A multiproxy record of Holocene environmental changes from the northern Kuril Islands (Russian Far East)

Abstract

Diatom, rock magnetic, geochemical, and lithological studies of a sediment core from Paramushir Island (northern Kuril Archipelago) trace environmental shifts from bog to salt-water lagoon to freshwater lake over the past 10,000 14C BP. Organic-rich mesic landscapes dominated the southern island until ~8200 14C BP. Transgression of the Sea of Okhotsk onto the island began sometime after 8200 14C BP, resulting in the formation first of a salty (~8200–5700 14C BP) then a brackish (~5700–5200 14C BP) lagoon. With lowering of sea level after 5200 14C BP, a freshwater lake formed, which has remained to the present day. This history parallels regional trends in the Russian Far East, where maximum sea levels occurred between ~8000 and 4600 14C BP, peaking at ~6400 14C BP. Sandy levels within the lake core suggest four intervals of aeolian activity (~4900–4800 14C BP; 4300–3800 14C BP; 3200–3000 14C BP; 1900–900 14C BP), perhaps related to drier than present climates. Palynological data indicate a dominance of Pinus pumila–Duschekia kamtschatica shrub tundra in the lowlands ~8200–5800 14C BP, marking the Holocene thermal maximum. This vegetation contrasts to modern, which established ~5800 14C BP and is a mix of coastal meadow, Betula–Salix low shrub tundra, and scattered Pinus and Duschekia thickets. The palynological record shows little response to mid-to-late Holocene climatic fluctuations except for a decrease in Pinus shrubs perhaps caused by changes in snow cover and/or summer temperature during the Little Ice Age.