Terrestrial and aquatic palynomorphs in Holocene sediments from the Chukchi–Alaskan margin, western Arctic Ocean: Implications for the history of marine circulation and climatic environments

Abstract

Two sediment cores from the Chukchi Sea margin north of Alaska were analyzed for palynological composition including terrestrial and aquatic palynomorphs. Based on 13 radiocarbon ages, the investigated sedimentary record represents most of the Holocene with a century to multidecadal age resolution. Three palynological zones were discriminated based on the abundance of major palynomorph groups (terrestrial and freshwater palynomorphs and dinoflagellate cysts) and composition of spore and pollen assemblages. They are interpreted in terms of depositional and paleoclimatic changes including predominance of redeposition by meltwater or sea ice in the early-Holocene, a strong input of contemporaneous material related to Pacific water advection culminating after ca. 6000 yr BP, and more subtle changes in the late-Holocene. It is concluded that depositional environments, such as current transportation and mixing, have an overall major control on palynomorph distribution. The climatic factors may have also played an important role in palynomorph abundance and composition, especially in the middle- to late-Holocene, when circulation changes were less dramatic than during the flooding of the Bering Strait and the shallow Chukchi Sea shelf. Comprehending these linkages requires a better knowledge of the Holocene vegetation history in the coastal areas of Alaska and Chukchi Peninsula.