GSA Penrose 2023

Conference Goals and Themes

An increasing number of robust datasets support that the western North America margin has dominantly been an oblique to transform plate boundary since the mid Cretaceous. Interpretation of magnetic seafloor anomalies with respect to deformation within North America indicate that the North American margin has clearly been obliquely divergent since ~35 Ma (Atwater, 1970).  

Abundant data also supports that the margin was oblique pre-35 Ma. These data include: 

• Paleomagnetic data from the Canadian Cordillera has suggested approximately 1000+ km of northward motion of the Intermontane terrane and approximately 3000+ km of northward motion of the Insular terrane (e.g., Beck and Noson, 1972; Wynne et al., 1995; Irving et al., 1996; Enkin et al., 2006a,b) since ~100 Ma, which place these terranes offshore of the western part of the US and north–central Mexico (Tikoff et al., 2023).
• The orientation of extension and ductile flow in parts of the Coast Mountains batholith and Paleogene metamorphic core complexes is oblique to the plate margin, implying a component of oblique motion (e.g., Andronicos et al., 2003; Vogl et al., 2012).
• Large strike-slip faults/shear zones (e.g., Jayko and Blake, 1993; Tikoff and St Blanquat, 1997; Giorgis et al., 2008; Krueger and Yoshinobu, 2018), regions of clockwise rotation (e.g., Beck and Noson, 1972; Beck, 1986), and development of basins (e.g., Wynne et al., 1995; Garver and Davidson, 2015; Surpless and Gulliver, 2018) occurred throughout the ca. 100–35 Ma evolution of the Cordillera.
• New isotopic data support models of coast-parallel translation along the western North America paleomargin. (e.g., Matzel et al., 2004; Garver and Davidson, 2015; Matthews et al., 2017; Sauer et al., 2019).
• Comprehensive global and regional plate tectonic models published in the last ten years provide an updated understanding, including a world-wide plate organization (e.g., Doubrovine et al., 2012; Matthews et al., 2012; Müller et al., 2019; Vaes et al., 2019).
• New reconstructions for the Pacific basin and North American continent, developed based on seismic tomotectonic analysis of subducted plates (Sigloch and Mihalynuk, 2013, 2017; Clennett et al., 2020; Fuston and Wu, 2020), are consistent with significant translation along the western North American paleomargin.

We contend that the past research efforts of the tectonics community and what is published from these efforts does not consistently reflect the reality of pre-35 Ma oblique convergent and oblique divergent motion. The premise of this Penrose Conference emerges from these major points. 

• Oblique plate boundaries are significantly understudied compared to orthogonal convergent and divergent boundaries, yet a large portion of active plate boundaries have a significant oblique component (e.g., the Alpine Fault of New Zealand; Lamb et al., 2016).
• The tectonic development of the North America Cordillera is inherently three dimensional, which requires incorporation of processes that cannot be viewed solely on either maps or cross-sections.
• There is a major issue linking tectonism and magmatism on the plate margin to that of the interior. These issues occur along all segments of the North American Cordillera, which themselves are hard to correlate with each other. Bringing together people with different perspectives working on the plate margin and in the interior to discuss these topics is required.
• The likelihood of large horizontal translations requires that terranes that caused tectonism in one area have subsequently moved from that area. Hence, workers from all sections of the North American Cordillera need to coordinate their efforts to better constrain the paleogeography through time. This approach is required for testing for significant terrane translation (e.g., Mojave–BC hypothesis; Krijgsman and Tauxe, 2006; Sauer et al., 2019).

This Penrose conference will bring together a diverse group of researchers working throughout the Cordillera, from the Late Jurassic to the Eocene, to develop a new understanding about the tectonic evolution of western North America. Conversations about oblique plate boundaries will be facilitated by a combination of field trips within Idaho, keynote presentations, and focused discussion sessions after the presentations. Only through collaborative discussions and research will the Tectonics discipline develop a coherent model for the western North American margin and move forward as a community.  

