Reply to the discussion by F. Lagroix and S.K. Banerjee of "Geochemical evidence for the origin of late Quaternary loess in central Alaska"

Abstract

We thank F. Lagroix and (S.K. Banerjee 2006) for their interest in our recent paper and welcome this opportunity to clarify our thoughts on the issues they raise. Lagroix and (Banerjee 2006) state that we have “misinterpreted” past work on paleowinds of Alaska and furthermore that considerations of temporal variability have been “cast aside.” We believe that Lagroix and (Banerjee 2006) have misinterpreted our statements about last-glacial paleowinds versus early Holocene winds in the Yukon River valley. We stated that Hopkins (1982) and Lea and Waythomas (1990) presented a picture of northeasterly winds to explain eolian sand distribution over much of Alaska during the last-glacial period. We then cited the Yukon River example of Froese et al. (2005), Holocene eolian sands on the north side of the river, as an example of how paleowinds may have changed at the end of the last-glacial period. We stated the following (Muhs and Budahn 2006, p. 324): “ If the ages are maximum-limiting estimates and if the sands were locally derived, these deposits imply sand-transporting winds from the south by the start of the Holocene”. [Italics added for emphasis]. This statement, coming after our summary of northeasterly paleowinds from Hopkins (1982) and Lea and Waythomas (1990), was intended to show not a contradiction, but a shift in winds from glacial to interglacial time. Furthermore, we do not disagree with Lagroix and Banerjee (2006) that the deposits studied by Froese et al. (2005) could have come from the north, derived from the Porcupine River. We qualified our statement about both the age and the source of the sands with the word “if,” which emphasizes the uncertainty we had at that time and still have today. Until provenance studies are conducted, the source or sources of eolian sand along the Yukon River are purely speculative. …