HR: 08:15h
AN: PP11A-02    [Abstracts]
TI: Sedimentary Record of the Last two Interglacials in the Terrestrial Canadian Arctic (Pingualuit Crater Lake, Nunavik)
AU: * St-Onge, G
EM: guillaume_st-onge@uqar.qc.ca
AF: GEOTOP Research Center, C.P. 8888, Succ. Centre-ville,
AU: * St-Onge, G
EM: guillaume_st-onge@uqar.qc.ca
AF: Institut des sciences de la mer de Rimouski (ISMER), Universite du Quebec a Rimouski, ,
AU: Guyard, H
EM: herve.guyard@uqar.qc.ca
AF: GEOTOP Research Center, C.P. 8888, Succ. Centre-ville,
AU: Guyard, H
EM: herve.guyard@uqar.qc.ca
AF: Institut des sciences de la mer de Rimouski (ISMER), Universite du Quebec a Rimouski, ,
AU: Pienitz, R
EM: reinhard.pienitz@cen.ulaval.ca
AF: CEN and Departement de Geographie, Universite Laval,
AU: Hausmann, S
EM: shausman@uark.edu
AF: Department of Geosciences, Uiversity of Arkansas,
AU: Francus, P
EM: pierre_francus@ete.inrs.ca
AF: Centre - Eau Terre Environnement, Institut national de la recherche scientifique (INRS),
AU: Salonen, V
EM: veli-pekka.salonen@helsinki.fi
AF: Department of Geology, University of Helsinki,
AU: Luoto, T
EM: tomi.luoto@helsinki.fi
AF: Department of Geology, University of Helsinki,
AU: Black, J
EM: jlb009@uark.edu
AF: Department of Geosciences, Uiversity of Arkansas,
AU: Lamothe, M
EM: lamothe.michel@uqam.ca
AF: Departement des sciences de la Terre et de l'atmosphere, Universite du Quebec a Montreal,
AU: Zolitschka, B
EM: zoli@uni-bremen.de
AF: GEOPOLAR, Institute of Geography University of Bremen,
AU: Larocque, I
EM: isabelle_larocque@ete.inrs.ca
AF: Centre - Eau Terre Environnement, Institut national de la recherche scientifique (INRS),
AB: The Pingualuit crater lake (Nunavik, Canada) resulted from a meteoritic impact that occurred ca. 1.4 million years ago. Due to its unique morphometry (depth and shape), the lake bottom may have escaped glacial erosion. Based on a punctual seismic profile acquired using a 12 kHz Knudsen echosounder and using both gravity and piston corers, we recovered the uppermost 8.5 m of sediments. High-resolution physical (CAT- Scan, Multi Sensor Core Logger, diffuse spectral reflectance), geochemical (ITRAX core scanner, carbon and nitrogen contents, δ¹³C of the organic matter) and magnetic (magnetic susceptibility, natural, anhysteretic, isothermal and saturation isothermal remanent magnetizations) analyses were performed. Two main lithofacies were clearly identified by the different measurements and likely represent successive interglacial/glacial cycles. Most of the sediment consists of light grey silts containing several angular rock fragments, that is characterized by very low organic carbon content, relatively high density and magnetic susceptibility values, suggesting a deposition during glacial conditions. Interbedded between this facies are at least two decimetre-thick, organic-rich and finely laminated intervals likely representing ice free periods. The presence of diatoms, chrysophytes and chironomid head capsules in smear and microscope slides from these two intervals supports this hypothesis. In addition, preliminary Infrared Stimulated Luminescence (IRSL) measurements indicate that the upper organic-rich layer has an age coeval with the last interglacial (Oxygen Isotope Stage 5), while the age of the lower organic-rich layer is consistent with an older interglacial, likely the Oxygen Isotope Stage 7. The sedimentary infill thus constitutes a unique long-term terrestrial record of environmental and climatic conditions in the Canadian Arctic. Furthermore, because these sediments escaped glacial erosion, it suggests the presence of a subglacial lake during the last two glacial periods. Micro- sedimentological analyses of thin sections are currently underway to define the depositional environments of each laminated interval.
DE: 4914 Continental climate records
DE: 4926 Glacial
DE: 4936 Interglacial
DE: 9315 Arctic region (0718, 4207)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2009 Joint Assembly