RECENT FACULTY AND STUDENT
GEOLOGY RESEARCH

Our geology research efforts at Eastern Oregon University focus on unraveling the geologic history of the Grande Ronde Valley and nearby areas in Northeast Oregon.  We began by describing the modern sediments of the Grande Ronde River and the alluvial fans that border the Grande Ronde Valley.  A  detailed study of the La Grande terrace gravels by Sandra Pilling plus recent C-14 dating of a mammoth tooth and soils studies by U.S. Geological Survey geologist Stephen Personius have helped us to show that the La Grande terrace gravels were deposited by braided streams flowing on the surface of a large alluvial fan deposited ~150,000 years ago during the Bull Lake Glaciation.  These gravels were incised and the present day La Grande alluvial fan was deposited ~15,000 years ago during the Pinedale Glaciation.  The Grande Ronde River has been incising into the La Grande alluvial fan ever since (Fig. 1).

Recent studies by Glen Fromwiller and Jay Van Tassell have focused on describing the grain size, composition and diatom content of sediment samples from five water wells in the valley.  This research is being done in conjunction with field mapping of the area by Mark Ferns and Vicki McConnell of the Oregon Department of Geology and Minerals (Baker City) and seismic profiling across the valley conducted by the Boise State University Center for the Geophysical Investigation of the Shallow Subsurface.  1999 marked the discovery of several ash layers in the sedimentary sequence, two of which have been Ar-Ar dated at ~7.5 and 3 Ma.  Our results suggest that the Grande Ronde Valley began to form ~9 m.y. ago.  The valley floor has been sinking at rates of ~0.07-0.18 mm/yr, with the greatest rates of subsidence occurring on the west side of the valley, resulting in a net dropping of the west side of the valley at a rate 0.03 mm/yr faster than the east side of the valley over the past 9 m.y. (Fig. 2).

Diatoms proved to be the key in correlating sedimentary units across the basin.  Two zones of very abundant diatoms in the sequence suggest two wet periods during the history of the basin.  The lower zone is rich in diatoms which suggest that the Grande Ronde Valley was occupied by marshes and shallow lakes ~8.5-7.5 m.y. ago.  The upper zone is rich in diatoms which suggest both shallow and deep lakes between ~4-2.5 m.y. ago.

In the spring of 2000, catfish, sunfish and minnow bones were discovered just above bedrock in a well near Imbler, Oregon.  These have been examined by Jerry Smith of the University of Michigan and confirm that the Grande Ronde Valley was linked to the Columbia River system at ~ 3-4 Ma.  Examination of the diatoms in the sequence by J. Platt Bradbury (U.S. Geological Survey, retired) revealed 2 very rare species which suggest a link to  Lake Idaho in the Snake River Plain at the same time.  The chemical composition of the ~3.0 Ma ash is very similar to a Lake Idaho tephra of the same age (similarity coefficient = 0.93).  This confirms Livingstonís (1928) theory that Lake Idaho once drained through the Grande Ronde Valley.  It also provides an alternate route in addition to Hells Canyon for the migration of fish and muskrats from the Lake Idaho area to the Pasco, Washington, area ~ 3-4 m.y. ago.  At approximately 2 Ma, the lakes in the Grande Ronde Valley drained abruptly, perhaps in response to the capture of the Snake River by a tributary of the Salmon River in the Hells Canyon area (Fig. 4).

Our latest student research efforts are focused on examining a possible Lake Idaho outburst gravel in the headwaters of Catherine Creek (Adam Isaacson); unraveling the structure and paleobiology of the Jurassic Hurwal Shale along Eagle Creek (Tammy Dunlavey); piecing together the relationships between topography, geology and the distribution of ladyslippers in the Pumpkin Ridge area (Laurie Allen); examining soil formation differences on glacial moraines in the Anthony Lakes area (Bob Brown); and documenting paleoflow directions of a late Miocene river system in the Starkey area (Drew Sherman).
 

PUBLICATIONS

Van Tassell, J., Ferns, M., McConnell, M. and Smith, G.V., 2002, Neogene history of the Grande Ronde Valley, NE Oregon:  Geological Society of America Abstracts with Programs, v. 34, no. 5, p. A-39.

Ferns, M., McConnell, V., Madin, I., and Van Tassell, J., 2001, Geologic Map of the  Imbler quadrangle:  Salem, Oregon Department of Geology and Mineral  Industries, 1:24,000, in press.

Van Tassell, J., Ferns, M., McConnell, M. and Smith, G.V., 2001, The Imbler fish fossils, Grande Ronde Valley, NE Oregon, and the Pliocene Lake Idaho-Columbia River connection:  Oregon Geology, v. 63, no. 3 (Summer), p. 77-84, 89-96.

Brown, R., Collier, J., Dunlavey, T., Erwin, D., Fritz, A-M., Healy, J., High, M.,  Isaacson, A., Line, R., Niimoto, K., Peterson, M.,   Rejzek, J., Schwehr, T.,  Taylor, A., Waldinski, P., and Van Tassell, J., 2001, Sedimentology and age of  the Pleistocene La Grande terraces, La Grande, Oregon:  Eastern Oregon Science  Journal, v. 16, p. 37-40.

