Palaeowind directions and sources of detrital material archived in the Roxolany loess section (southern Ukraine)

Abstract

Measurements of the anisotropy of whole-rock magnetic susceptibility (AMS) and U-Pb ages of detrital zircons have been combined to define the palaeowind directions and sources of wind-blown dust in the loess-palaeosol key section at Roxolany (southern Ukraine). Zircon dating has also been used to determine the age and provenance of the interbedded Roxolany tephra. The distribution of AMS axes in the loess indicates that the prevailing wind during its accumulation blew from the north-west, the same as the mean present-day summer wind direction measured in the nerby city of Odessa. The U-Pb isotopic ages of the detrital zircons mostly range between 0.25 and 2 Ga, with clusters at 0.28, 0.32, 0.45, 0.58, 1.0 and 1.5 Ga. Single Neoarchean grains (ca. 2.7 Ga) were also found. These ages indicate that material from Carpathian and Podolian sources formed the Roxolany loess. This material initially was transported by the Dniester River, then was wind-blown form the Dniester liman and the lower Dniester valley, located NW of Roxolany. Most of the pyroclastic zircons from the Roxolany tephra gave ages of 470–840 ka, with a peak between 500 and 750 ka. This age range is consistent with their being derived from the Ciomadul volcano in Romania. Show more