Archaeological Prospection of the Hatfield Site, a Monongahela Tradition Village in
Washington County, Pennsylvania
Jason Espino, Seth Van Dam, Ashley Brown, and Marion Smeltzer
Report completed for fulfillment of Specialized Methods in Archaeology: Archaeological
Geophysics (Anth 584) course requirements.
i
ACKNOWLEDGEMENTS
This project could not have been completed without the generosity of the Anthropology
Department at Indiana University of Pennsylvania (IUP). The department provided the
geophysical and spatial equipment necessary for the survey as well as transportation to and from
Indiana, Pennsylvania. Equally generous were the Mansfield family for allowing access to the
property on which the Hatfield site is located. They are thanked for their hospitality, patience,
and all-around interest in the project. Dr. Beverly Chiarulli of IUP is thanked for her guidance,
suggestions, comments, and technical support throughout every step of the process, from data
collection to report preparation. We are especially grateful for her availability at a moment’s
notice to trouble-shoot problems that invariably arose during the project. Amanda Snyder and
Andrea Boon are thanked for rearranging their busy schedules to lend a hand in data collection.
Likewise, Allegheny Chapter of the Society for Pennsylvania Archaeology members Nina
Larsen, Bob Leidig, Don McGuirk, Ben Scharff, and Don Tanner volunteered their time and
aided in data collection. Any errors found herein are the sole responsibility of the authors.
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TABLE OF CONTENTS
Acknowledgments
i
Table of Contents
ii
List of Figures
iv
List of Tables
iv
Abstract
v
Introduction
1
Archaeological Prospection Theory
1
Magnetometry
2
Ground-Penetrating Radar
2
Archaeological Prospection of Prehistoric North America
3
Circular Villages of the Monongahela Tradition
6
A Brief Background of The Hatfield Site
10
Research Objectives
13
Methods
13
Survey Parameters
13
Magnetometry Survey
16
Magnetic Susceptibility
16
Magnetic Gradient
16
Ground-Penetrating Radar Survey
17
Data Integration
19
Results
19
Magnetometry Survey
20
Magnetic Susceptibility
20
Magnetic Gradient
21
ii
Ground-Penetrating Radar Survey
24
Interpretations
26
Conclusions
30
References Cited
31
iii
LIST OF FIGURES
Figure 1. General Location of the Hatfield Site
7
Figure 2. Typical Monongahela Tradition Village
9
Figure 3. Typical Monongahela Tradition Dwelling
9
Figure 4. Topographic Setting of the Hatfield Site
11
Figure 5. Stratigraphic Profile of the Hatfield Site
12
Figure 6. View of Grid 2, facing East
15
Figure 7. View of Grid 3, facing North
15
Figure 8. Seth Van Dam conducting Magnetic Gradiometry Survey in Grid 2
18
Figure 9. Amanda Snyder and Nina Larsen Performing GPR Survey in Grid 2
18
Figure 10. Results of the Magnetic Susceptibility Survey
21
Figure 11. Results of the Magnetic Gradient Survey in Grid 2
23
Figure 12. Results of the Magnetic Gradient Survey in Grid 3
23
Figure 13. Results of GPR Survey in Grid 2
25
Figure 14. Results of the Magnetic Gradient and GPR Surveys in Grid 2
27
Figure 15. Results of the Archaeological Prospection of the Hatfield Site
29
LIST OF FIGURES
Table 1. Spatial Information for Grid 2 and Grid 3
14
Table 2. Magnetic Susceptibility Anomaly Attributes
21
Table 3. Magnetic Gradient Anomaly Attributes
24
Table 4. GPR Anomaly Attributes
26
iv
ABSTRACT
An archaeological prospection survey was undertaken at the Hatfield site in November of
2011. The survey utilized magnetometry and ground-penetrating radar techniques to identify
subsurface anomalies that may represent cultural features. In total, 28 anomalies were identified
through magnetic susceptibility, magnetic gradient, and ground-penetrating radar methods.
Several of the anomalies resulted from modern activities at the site, including agricultural
plowing and excavations by the Allegheny Chapter. However, at least 10 of the anomalies
possibly represent prehistoric cultural remain of the Middle Monongahela component of the
Hatfield site. These anomalies comprise two pit features, six dwellings, and a house ring zone.
The size and arrangement of dwellings as well as the spatial layout of the house ring is consistent
with typical Monongahela Tradition villages. If the anomalies indeed represent a section of a
village, the Middle Monongahela village at the Hatfield site would encompass an estimated area
of 1.7 to 2.27 acres. In addition, a composite anomaly south of the Middle Monongahela
component may represent a second village at the site that covers an area of 0.25 acres.
v
INTRODUCTION
The following report describes an archaeological prospection survey undertaken at the
Hatfield site (36WH678) for fulfillment of course requirements in Specialized Methods in
Archaeology: Archaeological Geophysics (Anth 584). Specifically, it attempts to address the
nature of the subsurface archaeological record at the site through the use of geophysical methods,
including magnetometry and ground-penetrating radar (GPR). The field component of the
survey was undertaken during five non-sequential days in November of 2011 while data
processing, graphic design, and report production were completed in November and December
of 2011.
The Hatfield site was selected due to the senior author’s participation in ongoing
excavations there as part of public outreach efforts by the Allegheny Chapter of the Society for
Pennsylvania Archaeology. Given that, as Bercel and Espino (2010) point out, one of the
primary purposes of excavations at the Hatfield site was to garner public interest in the
archaeology of southwestern Pennsylvania through hands-on experience, the chapter decided to
excavate the site by hand. The chapter felt that there were a number of benefits to the slowerpaced excavations. First, it allows for the supervision and education of inexperienced
fieldworkers. Second, volunteers can be involved in most aspects of the fieldwork. Third, since
sites such as Hatfield are among the most complex sites to excavate, there is ample time to
properly document the findings without being overwhelmed. Finally, a smaller portion of the
site is impacted, thus preserving large areas for future research.
Conversely, one of the drawbacks of the chapter’s excavation procedures is that there is
limited opportunity to excavate large areas and expose settlement pattern information, including
the presence of a palisade, the layout of domestic structures, and the organization of activity
areas. As a result, archaeological prospection, also referred to as archaeological geophysics, was
proposed as a method to better define the subsurface record at the site and help identify
settlement patterns that would only be recognizable through extensive and expensive
excavations.
Archaeological Prospection Theory
The following section provides a general discussion of geophysical theory as it relates to
magnetometry and GPR.
