Aminostratigraphic Correlation and Geochronology of Two Quaternary Loess Localities, Central Mississippi Valley

Abstract

Amino acid epimeric (aIle/Ile) values from terrestrial molluscs are used to define and correlate three aminozones in loess sequences exposed across the central Mississippi Valley, in Arkansas and Tennessee. Three superposed aminozones are defined at Wittsburg quarry, Arkansas, primarily using aIle/Ile values from total hydrolysates of the gastropod genus Hendersonia: Peoria Loess (aIle/Ile = 0.07 ± 0.01), Roxana Silt (0.14 ± 0.02), and a third loess (0.28 ± 0.06). Loess units at Wittsburg quarry can be correlated on lithologic characteristics eastward across the Mississippi Valley to the Old River section, near Memphis, Tennessee; however, only one loess unit is fossil-bearing (Peoria Loess, aIle/Ile = 0.05) at that section. Radiocarbon analyses of charcoal from the upper Roxana Silt (ca. 26,000 to 29,000 yr old) and mollusc shell carbonate from the basal Roxana Silt (ca. 39,000 yr old) are used to calibrate amino acid epimeric data for the central Mississippi Valley. These data, applied to the apparent parabolic kinetic model of R. M. Mitterer and N. Kriausakul (1989, Quaternary Science Reviews 8, 353-357), suggest an Illinoian (>120,000 yr) age for the third loess in the central Mississippi Valley that is correlative with part of the Loveland Loess in Illinois and Iowa.

A multi‐proxy palaeoecological and palaeoclimatic record within full glacial lacustrine deposits, western Tennessee, USA

“…While there is a large apparent range for each age estimate, aminostratigraphic correlations independently suggest that the Teneriffe Silt was deposited during the penultimate glaciation, corresponding to MIS 6 (Oches, 2001). D/L and A/I values are also aminostratigraphically comparable to values measured in Pomatiopsis shells from the Illinoian Petersburg Silt (immediately below glacial till) in southern Illinois (Curry et al, 1994;Oches, 2001) and in Hendersonia shells from the Loveland (or 'third') loess in north-eastern Arkansas (Mirecki and Miller, 1994;Oches and McCoy, 2001).…”

“…Although Pomatiopsis has not been analysed from other lastglacial silt units regionally, D/L ratios measured in shells from zone E-4 are comparable to values measured in other taxa from last glacial Peoria Silt elsewhere in the Mississippi Valley (e.g. Mirecki and Miller, 1994;Oches, 2001;Oches and McCoy, 2001), taking into consideration regional MAT differences. These relative ages are also consistent with wood fragment 14 C ages (Fig.…”

“…Parabolic age models for glutamic acid D/L values and A/I values on Pomatiopsis sp. shells point to a correlation with MIS 6 ($190-130 ka), as has been suggested for other Illinoian deposits in the central USA, such as the Loveland loess (Mirecki and Miller, 1994;Oches et al, 1996;Markewich et al, 1998), Petersburg Silt (Curry et al, 1994Oches, 2001;Grimley and McKay, 2004), and related outwash deposits (McKay and Berg, 2008). The timing of slackwater lake deposition within a period of high global ice volumes is reasonable, as high levels of aggradation likely corresponded to maximum Illinoian glacial extent in the north-central USA.…”

“…Amino acid geochronology has previously been applied to Quaternary deposits (up to $800 ka) in the Mississippi Valley region, providing valuable insights (Clark et al, 1989;Mirecki and Miller, 1994;Oches et al, 1996;Oches, 2001). In some studies, parabolic models have been used to represent glutamic acid racemisation and isoleucine epimerisation, although aspartic acid and phenylalanine do not appear to conform to parabolic racemisation models (Kaufman, 1992;Laabs and Kaufman, 2003).…”

Radiocarbon dating loess deposits in the Mississippi Valley using terrestrial gastropod shells (Polygyridae, Helicinidae, and Discidae)

“…Many of these sites, most notably the Vicksburg and Natchez sites ( Fig. 2g and h, respectively), have been the subject of sedimentologic, ecologic, and faunal studies for decades (Wascher et al, 1947;Leighton and Willman, 1950;Leonard and Frye, 1960;Hubricht, 1963;Krinitzsky and Turnbull, 1967;Snowden and Priddy, 1968;Ruhe, 1984a,b;Pye and Johnson, 1988;Clark et al, 1989;McCraw and Autin, 1989;Markewich, 1993Markewich, , 1994Mirecki and Miller, 1994;Oches et al, 1996;Rodbell et al, 1997;Markewich et al, 1998;Oches and McCoy, 2001;Bettis et al, 2003).…”