Michael L. Cummings
Economic geology, alteration geochemistry and mineralogy
Long-term research interests are centered around quandrangle mapping of the middle Miocene rift systems of eastern Oregon. I am particularly interested in the relations among statigraphic (volcanic and sedimentary), structural, and thermal evolution of these systems. The approach is multidisciplinary and includes geochemical, geophysical, mineralogical, paleontological, and structural studies. We are presently mapping in the area west of Beulah Reservoir near Juntura, Oregon. The map area lies west of the Oregon-Idaho graben, a newly defined middle Miocene graben system that evolved between 15.5 and 10.5 Ma. This graben was defined by cooperative mapping with Mark Ferns (Oregon Department of Geology and Mineral Industries, Baker City, OR) and Jim Evans (U.S. Geological Survey, Spokane, WA). In the Juntura area the Beulah fault zone marks an important change in structural and stratigraphic patterns. East of the zone, flows correlated with the Grande Ronde and Imnaha formations of the Columbia River Basalt Group are overlain by the 15.3 Ma Dinner Creek Welded Tuff and the Hunter Creek Basalt. These units form the western structural block for the Oregon-Idaho graben. The western margin of this block is the Beulah fault zone. In 1996 summer field camp worked on Castle Rock, a large ridge that lies northwest of the fault zone. Approximately 800 m of basalt are exposed on Castle Rock and the basalt section is overlain by remanants of what appears to be the Dinner Creek Welded Tuff. The basalts are subdivided into four series based on field characteristics and geochemistry determined by instrumental neutron activation. The lowest section includes basalt flows with Cr concentrations of 200 to 350 ppm and La concentrations between 6 and 12 ppm. We suspect that much of the section exposed at Castle Rock is actually older than the Columbia River Basalt Group. The distribution of units also suggests that the Beulah fault zone may have a significant strike slip component in its history. In the summer of 1997 we will extend mapping either to the west of the Beulah quadrangle to complete stratigraphic context for diatomite mines in that area, or continue mapping north and east of Castle Rock. In either case, we are unsure what units are like and their stratigraphic context. The mapping will be conducted as field camp for the Department.
Two other projects continue in the Oregon-Idaho graben. Kaye Savage and I are slowly working on an alteration zone that developed in an andesitic flow. The extensive loss of mass and generation of secondary porosity suggests that the alteration system was vapor dominated. A poster on this research was presented at the Cordilleran Section of GSA in Fairbanks, Alaska in May, 1995. A second study with graduate student Suzanne Hess looks at the structural evolution of the Dry Creek Buttes fault zone. This fault zone is a major structural zone that controls location of hot spring gold prospects, intrusions, and stratigraphic patterns in the central part of the Oregon-Idaho graben. Ken Cruikshank has been helping with this project. During field mapping in 1995, large north- and northeast-striking kink folds were defined. These features had been recognized during our earlier mapping, but the detailed work has defined their characteristics.
Ansel Johnson, Ken Cruikshank and I co-authored a paper published by the Nevada Geological Society on gravity studies we completed in the Oregon-Idaho graben in the vicinity of the hot spring precious-metals prospects at Red Butte and Quartz Mountain. The paper presents gravity and heat-flow models for a mafic intrusion that we believe provided the heat to drive the geothermal systems that formed these prospects. The paper that formally describes the Oregon-Idaho graben is nearing completion and will be submitted in early 1997 to the Bulletin of the GSA. The paper is co-authored with Jim Evans, U.S.G.S, Mark Ferns, DOGAMI, and Kate Lees, Open University. Final work on diagrams is in progress and "friendly" reviews have been completed.
I continue to expand research in hydrogeologic studies. Ben Perkins, a graduate student in the Environmental Sciences and Resources (ESR) Ph.D. program is beginning work on the chemical evolution of Harney Lake. We are particularly interested in evaporation from the shore zone and generation of bio-mineral crusts containing minerals that are far from saturation in the lake water. We believe that wind erosion and selective redissolution of these crusts plays an important role in evolution of lake-water chemistry. Bea Ritchie, also in the ESR Ph.D. program continues her research on the chemistry of hot springs and crater lakes on Kusatsu-Shirane volcano in Japan. She is conducting analytical work on water samples that were collected over a period of years. Her interest is in the efffects of eruptive processes on chemical composition and how to use these changes to improve monitoring of volcanic processes.