1
Magnetometry. Magnetic methods are based upon localized disruptions in the earth’s
magnetic field (Hargrave 1999:12). Magnetic surveys measure the variation of the magnetic
fields of the earth and the effects of near-surface features that may be overlain upon it. In
archaeological applications, the surveys map the contrasting values of buried anthropogenic
activities generally characterized through magnetic susceptibility of geological features and
ferrous materials. Once the average magnetic susceptibility for an area is established, the
magnetic gradient acts as a filter to reduce the effects of background geological magnetic fields
and daily effects caused by the interaction between the magnetic fields of the Earth and its
atmosphere, allowing anthropogenic activity areas to be viewed as anomalies (Campana 2009).
Magnetic gradiometry is a passive detection method that measures the sum of remnant and all
forms of induced magnetism at a location, whether forms are natural or anthropogenic (Kvamme
and Ahler 2007:455-546). The range of the spatial frequencies in the collected data depends on
the depth of subsurface features, the susceptibility contrast between features and their
surroundings, and the height of the measuring instrument above the surface (Scollar 1990:490).
Ground-penetrating Radar (GPR). The foundations of GPR lie in electromagnetic (EM)
theory that is based upon the relationship of a material’s response to EM fields. GPR survey
method involves the transmission of high-frequency electromagnetic radar pulses into the ground
and measures the time that elapses between each transmission, reflection off a buried
discontinuity, and the reception back to the radar antenna at the surface (Conyers and Goodman
1997:23). The frequency of the radar wave transmitted controls the depth to which radar energy
can penetrate and the amount of definition that can be expected in the subsurface (Conyers and
Goodman 1997). Once the reflected signal is detected by the receiving antenna at the ground
surface within close proximity to the transmitter, this reflected signal can then be compared to
the original signal. The magnitude or amplitude, phase (negative or positive), and frequency of
the received signal offers additional information as to the nature of the materials below the
surface (Heimmer 1992:37). The software of the GPR unit has equations of macroscopic (or
average behavior) descriptions of how different electron, atoms, and molecules respond en masse
to the application of the EM field. These fluctuations from the macroscopic properties stand out
from the average macroscopic state (Jol 2009).
2
Archaeological Prospection of Prehistoric North America, a Brief Overview
The use of geophysical testing at archaeological sites in the United States was first
pioneered in 1946 by Richard J. C. Atkinson with the use of electrical resistivity (Scollar et al.
1990). Over the past 70 years, archaeologists have increasingly employed classical geophysical
methods to successfully enhance many cultural resource investigations (Heimmer 1992,
Weymouth, 1986). Not until recently however, has the use of geophysical testing become a
more standard survey technique. When employed, they provide non-destructive methods to
access information contained within significant sites. There are many different types of
geophysical methods for testing archaeological sites. These include ground penetrating radar
(GPR), magnetometry, electrical resistivity, magnetic susceptibility, and profiling to name a few.
Improved geophysical instruments and application methods, as well as new innovations in data
processing, have allowed for the study and measurement of earth-related physical contrasts with
extreme precision (Heimmer 1992). As a benefit of these advancements, minute or small
subsurface contrasts attributable to both historic and prehistoric site remains have a greater
chance of being detected using high resolution geophysical techniques without being destroyed
(Heimmer 1992). The following is a review of several cases in which archaeologists
successfully used geophysical testing methods to identify aspects of an archaeological site that
otherwise may have required full excavations. In each one of these cases, similar equipment was
used as in the archaeological prospection of the Hatfield site. By studying the results of these
cases, and how the data was processed, better interpretations of the Hatfield data can be offered.
Near-surface geophysical surveys were conducted at three locations at the Poverty Point
site (16WC5), Louisiana in 2001 (Britt et.al. 2002). Over the past 100 years, a number of
archaeological excavations have been carried out at Poverty Point, but none provided a clear
understanding of the nature, distribution, and density of archaeological features such as pits,
hearths, postholes, and other structural remains (Britt et.al. 2002). Due to this lack of
information, the geophysical survey was designed to emphasize high data density in three target
areas instead of covering large tracts of land at the site. The intention of the survey was to
collect data in a manner that would permit the detection of relatively small, very low contrast
subsurface features (Britt et. al. 2002). Mound E, West Sector and the Southwest Sector (rings
1-5) were selected as the target areas.
3
Methods employed during the survey included magnetic field gradiometry, electrical
resistivity, electro-magnetic in-phase/conductivity, and GPR. The following systems and
parameters were used: Geoscan Research FM-36 gradiometer with two fluxgate sensors;
Geoscan Research RM-15 resistence meter equipped with an MPX15 multiplexor and a PA5
Probe array; Geonics Ltd. EM-38 terrain conductivity meter; and a Sensor & Software, Inc.
Noggins GPR system with 250 and 1000 MHz antennas. All resistivity and gradiometer survey
data was processed using Geoplot 3.0 software and exported into Surfer 7.0 to produce image
maps. The GPR data was processed using GPR Slice, but was considered unusable due to a high
clay soil content that obscured the detection of anomalies. Furthermore, datasets recovered from
Mound E were considered unreliable due to the proximity of modern field road, the incidence of
recent metal artifacts, and the presence of an overhead electrical power transmission line (Britt
et. al. 2002).
Geophysical surveys at both the West and Southwest Sectors (rings 1-5) of the site did
however produce interesting and usable results. In the West Sector, geophysical surveys
indicated magnetic variability in the composition of the sediments, such as would be seen in
compositional differences between sands and clays. The results lent support to Jon Gibson’s
position that Crowley’s clay, which is exposed along Bayou Macon, was consistently mined and
used for construction by the people at Poverty Point (Britt et. al 2002). In addition, numerous
anomalies were detected in the West and the Southwest Sectors, respectively, and are suggestive
of midden deposits. Several targets were identified for exploration, though no work has been
conducted to investigate these anomalies.
In 2003, geophysical surveys were conducted at four prehistoric and historic fortified
earthlodge settlements located in the Middle Missouri River Basin of North and South Dakota
(Kvamme 2003). The surveys were conducted to provide interpretive details that could bolster
information provided to tourists for the then upcoming bicentennial of the Lewis and Clark
expedition. The surveys included large scale magnetic gradiometry and electrical resistivity
along with the use of soil conductivity measurements and GPR. The following systems and
parameters were used: Geoscan Research FM-36 fluxgate gradiometer with 4-8 samples per
meter in 0.5-1 m traverses; Geoscan Research RM-15 resistence meter in four parallel twin
configuration with 0.5 m probe separation; Geonics Ltd. EM-38 electromagnetic conductivity
4
quadrature phase data in vertical dipole mode with 1 x 0.5 m sampling; and GSSI SIR-2000 with
a 400 MHz antenna with 0.5 m traverse interval (Kvamme 2003).
