algal mat A sheet-like accumulation of blue-green algae (Cyanobacteria) developed in shallow marine subtidal to supratidal environments, as well as in lakes and swamps. The algae cover the sediment surface, and will in turn trap sediment to produce a laminated alternation of dark, organic-rich algal layers and organic-poor sediment layers. See also STROMATOLITE.

algal mat A sheet-like accumulation of cyanobacteria (‘blue-green algae’) that develops in shallow marine subtidal to supratidal environments, as well as in lakes and swamps. The algae cover the sediment surface and themselves trap sediment to produce a laminated alternation of dark, organic-rich algal layers and organic-poor sediment layers. See also stromatolite.