期刊
QUATERNARY SCIENCE REVIEWS
卷 30, 期 27-28, 页码 3892-3907出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.quascirev.2011.10.002
关键词
Lacustrine sediments; Stratigraphy; Multiproxy; Late Pleistocene; Ungava; Crater Lake; Subglacial Lake
资金
- Canadian Foundation for Climate and Atmospheric Sciences (CFCAS)
- Natural Sciences and Engineering Research Council of Canada (NSERC)
- International Association of Sedimentologists (IAS)
- X-Strata Mine
- Canadian Foundation for Innovation (CFI)
- Ministere de l'education, du loisir et du sport of Quebec
- Geological Society of America (GSA)
The Pingualuit Crater was formed by a meteoritic impact ca. 1.4 million years ago in northernmost Ungava (Canada). Due to its geographical position near the center of successive North American ice sheets and its favorable morphometry, the Pingualuit Crater Lake (water depth = 246 m) promises to yield a unique continuous sedimentary sequence covering several glacial/interglacial cycles in the terrestrial Canadian Arctic. In this paper, we suggest the existence of a subglacial lake at least during the Last Glacial Maximum (LGM) by hydraulic potential modeling using LGM ice-surface elevation and bed topography derived from a digital elevation model. These results support the hypothesis that the bottom sediments of the Crater Lake escaped glacial erosion and may contain a long-term continental sedimentary sequence. We also present the stratigraphy of a 9 m-long core retrieved from the deep basin of the lake as well as a multiproxy reconstruction of its deglacial and postglacial history. The base of the core is formed by very dense diamicton reflecting basal melt-out environments marking the end of subglacial conditions at the coring site. The overlying finely laminated silt are related to the onset of proglacial conditions characterized by extremely low lacustrine productivity. Infra Red Stimulated Luminescence and AMS C-14 dating, as well as biostratigraphic data indicate sediment mixing between recent (e.g. Holocene) and much older (pre- to mid-Wisconsinan) material reworked by glacier activity. This process prevents the precise dating of these sediments that we interpret as being deposited just before the final deglaciation of the lake. Two finer grained and organic-rich intervals reflect the inception of lacustrine productivity resulting from the cessation of glacial meltwater inputs and ice-free periods. The lower organic interval corresponds to the early postglacial period (6850-5750 cal BP) and marks the transition between proglacial and postglacial conditions during the Holocene Thermal Maximum, while the uppermost organic-rich core section represents late Holocene sediments (similar to 4200-600 cal BP). The organic intervals are separated by a basin-scale erosive slide occurring around 4200 cal BP and likely related to 1) a seismic event due to the glacio-isostatic rebound following the last deglaciation or 2) slope instabilities associated with rapid discharge events of the lake. (C) 2011 Elsevier Ltd. All rights reserved.
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