Geometry of Proterozoic sutures in the central Rocky Mountains from seismic reflection data: Cheyenne belt and Farwell Mountain structures

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.