Tectonic, climatic and autogenic controls on the Late Quaternary evolution of the Somes fluvial fan, North-East Pannonian Basin, Central Europe

The Somes fluvial fan is located in the NW extremity of the Great Hungarian Plain (Pannonian Basin). It was formed by the left-side tributaries of the Tisa River (a tributary of the Danube) as they developed westward, following the avulsion of the main Tisa channel. Drainage reorganisation after the avulsion has occurred via a complex interplay between tectonic, climatic and autogenic controls over the past similar to 50-30 ka. In this study, we discuss the role of these factors in the spatial and temporal dynamics of the fluvial system that constructed the Somes fluvial fan during the second half of the last glacial cycle, using a combination of cartographic, sedimentary, and chronological tools. Our data suggests that, within a general setting of subsidence, spatial and temporal variation in the rate of this subsidence between different tectonic blocks created four local base levels, while autogenic factors play only a secondary role. The modern drainage configuration results from spatial channel adjustments during the last ca. 3000 cal BP, related to the current subsidence centre located in the NW extremity of the Somes fluvial fan. Over the entire period analysed, the rivers draining across the fluvial fan predominantly meandered, except when the river switched to a braided pattern. This braided phase likely occurred before similar to 30-32 ka ago, apparently coeval with a similar short, braided phase that has been documented along the middle Tisa River. The braiding phase is coincident with intense deglaciation in the Somes catchment area and development of open forest vegetation at lower elevations. Climatic changes during and after the Last Glacial Maximum had a reduced impact on the style of fluvial flow, which returned to a meandering pattern. Ca. 5000 cal BP these changes impacted suspended sediment delivery to drainage networks resulting in the present-day channel dimensions, at least along their lower reaches (our study area). Our results highlight the lower sensitivity of rivers draining the Great Hungarian Plain to the Late Quaternary climate changes compared to the far more responsive rivers of Western European. This behaviour is, in our opinion, most likely due to the presence of glacial forest refugia in the catchment areas, which modulated the response of discharge and fluvial dynamics to climatic changes

A Comparison of Methods Used for the Calibration of Radiocarbon Dates

From the 13th International Radiocarbon Conference held in Dubrovnik, Yugoslavia, June 20-25, 1988.Current calibration methods for single and replicate 14C dates are compared. Various forms of tabular and graphic output are discussed. Results from all the methods show reasonable agreement but further methodological development and improvements in computer output are required. Comparison of existing techniques for a series of non-contemporaneous dates showed less agreement amongst participants on this issue. We recommend that calibrated dates should be presented as a combination of graphs and ranges, in preference to mean and standard deviation.This material was digitized as part of a cooperative project between Radiocarbon and the University of Arizona Libraries.The Radiocarbon archives are made available by Radiocarbon and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform February 202