Tidal deposits of the Lower Cambrian Random Formation, eastern Newfoundland: facies and paleoenvironments
The Avalon tectonostratigraphic zone occupies about 25% of the area of insular Newfoundland. Late Precambrian development of the Avalon terrane is distinctly different than that of other parts of the Appalachian orogen and cratonic North America. Late Precambrian volcanism and tectonic instability gave way to deposition of about 2 km of Cambrian and Lower Ordovician dominantly epiclastic sediments on a slowly subsiding, relatively stable shelf platform.The Lower Cambrian Random Formation is part of the platformal sequence and is bounded by regional disconformities over much of the Newfoundland Avalon Zone, except around Fortune Bay where it is underlain by older terrestrial and shallow-marine sediments. The Random Formation was deposited during a time of global sea-level rise, and consists of up to 250 m of shoreline, nearshore, and open-shelf deposits that record macrotidal conditions and periodic storm activity. Cross-bedded quartzarenites occur in units to about 50 m thick (one exceptional unit is 110 ...