| Location: | Mount Vernon, Mount Vernon, VA, United States |
|---|---|
| Occupation Dates: | c. 1735 through late-18th century. |
| Excavator(s): | Dennis Pogue and Esther White. |
| Dates excavated: | 1990-1994. |
Overview
Opening excavation units at the South Grove site, looking north. Mount Vernon mansion on the left.
In 1948, members of the Mount Vernon grounds crew excavated a large hole in the area known historically as the South Grove, located 80 feet south of George Washington’s house, in order to plant a mature holly tree. Numerous artifacts dating to the eighteenth century were recovered, suggesting that the South Grove area contained midden deposits formed from the disposal of kitchen and Mansion refuse during George Washington’s lifetime. In the spring of 1990 during construction of an irrigation system in the South Grove, the grounds crew once again encountered eighteenth-century deposits while installing a sprinkler head. Later that summer, a 10×10 foot unit (328) was placed near the hole, beginning systematic study of the feature. During the summers of 1991, 1992, 1993, and 1994, excavations expanded to include an additional 8 units (308, 309, 310, 329, 330, 348, 349, and 350), fully exposing the midden and excavating the feature’s strata. Documentary, stratigraphic, and artifact evidence date the midden’s layers from ca. 1735 through the end of the eighteenth century.
Documentary evidence
Gaullaudet University students excavate the South Grove site.
While the midden is an undocumented feature, supporting historical documents detail architectural and landscape changes that affected the South Grove and vicinity. The original house was constructed by Augustine Washington ca. 1735, though this household only lived there sporadically until Augustine’s death in 1743 (Dalzell and Dalzell 1998). Lawrence Washington, Augustine’s first born son from his first wife, inherited the property and moved there with his wife Anne Fairfax. After Lawrence married and moved to Mount Vernon, he made a number of undocumented architectural changes to the structure. Prior to Lawrence Washington’s death, our understanding of the development of the house and surrounding layout of the outbuildings derives from his estate inventory of 1753, in addition to architectural and archaeological evidence. A dairy and an earlier kitchen extended diagonally from the southwest corner of the mansion and were mirrored to the north by a wash house and store house. Because of the smaller size of the mansion in 1753 and the placement of the early kitchen, the South Grove Midden was located farther away from these two buildings than it is today.
Following Lawrence’s death, George Washington, his younger half-brother, rented the estate from his widow, Anne Fairfax Washington, including the house, goods, and slaves contained therein. Because George Washington was often away on military expeditions during his first years at Mount Vernon, his brother, John Augustine, and his wife oversaw the plantation in his absence. Towards the end of the French and Indian War, Washington began to plan and implement major changes to the house that would essentially double its size. In 1759, Washington returned to Mount Vernon to establish his household with his new bride Martha Dandridge Custis, a wealthy widow from Virginia’s tidewater. The archaeological record contains evidence of some of these changes in the form of large deposits of plaster rubble. A September 1758 letter recorded, “the great house has took a vast Deal of Sawing work besides a vast Deal of other work which the Carprs Did, puling Down the old works and Raising the new… as to puling Down the old plastering and leaths [sic.] out of the rooms I made the home house people Do and all other work as they could.” (Breen 2003; Abbot 1988[5]:447-448).
Map of Mount Vernon and South Grove Phase I: 1735-1758.
Most likely in the years that the refuse accumulated, the South Grove represented a workspace where activities occurred relating to the day-to-day operations of the plantation. Washington began ordering the space around the Mansion in the 1760s when he built walls for palisades “from the Great House to the Wash House and Kitchen also”, thereby enclosing the west front of the Mansion and providing a boundary between it and the South Grove area behind the outbuildings (Jackson et al. 1976[1]:257). Construction of these walls would have created a greater visual impact for visitors arriving by land from the west while simultaneously screening the work activities of slaves in and around the dairy and kitchen. By the end of the 1760s, buildings anchored the North and South Lanes suggesting that these boundaries also existed by then, too (John Milner Associates 2004).
Map of Mount Vernon and South Grove Phase II: 1759-1775.
