Assessing the late Holocene14C reservoir age of theChukchi Sea with the AniakchakCFE II tephra 3.6 kyr BP

• Main Author: Geels, Alexis
• Format: Bachelor Thesis
• Language: English
• Published: Stockholms universitet, Institutionen för naturgeografi 2019
• Subjects: Cryptotephra; Aniakchak CFE II; Arctic Ocean; Chukchi Sea; Marine Reservoir Effect; Physical Geography; Naturgeografi; Arctic; Greenland; Pacific; Chukchi; Newfoundland; Alaska
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-193090

Tephrochronology is a powerful tool to correlate and improve the chronology of sedimentaryarchives in the Arctic Ocean. The Aniakchak Caldera Forming Eruption (CFE) in Alaska at3.6 cal kyr BP ejected ash that were found in a widespread layer in Alaska, and as cryptotephrain the Chukchi Sea, Newfoundland, and Greenland. This study presents data from the coreSWERUS-L2-4-PC1 (4PC) taken at a water depth of 120 m in the Chukchi Sea. The sharp peakin tephra shards concentration permitted to clearly place the isochron. Unfortunately, the microprobeanalyses were unsuccessful, however measurements of trace elements were performedwith Laser Ablated-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS). The geochemicalsignature of the Aniakchak 3.6 eruption was ensured with significant trace elementratios. The isochron of the eruption combined with the radiocarbon dates from 4PC permittedto calculate the local marine radiocarbon reservoir age offset DR=36446 years. This value isrelatively low compared to recent estimates in the Chukchi Sea, especially to the neighbouringcore SWERUS-L2-2-PC1 were DR=47760. The DR value of this study is explained by theinfluence of the "young" Atlantic water mixing with the "old" Pacific water at the depth wherethe core was taken.