High-resolution reconstruction of the hydroclimate and palaeoenvironment of the last 5500 years in the Apuseni Mountains (NW Romania)

In the present study, we analyzed an ombrotrophic peat sequence from NW Romania using a multi-proxy approach (lithology, radiocarbon dating, loss on ignition, magnetic susceptibility, testate amoebae and plant macrofossil) in order to reconstruct the environmental and hydroclimate changes that occurred in the last 5500 years.

The studied sequence (Molhașul Mare de la Izbuc, Apuseni Mountains) started to accumulate in 5520 cal yr BP, debutting with a lacustrine phase and evolving into an ombrotrophic Sphagnum peat bog. The palaeoenvironmental stages of the peat bog were confirmed by the lithology, loss on ignition and magnetic susceptibility results. A pan-european testate amoebae-based transfer function was used for the quantitative reconstruction of the water table levels in the peatland. The depth to water-table (DWT) values ranged between 7.3 and 28.5 cm, suggesting wetter conditions in the first 2500 years of the sequence and drier ones between 2500 cal yr BP and the present days. The occurred hydrological shifts and the changes of the surface wetness were also confirmed by the plant macrofossil analyses.

We identified and assessed the local effects of several rapid climate change events that occurred in Europe such as the Piora Oscillation, Middle Bronze Age Cold Event, Iron Age Cold Event, Roman Climate Optimum, Dark Age Cold Event, Medieval Warm Period, Little Ice Age, Great Famine in Europe, the Sporer, Maunder and Dalton Minimum Events and the Year Without Summer.

Our high resolution study is among the few quantitative DWT reconstructions in Romania. Our results contribute to obtaining a broader image and a better understanding of the palaeoenvironmental, palaohydrological and palaeoclimate changes in Romania and in Central Eastern Europe during the past 5500 years.