13. Motivation
• Overriding plate can flex and form foredeep.
• WIB is a textbook flexural basin until it widens
excessively.
• Flat Farallon “sucked” down a wide section of
overriding plate (WIB).
14. Questions
• Does WIB widening coincide with a change in the pattern of
volcanism?
• Does the crustal material beneath the basins have an effect
on the depth/width of the WIB?
• Did the point of maximum subsidence stay constant or
move with the Farallon plate over time?
1. Was the flat Farallon slab beneath the WIB during its
widening?
2. Was a particular oceanic plateau beneath Wyoming when
the WIB widened?
Model sub-WIB slab fragments forwards in time and
compare to tomography.
Model tomography backwards in time to find segment
placement in late Cretaceous
25. Campanian I Depo-center
80 m.y.a
Campanian II Depo-center
75 m.y.a
Point of Maximum Deposition
in Campanian I
Point of Maximum Deposition
in Campanian I
Forwards
modeling
29. Conclusions
• The point of maximum subsidence and deposition
did not move significantly during the late
Cretaceous.
• There are slab fragments that were beneath the
basin at the right time to interact with the crust and
deepen the basin.
– The Seton et al. 2012 model is a better fit to the basins in
the isopach
– A Flat Slab window sized slab seems to be a better spatial
match to the isopachs
• Flat-slab fragments would have been effective at
hydrating/metasomatizing the Wyoming lithosphere
from below.
30. Further Work Needed (From others)
• Recreate the regional isopachs using all available
data
– The last were completed 20 years ago
• 3-D crustal flexural modeling
– Some 2-D modeling has been completed but 3-D with
crustal properties from different provinces could be
useful
• Plotting the reconstructed slab locations on a
palinspastic reconstruction of North America
– Would change the locations shown earlier. How much
is unclear.
31. References for workshop
• Bedle, PhD thesis
• Carlson 2014
• P. V. Doubrovine, B. Steinberger, and T. H. Torsvik. Absolute plate motions in a reference
frame defined by moving hot spots in the Pacific, Atlantic, and Indian oceans. Journal of
Geophysical Research: Solid Earth, 117(B9), 2012.
• R. Dietmar Müller, J.-Y. Royer, and L. A. Lawver. Revised plate motions relative to the hotspots
from combined atlantic and indian ocean hotspot tracks. Geology, 21:275, 1993.
• Hoffmann 1988
• Kirschbaum and Rogers
• Porter et al.
• M. Seton, R. Müller, S. Zahirovic, C. Gaina, T. Torsvik, G. Shephard, A. Talsma, M. Gurnis, M.
Turner, S. Maus, et al. Global continental and ocean basin reconstructions since 200Ma.
Earth-Science Reviews, 113(3):212–270, 2012.
• VdLee and Nolet JGR 1997
• Gypsum
• Sigloch? (Shatsky Rise?)
Editor's Notes
Craton = lithosphere with long-term stability
Green circles: volcanism within the time period
Blue dashed line: Sevier front (line of zero sedimentation)
