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.

Surface water productivity and sediment transport by Bering Strait throughflow in the Chukchi Shelf (the western Arctic Ocean) during the Holocene

“…This timing is also consistent with sea-level records from Beringia (Elias et al, 1996;Mason and Jordan, 2002). The coincidence between our age expectation and the well-dated cores by previous studies (Bauch et al, 2001;Kim et al, 2017;Lisé-Pronovost et al, 2009) guarantees a plausible and acceptable age estimate for the lithologic boundary between Unit 2a and Unit 2b, which is indicative of depositional environment changes, although this age postdates a little the timing when the sea level reached the present condition (Figure 2c).…”

“…A little older age is a result that this shell fragment is reworked. In addition, Kim et al (2017) divided three palynological zones from a core (ARA02B-01A) collected in the northern margin of Chukchi Shelf and, conclusively, their lower lithologic boundary (~8400 cal. yr BP) is matched thoroughly with the age estimate between Unit 1 and Unit 2a.…”

“…The upper palynological zone of a core (ARA02B-01A) in the northern margin of Chukchi Shelf was dated at about 4000 cal. yr BP (Kim et al, 2017). Lisé-Pronovost et al (2009) reported a major decrease (from ~3.5 m/kyr to ~1.2 m/kyr) in the sedimentation rate on the Arctic Alaskan margin at approximately 5000 cal.…”

Glycerol dialkyl glycerol tetraether variations in the northern Chukchi Sea, Arctic Ocean, during the Holocene

“…Various stratigraphic and sedimentological data on one or several of the cores under study have been reported in a number of papers (Barletta et al, 2008;McKay et al, 2008;Darby et al, , 2012Polyak et al, 2009Polyak et al, , 2016Lisé-Pronovost et al, 2009;Faux et al, 2011;Kim et al, 2016). Sediments in cores 08JPC and 01A-GC consist predominantly of homogenous clayey silts indicative of open-marine environments, with a more sandy composition near the core bottom, possibly related to shallow-water erosion and redeposition during the shelf flooding .…”

Late Holocene Sedimentation in Active Geological Structures of the Chukchi Sea

“…Для палинологического анализа использовались образцы объемом 1 см 3 . По методике [Rudaya, 2010;Kim et al, 2017] были добавлены две таблетки с калиброванным маркером (споры Lycopodium), необходимым для подсчета концентрации зерен. Пробы заливались 10%-ной HCl для удаления карбонатов, затем органическая часть осадка, содержащая пыльцу и споры, отделялась кипячением в 10%-ном растворе KOH с последующей сепарацией в тяжелой жидкости KJ+KdJ (удельный вес -2.2 г/см 3 ).…”