The magnetic surveys proved to be the most consistent in providing subsurface details of
the village sites. At every site surveyed, the magnetic surveys revealed the presence of
fortifications, houses, hearths, and other features, such as storage and trash pits. Electrical
resistivity and GPR proved unsuccessful in defining subsurface anomalies. At one of the
villages, the Whistling Elk site, electrical resistivity, soil conductivity, and magnetometry were
successful in identifying an outer fortification ditch with five evenly-spaced bastions and 67
anomalies that represent houses (Kvamme 2003). The magnetometry survey further defined 34
of these houses as being burned, including what is known as the “Big House.” Ground-truthing
revealed that the “Big House” had indeed been burned. These results suggest that the Whistling
Elk prehistoric village had been sacked by another prehistoric group. At the historic village of
Mitu’tahaktos, the magnetic survey revealed household differences in the distribution of iron
artifacts, suggesting potential social and economic differentiation at the site (Kvamme 2003).
In November of 2008, geophysical investigations were conducted at the Late Prehistoric,
Monongahela Tradition Dividing Ridge site (36WM477) located in Westmoreland County,
Pennsylvania (Johnson 2008). Two methods were used for this investigation, magnetometry and
electrical resistance (Johnson 2008). For the purpose of this review, only the magnetometry
survey will be discussed since an electrical conductivity survey was not preformed at the
Hatfield site. The objective of the investigation at Dividing Ridge was to use geophysical
methods to map prehistoric features present at the site (Johnson 2008). The magnetometer
survey was conducted using a Geometrics G-858 Cesium magnetometer. Readings were taken at
a rate of 10 per second resulting in approximately 10 measurements for every meter (Johnson
2008). All magnetic data was collected along profile lines with a constant one-meter line
separation. All data maps were then produced using Surfer software.
The effect of recent human modification to the landscape can be seen in the data by the
presence of linear anomalies representing plow furrows. Even though the landscape had been
previously disturbed, numerous curvilinear magnetic features were observable in the maps. The
longest observable magnetic feature forms a large semi-circle at the western edge of the surveyed
area. Johnson (2008) interpreted this large feature as the palisade wall that once surrounded the
Dividing Ridge village site. Apart from this large palisade feature, numerous circular anomalies
5
measuring 8 to 12 m in diameter were identified. They are interpreted as possible houses based
on their size and distribution (Johnson 2008). Other anomalies were identified in the data, and
they may represent hearth, pit, or midden features. Although no ground-truthing of the
anomalies at the Dividing Ridge site have been conducted, the survey shows promise in
providing data related to settlement patterns at a Monongahela Tradition village.
The last example discusses a successful attempt in identifying subsurface archaeological
remains through GPR in an area with an abundance of clay soils, and it is offered because
subsoils at the Hatfield site have high clay content. Clay soils often will yield poor GPR results;
this is mostly due to clay having a high electrical conductivity. The survey was conducted at the
Riverfront Village, a prehistoric Mississippian site along the Savannah River in South Carolina
(Weaver 2006).
A GSSI SIR-3000 system with a 400 MHz antenna was used to collect data, and it was
processed to produce profiles in 3 ns slices. Processing revealed linear and circular features
within the 21-24 ns slice, which converted to depths of 40-45 cm below the ground surface. This
level laid below flood deposits that contained clayey soils. Anomalies that were identified were
interpreted as a palisade of the Mississippian village (Weaver 2006). Subsequent archaeological
excavations exposed a linear palisade 10 cm beneath the clay horizon. The reflection profiles
created in this area were so ambiguous that no usable interpretations could be made from them.
Even though this reflection data appeared ambiguous, the amplitude maps that were constructed
from all the combined reflection profiles provided useful data and maps.
Circular Villages of the Monongahela Tradition
The Hatfield site is a large, multi-component archaeological site located approximately
30 km (18.9 mi) south of Pittsburgh in North Strabane Township, Washington County,
Pennsylvania. One of the principal components represents a Late Prehistoric, Monongahela
Tradition village that was occupied during the Middle Monongahela period. The Monongahela
Tradition is an archaeological term used to define the people that inhabited the lower portion of
the Upper Ohio River Valley during the Late Prehistoric period, or between circa A.D. 1050 and
A.D. 1635. This region encompasses much of southwestern Pennsylvania and contiguous
portions of Maryland, Ohio, and West Virginia. Following Johnson’s (2001) chronology, the
Early Monongahela period dates to between A.D. 1050/1100 to A.D. 1250, the Middle
6
Figure 1. General Location of the Hatfield Site
7
Monongahela period dates between A.D. 1250 to A.D. 1580, and the Late Monongahela period
dates between A.D.1580 and A.D. 1635.
Villages are the most archaeologically visible Monongahela Tradition settlement. Of
over 400 Monongahela sites or components in which function has been determined, 74 percent
of these are identified as villages (Johnson 2001:68-69), and most are situated in upland settings
(Hasenstab and Johnson 2001; Johnson et al. 1989:1-9). Typical Monongahela villages consisted
of an outer fence or palisade with a concentric ring of houses surrounding an open area in the
center of the village that is commonly referred to as a plaza (Figure 2) (Johnson et al. 1989). At
some villages, especially during the Middle and Late Monongahela periods, there are more than
one palisade and more than one ring of houses. Palisades were usually constructed out of large
wooden posts, and often, a trench was excavated adjacent to the palisade. Soil from the trench
was added to the base of the palisade to provide structural support for the posts, especially at
villages that sat on shallow soils where bedrock precluded their deep placement. Within the
house ring, or domestic zone, a variety of features are typically found. They include domestic
structures, unattached storage facilities, fire pits, smudge pits, refuse pits, and burials, to name a
few. Plazas are usually devoid of domestic activity, perhaps because they were treated as
communal and/or ritual space. Some villages show evidence that a large hearth and/or central
post once stood at the center of the village (Means 2007).
Monongahela houses were usually circular or oval (Johnson et al. 1989:12-13), ranging
between three and ten meters in diameter. The interior of a typical house consisted of a central
hearth, support posts, and little else (Figure 3). Occasionally, burials are found underneath house
floors, but these are almost exclusively of young children or infants. It is estimated that
Monongahela houses may have been occupied by seven or eight individuals (Means 2006).
During the Middle Monongahela period, some of these domestic structures began to have pear or
horseshoe-shaped storage facilities attached to them (Hart 1995:46). With access through the
interior of the house, these appendages were used to store surplus agricultural goods among other
things. Over time, the number of houses with appendages increased (Hart et al. 2005:352), as
did the number of appendages that appear on households.
Later in time, specialized structures that may have complex social implications appear at
Monongahela villages, and mostly within plazas or near the center of the village (Anderson
2002). One such structure is referred to as a petal house because of its distinctive lay-out.
