A Dráva durvaszemcsés folyóvízi üledékéből előkerült szubfosszilis uszadékfák dendrokronológiai és faanatómiai vizsgálata

Abstract

This paper presents preliminary results of dendro-chronological analyses of the first occurrence of subfossil tree trunks from drava alluvial sediments. Driftwood logs were found at an outer bend of the Drava river near the village of Babócsa. The site is covered by >6 m fluvial sand and gravel. Trunks are arranged horizontally, roughly in the same bed, between massive gravel and sand layers.. Fourteen samples had been collected within a hundred metre long outcrop, ar-ranged in three distinct sets.. half of the samples are oak (Quercus roburl., n=7), fewer samples belonged to beech (Fagus sylvatica, n=2), wych elm (Ulmus scabra, n=1), eu-ropean white elm (Ulmus laevis, n=2) and finally a there are one sample each of poplar (Populus spp.) and larch (Larix decidua). the samples were processed following the stan-dard dendrochronological protocol. ring width was measured to the nearest 0.01mm. despite the most likely origin of the samples is the riverbank; the oak trunks had narrow tree-ring sequences. an oak trunk of a diameter not more 20 cm con-tains more than 240 rings and two other oak samples have about 200 rings. These three long series could be crossdat-ed, forming a 249 year long chronology. The chronology built from the three synchronized records (sample codes bab002, bab003, bab007) was tested with surrounding oak master chronologies, without success. The first subfossil wood re-mains from the drava river and their loating chronology will be of help to understand changes in river dynamics and the former composition of the tree species on the floodplain.