Paleopedology plus TL, Be-10, and C-14 dating as tools in stratigraphic and paleoclimatic investigations, Mississippi River Valley, USA

Thick (less than or equal to 35 m) loess deposits are present on ridges and high bluffs in the northern-half of the Lower Mississippi Valley (LMV), U. S.A. Detailed descriptions of the loess sections and pedologic, physiochemi cal, and mineralogic analyses and TL, C-14,and Be-10 age determinations, al low preliminary paleoclimatic reconstructions for the late Quaternary of ce ntral North America. No age data are available for the oldest (Fifth) loess . Be-10 and TL age data suggest a 250-200 ka age for the Fourth or Crowleys Ridge(?) Loess, and indicate that the Loveland or Third Loess is time equi valent to oxygen isotope stage 6, similar to 190-120 ka. A weakly developed paleosol is present in the basal-half of the Loveland. The Sangamon Geosol is present in the upper 5 m and represents all of oxygen isotope stage 5, similar to 130-60 ka. It formed in a climate as warm as, but drier and (or) with greater variation in precipitation, than the present. The Roxana Silt (second loess) was deposited during oxygen isotope stages 4 and 3, similar to 65-26 ka. The early Wisconsinan interglacial-glacial transition, repres ented by the Sangamon Geosol and the unnamed paleosol in the basal Roxana S ilt, was slow. The paleoclimate during the 35 k yr of Roxana deposition was cool to cold and wet. Age and pedologic data indicate that deposition of t he Peoria Loess (the youngest) began around 25 ka when the area's climate c hanged abruptly from cool or cold and wet to cold and dry, with periods of sustained high winds. (C) 1998 Published by INQUA/Elsevier Science Ltd. All rights reserved.