121 Recent Quaternary Research in Lacustrine, Glacial, Eolian, and Tectonic Systems

Monday, 26 September 2016
1:30 PM - 5:30 PM
Room 405

A PROMINENT PEDOGENIC SIGNAL FOR MIS 3 IN THE CENTRAL GREAT PLAINS, USA

Paper number: 121-6
Program: Technical Sessions
Time: 2:45 PM – 3:00 PM

Authors

Abstract

Well-expressed soil development during MIS 3 has long been documented in the ubiquitous loess deposits by several investigators working in the Central Great Plains (and beyond). Mid to late MIS 3 was dominated by pedogenesis, although expressed at some localities as two to three distinct episodes. Stratigraphically, the soils occur within and typically dominate the Gilman Canyon Formation, a relatively thin loess unit, deposition of which likely began in MIS 4. The formation rests on the Loveland soil of MIS 5 and is overlain by the Late Wisconsinan Peoria Loess (MIS 2). Substantial chronological data (14C, TL, OSL) have accumulated, and recent age data indicate pedogenesis began as early 45 ka, and possibly earlier at some sites, and terminated as late as c. 25 ka. Overall, δ13C data produce a pattern clearly indicating that the soil forming intervals are C4 grass-dominated, whereas C3-plant domination occurs in the zones largely unaffected by pedogenesis. In addition, a systematic east-to-west and south-to-north decrease occurs in the δ13C values across the array of documented sites. Recent phytolith and other biogenic opal data are in agreement with the isotopic data, e.g., C4-level δ13C values correspond to increased concentrations of C4 grass tribes (Panicoids and Chloridoids). Phytolith concentration peaks during soil formation and is in agreement with the generalized age model. Limited grass charcoal counts suggest an increase in fire frequency during the periods of soil development, whereas macro-charcoal (Picea sp.) has been found in the lowermost Peoria Loess, immediately overlying the MIS 3 soils. Though not as pronounced, MIS 3 pedogenesis is also expressed within coeval alluvial and aeolian sand stratigraphy, which suggests widespread landscape stability.

Geological Society of America Abstracts with Programs. Vol. 48, No. 7

doi: 10.1130/abs/2016AM-285870

© Copyright 2016 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.