PROGRESSIVE SHIFTS IN INTERGLACIAL CLIMATES, DON RIVER BASIN- SEA OF AZOV, RUSSIA

1. PROGRESSIVE SHIFTS IN INTERGLACIAL CLIMATES, DON RIVER BASIN- SEA OF AZOV, RUSSIA Puterbough, J.1, Catto, N.R.1, Velichko, A.A.2,; Matishov, G.G.3, Morozova, V.P.2, Nechaev, V.P.2, Novenko, E.Y.2, Sumborski, T.V.2, Timireva, S.N.2; Rutter, N.W.4, Evans, M. E.4 1Memorial University, St. John’s; 2Russian Academy of Science, Moscow; 3Southern Research Center, RAS, Rostov; 4University of Alberta, Edmonton The lower reaches of the Don River have never been disrupted by Quaternary glaciers, and preserve a record of proglacial and interglacial loess sedimentation and soil development extending into the early Pleistocene. Extension of previous research from the Central Russian Plain to the Sea of Azov allows comparison of the record of interglacial soil sediments from the Muchkap (OIS 11?), Likhvin (OIS 9), Kamenka (OIS 7), Mikulino (OIS 5e), and the Holocene events. The soil units, interbedded with loess, provide an excellent indication of climate changes, both along a north-south transect and among interglacial events. x Moscow Uppermost part of the Semibalki exposure. Visible are the OIS 1 Dark Grey Chernozem; OIS 2-4 loess; OIS 5e (Mikulino) Grey Chernozem; OIS 6 (Dneipr) loess; and OIS 7 (Romny-Kamenka complex) soils, showing polygenetic development and a mixture of chernozemic and castenozemic characteristics. Port Katon section, showing Holocene Brown Chernozem, OIS 2-4 loess, OIS 5e, 7, 9, and 11 soils, and basal Cromerian sand and silt. Tambov x Korostelievo exposure, showing sections KS1 and KS2. Soils indicate the modern interglacial (OIS1; dark grey chernozem); a weak interstadial (OIS 3, Bryansk; regosolic brunisol); Mikulino Interglacial (OIS 5e; luvisol); Romny-Kamenka complex (OIS 7; luvisol); Likhvin Interglacial (OIS 9; grey chernozem); and the Muchkap Interglacial (OIS 11?; brown chernozem), near base of trench KS2. The basal unit is diamicton of the Don Glaciation (OIS 12), at the base of KS2. o Korostelievo o Mikhailovka Dfa-BSk ecotone vegetation flanking the Don River, Korostelievo Contrast between OIS 9 (left) and OIS 11 (right) soils, showing enhanced chemical weathering (calcareous concretions and overprinting, cutan development, and iron staining) in the OIS 11 sequence; and post-depositional frost disruption of chernozemic horizon in the OIS 9 sequence. Don R o x Rostov Port Katon Ukraine o Semibalki Sea of Azov Black Sea Sunflower field developed under BSh climate, near Port Katon Correlation diagram for composite sections, southern and central Russian Plain. OIS Interglacials and interstadials are shown in italics. The Bryansk event corresponds to OIS 3; Mikulino (Mezin) corresponds to OIS 5; Dneipr loess to OIS 6; Romny-Kamenka complex (several soils) to OIS 7; Likhvin to OIS 9; Oka loess to OIS 10; Muchkap interglacial to OIS 11 (?). The Don Glaciation may be correlative to OIS 12 or 16. Older soils are present at Mikhailovka, but Semibalki and Port Katon were inundated by marine waters during the Cromerian. Probosidian tusk derived from nearshore marine/deltaic sediment, Cromerian horizon, Port Katon. Speciation is being undertaken by RAS specialists. Modern climates in southern European Russia vary from cold steppe-boreal transition (Koppen-Geiger Bsk-Dfa) at Korostelievo, to warm steppe (BSh) at Semibalki. Chernozemic soils are dominant in the modern landscapes, transitional to luvisols in forested areas. Castenozems are not present. Seasonal frost features were not recognized in any of the modern soils investigated. Differences exist between interglacials: the early interglacials show stronger Mediterranean influences, especially along the Sea of Azov. In contrast, OIS 5e and Holocene successions are dominated by westerly (Atlantic) circulation in the north, and the Sea of Azov successions also show increased effects from westerly and northwesterly (Atlantic) winds in the younger interglacial deposits. Basal part of the Mikhailovka exposure, with Don Glaciation diamicton at upper surface. A sequence of three loess-soil events overlies the Palaeogene and Cretaceous chalk (white horizon). Soils show extensive iron-staining and cutan development, and resemble modern Mediterranean soils and Castenozems. These successions parallel results obtained in the Altaisk region of Siberia, where a progressive shift from southerly winds during OIS 5e and OIS 4 to westerly winds during OIS 2 and OIS 1 has been observed. The overall pattern suggests that westerly winds have become progressively more dominant in the Central and Southern Russian Plain, both with respect to soil development and loess deposition, since OIS 11. The soil-loess successions show a progressive shift from Mediterranean dominated climate patterns, with warm, dry southwesterly winds, to colder northwesterly and Atlantic-influenced winds. As expected, soil development shows a progression from Mediterranean assemblages along the Sea of Azov, especially in the older interglacials, to soils developed under boreal and taiga forests in the north. Microphotographs of Holocene Chernozem (left) and OIS 7 soil (right, Semibalki. The OIS 7 soil shows extensive cutan development, calcareous overgrowths, and higher concentrations of heavy minerals. These characteristics suggest development under enhanced biochemical weathering, with periodic wetting and drying, and mineral input from southwesterly winds. The tendency for increased Mediterranean influence in earlier interglacial periods is evident in the OIS 7, 9, and 11 soils at Semibalki and Port Katon, with Castenozem characteristics more prevalent in the older soils. Basal Cromerian marine sand, Semibalki Acknowledgements: We thank all our colleagues and everyone who helped in Azov City, Edmonton, Moscow, Rostov, and St. John’s. Ted Little and Kostya Dlussky, in particular, contributed greatly to establishing the loess-soil succession in the north-central Russian Plain. Disruptions of soil horizons by seasonal frost activity are evident in the OIS 5e (Mikulino) soils at Korostelievo, Mikhailovka, and Semibalki. At Korostelievo, some deformations appear penecontemporaneous with soil development, suggesting a frost-influenced environment. Frost disruptions of the OIS 5e soils at Mikhailovka and Semibalki, and in the OIS 9 and 11 soils at all sites, are epigenetic. Comparison of OIS 5e soils between the four sites indicates a gradient between southern boreal conditions at Korostelievo (luvisol), to cool steppe at Mikhailovka (illustrated), to warm steppe at Semibalki and Port Katon (grey-brown chernozems).