Shallow Geophysical Imaging of the Olympia Anomaly: an Enigmatic Structure in the Southern Puget Lowland, Washington State GEOSPHERE; V
Research Paper GEOSPHERE Shallow geophysical imaging of the Olympia anomaly: An enigmatic structure in the southern Puget Lowland, Washington State GEOSPHERE; v. 12, no. 5 Jack K. Odum1, William J. Stephenson1, Thomas L. Pratt2, and Richard J. Blakely3 1Geologic Hazards Science Center, U.S. Geological Survey, PO Box 25046, MS 966, Denver, Colorado 80225, USA ddoi:10.1130/GES01248.1 2U.S. Geological Survey, 12201 Sunrise Valley Drive, MS 905, Reston, Virginia 20192, USA 3U.S. Geological Survey, 345 Middlefield Road, MS 989, Menlo Park, California 94025, USA 9 figures CORRESPONDENCE: odum@ usgs .gov ABSTRACT bases, and high-tech industries. The complex tectonic structure in the region results from the oblique northeast-directed subduction of the Juan de Fuca CITATION: Odum, J.K., Stephenson, W.J., Pratt, Gravity and magnetic anomalies suggest that the Olympia structure be- oceanic plate beneath western North America (Fig. 1A), northwest motion of T.L., and Blakely, R.J., 2016, Shallow geophysi cal imaging of the Olympia anomaly: An enigmatic neath the southern Puget Lowland (western Washington State, U.S.) vertically the Pacific plate along the San Andreas fault system, and clockwise rotation structure in the southern Puget Lowland, Washing displaces Eocene Crescent Formation strata. Northeast of the Olympia struc- and northward motion of the Coast Range block (Wells et al., 1998; Wells and ton State: Geosphere, v. 12, no. 5, p. 1617–1632, ture, middle Eocene Crescent Formation is beneath 4–6 km of Paleogene–Neo- Simpson, 2001; Blakely et al., 2002; Van Wagoner et al., 2002; Johnson et al., doi:10.1130/GES01248.1.
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