Age determination, carbon geochemistry and palynology of section AC003

Sedimentary records from California's Northern Channel Islands and the adjacent Santa Barbara Basin (SBB) indicate intense regional biomass burning (wildfire) at the Ållerød-Younger Dryas boundary (~13.0-12.9 ka) (All age ranges in this paper are expressed in thousands of calendar years before present [ka]. Radiocarbon ages will be identified and clearly marked "14C years".). Multiproxy records in SBB Ocean Drilling Project (ODP) Site 893 indicate that these wildfires coincided with the onset of regional cooling and an abrupt vegetational shift from closed montane forest to more open habitats. Abrupt ecosystem disruption is evident on the Northern Channel Islands at the Ållerød-Younger Dryas boundary with the onset of biomass burning and resulting mass sediment wasting of the landscape. These wildfires coincide with the extinction of Mammuthus exilis [pygmy mammoth]. The earliest evidence for human presence on these islands at 13.1-12.9 ka (~11,000-10,900 14C years) is followed by an apparent 600-800 year gap in the archaeological record, which is followed by indications of a larger-scale colonization after 12.2 ka. Although a number of processes could have contributed to a post 18 ka decline in M. exilis populations (e.g., reduction of habitat due to sea-level rise and human exploitation of limited insular populations), we argue that the ultimate demise of M. exilis was more likely a result of continental scale ecosystem disruption that registered across North America at the onset of the Younger Dryas cooling episode, contemporaneous with the extinction of other megafaunal taxa. Evidence for ecosystem disruption at 13-12.9 ka on these offshore islands is consistent with the Younger Dryas boundary cosmic impact hypothesis [Firestone et al., 2007, doi:10.1073/pnas.0706977104].

Benthic Foraminifera in Upper Pleistocene - Holocene bottom sediments from the southeastern Sea of Okhotsk

A comparative analysis of benthic foraminiferal assemblages in the last glacial sediments obtained by gravity cores from the southern Kamchatka slope (Vulk-34-98) and from the eastern slope of the Akademii Nauk Rise in the central Sea of Okhotsk (Vulk-34-90) revealed, along with their undoubted similarity, substantial differences caused by hydrological regime in these areas during the considered period. It is shown that during the last glacial period bottom waters near the northern Kuril Islands were warmer and less aerated than those in the Akademii Nauk Rise area. As is evident from low-amplitude variations in proportions of dominant species, hydrological parameters in the bottom layer of the latter area at that time were relatively more stable than in the former area.