Tectonic Unit: OTrAD
         Name: Duncan
 
  Description: undivided calcareous mudstone, siltstone,
               thin-bedded limestone, subordinate mafic to felsic
               volcanics, carbonate, chert, minor ultramafics;
               locally metamorphosed to slate, phyllite, schist,
               gneiss and marble; marine
 
    Formation: Insular Belt
                  Admiralty Subterrane of Alexander Terrane
                       OTA  undivided includes Devonian to Triassic rocks
                       in Duncan Canal Shear Zone
 
    Age Range: Devonian - Triassic
  Maximum Age: 408.5 Ma
  Minimum Age: 208.0 Ma