Conclusions
Investigation of lithospheric thickness beneath cratons by geophysical techniques is problematic.  Seismic low velocity zones are smaller in amplitude and more diffuse than in other settings.  P to S conversions from the base of the lithosphere are of small amplitude and arrive at a relatively noisy time during the seismogram.  S to P receiver functions are of small amplitude but arrive at a quieter time during the seismogram.  Heat flow provides some insight into the thickness of the lithosphere, but quantification of that thickness hinges upon estimates of the conductivity of the material, the heat production of the crust, and the three dimensional effects of heat refraction.  Traditional gravity measurements may not observe a lithospheric root simply because that root may represent a density anomaly compared to the convective asthenosphere.  Spectral gravity measurements demonstrate the large-scale variations in flexural rigidity but lack the resolution necessary to map heterogeneities at wavelengths less than several hundred kilometers.
   The application of these techniques to the Wyoming Craton may indicate that there has been modification or removal of at least the southernmost portion of the lithospheric root.  High seismic velocity anomalies extend to depths of >200 km throughout the craton but extend deeper still in the craton interior.  Receiver functions show conversions interpretted to be lithospheric in origin that extend deeper in the craton interior than near the Cheyenne Belt.  Higher heat flow than is observed in other cratons, particularly near the Cheyenne belt may represent a thinning of the conductive region. 
   It is clear, however, that the character of the lithosphere of the craton sharply contrasts that of the surrounding Cordillera.  Higher mantle velocities, lower heat flow, and much greater flexural rigidity all seem to characterize the region north of the Cheyenne Belt relative to that to south.  Therefore, the Wyoming Craton, though perhaps modified from its original form, retains some of the characteristics that have differentiated it from its surroundings.

Future Prospects
The integration of various geophysical techniques could prove useful in investigating the timing and extent of lithospheric modification beneath the Wyoming Craton.  The key to the utility of using the above techniques in concert is their sensitivity to varying spatial and temporal scales. 
   Changes in lithospheric composition or architecture would be imaged immediately by seismic and magnetotelluric methods.  If indeed the elastic thickness of the lithosphere reflects the depth of the 550 degree isotherm, a thermal pulse would take tens of millions of years to affect the observed flexural rigidity.  Finally, surface heat flow would require that enough time had elapsed since thermal modification that the pulse would propagate to the surface.  This timescale is roughly twice that of the flexural rigidity.
   Therefore, the synthesized investigation and coupled modeling of seismic, thermal, and flexural data would provide insight into the spatial extent and temporal history of any modification of the Wyoming Craton.