The Beach-Water Interface

The beach-water interface on the cay that we studied had an interesting lithological composition. The beach where we started our reef transect is composed of three major components; these are lithified breccia, beachrock and sand to pebble size sediment and unlithified sediment. The breccia is volcanic in origin and is composed of subangular mafic clasts surrounded by a fine grained mafic matrix. The beachrock is dominantly lithified carbonate sand, but does contain minor amounts of eroded mafic volcanic material. The unlithified sediment is of the same composition as the beachrock except that the mafic clasts are slightly larger (pebble size rather than sand size).