Paleo-Ecology of the Yedoma Ice Complex on Sobo-Sise Island (EasternLena Delta, Siberian Arctic)

Abstract

Late Pleistocene permafrost of the Yedoma type constitutes a valuable paleo-environmental archive due to the presence of numerous and well-preserved floral and faunal fossils. The study of the fossil Yedoma inventory allows for qualitative and quantitative reconstructions of past ecosystem and climate conditions and variations over time. Here, we present the results of combined paleo-proxy studies including pollen, chironomid, diatom and mammal fossil analyses from a prominent Yedoma cliff on Sobo-Sise Island in the eastern Lena Delta, NE Siberia to complement previous and ongoing paleo-ecological research in western Beringia. The Yedoma Ice Complex (IC) cliff on Sobo-Sise Island (up to 28 m high, 1.7 km long) was continuously sampled at 0.5 m resolution. The entire sequence covers the last about 52 cal kyr BP, but is not continuous as it shows substantial hiatuses at 36–29 cal kyr BP, at 20–17 cal kyr BP and at 15–7 cal kyr BP. The Marine Isotope Stage (MIS) 3 Yedoma IC (52–28 cal kyr BP) pollen spectra show typical features of tundra–steppe vegetation. Green algae remains indicate freshwater conditions. The chironomid assemblages vary considerably in abundance and diversity. Chironomid-based TJuly reconstructions during MIS 3 reveal warmer-than-today TJuly at about 51 cal kyr BP, 46-44 and 41 cal kyr BP. The MIS 2 Yedoma IC (28–15 cal kyr BP) pollen spectra represent tundra-steppe vegetation as during MIS 3, but higher abundance of Artemisia and lower abundances of algae remains indicate drier summer conditions. The chironomid records are poor. The MIS 1 (7–0 cal kyr BP) pollen spectra indicate shrub-tundra vegetation. The chironomid fauna is sparse and not diverse. The chironomid-based TJuly reconstruction supports similar-as-today temperatures at 6.4–4.4 cal kyr BP. Diatoms were recorded only after about 6.4 cal kyr BP. The Sobo-Sise Yedoma record preserves traces of the West Beringian tundra-steppe that maintained the Mammoth fauna including rare evidence for woolly rhinoceros’ presence. Chironomid-based TJuly reconstructions complement previous plant-macrofossil based TJuly of regional MIS 3 records. Our study from the eastern Lena Delta fits into and extends previous paleo-ecological Yedoma studies to characterize Beringian paleo-environments in the Laptev Sea coastal region.

Organic matter characteristics of a rapidly eroding permafrost cliff in NE Siberia (Lena Delta, Laptev Sea region)

“…The relatively high ACL across the cliff (Fig. 3) indicates a predominant contribution of vascular plants, which corroborates the pollen record presented by Wetterich et al (2021). Their results indicated the presence of tundra-steppe vegetation during MIS 3-2, while MIS 1 pollen spectra of the uppermost three samples indicated a shift from tundra-steppe to shrub-tundra vegetation.…”

“…Cooler and drier summer conditions as well as unstable (draining and rewetting phases) aquatic conditions were reconstructed for MIS 2 (Wetterich et al, 2021). In our study, the elevated ratio of iso-and anteiso-branched FAs relative to mid-and long-chain (C ≥ 21) n-FAs in unit I (MIS 1) and III (MIS 3) compared to unit II (MIS 2; Figs.…”

“…At the Sobo-Sise Yedoma cliff, the CPI values scattered around a mean of 9.89 and decreased in the lowermost 7 m of the cliff profile. This could probably indicate a higher level of OM decomposition for the lower cliff part but can also be influenced by the vegetation type and species prevailing during the early MIS 3 with stagnant water and partly warmer-than-today summer climate conditions (Wetterich et al, 2021). The HPFA values (0.45-0.86, median 0.61) are a bit higher compared to Yedoma deposits investigated by Strauss et al (2015) on the Buor Khaya Peninsula (0.15-0.69, median 0.54).…”

Towards a science of archaeoecology

“…Its upper temporal limit typically corresponds to the Pleistocene megafauna extinctions, although some suggest its scope also encompasses the Holocene [11,15]. Palaeoecologists look for the incidentally preserved remains of past biota, including shale deposits [23], permafrost preserved ecosystems [24], bog contexts [25], and other fossilized or preserved remains. These traces of the past have been instrumental in helping to understand the climatic, evolutionary, and ecological trajectory of our planet.…”

Fluvial and permafrost history of the lower Lena River, north‐eastern Siberia, over late Quaternary time

“…Estimates give the suspended sediment load in the lower Lena River at 21 Mt year −1 with <30% of this load thought to reach the sea (Are & Reimnitz, 2000). Fedorova et al (2015, and references therein) cite measurements saying that the amount of bottom sediments is about 5.4 Mt year −1 and Fofonova et al (2018, references therein) cite measurements saying that the annual bedload flux has been measured to be 14.9 Mt year −1 at Kyusur gauging station, which lies 200 km south of the Lena River delta, Exploration of deltaic sediment records allow to investigate the conditions of sediment deposition with biogeochemical and palaeoenvironmental archives (Schwamborn et al, 2002;Schirrmeister et al, 2003Schirrmeister et al, , 2011Wetterich et al, 2008Wetterich et al, , 2021. However, much of the observation has been restricted to exposures and to shallow coring down to 10 m depth with floodplain deposits being the dominant sediment type (Bolshiyanov et al, 2015).…”