HR: 1340h
AN: U13B-1150    [Abstracts]
TI: Preliminary Chronostratigraphy of Pingualuit Impact Crater Lake Sediments (Nunavik, Canada): a Possible Arctic Terrestrial Record of Several Glacial/Interglacial Cycles
AU: * St-Onge, G
EM: guillaume_st-onge@uqar.qc.ca
AF: ISMER and GEOTOP, Universite du Quebec a Rimouski 310 allee des Ursulines, Rimouski, QC G5L 3A1, Canada
AU: Guyard, H
EM: herve.guyard@uqar.qc.ca
AF: ISMER and GEOTOP, Universite du Quebec a Rimouski 310 allee des Ursulines, Rimouski, QC G5L 3A1, Canada
AU: Pienitz, R
EM: reinhard.pienitz@cen.ulaval.ca
AF: Dept. of Geography and CEN, Universite Laval, Quebec, QC G1K 7P4,
AU: Hausmann, S
EM: shausman@uark.edu
AF: Dept. of Geosciences, University of Arkansas, Fayetteville, AR 72701, United States
AU: Salonen, V
EM: vpsalone@mappi.helsinki.fi
AF: Dept. of Geology, University of Helsinki, Helsinki, FI-00014, Finland
AU: Luoto, T
EM: Tomi.Luoto@helsinki.fi
AF: Dept. of Geology, University of Helsinki, Helsinki, FI-00014, Finland
AU: Francus, P
EM: pfrancus@ete.inrs.ca
AF: INRS-ETE and GEOTOP, 490 rue de la Couronne, Quebec, QC G1K 9A9, Canada
AU: Larocque, I
EM: isabelle_larocque@ete.inrs.ca
AF: INRS-ETE and GEOTOP, 490 rue de la Couronne, Quebec, QC G1K 9A9, Canada
AU: Lavoie, M
EM: martin.lavoie@cen.ulaval.ca
AF: Dept. of Geography and CEN, Universite Laval, Quebec, QC G1K 7P4,
AU: Lamothe, M
EM: lamothe.michel@uqam.ca
AF: Dept. of Earth and Atmospheric Sciences, Universite du Quebec a Montreal, Montreal, QC H3C 3P8, Canada
AU: Vincent, W F
EM: warwick.vincent@bio.ulaval.ca
AF: Dept. of Biology and CEN, Universite Laval, Quebec, QC G1K 7P4, Canada
AU: Niederreiter, R
EM: richard.niederreiter@uwitec.at
AF: UWITEC, Moosbachweg 10, Mondsee, A-5310, Austria
AB: The Pingualuit Crater Lake is a 1.4 Ma perfectly circular depression. It is 3.4 km in diameter and hosts a lake with a maximum depth of 267 m with no surface connection to other surrounding water bodies. It is located in the northernmost part of the Ungava Peninsula in Nunavik, Canada (61°N, 73°W) and, due to its unique morphometry (shape, depth), the lake bottom may have escaped glacial erosion, possibly preserving a continuous Arctic terrestrial record of several glacial/interglacial cycles. Previous attempts to core the lake have resulted in the collection of only 14 cm of sediments that spanned about the last ~5000 years. Here, in order to test the possible accumulation of several glacial/interglacial cycles, we will present initial high resolution physical (CAT-scan, Multi Sensor Core Logger, color reflectance, high resolution digital images), magnetic (point source magnetic susceptibility) and sedimentological (detailed visual description, grain size) properties of about 10 m of sediments recently cored using a UWITEC piston percussion corer under harsh climatic conditions. 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 and more abundant over- and underlying 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 same site. Moreover, smear slides performed in these two intervals revealed the presence of diatoms and chrysophytes, suggesting that these two intervals represent ice-free conditions and thus possible interglacials, whereas the more abundant light grey and more sandy sediments likely reflect glacial intervals. This interpretation will be tested by ongoing paleomagnetic measurements (i.e., magnetostratigraphy), as well as radiocarbon and thermoluminescence dating.
DE: 1105 Quaternary geochronology
DE: 1135 Correlative geochronology
DE: 1165 Sedimentary geochronology
DE: 1520 Magnetostratigraphy
DE: 4914 Continental climate records
SC: Union [U]
MN: 2007 Fall Meeting