Seismic reflection data show ~40¿ S-dipping reflectors that extend from the Cheyenne belt (CB-Archean-Proterozoic suture) to 20 km depths, and profound differences in crustal reflectivity across the suture zone, which is itself imaged as an interwedging boundary. Archean crust has a Moho reflection (at 40 km) and abundant upper crustal reflectivity; Proterozoic crust has no Moho reflection and is distinctly less reflective. Reflective zones south of the Cheyenne belt include 40¿ S- and N-dipping reflections that extend from the Farwell Mountain zone to 20 km depths; these are interpreted to be a complex cryptic suture zone between the 1.78--1.76 Ga Green Mountain block and 1.75--1.72 Ga Rawah block.