Marker tephra in Haukadalsvatn lake sediment: A key to the Holocene tephra stratigraphy of northwest Iceland

Abstract

Emerging lake sediment records are rapidly improving Iceland‘s Holocene tephra stratigraphy and chronology. Here, we expand upon these recent developments with a securely-dated tephrochronological record from the lake Haukadalsvatn in West Iceland. We capitalize on the existing paleomagnetic secular variation (PSV) age model, which uses 54 ties points to synchronize Haukadalsvatn‘s high-resolution lake sediment record to a well-dated PSV master chronology from North Iceland Shelf marine core MD99-2269. Major element composition permits the identification of 38 tephra layers over the last 10500 years. Of these tephra, 15 can be traced to tephra found on the Vestfirðir peninsula and represent a series of well-dated marker tephra for West and Northwest Iceland that feature precise geochemical fingerprints. Based on these premises, and in contrast to recent assertations, there is no firm evidence for the presence of the presumed Middle Holocene „Hekla Ö tephra” in West or Northwest Iceland. Despite their close geographical locations, comparison of Haukadalsvatn‘s tephra layer frequency record to that of Northwest Iceland‘s reveals different trends. This regional disparity is likely the result of predominately small eruptions that featured narrower ash plumes. We argue that Haukadalsvatn serves as an important template for the tephrochronology of West Iceland and for future studies investigating the tephra records in more distal regions of the northwest North Atlantic, such as Greenland.