Tectonic Unit: DMIA
         Name: Imperial
 
  Description: northerly derived turbiditic shale and siltstone;
               basal dark, partly bituminous shale; includes
               chert-pebble conglomerate and quartz sandstone of
               Mattson Assemblage in E. Richardson Mts; marine
 
    Formation: Foreland Belt
                  Arctic Alaska Terrane
                       uD   Imperial
 
    Age Range: Devonian - Mississippian
  Maximum Age: 408.5 Ma
  Minimum Age: 322.8 Ma