Rehousing a vessel with salt damage

Contributed by John Bergman-McCool

In January, the HVAC system in one of our collection storage areas malfunctioned. Repair work required that the system was turned off for several days. During this time, we monitored the objects for any changes. One vessel caught our eye.

Thanks to Marla’s experience with the collection, she noticed that previously documented spalling due to salt efflorescence was likely developing further (see figure). A quick look at older photographs confirmed that the damage had indeed progressed. The vessel was stored on open shelving and an inspection of the area around the object determined that no fragments had fallen completely off. We decided to rehouse the vessel in a box to buffer it against changes in environment during the current or future failure of the HVAC system.

Figure 1. Rehoused vessel in open box

Since I’ve encountered salt efflorescence a few times, I thought I’d add a bit more information. Porous materials, like bone, ceramic and stone, can absorb salt from various sources. Once inside, salts can be dissolved by moisture in the air through a process called deliquescence. Eventually, the water evaporates and the salt recrystallizes. In very porous objects, the salt crystals form on the surface. In objects where the surface is less porous than the underlying body, recrystallized salt can generate massive forces than can spall or pit the surface (Source: NPS Conserv O Gram 06/05 page 1). In worst case scenarios objects can disintegrate.

As I mentioned in an earlier blog, salts can enter porous objects through groundwater or seawater in buried or submerged contexts (Source: NPS Conserv O Gram 06/05 page 1). They are a major source of salt in archaeological collections such as ours. In the case of ceramics, food and water stored in objects during their pre-burial use life can also leave salt residues (Source: Minnesota Historical Society Page 2). Salts can be introduced to ceramics during manufacture through additives that modify the clay body and through water (Source: Minnesota Historical Society Page 2, Source: Digital Fire). Even clay itself can be salty. When I lived in Arizona, I can remember hearing a potter discuss that they would check their clay by tasting it to make sure it wasn’t too salty.

After ceramic objects are recovered during excavation, salts can continue to be added in archaeological labs and museums. Hydrochloric acid has been used to remove calcium carbonate, an insoluble salt that adheres to ceramics during burial that impedes analysis. An unintended result of this process creates calcium chloride, a soluble salt, which is absorbed into the ceramic matrix (Source: The International Institute for Conservation of Historic and Artistic Works- Studies in Conservation Page 172, Source: NPS Conserv O Gram 06/05 Page 2). I would be highly doubtful of repairs that were done years ago. Without detailed treatment records, who knows what glues were used and what contaminants they might introduce.

Figure 2. Spalling due to efflorescence

Deliquescence and evaporation of soluble salts can be greatly diminished by keeping the storage environment below 60% relative humidity and by reducing humidity and temperature fluctuations (Source: NPS Conserv O Gram 05/06 Page 3). However, there is a continued danger of efflorescence. Display cases and storage shelving made from wood have the potential to release acetic acids. This volatile organic compound has the potential to interact with soluble salts leading to precipitation even in controlled storage environments (Source: ICOM Committee for Conservation Page 640).

There may not be quick or inexpensive solutions to mitigate efflorescence. Our current plans for renovation of Peabody collections spaces call for the replacement of wood drawers and cabinets, but this is expensive. In regards to removing salt from objects, the traditional method is through a desalination wash or soak, wherein the object is immersed in distilled or deionized water until the salt level is reduced. This is a complicated process and shouldn’t be done without involving a conservator. Desalination risks removing important residues and compounds that can reduce the usefulness of the objects for future analysis and weaken the object (Source: NPS Conserv O Gram 05/06 Page 3).

Here at the Peabody we’ve taken steps to remove salt through dry brushing, environmental controls, and monitoring. In the future, we have plans to improve our storage space so that these issues will no longer be a concern.

C14 Dating the Collection

Contributed by Marla Taylor

You have probably heard of radio-carbon (C14) dating.  An invaluable tool for contextualizing the past, C14 dating is a method for determining the age of an object containing organic material by measuring stable and unstable (radioactive) isotopes of Carbon.  Developed by University of Chicago physical chemist Willard Libby in the 1940s, C14 dating was a game-changer for the field of archaeology. Libby received the Nobel Prize in Chemistry in 1960.

Instead of relying solely on relative dating – the basic concept that an object found below another is older than one found closer to the surface – archaeologists gained the ability to specifically identify a year range for organic artifacts.  The Peabody Institute was a contributor to this work through past curator, Frederick Johnson, but that is a story for another blog.

This profile is an example of relative dating – more recent objects are closer to the surface while older material is deeper.

Lately, I have been working to facilitate C14 dating on bone artifacts from Pikimachay Cave in the Ayacucho Valley of Peru at the request of the 2019 Cordell Fellow, Juan Yataco.  Juan is revisiting work done in the Ayacucho Valley by Scotty MacNeish.  Back in the 1970s, MacNeish made some pretty bold assertions about the dates of human occupation in that region.  At the time, the C14 dates from animal bones supported his claims, but other archaeologists doubted whether those bones were associated with human occupation. 

