Previous work on lake and peat deposits throughout Europe and Alaska have used the distribution of tephra from Quaternary Icelandic and Alaskan volcanoes as a way to independently date sediments. Such a technique would be extremely useful in High Arctic lake sediments due to the typical lack of dateable organic-material in these environments. However, tephra has not yet been found in High Arctic lakes. Due to the distal location from active volcanic regions, resulting in the fall-out of limited and extremely fine grain volcanic material, additional techniques are necessary to locate and isolate cryptotephra from minerogenic High Arctic lake sediments.
Here we present results detailing the successful extraction of rhyolitic cryptotephra from Lake C3 (northern Ellesmere Island) sediments using a sieve array and heavy liquid separation technique (modified from Turney, 1998 and Blockley et al., 2005). Upcoming work includes electron microprobe analysis on extracted volcanic glass shards in order to determine their geochemical composition. The goal is to use this information to identify the likely source eruption and time of tephra dispersal, thereby providing an independent marker for varve chronology and a tool for site correlation between Lake C3 and other Arctic lakes.

Also presented is a preliminary 1200 year varve thickness record developed from a sediment core recovered from Lake C3 during the summer of 2006. Lake C3 (82°50’N, 78°2’W), located adjacent to Taconite Inlet, northern Ellesmere Island, Nunavut, Canada, is depleted in oxygen at the sediment-water interface and clastic laminations are well preserved in the sedimentary record. Epoxy impregnated thin sections were made for the upper 2.5 m of the cores and, using new imaging software, a varve chronology and thickness record was developed extending back 1200 years. Radionuclide analysis of the upper 6 cm using 210Pb and 137Cs supports the interpretation that the laminations are varves. 239+240Pu activity was also determined using an alternative sampling scheme than previously used for Pb and Cs in order to test the consistency of the radionuclide activity interpretation. Pu activity, determined using sector field ICPMS, confirmed the success of Cs analysis and supported the hypothesis that particular upper laminations were turbidites and should therefore be taken out of the lamination chronology. The onset and peaks of radionuclide detection suggest that approximately 45 varves are unaccounted for in the upper 6 cm chronology; these were likely eroded by two turbidites present in this section. As similar laminations are present throughout the core, a successful cryptotephra chronology will assist in adjusting the varve chronology to account for anomalous laminations and erosion.