Eemian Optimum Research Articles

Des passages discrets mais récurrents de néandertaliens à waziers le bas‑terroir : un nouveau gisement archéologique du tardiglaciaire du SIM 6 a l’optimum eemien (SIM 5e) dans le nord de la France

Des passages discrets mais récurrents de néandertaliens à waziers le bas‑terroir : un nouveau gisement archéologique du tardiglaciaire du SIM 6 a l’optimum eemien (SIM 5e) dans le nord de la France

Waziers le Bas-Terroir (plaine de la Scarpe, nord de la France) : synthèse des études sur les observations 2011-2015 et mise en évidence d’un enregistrement sédimentaire continu de la fin du saalien (SIM 6) à l’optimum eemien (SIM 5e).

Waziers le Bas-Terroir (plaine de la Scarpe, nord de la France) : synthèse des études sur les observations 2011-2015 et mise en évidence d’un enregistrement sédimentaire continu de la fin du saalien (SIM 6) à l’optimum eemien (SIM 5e).

Two pollen-based methods of Eemian climate reconstruction employed in the study of the Żabieniec-Jagodne palaeolakes in central Poland

The aim of the present study was to estimate the range of climate variability in Central Poland during the Eemian Interglacial (MIS 5e). High resolution pollen records are available for all seven RPAZs typical of this interglacial in Central Europe. These pollen records were used to estimate total annual precipitation and mean annual temperature, as well as the mean temperatures of the warmest and the coldest months based on the plant indicator method and the modern analogue technique. The reconstructions indicate that the combination of these two methods provides a much clearer insight into the climate changes of the Eemian optimum. The results confirmed no drastic drop in temperature in the Middle Eemian, with high total precipitation in the hazel phase, and that this was followed by a decrease in temperature in the Late Eemian (fir-spruce and pine phases). A drop in precipitation occurred during the youngest part of the Carpinus phase, while coincided with a marked lowering of the water level in lakes and their transformation into peatbogs. The last part of the Eemian is characterized by decreasing temperature, particularly during the coldest month, rising water levels due to a combination of lower evaporation and higher air humidity, and a transition to glacial conditions. Principal Component Analysis found all investigated sites to follow the same pattern of changes. Mean winter temperature, annual temperature and precipitation were found to have a strong positive correlation with the occurrence of thermophilus temperate broadleaved trees (hazel, linden, and ash) typical for the mid-Eemian optimum. These three factors also have a negative correlation with the presence of cold tolerant boreal trees (birch and pine) and open land taxa characteristic of the beginning and end of the interglacial. Mean July temperature was found to be positively correlated with the occurrence of temperate broadleaved trees (oak, ash and elm) typical for early stages of the Eemian and negatively with that of coniferous trees (fir and spruce) characteristic for later stages of the interglacial.

Was there an abrupt cold climatic event in the middle Eemian? Pollen record from a palaeolake at the Hieronimowo site, NE Poland

Seventy samples of lacustrine sediments from a palaeolake at the Hieronimowo site, NE Poland were investigated by pollen analysis method. The obtained results indicate that the examined sequence spans the whole Eemian Interglacial (MIS 5e), the beginning of the Early Vistulian (Weichselian; MIS 5d) and some undefined period of the Plenivistulian (Middle Weichselian; MIS 2-4). The specific feature of the studied profile is the great thickness of deposits representing the hornbeam phase of the Eemian Interglacial (E5 R PAZ), which was the younger part of the climatic optimum of this interglacial, and the very well developed pollen record of this phase, that is absent in other profiles in NE Poland. Due to this, our study allowed, for the first time in NE Poland, the detailed reconstruction of changes in the vegetation and in the mean January and July temperature during the middle part of the Eemian Interglacial. This reconstruction unequivocally rules out the existence of an abrupt short-lasting cold event at that time. Only a gradual slight increase in temperature was apparent during the older part of the hornbeam phase (to >21 °C for July, and to >0 °C for January) and gradual decrease during its younger part (to >17 °C for July, and to > -5 °C and <-2 °C for January). So during the warmest part of the hornbeam phase, reconstructed temperatures for July were similar as in older part of the Eemian optimum (hazel phase, E4 R PAZ), however they were approximately 2 °C higher for January.