References: 

• Atwater, T., 1970, Implications of plate tectonics for the Cenozoic tectonic evolution of western North America: Geological Society of America Bulletin, v. 81, p. 3513–3536, https://doi.org/10.1130/0016-7606(1970)81[3513:IOPTFT]2.0.CO;2.
• Andronicos, C.L., Chardon, D.H., Hollister, L.S., Gehrels, G.E., and Woodsworth, G.J., 2003, Strain partitioning in an obliquely convergent orogen, plutonism, and synorogenic collapse; Coast Mountains Batholith, British Columbia, Canada: Tectonics, v. 22, no. 2, p. 24, doi: doi:10.1029/2001TC001312.
• Beck, M.E., Jr., 1986, Model for late Mesozoic–early Tertiary tectonics of coastal California and western Mexico and speculations on the origin of the San Andreas fault: Tectonics, v. 5, p. 49–64, https://doi.org/10.1029/TC005i001p00049.
• Beck, M.E., Jr., and Noson, L., 1972, Anomalous palaeolatitudes in Cretaceous granitic rocks: Nature–Physical Science (London), v. 235, p. 11–13, https://doi.org/10.1038/physci235011a0.
• Clennett, E.J., Sigloch, K., Mihalynuk, M.G., Seton, M., Henderson, M.A., Hosseini, K., Mohammadzaheri, A., Johnston, S.T., and Müller, R.D., 2020, A quantitative tomotectonic plate reconstruction of western North America and the eastern Pacific Basin: Geochemistry, Geophysics, Geosystems, v. 21, e2020GC009117, https://doi.org/10.1029/2020GC009117.
• Doubrovine, P.V., and Tarduno, J.A., 2008, A revised kinematic model for the relative motion between Pacific oceanic plates and North America since the Late Cretaceous: Journal of Geophysical Research, v. 113, B12101, https://doi.org/10.1029/2008JB005585.
• Enkin, R.J., Johnston, S.T., Larson, K.P., and Baker, J., 2006a, Paleomagnetism of the 70 Ma Carmacks Group at Solitary Mountain, Yukon, confirms and extends controversial results; further evidence for the Baja British Columbia model: Special Paper - Geological Association of Canada, v. 46, p. 221-232.
• Enkin, R.J., Mahoney, J.B., and Baker, J., 2006b, Paleomagnetic signature of the Silverquick/Powell Creek succession, south-central British Columbia; reaffirmation of Late Cretaceous large-scale terrane translation: Special Paper - Geological Association of Canada, v. 46, p. 201-218.
• Fuston, S. and Wu, J., 2020, Raising the Resurrection Plate from an unfolded-slab plate tectonic reconstruction of northwestern North America since early Cenozoic time, Geological Society of America Bulletin, v. 133, no. 5-6, p. 1128-1140, https://doi.org/10.1130/B35677.1.
• Garver, J.I., and Davidson, C.M., 2015, Southwestern Laurentian zircons in Upper Cretaceous flysch of the Chugach–Prince William terrane in Alaska: American Journal of Science, v. 315, p. 537–556, https://doi.org/10.2475/06.2015.02.
• Giorgis, S., McClelland, W., Fayon, A., Singer, B., and Tikoff, B., 2008, Timing of deformation and exhumation in the western Idaho shear zone, McCall, Idaho: Geological Society of America Bulletin, v. 120, p. 1119–1133, https://doi.org/10.1130/B26291.1
• Irving, E., Wynne, P.J., Thorkelson, D.J., and Schiarizza, P., 1996, Large (1000 to 4000 km) northward movements of tectonic domains in the northern Cordillera, 83 to 45 Ma: Journal of Geophysical Research–Solid Earth, v. 101, p. 17,901–17,916, https://doi.org/10.1029/96JB01181
• Jayko, A.S., and Blake, M.C., Jr., 1993, Northward displacements of forearc slivers in the Coast Range of California and southwest Oregon during the late Mesozoic and the early Cenozoic, in Dunne, G., and McDougall, K., eds., Mesozoic Paleogeography of the Western United States–II: Pacific Section, Society of Economic Paleontologists and Mineralogists (SEPM), Book 71, p. 19–36.
• Krijgsman, W., and Tauxe, L., 2006, E/I corrected paleolatitudes for the sedimentary rocks of the Baja British Columbia hypothesis: Earth and Planetary Science Letters, v. 242, p. 205–216, https://doi.org/10.1016/j.epsl.2005.11.052.
• Krueger, R.J., and Yoshinobu, A.S., 2018, Structures in the Jackass Lakes pluton–host-rock system, central Sierra Nevada, California, and inferred mid-Cretaceous Farallon–North America plate kinematics: Geological Society of America Bulletin, v. 130, p. 1940–1958, https://doi.org /10.1130/B31992.1.
