Loess in Armenia
Final Report Abstract
Loess-Palaeosoil sequences enable a detailed reconstruction of past environmental and climatic conditions. However, especially in the transition area between SE-Europe and Central Asia/ N-Iran that is characterized by strong climatic and landscape gradients, there is a significant research gap in loess research. In the frame of this project, we were able to develop a reliable stratigraphic standard loess-section for the Southern Caucasus based on the detailed work on four individual loess sections. Several sections show a high stratigraphic differentiation that strongly correlate with each other. Based on intensive luminescence dating (pIRIR), nearly each stratigraphic position could be provided with temporal information. For example, strongly developed palaeosoils could be linked to interglacial or interstadial periods of incipient cold stages. Detailed gastropod and n-alkane analyses revealed valuable proxy information on past ecological and climatic conditions. This, together with a provenance study based on XRF and rock-magnetic measurements, enabled a reliable reconstruction of the processes of loess formation in the study area. We identified the fluvial sedimentation basin of the Kura depression as most relevant loess source. Several proxy information point to semi-desertic conditions during phases of loess formation. Thus, we conclude that loess formation in that area was mainly related to hycric aridity instead of cold temperatures. That means that loess formation is very similar to that of the Western Mediterranean. Phases of lacking or strongly reduced loess deposition suggest the presence of long grass steppe or forest steppe as dominant vegetation form. Interstadial periods during MIS-4 and MIS-3 were related to short grass steppe. The highly resolved dating of the loess sequences revealed that phases of loess formation during the last glacial period can most probably be correlated with stronger dynamics of the Siberian high-pressure area. However, during MIS-2 that is characterized by maximum loess deposition in many other areas, no or just little loess was deposited in the Southern Caucasus. Through intensive consultation of regional comparative archives, we suggest that this phenomenon presumably relates to a higher moisture supply from the Black Sea due to southward shifted westerlies during MIS-2. In general, weaker interstadial soils of the loess sequences show also high clay contents of partly more than 30%. Based on proxy information, we do not assume climatically moister phases as mean reason, but the fast formation of amorphous clay minerals because of the weathering of volcanic glasses incorporated into the loess (background contents of about 10 to 20%). This volcanic character is visible in element contents as well and clearly differentiates the Southern Caucasian loess from other Eurasian loess occurrences. In summary, including intensive stratigraphic work, the development of suitable proxy data and the dating of highly demanding volcanic material, this project succeeded in exploiting a valuable environmental archive for the middle to late Pleistocene period in the Southern Caucasus.
Publications
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(2019). First Calibration and Application of Leaf Wax n-Alkane Biomarkers in Loess-Paleosol Sequences and Modern Plants and Soils in Armenia. Geosciences 9 (6), 263
Trigui, Y., Wolf, D., Sahakyan, L., Hovakimyan, H., Sahakyan, K., Zech, R., Fuchs, M., Wolpert, T., Zech, M., Faust, D.
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(2020). New Insights into Southern Caucasian Glacial-Interglacial Climate Conditions Inferred from Quaternary Gastropod Fauna. Journal of Quaternary Science 35 (5), 634–649
Richter, C., Wolf, D., Walther, F., Meng, S., Sahakyan, L., Hovakimyan, H., Wolpert, T., Fuchs, M., Faust, D.
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(2021). Establishing a luminescence-based chronostratigraphy for the last glacial-interglacial cycle of the loess-palaeosol sequence Achajur (Armenia). Frontiers in Earth Science 9
Lomax, J., Wolf, D., Wolpert, U. T., Sahakyan, L., Hovakimyan, H., Faust, D., Fuchs, M.
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(2022). Testing post-IR-IRSL dating on Armenian loess-palaeosol sections against independent age control. Quaternary Geochronology 69, 101265
Lomax, J., Wolf, D, Meliksetian, K., Wolpert, T., Sahakyan, L., Hovakimyan, H., Faust, D., Fuchs, M.