Throughout the 1770s and 1780s, George Washington renovated Mount Vernon (adding wings and the piazza), constructed outbuildings, and formalized the surrounding landscape. Most significant to the South Grove area was the replacement of the old dairy and kitchen with a new kitchen, the installation of a large, vaulted brick drain, and the transformation of the South Grove from workspace to formal landscape. By 1775, Washington had torn down Lawrence’s flanking outbuildings and built in their place a servant’s hall to the north and a new kitchen to the south (John Milner Associates 2004:20). The South Lane was reorganized, new outbuildings populated its western side, and fences were constructed to further demarcate space. Also in 1775, a series of brick-lined drains were installed under the basement floor to channel the rainwater away from the house and into a large, barrel-vaulted brick drain (uncovered in the 1991 field season). This tightly dated feature provides a solid terminus ante quem for the bulk of the midden’s deposits intruded by its builder’s trench. The following year, Washington wrote to his plantation manager his vision for the South Grove – to include plantings of ornamental species (Pogue, White, and Breen 2005). Washington described “that at the South, of all the clever kind of Trees (especially flowering ones) that can be got, such as Crab apple, Poplar, Dogwood, Sasafras, Lawrel, Willow (especially yellow & Weeping Willow, twigs of which may be god from Philadelphia)…” (Abbot 1988[6]:84).
Excavation history, procedure, and methods
Map of Mount Vernon and South Grove Phase III: 1776-1800.
This multi-year project, led by Dennis Pogue and Esther White, resulted in the excavation of 400 contexts, 226 midden layers (Feature 1), 7 associated with the builder’s trench for the brick drain (Feature 2), and 1 associated with the brick drain (Feature 3). Excavators water-screened midden layers, taking flotation and soil chemical samples from each. Layers from the builder’s trench were dry-screened through ¼” mesh, with soil chemical samples collected. Twentieth-century layers and intrusions were dry-screened through 3/8″ mesh and nineteenth-century layers were primarily dry-screened through ¼” mesh, and both sampled for soil chemicals. One hundred percent of the heavy fraction, fine-screened material is processed and is included in this database. Specialized analyses of the botanical and faunal remains are completed and the soil samples have been analyzed for the presence of 10 chemicals.
Summary of research and analysis
Map of Mount Vernon and South Grove Phase IV: 1801-1858.
The Mount Vernon Archaeology Department has conducted extensive archaeological and historical research on the South Grove Midden (SGM). Site reports, a thesis, and multiple publications have resulted from this work (Breen 2003, 2004, Pogue, White, and Breen 2005). A dissertation is currently in process and a website dedicated to the spectacular objects and documentary record related to consumerism has recently launched at www.mountvernonmidden.org.
Here we discuss the results of two different methodological approaches used to date the South Grove Midden. The first methodological approached, employed by Eleanor Breen and her colleagues at Mount Vernon, used ceramic seriation, TPQ dating, vessel analysis, tobacco pipe dating, and the integration of documentary sources to identify and date six occupational phases at SGM. These phases were broadly dated from the 1730s to the 20th century. The second approach, employed by Jillian Galle and Fraser Neiman, consists of mean ceramic dating and correspondence analysis. CA resulted in five rather tightly dated phases whose MCDs ranged from 1725 to 1777.
The two methodological approaches to determining site chronology produced different yet complementary dates. We begin by discussing the Mount Vernon Chronology, followed by a review of the DAACS chronology, which is more fully explicated on the South Grove Chronology Page. We conclude with a comparison and discussion of these methods and their results.
Mount Vernon’s South Grove Chronology
Extensive work by Eleanor Breen, Mount Vernon’s Deputy Director of Archaeology, on phasing the complex midden stratigraphy (primarily due to disturbance by modern and historic intrusions) based on ceramic seriation, dating, vessel analysis, tobacco pipe dating, and the integration of documentary sources resulted in six phases. Breen built a Harris matrix based on the stratigraphic relationships documented in profiles, plan views, and on provenience cards. She then used TPQs from ceramics and marked pipes to provide relative dates for the layers. Additionally, relevant documentary evidence related to the construction of certain features like the brick drain and events such as the large plaster deposits and the construction of the mansion (documentary and TPQ dates aligned) provided dates. Breen and Mount Vernon staff then grouped the individual layers (driven by TPQs and documentary dates) into household-related phases. This macro-grouping of individual layers allowed Mount Vernon to link the northern, western, and southern sections of the midden, which had been divided and intruded by modern utilities and the brick drain (Breen 2003, 2004).
