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Periodic JöKulhlaups from Pleistocene Glacial Lake Missoula—New Evidence from Varved Sediment in Northern Idaho and Washington

  • Richard B. Waitt (a1)
Abstract

Newly examined exposures in northern Idaho and Washington show that catastrophic floods from glacial Lake Missoula during late Wisconsin time were repeated, brief jökulhlaups separated by decades of quiet glaciolacustrine and subaerial conditions. Glacial Priest Lake, dammed in the Priest River valley by a tongue of the Purcell trench lobe of the Cordilleran ice sheet, generally accumulated varved mud; the varved mud is sharply interrupted by 14 sand beds deposited by upvalley-running currents. The sand beds are texturally and structurally similar to slackwater sediment in valleys in southern Washington that were backflooded by outbursts from glacial Lake Missoula. Beds of varved mud also accumulated in glacial Lake Spokane (or Columbia?) in Latah Creek valley and elsewhere in northeastern Washington; the mud beds were disrupted, in places violently, during emplacement of each of 16 or more thick flood-gravel beds. This history corroborates evidence from southern Washington that only one graded bed is deposited per flood, refuting a conventional idea that many beds accumulated per flood. The total number of such floodlaid beds in stratigraphic succession near Spokane is at least 28. The mud beds between most of the floodlaid beds in these valleys each consist of between 20 and 55 silt-to-clay varves. Lacustrine environments in northern Idaho and Washington therefore persisted for two to six decades between regularly recurring, colossal floods from glacial Lake Missoula.

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This list contains references from the content that can be linked to their source. For a full set of references and notes please see the PDF or HTML where available.

E. Antevs (1951). Glacial clays in Steep Rock Lake, Ontario, Canada Geological Society of American Bulletin 62 1223 1262

G.M. Ashley J.B. Southard J.C. Boothroyd (1982). Deposition of climbing-ripple beds—A flume simulation Sedimentology 29 67 79

V.R. Baker (1973). Paleohydrology and Sedimentology of Lake Missoula Flooding in Eastern Washington: Geological Society of America Special Paper 144

J.H. Bretz (1969). The Lake Missoula floods and the Channeled Scabland Journal of Geology 77 505 543

J.H. Bretz H.T.U. Smith G.E. Neff (1956). Channeled Scabland of Washington—New data and interpretations Geological Society of America Bulletin 67 957 1049

R.C. Bunker (1982). Evidence of multiple late-Wisconsin floods from glacial Lake Missoula in Badger coulee, Washington Quaternary Research 18 17 31

R.B. Waitt Jr. (1980). About forty last-glacial Lake Missoula jökulhlaups through southern Washington Journal of Geology 88 653 679

R.B. Waitt Jr. (1985). Case for periodic, colossal jökulhlaups from Pleistocene glacial Lake Missoula Geological Society of America Bulletin in review

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Quaternary Research
  • ISSN: 0033-5894
  • EISSN: 1096-0287
  • URL: /core/journals/quaternary-research
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