While Juan’s specialty is stone tools, he also wanted to use improved technology to obtain an updated date for Pikimachay Cave.  Unfortunately, the first bone sent for testing failed to yield an appropriate collagen sample and could not be tested.  A second bone is on its way now.  Both bones were modified by humans and will provide a fascinating glimpse of the past.  Fingers are crossed for a better outcome this time around!

FBI Collection – Origin and Update

Contributed by Marla Taylor and John Bergman-McCool

Every museum is full of stories and story-tellers.  Our recent work in the inventory process has uncovered an old story that always gets my attention (Marla’s).  But, before I begin, I must give credit to Eugene Winter, the Peabody’s late Curator Emeritus, who was a story-teller extraordinaire – I am sharing a shortened version of his memories.  (Another time, I will tell you about the time Gene cooked his lunch in an active volcano or walked on a whale.  The man was full of stories!)

Gene Winter – the best story-teller I knew

In 1986, Gene welcomed a man named George McLaughlin into the Peabody.  McLaughlin claimed to be creating a handbook on archaeology for the local Boy Scouts and was looking to photograph objects in the Peabody’s collection.  As a teacher himself, Gene was happy to encourage this project and made arrangements for McLaughlin to return a couple weeks later to access the collection.

However, McLaughlin instead returned the next day and told the administrative assistant, Betty Steinert, that Gene had authorized him to examine the collection – alone.  Over the next three days, McLaughlin helped himself to an unknown number of objects from the collection.

Less than a week later, Gene received a call from security at Yale’s Peabody Museum of Natural History.  A man matching McLaughlin’s description had stolen artifacts from a grad student’s work area and ran out of the museum before he could be caught.  Because McLaughlin had now crossed state lines, the FBI became involved. 

Gene and Betty remembered that McLaughlin had used the Peabody’s phone to call his wife about being late for dinner.  This crucial piece of information allowed the FBI to locate McLaughlin’s home. Fortunately, McLaughlin was arrested soon after these incidents and all materials in his possession were seized. 

Eagle-Tribune article from 1986 recounts George McLaughlin’s theft of artifacts from the Peabody Museum.

In total, McLaughlin victimized six institutions in New England and stole thousands of artifacts valued at over $800,000 in 1986 ($1.9 million in 2020 dollars).  He intermingled the artifacts based on his own system and systematically removed their catalog numbers (often the best clue to their original home).  By so drastically removing the objects from their context, it was a challenge to return the objects to their appropriate homes.

McLaughlin had kept his own version of a ledger identifying the objects and where they came from.  And fortunately, Gene was able to recognize a dozen or so very specific objects from the Peabody’s collection.  The FBI left it up to the victimized institutions to divide the material in McLaughlin’s collection.  The Peabody ended up with nearly 1600 objects from McLaughlin. 

Ultimately, McLaughlin was sentenced to a three year suspended sentence and four years of probation.  He was also fined $10,000 and ordered to pay a small restitution to each institution.

And therein lays the origin of the Peabody’s FBI collection.

Having come across these materials during our inventory and rehousing project it was time for them to be cataloged by myself (John). One challenge confronted us: McLaughlin had removed any identifying numbers applied by the museums and applied stickers with his own numbers. As the objects were cataloged, a careful inspection was made for remnants of original numbers not completely obliterated during the removal process. There were many with tantalizing hints of legible numbers. In the end though, there were just a few objects with numbers clear enough to associate with our museum’s ledger.

A page of McLaughlin’s inventory

The remaining majority of objects needed new numbers. As mentioned above, McLaughlin had organized the objects and transcribed them into a ledger of sorts. His ledger was too general to make a one-to-one comparison with our own museum’s ledger, but it served as the outline of our numbering system. We added our own prefix, indicating that these objects were stolen and returned by the FBI and followed that with the McLaughlin number. In that way the objects will always carry that part of their strange history.

I (Marla again) do want to note that to our knowledge, McLaughlin is not responsible for the missing artifacts from Etowah and Little Egypt discussed in our blog in 2019.

The ‘Horned Giants’ of Pennsylvania

Contributed by Emily Hurley

One day while I was working in the basement of the Peabody, plugging away at inventorying drawers, I was listening to a podcast called Astonishing Legends. It was an episode titled “The Tall Ones” exploring the legends and lore surrounding giants around the world. It came as a surprise when I heard the hosts say the name W.K. Moorehead! My ears instantly pricked up.

