Gravity radar and seismic investigations to help determine geologic hydrologic and biologic relations in the Nyack Valley northwestern Montana

Harrison, Nathan E., M.S., Spring 2004 Geology Gravity, Radar and Seismic Investigations to Help Determine Geologic, Hydrologie, and Biologic Relations in the Nyack Valley, Northwestern Montana. Director: Dr. Steven Sheriff Interdisciplinary research on the intermontane Nyack floodplain of the Flathead River in northwestern Montana focuses on the relationships between physical and biological processes linking water, nutrients, and the evolution of the floodplain. As part of that research, I determined the configuration of the valley fill and its internal stratification. 150 new observations of the complete Bouguer anomaly indicate a maximum depth to bedrock of about 200 meters in the Nyack Valley. The signal from 79 lines of Ground Penetrating Radar (GPR) data, collected with a 50 mhz antenna system indicate a reasonably consistent layer of coarse quaternary alluvium at approximately 25 meters depth.. Seismic refraction results, from a 24-channel instrument also indicate a stratigraphie boundary at 30 meters (commonly 1400 m/s over 2100 m/s), as well as bedrock in some of the surveys.

[1]  Laurent Labeyrie,et al.  Coherent patterns of ice-rafted debris deposits in the Nordic regions during the last glacial (10–60 ka) , 2001 .

[2]  J. Matthiessen,et al.  Marine ice-rafted debris records constrain maximum extent of Saalian and Weichselian ice-sheets along the northern Eurasian margin , 2001 .

[3]  Rabi N. Bohidar,et al.  Delineating Depth to Bedrock Beneath Shallow Unconfined Aquifers: A Gravity Transect Across the Palmer River Basin , 2001, Ground water.

[4]  R. A. Overmeeren,et al.  Radar facies of unconsolidated sediments in The Netherlands: A radar stratigraphy interpretation method for hydrogeology , 1998 .

[5]  Richard W. Saltus,et al.  Upper-crustal structure beneath the Columbia River Basalt Group, Washington: gravity interpretation controlled by borehole and seismic studies , 1993 .

[6]  M. K. Lee.  A new gravity survey of the Lake District and three-dimensional model of the granite batholith , 1986, Journal of the Geological Society.

[7]  Lindrith Cordell,et al.  Iterative three-dimensional solution of gravity anomaly data using a digital computer , 1968 .

[8]  M. Cushing,et al.  Investigating alluvial and tectonic features with ground-penetrating radar and analyzing diffractions patterns , 2000 .

[9]  J. Andrews,et al.  Spatial and temporal patterns of iceberg rafting (IRD) along the East Greenland margin, ca. 68°N, over the last 14 cal.ka , 1997 .

[10]  K. Constenius.  Structural Configuration of the Kishenehn Basin Delineated by Geophysical Methods, Northwestern Montana and Southeastern British Columbia , 1988 .

[11]  D. Harris.  Crustal structure of northwestern Montana , 1985 .

[12]  D. M. Kulik.  Preliminary Gravity Study of Glacier National Park, Montana , 1982 .