The Late Pleistocene Belotinac section (southern Serbia) at the southern limit of the European loess belt: Environmental and climate reconstruction using grain size and stable C and N isotopes

摘要

The Belotinac loess section is one of the southernmost loess-paleosol environmental archives for the Late Quaternary in Serbia. The climate at this site is intermediate between the continental and the Mediterranean realms, which makes this loess archive potentially highly sensitive to past climatic changes. This paper presents new insights into the paleoenvironmental history during the last glacial period in southern Serbia using grain size and isotope proxy data. The grain size parameters from the Belotinac section reveal variations in the paleowind dynamics and weathering intensity, and suggest the nearby valley of the Juzna Morava River as an important source of aeolian sediments in this area. Based on a multiproxy dataset, alternating phases of weak interstadials and phases of enhanced loess deposition at this site were identified. Nitrogen isotope data suggest that during Marine Isotope Stage 3, ecosystems of high biomass productivity and rather open N-cycles prevailed. During Marine Isotope Stage 2, productivity was reduced and the N cycle was more strongly closed, probably due to a shorter growing season and more pronounced temperature decline. Carbon isotope data indicate a possible contribution of C_4 plants to the Holocene vegetation, but not to the glacial and interstadial ecosystems of the Late Pleistocene. Changes in atmospheric CO_2 level are not reflected in the carbon isotope record. These findings are discussed in the light of paleoclimate proxy datasets from the Morava River valley and Carpathian Basin, as well as through comparison of carbon isotope records from loess sections in SE-Central Europe and in the Rhine Valley. Two different loess provinces exist in terms of glacial-interglacial humidity changes: a province of "glacial drying" and a province of "glacial humidification". The first includes loess sites under more oceanic influence, where loess δ~(13)C records indicate humid interglacials and interstadials and relatively drier glacial periods. The second includes the loess sites of the Carpathian Basin and especially the southern Serbian loess area of Belotinac, where loess δ~(13)C records indicate more intensive aridity during interglacials, but a reduced soil moisture deficit and a more humid climate due to lower evapotranspiration in interstadials, and even more in glacial periods.