Table 1: Mount Vernon’s Phased South Grove Chronology
| Phase | Interpretation | Feature Assignment | Contexts in Phase |
|---|---|---|---|
| Phase 1: ca. 1735-1758 | Augustine Washington Household; Lawrence Washington Household | Feature 1 (Pit, Trash) | 308BB, 308CC, 308DD, 308EE, 309AAA, 309BBB, 309CCC, 309DDD, 309EEE, 309GGG, 309HHH, 309JJ, 309JJJ, 309KK, 309KKK, 309LL, 309LLL, 309MM, 309MMM, 309NN, 309NNN, 309PP, 309PPP, 309RR, 309RRR, 309SSS, 309TT, 309TTT, 309WW, 309WWW, 309XXX, 309YYY, 328AAA, 328BBB, 328CCC, 328DDD, 328FFF, 328GG, 328GGG, 328HH, 328HHH, 328JJ, 328JJJ, 328KK, 328KKK, 328LL, 328LLL, 328MM, 328MMM, 328NN, 328NNN, 328PPP, 328RR, 328RRR, 328SS, 328SSS, 328TTT, 328WWW, 328XX, 328YY, 329AAA, 329BBB, 329CCC, 329DDD, 329EEE, 329FFF, 329GGG, 329HHH, 329JJJ, 329KKK, 329LLL, 329MMM, 329NNN, 329PPP, 329RRR, 329SSS, 329TTT, 329WWW, 329XXX, 329YY, 329YYY, 348AAA, 348BBB, 348CCC, 348HH, 348JJ, 348KK, 348LL, 348MM, 348PP, 348SS, 348TT, 348WW, 348XX, 348YY, 349AAA, 349BBB, 349CCC, 349DDD, 349EEE, 349FFF, 349GGG, 349HHH, 349LL, 349MM, 349NN, 349PP, 349SS, 349TT, 349WW, 349XX, 349YY, 909A, 929A, 929AA, 929B, 929BB, 929BBB, 929C, 929CC, 929CCC, 929D, 929DD, 929E, 929EE, 929F, 929FF, 929FFF, 929G, 929GG, 929GGG, 929H, 929HH, 929J, 929JJ, 929K, 929KK, 929L, 929LL, 929M, 929MM, 929N, 929NN, 929P, 929PP, 929R, 929RR, 929S, 929T, 929TT, 929W, 929X, 929Y |
| Phase 2: ca. 1759-1775 | Early George and Martha Washington Household | Feature 1 (Pit, Trash) | 308AA, 309CC, 309DD, 309EE, 309FF, 309GG, 309HH, 309XX, 309YY, 328AA, 328BB, 328DD, 328EE, 328FF, 328R, 329BB, 329CC, 329DD, 329EE, 329GG, 329HH, 329JJ, 329KK, 329LL, 329MM, 329NN, 329PP, 329R1, 329RR, 329SS, 329TT, 329WW, 329XX, 330W, 330X, 330Y, 348BB, 348CC, 348DD, 348EE, 348FF, 348GG, 348RR, 349AA, 349BB, 349CC, 349DD, 349EE, 349FF, 349GG, 349HH, 349JJ, 349KK, 349RR, 929AAA, 929SS, 929WW, 929XX, 929YY |
| Phase 2: ca. 1759-1775 | Early George and Martha Washington Household | Feature 2 (Builder’s Trench) | 309AA, 309BB, 329R, 329S, 329W, 349JJJ, 929HHH |
| Phase 3: ca. 1776-1800 | Late George and Martha Washington Household | Feature 1 (Pit, Trash) | 308Y, 310K, 328H, 328K, 328Y, 329AA, 329FF, 329X, 329Y, 330T, 348AA, 349W, 349X, 349Y |
| Phase 3: ca. 1776-1800 | Late George and Martha Washington Household | Feature 3 (Brick Drain) | DELTA |
| Phase 4: 19th century | Bushrod Washington Household; John Augustine Washington II and III Households | None | 308N, 308P, 308R, 308S, 308T, 308W, 308X, 309M, 309N, 309P, 309R, 309S, 309SS, 309T, 309W, 309X, 309Y, 310J, 328G, 328J, 328L, 328M, 328N, 328P, 328T, 328X, 329L, 329M, 329N, 329P, 329T, 330L, 330M, 330N, 330P, 330R, 330S, 348W, 348X, 348Y, 349T, 350P |
