CGRG Bibliography of Canadian Geomorphology
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Author : Barendregt, R.W.; and Duk-Rodkin, A.
Date : 2009.
Title : Paleomagnetic evidence for multiple Late Cenozoic glaciations in the Tintina Trench, west central Yukon, Canada.
Publication : 2009 American Geophysical Union Fall Meeting. December 14-18, 2009. San Francisco, California, USA.
Issue :
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Abstract
The Tintina Trench in west central Yukon has preserved an extensive record of preglacial, glacial, and interglacial sediments which were deposited during the late Cenozoic, extending from late Pliocene to late Pleistocene. These deposits comprise multiple sequences of tills, outwash, loesses, and paleosols. The sediments which were laid down directly by ice (tills) are of both local (montane) and regional (Cordilleran) provenance. The Tintina Trench area was impacted repeatedly by local montane ice from the southern Ogilvie Mountains to the northwest (2500 m), and also repeatedly along its southern extent by Cordilleran ice from the Selwyn Mountains to the east (2759 m), the latter forming the continental divide in this region. We report here the magnetostratigraphy of three sections: Rock Creek (RC) (64°13'; 139°07'), West Fifteenmile River (WFR) (64°29'; 139°55'), and East Fifteenmile River (EFR) (64°23'; 139°48'). The majority of the units identified at these sections record late Pliocene to mid-Pleistocene glaciations, although relatively thin surficial sequences of late middle Pleistocene to late Pleistocene loesses and tills are present as well. Of the eleven units described in the Tintina Trench 7 have normal polarity, 3 have reversed polarity, and 1 unit has an undefined polarity. These units span about 2.89 million years (2.90 to 0.01 Ma). It appears that most of the polarity chrons and subchrons of the late Cenozoic are present, and that the sequence of 6 reversals record at least 10 glaciations (3 in the Brunhes and 7 in the Matuyama Chron), and 7 interglaciations (2 in the Brunhes and 5 in the Matuyama Chron). The interglacials are recorded as either paleosols or unconformities between glacial or loess units having opposite polarity. While not all Matuyama Chron glacial and interglacial cycles recorded in marine isotopic records are seen on land, the terrestrial records found in the Tintina Trench have thus far proven to be the most complete in terms of the polarity record. While no absolute ages can be obtained from the sediments in the Tintina Trench, the extensive polarity sequence constrains the timing of glaciations to a considerably greater degree than was previously possible for this region. The magnetostratigraphy of the Tintina Trench sites can be compared in part to the fluvial, glaciofluvial, and loessic deposits in the nearby Dawson area of Central Yukon (Froese et al. 2000, Westgate et al. 2003), where tephras provide absolute ages, and stratigraphic units contain an extensive late Cenozoic climate proxy for northwestern North America (eastern Beringia). In this study, we present new paleomagnetic polarity data and establish a magneto-lithostratigraphy describing glacial, interglacial and preglacial deposits in the Tintina Trench. These deposits are referred to as the West Tintina Trench Allogroup (see Duk-Rodkin et al., 2009) and provide a broad framework for establishing a paleoclimate record for the northern Canadian Cordillera.
Bibliography of Canadian Geomorphology