Palaeoenvironment, Palaeoclimate and Stable Carbon Isotopes of Palaeozoic Red-Bed Palaeosols, Appalachian Basin, USA and Canada

  1. Médard Thiry and
  2. Régine Simon-Coinçon
  1. C. I. Mora and
  2. S. G. Driese

Published Online: 14 APR 2009

DOI: 10.1002/9781444304190.ch3

Palaeoweathering, Palaeosurfaces and Related Continental Deposits

Palaeoweathering, Palaeosurfaces and Related Continental Deposits

How to Cite

Mora, C. I. and Driese, S. G. (1995) Palaeoenvironment, Palaeoclimate and Stable Carbon Isotopes of Palaeozoic Red-Bed Palaeosols, Appalachian Basin, USA and Canada, in Palaeoweathering, Palaeosurfaces and Related Continental Deposits (eds M. Thiry and R. Simon-Coinçon), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444304190.ch3

Author Information

  1. Department of Geological Sciences, University of Tennessee-Knoxville, Knoxville, TN 37996–1410, USA

Publication History

  1. Published Online: 14 APR 2009
  2. Published Print: 26 MAY 1995

ISBN Information

Print ISBN: 9780632053117

Online ISBN: 9781444304190

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Keywords:

  • pedogenic carbonate, consisting of calcite nodules and rhizoliths;
  • Juniata Formation vertic palaeosol chemistry, indicating salinization;
  • Conemaugh Group palaeosols, exhibiting colour variations;
  • post-Devonian palaeoclimate, ‘megamonsoonal’ and influencing Appalachian Orogen;
  • Silurian and Early Devonian plant communities, occupying wet coastal-margin environments;
  • nodular pedogenic carbonate, exhibiting spherical to prolate micrite nodules

Summary

Palaeosols with vertic (Vertisol-like) features occur in the upper clay-rich parts of upward-fining sequences in Palaeozoic red-bed successions ranging from Ordovician to Permian age within the Appalachian Basin, USA and Canada. Occurrences of vertic features in nearly all of the claystone palaeosols indicate persistence of a seasonally wet-dry palaeoclimate and smectitic clay sources in the Appalachian region for nearly 180 Myr, over palaeolatitudes ranging from 0 to 30° south. Palaeosols are developed in both allocyclic, marginal-marine deposits and autogenic, alluvial-plain deposits, and are characterized by very weak horizonation, abundant pedogenic slickensides, and a micromorphology dominated by sepic-plasmic fabrics and peds bounded by stress cutans, hence they broadly are analogous to USDA vertic Entisols and Inceptisols. Pedogenic carbonate is generally abundant, and consists of calcite nodules and rhizoliths. Variations in palaeosol morphology and stable isotope geochemistry are attributed to:

1 differences in the pedogenic and geomorphic environments, whether coastal margin or inland alluvial;

2 differences in the evolutionary state of the soil ecosystem, in particular, the presence of vascular plants, with or without deep root systems.

Consideration of these controls permits interpretation of the carbon isotope compositions of pedogenic carbonate as a proxy for Palaeozoic atmospheric CO2 levels. Our results suggest a steep decrease in atmospheric CO2 levels between the late Silurian (3200–5200 p.p.m.) and early Permian (150–200 p.p.m.), which was associated with the rapid evolution and diversification of vascular land plants and global climate change, leading to the extensive Permo-Carboniferous glaciation.