Building l Chronology
DAACS has developed a uniform set of methods 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 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 for the Building l site that was developed by DAACS (see Neiman, Galle, and Wheeler 2003 for technical details). DAACS seriated ceramic assemblages, with more than five sherds, from individual excavated contexts and from stratigraphic groups—groups of contexts that field records indicate were part of a single stratigraphic layer or deposit. Stratigraphic Groups have a SG-prefix, which precedes the group number (e.g. SG01 equals Stratigraphic Group 1). For example, at the Building l site, two portions of a single layer, described by the excavators as ‘reddish brown loam”, spanned two adjacent quadrats (342 and 343). The layer segments were excavated as 342E and 343G. DAACS assigned these contexts to a single stratigraphic group (SG05). Not all contexts have stratigraphic group assignments.
DAACS chose to base the seriation chronology for the Building l site on 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. In the few cases where stratigraphic groups and contexts were parts of features, the relevant feature numbers and descriptions are included in the seriation chronology table below.
DAACS computed the frequency of mean-ceramic-date (MCD) types in stratigraphic groups and in individual contexts when those contexts had no stratigraphic group assignment. The seriation chronology is derived from a correspondence analysis of these MCD-type frequencies. Seriated assemblages were assigned to phases. Phases are groups of assemblages that have similar correspondence-analysis scores and are therefore inferred to be broadly contemporary. Phases assigned by DAACS have a P-prefix that precedes the phase number (e.g. P01 equals Phase 1).
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.
Building / Phases
Based on the correspondence analysis, DAACS divided the Building l site occupation into six phases. Mean ceramic dates for the six phases are given in the table below. The table also includes two estimates of the 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 is a small assemblage derived from limited excavation of layers (SG01 and SG02) that lay below the brick and cobble floor (F01, F03) of Building l, shown on the 1796 Mutual Assurance Plat. These assemblages attest to the presence of a significantly earlier occupation at the site, most of which is still covered by the floor. Phases two, three, four, and five contain the remains of the Building l occupation from about 1790 until Jefferson’s death in 1826. The contrast between TPQ and TPQp90 values for phases three and four indicates they contain a few anomalously late sherds as well as Jefferson-era material. Phase six contains significantly more post-Jefferson material than the others.
The phases for the Building l site are among the most massively time averaged on Mulberry Row. Each phase represents deposition over many decades and there is considerable overlap between the periods represented by successive phases. This is the result of both site formation processes and excavation and analytical errors which may have combined, in a single context or stratigraphic group, deposits from different time periods. Among the special complications affecting Building l are excavations in 1957 that resulted in two test trenches across the site and partial excavation of the sediment covering the brick and cobble foundation (Pi-Sunyer and Bear 1957, Scholnik et al. 2001). Improving temporal resolution among individual contexts for phases two through five may be possible in the future.
A Seriation Chronology for the Building l Site
The following table presents a seriation chronology for the Building l site. We use the indefinite article to signify that it is not the only chronology possible, nor the best. DAACS encourages users of Archive data to help explore improvements.