DETRITAL ZIRCON REFERENCE FOR CAMBRIAN TO TRIASSIC MIOGEOCLINAL STRATA OF WESTERN NORTH-AMERICA

U-Pb analyses of 656 single zircon grains from Cambrian to Triassic mi ogeoclinal strata provide a latitudinal and temporal reference for the ages of grains that accumulated along the western margin of North Ame rica, Comparisons between this detrital zircon reference and the ages of grains in potentially displaced terranes outboard (west) of the mio geocline should help establish when the terranes first arrived in sedi mentary proximity to western North America, North-south variations in the ages of grains in Cambrian and Devonian to Triassic strata, which reflect the north-south changes in the age of cratonal rocks near the margin, should also help place constraints on a terrane's paleolatitud e during these time periods, The technique cannot be used to determine paleolatitude during Ordovician time, however, because miogeoclinal s trata from northern Canada to northern Mexico are dominated by grains shed from the Peace River arch (northwestern Canada).