Abstract:

A reef is defined as a carbonate buildup mainly constructed by organisms and organic actions and stunding above the sea (or lake) floor. Organic actions contributing to reef include:(1) forming reef framework by erect,inarticulate and calcified organisms, (2) baffling sediments by erect, noncalcified or calcified organisms, (3) supplying sediments to reefs by calcified organisms except frame-formers, (4) adhering sediments by organisms such as algae which can secrete mucus,(5) strengthening reef construction through encrustment of sheet-like or filamentous organisms on frame-formers or bafflers, (6) binding non-consolidated sediments by sheet-like or filamentous organisms, (7) covering sediments by creeper organisms. On the contrary, organisms can destroy reefs by boring or eating the soft tissue or skeletons of the reef-forming organisms. According to their composition and structure, reefs are classified into:(1) frame-reefs, (2) baffle-reefs,(3) mounds (including limemud mounds).