Pedosedimentary division, rock magnetism and chronology of the loess/palaeosol sequence at Roxolany (Ukraine)

The loess mantle of the Vm Dniestre terrace at Roxolany in the Black Sea area of Ukraine is subdivided into six units, which encompass the following palaeosol taxons: pedocomplexes (PK) with evidence for several soil-forming and sedimentary episodes; incipient monogenetic palaeosols; and horizons of carbonate concretions. These cyclical loess-palaeosol units provide a depositional record from the end of the Matuyama chron through the Holocene. The detailed pedosedimentary subdivision of loesses at Roxolany is generally consistent with magnetic susceptibility depth functions and seems to reflect global climatic variations. Earlier chronologies [Guidebook of the International Geological Congress. XXVII Session, 1984] are re-estimated on the basis of a revised position of the Matuyama-Brunhes boundary and by detailed rock magnetic and micromorphological studies. The strongly developed chernosem of PK4 at approximately 22 m depth, showing features of rubefication and the highest magnetic susceptibility value, is viewed as a good stratigraphic marker of the Late Cromerian and seems to represent the climatic optimum of the Brunhes chron (oxygen isotope stage 13?). The uppermost PK2 is represented in the lower part by a chernosem analogous to surface soils of the area and is argued to be no younger than the Last Interglacial (oxygen isotope stage 5e). The poor preservation of PK2 seems to result from processes of soil degradation and deflation at the time of interglacial-glacial transition. The closely spaced palaeosols between PK2 and PK4 seem to relate to three independent interglacials. Highest resolution of the palaeoclimatic record is found at the final Matuyama chron from PK9 to PK8 and in incipient soils that contain either humic horizons with enhanced magnetic susceptibility or only horizons of large carbonate concretions. (C) 1998 Elsevier Science B.V. All rights reserved.