Depth of deposition of Early Holocene raised sediments at Irvine deduced from algal borings in mollusc shells

Micro-borings attributed to the chlorophytes Phaeophila and Eugomontia and the cyanophytes Hyella and Plectonema are recorded from shells in the early Holocene sediments of Irvine. The basal gravel beds generally show a higher density of algal borings and a greater percentage of algal-infested shells than the overlying sand unit. Borings of Eugomontia and the sponge Cliona and the calcareous algae Melobesia and Lithothamnium, are restricted to the basal gravel. Pockets of broken Lithothamnium observed in the sand unit are interpreted as reworked. By comparison with Recent micro-endolithic algal assemblages in the Firth of Clyde, it is concluded that the basal gravel formed in a low energy marine environment about 10 m deep: the overlying sands represent a true raised beach