DAACS Seriation Method
DAACS staff aim to produce a seriation-based chronology for each slave-quarter site using the same methods (see Neiman, Galle, and Wheeler 2003 for technical details). Only assemblages from features or stratigraphic groups with more than five ceramic sherds are included in these ceramic-based seriations. Plowzone contexts do not contribute to a DAACS seriation-based chronology. Four features at Ashcomb's Quarter (18CV362) contained more than 5 ceramic sherds (F14=8 sherds; F16=144 sherds; F22=52 sherds; F68=57 sherds). DAACS computed the frequency of mean-ceramic-date (MCD) types contained in these features. 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.
Ashcomb's Quarter Site Phases
Based on the correspondence analysis, DAACS divided the Ashcomb's Quarter site occupation into 2 phases. The ceramic assemblage from the prehistoric shell midden (F68) emerged in the correspondence analysis as an outlier in relation to the other assemblages, signaling its distinctive composition, and justifying its placement in a separate phase (P01). All 57 ceramic sherds found in the shell midden (F68) were Native American ceramics known as Yeocomico Wares which date to the late Woodland Period. Native American ceramics are not assigned mean ceramic dates and therefore no MCDs or TPQs were calculated for Phase 1.
The ceramic assemblages from F14, F16, and F22 fall into Phase 2 (P02), which represents the historic-period occupation of this site. A Mean Ceramic Date and three TPQ measures were calculated for this phase.
The stratigraphic relationships among features, 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.
Ashcomb's Quarter Site-wide Mean Ceramic Date and TPQs
Only 204 sherds from three features contribute to the seriation-based Phase 2 MCD and TPQs. Those dates suggest that the historic-period occupation of Ashcomb's Quarter fell solidly in the middle of the eighteenth century, with an early TPQp90 of 1720. However, the site-wide Mean Ceramic Date, derived using all ceramic sherds excavated from the site (n=1107), suggests a slightly later occupation in the late-third quarter of the eighteenth century.
Two other measures that are less sensitive to excavation errors and taphonomic processes that might introduce a small amount of anomalously late material into an assemblage were used. They are TPQp90 and TPQp95. The TPQp95 of 1775 provides a robust estimate of the site's TPQ based on the 95th percentile of the beginning manufacturing dates for all the artifacts comprising it. The TPQp90 of 1762 provides a more robust estimate of the site's TPQ based on the 90th percentile of the beginning manufacturing dates for all the artifacts comprising it.
A Seriation Chronology for Ashcomb's Quarter
Click on the following link to access a seriation chronology for Ashcomb's Quarter (18CV362). We use the indefinite article to signify that it is not the only chronology possible, nor even the best one possible.