| Phase 5: Modern intrusions and layers | Mount Vernon Ladies’ Association period | None | 308A, 308B, 308C, 308D, 308E, 308F, 308G, 308H, 308J, 308K, 308L, 308M, 309A, 309B, 309C, 309D, 309E, 309F, 309G, 309H, 309J, 309K, 309L, 310A, 310B, 310C, 310D, 310E, 310F, 310G, 310H, 328A, 328B, 328C, 328D, 328E, 328F, 328S, 328W, 329A, 329B, 329C, 329D, 329E, 329F, 329G, 329H, 329J, 329K, 330A, 330B, 330C, 330D, 330E, 330F, 330G, 330H, 330J, 330K, 348A, 348B, 348C, 348D, 348E, 348F, 348G, 348H, 348J, 348K, 348L, 348M, 348N, 348P, 348R, 348S, 348T, 349A, 349B, 349C, 349D, 349E, 349F, 349G, 349H, 349J, 349K, 349L, 349M, 349N, 349P, 349R, 349S, 350A, 350B, 350C, 350D, 350E, 350F, 350G, 350H, 350J, 350K, 350L, 350M, 350N |
| Phase 6: Buried Topsoil | None | None | 310L, 310M, 310N, 330AA, 330BB, 330CC, 330DD, 330EE |
| Unassigned | None | None | 1, 23, 125, 328DELTA, 349DELTA, 99/7, UNKNOWN |
Map of Mount Vernon and South Grove Phase V: 1859-1994.
Phase 1 potentially contains evidence of the Augustine Washington occupation, but because his ownership of the plantation was short-lived, we interpret the bulk of these deposits to Lawrence’s period. Ceramic vessels with a high degree of reconstructability in addition to the existence of matched sets suggest that both Phases 1 and 2 represent episodes of household cleaning at the time of Lawrence’s death and again when George Washington establishes his household with Martha Custis interspersed with refuse generated from daily activities such as cooking (Breen 2003, 2004).
Phase 2 represents the early George and Martha Washington household. Large deposits of plaster provide the terminus post quem for this phase, which correlates to the initial renovations of the house undertaken by Washington at the end of the French and Indian War. The terminus ante quem for Phase 2 is the construction of the brick drain (Features 2 and 3). The builder’s trench (Feature 2) intrudes Phases 1 and 2 (Breen 2003, 2004).
Phase 3 dates to the later George and Martha Washington household. In this phase, there is a significant decrease in artifact and faunal counts, suggesting that not only was Washington planting a formal landscape in the South Grove area, but that refuse disposal moved to a different location. The midden (Feature 1) ceases at the end of Phase 3.
Phases 4 and 5 are groups of contexts that date to the post-George Washington occupations of Mount Vernon and the transition of the estate from a working plantation to a museum. Ceramic TPQ dates support this interpretation.
Phase 6 represents evidence of historic topsoil or ground surface pre-dating the midden’s layers.
