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06 février 2019
Une accumulation remarquable de loess datée du Saalian tardif à Harletz (Bulgarie) dans le Bas Danube
Une accumulation remarquable de loess datée du Saalian tardif à Harletz (Bulgarie) dans le Bas Danube

Detailed stratigraphic log of the Harletz profile including the location of the various luminescence and micromorphological samples (blocks). High-resolution grain size data (clay, coarse and fine sand, grain-size ratios (GSI and CSI), TOC, carbonate, mass-specific magnetic susceptibility (cBULK in 10_8m3/kg) and absolute frequency dependence of mass-specific magnetic susceptibility (DcFD in 10_8m3/kg), colour reflectance data and luminescence dating results from Lomax et al. (2019)) (black: feldspar coarse grain fraction, applying the MET-pIRIR protocol, grey italics: quartz fine grain fraction and SAR protocol).

While numerous high-resolution studies concerning Last Glacial aeolian sequences are available for Europe, the approach of the penultimate glacial in this geographical area is still poorly developed. In order to bridge this gap, this study focuses on the Bulgarian sequence of Harletz, along the Danube River, where extremely high sedimentation rates allow the depiction of high-resolution signals during MIS 6. At Harletz in NW Bulgaria on the western bank of the Ogosta River (tributary of the Danube) a 20m thick loess-palaeosols section was cleaned and sampled for a multi-disciplinary study and detailed pedostratigraphic approach. High-resolution continuous bulk sampling (5 cm) was carried out to characterise sedimentary grain size, magnetic properties (including magnetic susceptibility and its frequency dependence), colour reflectance (1 cm), and organic carbon. Geochronological control is based on 16 samples collected for OSL and MET-pIRIR dating. Using a cyclo-stratigraphic approach of the sequence combined with dating constraints provided by both MET-pIRIR dates and the age of a tephra layer occurring at a depth of 12m within the main loess unit, we can demonstrate that the Harletz section exhibits a 10m thick Late Saalian (Marine Isotope Stage 6, MIS 6) loess accumulation unique in Europe. The lower part of the main loess unit is 4m thick and overlies a basal brown soil complex allocated to MIS 7, which includes an exceptionally thick (4 m) and detailed succession of loess and four incipient soil horizons never described in European loess until now.
Référence : Antoine P., Lagroix F., Jordanova D., Jordanova N., Lomax J., Fuchs M., Debret M., Rousseau D.-D., Hatté C., Gauthier C., Moine O., Taylor S.N., Till J.L., Coutard S., 2019. A remarkable Late Saalian (MIS 6) loess (dust) accumulation in the Lower Danube at Harletz (Bulgaria). Quaternary Science Reviews 2017, 80-100. Doi : 10.1016/j.quascirev.2019.01.005

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