Additional Authors: Larocque, Isabelle (8); Lavoie, Martin (9); Lamothe, Michel (10); Vincent, Warwick F. (11); Niederreiter, Richard (12)

⁸ Centre Eau, Terre et Environnement, Institut national de la recherche scientifique (INRS), Québec, Québec, G1K 9A9, Canada.
⁹ Département de Géographie, Centre d'études nordiques, Université Laval, Québec, G1V 0A6 Canada.
¹⁰ Département des sciences de la Terre et de l'atmosphère, Université du Québec à Montréal (UQAM, Montréal, Canada.
¹¹ Département de Biologie, Centre d'études nordiques, Université Laval, Québec, G1V 0A6 Canada.
¹² UWITEC, Moosbachweg 10, Mondsee, Austria

Most lakes in the northern circumpolar region are of glacial origin and allow hindcasts that date back only until the last deglaciation several thousand years ago, because of glacial erosion of their sediment infill. With the exception of the El'gygytgyn Crater Lake in Siberia, all other climate archives of the Arctic covering several interglacials originate from marine sediments or ice cores. The sediments of the Pingualuit Crater Lake (Nunavik, Canada; 61°17'N, 73°41'W) - known as the "Crystal Eye of Nunavik"- offer the unique opportunity to study terrestrial climate dynamics not only during the postglacial period, but potentially over several hundreds of thousands of years as its deep sediment infill promises to yield an uninterrupted arctic paleoclimate record covering several interglacial-glacial cycles. Previous attempts to core the lake have resulted in the collection of only 14 cm of sediments that spanned the last ~5000 years. Almost 20 years later (May 2007), an expedition team of 5 scientists, 1 park representative and 2 Inuit assistants managed to extract about 10 m of sediments from a lake water depth of 270 m using a UWITEC piston percussion corer system under harsh climatic conditions and severe water protection measures. Here we will present initial results of limnological measurements (PAR, UV light transparency) performed on the water column of one of the deepest and most transparent lakes on this planet. We will also report on the high resolution physical (CAT-scan, Multi Sensor Core Logger, color reflectance, high resolution digital images), magnetic (point source magnetic susceptibility) and sedimentological (density, grain size) analyses of the lake sediment archives. The initial results revealed the presence of at least two decimetre-thick intervals composed of laminated, dark grey clayey silts characterized by a relatively low density and magnetic susceptibility that contrast sharply with the thicker over- and underlying sections with light grey, denser, sandy sediments. The sediment characteristics in the darker laminated intervals are also similar to the ones observed in the small surface gravity core sampled at the site. Moreover, smear slides from these two intervals revealed the presence of fossil diatoms and chrysophytes, suggesting that these two intervals represent ice-free conditions and thus possible interglacials, whereas the more extensive light grey and sandy sediments likely reflect glacial intervals. This interpretation will be tested by ongoing paleomagnetic and spectroscopic measurements (i.e., magnetostratigraphy, fourier transform infrared spectroscopy- FTIRS), multi-proxy biostratigraphic analyses (diatoms, chironomids, cladocerans, pollens), as well as radiocarbon and thermoluminescence dating.