SW Michigan Earthwork - Summary

Laura Sherrod - 2010

Geophysical Survey Goals:

Locate previous excavations within the archaeological grid
Identify potential burn pit features
Determine possible entry ways through the the apparently continuous earthwork structure

Site History:

Earthwork constructed between 1400 and 1650 AD
Located on bluff above old flood plain of the Muskegon River
1937 excavations by Georgy Quimby
2006 excavations by Grand Valley State University
2010 geophysical surveys

Stratigraphy and Artifacts:

Sandy soils ideal for GPR surveys
Tree roots create moderate noise for GPR
Four Late Archaic Dustin/Lamoka points
One Early Woodland Kramer point
Numerous ceramics and lithics diagnostic of Late Woodland/Late Prehistoric
Two burn pit features (radiocarbon date between 1400 and 1650 AD)
Worked native copper recovered from Feature 1

Geophysical Surveys:

Gentle topography with leaf cover and numerous small trees
400MHz GSSI SIR 3000 GPR system
Geometrics G-858 Magnetometer/Gradiometer
42m x 44m grid
Bidirectional survey lines with a spacing of 1.0m

Magnetometer Data:

Background magnetic field increases to the southeast
Feature 2 was not completely excavated in 2006 and is observed as a magnetic anomaly
An arc of magnetic anomalies similar to that found at feature 2 is traced by the bold dashed line which ends at feature 2 in the east
Additional anomalous responses of unknown origin are observed on the southern edge of the survey area (two dashed lines)
Pit Data:
1937 excavation pits and 2006 reconstruction efforts create large anomalies on the north edge
2006 excavations give indistinct geophysical responses
Modern charcoal deposits south of A create noise in the magnetic results
Positive shovel test pits indicate locations of artifact removal prior to the 2010 geophysical surveys

GPR Data:

Three dimensional GPR image illustrates the circular earthwork structure at shallow depth
Comparison of GPR and magnetic maps shows correlation of anomalies at various depths (example - dashed circle)
Two dimensional GPR profiles show many hyperbolic reflections within the depth range of artifact recovery (approximately 0.5m)
GPR results correlate to magnetic responses with subsurface disturbance visible at the locations of several magnetic anomalies


Previous excavation units within the archaeological grid were identified as magnetic and GPR anomalies
Several potential burn pit features were identified through both magnetic and GPR methods.
The magnetic anomalies on the southern edge of the survey area may relate to remnants of an entry way
Published in Michigan Academician, December 2013     
Earthworks Page Archaeology and Geophysics Ground Penetrating Radar
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