Late Pleistocene glacial chronology of the Pietrele Valley, Retezat Mountains, Southern Carpathians constrained by 10Be exposure ages and pedological investigations

Abstract

The Southern Carpathians are located in the transition zone between Mediterranean and continental climates and constituted the major areas of ice accumulation in the Carpathians during Pleistocene glaciations. An absolute glacial chronology had not yet been established. In this study we constrain the glacial history of the Pietrele Valley in the Retezat Mountains located in the Southern Carpathians and find that the timing of the late Würmian glacial advance is asynchronous to global climate records, likely reflecting changes in moisture availability in the area. The former ice extent of two major glacial advances (M1 or Lolaia glacial advance and M2 or Capra-Judele glacial advance) in the valley was reconstructed based on mapping and surveying of glacial features. Field relations and different pedological weathering indicators of till imply that the M1 glacial advance occurred well before the global Last Glacial Maximum (LGM). Its deposition during the penultimate glaciation is unlikely; no boulders suitable for exposure dating were found on M1-moraines. Seventeen exposure ages show that the moraines of the maximum late Würmian M2-glacial advance were abandoned around 16.1±1.6 ka. Another late glacial advance (M3 or Stevia advance) occurred during the Younger Dryas chron as constrained by two exposure ages. We suggest that the glacial advance that occurred during the time of the global LGM was less extensive than the M2 glacial advance and the deposits were overrun by the lateglacial M2 glacier, as we found no field evidence of glacial deposits between the M1 and the M2 moraines. We explain this obvious asynchronity of the local late Würmian ice extent with that of global records of ice accumulation with increased aridity in the Carpathians during the global LGM due to a lower sea-level. The reconstructed Late Pleistocene equilibrium line altitude (ELA) shows a distinct increase in the trend from the Alps and the Bavarian Forest to the Carpathians in comparison to the modern ELA. This finding supports the high aridity in the study area during the Late Pleistocene. Two distinct lateglacial moraines were deposited during times of reported colder and wetter climatic conditions around the North Atlantic (Heinrich-events H0 and H1).