Clumped isotope paleotemperatures from MIS 5 soil carbonates in southern Hungary

Újvári, Gábor and Kele, Sándor and Bernasconi, Stefano M. and Haszpra, László and Novothny, Ágnes and Bradák, Balázs (2019) Clumped isotope paleotemperatures from MIS 5 soil carbonates in southern Hungary. Palaeogeography, Palaeoclimatology, Palaeoecology, 518. pp. 72-81. ISSN 0031-0182

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Abstract

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.

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