Surficial beach structures formed by wave-generated foam

In this article, we report on the modification of an intertidal beach surface by processes connected with the generation and redistribution of foam during a coastal storm. Foam generated by breaking waves initially accumulated at the swash line but was reworked across the beach by onshore winds. A distinctive suite of sedimentary structures, capable of preservation in the geological record, was produced that displayed a distinctive cross-shore arrangement from the zone of foam generation to the zone of foam deposition and also varied according to tidal level and wind speed. Foam marks with wind-transverse linear elements characterized the upper sections of the beach. Other distinctive features formed during this storm include foam swash lines, wind-parallel foam stripes, mud drapes, and sand drapes on the upper beach and supratidal zone. These features formed a surface veneer on a high-energy dissipative beach; their formation began during a high tide and continued during the subsequent falling tide. During the later stages of the falling tide, still-forming foam-driven features were in places being modified by (and themselves modifying) surface features characteristic of late-stage emergence runoff (e.g., double-crested ripples, rill marks, microdeltas).