8
Figure 2. Typical Monongahela Tradition Village (Courtesy of the PHMC)
Figure 3. Typical Monongahela Tradition Dwelling (George 1997)
9
Occurring within at least three Late Monongahela period villages, petal houses exhibit multiple
appendages, from as few as 11 to as many as 24 (Anderson 2002:123-124). Interpretations of
these structures have ranged from communal storage, to sweat baths or council houses, to
communal ritual space (Anderson 2002:125; Hart 1995:50; Herbstritt 1984, 2003:31). The other
type of specialized structure is recognized because of its mortuary function. Known as charnel
houses, these structures were used primarily for the burial of adults (Anderson 2002:125-127).
They are identified at four terminal Middle Monongahela and Late Monongahela villages, with
two of these possibly representing early progenitors of the type (Johnson 2001:73). These
structures suggest that certain individuals were treated, at least in death, differently than other
members of the village (Anderson 2002:127).
A Brief Background of the Hatfield Site
The Hatfield site is situated on a long peninsular hill spur oriented north to south at an
elevation of 360 m above sea level (Figure 4). This hill spur is flanked by springs on both the
eastern and western sides as it gently slopes down to a small unnamed tributary of Little
Chartiers Creek at its southern tip. Little Chartiers Creek joins the larger Chartiers Creek about
seven km northeast of the site. Chartiers Creek is a north-flowing, major tributary of the Ohio
River that is more or less paralleled by the Monongahela River to the east and a portion of
Raccoon Creek to the west. Cross-cutting Allegheny and Washington Counties, the stream
drains approximately an area of 446 square-kilometers (277 square-miles). The headwaters of
the creek originate just south of the City of Washington in south-central Washington County.
The creek empties about 50 km (31 miles) from its origin into the Ohio River near the Borough
of McKees Rocks, just upriver from Pittsburgh.
The site is situated within the Pittsburgh Low Plateau Section of the Appalachian
Plateaus Physiographic Province, which is characterized by narrow summits, narrow stream
bottoms, and steep linear valley slopes. This highly dissected terrain results from the erosion of
flat lying bedrock that belongs to the Pennsylvanian aged Washington Formation, and is
composed of cyclic sequences of sandstone, shale, limestone, and coal (Wagner et al. 1975). The
base of the Washington Formation is defined by the Washington coal. Overlying the coal are
three limestone beds (lower, middle, and upper) that are readily identifiable on many hilltops
across Washington County. The weathering of these various beds provides the parent material
from which the soils on the Hatfield site have formed. Soils
10
Figure 4. Topographic Setting of the Hatfield Site
underlying the site are mapped as Guernsey silt loam on 3 to 8% slopes (NRCS 2007a), and are
excellent for growing staple crops such as corn and wheat (NRCS 2007b).
A geomorphologic study of the site revealed that a pronounced plow zone with a depth
ranging between 23 and 26 cm (9.06-10.24 in) was clearly shown by the unusually dark humic
soils of the Ap horizon (Figure 5) (Fritz and Valko 2007). It is possible that midden deposits
resulting from prehistoric occupation of the site have enhanced the darkness of the Ap horizon.
Based on the auger probes, the artifact density within the plow zone was relatively high, with
two artifacts recovered per 1.2 liters of soil. The bottom of the Ap horizon is sharply contrasted
against the lighter and more yellow Bt horizons. Formation of these Bt horizons is the result of
in situ weathering of bedrock over thousands of years. It was determined that artifacts were
11
unlikely to be found within the Bt horizons except where human features, bioturbation, or any
other types of disturbances have intruded into the Bt horizons.
Figure 5. Stratigraphic Profile of the Hatfield Site
In total, seven features, over 150 postmolds, and more than 20,000 artifacts have been
documented by the Allegheny Chapter’s excavations (Bercel and Espino 2010). The field work
has exposed a 40 m2 (430.56 ft2) area of contiguous units arranged more or less linearly along the
eastern section of the village. Features include two refuse pits, two fire pits, two post-enclosed
storage pits, and a burial, all of which are found within the domestic zone, or house ring, of
typical Monongahela villages. However, the limited areal extent of the excavations has
12
precluded any positive identification of domestic structures and other large-scale village features.
A fragment of hickory nut (Caryan sp.) from Feature 2, a refuse pit, produced an Accelerator
Mass Spectrometry (AMS) radiocarbon date of 545±15 radiocarbon years before the present
(rcybp) (ISGS-A1409; Bercel and Espino 2010). This date has a one sigma calibration of A.D.
1399-1419 and a two-sigma calibration of A.D. 1326-1425.
Research Objectives
Due to the limited extent of the Allegheny Chapter’s excavation, little can be said of the
settlement patterns at the Hatfield site. Therefore, the primary objective of the archaeological
prospection survey is to identify subsurface anthropogenic features that may help develop
interpretations about the spatial structure of the village. Similarly, the project is intended to
identify areas of archaeological interest as the Allegheny Chapter continues research at the site.
Prior to the survey, a number of research questions were developed to help guide data
collection: (1) Can overall boundaries at the Monongahela component be defined using
geophysical methods?; (2) Does the village contain a defensive stockade and associated trench?;
and (3) Can the domestic zone of the village be identified, and if so, can activity areas and
domestic structures be identified and measured? Delineating the spatial extent of the village
within the surveyed area is integral to understanding settlement patterns. With better-defined
boundaries, the size of the village may be extrapolated onto the neighboring property, and with
an extrapolated size, estimates of the number of houses and overall population size can be
developed. Similarly, identifying the stockade will help to more accurately define the aerial
extent of the village. Finally, identifying and interpreting anomalies within the domestic zone
may reveal patterns associated with the organization of the village, i.e. whether there are one or
two rings of houses, clustering of houses, and areas of specialized activities.
METHODS
The following section describes the data collection and processing methods and systems
used during the archaeological prospection of the Hatfield site.
Survey Parameters
Archaeological prospection of the Hatfield site commenced with the establishment of a
large grid (Grid 1) across the eastern section of the hill spur on which the site is situated. The
purpose of this grid was to provide an area to systematically collect magnetic susceptibility data
over most of the site. A shapefile of points spaced five meters apart was created using
13
AUTOCAD 2004 and ESRI’s ArcGIS v. 10.0, the shapefile was then uploaded into a Trimble
TSC2 data collector through the use of Trimble’s GPS Path Finder Office 3.0 for field use. Grid
1 measured 35 x 265 m (114.83 x 869.42 ft) for an area of 9,275 m2 (2.29 acres).
