Optically Stimulated Luminescence (OSL) data and ages for selected Native American Sacred Ceremonial Stone Landscape features--Final Project Report Submitted to the Narragansett Tribal Historic Preservation Trust

Stone rows, enclosures, structures and chambers can be found in the landscapes of Massachusetts and Rhode Island. Structures similar to those shown in the cover photo are documented elsewhere. The age, cultural affiliation, and purpose of these stone structures--which are found in a variety of forms, such as piles arranged in spatial configurations across landscapes, shapes suggesting animal effigies, platforms and chambers--have been the subject of much debate. Some have argued they are remnants of colonial agricultural and storage practices; others that they are prehistoric Native American ceremonial structures. Ascertaining the time periods of their creation had previously been impossible. We felt that optically stimulated luminescence (OSL) had the potential to provide meaningful insights into their origins. 
In June 2018, samples for luminescence dating were taken from three sites: the Pratt Hill Site near Upton, located in south central Massachusetts; the Tolba Site of Leverett, located in western Massachusetts; and the Site of Hopkinton, Rhode Island. These samples were taken from hand-dug pits beneath stone structures to depths past modern soils into the geomorphic feature upon which the stones were placed (i.e. alluvial fan or terrace). The object of this excavation was to date the placement time of the stones onto the geomorphic feature. Luminescence chronology is an ideal scientific measurement, since the physics of the phenomenon mean that it dates the last time mineral grains of quartz and feldspar were exposed to sunlight or heat above 150 °C. All sediment samples were dated using OSL on very small aliquots of &lt;50-10 grains. 
The age of the sample from the Site of Hopkinton, Rhode Island is in the range of 1570-1490 C.E (or 490 ± 40 years ago). The ages of the samples from Pratt Hill near Upton, Massachusetts, at a site that was recently desecrated by being scraped off the boulder foundation it was originally built on, are 1475-1375 C.E. (595 ± 50 years) for the top sample and 1315-1835 B.C.E (3,595 ± 260 years) for the bottom sample. These samples were obtained from dust or loess that had blown into the structure and collected in the scooped out hollow of the boulder foundation. The ages of the Tolba site in Leverett, Massachusetts cover the ranges of 1670-1510 C.E. (430 ± 80 years), 1730-1570 C.E. (370 ± 80 years), 1420-1220 C.E. (700 ± 100 years) at the base. A sample obtained beneath a housing foundation and into the land surface very near to this site also gave an age range of 1470-1230 C.E. (670 ± 120 years). A brick used in the house manufacturing was also taken back to the lab for luminescence dating but data are not available at this time. 
In a previous study of OSL dating performed on sediment from the Upton Chamber Site, it was established that European contact was documented in Plymouth at 1620 C.E., in Boston at 1630 C.E. and Upton at 1660 C.E. It is interesting that most of the currently sampled stone ceremonial structure ages are falling in the Upton time frame (455 to 580 years ago, with one lower age at 700 years) except for the lower Pratt Hill sample, which is considerably older than any other previous age obtained. One theory is that the ceremonial structures were sacred sites that were cared for and maintained during the years of sole Native American occupation. This theory postulates that as Europeans settlers disseminated across the landscape, the disease and displacement they brought largely ended the Native population’s ability to maintain these sites and that the OSL dating documents this time of disrepair instead of an original placement of stones on a geomorphic surface. Clearly, further work is warranted at these and other sites, since the older age of 3,595 ± 260 years is an intriguing and valued look into the earliest dates of construction to these features.

Tags: age-estimation-methods, archeology, geochronology, hopkinson, leverett, luminescence-dating, massachusetts, new-england, optically-stimulated-luminescence, pratt-hill, radiation-dosimetry, usgs-5f6a595082ce38aaa24493cf
Organization: Department of the Interior