Freshwater reservoir offsets on radiocarbon-dated dog bone from the headwaters of the St. Lawrence River, USA

Abstract

Isotopic analysis of dog (Canis lupus familiaris) bone recovered from archaeological sites as proxies for human bone is becoming common in North America. Chronological placement of the dogs is often determined through radiocarbon dating of dog bone. The Great Lakes, their tributaries, and nearby lakes and streams were important fisheries for Native Americans prior to and after sustained European presence in the region. Carbon entering the food web in freshwater systems is often not in full isotopic equilibrium with the atmosphere, giving rise to spuriously old radiocarbon ages in fish, other aquatic organisms, and their consumers. These freshwater reservoir offsets (FROs) have been noted on human and dog bone in several areas of the world. Here we report the results of multi-tracer Bayesian dietary modeling using δ15N and δ13C values on dog bone collagen from mid-fifteenth to mid-sixteenth-century Iroquoian village sites at the headwaters of the St. Lawrence River, New York, USA. Results indicate that fish was an important component of dog diets. A comparison of radiocarbon dates on dog bone with dates on deer bone or maize from the same sites indicate FROs ranging from 97 ± 24 to 220 ± 39 14Cyr with a weighted mean of 132 ± 8 14Cyr. These results suggest that dog bone should not be used for radiocarbon dating in the absence of modeling to determine fish consumption and that previously reported radiocarbon dates on human bone from the larger region are likely to have FROs given the known importance of fish in regional human diets.

Radiocarbon Dating the Iroquoian Occupation of Northern New York

“…familiaris ) bone, which appear to have offsets relative to ages on maize ( Zea mays ssp. mays ) and/or white-tailed deer ( Odocoileus virginianus ) from the same sites (Hart, Feranec et al 2019). We also eliminated an erroneous date on white-tailed deer bone from the St. Lawrence site (UCIAMS-204716), bulk sample dates as discussed above, and a modern determination from Whitford (UGAMS-30329).…”

“…Over the last 30 years, the Iroquoian occupations of Northern New York have received a renewed research focus. Reanalyses of older data (Engelbrecht 1995, 2004; Engelbrecht et al 1990), in conjunction with the publication of new excavations and analyses (Abel 2001, 2015, 2016; Baron et al 2016; Dermarkar et al 2016; Engelbrecht and Jamieson 2016a, 2016b; Hart et al 2017; Hart, Winchell-Sweeney, and Birch 2019; Jones et al 2018; Vavrasek 2010; Wonderley 2005), have greatly increased our understanding of this once-enigmatic region and period (Abel 2019a). As a result of this research, it is apparent that the region and its inhabitants played a far more integral role in the broader social, economic, and political fabric of greater Iroquoia than had been previously acknowledged.…”

Zooarchaeological assemblages contextualize the historical ecology and harvest of fur-bearing mammals in Vermont

“…The location of Ewing site (Shelburne Pond) contains dolomite that could cause a reservoir effect as 14 C depleted carbon dissolves from bedrock into the water and is taken up into non-emergent aquatic vegetation (Lini et al, 2007). While Hart et al (2019) found a freshwater offset of 132 ± 8 14 Cyr for dogs consuming freshwater resources on the St. Lawrence River, Plint et al (2019) did not include such an offset for paleontological beaver remains, and beavers are known to rely on terrestrial vegetation (Supplementary material); therefore, we did not apply a freshwater reservoir correction. Our muskrat and beaver radiocarbon dates are in line with expectations from contextual charcoal-based dates from the site that would be unaffected by this reservoir effect (Supplementary Figure 1).…”

Differentiating salmonid migratory ecotypes through stable isotope analysis of collagen: Archaeological and ecological applications

“…It is important to note that, unlike the correction used for anadromous fish, the equation used for potamodromous fish does not account for temporal offsets related to the complexities of freshwater aquatic carbon cycling. An increasing number of 14 C studies highlight the wide range of variation that can occur in the age and reservoir period for DIC used by primary producers at the base of freshwater environments, which can extend to hundreds and even thousands of years [e.g., [103][104][105][106][107][108][109][110]. This offset means that there may be considerable temporal lag between the impact of the Suess effect on the isotopic composition of atmospheric and freshwater DIC pools.…”