Subsequently, two areas were selected for magnetic gradient and GPR sweeps based on
their proximity to the Allegheny Chapter’s excavations where cultural features had been
identified. The survey areas were established through spatial control points belonging to the
chapter’s existing localized excavation grid. The excavation grid originally had been created and
aligned to magnetic north using a Berger transit (Fritz and Valko 2007). For the purpose of the
geophysical survey and future work at the site, the excavation grid was updated with a Nikon
DTM-520 (with 3” angle accuracy, +/- [3mm+2ppm]) and a Trimble TSC2 Data Collector (256
MB), thereby establishing sub-millimeter accuracy for regions within the site. Once the
excavation grid was updated, the two geophysical survey grids (Grid 2 and Grid 3) were
established, and the corners of each grid were located using a Trimble R8 GNSS Global
Positioning Systems (GPS) unit (horizontal accuracy 3mm+0.4ppm RMS, vertical accuracy
3.5mm + 0.4ppm RMS). This process established real world coordinates for the project area
using the Universal Transverse Mercator (UTM) projection and a World Geodetic System
(WGS) 1984 datum. Grid 2 measured 20 x 30 m (65.62 x 98.43 ft) (Figure 6) while Grid 3
measured 10 x 40 m (32.82 x 131.23 ft) (Figure 7). Table 1 contains spatial information for both
these grids.
Table 1. Spatial Information for Grid 2 and Grid 3
Point #'s Desc
Grid 2
1004
NW
1005
SW
1006
SE
1007
NE
Grid 3
1010
1011
1012
1013
NW
NE
SE
SW
Local Northing/Easting UTM Zone 19N Coordinates
Northing
1010N,1000E
4452264.024
990N,1000E
4452244.447
990N,1030E
4452250.032
1010N,1030E
4452269.679
990N,1002E
990N,1012E
950N,1012E
950N,1002E
4452244.788
4452246.66
4452207.376
4452205.494
14
Easting
570877.515
570881.254
570910.756
570907.024
Elevation
321.778
321.015
317.619
318.06
570883.224
570893.069
570900.438
570890.679
320.927
319.815
318.896
320.044
Figure 6. View of Grid 2, facing east
Figure 7. View of Grid 3, facing north.
15
Magnetometry Survey
As noted earlier, magnetic surveys measure the variation of the magnetic fields of the
earth and the effects of near-surface features that may be overlain upon it. In archaeological
applications, the surveys map the contrasting values of buried anthropogenic activities generally
characterized through magnetic susceptibility of geological features and ferrous materials. Once
the average magnetic susceptibility for an area is established, the magnetic gradient acts as a
filter to reduce the effects of background geological magnetic fields and daily effects caused by
the interaction between the magnetic fields of the Earth and its atmosphere, allowing
anthropogenic activity areas to be viewed as anomalies (Campana 2009).
Magnetic Susceptibility. The magnetic susceptibility survey was conducted in Grid 1 on
November 13 and 15, 2011. It employed a MS2F probe with a 15mm diameter tip that
penetrates to a depth of 15-20 mm (Bartington OM0408, Issue 42). The Trimble TSC2 data
collector was used to locate 417 pre-designated grid points where measurements were taken.
Probe readings were recorded in the field and transferred into a Microsoft Excel file containing
spatial information for each point. The Excel file was used to create a grid file in Golden
software’s Surfer 9, where processing and spatial analyses were conducted. The grid file was
converted into a contour map of the dataset. It should be noted that Surfer 9 created a contour
map that extrapolated a larger surface area than what was actually collected in the field, possibly
because the data points were collected on a grid oriented to magnetic north and therefore tilted
from the true north layout used by Surfer. In other words, large areas that were not surveyed
were given values based on statistical extrapolations from known points. The farther away the
extrapolated surface was from known points, the less accurate it appeared.
Magnetic Gradient. A magnetic gradient survey was conducted within Grids 2 and 3 on
November 13, 2011 through the use of a FM 256 Fluxgate Gradiometer data processing unit
(Figure 8). Specifications for the equipment include sensor separation of 500mm, operation field
range of +/- 100nT, analogue ranges of +/- 5, 10, 20, 40, 80, 160, 320, 640 nT, digital ranges of
+/- 20000, 2000, & 200 nT, digital display resolution of 10, 1, 0.1 nT and a response time of 20,
40, 120 mS (GeoScan Research 2005). Data from Grid 2 was collected at a sampling interval of
25 cm (9.84 in) along 50 cm (19.69 in) spaced transects traveling along the east-west axis. Data
from Grid 3 was collected at a sampling interval of 12.5 cm (4.92) along 50 cm (19.69 in) spaced
16
transects traveling along the north-south axis. Both grids were collected in a zigzag fashion
(Clay 2006).
Data analysis was completed with Geoplot software produced by Geoscan Research. The
following steps were followed in the processing of data from Grid 2: (1) clipping of seven areas
of extremely low reading, (2) Zero Mean Traverse, (3) De-stagger of the grid, (4) Interpolation
of Y & X axis – Sin X/X, x2, and (5) Low Pass Filter, X=1,Y=1, Weight: Uniform. Grid 3 was
processed as follows: (1) Clipping of four areas of extremely low readings and two areas of
extremely high readings, (2) Despike of the entire grid, (3) Zero Mean Traverse, (4) Interpolation
of Y & X axis– Sin X/X, x2, and (5) Low Pass Filter, X=1,Y=1, Weight: Uniform. Anomalies
that are identified will be classified according to magnetic gradient codes developed by Burks
(2009).
Ground-penetrating Radar Survey (GPR)
The foundations of GPR lie in electromagnetic (EM) theory, which is based upon the
relationship of a material’s response to EM fields. For GPR, the electrical and magnetic
properties are of importance. The software of the GPR unit has equations of macroscopic (or
average behavior) descriptions of how different electron, atoms, and molecules respond en masse
to the application of the EM field. These fluctuations from the macroscopic properties stand out
from the average macroscopic state (Jol 2009).
This survey was conducted using a GSSI SIR-3000 GPR model with a 400 MHz antenna.
It can penetrate into the ground to a depth of 0-4 meters (0-12 feet) (Figure 9). The equipment
specifications include Scan Rate Examples of 8 bit 220 scans per second at 256 samples per
scan, 16 bit 120 scans per second at 512 samples per scan, a Number of Samples per Scan of
256, 512, 1024, 2048, 4096, or 8192, Time Range of 0-8,000 nanoseconds full scale, userselectable, a Gain of Manual or Automatic, 1-5 gain points (-20 to +80 dB), Vertical Filters:
Low Pass and High Pass IIR and FIR, and Horizontal filters: Stacking, Background Removal
(GSSI 2009).