In the Portland area, I continue to work with Ansel Johnson and Ken Cruikshank on the hydrology of Government Island in the Columbia River. Shawn Eisner is working on this project for his M.S. thesis. 1996 was the first year since the project started that there was enough water in the system to keep a flooded area the entire year. However, 1996 has been a record rainfall year and at times Government Island was nearly under water. Evapo-transpiration rates are of interest in determining a water budget for the island. This project is for the Port of Portland and is part of their mitigation program for expansion of runways at Portland International Airport.
Recent arrival of Georg Grathoff, a recent Ph.D. from the University of Illinois is encouraging expanded research in clay mineralogy. We are beginning to examine the role of clay minerals in the distribution of arsenic in the ground water of western Oregon.
In September, Mark Scott and I completed a study that examined the geology and hydrology of southeastern Oregon with the intention of finding "blind" geothermal systems. The project was completed for the Bonneville Power Administration. Part of the product is a GIS database for the southeastern 1/3 of Oregon. The database includes hydrologic, geologic, heat flow, thermal gradient, neotectonic, and water chemistry for this region. The database is available through the Department of Geology Home Page. In the fall of 1995 we completed an strontium isotope study of bed rock units and thermal and non-thermal springs in the Alvord Valley. This report is also available on the Home Page. This study was supported by the Bureau of Land Management as a series of studies on geothermal potential in the Borax Lake area of the Alvord Valley. Since the lake is home of the Borax Lake Chub, a rare and endangered species, the question of geothermal exploration and development is driving our research. I am now working on a report on chemical and isotopic variability of Borax Lake on an annual cycle. In early December, 1996, Ken Cruikshank, Ansel Johnson, and I worked with Sean Wilson to establish a detailed survey on the Borax Lake mound. Sean will use the grid as a basis for his M.S. study on the stability of this feature. The mound is an erosional remnant underlain by saturated diatomite and protected by a porous sinter sheet that extends out from the shores of Borax Lake.
Cummings, M. L., Johnson, A. G., and Cruikshank, K. M., 1996, Intragraben fault zones and hot-spring deposits in the Oregon-Idaho graben: A Geophysical study, in A.R. Coyner and P. L. Fahey, eds., Geology and Ore Deposits of the America Cordillera: Geological Society of Nevada Symposium Reno/Sparks, Nevada, April, 1995, p. 1047-1062.
Cummings, M. L., 1995, Intragraben fault zones, volcanism, and geothermal evolution in the Oregon-Idaho graben U.S.A.: PACRIM Congress 1995, The Australasian Institute of Mining and Metallurgy Publication Series 9/95, p. 169-174.
Cummings, M. L., Evans, J. G., and Ferns, M. L., 1994, Stratigraphic and structural evolution of the Middle Miocene Oregon-Idaho graben, Malheur County, Oregon, in, D. A. Swanson and R. S. Haugerud, editors, Geologic field trips in the Pacific Northwest: 1994 Geological Society of America Meeting: University of Washington, Department of Geology, p. 1G1 - 1G20.
Cummings, M. L., St John, A. M., Sturchio, N. C., 1993, Hydrogeochemical characterization of the Alvord basin geothermal area, Harney County, Oregon, USA: Proceedings 15th New Zealand Geothermal Workshop 1993, p. 119-124.
Ferns, M. L., Evans, J. G., Cummings, M. L., 1993, Geologic map of the Mahogany Mountain 30 x 60 minute quadrangle, Malheur County, Oregon, and Owyhee County, Idaho: Oregon Department of Geology and Mineral Industries Geological Map Series GMS-78, scale 1:100,000.
