HR: 1330h
AN: H52A-1180    [PDF]
TI: Catastrophic Floods Through the Eastern Outlets of Glacial Lake Agassiz: Drainage Routes and Event Magnitudes
AU: * Leverington, D W
EM: leveringtond@nasm.si.edu
AF: Center for Earth and Planetary Studies, National Air and Space Museum, Smithsonian Institution, Washington, DC 20560 United States
AU: Teller, J T
EM: tellerjt@ms.umanitoba.ca
AF: Department of Geological Sciences, University of Manitoba, Winnipeg, MB R3T 2N2 Canada
AB: Glacial Lake Agassiz was the largest lake in North America during the last deglaciation, extending over a total of 1.5 million km$^{2}$ before its final drainage at about 7700 $^{14}$C yr B.P. Over its 5000-calendar-year history, Lake Agassiz was the source of numerous catastrophic outbursts, the largest of which may have influenced climate in the North Atlantic region by disrupting oceanic thermohaline circulation. New high-resolution paleotopographic reconstructions of the eastern outlets of Lake Agassiz provide a foundation for understanding the complex manner in which terrain morphology controlled the routing of overflow through the eastern outlets during the lake's Nipigon Phase (ca. 9400 - 8000 $^{14}$C yr B.P.), and for understanding the causes of outlet-driven declines in lake level during that period. Although flow paths across the divide between the Agassiz and Nipigon basins were numerous, eastward releases from Lake Agassiz to glacial Lake Kelvin (modern Lake Nipigon) were channeled downslope into a relatively small number of major channels that included the valleys of modern Kopka River, Ottertooth Creek, Vale Creek, Whitesand River, Pikitigushi River, and Little Jackfish River. From Lake Kelvin, these waters overflowed into the Superior basin and ultimately flowed into the Atlantic Ocean. The many lowerings in lake level between stages of the Nipigon Phase, controlled by topography and the position of the retreating southern margin of the Laurentide Ice Sheet, had magnitudes of up to 58 m, although some of these drawdowns may have occurred as multiple individual events that could have been as small as several meters. The volumes of water released in association with drops in lake level may have been as great as 8100 km$^{3}$, and for all Nipigon stages were probably between about 140 and 250 km$^{3}$ per meter of lowering.
DE: 1821 Floods
DE: 1824 Geomorphology (1625)
SC: Hydrology [H]
MN: 2003 Fall Meeting