The GPR survey within both grids was conducted via north-to-south zigzag sweeps
spaced at 25 cm (9.14 in) intervals along the Y-axis (Conyers 2004). Datasets were collected
along parallel transects separated by 25 cm (9.84 in) intervals (Conyers 2004). The collection of
the data in Grid 2 occurred over two nonconsecutive days (November 5 and 8, 2011). Transect
17
Figure 8. Seth Van Dam conducting Magnetic gradiometry survey in Grid 2
Figure 9. Amanda Snyder and Nina Larsen doing GPR survey of Grid 2
18
0.0-17.25 m were collected on the first day and transects 17.5-30.0 m were collected on the
second day. The collection of the data from Grid 3 occurred on November 13, 2011.
GPR Slice v7.0 was used to process the datasets from both grids (GPR Slice 2011).
Settings for Grid 2 included the number of samples per scan as 512 with a sample start of 58 and
a sample end of 512. Twenty slices were created with sample thickness of 4.4 ns and a sample 0
ns of 58. Since the datasets were gathered on separate days, the combined dataset’s slices
required a mosaic correction of increased batch gains to make the two dataset represent equal
reflective values. Once corrected, the slices were further processed through a 3x3 Low Pass
Filter. Settings for Grid 3 included the number of samples per scan as 512 with a sample start of
64 and a sample end of 512. Twenty slices were created with sample thickness of 4.39 ns and a
sample 0 ns of 64. The dataset’s slices were further processed through a 3x3 Low Pass Filter.
Data Integration
Once the data from the magnetic susceptibility, magnetic gradient, and GPR were
processed and analyzed, the results were integrated into a Geographic Information System (GIS)
via ArcGIS v10.0. The datasets were combined by georeferencing select Joint Photographic
Experts Group (jpeg) files and layering them with varying transparencies in order to locate
anomalies that are represented in all three geophysical datasets. Shapefiles of the Allegheny
Chapter’s excavations were also combined to provide contrasting views of real-world cultural
features and geophysical anomalies that may represent areas of anthropogenic activities (Bercel
and Espino 2010).
RESULTS
Integration of the datasets into a geographic information system allowed for a layered
visualization of the data that greatly enhanced the interpretation of the results. Both the
magnetometry and GPR survey data strongly suggests that these particular archaeological
prospection methods are very effective in defining subsurface anomalies that may represent
cultural zones and smaller cultural features. Both methods provide complimentary results that,
together, begin to shed light on the settlement patterns and village organization of the Hatfield
site.
In total, 28 anomalies were identified through archaeological prospection. Anomalies are
labeled sequentially according to grid number. Grid 1 contained eight anomalies labeled G1-1
through G1-8, Grid 2 contained 14 anomalies labeled G2-1 through G2-14, and Grid 3 contained
six anomalies labeled G3-1 through G3-6. The results of the surveys are described below.
19
Magnetometry Survey
Magnetic Susceptibility (Figure 10). The magnetic susceptibility portion of survey
proved highly efficient in collecting data from a large area in a relatively short time.
Measurements were recorded at 417 points spaced at five meter intervals within Grid 1. As
mentioned earlier in the Methods section, Surfer 9 created a contour map representing a larger
surface area than what was actually collected. In interpreting features, special care was taken to
not give too much weight to possible anomalies in the areas if the map that were extrapolated.
Initially, the magnetic susceptibility data revealed an arcing pattern (G1-1) trending eastto-west that was dominated by relatively low magnetic values ranging between -10 to 60 nT.
The portion of the anomaly that was recorded during the survey measured 80 to 90 m north-south
and 55-65 m e-w. The ellipsoid has an extrapolated area ranging between 6,908 and 9,185
square-meters (1.71-2.27 acres). There was an area of higher magnetic value that peaked near 90
nT adjacent to the arc. When this area was examined, it became apparent that measurements
were affected by the Allegheny Chapter’s staging area, where screens, wheel burrows, shovels,
and other metal objects are stored. Since the resulting peak may have obscured true anomalies,
seven data points in that portion of Grid 1 were removed from the analysis and a modified
contour map was created. The modified contour map retained the arcing pattern of low magnetic
values seen in the earlier version. However, new anomalies appeared that indeed were masked
by the high magnetic values associated with the staging area. These anomalies (G1-3, 4, 5, 6,
and 7) appeared as small circular areas of higher values that ranged between 50 and 70 nT. They
measured between 5.7 and 29.4 square-meters (61.3-316.5 square-feet).
An interesting area of anomalies (G1-7) was identified approximately 90 m (295.28 ft)
south-southeast of the Allegheny Chapter’s excavations. Similar to the pattern noted above, the
anomalies consist of a ring of low to moderate magnetic values (50-80 nT) accentuated by
smaller areas of higher values (up to 110 nT). The center of the ring displayed relatively low
magnetism (-10-40 nT). The area encompassed by these anomalies measures approximately
1,107 square-meters (0.25 acres). Finally, large areas (G1-2) of high magnetic value were
measured in the southern portion of Grid 1. Values here peaked at 170 nT. The cause of these
anomalies is uncertain, though they are unlikely to represent archaeological remains since this
20
Figure 10. Results of the Magnetic Susceptibility Survey
portion of the grid is steeply sloped. The definitions and details of anomalies identified during
the magnetic susceptibility survey are available in Table 2.
Table 2. Magnetic Susceptibility Anomaly Attributes
Grid 1
G1-1
G1-2
G1-3
G1-4
G1-5
G1-6
G1-8
.
Northing
N/A
4452129mN
4452293mN
4452277mN
4452260mN
4452236mN
4452173mN
Easting
N/A
570945.9mE
570879.9mE
570889.5mE
570896.3mE
570893.4mE
570907.2mE
Readings/Areas
60nT, -10nT
147nT
55nT, 13.74sq m
55nT, 29.43sq m
56nT, 18.65sq m
46nT, 5.7sq m
50-110 nT, 1.107 sq m
Comments
Probable House Ring
Unknown magnetic Anomaly
Probable Domestic Structures
Probable Domestic Structures
Probable Domestic Structures
Probable Domestic Structures
Possible Second Village Site
Magnetic Gradient (Figures 11 and 12). Map surfaces covered in full, grid-length linear
features oriented north-to-south is immediately apparent from the magnetic gradient data. These
linear features are present in both grids, and are consistent with agricultural plow scars. The
presence and similar orientation of plow scars have been noted during excavations of the
21
Hatfield site (Bercel and Espino 2010). Additional agricultural disturbances are seen in Grid 3,
where a series of mixed positive and negative readings were recorded along the western edge of
the grid.