Vipera berus (Linnaeus, 1758) remains from the Late Pleistocene of Slovakia

Completely preserved specimens of fossil snakes are extremely rare and ophidian palaeontologists are usually dependent only on disarticulated elements of a postcranial skeleton. Here we present an unusually well-preserved specimen of a small viperid snake from the Late Pleistocene firm travertine at the famous Gánovce-Hrádok Neanderthal mound in Slovakia. The complex study of both cranial and axial skeleton with well-preserved maxilla and basiparasphenoid confirms the presence of a viper from theVipera berusspecies group, and recent distribution ofV. berusspecies complex members supports identification of these preserved remains as belonging to the common adder,V. berus(Linnaeus, 1758). Associated faunal assemblages of the MFG-C and D mammalian fauna groups reported from the firm travertine indicate a humid climate in a predominantly woodland environment with typical forest species in the Gánovce-Hrádok vicinity throughout the Eemian optimum, and mixed forest and steppe environments in the late Eemian to early Weichselian stages. Occurrence ofV. berusdocuments the presence of open or semi-open biotopes with low vegetation. AlthoughV. berusoccurs in the Quaternary glacial/interglacial cycle and throughout the entire warm part, it never dominated herpetofaunal assemblages during the climatic optimum. Therefore, the presence ofV. berusmost likely indicates late Eemian or early Weichselian (interstadial) climatic conditions.

Reaction of lake environment on the climatic cooling – Transition from the Eemian Interglacial to Early Vistulian on the basis of Solniki palaeolake sediments (NE Poland)

Results of Cladocera and organic matter analyses from the Eemian lake deposits in Solniki (NE Poland) are presented. We focused on the reaction of the lake's environment to progressive cooling reflected in the changes of the organic matter and the Cladocera community. Approximately 3-m of sediments accumulated from the optimum of the Eemian Interglacial (E5) to the Early Vistulian (EV2) were analyzed. Results of analyses of organic matter correlated with Cladocera data enabled a reconstruction of varying environmental conditions and geneses of organic matter. The organic carbon content is closely related to climatic conditions. The lowest values are recorded in the coldest periods during the ending of the Eemian Interglacial and the Herning stadial of the Early Vistulian. The highest ones occur unexpectedly in the Eemian post-optimum: at the end of the spruce phase and at the beginning of the pine phase.During the Eemian optimum (E5), biodiversity of Cladocera species was maximal (17), but the frequency of specimens was low. At the end of the optimum (E5), an improvement of living conditions, more optimal for various ecological groups of Cladocera took place. Algae remained a significant component of organic matter. The early Eemian post-optimum (E6) is characterized as a period of the high number of zooplankton species, the highest frequency as well as biodiversity. At that time, probably a higher water level and an optimal temperature formed very favorable conditions for the fauna development. During this period, maximal values of TOC, TN and the slight increase of C/N ratio suggest a higher primary productivity with a small supply of organic matter of terrestrial origin. Coexistence of two species of the family Bosminidae and maximum values of δ15N suggest a high trophy (β-mesotrophy). High resolution and detailed analyses of the lake sediments accumulated during the pollen zone E7, allowed to identity a few minor environmental fluctuations recorded in varied Cladocera frequency, TOC and C/N ratio. In the final period of the Eemian Interglacial and in the Early Vistulian (Herning stadial), a drastic reduction in frequency of Cladocera and the features of OM (the lowest amounts of TOC and TN, and the highest value of C/N) reflect the decline of lake conditions and a lack of both primary production and aquatic vegetation in the lake. During the Amersfoort interstadial a renewed bioproduction and slightly supply of terrestrial plants in organic matter as well as revitalize zooplankton took place.

Eemian environmental changes recorded in lake deposits from Rzecino (NW Poland): Cladocera, isotopic and selected geochemical data

Analysis of Cladocera and organic matter from the sediments of the Rzecino paleolake are presented. These are probably among the first detailed published data from the Eemian Interglacial (MIS 5e) organic matter. The Rzecino paleolake is located in NW Poland in an area covered by the last glaciation. Approximately 5.8 m of sediment was analyzed. Previous palynological data indicate a continuous accumulation from the final phase of the Wartanian to the early Vistulian Glaciation. Data on the Cladocera correlated with the results of the analyses of organic matter, which enabled the reconstruction of varying environmental conditions and geneses of organic matter. In the final phase of the Wartanian and at the beginning of the Eemian Interglacial, low frequencies of Cladocera specimens and species were identified, which suggests unfavorable conditions for the development of zooplankton. Organic matter (OM) was characterized by a small amount of organic carbon and nitrogen, a high value of C/N (18–27) and a δ13C of approximately −26 ‰, which suggests a higher plant source and a predominantly terrestrial origin for OM. An improvement in environmental conditions occurred during the pollen zone E3. The number of Cladocera species and individuals increased. An increase in TOC and TN suggests an enhancement of primary productivity and the development of macrophytes in the lake. A lower C/N ratio indicates a primary role of algae in the production of organic matter. During the Eemian optimum (pollen zones E4–E5), mostly Cladocera species preferring warm water occurred. Algae remained a significant component of OM. The early Eemian post-optimum (pollen zone E6) was characterized as a period of maximal abundance of zooplankton (20 species). During this period, rapid decreases in TOC, TN and the C/N ratio and an increase in δ13C values suggest the reduced abundance of higher plants in the lake. In pollen zone E7, the frequency and diversity of Cladocera rapidly decreased. Species that tolerate cold water were dominant, which reflects unfavorable conditions for the development of zooplankton but a high water level. The low content of organic carbon and nitrogen, a C/N ratio in the range of 13–17 and δ13C values in the range of −26.2 to −28 ‰ suggest the inhibition of terrestrial plant delivery. During the Early Vistulian (pollen zone EV1), rare faunal remains and the features of OM (the lowest amounts of TOC and TN, and the highest value of C/N) reflect the decline of lake conditions and a lack of primary production and aquatic vegetation in the lake.