The podcast hosts went on to cite a New York Times article written on July 14, 1916 under the headline “Find Horned Men’s Skulls: Remarkable Discovery by Archaeologists in the Susquehanna Valley”. The short article stated that Professor A.B. Skinner of the American Indian Museum, Rev. George Donehoo, Pennsylvania State Historian, and Professor W.K. Moorehead of the Phillips Andover Academy uncovered a burial mound at the Murray Farm site while conducting research at Tioga Point in the Susquehanna Valley. In the mound, they uncovered the remains of sixty-eight men, believed to have been buried around the year 1200 AD. According to the article, the average height of these men was seven feet, with many being even taller. Also found with the remains were very large stone celts and axes, further evidence of the men’s gigantic size. Perhaps most interesting of all, some of the skulls had two inch bone protuberances on their foreheads. Well, this was something to explore!

Workers at the Murray Farm excavation. Photograph taken by Rev. George Donehoo, 1916.

Looking through historical texts and documents, it is clear that giants have been a topic of interest for centuries. Not only are they mentioned in the Biblical story of David and Goliath, but in fairy tales such as Jack and the Beanstalk, and the legend of Paul Bunyan. One pervasive theory about giants is that they are actually Nephilim (also from the Bible), the offspring of an angel and a human. Even some historical figures such as Gilgamesh are thought by some to have been giants.

Many newspaper articles from across the country in the nineteenth and early twentieth centuries claim to have found giant skeletons. Some accounts even call them a lost race of giant people, but many others hypothesize that they were giant Native Americans. An eight foot tall Native American skeleton was said to be found in Towanda, Pennsylvania in 1822. A headline from The World newspaper on October 6, 1895, read “Biggest Giant Ever Known-Nine Feet High and Probably a Prehistoric California Indian.” Some, like the Cardiff Giant, which was actually a buried stone statue, were proven to be hoaxes. Yet the stories still remain popular. Even Captain John Smith, in his account of meeting the Susquehanncocks in 1608, described them as giant-like. But were there really giants roaming this land before us? Or horned giants for that matter?

After some further digging, it was discovered that the “horned giants” found by Moorehead and others at Murray Farm were not horned at all, nor were they giants. Professor Skinner wrote a corrected article for the New York Times but it was not as publicized as the original, so it is harder to find. Apparently while excavating the site, a workman shouted out “There are horns over his head!”, after discovering a bundle burial which had been covered with deer antlers. An excited visitor or reporter at the site heard this and asked another workman, who decided to play a joke and claim that the skeletons had horns growing out of their heads. Another version says that a disgruntled camp cook made up the story.

Workers at the Murray Farm excavation, along with visitors who came to see the exciting finds. Photograph by Rev. George Donehoo, 1916.

This explains the story about the horns, but what about the supposed enormous height of these individuals and the other accounts of giants found nearby? It is thought that these skeletons, as well as accounts of living “giant” Susquehannocks, were not giant at all, but just taller than average. At the time, the average height of most Europeans was about five feet six inches tall, whereas Native Americans were thought to average about six feet tall. While six inches is not that big of a difference, anyone taller than six feet may seem like a giant to the generally shorter Europeans.

Another reason for the discovery of “giant” skeletons is that these bones were often misidentified as human when they actually belonged to extinct animal species. It may seem far-fetched that anyone could misidentify a mammoth bone as that of a human, but other than the skull, human bones actually look very much like animal bones. So to someone not trained in osteology, a very large rib bone may seem like it is from a human skeleton. Many skeletal remains have been innocently misidentified this way, not only as giants, but as monsters or “Titans” as well.

Over time it seems that this giant narrative of Native Americans by Europeans was exaggerated and, coupled with misidentified animal bones, resulted in the discovery of “giant skeletons.” However, these so-called giant skeletons always seem to mysteriously disappear after being excavated, leading many to believe that they either never existed, were misidentified animal bones, or it was actually just a taller than average person.

After hearing the podcast, I did some digging of my own through Moorehead’s records, just in case I could find anything related to the “horned giants”. I found many documents related to the Susquehanna Valley expedition as well as correspondences between Moorehead, Skinner, and Donehoo. None of these documents ever mentioned the “horned giants” or the article written in the New York Times. I did find a picture of Professor Skinner holding a perfectly normal looking skull with no protuberances while at Murray Farm. Moorehead also wrote a short report of the excavation, and again, no mention of giants was found.

Warren K. Moorehead (far right) and others in the Susquehanna Valley. Photograph taken by George Donehoo, 1916.

Even though the horned giants of Pennsylvania turned out to be nothing more than a tall tale (pun intended), it was fun to hear a story about Moorehead on one of my new favorite podcasts! I wonder what interesting stories I’ll uncover next!

P.S. For further reading on giants and other archaeological myths, check out Kenneth Feder’s book titled Frauds, Myths, and Mysteries!

