The importance of both geological and pedological processes in control of grain size and sedimentation rates in Peoria Loess Hong Wang a, ⁎ , Joseph A. Mason b , William L. Balsam c a Illinois State Geological Survey, 615 Peabody Drive, Champaign, IL 61820, USA b Department of Geography, University of Wisconsin at Madison, Madison, WI 53706, USA c Department of Geology, University of Texas at Arlington, Arlington, TX 76019, USA Received 23 May 2005; received in revised form 27 February 2006; accepted 2 April 2006 Available online 30 May 2006 Abstract The loess–paleosol succession in the Peoria Loess in southern Illinois is characterized as alternating loess layers and weathering bands, known as paleosol A horizons. The fast loess accumulation during the late Wisconsin glaciation interacted with the incipient pedogenesis and caused unclear boundaries of loess–paleosol alternations in soil horizonation and mineralogy. Parameters of grain size distribution, sedimentation rate, matrix carbonate content and diffuse reflectance (i.e. soil colors and iron oxides) are used in this paper to discuss the geological and pedological influences for the Peoria Loess in Keller Farm section in southern Illinois. The multi-proxy analysis revealed that many paleosol A horizons, defined by the diffuse reflectance variability, contain finer-grained materials with a relatively higher sedimentation rate. It suggests that glaciofluvial sediments were available in the source areas for uploading eolian dust during the temporary ice sheet retreats. The denser vegetation and wetter surface soils on the loess deposit area could increase the dust trapping efficiency and caused a greater accumulation rate of loess deposits. The coarser-grained materials and slower sedimentation rate are often found in loess layers. It suggests that strong surface winds transported the coarser-grained materials from local dust sources and sparse vegetation and dry surface soils reduced the dust trapping efficiency during the ice sheet readvance. The strong interactions between the geological and pedological processes played an important role on the loess–paleosol alternations in southern Illinois during the late Wisconsin glaciation. © 2006 Elsevier B.V. All rights reserved. Keywords: Geological and pedological interaction in Peoria Loess; Grain size distribution; Sedimentation rate; Diffuse reflectance variability; Paleoclimate change 1. Introduction The Peoria Loess, deposited during the late Wiscon- sin glaciation in southern Illinois, is characterized as numerical loess layers and alternating weathering bands, known as incipient paleosol A horizons. The general fast loess accumulation during the late Wisconsin glaciation in southern Illinois interacted with the incipient pedogenesis, causing unclear boundaries of loess– paleosol alternations. The vague soil horizonation and less distinctive variations in clay mineralogy can hardly provide details for paleoclimate record and dynamic links between geological and pedological processes. In this paper, we compared grain size, sedimentation rate, matrix carbonate content and diffuse reflectance (soil Geoderma 136 (2006) 388 – 400 www.elsevier.com/locate/geoderma ⁎ Corresponding author. Tel.: +1 217 244 7692; fax: +1 217 333 4722. E-mail address: hongw@isgs.uiuc.edu (H. Wang). 0016-7061/$ - see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.geoderma.2006.04.005