Osl Dates and Heavy Mineral Analysis of Upper Quaternary Sediments from the Valleys of the Ér and Berettyó Rivers

The study of the evolution of the river network in the Great Hungarian Plain has been based on sedimentological, neotectonical, morphological investigations, heavy mineral analysis and complementary OSL dating. The study area extends from the Koros sub-basin into the Er and Beret- tyo river valleys which are situated northeast from the subsiding basin and northwest from the uplift- ing Apuseni Mountains. The OSL ages provide evidence that a large river run in the Er-valley at least from 46±4 to 39±4 ka. It deposited garnet and magnetite-ilmenite-rich sediments, similar to the recent Berettyo, Er and Sebes- Koros rivers and less intensive the modern Tisza river. These sediments originated from the nearly lo- cated metamorphic and Neogene volcanic rocks and contain some reworked older clastic sedimentary rocks from the northern part of the Apuseni Mountains. These OSL ages fit the active tectonic phase of the Ermellek depression. Loess is 49-47, 44, 39 and 25 ka old and aeolian sands 10 to 9 ka were dated. Their heavy mineral composition and that of fluvial sands is similar.