Results of paleoecological studies in the loess region of Szeged-Othalom (SE Hungary)

摘要

New results of sedimentological, Magnetic Susceptibility, geochemical, radiocarbon and malacological analysis from a typical and an infusion loess section are presented from SE Hungary. The geologic and geomorphologic value of the area is that aeolian (typical) loess accumulated on sand dunes that formed during MIS3, while in the interdune depressions on the top of lacustrine deposit series, infusion loess developed. As the two types of loess interfinger, it is the first demonstration that the two types of loess formed during the same time period (isochron) in different environments (heterotype). At the end of MIS3 and during MIS 2 between 33,000-13,000 cal BP, a temperate steppe-forest steppe environment characterized the loess surface of the SE Great Hungarian Plain. During the first interstadial phase of MIS2 a Pinus sylvestris charcoal rich paleosol layer developed on the loess covered surface of a wind-blown sand hummock, while in the interdune depressions a pond phase developed. After the formation of the paleosol layer on the surface of the loess covered wind-blown sand hummock during the Heinrich 2 event, Vertigo modesta-Vallonia tenuilabris indicate a cold steppe-forest steppe environment and a deeper and colder lake phase in the interdune depressions. After that, a short microinterstadial phase developed and a Pupilla triplicata-Chondrula tridens dominated temperate steppe-forest steppe environment evolved on the terrestrial surface between 23,000 -21,000 cal BP. After 21,000 cal BP, in the Last Glacial Maximum (LGM) the environment completely changed. The average dust accumulation accelerated and coarse silt (0.02-0.06 mm) became dominant. As a result, the lake stage transformed to a marshy environment, while on the land area shade-loving, including closed forest environment-preferring mollusca taxa appeared, such as Vestia turgida, Vitrina pellucida and Mastus venerabilis. Based on the mollusca fauna composition, humidity increased during the cooling of the LGM horizon, forestation started and a boreal forest-steppe evolved at the study site. During the post LGM, the interdune depressions filled and aeolian loess layers developed. Formation of the infusion loess occurred between 24,000-17,000 cal BP. Loess formation lasted until the beginning of the Late Glacial Maximum (Last Permafrost Maximum) and ended in a forest steppe environment with boreal, Central European, holarctic, palearctic and continental mollusc fauna elements. (C) 2014 Elsevier Ltd and INQUA. All rights reserved.