Likewise, a series of mono-polar positive and mono-polar negative anomalies are
aligned linearly along the 1010E transect of Grid 3. Four of these are mono-polar positive
anomalies while the fifth one is a mono-polar negative anomaly. The sources of both sets of
anomalies are likely agricultural furrows noticed during data collection. In addition, two
anomalies in Grid 2 were influenced by recent activity at the site. One is a large mono-polar
negative anomaly located around the existing excavation trench, and likely caused by a large
number of 25.4 cm (10 in) iron spikes demarcating the corners of excavation units. The other
represents a multi-polar complex anomaly whose source is a 30.5 cm (12 in) iron spike at the
location of one the excavation’s spatial control points. Efforts to buffer these areas by a distance
of a meter in all directions were insufficient in reducing the magnetic noise caused by the ferrous
metal.
Despite these modern disturbances, the magnetic gradient survey proved relatively
effective in revealing a number of subsurface anomalies within Grid 2. In total, nine magnetic
anomalies were identified. None of the anomalies produced readings higher than 40 nT,
suggesting an overall lack of historic iron in the survey grid (Burks 2009). Three (G2-3, 6, and
8) of the observable anomalies are classified as mono-polar positive and two (G2-4 and 7) as
dipolar simple. Mono-polar positive and dipolar simple anomalies are typically classified as
undefined feature types due to difficulties in discerning their true polar nature, i.e. mono-polar
positive or only a portion of a dipolar simple anomaly (Burks 2009). Prehistoric features that
may produce these types of anomalies include pits as well as some hearths and earth ovens. One
large positive anomaly (G2-9) was detected near the southwestern edge of the grid. Initially, this
anomaly was observed as three monopoles, or a multi-monopositive anomaly, though by the end
of data processing, the anomalies blended into one mass. Though rare to detect, such anomalies
represent clusters of positive mono-poles arranged in linear or arcing patterns likely representing
postmolds (Burks 2009).
Finally, one anomaly (G2-2) was identified as a dipolar complex
anomaly due to the presence of three negative peaks surrounding a large positive peak. This type
of anomaly is often associated with burned areas or prehistoric structure floors (Burks 2009).
The definitions and details of anomalies identified during the magnetic gradient survey are
available in Table 3.
22
Figure 11. Results of the Magnetic Gradient Survey in Grid 2
Figure 12. Results of the Magnetic Gradient Survey in Grid 3
23
Table 3. Magnetic Gradient Anomaly Attributes
Anomaly
Northing
Easting
Readings (High,Low)
G2-1
G2-2
G2-3
G2-4
G2-5
G2-6
G2-7
G2-8
G2-9
G3-1
G3-2
G3-3
G3-4
G3-5
G3-6
1005
1008.875
1009.625
1007.375
1000
996.125
994.375
995.625
991.375
970
983.875
979.875
975.875
963.125
955.125
1005
1018
1023.06
1029.81
1020
1006.43
1010.43
1029.81
1005.06
1022
1009.9
1010.05
1010.03
1010.59
1010.03
Dummy
20.78nT, -7.33nT
5.52nT, 1.89nT
16.96nT, -9.21nT
Dummy
4.97nT, -0.28nT
10.70nT, -11.16nT
4.11nT, -0.69nT
19.52nT, -0.43nT
18.46nT, -15.54nT
4.76nT, -0.86nT
11.73nT, -0.65nT
6.54nT, -1.41nT
2.08nT, -12.38nT
6.51nT, -2.19nT
Comments
Caused by 10" spikes from previous excavation grid
Dipolar Complex - Probable Hearth
Mono-Polar Positive
Dipolar Simple
Caused by a 1" Rebar set as a local datum point
Mono-Polar Positive
Dipolar Simple – Probable Pit Feature
Mono-Polar Positive
Multi-Monopolar Positive
Caused by agrilcultural furrows
Mono-Polar Positive
Mono-Polar Positive
Mono-Polar Positive
Mono-Polar Negative
Mono-Polar Positive
Ground-penetrating Radar Survey (Figures 13 and 14)
Six anomalies were identified during the GPR survey of Grid 2 and none were recognized
completely in Grid 3. This includes an area (G2-10) of high reflection in the northwest section
of Grid 2 where test units had been excavated by the Allegheny Chapter. A small anomaly (G215) of high reflection values is located at 1000N 1020E. This anomaly was caused by an
existing spatial control point for the chapter excavations. Another high reflection anomaly (G212) is situated on the western edge of the grid south of the chapter’s excavation area. The cause
of this anomaly is uncertain.
Two anomalies that produced similar moderate reflection values are also present in Grid
2. One (G2-13) is circular in shape located in the south-central portion of the grid with its center
point located at 995N 1020E. This anomaly has an area of approximately 78.50 m2 (844.97 ft2)
and reflective values ranging between 0.25 to 1 ns. The location of this anomaly corresponds to
the location of anomaly G1-5 identified during the magnetic susceptibility survey. The second
anomaly (G2-11) has a roughly circular shape with an area of 63.59 m2 (684.48 ft2). It is located
due north of G2-13 near the northern edge of the grid, with its center point located at 1007N
1020E. It appears as if the anomaly extends northwards beyond the survey area. The anomaly
has reflective values that range between 0 and 1 ns. While the boundaries of this anomaly were
not as well defined, it contains a few more areas of high reflection than G2-13. Interestingly, the
24
Figure 13. Results of GPR Survey in Grid 2
Dipolar Complex anomaly identified during the magnetic gradient survey is located near the
center of G2-11. Both G2-11 and G2-13 were identified in the same slice, and their parabolas
occurred at similar depths of 28-36 cm (11.02-14.17 in) below the antenna. While zero time was
not calculated, and therefore the exact depth of the anomalies is uncertain, this range of depth
encompasses the plowzone-subsurface interface at this portion of the site (Bercel and Espino
2010). A third anomaly (G2-14) is identified as a partial arc of mainly low reflection values (00.75 ns). It is located along the southern edge of the grid at 990N 1009.5E and extends slightly
into Grid 3. The definitions and details of anomalies identified during the GPR survey are
available in Table 4.
25
Table 4. GPR Anomaly Attributes
Anomaly
G2-10
G2-11
G2-12
G2-13
G2-14
G2-15
Northing
1008
1007
995
995
990
1000
Easting
1000.5
1020
1001
1020
1009.5
1020
Readings
0.5-1 ns
1.0-0.0ns
0-1 ns
0.25-1 ns
0-0.75 ns
N/A
Comments
Previous Excavation Trench
Probable Dwelling Feature
Unknown Anomaly
Probable Dwelling Feature
Possible Dwelling Feature
Datum Spike
INTERPRETATIONS
The results of the archaeological prospection of the Hatfield site offer tantalizing clues as
to the nature of its subsurface archaeological deposits. It should be noted, however, that the
results remain highly hypothetical until they can be verified through excavations. To understand
what the results may mean, this discussion will begin with the small scale datasets recovered in
Grid 2 through magnetic gradient and GPR surveys and end with the large scale Grid 1 magnetic
susceptibility data.
