Pleistocene climate and environment reconstruction by the paleomagnetic study of a loess-paleosol sequence (Cérna Valley, Vértesacsa, Hungary)

Abstract Four paleosol layers indicating wet and moderate periods and five loess layers indicating dry and cold climate were separated by different methods. The following climate cycle model, based on the development of the sediment sequence created by the influence of climatic, geologic and geomorphologic phenomena, was established by detailed paleomagnetic studies (e.g. anisotropy of magnetic susceptibility (AMS), isothermal remanent magnetization (IRM), frequency dependence of magnetic susceptibility (κFD), etc.): –A well-foliated magnetic fabric predominantly built up by multi-domain ferromagnetic minerals (magnetite, maghemite) was developed during the semi-arid (350–400 mm/y) and cold loessification period of the Pleistocene. The magnetic fabric can reflect the direction of dust deposition and/or the paleoslope. –The accumulation period of dust was followed by the more humid (650 mm/y) pedogenic period indicated by the enrichment of superparamagnetic minerals and by the disturbed or inverse magnetic fabric developed during pedogenesis by different processes (e.g. leaching and/or bioturbation). –The third period following the pedogenic period is the humid erosional phase indicated by the finely layered reworked loess. The magnetic fabric built up by multi-domain ferro- and superparamagnetic minerals is characterized by better-aligned directions of principal susceptibilities than in the wind blown material. Sheet wash and other waterlogged surface processes appeared in the fabric of these layers. This process is possibly connected to sudden, rare yet significant events with high precipitation and absence of vegetation. –The cycle was closed by the beginning of the next dust accumulation period

Forensic Profiling Analogue Approach for the Investigation of Natural Hazards – A Case Study from Onokoba Elementary School, Unzen Volcano, Japan

Internal temperature variations of pyroclastic flows and their deposits are arguably the most challenging data to acquire. As a preliminary study of the temperature variation inside pyroclastic flows, the remains of Onokoba Elementary School (Shimabara, Japan) were investigated. The elementary school is located in the close vicinity of Unzen volcano and was hit by one of the largest pyroclastic flows during the latest active period of the volcano on 15th of September 1991. This present preliminary study aims to determine the temperature exposure of various portion of the school building using field-forensic and urban geology. Natural hazard methods applied to the damaged materials exposed to high temperature have generated a temperature fingerprint the maximum temperature distribution. Charred wooden parts and plastic gutters installed on the schoolyard-side faced of the building turns out to be the most useful temperature indicators. The various deformation and alterations of the studied materials show significant differences in the temperature exposed to. Such differences on the second-floor section (between 75-110°C and 120-150°C) and on the first-floor section (above 435-557°C) of the building do not simply imply significant temperature heterogeneity in short distance (some ten to ≤100 m) inside the pyroclastic flow, but also points toward the possible effects of the building architecture on some key dynamic parameter of the pyroclastic flow. Such information may be important for planning future hazard mitigation actions

Enviromagnetic study of Late Quaternary environmental evolution in Lower Volga loess sequences, Russia

The late Quaternary development of the Lower Volga region of Russia is characterized by an alternating influence of marine and continental environments resulting from fluctuations in Caspian Sea level during the last glaciation. However, sediments deposited under continental conditions have received very little research attention compared to the under- and overlying marine deposits, such that even their origin is still in debate. Detailed magnetic mineralogical analyses presented here show clear similarities to loess. The results suggest that climate during the time of loess deposition, the Atelian regression (27–80 ka, MIS 4–3), was dry and cool, similar to the modern-day Northern Caspian lowland. The magnetic properties recorded in the loess-paleosol sequences of the Lower Volga also point to short episodes of potentially more humid and warmer climate during the late Atelian. The new findings in regard to the local Caspian climate and environmental evolution support decreased river discharge from the Russian Plain and Siberian Plain as the dominant factor causing the low Caspian sea level stand during the Atelian, although local-regional climate changes might have had an additional influence.The Swedish Research Council is gratefully acknowledged for funding to Thomas Stevens for part of this project (2017-03888). The work of Redzhep Kurbanov was supported by the Russian Science Foundation (grant 19-77-10077). Sofya Yarovaya was supported by the Russian Foundation for Basic Research (grant 18-00-00470). Balázs Bradák acknowledges the financial support of project BU235P18 (Junta de Castilla y Leon, Spain) and the European Regional Development Fund

The formation, alteration and significance of pyrogenic magnetic fabric in mid-paleolithic burnt cave facies

Trabajo presentado en: Magiber XI, 4-7 de septiembre de 2019, Condeixa a NovaB. Bradák acknowledges the financial support of project BU235P18 (Junta de Castilla y Leon, Spain) and the European Regional Development Fund (ERD)

Clumped isotope paleotemperatures from MIS 5 soil carbonates in southern Hungary

Quantitative paleotemperature reconstructions for the continents, including East Central Europe, over marine isotope stage 5 (MIS 5) and specifically the last interglacial (LIG, MIS 5e) are scarce and mostly based on pollen assemblages. Here we provide soil and air temperature reconstructions for the summer season of MIS 5e (5c) using carbonate clumped isotope thermometry applied to soil carbonate concretions in the Dunaszekcső loess-paleosol record, Southern Hungary. The sediments making up the S1 pedocomplex investigated represent the MIS 5 as demonstrated by bracketing K-feldspar post-IR-IRSL225/290 ages of ~63 to 164 ka. Both the absolute ages and pedogenic susceptibility (χP) curve indicate that all the subtages of MIS 5 were found to be recorded in the sequence, and soil carbonates found >1 m depth below the paleosurface of the S1 soil provide pristine, undisturbed isotopic signals. The soil carbonate concretions likely formed during MIS 5e at a relatively shallow (20–50 cm) depth, but a later formation during MIS 5c at >50 cm depth is also plausible. Clumped isotope-based soil temperatures (ST-Δ47sc) ranged from 16 to 20 °C, and reconstructed summer season air temperatures (SATs) for the LIG are consistently lower than the modern values at the site by ~1–5 °C, matching surprisingly well the soil bacteria membrane lipid-based MIS 5e air temperature estimates from a nearby Serbian site. At the same time, the reconstructed SAT values do not match the 2–4 °C positive warm season anomalies modeled for East Central Europe between LIG and present-day in paleoclimate simulations. ST uncertainties of 1–6 °C, infiltration-driven cooling of soil temperatures, and the possibility of MIS 5c formation of the investigated carbonates may account for this proxy-model data discrepancy. Oxygen isotope compositions of summer season paleo-rainwaters for MIS 5e (5c), as reconstructed using the ST-Δ47sc and δ18Osc data of soil carbonates, were found in a range of −6.7 and −6.4‰, matching the modern mean summer season value of −6.2 ± 0.94‰ within error