We perform a standard set of analyses to infer intra-site chronologies for the sites included in the Archive. Using them, we have assigned most excavated contexts at each site to a set of site-specific phases. The use of common analytical methods is designed to increase comparability among phases at different sites. The methods and the phase assignments they produced are summarized below. For some sites, the original excavators developed intra-site chronologies and, where these exist, they are included on the Background page for the site. DAACS encourages users of Archive data to help explore improvements.
DAACS Seriation Method
This page summarizes a frequency-seriation based chronology we developed for the MRS 2 site (see Neiman, Galle, and Wheeler 2003 for technical details).
As with other sites in the Archive, the seriation chronology for MRS 2 was derived from ceramic assemblages aggregated at the level of contexts and stratigraphic groups, and not at the level of features. This is because most contexts and stratigraphic groups on the site were not parts of features. For the relatively few cases where seriated contexts and stratigraphic groups were parts of features, the relevant feature numbers and descriptions are included in the seriation chronology table below. The seriation chronology is the result of a correspondence analysis of MCD-type frequencies in each stratigraphic group and each individual context that had no stratigraphic group assignment (Figures 1 and 2). Not all contexts have stratigraphic group assignments.
To reduce the noise introduced by sampling error, only ceramic assemblages with more than 5 sherds and more than one ceramic type from individual excavated contexts and from stratigraphic groups were included. Redware was removed from the seriation of MRS 2 due to unusually high contributions of this ware type to inertia. The subsequent results produced a strong correlation between Dimension 1 scores and MCDs (Figure 3). Based on the dips in ceramic counts observed in a histogram of Dimension 1, we divided the Building m site into four phases (Figure 4).
MRS 2 Phases
Phases are groups of assemblages that have similar correspondence-analysis scores, similar MCDs, or both, and are therefore inferred to be broadly contemporary. Phases have a P-prefix that precedes the phase number (e.g. P01 equals Phase 1).
Mean ceramic dates for the site-specific phases are given in the table below. The table also includes two estimates of the ceramic TPQ for each phase. The first TPQ estimate is the usual one – the maximum beginning manufacturing date among all the MCD types in the assemblage. The second estimate -- TPQp90 -- is the 90th percentile of the beginning manufacturing dates among all the sherds in the assemblage, based on their MCD-types. This TPQ estimate is more robust against excavation errors and taphonomic processes that might have introduces a few anomalously late sherds in an assemblage.
Phase one assemblages are generally lower stratigraphically and include one deposit within the cellar (F09) of MRS 2 as well as layers cut by (SG13) and sealing (SG02) the feature. Phase two assemblages come from two important SGs, a garden fenceline deposit (SG27) and a clay layer with greenstone (SG16). The latter, SG16, although stratigraphically between two Phase one fills, contains only creamware and chinese porclain, suggesting it too may be a phase one assemblage. Its small sample, with no mid 18th century types, may have set it off from the other phase one assemblages in the CA. Phases three and four have increasingly substantial amounts of post-Jefferson material, as indicated by the late MCD, TPQ, and TPQp90.
A Seriation Chronology for MRS 2
The following table presents a seriation chronology for the MRS 2 site. We use the indefinite article to signify that it is not the only chronology possible, nor the best. We encourage users of Archive data to help explore improvements.
The stratigraphic relationships among stratigraphic groups and unassigned contexts are summarized in the Harris Matrix for the site. Phase assignments from the seriation are shown on the Harris Matrix in color, facilitating comparison of the seriation chronology and the stratigraphic chronology of the site.