The South Mountain landscape of south-central Pennsylvania is home to a diverse array of natural and cultural resources—resources that have made the landscape unique and special for thousands of years.
Culturally, the South Mountain region has a rich human history: many visitors are aware of the region for the iron industry’s boom in the 18th and 19th centuries, and as a contested Civil War landscape. Fewer visitors, however, are aware of the great
antiquity of use by Native American populations, beginning with the Paleoindian period nearly 10,000 years ago, and extending up to European contact in the 1600's.
Physical remnants of many of these indigenous histories abound on the landscape today, and include archaeological sites such as hunting camps, stone tool debris, and stone quarries mined for the native rock metarhyolite, a sturdy material that
was very popular for stone tool manufacture for thousands of millennia. The material remnants of these histories continue to shape the landscape today, and a knowledge of these resources is critical to the region’s sense of place, as well as stewardship
of the ancient landscape.
In partnership with the South Mountain Partnership (SMP), this study is a collaborative research project comprised of a team of archaeologists, geologists, and cultural resource managers led
by the Indiana
University of Pennsylvania Department of Anthropology. The project’s focus is to better understand use of the prehistoric rock quarries located in the Michaux State Forest. Native Americans utilized geological outcrops of metarhyolite from South Mountain
throughout prehistory as a preferred raw material for making their stone tools such as projectile points, knives, and scraping tools.
The archaeological aspect of the project entailed ground-truthing and mapping these lithic procurement sites in a pilot area of the quarry complex. The geologic aspect entailed analysis of rhyolite samples using two state-of-the-art technologies, portable
X-ray Fluorescence (pXRF) spectrometry, and laser-induced breakdown spectroscopy (LIBS). These techniques allow for identification of unique chemical signatures, or “fingerprints,” for different outcrops, which can then be compared with archaeological
samples from Middle Atlantic archaeological in order to link distant sites to the South Mountain quarries and reconstruct prehistoric networks of travel and trade.
The importance of this project is threefold.
First, it has improved archaeologists’ understanding of prehistoric use of this important natural resource, allowing us to answer questions about prehistoric mobility, trade, and natural resource exploitation.
Second, it demonstrates the utility of newly emerging, non-destructive technologies such as LIBS and pXRF to answer archaeological questions.
Finally, it has informed best management practices of cultural resources within Michaux State Park, knowledge that will foster stewardship and education of the archaeological record of South Mountain.
The Precambrian-aged metarhyolite in South Mountain originated as lava flows associated with the rifting of continental crust to form the Iapetus, or “proto-Atlantic,” ocean approximately 540 million years ago. About 250 million years ago, this lava was
altered by heat and pressure associated with mountain building when the Iapetus closed again during the collision of North America and Africa. This pressure metamorphosed the rhyolite into metarhylite, a process that resulted in a strong, fine-grained,
and intergranular texture conducive to knapping into stone tools by prehistoric Native Americans. Tools made of metarhyolite vary widely in color and texture, as seen in the figure below.
During the Archaic and Woodland cultural periods, Native Americans quarried for high-quality rock in pits measuring approximately eight feet in depth and 20 feet in diameter. Materials recovered in and around these pits include unworked metarhyolite material
discarded due to its low quality; hammerstones used to shape the rhyolite into large bifaces that were transported to other sites for final production; flakes of high-quality material left over from biface production; and stone hoes used as digging
implements. Occasionally, the bifaces themselves are seen on the ground surface, presumably overlooked by their creators. The lack of domestic debris suggests that use of these locations was restricted to quarrying rather than used as habitation.
Today, the rhyolite quarry pits appear as subtle depressions that have been backfilled prehistorically by the excavation of adjacent pits and historically by erosion and vegetative debris. Although sometimes difficult to see, these depressions are visible
on the ground as well as in satellite imagery. Unfortunately, to date, very little research has been undertaken to investigate the spatial distribution of the quarries, how far the rhyolite was traded regionally, nor which outcrops of rhyolite were
used most often and preferred.
Lacking this knowledge creates difficulties for Forest staff tasked with balancing management of such a dispersed cultural resource with other mandated Forest activities such as timbering, conservation of native plant and animal habitat, and public recreation.
By better understanding Native American resource exploitation and trade within the Forest boundaries, we will be able to target the most sensitive areas for protection.
Flintknapping is the creation of flaked tools from stone core such as metarhyolite. This process requires knowing how to control the way stone will break. Certain types of rock such as chert, flint, and rhyolite are predictable in the ways that they will
fracture when struck by another material, such as stone, bone, or antler.
The fragment that breaks off is called a flake. Flakes are taken off the core during primary reduction in order to reduce the size of the original cobble for easier transport.
To take large flakes off the core, a hard hammer like a stone or moose billet is most useful. To remove flakes in a more controlled fashion and further shape the tool or when working with brittle material, a soft hammer, like an antler tine, can be used
to reach the desired shape in a process called
pressure flaking. To remove the finest flakes along the edge, the tip of an antler is used to apply pressure and remove small flakes. This process both straightens, sharpens, and reinforces the tool edge.
Flakes have several characteristics that distinguish them from naturally broken stones. Rock surfaces are carefully prepared by those who make stone tools. This results in a noticeable platform on the resulting flake, a somewhat flat surface left
over from where core preparation occurred. When a core is struck with a harder material, such as a granite hammerstone or moose billet, the force of the blow sends energy through the rock, creating a bulb of percussion, a cone-shaped bulge
adjacent to the platform. The force may also cause a tiny flake to pop off and leaving behind an errailure
scar. Finally, the energy may also produce compression rings to form—sort of like ripples produced by tossing a stone into a puddle of water.
The reduction process begins when a core is made smaller, or reduced, in the process of making a stone tool. Flintknappers use a rounded rock called a hammerstone or moose billet to strike flakes off one at a time. This is a very strategic and
complex process, and not nearly as easy as it sounds.
If you have never seen knapping in action, the Cleveland Museum of Natural History has an excellent video of archaeologist Mark Kollecker making it look easy—but don’t be fooled! Prehistoric knappers
probably spent years apprenticed to a master to learn this form of craftsmanship.
During the reduction process, the original stone core gets smaller as material is removed. Initially the flakes are very large and thick, and the weathered rind of the rock—called the cortex—covers most of the outer (i.e., dorsal) surface.
As the process continues, the flakes become smaller and smaller, with fewer of them having cortex as the weathered rind is removed. Eventually it is the right size, shape, and thickness to begin fine-tuning it into a final product. At this point,
the tool prototype—or biface—is more fragile and knappers must use a lighter tool, such as a deer antler tine, to carefully take off the smaller, thinner flakes.
Finally, the knapper shapes the tool using a technique called pressure flaking—that is, pressing the tip of the tine against the tool to create a strong, serrated edge capable of scraping deer hide, drilling through leather, or penetrating the
muscle of an animal.
Now imagine looking at the ground and seeing all those waste flakes. This, then, is what archaeologists often find themselves studying…the tools are long gone, but the debitage remains.
What has long puzzled archaeologists is why prehistoric populations went to so much work to dig pits into the ground to extract rhyolite, when it would have been easily collected from the surface. This project attempted to answer this question by looking
at thin slices of the rock under a microscope measuring about 30 microns, about the width of a human hair. These thin
sections, as they are called, showed that rhyolite from the ground surface tends to be very weathered, with some minerals weathering to fragile clays, and others wreathing to iron oxide, or rust. This creates weakness in the material and makes it
more difficult to knap predictably.
Rock from several feet below ground, however, does not show this same weathering affect. So, it seems that the extra work was worth it to obtain better materials.
This time-intensive process likely added value to the material as well. Just like today’s products that are time intensive and require craftsmanship, this may well have increased the rock’s value, and may help explain why it was traded so widely across
the Mid-Atlantic region.
One of the largest and most accessible outcrops of metarhyolite in the eastern United States comes from Adams County near Carbaugh Run. The quarries located here are listed on the National Register of Historic Places and are protected by the Michaux State
Forest. There are other sources of this same geologic formation following the Appalachian Mountain chain south into Maryland, Virginia, and North Carolina.
Rhyolite from South Mountain is believed to have been found at archaeological sites over 200 miles away from the source. This study sought to prove this hypothesis. Using high-tech geochemical instrumentation such as X-Ray Fluorescence (XRF) and Laser
Induced Breakdown Spectroscopy (LIBS), we were able to show that metarhyolite from Pennsylvania and Maryland sources have different chemical “fingerprints.” This is helpful to know because we can geochemically test artifacts from private and museum
collections and compare their chemical fingerprint to the known sources to see if the material was traded in from Pennsylvania or Maryland.
Unfortunately, the rhyolite proved too heterogeneous to source rock to specific quarries on South Mountain as we had originally hoped, but we can at least source artifacts to South Mountain versus more southern sources. Artifacts that shared the “Pennsylvania
fingerprint” come from as far west as Indiana County and north of State College.
Down the road, we hope to establish a citizen science program in which museums and collectors can loan artifacts for chemical testing.
The South Mountain Partnership mission is to be stewards of the natural and cultural resources. The partnership wants to protect and conserve these resources so that future generations may enjoy and appreciate them just as we are able to today. This includes
the metarhyolite quarries found within South Mountain, as they hold potential for furthering the archaeological understanding of the area and of cultural development and change through the trade of rhyolite among other materials.
Why do we want to protect these resources? Think of them like a book you’ve yet to read. Imagine that each looted artifact is a paragraph that’s been erased and that each hole dug by a looter erases pages. It may not seem like much when done once or twice,
but you lose details, and eventually nobody will be able to read that story. We want to protect these resources so that others will be able to read the story.
It’s difficult to protect these resources without the help of people like you, but these resources are not defenseless. To better protect these resources, and the stories that come along with them, there are laws in place that yield legal repercussions
for those who damage or loot archaeological sites.
The Archaeological Resources Protection Act (ARPA) makes if a federal crime to disturb subsurface deposits at archaeological sites; those prosecuted face both fines and jail time. In Pennsylvania, Title 37 or the Pennsylvania History Code classifies the
looting archaeological sites as a third-degree misdemeanor and could result in up to $2,500 in fines and up to a year in prison.
There are several ways that you can get involved with the South Mountain Landscape and South Mountain Partnership.
You can aid in the conservation of South Mountain resources by taking part in responsible outdoor ethics. Leave no trace of your visit: travel and camp on durable surfaces, and stay on existing trails and campsites; properly dispose of your waste; and
leave what you find.
If you see evidence of looting or disturbance, report it to the Michaux State Forest or local archaeologists. Members of our team that can help include archaeologists and geologists from Indiana University of Pennsylvania (Lara Homsey-Messer), Shippensburg University (Paul Marr and John Wah), and Juniata College (Jonathan
If you think that you have identified a new archaeological site not yet recorded, you can contact a member of our team, or you can record the site on a Pennsylvania State Site Survey form available at the Pennsylvania
and Historic Museum Commission’s website. For more information on recording sites, protecting our states cultural resources, and identifying prehistoric artifacts, visit the PHMC website.
If you want to get more involved with the South Mountain Partnership, their website offers a variety of ways to promote and conserve South Mountain resources and join in their community of collaboration. You could become a formal partner with South Mountain
Partnership or serve a committee on important issues and priorities in the region. Consider taking part in volunteer opportunities offered or sharing your stories of South Mountain by writing and submitting essays to their website.
Lastly, we want to emphasize that it’s fine to look and appreciate the skill of the artisans who made these tools, but leaving them where they are found is the best way to preserve this knowledge for scientists and—even more importantly—to respect the
descendant communities whose ancestors worked and lived on this beautiful landscape. In this way we can save the past for the future.