HR: 1340h
AN: H33D-1412    [Abstracts]
TI: The Geology of the Western Margin of the Upper Klamath Basin, Oregon
AU: * Mertzman, S A
EM: stan.mertzman@fandm.edu
AF: Stanley A. Mertzman, Department of Earth and Environment Franklin and Marshall College, Lancaster, PA 17604-3003
AB: The aspect of my work and that of my students that will be of interest to this group is the bedrock geologic mapping that has been completed between Mt. Shasta-Medicine Lake Highland region to the south and the southern boundary of Crater Lake National Park to the north. Combining the mapping with lithologic, structural, and geochronology information provides the foundation on which a geologic history of an area can be constructed. Within this region Western Cascades volcanic rocks, ranging in age from 22 to 20 M. Y. old, are overlain by High Cascades volcanic rocks that are ? 7.6 M. Y. old. There is one anomalous area located on the Oregon-California border where volcanic rocks in the age range 14 to 12.5 M. Y. old are abundant. In general the older the volcanic rock the lower both the porosity and permeability will be and therefore affect groundwater flow characteristics. In three regions where the unconformity between the Western Cascades and the High Cascades is exposed near the Klamath Basin western margin, it does so at an elevation of approximately 4500 feet. The erosion surface suggests modest relief, which further indicates that the total thickness of volcanic rocks of High Cascades age is not great in a number of areas. The thickness or rather the thinness of these ? 7.6 M. Y. old volcanic rocks coupled with fault location information may help to constrain well recharge calculations. Also, the limited geographic extent of individual volcanic units and the large number of volcanic point sources with their attendant pyroclastic material will affect the regional hydrology; it makes for a heterogeneous scene when it comes to modeling a variety of hydrologic parameters.
DE: 1199 General or miscellaneous
DE: 1829 Groundwater hydrology
DE: 1899 General or miscellaneous
DE: 8486 Field relationships (1090, 3690)
SC: Hydrology [H]
MN: Fall Meeting 2005