Environmental conditions at the Last Interglacial (Eemian) site Neumark‐Nord 2, Germany inferred from stable isotope analysis of freshwater mollusc opercula

Abstract

Mollusc biogenic carbonates are valuable records of past environmental conditions. In particular, carbonate oxygen (δ18O) and carbon (δ13C) stable isotopes can be used to reconstruct different physical and chemical parameters, according to the different genera used (marine, freshwater or terrestrial). The Last Interglacial (early Eemian) palaeolake of Neumark‐Nord 2 (NN2), Germany provides an excellent example of a Neanderthal archaeological site with abundant freshwater carbonate remains. As in other European contexts, one of the most abundant species is Bithynia tentaculata. In order to provide a robust regional baseline for the interpretation of the archaeological data, this study includes a calibration phase on modern B. tentaculata opercula. The results indicate that these calcitic structures are likely to be subjected to a growth slowdown/cessation during summer, which influences their geochemistry, reflecting mainly the water properties of the rest of the year. This modern calibration, together with the existing palaeoenvironmental reconstructions developed for NN2 (e.g. pollen data), represents a valuable opportunity to establish B. tentaculata opercula as reliable environmental proxies applicable to several other freshwater contexts. The isotope data of the NN2 opercula, in agreement with the pollen record, indicate that the major archaeological horizon was formed during a rather wet period and potentially in a semi‐forested environment. However, human occupation occurred also during drier phases at the site and within a wide temperature range, indicating the absence of restricted environmental preferences by the local Neanderthal groups.

Landscape modification by Last Interglacial Neanderthals

“…Data regarding rainfall and temperature during the period of Neanderthal presence at Neumark-Nord 2 come from stable isotope analysis of freshwater mollusk opercula (41) and are in agreement with the results from the oxygen isotope analysis of horse tooth enamel from the Neumark-Nord 2 site (59), which has yielded mean annual temperature estimates for the Last Interglacial. The Mitteldeutsches Trockengebiet in which Neumark-Nord is situated has a mean annual temperature of ~9°C (60) and is in an area of the German "isoscape" with annual average rainfall δ 18 O values between −8.7 and − 9.4 ‰ [see Fig.…”

“…3, (45,(48)(49)(50)]. Our expectation that rainfall and temperature will not differ between sites in the study region is partially confirmed by data from one of the baseline sites, Gröbern, where the temperature history of the Eemian has been reconstructed by palynology and by the bulk carbonate d18O record from that basin (62,63), both methods indicating very similar temperature histories for Gröbern and Neumark-Nord, with temperatures reaching a maximum at both sites during PAZ IVb and remaining stable during PAZ V [see also (41)].…”

“…Both basin structures formed in Saalian till deposits and subsequently filled up with fine-grained Last Interglacial sediments ( 35 ): The Neumark-Nord 1 basin’s infill consisted predominantly of silt loams and peat deposits reaching a total thickness of 15 m, while the more clastic infill of the shallow pool Neumark-Nord 2 reached a total thickness of 10 m. A section in the deeper part of the Neumark-Nord 2 basin, Hauptprofil 7 (HP7), was continuously sampled for a multidisciplinary study of the basin infill, which included micromorphology ( 36 ), pollen analysis ( 37 , 38 ), paleomagnetism ( 28 ), small mammal studies ( 39 ), and malacology ( 40 ), with a recent study using oxygen and carbon stable isotopes of Bithynia tentaculata opercula from the section as a new type of environmental proxy ( 41 ). The sediments containing the environmental data can be clearly related to the occupations recorded by the archaeological data.…”

Tracking Hunter-Gatherer Impact on Vegetation in Last Interglacial and Holocene Europe: Proxies and Challenges

“…The Neumark archaeological record contains high-density evidence for flint knapping, animal exploitation and fire use (at NN2) as well as low-density single activity death or kill sites, mostly accumulated during the first 7,000 years of the Eemian. Comprehensive coverage of the Neumark palaeoecological and archaeological studies are assembled in Mania et al (1990), Mania (2010), Meller (2010), Gaudzinski-Windheuser and Roebroeks (2014), Gaudzinski-Windheuser et al (2018) and Kindler et al (2020) (for various detailed studies of a wide range of proxies from Neumark-Nord, see Mania, 2010;Meller, 2010;Bakels, 2012Bakels, , 2014Britton et al, 2012Britton et al, , 2019García-Moreno et al, 2016;Milano et al, 2020).…”