Siliciclastic sequences accumulated along the eastern margin of Laurentia during the late Neoproterozoic to early Paleozoic as a result of the breakup of Rodinia and formation of the Iapetus Ocean. Detrital zircon data show considerable variability in provenance of time-equivalent units that has implications for paleodrainage and paleogeography. Samples from northwest Scotland and northeast Greenland show detrital zircon U-Pb age groupings dominated by Archean and Paleoproterozoic populations consistent with derivation largely from the West Greenland segment of the North Atlantic craton. In Scotland, timeequivalent outboard sedimentary sequences show contrasting Archean and Proterozoic populations, including a substantial ca. 1.1-1.0 Ga component, indicative of derivation from the Grenville orogen to the southwest. These contrasting paleodrainage patterns, consistent with paleocurrent data, must have developed during the early phase of passive-margin thermal subsidence and may have been accentuated by remnant rift shoulders. In Newfoundland and the U.S. Appalachians, time-equivalent sedimentary sequences are located within the hinterland of the Grenville orogen and are dominated by ca. 1.1-1.0 detritus with very few preMesoproterozoic grains. The Grenville deformation front in these areas may have constituted a drainage divide that limited sediment input from the cratonic interior.