--> Sediment Diapirism and Gravity Sliding of the 2 Ma Huckleberry Tuff Near the Teton Dam, Idaho: Small-Scale Structural Constraints, by Mark Millard, Robert W. Clayton, and Clayton S. Painter, #50020 (2005)

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Sediment Diapirism and Gravity Sliding of the 2 Ma Huckleberry Tuff Near the Teton Dam, Idaho: Small-Scale Structural Constraints*

By

Mark Millard1, Robert W. Clayton1, and Clayton S. Painter1

 

Search and Discovery Article #50023 (2005)

Posted November 27, 2005

 

*Oral Presentation at Rocky Mountain Section AAPG Annual Meeting, Jackson, Wyoming, September 24-26, 2005. Appreciation is expressed to Lyn George, Technical Program Chair, and Don French, for encouraging the authors to submit this presentation.

  

Click to view presentation in PDF format.

 

1Dept. of Geology, Brigham Young University - Idaho, Rexburg, ID 83460, ( [email protected] )

 

Abstract 

A 20 by 20 km sheet of the 2 Ma Huckleberry Tuff and underlying Pliocene alluvial gravel, basalt, and tuffaceous lacustrine sediments were involved in gravity sliding and flow shortly after deposition of the tuff. Large scale structures are similar to those observed in the Gulf of Mexico resulting from soft-sediment and salt flow, and include overturned anticlines >100 m in amplitude, strike slip faults with up to 1 km displacement, sedimentary diapirs, and an arcuate pull-apart valley 12 km long. Because displacement occurred during compaction but before devitrification, the tuff deformed plastically in its lower parts but contains brittle joints in its upper. The brittle joints were opened during shearing by as much as 1 m. We classify and analyze the orientations of plastic shear zones, plastically deformed joints, orientation of zones within the tuff, and joint sets to document the kinematics of deformation. The small-scale structures are consistent with the secondary deformation and gravity sliding originally proposed by Embree and Hoggan in 1999. Sliding was toward the southwest, resulting in NW-SE fold axes, SW-NE trending strike slip faults, and cooling joints that were plastically sheared toward the southwest. The opened joints played a role in the failure of the Teton Dam in 1976.

 

Location map

 

Teton Dam failure (1976)

 

Selected Bibliography 

Arthur, H.G., 1977, Teton Dam failure, in The Evaluation of Dam Safety (Engineering Foundation Conference Proceedings, Asilomar, Nov. 28-Dec. 3, 1976): American Society of Civil Engineers, New York, p. 61-71.

Christiansen, R.L., and Blank, H.R., Jr., 1972, Volcanic stratigraphy of the Quaternary rhyolite plateau in Yellowstone National Park: U.S. Geol. Survey Prof. Paper 7290B, 18 p.

Christiansen, R.L., 1982, Late Cenozoic volcanism of the Island Park area, eastern Idaho, in Bonnichsen, B., and Breckenridge, R.M., eds., Cenozoic Geology of Idaho: Idaho Bureau of Mines and Geology Bulletin 26, p. 345-Idaho: 368. 368.

Christiansen, R.L., and Embree, G.F., 1987, Island Park, Idaho; Transition from rhyolites of the Yellowstone Plateau to basalts of the Snake River Plain, in Geological Society of America Centennial Field Guide, Rocky Mountain Section, p. 103-108.

Embree, G.F., Hoggan, R.D., 1999, Secondary deformation within the Huckleberry Ridge Tuff and subadjacent Pliocene units near the Teton Dam: Road log to the regional geology of the eastern margin of the Snake River he Plain, Idaho, in Hughes, S.S, Thackray, G.D., eds., Guidebook to the Geology of Eastern Idaho.

Morgan, J.P., Coleman J.M., and Gagliano, S.M., 1968, Mudlumps diapiric structures in Mississippi Delta sediments: AAPG Memoir 8, p. 145-161.

Prostka, H.J., 1977, Joints, fissures, and voids in rhyolite welded ash flow tuff at Teton Dam site, Idaho: U.S. Geological Survey, Open File Report 77-211, 13 p.

Sousa, Jr. N, N., 1999, Features found in flood basalts, Geoscience Reports, vol. 28, p. 1-3