COVID-19 and Social Distancing: What Museums Are Doing to Bring Their Collections to Audiences Stuck at Home

Contributed by Emma Lavoie

The Centers for Disease Control and Prevention (CDC) issued guidelines to limit the spread of COVID-19, also known as the coronavirus. One recommendation included in these guidelines was for “social distancing” – a term referring to the conscious effort to reduce close contact between people and hopefully hinder the community transmission of the virus.

While schools, companies, and various workplaces determine the best possible options to both adhere to these guidelines as well as provide the appropriate support to their staff, students, and customers – many have chosen to close their doors. Some institutions and companies have shut down indefinitely, while various schools and universities have moved to remote teaching, where students complete their classes online and stay at home. Universities and colleges all over the country have moved courses to online platforms. Undergrads are being told to move out of their dorms and off campus for the remainder of the semester.

Phillips Academy (PA), a New England boarding school and the Peabody’s parent institution has instituted similar measures, following the directives issued by Massachusetts Governor Charlie Baker.

A local restaurant closes their doors in light of “on-site eating” bans over COVID-19

Now many would say they like working from home and actually get more done, but it is not the case for everyone. The Peabody staff are doing what they can to continue their museum work from home. For the Peabody collections team, it is very difficult to continue much of the work they do every day at the institution, as much of the collections and material cannot leave the building. While inventory, rehousing, and cataloguing of the collection is put on hold, our staff is editing object photographs, digitizing documents, transcribing collection ledgers, writing blogs (like this one), and more.

My dog, Rourke, is very happy to have me working from home!

Outside of my remote-work, I am wondering like many others who are stuck at home – what else can I do with the rest of my week? By being at home, we miss out on the daily interactions with our coworkers, colleagues, and classmates. Our experiences with each other fuel our creativity and critical thinking, and are important for much needed collaborative efforts. Through “social distancing” we are recommended to not take part in every day, public activities such as eating out, going to the store, or visiting a museum or historical site with our friends and family.

But don’t let social distancing doom your week and weekend! Museums have found a way to bring some of their collections to their visitors. So worry no more! You can view that Van Gough from the couch!

I was happy to enjoy a little culture and education in my off-time while at home. According to Fast Company, Google Arts & Culture has teamed up with over 500 museums and galleries around the world to bring virtual tours and online exhibits to a global audience.

Some of the museums highlighted by Google Arts & Culture include the British Museum in London, the National Gallery of Art in Washington, D.C., the Musée d’Orsay in Paris, France, the National Museum of Anthropology in Mexico City, Mexico, and various historical parks and sites.

Design of the Musée d’Orsay in 1979
Image courtesy of A.C.T. Architecture and the Musée d’Orsay

The first museum I “visited” was the Musée d’Orsay in Paris, France. As a student, I had visited this museum on a class trip many years ago and I was interested in the exhibits they provided online. This exhibit was a detailed history on the building of the museum titled, From Station to the Renovated Musée d’Orsay. This endeavor was a groundbreaking project for Paris as it was the first time an industrial building had been restored to accommodate a major museum. The virtual exhibit showcases the early building plans and images of the Orsay train station and hotel from the 1900s as well as images of the museum and its galleries after the renovation project in the early 2000s. Explore this virtual exhibit here!

I visited a second virtual exhibition, this time, at the National Gallery of Art in Washington, D.C. The exhibition is called, Fashioning a Nation. This exhibit features drawings from the Index of American Design, a collection of more than 18,000 watercolor pictures of American decorative art objects. This exhibition explores the American fashions from 1740 to 1895, giving insight into the character and quality of American life from the colonial period to the Industrial Revolution. Click here to explore this exhibit!

3D model of the Balcony House at Mesa Verde National Park
Image courtesy of CyArk and Open Heritage – Google Arts & Culture

If museums aren’t your thing, explore a historic site! Open Heritage – Google Arts & Culture offers iconic locations in 3D, using 3D modeling techniques for you to explore. You can learn about the tools of digital preservation and how people all over the world are preserving our shared history. One site I visited was the Mesa Verde National Park. This site is home to Native American cliff dwellings in southern Colorado that span over 700 years of Native American history (600-1300 CE). An expedition was led by CyArk in February 2017. CyArk is a nonprofit organization that specializes in the digital documentation and preservation of historic sites. The organization documented the Balcony House at Mesa Verde using Light Detection and Ranging (LIDAR) and terrestrial photogrammetry. Combining these two technologies is what creates the 3D model of a site. To explore the 3D model of the Balcony House at Mesa Verde, click here!

Unfortunately, not all popular museums and galleries are included on Google Arts & Culture’s collection website, but some museums are offering virtual tours and online visits on their own websites, such as the Louvre in Paris, France. To see more of Google Arts & Culture’s collection of virtual museums and exhibits, visit their collection website. Explore and enjoy your visit!

Wild Ride No More

Contributed by John Bergman-McCool

Cups and Coaster
The collections environment before and after rehousing in archival boxes

Back in March I wrote a blog post summarizing efforts to rid collections objects of mold and salt uncovered during inventory and rehousing. We identified and isolated affected objects and cleaned them by dry brushing and vacuuming. The cleaned objects were rehoused in archival boxes that included a sachet of silica gel. The purpose of the gel is to reduce relative humidity (RH), thereby robbing mold and salt of the environmental conditions necessary for their growth. To better understand what the environment is like inside the boxes, we are monitoring their temperature and relative humidity with two data loggers. One is placed inside a box without silica gel and one is placed inside a box with silica gel. These conditions will be compared against a data logger that is recording general conditions in the basement not far from where these test boxes are located. We will be watching these data loggers over the coming year, but we already have some interesting results.

Temp and RH graph for John August 2019
Environmental Stats for April

First, the boxes are working well as a buffer against relative humidity cycles. The graph above shows RH and temperature for the month of April; the basement is shown in red and the boxes with and without silica are blue and yellow, respectively. In April the RH in the basement was quite volatile. However, the RH inside the boxes is remarkably tranquil in comparison. The boxes are exhibiting small daily shifts of 1 or 2%, which is acceptable. Keeping RH from shifting dramatically is an important factor in collections care. Organic materials such as basketry, bone, and wood are hygroscopic, meaning that they can absorb and release moisture in the air. Rapid and large changes in RH can cause organic materials to swell and contract leading to damage such as cracking or delamination. It is best to keep collections from experiencing RH shifts exceeding 10% over a given month and on that count the boxes are doing a great job. As they are found, the most sensitive organic collections are being moved to another part of the museum that has a better environment.

Layerd Storage
Layered Storage

The National Park Service recommends creating a layered approach to collections storage. Every enclosure within museum storage can act as an environmental buffer. The first enclosure is the building itself. It may seem pretty obvious, but keeping collections inside a building greatly reduces the effects of environmental factors. The same is true of every subsequent layer of enclosed storage. Here at the Peabody Institute we have wooden storage bays that, when closed, serve as another layer. The archival boxes act as a final layer.

 

Interestingly, the basement seems to be effective at buffering daily temperature cycles. The temperature in the basement has been hovering around 70 between February and June leaving little for the boxes to mediate.

Sachet
Silica Gel Sachets

The second finding of note is that the sachets of silica gel were spent faster than anticipated. As mentioned above sachets of silica gel were placed in the boxes with cleaned objects. The gel, in solid pebble-like form, starts out orange and as it absorbs water it changes to a deep blue. The expectation was that the gel would keep the RH at a reduced and steady level. The graph above shows that the silica gel was keeping relative humidity lower than that of the box without gel, but it is only a matter of a few percentage points. Most likely the boxes are not well enough sealed for the silica gel to more significantly moderate RH levels. The silica was active from mid-February until mid-April (see star on graph) when RH graphs inside both boxes started to match almost perfectly. A visual inspection in June indicated that the gel was spent. We replaced the silica in mid-June and it was spent within two weeks given the higher RH levels generally in the basement.

 

Our data shows that the boxes are acting as a significant buffer against potentially damaging cycles of increasing and decreasing RH levels. For now, we are forgoing replacing spent silica gel. Later in the fall we’ll see how the archival boxes work with our dehumidifiers at keeping mold and salt inducing RH at bay.

Northeastern Archaeological Survey re-examined

Hello! We are Arthur Anderson and Gabe Hrynick, faculty at the University of New England and University of New Brunswick, respectively. Much of our fieldwork together is in far Down East, Maine on Cobscook Bay in Washington County. We’ve been lucky enough to make a few visits to the Peabody over the last few years to get an understanding of the collections housed there from this area. Now we’re excited to be back for an extended visit to explore these collections further! The Peabody’s collections are particularly important to our research because in many cases they may be all that’s left of sites that have eroded due to rising sea levels and increased storm magnitude.

The Peabody collections from Cobscook Bay are almost all the product of the Northeastern Archaeological Survey from the late 1940s to the middle 1950s. The project was initially led by Robert Dyson, future director of the Penn Museum, but effectively taken over by Theodore Stoddard, the most consistent member of the crew over those years. In addition to NAS members from the Peabody, Stoddard worked closely with avocational archaeologists in the area. The most prominent of these was Isaac W. Kingsbury, a Hartford internist who summered in Perry, Maine and seems to have been a local point of contact for the survey crew, and even occasionally published his findings in the Bulletin of the Massachusetts Archaeological Society. One of the most interesting aspects of our research in the Peabody Collections has been reconstructing the work undertaken during those years largely from charming and expansive correspondence between Kingsbury and Stoddard to better understand the context of their records and collections. It’s also a lot of fun to read their accounts of the joys and challenges of working in an area that we love. We can commiserate with their complaints of construction on US Route 1 almost every summer and the barrage of mosquitoes and black flies. We certainly identify with ‘day book’ entries recounting their discussions of the latest archaeological publications on the long drive there. Unfortunately, Frank’s Restaurant in Freeport is long gone, so we can’t comment on their lunch recommendations.

In addition to better understanding the NAS collections, we’ve been looking for some very specific artifacts within it. Our current project, funded by the Social Science and Humanities Research Council of Canada, focuses on the very earliest period of European interaction with Maine and the Maritime Provinces. This is often referred to as the Protohistoric period. By examining old collections for things like glass trade beads, early iron axes and fragments of copper kettle that we have much more context for and information about than they did in the middle of the 20th century, we hope that we can better understand the period and potentially re-locate sites we know to have Protohistoric components thanks to the Peabody collections.

Northeastern Archaeological Survey
Why not write the entire provenience on every object?

Sharing our collection – Indian Basketry in Yosemite Valley

Contributed by Marla Taylor

In September 2018, Catherine Hunter, Research Associate, presented a paper to the 2018 Symposium of the Textile Society of America (TSA).  The symposium was an opportunity to publish a portion of the Native American basketry collection at the Peabody Institute.  Held in Vancouver, BC, the symposium was a dynamic event with over 400 participants and Catherine was one of 120 individuals presenting their research.

Catherine’s paper, Indian Basketry in Yosemite Valley, 19th-20th Century: Gertrude ‘Cosie’ Hutchings Mills, Tourists and the National Park Service, is now available via Digital Commons at the University of Nebraska.

For more about the basketry in the Peabody’s collection, take a look back at Catherine’s past contributions to our blog: The Language of Baskets, The Language of Weaving, California Basketry Exploration

Half-Life: Radiocarbon Dating Tehuacán Carbon Samples

Contributed by Emma Cook

In my last blog I discussed soil analysis and its importance in dating and understanding a site. Another form of analysis used in the Tehuacán Archaeological-Botanical Project by Richard “Scotty” MacNeish was a process called radiocarbon dating, a technique developed by University of Chicago physicist Willard Libby. Carbon samples were collected during excavation and sent for carbon dating to be used for the Tehuacán Chronology Project.

There are two techniques for dating in archaeological sites: relative and absolute dating. Relative dating, in a stratigraphic context, is the idea that objects closer to the surface are more recent in time relative to objects found deeper in the ground. This relates to the law of superposition, which in its plainest form, states soil layers in undisturbed sequences will have the oldest materials at the bottom of the sequence and the newest material closer to the surface. Although this form of dating can work well in certain cases, it does not work for all.

Jars of Carbon Samples from various sites in the Tehuacán Valley.
Jars of Carbon Samples from various sites in the Tehuacán Valley.

Many sites include soil layers that have been disturbed and this can happen several ways. Natural disasters, such as floods, can erase top layers of sites. Rodents can move around layers in a site as they burrow underground, sometimes moving items from one context to another. Even current human activity can change the stratigraphy of a site through construction, post holes, and pits.

This takes us to our second dating technique. Absolute dating represents the absolute age of a sample before the present. Examples of objects that can be used to find absolute dates are historical documents and calendars. However, when working in an archaeological site without documents, it is hard to determine an absolute date. If a site has organic material present, radiocarbon dating can be used to determine an absolute date. Radiocarbon dating is a universal dating technique that is used around the world and can be used to date materials ranging from about 400 to 50,000 years old. Radiocarbon dating may even work on very recent materials.

Part of this carbon sample sent to Isotopes lab for radiocarbon dating.
Part of this carbon sample sent to Isotopes lab for radiocarbon dating.

Organisms such as plants and animals all contain radiocarbon (14C). When these organisms die, they stop exchanging carbon with the environment. When this occurs, they begin to lose amounts of 14C overtime through a process called radioactive decay. The half-life of 14C is about 5,730 years. Radiocarbon dating measures the amount of stable and unstable carbon in a sample to determine its absolute date. As a result, the older the organic material, the less 14C it has relative to stable versions of the isotope.

The carbon samples recovered from the Tehuacán Valley were collected specifically with this in mind. Many of these samples had labels or notes stating that some of each sample was sent to labs for radiocarbon testing. The carbon samples are organic material and their properties of radiocarbon were used to determine the age of the material, which in turn, helped date each site.

Map of the Tehuacán Valley and some of the sites the carbon samples came from.
Map of the Tehuacán Valley and some of the sites the carbon samples came from.

The following sites are represented in some of the jars of carbon samples I catalogued from the Tehuacán Archaeological-Botanical Project.

