The Bolling-Allerod Transition in the Eastern Baltic: Environmental Responses to Climate Change

Simple Summary During the last glaciation, the nature of the northern hemisphere of the Earth underwent significant changes. Nonetheless, it underwent no less serious changes after the melting of the glacier, when, under the conditions of climate mitigation, the gradual formation of modern landscapes began in the spaces freed from ice. This study is devoted to the reconstruction of the post-glacial environment in one of the regions of Eastern Europe, in the south-eastern part of the Baltics. The uniquely preserved deposits of one of the post-glacial basins discovered here made it possible to reconstruct in detail the changes in climate, vegetation, and aquatic organisms in the time interval of 14-13.4 thousand years ago. The study revealed that during this period there were short-lasting climate fluctuations (warmings and coolings), which caused repeated changes in all components of the local nature. The results of the study contribute to understanding the complex processes of planetary climate formation, as well as the impact of climate on nature both at local and global levels, which is necessary not only for understanding the past, but also for predicting the future of all living organisms on the planet. This paper presents the results of a study on the Kulikovo section (south-eastern Baltic Sea coast), a sediment sequence exposing deposits of a post-glacial basin that existed along the edge of the glacier in the Late Pleistocene. The research was targeted at the reconstruction of the dynamics of the local environmental systems in response to climatic oscillations of the Lateglacial (the Older Dryas-first half of the Allerod). The evolution of the local biotic components on the territories of the Baltic region after the ice retreat is still poorly understood. Data from geochronological, lithological, diatom, algo-zoological and palynological analyses provide a reconstruction of local aquatic and terrestrial biocenoses and their response to short-term warmings and coolings that took place 14,000-13,400 cal yr BP. This study has demonstrated that, during the Older Dryas and first part of the Allerod (GI-1d and GI-1c), the aquatic and terrestrial environment of the Kulikovo basin underwent several changes, resulting in eight stages of the basin evolution, most probably related to the short-term climatic fluctuations that could have had a duration of several decades. The data obtained in this study have revealed the fairly dynamic and complex evolution of the pioneer landscapes, as indicated by the changes in the hydrological regime of the area and by the traced successions of plant communities from the pioneer swampy vegetation to park and real forests towards the middle of the Allerod.