MICRITIZATION AND CARBONATE-GRAIN BINDING BY ENDOLITHIC ALGAE.

Endolithic (boring) algae are the direct or indirect agents of important erosive and early diagenetic processes in carbonate sediments. Algae boring into carbonate grains produce micrite envelopes by repeated boring and infilling of borings by precipitated micrite. However, the algae also produce micrite envelopes outside grains by the calcification (cementation) of exposed dead endolithic filaments, a process which reduces intergranular porosity. Algal filaments grow through the micrite envelopes into intergranular pores, and live within the pores as chasmolithic algae (living in holes not of their own creation); after death these may become calcified to produce an intertwined mesh of calcified filaments on which later micrite and microspar cements precipiate.