Tephrochronology,magnetostratigraphy and mammalian faunas of Middle and Early Pleistocene sediments at two sites on the Old Crow River,northern Yukon Territory,Canada |
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| Authors: | John A Westgate G William Pearce Shari J Preece Charles E Schweger Richard E Morlan Nicholas JG Pearce T William Perkins |
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| Institution: | 1. Department of Geology, University of Toronto, Toronto, ON, Canada M5S 3B1;2. 152 Indian Road, Kingston, ON, Canada K7M 1T4;3. Department of Anthropology, University of Alberta, Edmonton, AB, Canada T6G 2H4;4. Archaeological Survey of Canada, Canadian Museum of Civilization, Hull, Quebec, Canada J8X 4H2;5. Institute of Geography and Earth Science, Aberystwyth University, Wales, SY23 3DB, UK |
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| Abstract: | Alluvial and lacustrine sediments exposed beneath late Pleistocene glaciolacustrine silt and clay at two sites along the Old Crow River, northern Yukon Territory, are rich in fossils and contain tephra beds. Surprise Creek tephra (SZt) occurs in the lower part of the alluvial sequence at CRH47 and Little Timber tephra (LTt) is present near the base of the exposure at CRH94. Surprise Creek tephra has a glass fission-track age of 0.17 ± 0.07 Ma and Little Timber tephra is 1.37 ± 0.12 Ma. All sediments at CRH47 have a normal remanent magnetic polarity and those near LTt at CRH94 have a reversed polarity — in agreement with the geomagnetic time scale. Small mammal remains from sediments near LTt support an Early Pleistocene age but the chronology is not so clear at CRH47 because of the large error associated with the SZt age determination. Tephrochronological and paleomagnetic considerations point to an MIS 7 age for the interglacial beds just below SZt at CRH47 and at Chester Bluffs in east-central Alaska, but mammalian fossils recovered from sediments close to SZt suggest a late Irvingtonian age, therefore older than MIS 7. Further studies are needed to resolve this problem. |
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