Chronology is a necessary first step to wringing historical meaning from the archaeological record. Because the archaeological record is a contemporary phenomenon, time is an inferred dimension in archaeology. Here we present three different types of chronologies for the NAVAIR site using methods we have developed to infer and evaluate archaeological chronologies for artifact assemblages included so far in DAACS.

This page provides three different types of chronologies for the NAVAIR site. These chronologies are described below. Chronologies for every archaeological site in DAACS are produced by DAACS staff using the same methods. As a result, DAACS chronologies are standardized and provide the best means for comparing data from multiple sites and regions.

Our choice of methods is driven by both theoretical and practical considerations. On the theory side, we are interested in placing assemblages as events in time so that we can chart trends in assemblage content - say the frequency of tea vessels - across multiple sites. However, assemblages are not instantaneous events. Assemblages accumulate over periods of time, usually decades. Some chronological methods in historical archaeology provide estimates of the mean of the assemblage temporal distribution, while others do not. Termini post and ante quem, the most commonly encountered methods, are estimates of the upper and lower extreme values of the assemblage temporal distribution, not its mean. They are therefore poorly suited to our purposes. Two methods, frequency seriation and mean ceramic dating, do offer estimates of temporal distribution means and we rely on them here. We do, however, provide TPQs in the following analyses.

Phase assignments, mean ceramic dates, and TPQs are generated using ceramic ware dates found on the Ceramic Ware and Mean-Ceramic-Date Types page in the About the Database section. If a site's principal investigator produced a site chronology using different dates and methods, it is discussed on the site's background page. DAACS users are also encouraged to explore the Mean Ceramic Date Queries for dating individual contexts, features, and stratigraphic groups.

For each site, DAACS staff attempt to produce an intra-site chronology using seriation methods. The units in the seriation are ceramic assemblages from contexts with more than five sherds. Plowzone and topsoil contexts are excluded from this analysis. An initial seriation solution is derived using correspondence analysis of type frequencies in the assemblages. This order is then compared to an order derived from mean ceramic dates. If the orders are correlated, we assign assemblages - and the contexts and stratigraphic groups to which they belong - to phases based on their CA scores. Phases can be further evaluated by plotting them on a Harris Matrix (for details see Neiman, Galle and Wheeler 2003).

At NAVAIR, only four contexts contained over five ceramics.  The CA did not produce an ordered seriation for these four contexts, therefore no phases were assigned.

DAACS staff also produce a site-wide Mean Ceramic Date and TPQs using ceramic-ware types from all stratified, non-plowzone contexts at a given site. A total of 164 ceramic sherds from stratified contexts at NAVAIR contributed to the following dates.

NAVAIR's Mean Ceramic Date of 1789.5 places the site's occupation solidly in the fourth 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 1762 provides a robust estimate of the site's TPQ based on the 95th percentile of the beginning manufacturing dates for all the ceramics 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 ceramics comprising it.

Finally we provide a mean ceramic date and TPQs that are generated using ceramics from all archaeological contexts at the NAVAIR site, including topsoil and plowzone contexts, as well as data from shovel-test-pits. A total of 996 sherds contributed to these dates.