The refuse that accumulated within this deposit represents the material culture of a broadly defined, eighteenth-century Virginia plantation household whose members included the white plantation owner’s family and the enslaved men and women who lived and labored in and around the Mansion, kitchen, and dairy outbuildings. Plantation middens like this one embody a kind of spatial and artifactual middle ground between the big house and the quarter that force archaeologists to acknowledge and analyze the complexities of plantation household compositions and day-to-day activities. This “mixed” feature chronologically overlaps with the House for Families slave quarter, offering an unique opportunity to compare these two nearby plantation-related deposits. Key documents pertaining to the development of the enslaved community at Mount Vernon and the hired white workers have been compiled and can be accessed at www.mountvernonmidden.org.
DAACS’s South Grove Chronology
For each archaeological site in the archive, DAACS staff use correspondence analysis (CA) and ware-type manufacturing dates to develop and assign ceramic assemblages from excavated contexts to site-specific occupation phases. These methods and the resulting chronology for the South Grove Midden are described in detail on the South Grove Midden’s Chronology Page. The goal of DAACS chronologies is to produce replicable dates, such that other archaeologists can arrive at the same dates using the same methods, thereby increasing comparability among occupational phases at different sites.
As noted earlier, DAACS developed five occupational phases for the South Grove Midden (Table 2). These tightly-dated phases are the result of the correspondence analysis methods used by DAACS to develop the chronology. CA dates the center point of the accumulation of the ceramic assemblage, as measured by the mean-ceramic-dates of ceramic ware types. As a result, there can be a single late-dated sherd in the assemblage and the MCD or BLUEMCD for that phase can still be early. When using TPQs to date a site, a single late-dated sherd (or artifact) can push the entire assemblage date back to the TPQ of that single artifact.
Table 2: DAACS’s Phased South Grove Chronology (context assignments by phase can be found on the Chronology Page)
| Phase | MCD | BLUEMCD | TPQ | TPQp90 | TPQp95 | Total Count |
|---|---|---|---|---|---|---|
| P01 | 1725 | 1732 | 1725 | 1683 | 1720 | 277 |
| P02 | 1738 | 1740 | 1762 | 1715 | 1720 | 2622 |
| P03 | 1749 | 1752 | 1840 | 1720 | 1750 | 4753 |
| P04 | 1757 | 1765 | 1840 | 1762 | 1775 | 664 |
| P05 | 1777 | 1780 | 1840 | 1762 | 1820 | 135 |
The DAACS CA results suggest that the vast majority of ceramics in all South Grove Midden phases were manufactured in the 18th century evidenced by the fact of closely-dated phases spread over five decades. The dates for Mount Vernon’s phases, which developed using TPQs and the documentary record, are much more spread out.
Which Chronology Should You Use?
There is no right or wrong chronology. The two chronologies presented here were developed using different methods. Which method, and its resulting dates, a scholar use depends on the goals of any given analysis.
The Mount Vernon method relies heavily on TPQs and the documentary record. TPQs often provide clean dates for specific site formation events. For example, they are great for dating the deposit of sediment–when a sediment came to rest in the drain cut relative to other deposits on the site, such as the deposition of plaster from house renovations. The DAACS method relies solely on mean manufacturing dates of ceramic ware types using a replicable method. DAACS dates measure the center-point of an assemblage’s accumulation.
We compared the Mount Vernon and DAACS chronologies by creating mean ceramic dates and TPQs for the Mount Vernon Phases using DAACS’s basic MCD and TPQ methods (Table 3). The MCD and TPQs for the Mount Vernon Phases reveal five closely-dated phases, with the mean ceramic dates of the first four phases falling within a single ten-year period. On the other hand, MCDs for DAACS CA Phases are spread across five decades, perhaps more closely reflecting the phased spans of occupational use at the South Grove.
Table 3: MCDs and TPQs for Mount Vernon’s South Grove Phases developed using DAACS MCD and TPQ methods.
| Phase | MCD | BLUEMCD | TPQ | TPQp90 | Total Count |
|---|---|---|---|---|---|
|
1 |
1731 |
1750 |
1683 |
1720 |
2302 |
|
2 |
1733 |
1762 |
1720 |
1720 |
2620 |
|
3 |
1735 |
1775 |
1720 |
1720 |
901 |
|
4 |
1741 |
1840 |
1720 |
1762 |
2264 |
|
5 |
1750 |
1840 |
1762 |
1775 |
2748 |
|
6 |
1718 |
1670 |
1670 |
1670 |
20 |
We also created a contingency table of contexts relating Mount Vernon Phases to DAACS CA Phase (Table 4). It demonstrates that the majority of Mount Vernon’s phased contexts fall within DAACS CA Phases 1 and 2, again suggesting that the ceramics in the majority of South Grove contexts date to the mid-to-late 18th century. Here we see that many artifacts in Mount Vernon’s later phases (4-6) actually date to the 18th century.
