Peat palaeorecords from the arid Caspian Lowland in Russia: Environmental and anthropogenic effects during the second half of the Holocene

Abstract

The current study presents new palaeoecological records from arid areas in the western sector of the Caspian Lowland, covering the second half of the Holocene . Environmental alterations, driven by global climatic factors and regional features initiated by the Caspian Sea, were identified based on palynological and sedimentological changes in two mires . The study revealed that the wetlands in the south and northwest of the Caspian Lowland have different origins and sources of water supply because they are associated with the priority influence of the Caspian Sea (i.e. Arkida mire) or the dynamics of winter-cyclonic precipitation (i.e. Zelmen mire). Therefore, the humidification episodes in the peatlands under consideration were rarely synchronous. In the south of the Caspian Lowland adjacent to the Caucasus, the climate was milder, steppe vegetation predominated, and the most favourable intervals were at about 4.1–3.8, 3.4–2.8, 2.3–2.9 and after 1.5 cal ka BP. Apparently, the moisturising influence of the Caspian Sea was decisive there, even during the strengthening of the high-pressure zone in Siberia , resulting in a decreased role of westerlies and dryness in other regions. The northeast of the Caspian Lowland was distinguished by longer arid episodes and a more significant contribution of semi-desert vegetation. An increase in moisture and steppe predominance detected there at intervals of 6.7, 3.8, 2.8–2.4, and several shorter ones after 1.4 cal ka BP is associated with warm and humid winters that coincided with a weak Siberian High and North Atlantic warming combined with Caspian transgression. Wetlands in arid areas were vulnerable to intensive human activity over thousands of years and were involved in year-round grazing cycles, even during dry periods. Peculiarities of paleoecological records reflect the burning and forced grazing on the mire under aridification , evident signs of overgrazing, and the use of swamp herbs for building purposes. • Holocene moisture in the arid Caspian lowland was influenced by the Caspian Sea and westerlies. • Influence in the Caspian transgression was decisive even in the strengthening of the Siberian High. • Peat records reflect different episodes of aridification in the south and northwest. • Wetlands in arid areas were used by human activity in the past.