Vignette: Building a Prehistory for the Maritimes

Archaeologists use a number techniques to determine the chronological placement of sites and artifacts within a regional culture historical sequence. The stratigraphy, or depositional layers, within a site, are normally laid down in a chronological fashion. Sometimes, at multi-component sites, distinct cultural layers may overlap in some areas and not in others. Multi-component sites are often very shallow in this region, with two or more components occurring within 10-15 cm of overall deposit. Each cultural group using the site is likely to disturb earlier deposits in heavy use areas and subsurface features. Even short-term post-abandonment disturbances, such as plowing, can create havoc with the stratigraphy of shallow archaeological sites.

In practice, most sites, features, and artifacts are dated through association with wood charcoal, or other organic materials such as shell, that can dated using the radiocarbon dating method. This is an absolute dating method that is based on the radioactive decay of Carbon-14 (C-14). Libby's technique relied on the assumption that the ratio of radioactive C-14 and normal C-12 remained constant over time. Dendrochronological (Tree-ring) studies proved that there have been considerable variations in the atmospheric concentration of C-14 over time. Today, radiocarbon dating laboratories provide both uncorrected and corrected (or calibrated) dates. A more recent method of radiocarbon dating, known as the accelerator mass spectrometric (AMS) technique can be used to determine dates on much smaller samples. A list of all the reported radiocarbon dates, and associated materials, for the Maritime Provinces appears in Appendix A.

The seriation of prehistoric ceramic styles has provided the framework against which archaeologists in Northeastern North America interpret local and regional culture histories for the Woodland Period (Petersen 1985:6-8; Ritchie 1985). In 1991 an elaborate ceramic chronology was proposed for Maine and the Maritimes by Petersen and Sanger (1991), based on comparisons of ceramic stylistic, morphological and physical attributes with associated radiocarbon dates from dozens of Ceramic Period sites. This chronology replaced a longstanding tripartite system (i.e., Early, Middle and Late Ceramic) with a seven part chronology that was designated Ceramic Periods one through seven (or, CP1 to CP7; see Table 1). A refinement of this model was proposed by Kristmanson (1992) for southwestern Nova Scotia, using 20 radiocarbon and two thermoluminescence dates from five sites. Kristmanson's study suggests that the new Ceramic Period divisions are widely applicable, yet there is considerable variation in the date ranges for each period in different portions of the broad Maine/Maritime region. Both Petersen and Sanger (1991) and Kristmanson (1992) distinguish between direct and general associations between C14 dated samples and ceramics. Direct associations indicate a clear connection between the C14 date and ceramic vessel(s), such as recovery from the same feature or physical contact between the dated charred organic sample and the ceramic sherd. All other associations are considered to be less reliable and are given a general ascription.


Ceramic Period subdivisions and temporal equivalents(Petersen and Sanger 1991:135) .

Ceramic Period Subdivisions - Temporal Equivalents (B. P.)
Ceramic period One (Early Ceramic) - ca. 3050-2150
Ceramic Period Two (early Middle Ceramic) - ca. 2150-1650
Ceramic Period Three (middle Middle Ceramic) - ca. 1650-1350
Ceramic Period Four (late Middle Ceramic) - ca. 1350-950
Ceramic Period Five (early Late Ceramic) - ca. 950-650
Ceramic Period Six (late Late Ceramic) - ca. 650-400
Ceramic Period Seven (Contact, or Early Historic) - ca. 400-200

In 1993 the thermoluminescence (or TL) dating technique was used for dating ceramics at the St. Croix site. The Luminescence laboratory at the Department of Earth Sciences, Dalhousie University is the only facility in eastern Canada where the work can be conducted. The TL dating technique is preferred over radiocarbon dating since it provides a date for the ceramic sherd itself (and its design elements) rather than from associated charcoal. However, field collection procedures are more rigorous for TL analysis and there are more opportunities for both natural and cultural contamination. An earlier attempt to apply TL analysis to four specimens from the Brown site (BeCs-3) was abandoned due to contamination problems (Sheldon 1988:40). Basically, thermoluminescence dating works on the principle that small amounts of energy accumulate in the minerals in the clay matrix of a ceramic vessel (as trapped electrons). When a ceramic piece is fired some of the accumulated energy is released as light and energy begins to build up again in the vessel. After excavation, a ceramic sherd can be reheated to release the energy accumulated since its original firing. The light from the reheating, known as the thermoluminescent signal, can be used to calculate the time elapsed since the vessel was last heated. The six TL dates determined for St. Croix ceramics do not completely agree the Petersen and Sanger chronology and therefore support Kristmanson's conclusion that some local and intra-regional variation exits in the ceramic chronology (Godfrey-Smith et al. 1997).

References

Godfrey-Smith, D.I., M. Deal, and I. Kunelius
1997 Thermoluminescence Dating at the St. Croix Site: Chronology Building in Southwestern Nova Scotia. Geoarchaeology 12(3):251-273.

Kristmanson, H.
1992 The Ceramic Sequence for Southwestern Nova Scotia: a Refinement of the Petersen/Sanger Model. M.A. thesis, Archaeology Unit, Department of Anthropology, Memorial University of Newfoundland, St. John's.

Petersen, J. B.
1985 Ceramic analysis in the Northeast: resume and prospect. In Ceramic analysis in the Northeast: contributions to methodology and culture history, edited by J. B. Petersen, pp. 5-25. Occasional Publications in Northeastern Anthropology 9(2).

Petersen, J. B., and D. Sanger
1991 An Aboriginal Ceramic Sequence for Maine and the Maritime Provinces. In Prehistory of the Maritime Provinces: Past and Present Research, edited by M. Deal and S. Blair, pp. 113-170. Council of Maritime Premiers, Reports in Archaeology 8. Fredericton.

Ritchie, W. A.
1985 Fifty years of archaeology in the northeastern United States: a retrospect. American Antiquity 50(2):412-420.

Sheldon, H. L.
1988 The Late Prehistory of Nova Scotia as Viewed from the Brown Site. Nova Scotia Museum, Curatorial Report 61. Halifax.

 

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