Site Number                        Site Name                     Radiocarbon years

Tc 35                                         El Riego                                 6800 to 5000 B.C.

Tc 50                                         Coxcatlan Cave                  5000 to 3400 B.C.

Tc 307                                      Abejas                                     3400 to 2300 B.C.

Tc 272                                      Purron Cave                          2300 to 1500 B.C.

Ts 204                                     Ajalpan                                     1500 to 800 B.C.

These results were published in Volume Four of MacNeish’s Prehistory of the Tehuacan Valley: Chronology and Irrigation and can be found on Page 5. MacNeish and Tehuacán Chronology Project director, Frederick Johnson, selected carbon samples to be sent for testing, which resulted in the determination of 218 radiocarbon dates. Johnson played a prominent role in radiocarbon dating, serving as the chair of the Committee on Radioactive Carbon 14 set up by the American Anthropological Association. This project not only produced a chronology for the Tehuacán sequence of excavated sites, but later contributed (along with 400 additional radiocarbon dates) to the chronology for all of Mesoamerica. The dates, however, were made within the first two decades of radiocarbon dating and lack the accuracy and precision now available with newer techniques, especially with the older dates.

To read more about the Tehuacán Archaeological-Botanical Project and the Tehuacán Chronology Project visit Internet Archive.

Further Reading

Libby, Willard F. Radiocarbon Dating, 2nd ed., University of Chicago Press, Chicago, IL, 1955. Print.

MacNeish, Richard S. et al., The Prehistory of the Tehuacan Valley: Chronology and Irrigation. Vol. 4. University of Texas Press, Austin, TX, 1972. Print.

Stromberg, Joseph. “A New Leap Forward for Radiocarbon Dating.” Smithsonian.com, October 18, 2012. Web. https://www.smithsonianmag.com/science-nature/a-new-leap-forward-for-radiocarbon-dating-81047335/

Taylor, R.E. and Ofer Bar-Yosef. Radiocarbon Dating: An Archaeological Perspective. 2nd ed., Routledge, New York, NY, 2016. Print.

Iconography and Wetsite Archaeology of Florida’s Watery Realms

In April the University Press of Florida published Iconography and Wetsite Archaeology of Florida’s Watery Realms, my new book, co-edited with Oxford’s Joanna Ostapkowicz. Watery Realms highlights current research on sites and artifacts preserved in anaerobic environments throughout Florida. This blog reproduces some of the book’s first chapter, which recounts the origins of the volume and some of the exciting research presented.

Image of presenters at the 2016 Society for American Archaeology symposium The Archaeology, Art, and Iconography of Florida’s Watery Landscapes with Barbara A. Purdy. From left: Joanna Ostapkowicz, Dan Seinfeld, Bill Marquardt, Michael Faught, Julia Duggins, Karen Jo Walker, Phyllis Kolianos, Steven Koski, Barbara Purdy, Jim Knight, and Ryan Wheeler.
Presenters at the 2016 Society for American Archaeology symposium The Archaeology, Art, and Iconography of Florida’s Watery Landscapes with Barbara A. Purdy. From left: Joanna Ostapkowicz, Dan Seinfeld, Bill Marquardt, Michael Faught, Julia Duggins, Karen Jo Walker, Phyllis Kolianos, Steven Koski, Barbara Purdy, Jim Knight, and Ryan Wheeler.

The book grew out of the symposium The Archaeology, Art, and Iconography of Florida’s Watery Landscapes that we organized at the 81st annual meeting of the Society for American Archaeology (SAA) in Orlando, Florida, not terribly far from some of the amazing sites being discussed. By coincidence, the icon of the 2016 SAA meeting was the Hontoon/Thursby owl, which was the focus of our conference presentation and recent study. This made the venue doubly relevant in highlighting the importance of Florida wetland archaeology. As the session grew into the Watery Realms book, it expanded to include other contributors and has inspired new collaborations. A generous grant from the Toomey Foundation for the Natural Sciences helped underwrite the symposium and ensure that presenters from graduate programs, government agencies, cultural resource management firms, universities, and museums were able to attend. William Marquardt, a co-presenter on the wetsite resources of the Pineland site with Karen Jo Walker, volunteered to write a chapter for the book on the interesting corpus of wooden anthropomorphic figurines from southern Florida. Rick Schulting, who was involved in the strontium isotope analysis of the Hontoon/Thursby carvings in our study, linked with Julia Duggins over ways to test her ideas about Florida canoes and watersheds, a project that secured a Wenner-Gren Foundation grant. Plans for future collaborations on the anthropomorphic figurines and Key Marco material are also under way. Our discussants Jim Knight and Lee Newsom pointed out many of the ways the presenters could connect their work and explore Florida’s wetsite art.

