2021, Constantin, D., Mason, J.A., Veres, D., Hambach, U., Panaiotu, C., Zeeden, C., Zhou, L., Marković, S.B., Gerasimenko, N., Avram, A., Tecsa, V., Groza-Sacaciu, S.M., del Valle Villalonga, L., Begy, R., Timar-Gabor, A.

Loess deposits intercalated by paleosols are detailed terrestrial archives of Quaternary climate variability providing information on the global dust cycle and landscape dynamics. Their paleoclimatic significance is often explored by quantifying their mineral magnetic properties due to their sensitivity to local/regional hydroclimate variability. Detailed chronological assessment of such regional proxy records around the climatic transitions allow a better understanding of how regional records react to major global climatic transitions such as the Pleistocene-Holocene climatic transition. Logs of high-resolution magnetic susceptibility and its frequency dependence were used as paleoclimatic proxies to define the environmental transition from the last glacial loess to the current interglacial soil as reflected in nine loess-paleosol sequences across the northern hemisphere, from the Chinese Loess Plateau, the southeastern European loess belt and the central Great Plains, USA. The onset of increase in magnetic susceptibility above typical loess values was used to assess the onset of, and developments during, the Pleistocene-Holocene climatic transition. High-resolution luminescence dating was applied on multiple grain-sizes (4–11 μm, 63–90 μm, 90–125 μm) of quartz extracts from the same sample in order to investigate the timing of Pleistocene-Holocene climatic transition in the investigated sites. The magnetic susceptibility signal shows a smooth and gradual increase for the majority of the sites from the typical low loess values to the interglacial ones. The initiation of this increase, interpreted as recording the initiation of the Pleistocene-Holocene climatic transition at each site, was dated to 14–17.5 ka or even earlier. Our chronological results highlight the need of combining paleoclimatic proxies (magnetic susceptibility) with absolute dating when investigating the Pleistocene-Holocene climatic transition as reflected by the evolution of this proxy in order to avoid chronostratigraphic misinterpretations in loess-paleosol records caused by simple pattern correlation. The detailed luminescence chronologies evidence the continuity of eolian mineral dust accumulation regardless of glacial or interglacial global climatic regimes. Coupled with magnetic susceptibility records this indicates that dust sedimentation and pedogenesis act simultaneously and result in a non-negligible accretional component in the formation of Holocene soils in loess regions across the Northern Hemisphere. The luminescence ages allowed the modeling of accumulation rates for the Holocene soil which are similar for European, Chinese and U.S.A. loess sites investigated and vary from 2 cm ka−1 to 9 cm ka−1. While accretional pedogenesis has often been implicitly or explicitly assumed in paleoclimatic interpretation of loess-paleosol sequences, especially in the Chinese Loess Plateau, our luminescence data add direct evidence for ongoing sedimentation as interglacial soils formed.

2020, Müller, Katharina, Polom, Ulrich, Winsemann, Jutta, Steffen, Holger, Tsukamoto, Sumiko, Günther, Thomas, Igel, Jan, Spies, Thomas, Lege, Thomas, Frechen, Manfred, Franzke, Hans‑Joachim, Brandes, Christian

We present new evidence for neotectonic activity along the Harz Boundary Fault, a Cretaceous reverse fault that represents a key structure in northern Germany. For the fault analysis, we use a multimethod approach, integrating outcrop data, luminescene dating, shear wave seismics, electrical resistivity tomography (ERT) and numerical simulations. A recent sinkhole at the SSW-ward dipping and WNW–ESE striking Harz Boundary Fault exposes a NNE-ward dipping and WNW–ESE striking planar fault surface that cuts through unconsolidated debris-flow deposits thus pointing to young Lateglacial tectonic activity. The fault shows a polyphase evolution with initial normal fault movement and a later reactivation as an oblique fault with reverse and strike-slip components. A shear wave seismic profile was acquired to analyse the geometry of the fault and show that the Harz Boundary Fault is steeply dipping and likely has branches. Partly, these branches propagate into overlying alluvial-fan deposits that are probably Pleniglacial to Lateglacial in age. The outcrop data in combination with the seismic data give evidence for a splay fault system with steep back-thrusts. One of these back-thrusts is most likely the NNE-ward dipping fault that is exposed in the sinkhole. The lateral extent of the fault was mapped with electrical resistivity tomography (ERT) profiles. The timing of fault movement was estimated based on optically stimulated luminescence dating of the faulted debris-flow deposits using both quartz and feldspar minerals. Consistent feldspar and quartz ages indicate a good bleaching of the sediment prior to deposition. The results imply fault movements post-dating ~ 15 ka. Numerical simulations of glacio isostatic adjustment (GIA)-related changes in the Coulomb failure stress regime at the Harz Boundary Fault underpin the assumption that the fault was reactivated during the Lateglacial due to stress changes induced by the decay of the Late Pleistocene (Weichselian) Fennoscandian ice sheet. © 2020, The Author(s).