Palaeosol Stratigraphy across the Permian-Triassic Boundary, Bogda Mountains, NW China: Implications for Palaeoenvironmental Transition through Earth's Largest Mass Extinction

Abstract

Upper Permian and Lower Triassic palaeosols from northeastern Tethyan localities exposed within the Bogda Mountains, NW China, provide a wealth of information regarding long-term palaeoclimatic and palaeoenvironmental variations. Wuchiapingian palaeosols are characterized by intense redoximorphy, accumulation of vascular plant matter, accumulation of clay minerals and Fe-oxides, slickensides, and clastic dikes, suggesting a soil moisture regime that ranged from perennially wet to distinctly seasonal in soil moisture budget. Changsinghian to early Induan palaeosols include subsurface accumulations of clay and carbonate as well as surficial accumulations of organic matter, indicative of sub-humid to sub-arid soil moisture and variable soil moisture regimes. Induan to Olenekian palaeosols contain pedogenic CaCO3 accumulations and gypsum pseudomorphs, indicating a drier environment characterized by net soil moisture deficiency. Elemental composition of palaeosol matrix was used to estimate palaeoprecipitation through thechemical index of alteration minus Potassium (CIA-K) proxy. Estimates from various Wuchiapingian strata indicate relatively stable palaeoprecipitation. During thelate Changsinghian and early Induan, palaeoprecipitation appears to have decreased from 1100 to 230 (±180)mm/year over less than 100m of vertical stratigraphic section. IntheInduan and Olenekian, palaeoprecipitation appears much less stable than inWuchiapingian, with values vacillating from 290 to 1014mm/year. Thetransition to a relatively unstable precipitation state coincides generally with thePermian-Triassic boundary, and may reflect climatic disturbances associated with theend-Permian extinction event inaddition to altered atmospheric circulation patterns resulting from regional tectonics, moisture availability, and expansion of thesubtropical high pressure belt.

Department(s)

Geosciences and Geological and Petroleum Engineering

Keywords and Phrases

Northwest China; Palaeoclimate; Palaeoprecipitation; Palaeosols; Pangaea; Permian-Triassic Boundary; Terrestrial; Atmospheric Circulation; Carbonate; Chemical Composition; Clay Mineral; Event Stratigraphy; High Pressure System; Mass Extinction; Organic Matter; Paleoatmosphere; Soil Moisture; Tethystype Locality; Vascular Plant; Bogda Mountains; China; Tien Shan; Xinjiang Uygur; Tracheophyta

Geographic Coverage

NW China

Time Period

Permian
Triassic

International Standard Serial Number (ISSN)

0031-0182

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2011 Elsevier, All rights reserved.

Publication Date

01 Jul 2011

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