Table 4: Contingency Table of Phased Context Assignments: Mount Vernon’s Phased Contexts by DAACS’s Phased Context.
| DAACS Phase 1 | DAACS Phase 2 | DAACS Phase 3 | DAACS Phase 4 | No Phase | Total | |
|---|---|---|---|---|---|---|
| Mount Vernon Phase 1 |
85 |
25 |
1 |
0 |
42 |
153 |
| Mount Vernon Phase 2 |
31 |
24 |
1 |
0 |
10 |
66 |
| Mount Vernon Phase 3 |
2 |
7 |
1 |
0 |
5 |
15 |
| Mount Vernon Phase 4 |
1 |
37 |
0 |
1 |
3 |
42 |
| Mount Vernon Phase 5 |
1 |
26 |
12 |
5 |
61 |
105 |
| Mount Vernon Phase 6 |
8 |
0 | 0 | 0 | 0 |
8 |
| No Phase |
2 |
3 |
0 | 0 |
15 |
20 |
| Total |
130 |
122 |
15 |
6 |
136 |
409 |
The MCDs, TPQs, and contingency table suggest that the South Grove’s successive, closely dated layers, which also have so many artifacts in them, do not contain secondary refuse but rather are primarily comprised of redeposited sediment from original mid-18th-century deposits. It seems probable that the original deposit was redeposited several times in the 18th century through pipe trenching and other activities so that even in the 18th century these deposits were heavily time averaged.
The clustered MCDs for the Mount Vernon Phases might also shed light on the formation processes at the South Grove. It seems possible to argue that the successive, closely dated layers that also have so many artifacts in them do not contain secondary refuse but rather are primarily comprised of redeposited sediment from the original deposits. It seems probable that the original 18th-century deposit was also likely redeposited several times in the 18th century through pipe trenching and other activities so that even in the 18th century these deposits were heavily time averaged. All of this does not mean that one phasing is correct and the other is not. Rather, it takes us back to the question of what type of analysis do you want to do and then, what dates should you use to do that analysis. Mount Vernon’s approach to phasing (through TPQs and documents) is right for dating the deposit of sediment, when exactly that sediment came to rest relative to, say, the drain installation or house renovations. DAACS CA phases date the center-point of an assemblage’s accumulation. These dates are ones that a researcher would want to use when comparing use and discard patterns of artifacts over time.
Eleanor Breen, with chronology additions by Jillian Galle
Mount Vernon Estate and Gardens
September 2013
Things you need to know about the South Grove Midden site before you use the data:
• Measurements are in feet and tenths of feet.
• There is no plowzone.
• Mount Vernon excavates stratigraphically using numeric contexts for horizontal control and alphabetical contexts for vertical control. The vertical controls work through single (A), double (AA), and triple designations (AAA). For units 309 and 329, once the triple letters were exhausted, excavators switched the numeric designations to 909 and 929, beginning with the single alphabet designation.
• The South Grove Midden site consisted of a 25 foot long by 20 foot wide refuse feature that was intruded by a large brick drain constructed ca. 1775 and by modern utilities and other disturbances. The refuse accumulated in a natural swale located south of Mount Vernon’s current Mansion and kitchen.
• The midden contains material culture relating to both enslaved individuals and the Washington households.
• The site was excavated over five field seasons.
• Artifacts from other areas of the South Grove dug up or excavated in previous years were not catalogued into the DAACS database, except when they crossmend or can be confidently associated with objects recovered in the 1990s excavations. Contexts that are not part of the South Grove Midden excavations include 125, 99/7, 23, 1, 324AA, 344R, 363T, and 364H.
