James Stuby, Jonathan Burns, 2024. Ground Penetrating Radar Survey of Former Fort Halifax, Halifax, Pennsylvania. AEG News. Vol. 67, No. 4 - Program with Abstracts. (link)
Abstract:
The former Fort Halifax was located along the Susquehanna River from 1756 to 1757 during the French and Indian War period. The approximate shape and dimensions of the fort are known from historical documents, but its exact location is not known. Archaeological excavations run by one of us in 2021 and 2023 revealed what is likely to be the foundation of a structure located near one of the four bastions of the fort. Other documents suggest the presence of a well within or near the northeast bastion. A ground penetrating radar (GPR) survey was conducted in November 2023 to search for the well and other architectural anomalies, using a 900 MHz antenna in a 50 m by 50 m area. Results suggest that the well is approximately 1.5 m in diameter and about 30 cm below the surface. Excavations planned for June 2024 are expected to conduct ground truthing.
Download the poster presented at the Annual Meeting in Philadelphia on September 12, 2024, with excavation results.
Ryan Mathur, Jonathan Burns, Glenn Nelson, Karen Morrow, James Stuby, Martin Helmke, Daniel Bochicchio, Linda Godfrey, George Kamenov, George Pedlow, 2023. Finding Fort Roberdeau. Historical Archaeology (2023). (link)
Abstract:
Fort Roberdeau was a lead mine in central Pennsylvania during the period of the American Revolution. Scant information exists on the original position of the fort, the location of mining activity in the area during the period of the Revolution, or artifacts from this period. Subsequent farming, mining exploration, and the placement of the current replica fort (erected 1976) obscure the landform and hinder identification of Revolutionary-period mining activities. As a means of locating where the mining activities occurred and the original position of the fort, this study integrates historical, geological, geophysical, geochemical, geomorphological, and archaeological data. Geological mapping identified potential areas of past mining, and geophysical resistivity surveys verified at least one Revolutionary-period mine, since the location and dimensions of the subsurface anomaly match historical records. The positions of period metallic artifacts in conjunction with a road and corner of the original fort (identified with LiDAR and thermal imagery) place the original fort near the current replica.
Stuby, J. and Lolcama, J., 2021. Spontaneous Potential as a Method for Identifying Karst Flow Conduits at Aggregate Quarries. 33rd Symposium on the Application of Geophysics to Engineering and Environmental Problems (SAGEEP 2021). (link)
Abstract:
Spontaneous Potential (SP) surveys were carried out at a limestone quarry in the central Appalachian region in 2001 and 2019, in order to identify the location of groundwater conduits between a nearby river and the quarry pit. A new anomaly developed between the time of the surveys at a fault zone where river water was confirmed to be entering the quarry by tracer testing, demonstrating that SP is an effective tool for searching for such conduits. Confidence in interpretation of results is enhanced when a baseline survey is available for comparison with later surveys.
Stuby, J., 2017. Geophysical Surveys, Fort Roberdeau. Pre-conference presentation for the 82nd Annual Field Conference of Pennsylvania Geologists, 2017. Recent Geologic Studies & Initiatives in Central Pennsylvania.
Summary:
I collaborated with Dr. Ryan Mathur, Geology Professor at Juniata College, and his introductory geophysics class for one day in April 2017 at the historic Fort Roberdeau in Blair County, Pennsylvania. I presented a summary of the investigation which included electrical resistivity and ground penetrating radar (GPR). Dr. Mathur presented other aspects of the study such as mineralogy. Geologist George Pedlow performed an analysis of historical maps and air photos in addition to field observations.
An article in the Juniatian has a description of the fieldwork in 2017 and a project overview. (pages 24-29).
I collaborated with Dr. Mathur's class again in 2019 (different students). Results of that investigation and that of archaeologists, historians, and other geologists were published in Historical Archaeology in 2023 (see above).
Lolcama, J., and Stuby, J., 2015. Remote Detection of Deep Conduit Flow by a Novel Brine-Enhanced Electrical Resistivity Surveying Method. Proceedings of Dam Safety 2015, New Orleans, LA. (link)
Abstract:
This paper provides an overview of a novel method for rapidly locating and imaging deep-lying karstic flow channels that can carry flooding rates of flow through limestone and dolomite bedrock. The method is applicable to rapid reconnaissance investigations for leakage through karstic bedrock below a dam, and flooding investigations of pits, quarries, and underground mines. Major karst solution channels at depths of over 200 feet (61 m) have been efficiently located, drilled, and tested for grouting repair, in weeks rather than months timeframe. The three applications of the method which have been completed to date have used a modified data acquisition for 2-D electrical resistivity imaging of the subsurface. The imaging may require up to 112 electrodes at 3 m spacing for a surveyed length of 333 m (1,092 ft). An initial, background survey of ground resistivity prior to brine injection was completed to measure ambient resistivity conditions throughout the surveyed area. Constant-rate injection of saturated NaCl brine solution into the turbulent flowing groundwater commenced immediately after the background survey. The conductivity of the groundwater reached roughly 10 times background after mixing with the salt solution during turbulent flow within the karstic channels. After a pre-determined delay time, which allowed the salt mixture to travel to the survey area from the point of injection, the second resistivity survey was initiated. The volume of saturated brine injected was roughly 15,000 gallons (57,000 L), and the continuous pumping rate was about 200 GPM (757 L/min).
The 2-D models of subsurface resistivity from the pre-brine, and brine-enhancement surveys were subtracted, producing a conductive anomaly map of the 2-D imaged area. An anomaly of roughly -500 Ohm-m, with a cross-sectional area of about 20,000 ft2 (1,860 m2), was located in a surveyed area roughly 11X this size. The conductive anomaly was drilled with several deep boreholes, and each borehole was fitted with a perforated PVC sleeve and logged for water quality evidence of surface water recharge flowing at depth. The logging confirmed that the anomaly represents the primary extent of the subsurface flow.
Planning, setup, and execution of the testing can be accomplished within two weeks, with anomaly maps available soon thereafter. This enhancement to the standard 2-D electrical resistivity survey is believed to be the first application of its kind at this scale.
A related paper by my coauthor J. Lolcama describes the method and some of the results.
Bolt, L. R., Stuby, J. L., Li, P. H., and Martin, D., 2003. Maryland's Experience with Large Scale Grouting for Roadway Stabilization in Karst Terrain of I-70. Proceedings, 54th Highway Geology Symposium, Burlington, Vermont. (link to PDF)
Abstract:
I-70 near Frederick, Maryland, has a history of sinkholes and dolines developing in soils overlying folded and fractured limestone. For its reconstruction, geophysical methods were utilized to select zones for stabilizing by pressure grouting along the soil-rock contact.
Grout holes were drilled on 12 ft. centers through the soil and epikarst into 5 ft. of limestone. Grouting started at the top of rock and continued to the surface. Grout was produced by an onsite plant to achieve minimum time between drilling and injection.
Only roadway areas were grouted, and this was accomplished early, prior to main construction. Approximately 2200 borings, consuming over 10,000 cubic yards of grout were completed. Daily drilling and grout quantity data were plotted by hand to insure quality control, to design secondary borings, and to alter the limits of the grout zones. The depth-to-rock and grout volume data were later analyzed and compared to the geophysical survey using 3D software. Evaluation is still in progress, but based on past performance of smaller projects, the method appears to achieve the result of roadway stabilization at an efficient cost.
Stuby, J., Boardman, M., and Carney, C., 2001. Description and Depositional History of an Open, Carbonate Lagoon: Rice Bay, San Salvador, Bahamas. Proceedings of the 10th Symposium on the Geology of the Bahamas and Other Carbonate Regions. Edited by Benjamin J. Greenstein and Cindy K. Carney. Gerace Research Center, San Salvador, Bahamas. (link to PDF)
Abstract:
Rice Bay is an open, windward, sandy, carbonate lagoon, approximately 1 km x 1 km in area, located on the northeast corner of San Salvador Island in the Bahamas. It is separated from other lagoons and the open Atlantic Ocean by North Point, Cut Cay, and Man Head Cay, all consisting of lithified eolianites. There are beaches on the mainland and on Man Head Cay. The subtidal surface of Rice Bay consists of a mosaic of subenvironments: barren carbonate sand and mud, Thalassia and Syringodium (seagrass) meadows, areas of calcareous green and red algae, subtidal beachrock, and patch reefs.
Forty-six intertidal and subtidal sediment samples were collected from the sea floor of Rice Bay along a 450 m long transect between the two beaches (Transect A). This transect passes through all of the subenvironments except a patch reef. Three sediment cores were taken from Rice Bay: two close to Rice Bay beach and one from near the center of Transect A. Sediment thicknesses in the complete cores range from 3.58 m to 4.51 m. Eight supratidal rock samples were collected from the southwestern side of Man Head Cay.
Results of a petrographic analysis indicate that the subtidal sediment of Rice Bay consists of 40% mollusks, 24% intraclasts, 14% algae, 7% peloids, 6% foraminifera, 6% other skeletal grains, 2% ooids, and 1 % oolitic clasts. The core sediment has a similar composition to that of the surface transect, but shows an increase in ooid content with depth. Samples from Man Head Cay have high porosity (26%) and consists of 33% intraclasts, 23% mollusks, 19% algae, 10% foraminifera, 9% peloids, and 6% other skeletal grains, with no mud, ooids, or oolitic clasts.
Three facies have been recognized in the sediment cores. One (A) is poorly sorted lagoon deposits, one (B) is a moderately sorted beach deposit underneath the lagoon deposits, and the last (C) is peat at the base of the complete cores. This peat has been radiocarbon dated to 6300 BP.
The depositional history of Rice Bay begins in the Late Pleistocene, with the formation of Man Head Cay at the end of the Oxygen Isotope Substage Se highstand (-119 ka). A paleosol developed on San Salvador during the following lowstand. The Holocene history may be divided into three phases. Early Transgression (1-6 ka): platform edges were flooded and peat accumulated in the restricted lagoon. Middle Transgression (6-5 ka): continuing sea level rise allowed open exchange of seawater and sediment production allowed formation of North Point dunes; ooids were generated. Late Transgression (5-0 ka): Rice Bay continues to be filled with sand as North Point erodes.
Other publicly available documents of projects in which Jim was involved:
Final Pilot Study, Advanced Geophysical Classification, Spring Valley Formerly Used Defense Site, Spring Valley, Washington, DC (USACE, 2016)
Hagerstown Multi-Use Sports and Events Facility - Concept Design Report, Hagerstown, Maryland (RK&K, 2021)