Turbidite megabeds in an oceanic rift valley recording jokulhlaups of late Pleistocene glacial lakes of the Western United States

Author(s): Zuffa, G. G.; Normark, W. R.; Serra, F.; Brunner, C. A.
Author Affiliation(s): Primary:
Universita di Bologna, Dipartimento di Scienze della Terra, Bologna, Italy
Other:
U. S. Geological Survey, United States
University of Southern Mississippi, United States
Volume Title: Journal of Geology
Source: Journal of Geology, 108(3), p.253-274. Publisher: University of Chicago Press, Chicago, IL, United States. ISSN: 0022-1376 CODEN: JGEOAZ
Note: In English. 59 refs.; illus., incl. sects., 2 tables, sketch maps
Summary: Escanaba Trough is the southernmost segment of the Gorda Ridge and is filled by sandy turbidites locally exceeding 500 m in thickness. New results from Ocean Drilling Program (ODP) Sites 1037 and 1038 that include accelerator mass spectrometry (AMS) 14C dates and revised petrographic evaluation of the sediment provenance, combined with high-resolution seismic-reflection profiles, provide a lithostratigraphic framework for the turbidite deposits. Three fining-upward units of sandy turbidites from the upper 365 m at ODP Site 1037 can be correlated with sediment recovered at ODP Site 1038 and Deep Sea Drilling Program (DSDP) Site 35. Six AMS 14C ages in the upper 317 m of the sequence at Site 1037 indicate that average deposition rates exceeded 10 m/k.yr. between 32 and 11 ka, with nearly instantaneous deposition of one ∼60-m interval of sand. Petrography of the sand beds is consistent with a Columbia River source for the entire sedimentary sequence in Escanaba Trough. High-resolution acoustic stratigraphy shows that the turbidites in the upper 60 m at Site 1037 provide a characteristic sequence of key reflectors that occurs across the floor of the entire Escanaba Trough. Recent mapping of turbidite systems in the northeast Pacific Ocean suggests that the turbidity currents reached the Escanaba Trough along an 1100-km-long pathway from the Columbia River to the west flank of the Gorda Ridge. The age of the upper fining-upward unit of sandy turbidites appears to correspond to the latest Wisconsinan outburst of glacial Lake Missoula. Many of the outbursts, or jokulhlaups, from the glacial lakes probably continued flowing as hyperpycnally generated turbidity currents on entering the sea at the mouth of the Columbia River.
Year of Publication: 2000
Research Program: DSDP Deep Sea Drilling Project
ODP Ocean Drilling Program
Key Words: 24 Surficial Geology, Quaternary Geology; Absolute age; Acoustical methods; C-14; Carbon; Cenozoic; Clastic sediments; Columbia River; Correlation; DSDP Site 35; Dates; Deep Sea Drilling Project; East Pacific; Escanaba Trough; Foraminifera; Geophysical methods; Geophysical profiles; Geophysical surveys; Glacial features; Glacial lakes; Gorda Rise; Heavy minerals; High-resolution methods; Invertebrata; Isotopes; Jokulhlaups; Lake Missoula; Lakes; Leg 169; Leg 5; Lithostratigraphy; Magnetic susceptibility; Marine sediments; North Pacific; Northeast Pacific; ODP Site 1037; ODP Site 1038; Ocean Drilling Program; Pacific Ocean; Paleomagnetism; Physical properties; Pleistocene; Protista; Provenance; Quaternary; Radioactive isotopes; Reflection methods; Rift zones; Sand; Sediment transport; Sedimentation; Sedimentation rates; Sediments; Seismic methods; Seismic profiles; Seismic stratigraphy; Surveys; Turbidite; United States; Upper Pleistocene; Upper Wisconsinan; Volcaniclastics; Western U.S.; Wisconsinan
Coordinates: N403000 N411000 W1273000 W1273000
Record ID: 2000045702
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute.