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Climatic significance of natric horizons in Permian (Asselian) palaeosols of north‐central Kansas, USA
Author(s) -
McCAHON THOMAS J.,
MILLER KEITH B.
Publication year - 1997
Publication title -
sedimentology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.494
H-Index - 108
eISSN - 1365-3091
pISSN - 0037-0746
DOI - 10.1111/j.1365-3091.1997.tb00427.x
Subject(s) - paleosol , geology , permian , paleontology , horizon , arid , paleoclimatology , evaporite , geochemistry , sedimentary rock , climate change , structural basin , oceanography , geometry , mathematics , loess
Columnar structured horizons have been recognized in ancient coastal palaeosols of several Lower Permian (Asselian) stratigraphic units of north‐central Kansas. These strongly developed columnar, polygonal‐shaped peds are characteristic of sodium‐influenced (natric) argillic horizons, and are commonly indicative of semi‐arid to arid environments. Evaporite features above and below these palaeosols support the conclusion for a dry palaeoclimate. The columnar peds are typically 3–15 cm in diameter and exhibit domed tops. Fine clay fills the cracks between the columnar peds, and is generally of a darker colour than the peds. Each natric horizon has a low value and chroma colour, apparently the result of carbonate accumulation. The natric horizons in these Permian palaeosols appear to have been partially influenced by sodium‐rich groundwaters. Root traces and root moulds are found between peds in all natric horizons, indicating plant succession after columnar ped formation. These sodium‐influenced palaeosol profiles occur as part of a spectrum of palaeosol types that indicate cyclical climate change associated with glacioeustatic sea‐level fluctuations.