Radiocarbon age of rock-boring Hiatella arctica (Linné) and postglacial sea-level change at Cow Head, Newfoundland

Carbonate bedrock surfaces recently exposed at Cow Head, Newfoundland (50°14′N, 57°35′W) are densely riddled with boreholes of Hiatella arctica (Linné), many of which are occupied by subfossil specimens of this bivalve as well as with vermiform burrows of a sponge (? Cliona sp.). A radiocarbon date of 8250 ± 320 years BP (GSC-3433) on several Hiatella valves from the burrows gives the age of a sea-level stand at 8 m asl at the locality, during which penecontemporaneous surf erosion or beach gravel deposition led to the demise of the shells. Other unoccupied cavities in longer exposed bedrock outcrops on Cow Head are contrasted in form and distribution with those of Hiatella and are argued to be boreholes of another marine invertebrate, not positively identified.