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Soil-forming rates and processes on Quaternary moraines near Lago Buenos Aires, Argentina

Published online by Cambridge University Press:  20 January 2017

Daniel C. Douglass*
Affiliation:
Department of Geology and Geophysics, University of Wisconsin, Madison, 1215 West Dayton Street, Madison, WI 53706, USA
James G. Bockheim
Affiliation:
Department of Soil Science, University of Wisconsin, Madison, 1525 Observatory Drive, Madison, WI 53706-1299, USA
*
*Corresponding author.E-mail address: douglass@geology.wisc.edu(D.C. Douglass).

Abstract

Thirty-four pedons on four moraine groups spanning the last 1 myr are used to investigate mechanisms and rates of soil development in Santa Cruz province, Argentina. All soils are coarse-loamy, mesic, Typic Haplocalcids or Calcic Haploxerolls occurring under short grass-shrub steppe, in a semi-arid climate. The dominant soil-forming processes are the accumulation of organic matter, carbonate, and clay-sized particles. Organic carbon accumulates rapidly in these soils, but significantly higher amounts in the oldest two moraine groups are likely the result of slight differences in soil-forming environment or grazing practices. Accumulation rates of carbonate and clay decrease with age, suggesting either decreased influx in the earliest part of the record or attainment of equilibrium between influx and loss. There are no changes in soil redness, and preservation of weatherable minerals in the oldest soils indicates there is little chemical weathering in this environment. Measured dust input explains the accumulation of both clay and carbonate. We present a carbonate cycling model that describes potential sources and calcium mobility in this environment. Calibration of rates of soil formation creates a powerful correlation tool for comparing other glacial deposits in Argentina to the well-dated moraines at Lago Buenos Aires.

Information

Type
Original Articles
Copyright
University of Washington

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Supplementary material: File

Douglass and Bockheim Supplementary Material

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