Research Summary:

Although several recent studies have examined Fe mobility during both pedogenesis and later burial diagenesis of modern Vertisols and Paleozoic vertic claystone paleosols, studies that quantify the transfer of soluble Fe from these paleosols into subjacent limestone deposits undergoing meteoric diagenesis are lacking currently. This study addresses this knowledge gap by quantifying the amount of Fe in meteoric pore waters derived from a Late Mississippian paleoVertisol from Tennessee. Meteoric-fluid Fe compositions can be constrained by observed Fe values present in stabilized echinoderm grains located in a subjacent limestone that experienced paleokarst and meteoric diagenesis during late Mississippian and early Pennsylvanian time. This paper uses the iterative modeling approach of Banner and Hanson (1990) to constrain the Fe composition of the meteoric diagenetic fluid associated with the Pennington paleokarst surface. Significantly, this approach demonstrates that vertic claystone paleosols represent a potential source of abundant, transferable Fe that can be incorporated into meteoric diagenetic fluids. Additionally, this paper shows the utility of this approach to ancient carbonate sequences in general by constraining the time required to facilitate stabilization of metastable carbonate. Significant conclusions of this work include:

(1) Modeling constrains the magnitude of Fe transfer associated with echinoderm stabilization was a fraction (8 to 14%) of the total quantity of Fe lost from the gleyed paleosol. Consequently, transfer of Fe from the paleosol to subjacent limestone could have continued as the paleokarst surface was buried.

(2) Timescales for echinoderm stabilization were probably < 12 ky. Stabilizing pore fluids likely had an elevated DIC value, which is consistent with an organic diagenetic setting localized immediately below the paleokarst surface.

(3) Significantly, this method has the potential to be applied to constrain mineraological stabilization timescales in other ancient carbonate sequences.

Papers:

Tobin, K.J., and Driese, S.G., 2003, Control on transitional element chemistry of diagenetic calcite associated with paleokarst at the Mississippian-Pennsylvanian boundary in Tennessee, Journal of Sedimentary Research; 73: 204-214.

Caudill, M.A. et al. , 1992, Preliminary interpretations of paleosols associated with Late Mississippian marginal marine deposits, Pennington Formation, Monterey, TN, In: Driese, S.G. et al., eds., Paleosols, Paleoweathering Surfaces, and Sequence Boundaries. SEPM Mid-Continent Section Annual Meeting and Field Conference, University of Tennessee Studies in Geology 21, p. 57-78.

Abstracts:

Tobin, K.J., and Driese, S.G., 2001, Geomicrobiology control on diagenetic calcite associated with paleokarst at the Mississippian-Pennsylvanian boundary in Tennessee. GSA Abstract. 33(7).

Driese, S.G, Tobin, K.J., and et al., 1992, Paleopedology and stable isotopic chemistry of Mississippian vertic claystone paleosols, Pennington Fm., TN. GSA Abstract, 24(4): 13.