Feature Numbers
The original excavators of the South Grove site assigned numbers to individual features. South Grove feature numbers were assigned consecutively throughout the entire project. Since South Grove feature numbers were assigned by the excavators, they do not have a F-prefix as DAACS-assigned feature numbers do.
Feature Groups
Feature groups are sets of features whose spatial arrangements indicate they were part of a single structure (e.g. structural postholes, subfloor pits, and hearth) or landscape element (e.g. postholes that comprise a fenceline). Feature Groups assigned by DAACS have a FG-prefix, which precedes the number (i.e. FG01 equals Feature Group 1).
| Feature | Feature Type | Contexts |
|---|---|---|
| 1 | Pit, trash | 328AA |
Intra-Site Chronologies
Figure 1. Plot of contexts along CA Dimensions 1 and 2. Time runs left (early) to right (late).
DAACS staff performs a standard set of analyses to produce a seriation-based intra-site chronology for each site included in the Archive. We aspire to use the same analytical methods for each site, specifically correspondence analysis of ware-type frequencies and ware-type manufacturing dates, to develop and assign ceramic assemblages from excavated contexts to site-specific occupation phases (see Neiman, Galle, and Wheeler 2003 for technical details). We provide a mean ceramic date (MCD) and terminus post quem (TPQ) for each intra-site phase. The phases are recorded in the DAACS Phase field of the database.
The use of common analytical methods is designed to increase comparability among phases at different sites. The methods, any changes we made to those methods that are specific to the site, and the phase assignments our methods produce are summarized below. DAACS encourages users of Archive data to help explore improvements to our methods.
For some sites, the original excavators developed intra-site chronologies and, where these exist, they are described on the Background page for the site. They are also associated with individual contexts through the Excavator Phase field and can be accessed through Context Query.
Figure 2. Plot of Ware Types along CA Dimensions 1 and 2.
In the case of the South Grove, the site’s principal investigators developed a six-phase site chronology based on ceramic seriation, dating, and vessel analysis, tobacco pipe dating, and the integration of documentary sources. The Mount Vernon chronology differs from the DAACS Intra-Site Chronology presented below. The differences between the Mount Vernon (Excavator Phase) chronology and the DAACS (DAACS Phase) Chronology are discussed in the South Grove’s Background Page.
DAACS Seriation Method
As with other sites in the Archive, the seriation chronology for the South Grove project was derived from ceramic assemblages aggregated at the level of stratigraphic groups and individual contexts not assigned to stratigraphic groups. To reduce the noise introduced by sampling error, only ceramic assemblages with more than 5 sherds and more than two ceramic types were included. The seriation chronology presented here is the result of a correspondence analysis (CA) of ware-type frequencies from contexts that meet these requirements (Figures 1 and 2).
The CA results produced a strong correlation between Dimension 1 scores and MCDs (Figure 3), indicating that Dimension 1 represents time from left to right. Based on the dips in ceramic counts observed in a histogram of Dimension 1 scores, where the vertical axis measures ceramic assemblage size, we divided the site into five occupational phases (Figure 4).
Figure 3. CA Dimension 1 scores plotted against Mean Ceramic Dates.
In addition to revealing temporally distinct assemblages, the CA demonstrates that there is interesting and significant synchronic variation during the earlier occupation phases at the South Grove. Returning to Figure 1, note that the point scatter is more widely arrayed along Dimension 2 to the right of the zero point on Dimension 1 than to the left . Figure 2 shows which ceramic ware types contribute to the assemblage locations along Dimension 1 and Dimension 2: type locations on Dimensions 1 and 2 are correlated with the locations of assemblages in which they are most frequent.
Figure 5 highlights these assemblages, with assemblages in Group 1 disproportionately comprised of North Devon, Group 2 assemblages dominated by early-to-mid 18th century tablewares (Astbury, Staffordshire Mottled, Westerwald, North Midlands Slipware), Group 3 assemblages dominated by Colonoware, Post-Medieval London Redware, and Delftware, and Group 4 dominated by mid-to-late 18th century table, tea, and utilitarian wares.