• Lamb, S.H., Mortimer, N., Smith, E., and Turner, G., 2016, Focusing of relative plate motion at a continental transform fault; Cenozoic dextral displacement >700 km on New Zealand's Alpine Fault, reversing >225 km of late Cretaceous sinistral motion: Geochemistry, Geophysics, Geosystems - G3, v. 17, no. 3, p. 1197-1213, https://doi.org/10.1002/2015GC006225.
• Matthews, K.J., Seton, M., and Müller, R.D., 2012, A global-scale plate reorganization event at 105–100 Ma: Earth and Planetary Science Letters, v. 355–356, p. 283–298, https://doi.org/10.1016/j.epsl.2012.08.023.
• Matthews, W.A., Guest, B., Coutts, D., Bain, H., and Hubbard, S., 2017, Detrital zircons from the Nanaimo Basin, Vancouver Island, British Columbia: An independent test of Late Cretaceous to Cenozoic northward translation: Tectonics, v. 36, p. 854–876, https://doi.org/10.1002/2017TC004531.
• Matzel, J.E.P., Bowring, S.A., and Miller, R.B., 2004, Protolith age of the Swakane Gneiss, north Cascades, Washington; evidence of rapid underthrusting of sediments beneath an arc: Tectonics, v. 23, no. 6, p. 18, https://doi.org/10.1029/2003TC001577.
• Müller, R.D., Zahirovic, S., Williams, S.E., Cannon, J., Seton, M., Bower, D.J., Tetley, M.G., Heine, C., Le Breton, E., Liu, S., Russell, S.H.J., Yang, T., Leonard, J., and Gurnis, M., 2019, A global plate model including lithospheric deformation along major rifts and orogens since the Triassic: Tectonics, v. 38, p. 1884–1907, https://doi.org/10.1029/2018TC005462.
• Sauer, K.B., Gordon, S.M., Miller, R.B., Jacobson, C.E., Grove, M., Vervoort, J.D., and Fisher, C.M., 2019, Deep-crustal metasedimentary rocks support Late Cretaceous “Mojave-BC” translation: Geology, v. 47, p. 99–102, https://doi.org/10.1130/G45554.1.
• Sigloch, K., and Mihalynuk, M.G., 2013, Intra-oceanic subduction shaped the assembly of Cordilleran North America: Nature, v. 496, p. 50–56, https:// doi.org/10.1038/nature12019.
• Sigloch, K., and Mihalynuk, M.G., 2017, Mantle and geological evidence for a Late Jurassic−Cretaceous suture spanning North America: Geological Society of America Bulletin, v. 129, p. 1489–1520, https://doi .org/10.1130/B31529.1.
• Surpless, K.D. and Gulliver, K.D.H., 2018, Provenance analysis of the Ochoco Basin, central Oregon; a window into the Late Cretaceous paleogeography of the northern U.S. Cordillera: Special Paper - Geological Society of America, v. 540, p. 235-266, https://doi.org/10.1130/2018.2540(11).
• Tikoff, B., and De Saint Blanquat, M., 1997, Transpressional shearing and strikeslip partitioning in the Late Cretaceous Sierra Nevada magmatic arc, California: Tectonics, v. 16, p. 442–459, https://doi.org/10.1029/97TC00720.
• Tikoff, B., Housen, B.A., Maxson, J.A., Nelson, E.M., Trevino, S., and Shipley, T.F., 2023, Hit-and-run model for Cretaceous–Paleogene tectonism along the western margin of Laurentia, in Whitmeyer, S.J., Williams, M.L., Kellett, D.A., and Tikoff, B., eds., Laurentia: Turning Points in the Evolution of a Continent: Geological Society of America Memoir 220, https://doi.org/10.1130/2022.1220(32).
• Vogl, J.J., Foster, D.A., Fanning, C.M., Kent, K.A., Rodgers, D.W., and Diedesch, T., 2012, Timing of extension in the Pioneer metamorphic core complex with implications for the spatial-temporal pattern of Cenozoic extension and exhumation in the northern U. S. Cordillera: Tectonics, v. 31, no. 1, p. Citation TC1008, https://doi.org/10.1029/2011TC002981.
• Vaes, B., van Hinsbergen, Douwe J. J., and Boschman, L.M., 2019, Reconstruction of subduction and back-arc spreading in the NW Pacific and Aleutian Basin; clues to causes of Cretaceous and Eocene plate reorganizations: Tectonics, v. 38, no. 4, p. 1367-1413, https://doi.org/10.1029/2018TC005164.
• Wynne, P.J., Irving, E., Maxson, J.A., and Kleinspehn, K.L., 1995, Paleomagnetism of the Upper Cretaceous strata of Mount Tatlow: Evidence for 3000 km of northward displacement of the eastern Coast belt, British Columbia: Journal of Geophysical Research, v. 100, p. 6073–6091, https://doi.org/10.1029/94JB02643.