Quantitative dynamics of the early Pliocene climate and vegetation in the Lena River Delta (northern Yakutia, Eastern Siberia)

Abstract

Early Pliocene climate and vegetation evolution in the Lena River Delta (northern Yakutia, Eastern Siberia) are quantitatively studied for the first time in de­ tail, based on a palaeobotanical record. Palaeobotanical data for this time-interval were obtained on 28 palynofloras from the Sardakhskaya Formation in the coastal cliffs of the Sardakh-Sisse Island (Lena River Delta). In this first integrative study we apply the Coexistence Approach (CA) for quantification of palaeoclimate, the Plant Functional Types (PFT) approach and Integrated Plant Record (IPR) vegetation analysis for quantification of palaeovegetation. Our investigation documents the persistence of temperate climate with two warmer and colder phases. Moreover, our reconstructions show significantly higher mean values of all temperature parameters in comparison to previous estimations. Overall hu­ mid climate conditions (up to 1500 mm) prevailed throughout the early Pliocene correspond to an oceanic climate. Our reconstruction indicates relatively strong temperature and precipitation seasonality. Our data for vegetation show more open vegetation in comparison to previous studies reconstructing mixed conifer- deciduous forests for the early Pliocene of Northeast of Russia. Based on PFT, the early Pliocene vegetation of northern Yakutia in Lena River Delta mainly was presented by more or less open mixed deciduous woodlands of warmer or colder temperate type. The results obtained from the PFT approach generally are in ac­ cordance with our data obtained from IPR approach. However, based on IPR, periodically forests and grasslands were obtained in addition to open woodlands.