Ferns, M. L., Brooks, H. C., Evans, J. G., Cummings, M. L., 1993, Geologic map of the Vale 30 x 60 minute quadrangle, Malheur County, Oregon, and Owyhee County, Idaho: Oregon Department of Geology and Mineral Industries Geological Map Series GMS-77, scale 1:100,000.
Cummings, M. L., and W. R. McCulloch, 1992, Geochemistry and origin of amphibolite and ultramafic rocks, Branham Lakes Area, Tobacco Root Mountains, southwestern Montana, U.S.A. in M. J. Bartholomew, D. W. Hyndman, D. W. Mogk, R. Mason, eds, Basement Tectonics 8: Characterization and comparison of Ancient and Mesozoic continental margins-Proceedings of the 8th International Conference on Basement Tectonics (Butte, Montana, 1988): Kluwer Academic Publishers, Dordrecht, The Netherlands, p. 323-340.
Ferns, M. L., and Cummings, M. L., 1992, Geology and Mineral Resources of The Elbow Quadrangle, Malheur County, Oregon: Oregon Department of Geology and Mineral Industries GMS-62, Scale 1:24,000.
Papers in Progress:
Cummings, M. L., Evans, J. G., Ferns, M. L., and Lees, K. R., Stratigraphic and structural evolution of a middle Miocene synvolcanic graben: The Oregon-Idaho graben: to be submitted to GSA Bulletin.
Cummings, M. L. and St. John, A. M., The Holocene evolution of Borax Lake, Pueblo Valley, Oregon:
Cummings, M. L., Geology and mineral resources of the Beulah quadrangle, Malheur and Harney Counties, Oregon: 1:25,000.
Cummings, M. L., Geology and mineral resources of the DeArmond Mountain quadrangle, Malheur County, Oregon: 1:25,000.
G 200 Bend Field Study (Volcanic areas near
G 315 Metamorphic Petrology
G 446/546 Economic Geology
I am interested in improving education opportunities and quality at all levels. I am developing a grant proposal to the Science and Mathematics Consortium for Northwest Schools in cooperation with the school districts of Harney, Lake, and Grant Counties for training elementary teachers. The program is planned for summer, 1997 at the Malheur Field Station, near Burns, Oregon. We hope to integrate the skills of local school districts, higher education institutions that support the Field Station, local offices of Federal and State agencies, and Field Station staff as a model of teacher training in sparsely populated rural areas.
The K-12 program at the Cordilleran Section of the Geological Society of America Annual Meeting in Portland, April, 1996 was very successful. Workshops, field trips and field studies, and a special meeting on earthquake preparedness in the Pacific Northwest were well attended by K-12 teachers. We estimate 75 to 80 teachers participated in various aspects of the program. .
I have served as a mentor for high school students for five summers. These students participate in a program offered through Saturday Academy. Saturday Academy is housed at the Oregon Graduate Institute and matches high school students with mentors for an eight week summer program. This program, Apprenticeships in Science and Engineering, places high school students in the work environment. I have been mentor for 11 students. In some cases, the projects have resulted in publications or abstracts at professional meetings where the student is the presenter.
At Portland State I continue to develop approaches to classroom activities for general education classes and major courses. My Geology of the Oregon Country course, a general education course, takes non-science majors through the process by which we identify, define, execute, and report on research projects. The student-generated projects work well and most students accomplish substantial projects. Three progress reports are due during the term. The first reports on background research conducted in support of the project. The second reports on field investigations conducted to gather information for the project. The third reports on laboratory methods used and additional literature research conducted to bring the project to a conclusion. The last report is a formal integration of the research in the format of a professional contribution and is supported by a poster session held during the final exam period. Students may work in groups or individually. I usually find the drop rate in the course is about 30% when the students learn what is expected. However, those that complete the course show considerable increase in their understanding of science and usually produce solid projects. I find this approach works well with junior and senior students with at least one geology course in their background. I have tried this approach at the sophomore level and find that students lack skills needed for this approach. At this level I believe a more structure inquiry format is needed. I will be experimenting with this approach this spring term.
Last Update: Saturday, December 28, 1996