Evolution of palaeolake environment in Poland during the Eemian Interglacial based on oxygen and carbon isotope data from lacustrine carbonates

The results of oxygen and carbon stable isotope investigations of eight Eemian lacustrine sediments from Poland are presented. The values of δ 18O changed from ca. −11 to −1‰, and δ 13C values oscillated between −3.5 and +7.0‰. The isotopic record correlated well with pollen, cladoceran, and diatom data. The evolution of the palaeolakes in Poland was reconstructed. The palaeolakes originated during the final phase of the Wartanian (Late Saalian) Glaciation. The δ 18O and δ 13C values of that time reflect the input of detrital carbonates into the basins. The boundary between the glaciation and the interglacial period is expressed by a significant decrease in δ 18O and δ 13C values. During the early Eemian, a positive trend in δ 18O values confirms the gradual climatic changes. The Eemian optimum is characterized by constant δ 18O and δ 13C values. During the Early Vistulian (Weichselian) Glaciation, the palaeolake declined. The varying δ 18O values likely reflect frequent changes in water balance between precipitation and evaporation associated with an influence of marine circulation. The fluctuations of the isotopic curves in the upper parts of the successions (the post-optimum) were caused by a shallowing of the basin by infilling with sediments. The observed shifts in the isotopic curves are due to the proximity of the Baltic Sea and earlier strong oceanic influences.

Isotope and Cladocera data and interpretation from the Eemian optimum and postoptimum deposits, Kaliska palaeolake (Central Poland)

During the Eemian optimum, calcareous gyttja and lake marl accumulated. The characteristic feature of calcareous gyttja is an occurrence of fragments of diatoms and plants, while in lake marl they are absent. In the carbonate-rich deposits no Cladocera remains are preserved. Based on the results of stable isotope analyses of carbonates, the eight isotopic horizons (Is) were defined and characterised. In the studied deposits, 15 species of subfossil Cladocera were identified and 6 zones of fauna development were distinguished. The defined Cladocera species are similar to ones known from the other Eemian site in Poland. The faunal taxa indicate the low trophy status of the lake initially, followed by an increase to eutrophic status. The Cladocera and isotopic compositions suggest that the hornbeam zone (E5) was a period of higher density of macrophytes as well as of an increase of biological activity associated with the low water level. The fluctuations of the isotopic curves caused by a shallowing of the basin and a change of sediment lithology are characteristic for the spruce zone (E6). The palaeolake transformed into a peatbog during the pine zone (E7). During the Early Vistulian renewed carbonate accumulation and Cladocera development took place indicating the repeated reservoir existence.

Phytomass and carbon storage during the Eemian optimum, late Weichselian maximum and Holocene optimum in Eastern Europe

The phytomass stored in terrestrial vegetation at 5.5, 18 and 125 Ka BP, representing the environmental extremes of the Late Quaternary, was estimated for the Russian Plain, excluding the northern coast and adjacent piedmont. The estimates are based on paleovegetation maps by Grichuk [Grichuk, V.P., 1982. Rastitel `nost' Evropy v pozdnem pleistotsene. In: Gerasimov, I.P., Velichko, A.A. (Eds.), Paleogeografiya Evropy za Posledniye sto Tysyach Let. Nauka, Moscow, pp. 92–109, (in Russian).] for Eemian optimum, by Velichko and Isayeva [World Atlas of Resources and Environment, 1996. Lionty, H.A. (Ed.). Institute of Geography of RAS, Moscow, Vienna.] for the Late Glacial Maximum, and by Khotinskiy [Khotinskiy, N.A., 1984. Holocene vegetational history. In: Velichko, A.A. (Ed.), Late Quaternary Environments of the Soviet Union. Univ. of Minnesota Press, Minneapolis, pp. 179–200.] for the Late Atlantic, together with analysis of the ecological–coenotic connections of plants and their modern areas. Vegetation on the East-European Plain at 125, 18 and 5.5 Ka BP contained 81.0, 3.1 and 61.4 million kilotons of phytomass, which represents 36.5, 1.4 and 27.6 Gt of carbon. The phytomass of terrestrial plants thus represents an important sink of carbon. Its marked changes make it an important part of the carbon balance during the Pleistocene and the Holocene.