4 Near-Surface Geophysics and Geoarchaeology: Methods and Mapping

We invite abstracts that will highlight applied methodologies and mapping projects, including near-surface geophysics (e.g., GPR, resistivity, magnetometry), remote sensing (e.g., drones, LiDAR), or comparisons in GPS accuracy and precision (e.g., GNSS, N-Trip, RTK)

Monday, 9 March 2026
9:30 AM - 11:00 AM
RCC, 106

Geophysical Mapping of Point Bars and Compound Bars Along the Great Miami River, Southwestern Ohio

Paper number: 4-2
Program: Technical Sessions
Time: 9:50 AM – 10:05 AM

Authors

Abstract

Per- and polyfluoroalkyl substances (PFAS) are long-lived chemicals that are found in our waterways, soil, and air. PFAS chemicals are used in manufacturing plants, fire extinguishing foams, food packing, and household products. Following use, PFAS can flow into surface water and leach PFAS into groundwater. Recent work shows that within the critical zone PFAS preferentially sorbs onto fine grained sediment, indicating the need to understand the distribution of sorption hot spots within heterogeneous fluvial deposits. This study focuses on the potential accumulation of PFAS at several sites along the Great Miami River in southwestern Ohio. The aquifer replenished by the Great Miami River supplies ~2.3 million people with drinking water and PFAS has been detected in the river water.  

In this study we used a Dualem421s electromagnetic induction (EMI) and IRIS Syscal Kid 24switch electrical resistivity tomography (ERT) to evaluate point and compound bar architecture at Roadside Dog Park in Piqua, Heritage Park, and Miami Township West Community Park in Cleves along the Great Miami River. A Geophex GEM-2 multi-frequency broadband EMI was used at Great Miami River Trail at Trenton. A grid survey of 2m spacing in the long direction and 5m spacing of the short direction was conducted with the EMI. An ERT electrode spacing of 1.5m was used for each site. ERT data are used to help calibrate the EMI data by joint inversion.

Our preliminary results show laterally extensive zones at approximately 1-3m depth. This zone shows higher electrical conductivity and lower resistivity compared to the surrounding material. These signatures are consistent with finer-grained sediments, such as clays and silts. Variations in geophysical response suggest that the subsurface composition is locally heterogenous but dominantly fine-grained. This result is consistent with recent local studies depicting fine grained material around 1-3m depth of compound and point bars. This study shows the utility of using geophysical techniques to better understand fluvial sedimentary to better evaluate PFAS fate, transport, and sorption.

Geological Society of America Abstracts with Programs. Vol. 58, No. 1

doi: 10.1130/abs/2026SE-411864

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