1 Using Near Surface Geophysics to Solve Geological Problems

Sunday, 21 April 2024
1:30 PM - 5:30 PM
Maui Ballroom, Oasis CC

MELTWATER CHANNELS IN THE KARST BELLEVUE-CASTALIA PLAIN, SENECA COUNTY, OHIO

Paper number: 1-3
Program: Theme Sessions
Time: 2:10 PM – 2:30 PM

Authors

Abstract

The Bellevue-Castalia karst plain in Seneca County, north central Ohio, hosts numerous channel-like depressions previously interpreted to be associated with large sinkholes. The channels are 3–6 m deep, start and stop abruptly, and are generally parallel to ice flow direction, trending uphill from the northeast. Sinkholes of varying sizes are within and outside the channels. A low-density network of existing well-logs prevents determining if the channels are incised into the Columbus Limestone bedrock or glacial sediment. Hence, this study combines electrical resistivity imaging with a geomorphological analysis of the channels’ orientation and distribution to assess the architecture and origin of the channels. Several electrical resistivity tomography (ERT) transects <350 m long were collected across the channels using a dipole-dipole electrode array and a 1 m unit electrode spacing The ERT results shows two main resistivity units with discontinuities within each unit The lower unit with higher resistivity values (250–2500 Ω-m) is interpreted as the limestone bedrock with an irregular upper surface. The overlying less resistive (25–100 Ω-m) unit with thicknesses of 3–5 m inside the channels and ~1–3 m outside the channels is interpreted as till. Soil sampling along the ERT transects by soil auger reached refusal consistently at ~2 m depth. From the ERT results, the bedrock is at a lower elevation beneath the channels than the ground surface adjacent to the channels. This observation indicates the meltwater channels are incised into bedrock, and the till deposit has a sheet-like geometry draping the bedrock surface. The irregular bedrock surface likely reflects a combination of unequal meltwater incision across the channel bottom, and postglacial karstification of the bedrock surface, consistent with the presence of sinkholes within the channels.

Geological Society of America Abstracts with Programs. Vol. 56, No. 3

doi: 10.1130/abs/2024NC-398961

© Copyright 2024 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.