Buried Pre-Illinoian-Age Lacustrine Deposits with “Green Rust” Colors in Clermont County, Ohio

Author Institution: Bennett & Williams Environmental Consultants Inc., Columbus, OHAuthor Institution: The Ohio State University, School of Environment and Natural Resources, Columbus, OHBuried, Pre-Illinoian-age lacustrine deposits found in at least two separate bedrock valleys in Clermont County, OH, exhibit brilliant colors of “green rust” that alter rapidly when exposed to oxygen. In these settings, the materials are leached of calcium carbonate but the iron has not undergone the redoximorphic depletion typically observed in gleyed hydric soils. Water movement has been exclusively through fractures and along varved bedding planes for approximately 700,000 years, indicating that in these settings, matrix flow is not occurring. The overlying Pre-Illinoian-age Backbone Creek glacial till also exhibits gleyed coloration but these materials are not leached of calcium carbonate. These materials also oxidize when exposed to air, indicating that again, the iron is not removed from the till. A possible correlation to similar permeability properties in northwest Ohio Late-Wisconsinan-age lacustrine materials and fine-grained tills is drawn. The “green rust” provides evidence for minimal to no matrix flow in fine-grained materials and supports the Ohio Fracture Flow Working Group recommendation that water movement along fractures, varved bedding planes, through sand stringers, and along paleosol unconformities be assumed unless matrix contributions have been documented and can be confirmed in these settings