Paleomagnetic evidence for multiple Late Pliocene - Early Pleistocene glaciations in the Klondike area, Yukon Territory

The Late Pliocene - Early Pleistocene terraces of the Klondike area provide a conformal record of sedimentation which marks the transition from pregla cial to glacial conditions, and is one of the most complete records of glac iation and interglaciation in the northern Cordillera. Preglacial sedimenta tion is recorded in the Lower White Channel gravel that contains a reverse- normal polarity sequence. A re-aggradation of the nonglaciated valleys of t he goldfields in response to Late Pliocene cooling is recorded by the Upper White Channel gravel, which is characterized by a dominant normal polarity with a lower reversal likely associated with the first ice-wedge casts. Kl ondike gravel interfingers with Upper White Channel and is normally magneti zed, indicating an equivalent magnetostratigraphic unit. This glaciofluvial gravel provides evidence of extra-basinal clasts, marking a major reorgani zation of drainage associated with the first advance of the Cordilleran Ice Sheet in western Yukon Territory correlated with the Gauss chron (> 2.58 M a). An intermediate terrace in Klondike valley is overlain by 8 m of fluvia l and glaciofluvial gravel named the Midnight Dome gravel. This gravel is m antled by 15 m of loess and hillslope deposits, named the Midnight Dome loe ss, which preserve at least three interglacial pollen assemblages, and a re verse-normal-reverse-normal polarity sequence assigned to the late Matuyama chron, including Jaramillo subchron (1.07-0.99 Ma), and early Brunhes chro n (< 0.78 Ma). The oldest glaciations here, based on the preferred interpre tation, extend well into the Pliocene (> 2.58 Ma) making these among the ol dest glacial sediments in North America.