Dunlavey, T., and Van Tassell, J., 2001, Graben vs. strike-slip basin models for the origin of the La Grande  Basin, northeast Oregon:  Analogue models:  Eastern Oregon Science Journal, v.  16, p. 47-55.

Van Tassell, J., Ferns, M.L., and McConnell, V.S., 2000, Neogene sediment  accumulation and subsidence rates, La Grande Basin, northeast Oregon:   Geological Society of America Abstracts with Programs, v. 32, no. 6, p. A73-74.

Fromwiller, G., and Van Tassell, J., 1999, Pleistocene sedimentation in the La Grande  Basin, northeast Oregon:  Eastern Oregon Science Journal, v. 15, p. 34-38.  (recent dating suggests this sequence actually is Miocene-Pliocene in age)

Alberts, J., Barker, J., Batten, N., Brown, J., Ikegami, M., Keene, J., Line, R., Mertz,  B., Pratt, A., Rogers, T., Sherman, D., Strafford, V., and Zubin, B., 1999,  Boulder size, soil profiles and maximum lichen diameters of the younger lateral  moraine, Antone Creek, Elkhorn Mountains, northeast Oregon:  Eastern Oregon  Science Journal, v. 15, p. 27-33.

Harmon, J.K., 1998, Sediments of the Homer, Alaska, area:  Eastern Oregon Science  Journal, v. 14, p. 34-38.

Pilling, S., 1998, Sedimentology of a Pleistocene outcrop, Waite Bluff, Foothill Road,  south of La Grande, OR:  Eastern Oregon Science Journal, v. 14, p. 29-33.

Compos, J., Fromwiller, G., Hubbard, R., Johnson, J., Kalmbach, D., Phelps, T., and  Smith, M., 1998, Quaternary surficial sediments of the Grande Ronde Basin,  northeast Oregon:  Eastern Oregon Science Journal, v. 14, p. 21-23.

Harmon, J., Johnson, M., Spring, E., and Swanger, M., 1998, Pleistocene alluvial  deposits of North Powder Valley and Recent stream deposits of Anthony Lakes,  Antone Creek and the Powder River, northeast Oregon:  Eastern Oregon Science  Journal, v. 14, p. 21-23.

Van Tassell, J., 1998, A 1-m.y. record of Quaternary sedimentation in the Grande Ronde  strike-slip basin, eastern Oregon:  Geological Society of America Abstracts with  Programs, v. 30, no. 6, p. 29. (recent dating shows that the record is actually 9  m.y. long!)

Johnson, D.C., 1997, Sugarloaf Mountain tor, Blue Mountains, northeastern Oregon:   Eastern Oregon Science Journal, v. 13, p. 30-32.
Fromwiller, G., 1997, Grande Ronde Valley landslides, eastern Oregon:  Eastern Oregon  Science Journal, v. 13, p. 27-30.

Hubbard, R., and Smith, M., 1997, Analysis of fractures in the vicinity of the Cove Hot  Springs, Grande Ronde Valley, northeastern Oregon:  Eastern Oregon Science  Journal, v. 13, p. 23-26.

Swanger, M., 1997, Structural geology of the John Day Formation, Warm Mineral  Springs area, northeastern Oregon:  Eastern Oregon Science Journal, v. 13, p. 20- 23.

Erwin, D., Rank, D., and Van Tassell, J., 1997, Alluvial fans of the Grande Ronde  Valley, eastern Oregon:  Eastern Oregon Science Journal, v. 13, p. 14-19.

Van Tassell, J., 1997, Cyclostratigraphy of the Grande Ronde graben, northeast Oregon:   Geological Society of America Abstracts with Programs, v. 29, no. 5, p. 71.

Van Tassell, J., Beam, M., Bishop, J., Brown, S., Hanford, K., McDonald, T.,  Thompson, L., and Wilson, J., 1996, Sedimentology of the Middle Jurassic  Weatherby Formation, northeastern Oregon: Preliminary studies:  Geological  Society of America Abstracts with Programs, v. 25, no. 5, p. 120.

Bishop, J.R. and Van Tassell, J., 1994, Structural geology of an outcrop of the Jurassic  Weatherby Formation along I-84 southwest of Weatherby, Oregon:  Eastern  Oregon Science Journal, v. 10, p. 18-20.

Wilson, J.G., and Van Tassell, J., 1994, Sedimentology of an outcrop of the late Miocene  to early Pliocene lacustrine desposits northeast of Durkee, Oregon:  Eastern Oregon  Science Journal, v. 10, p. 23-26.

Bishop, E.M., Thompson, L.L., and Woodward, J., 1992, Sedimentation and tectonics in the Grande Ronde graben,northeast Oregon: A preliminary assessment:  Geological Society of America Abstracts with Programs, v. 24, no. 5, p. 7.
 
 

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