It is not clear what this synchronic variation represents. Possibilities include variation among different households or activity variation within a single household. What is clear is that this variation has no horizontal spatial expression within the excavated area: When the mean northings and eastings of the contexts were plotted by CA group, no spatial patterns emerged (Figure 6). If the assemblage came from different sources, they were dumped in the same place.
Figure 4. Histogram of ceramic counts plotted along CA Dimension 1. The lines indicate DAACS phase divisions, with phase 1 on left, phase 5 on right.
Figure 5. Plot of contexts along CA dimensions 1 and 2, color coded by CA Group to highlight synchronic variation.
Figure 6. Plot of CA Group contexts by the Northing and Easting centroids, suggesting that there is little spatial correlation among contexts within the same CA Group.
South Grove Site Phases
DAACS 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 Ware 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 Ware 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 | MCD | BLUEMCD | TPQ | TPQp90 | TPQp95 | Total Count |
|---|---|---|---|---|---|---|
| P01 | 1725 | 1732 | 1725 | 1683 | 1720 | 277 |
| P02 | 1738 | 1740 | 1762 | 1715 | 1720 | 2622 |
| P03 | 1749 | 1752 | 1840 | 1720 | 1750 | 4753 |
| P04 | 1757 | 1765 | 1840 | 1762 | 1775 | 664 |
| P05 | 1777 | 1780 | 1840 | 1762 | 1820 | 135 |
A Seriation Chronology for the South Grove
The following table presents a seriation chronology for the South Grove 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. DAACS 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.
South Grove Harris Matrix
The Harris matrix summarizes stratigraphic relationships among excavated contexts and groups of contexts that Mount Vernon staff has identified as part of the same stratigraphic group. Stratigraphic groups and contexts are represented as boxes, while lines connecting them represent temporal relationships implied by the site’s stratification, as recorded by the site’s excavators (Harris 1979).
Stratigraphic groups, which represent multiple contexts, are identified on the diagram by their numeric designations (e.g. SG06). Contexts that could not be assigned to stratigraphic groups are identified by their individual context numbers (e.g. 328AAA).
Here we provide two Harris matrices. They are identical with the exception of the phase assignments, which are denoted by different colors. The first Harris matrix is color-coded with Mount Vernon Excavator-Assigned Phases. The second Harris matrix contains boxes with color fill representing contexts and stratigraphic groups with ceramic assemblages large enough to be included in the DAACS seriation of the site (see Chronology). Their seriation-based phase assignments are denoted by different colors to facilitate evaluation of the agreement between the stratigraphic and seriation chronologies. Grey boxes represent contexts that were not included in the seriation because of small ceramic samples.
This Harris matrix is based on data on stratigraphic relationships recorded among contexts in the DAACS database. It was drawn with the ArchEd application. See http://www.ads.tuwien.ac.at/arched/index.html.
See South Grove Chronology for stratigraphic and phase information. Please note that some of the contexts present in the chronology analysis are not visualized on the Harris Matrix. The contexts that are not included do not have any stratigraphic relationships with other contexts. The lack of relationships can occur for a few reasons but two common examples are 1) the artifacts are from a surface collection, which is entered into DAACS as a context but does not have recorded relationships to other contexts that are below it; 2) in cases where topsoil and plowzone are stripped and discarded, there may be features below the plowzone that are comprised of a single context. Since the plowzone does not exist as a documented context with artifacts, it cannot seal the single-context feature. DAACS also does not record subsoil as a context, so there is nothing for that single context feature to intrude or seal.
For a printable version of the Harris matrix based on Mount Vernon Excavator-Assigned Phases, download the Harris matrix [506 KB PDF].
For a printable version of the Harris matrix based on DAACS seriation, download the Harris matrix [508 KB PDF].
PDF of Composite excavator’s plan, compiled by Luke Pecoraro from original field drawings, with excavation units and features labeled.
PDF of composite excavator’s plan, compiled by Luke Pecoraro from original field drawings, with only excavation units labeled.
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