| Large, explosive pyroclastic eruptions can disperse fine tephra shards hundreds to thousands of kilometers from their volcanic vents, serving as instantaneous time markers. Identifying and characterizing these glass shards has been typically limited to visible ash beds proximal to the source. However, advances in isolation methods and instrumentation produce promising results towards the detection of microscopic tephra termed cryptotephra. Here we present two separate studies that advance the detection of cryptotephra in distal, minerogenic and organic-rich lacustrine archives from the Arctic. First, we use the ITRAX core scanner to rapidly and non-destructively analyze synthetic lacustrine sediment cores at sub-millimeter resolution. We find that cryptotephra horizons are detectable in organogenic sediment, but they are imperceptible within minerogenic sediment due to aluminosilicate enrichment within the background matrix. In the second study, we successfully isolate and geochemically characterize a cryptotephra horizon within lacustrine sediment from Spitsbergen, Svalbard. Geochemical analyses combined with multi-proxy age models suggest that this unknown cryptotephra was transported from the explosive Oraefajokull 1362 AD eruption in Iceland. These cryptotephra shards were deposited more than 1000 km from the eruption source. This study represents the first discovery of cryptotephra in Svalbard lacustrine sediment, as well as the northernmost Oraefajokull tephra deposit found in the world. |
