Origin and paleoclimatic significance of late Quaternary loess in Nebraska: Evidence from stratigraphy, chronology, sedimentology, and geochemistry

Abstract

Rachel, "Origin and paleoclimatic signifi cance of late Quaternary loess in Nebraska: Evidence from stratigraphy, chronology, sedimentology, and geochemistry" (2008 The spatial variability of particle size abundances in Peoria Loess shows a northwest-to-southeast fi ning in Nebraska, consistent with maps of previous workers that show a northwest-to-southeast thinning of loess. These observations indicate that paleowinds that deposited the loess were from the west or northwest and that the source or sources of Peoria Loess lay to the west or northwest.New mineralogical and geochemical data indicate that the most important sources of loess were likely Tertiary siltstones of the White River and Arikaree Groups, silt facies of Pliocene eolian sediments, and small contributions from Pierre Shale. It is likely that fi ne-grained silts were transported episodically through the Nebraska Sand Hills from

Isotopic evidence for the diversity of late Quaternary loess in Nebraska: Glaciogenic and nonglaciogenic sources

“…From K-feldspar isotopic data alone, we are unable to determine if this change in Pb isotope ratio is caused by an increased fl ux of silt defl ated from the Platte, or a decrease in the eolian component defl ated from the White River Group. However, we suspect it is more likely the former, as the mass accumulation rate increases upsection at Eustis (Roberts et al, 2003) despite no systematic trend in particle size (Muhs et al, 2008).…”

“…2). The Sioux City, Iowa, locality is situated where the Missouri River is likely to have been the major loess source (see discussion in Muhs et al, 2008 Pb ratios (Fig. 4D).…”

“…Muhs et al, 1999aMuhs et al, , 2008Muhs and Budahn, 2006;Aleinikoff et al, 1999;Sun, 2002aSun, , 2002bYokoo et al, 2004), as well as tracing glaciogenic sediments (Bell and Murton, 1995). The goal of our study is to utilize two independent isotopic systems, initial Pb isotope ratios in K-feldspars and U-Pb ages of zircons, to determine the source(s) of late Wisconsin Peoria Loess in Nebraska and western Iowa in order to infer paleowind directions during the last glacial period.…”

Rates of consumption of atmospheric CO<sub>2</sub> through the weathering of loess during the next 100 yr of climate change

“…Minerals include primary silicates (potassium feldspar, plagioclase feldspar, quartz), secondary clay minerals (dominated by smectites), and carbonate phases (calcite and dolomite) (Muhs et al, 2008). Given this mixed mineralogy, a quantitative description of the evolution of loess weathering as a function of climate change is not an easy task.…”

“…In North America, loess is one of the most extensive surficial deposits, especially in the central Great Plains region where it is known as the Peoria loess (Rousseau, 2001;Muhs et al, 2008). Minerals include primary silicates (potassium feldspar, plagioclase feldspar, quartz), secondary clay minerals (dominated by smectites), and carbonate phases (calcite and dolomite) (Muhs et al, 2008).…”