Physico-chemical environment of pedogenic carbonate formation in Devonian vertic paleosols, central Pennsylvania

Conference · Wed Jan 01 04:00:00 EST 1992 · Geological Society of America, Abstracts with Programs; (United States)

OSTI ID:5690406

Driese, S G; Mora, C I ^[1]

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1. Univ. of Tennessee, Knoxville, TN (United States). Dept. of Geological Sciences

The morphology and geochemistry of pedogenic carbonate found in vertic claystone paleosols in the Devonian Catskill Formation in central Pennsylvania preserve a record of the physical and chemical environment of carbonate precipitation. The carbonate is characterized by three distinct petrographic phases. Pedogenic rhizoliths and nodules are the earliest precipitated phases. Clear, equant calcite spar cements fill voids in the centers of rhizoliths, as well as circumgranular cracks and septarian voids in nodules. Late-stage pedogenic fractures are always occluded with very bright yellow-orange luminescent spar cements. The incorporation of progressively higher concentrations of Mn into successively younger calcite spar cements, without concomitant increases in Fe, suggests carbonate precipitation from an evolving meteoric water in which Mn[sup 2+] became increasingly mobile over time. The increased mobility is possibly due to decreasing Eh resulting from oxidation of organic matter after rapid soil burial on the flood plain. Carbon isotope compositions of pedogenic carbonate correlate with the inferred depths of carbonate precipitation. Rhizoliths preserved below the lowest stratigraphic occurrences of pedogenic slickensides are consistently depleted in C-13 relative to nodules which formed stratigraphically higher, within the zone of active soil shrink-swell processes. Nodular carbonate precipitated in proximity to deep cracks in the soil is enriched due to increased gas exchange with isotopically-heavy atmospheric CO[sub 2], whereas the environment in which rhizoliths precipitated was dominated by isotopically-light plant-root-respired CO[sub 2]. These results are relevant to models which use the carbon isotope compositions of pedogenic carbonate to estimate paleoatmospheric levels of CO[sub 2].

• OSTI ID: 5690406
• Report Number(s): CONF-921058--
• Conference Information: Journal Name: Geological Society of America, Abstracts with Programs; (United States) Journal Volume: 24:7
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
ATMOSPHERIC CHEMISTRY
CARBON 13
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON ISOTOPES
CARBON OXIDES
CARBONATE ROCKS
CHALCOGENIDES
CHEMISTRY
CLIMATE MODELS
DEVELOPED COUNTRIES
DEVONIAN PERIOD
EVEN-ODD NUCLEI
GEOCHEMISTRY
GEOLOGIC AGES
GEOLOGIC HISTORY
GEOLOGIC STRUCTURES
ISOTOPE RATIO
ISOTOPES
LIGHT NUCLEI
MATHEMATICAL MODELS
NORTH AMERICA
NUCLEI
OXIDES
OXYGEN COMPOUNDS
PALEOZOIC ERA
PENNSYLVANIA
PHASE STUDIES
PRECIPITATION
ROCKS
SEDIMENTARY BASINS
SEDIMENTARY ROCKS
SEPARATION PROCESSES
SOIL CHEMISTRY
STABLE ISOTOPES
USA