Archaeologists Christine Newman and Ray McGee excavating the Lake Pithlachocco canoe site, 2000.
Archaeologists Christine Newman and Ray McGee excavating the Lake Pithlachocco canoe site, 2000. Dugout canoes like these figure prominently in the Watery Realms book.

The idea for the symposium emerged through a rather circuitous route. It began at the SAA’s 78th annual meeting in Hawaii, where I first meet Joanna Ostapkowicz. We were participants in a general session called By Design: Iconography in Social and Cosmological Negotiations, which included an interesting array of papers on everything from Dorset art to Egyptian textiles. Our papers contributed to enlarging the geographical scope to Florida (Wheeler: “Thinking about Animals in Ancient Florida”) and the Caribbean (Ostapkowicz: “The Sculptural Legacy of the Jamaican Taino”). Before and after the session we talked about how many iconographic wood carvings were known from Florida, from Key Marco to Fort Center and everything in between. Joanna suggested that the techniques she had been using with Caribbean wood carvings might have interesting applications in Florida. Many of the Caribbean pieces had traces of pigments and adhesives that were modified over relatively long periods of time. Some of this could be understood with a combination of microscopic examination and AMS dating. She also suggested that it might be possible to use isotopic analysis to understand the origin of a piece and how it could have been moved during its use life. In responding to slides in Ryan’s presentation, Joanna said something that was intriguing, namely that none of the carvings bore much similarity to Caribbean pieces, the potential connections between these geographically close areas remaining a hotly debated topic in some circles of Florida archaeology. We agreed to collaborate and decided that the Hontoon/Thursby and Tomoka carvings would be a good pilot study. We secured a National Environment Research Council (UK) grant to undertake AMS radiocarbon dating on the four sculptures. The results of that collaboration are explored in Chapter 9 of Watery Realms and in our recent article in the Journal of Archaeological Science: Reports. During our field trip to visit the Hontoon/Thursby and Tomoka carvings, we linked with many colleagues who are doing research on Florida’s wetsites, both collections-based study and reanalysis, and learned of new discoveries. After canvassing people about their work and interest, we decided to organize the SAA symposium.

Two images of archaeologist Barbara Purdy: Barbara Purdy during excavations at Hontoon Island, 1980 (left) and revisiting the Container Corporation of America site in Marion County, Florida, in 2017.
Barbara Purdy during excavations at Hontoon Island, 1980 (left) and revisiting the Container Corporation of America site in Marion County, Florida, in 2017. Courtesy of Barbara A. Purdy.

That is not really the whole story, however, as there was another person in the audience of our symposium who deserves a lot of credit for modern studies of Florida’s wetsites, wooden artifacts, and iconography. Nearly all of the presenters that day mentioned Barbara Purdy, professor emerita of the University of Florida. She led a statewide investigation of dugout canoe finds from the 1970s until her retirement in 1992, maintaining extensive files and documentation on hundreds of canoes. She also led excavations at Hontoon Island in the 1980s to probe the wetsite deposits there, followed by a project at Lake Monroe, where I had my first taste of wetsite archaeology as a graduate student in the 1990s. In fact, I tracked down several canoes with Purdy and fellow grad student Ray McGee in the early 1990s; this work prefigured my involvement in the Lake Pithlachocco canoe site some ten years later. In 1991, Purdy published a compendium of Florida’s wetsites in Art and Archaeology of Florida’s Wetlands, building on her statewide survey of wetsites in 1981. That book was followed by Indian Art of Ancient Florida, a survey of Florida’s American Indian art with photographer and curator Roy Craven. It is most appropriate that the Watery Realms book is dedicated to Barbara Purdy, a pioneer of Florida’s wetsite archaeology and studies of wooden artifacts and carvings. Purdy encouraged an appreciation of canoes as fascinating artifacts in their own right that embody information about past lifeways and deserve care and study. Purdy organized and hosted several international wetsite conferences that resulted in important proceedings on the subject and created a community of scholars dedicated to the documentation and preservations of wetsite artifacts. She has continued to advocate for more recognition for Florida wetsites. Archaeologists still avoid damp and low areas during surveys and seldom think about intentional prospecting for these important sites. That is changing, however, largely due to her work, which introduced many of us as students and professionals to the hidden world of wetsite archaeology.

Image of Hontoon Island owl carving.
The Hontoon Island owl carving displayed at the Florida State Museum (now Florida Museum of Natural History), shortly after it was found in the St. Johns River, circa 1955. Black & white photoprint. State Archives of Florida, Florida Memory. Accessed 13 May. 2019.

The rest of Chapter 1 introduces the environment of Florida and gives a brief overview of the other eight chapters, as well as some thoughts about major themes covered in the book and prevalent in wetsite archaeology. Copies are available from Amazon.com and directly from the University of Press of Florida.