UCARE: Undergraduate Creative Activities & Research Experiences


Date of this Version

Spring 4-2016

Document Type



Anthony J. Kohtz, Richard M. Kettler, David B. Loope "Iron concretions in the Cretaceous Dakota Formation" (2016). UCARE Poster session, University of Nebraska-Lincoln Research Fair, April 2016, Lincoln, NE.. UNL Digital Commons


The author thanks Richard Kettler and David Loope for informative and helpful discussions, as well as help in advising and developing the project.

Copyright © 2016 Anthony Kohtz, Richard Kettler, David Loope


The Cretaceous Dakota Formation contains abundant iron oxide concretions. The precursors to the iron concretions are siderite (FeCO3) nodules that formed in a reducing floodplain environment. A variety of concretion morphologies formed when the precursor siderite nodules were dissolved by oxidizing groundwater in a paleoaquifer. Iron-oxidizing bacteria are able to oxidize aqueous Fe(II) to Fe(III) oxy-hydroxide at microaerophilic and neutrophilic conditions. This study investigated these concretions to determine if there was a microbial element in their formation and to characterize the concretion morphologies present in the Dakota. This is important for complete paleoenvironment interpretations and astrobiology pursuits.