadcuts and are still accessable. Many of these sites are roadcuts that expose the Mahantango Formation.

What makes this book a classic is Jasper Burns incredible sketches of the locations and the fossils found at each location. It is a very descriptive and useful guide book. Even after all these years, I still find myself referencing it!

Fossil Collecting Locations in this book are from Virginia, West Virginia, Pennsylvania, Maryland, and Delaware.

Trilobites: Common Trilobites of North America (A NatureGuide Book)
by Jasper Burns, 2000

I love Jasper Burns. His Fossil Collecting in the Mid-Atlantic book is still one of my favorite fossil books. His drawings are spectacular and the books are well laid out. This book serves as a field guide and identification guide to North American trilobites. If you fossil hunt for trilobites in North America, you should have this book!

Trilobite Fossils:

Trilobite fossils are some of the most beautiful and collectible fossils in the world! There are countless species and countless colors of trilobites. They make beautiful display pieces and conversation pieces. Common ones make very affordable for gifts to fossil and paleontology enthusiasts. Fossil Era has a huge selection of top quality trilobites from many states and many countries. It's fun just to browse through the inventory and look at all the different types!

About the Author

Contact Us

To ask Questions about Paleontology, Fossil Identification, Image Use, or anything else, email us. is very active on Facebook, you can also message us there!

We don't buy or sell fossils, so please don't email us asking about the value of a fossil or fossil purchases.

Visit us on Social Media:

Enjoy this website?
Consider a Paypal / Credit Card donation of any size to help with site maintenance and web hosting fees:

Privacy Policy and Legal Disclaimer

Back to the TOP of page

© 2000 - 2022 : All rights reserved


fossilguy logo is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to