Natural Patterns on Rhossili Beach – Part 4

Patterns made by a thin sheet of surface water flowing over compacted beach sand, and distributing streaks of blackened particles, presumably of smaller grain size or lighter weight. Two thoughts about the origin of the black ‘sediment’, yet to be examined under the microscope, they might be organic as in comminuted mussel shell fragments, or perhaps fine sand grains coated in the products of anaerobic bacterial processes stirred up from deeper levels.