Abstract The numerous extinctions that affected shallow marine faunas on the tropical shelves surrounding Laurentia in the Cambrian and Early Ordovician have been the focus of many detailed biostratigraphic, evolutionary, and paleoecologic studies. Data from carbonate platform and off-platform strata have been used to propose process-response models that invoke sea level change as a forcing mechanism for extinctions and/or radiations within the Cambrian and Early Ordovician. Some regressive features observed near horizons of faunal change within the Cambrian-Ordovician boundary interval on various continents have been used to propose a series of "eustatic events" (Nicholl et al., 1992). These include the "Lange Ranch Eustatic Event" and "Black Mountain Eustatic Event" of Miller (1984, 1992) and the Acerocare Regressive Event and Peltocare Regressive Event of Erdtmann (1986). There is much debate about the nature of these proposed events (Ludvigsen et al. 1986; Taylor et al. 1992; Landing 1993) based, at least in part, on the ambiguous nature of the sedimentological data and insufficient precision of correlation.