Abstract
Gorda Ridge is the southern segment of the Juan de Fuca Ridge complex, in the north-east Pacific. Along-strike spreading-rate variation on Gorda Ridge and deformation of Gorda Plate are evidence for compression between the Pacific and Gorda Plates. GLORIA sidescan sonographs allow the spreading fabric associated with Gorda Ridge to be mapped in detail. Between 5 and 2 Ma, a pair of propagating rifts re-orientated the northern segment of Gorda Ridge by about 10° clockwise, accommodating a clockwise shift in Pacific-Juan de Fuca plate motion that occurred around 5 Ma. Deformation of Gorda Plate, associated with southward decreasing spreading rates along southern Gorda Ridge, is accommodated by a combination of clockwise rotation of Gorda Plate crust, coupled with left-lateral motion on the original normal faults of the ocean crust. Segments of Gorda Plate which have rotated by different amounts are separated by narrow deformation zones across which sharp changes in ocean fabric trend are seen. Although minor lateral movement may occur on these NW to WNW structures, no major right-lateral movement, as predicted by previous models, is observed.
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References
AtwaterT., 1970, Implications of Plate Tectonics for the Cenozoic Tectonic Evolution of Western North America, Geol. Soc. America Bull. 81, 3513–3536.
AtwaterT. and MudieJ. D., 1973, Detailed Near-Bottom Geophysical Study of the Gorda Rise, J. Geophys. Res. 78, 8665–8686.
BeldersonR. H., JonesE. J. W., GoriniM. A., and KenyonN. H., 1984, A Long-Range Side-Scan Sonar (GLORIA) Survey of the Romanche Active Transform in the Equatorial Atlantic, Mar. Geol. 56, 65–78.
CacchioneD. A., DrakeD. E., ClarkeS. H., MassonD. G., 1985, Sonograph Mosaic of Northern California and Southern Oregon Exclusive Economic Zone, Amer. Assoc. Petroleum Geol. Bull. 69, 242.
CarlsonR. L. and StoddardP. R., 1981, Deformation of the Gorda Plate: A Kinematic View, EOS, Trans. Amer. Geophys. Union 62, 1035.
EatonJ. P., 1981, Detailed study of the November 8, 1980, Eureka, California Earthquake and its Aftershocks, OES, Trans. Amer. Geophys. Union 62, 959.
EEZ-SCAN 84 SCIENTIFIC STAFF 1985. GLORIA II Sonograph Mosaic of the Western U.S. Exclusive Economic Zone. EOS, Trans. Amer. Geophys. Union 66, 553–555.
EEZ-SCAN 84 SCIENTIFIC STAFF 1986, Atlas of the Exclusive Economic Zone, Western Conterminious United States, U.S. Geological Survey Misc. Investigations Series I-1792, 152 pp.
HeyR. N., 1977, A New Class of ‘Pseudofaults’ and their Bearing on Plate Tectonics: a Propagating Rift Model, Earth Planet. Sci. Letters 37, 321–325.
JachensR. C. and GriscomA., 1983, Three-Dimensional Geometry of the Gorda Plate beneath Northern California, J. Geophys. Res. 88, 9375–9392.
NessG., LeviS., and CouchR., 1980, Marine Magnetic Anomaly Timescales for the Cenozoic and Late Cretaceous: a Precis, Critique and Synthesis, Rev. Geophys. and Space Phys. 18, 753–770.
ParsonL. M. and SearleR. C., 1986, Strike-Slip Fault Styles in Slow-Slipping Oceanic Transform Faults-Evidence from GLO-RIA Surveys of Atlantis and Romanche Fracture Zones, J. Geol. Soc. London 143, 757–761.
RaffA. D. and MasonR. G., 1961, Magnetic Survey off the West Coast of North America, 40° N Latitude to 52° N Latitude, Geol. Soc. America Bull. 72, 1267–1270.
RiddihoughR. P., 1980, Gorda Plate Motions from Magnetic Anomaly Analysis, Earth Planet. Science Letters 51, 163–170.
RiddihoughR. P., BeckM. E., ChaseR. L., DavisE. E., HyndmanR. D., JohnsonS. H., and RogersG. C., 1983, Geodynamics of the Juan de Fuca Plate, pp. 5–21, in R. CabreS.J. (ed.) Geodynamics of the Eastern Pacific Region, Caribbean and Scotia Arcs, Geodynamics Series, Vol. 9, American Geophys. Union, Washington D.C. and Geological Society of America, Boulder, Colorado.
SearleR. C., 1979, Side-Scan Sonar Studies of North Atlantic Fracture Zones, J. Geol. Soc. London 136, 283–292.
SearleR. C., 1981, The Active Part of Charlie-Gibbs Fracture Zone: A Study Using Sonar and Other Geophysical Techniques, J. Geophys. Res. 86, 243–262.
SearleR. C., 1983, Multiple Closely Spaced Transform Faults in Fast-Slipping Fracture Zones, Geology 11, 607–610.
SearleR. C. and LaughtonA. S., 1977, Sonar Studies of the Mid-Atlantic Ridge and Kurchatov Fracture Zone, J. Geophys. Res. 82, 5313–5328.
SilverE. A., 1969, Late Cenozoic Underthrusting of the Continental Margin off Northernmost California, Science 166, 1265–1266.
SilverE. A., 1971, Tectonics of the Mendocino Triple Junction, Geol. Soc. America Bull. 82, 2965–2978.
Smith, S. W. and Knapp, J. S., 1980, The Northern Termination of the San Andreas Fault, California Division of Mines and Geology. Special Report 140, 153–164.
SomersM. L. and SearleR. C., 1984, GLORIA Sounds out the Seabed, New Scientist 104, 12–15.
SomersM. L., CarsonR. M., RevieJ. A., EdgeR. H., BarrowB. J., and AndrewsA. G., 1978, GLORIA II—An Improved Long Range Sidescan Sonar, 16–24 in Oceanology International 78, Technical Session J. BPS. Exhibitions, London.
StoddardP. R., 1987, A Kinematic Model for the Evolution of the Gorda Plate, J. Geophys. Res. 92, 11524–11532.
WilsonD. S., 1986, A Kinematic Model for the Gorda Deformation Zone as a Diffuse Southern Boundary of the Juan de Fuca Plate, J. Geophys. Res. 91, 10259–10269.
WilsonD. S., HeyR. N., and NishimuraC., 1984, Propagation as a Mechanism of Reorientation of the Juan de Fuca Ridge, J. Geophys. Res. 89, 9215–9226.
Wilson, D. S., Constraints on the Deformation of the So-Called Gorda Plate, J. Geophys. Res. (in press).
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Masson, D.G., Cacchione, D.A. & Drake, D.E. Tectonic evolution of Gorda Ridge inferred from sidescan sonar images. Mar Geophys Res 10, 191–204 (1988). https://doi.org/10.1007/BF00310064
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DOI: https://doi.org/10.1007/BF00310064