The incidence of a dipolar complex anomaly (G2-2) identified by the magnetic gradient
survey within the boundaries of a roughly circular anomaly (G-2-11) recorded during the GPR
survey suggests that the geophysical techniques possibly identified a domestic structure (Figure
14). Hearth features often produce dipolar complex anomalies (Burks 2009), and its location
suggests that it may represent a central hearth within the domestic structure. The second circular
anomaly (G2-13) identified through GPR may also represent a domestic structure. This anomaly
appears better defined, and it is located four meters due south of the other possible structure. It
should be noted that the sizes of these anomalies (63.59 m2 [684.48 ft2] for G2-11 and 78.5 m2
[844.97 ft2 for G2-13) exceed the higher end of Monongahela mean dwelling size range in the
Somerset Plateau, where spatial analyses of Monongahela villages has been undertaken more
systematically (Means 2006). However, large houses in excess of 65 m2 (699.65 ft2) have been
recorded at the McJunkin (36AL17), Portman (36AL40), and Household (36WM61) sites (Buker
1993; George 1978, and George et al. 1990), including a maximum of 83.3 m2 (896.63 ft2) at
McJunkin. Moreover, plow disturbance of materials with high reflective values at Hatfield may
be accentuating their actual size.
Interestingly, the location of G2-13 corresponds to anomaly G1-5 measured by the
magnetic susceptibility survey. In analyzing the magnetic susceptibility data, the location of the
possible structure and central hearth (G2-11 and G2-5, respectively) returned low magnetic
26
Figure 14. Results of the Magnetic Gradient and GPR Surveys in Grid 2 (note: GPR layer has a
60% transparency)
27
values during the susceptibility survey. This situation seemed at odds with the magnetic
gradient survey since the latter measured high magnetism associated with the central
hearth/dipolar complex feature/anomaly. Closer examination of the magnetic susceptibility data
points showed that none of the points were recorded within the possible structure. The anomaly,
as it was identified by the magnetic gradient and GPR, fell within the gaps of the magnetic
susceptibility grid. Based on the G2-13 and G1-5 correlation, the arcing pattern of anomalies
(G1-3 through G1-7) also identified through magnetic susceptibility are inferred to represent
domestic structures as well. As noted earlier, these anomalies displayed similar magnetic
signatures and sizes.
The results of the survey suggest that six possible dwellings were identified through
archaeological prospection of the Hatfield site (Figure 15). These structures are aligned in an
arc, and they fall within a larger arcing pattern of low magnetic values. This pattern is
suggestive of the typical house ring of Monongahela villages (Means 2007). The geophysical
data provides rough boundaries for the Middle Monongahela component, but unfortunately the
survey failed in identifying the palisade. North to south, the village has a possible diameter
between 80 and 90 meters. The eastern boundary of the site falls within 35 to 45 meters of the
site’s datum. However, the east to west diameter is uncertain since the west boundary is outside
of the surveyed area. An extrapolation of the house ring into the un-surveyed portion of the
Hatfield site suggests that the ellipsoid village covers an area of between 6,908 and 9,185 m2
(1.71-2.27 acres). Though Monongahela village sizes vary greatly, the size of the Hatfield
Middle Monongahela village component is consistent with the range of Monongahela village
sizes (Hart et al. 2005). Villages that approximate the size of Hatfield include Ashmore Farm
(36WH675), Saddle (46MR95), McJunkin (36AL17), Campbell Farm (36FA26), Peck 2-2
(36SO8), and Foley Farm (36GR52). Even larger villages include Sony (36WM151), Johnston
(36IN2), Fort Hill 2 (36SO2), and Hughes Farm (46OH9).
Finally, it was mentioned during the results of the magnetic susceptibility survey that a
smaller arcing pattern that mimics the pattern described above was identified about 90 m (295.28
ft) south of the Allegheny Chapter’s excavation area. Identified as G1-7, this composite anomaly
has a size of 1,011.7 m2 (0.25 acres). Surface-collected artifacts from the Hatfield site include a
number of ceramics attributed to the Early Monongahela period (William C. Johnson, personal
communication 2009). The provenience of these artifacts in relation to the areas currently being
28
Figure 15. Results of the Archaeological Prospection of the Hatfield Site
29
excavated is uncertain, but no Early Monongahela period ceramics have been identified during
the course of the fieldwork (Bercel and Espino 2010). Anomaly G1-7 may represent a smaller
and older village at the site. A similar situation occurs at the Consol site (36WM100), where a
small, circular Early Monongahela village is situated a short distance from the much larger
Middle and Late Monongahela village component. However, since no excavations have taken
place at that portion of the Hatfield site, there is little evidence suggesting that cultural remains
may be found at that location. The above is only offered as an interesting pattern that is worth
investigating.
CONCLUSIONS
An archaeological prospection survey was undertaken at the Hatfield site in November of
2011. The survey utilized magnetometry and ground-penetrating radar techniques to identify
subsurface anomalies that may represent cultural features. In total, 28 anomalies were identified
through magnetic susceptibility, magnetic gradient, and ground-penetrating radar methods.
Several of the anomalies resulted from modern activities at the site, including agricultural
plowing and excavations by the Allegheny Chapter. However, at least 10 of the anomalies
possibly represent prehistoric cultural remains of the Middle Monongahela component of the
Hatfield site. These anomalies comprise two pit features, six dwellings, and a house ring zone.
The size and arrangement of dwellings as well as the spatial layout of the house ring is consistent
with typical Monongahela Tradition villages. If the anomalies indeed represent a section of a
village, the Middle Monongahela village at the Hatfield site would encompass an estimated area
of 1.7 to 2.27 acres. In addition, a composite anomaly 90 m (295.28 ft) south of the Middle
Monongahela component may represent a second village at the site that covers an area of 0.25
acres.
The application of geophysical techniques at archaeological sites is still in its infancy,
and they should not be used, by any means, as the final word of an investigation. Through their
continued excavations at the Hatfield site, the Allegheny Chapter will attempt to verify the
findings of the archaeological prospection of the Hatfield site. Only then could the results be
properly used to discuss the nature of subsurface archaeological deposits and intra-site settlement
patterns at the site. Nevertheless, the results of the archaeological prospection at the Hatfield site
offer solid data through which future excavations can be directed to begin to understand the
30
organization of this occupation and the social and cultural factors that influenced the formation
and use of space within this Middle Monongahela village.
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