Discussion of "Geochemical evidence for the origin of late Quaternary loess in central Alaska"

Abstract

In a recent paper, Muhs and Budahn (2006) aim to test regional paleowind hypotheses put forth in the literature for the provenance of Quaternary loess deposits in central Alaska with geochemical evidence. The experimental design of their study consists of a comparison and multilinear regression analysis (MRA) of major element and rare-earth element (REE) geochemistry between possible source sediment material along the Yukon, Tanana, and Nenana rivers and the youngest loess units of three deposits near Fairbanks, Alaska (see their fig. 2). Such a study has been long overdue and we applaud their initiative. However, through this discussion letter, we wish to address two points. The first concerns the “opposing” hypotheses to be tested, while the second concerns aspects of their experimental design. Muhs and Budahn (2006, pp. 324–325) set out to “test the opposing hypotheses of northerly versus southerly paleowinds for the origin of Quaternary loess in central Alaska”. Literature accounts of paleowind reconstructions are either based on sand dune orientations and sand sheet locations or loess deposits. For both types of archives, sand and loess, the inferred paleowinds are presented by the authors as inconsistent and contradictory. We argue that the platform on which this paper is set up (i.e., north versus south) is built from a misinterpretation and inaccurate representations of previous work referenced as supporting evidence. Furthermore, temporal variability, an important issue, appears to be cast aside. Concerning aeolian sand deposits in the inner parts of central Alaska, Hopkins (1982) and Lea and Waythomas (1990) conclude winds came from a northeasterly direction during the last glacial maximum. Muhs and Budahn (2006) hypothesize (p. 324) from the occurrence of aeolian sands of early Holocene age north of9the Yukon River near the confluence of the Porcupine River (see Froese et al. 2005 and their fig. 1 for location) that winds must …