OBSERVATION ON ALGAL EFFECTS ON SUBAERIAL KARST SEDIMENTATION
地表喀斯特沉积中藻类作用的观察研究

With optical microscopic and Scanning Electronic Microscopic observation on subaerial karst deposit (terrestrial freshwater carbonates) samples from NW. Sichuan, China, Yugoslavia and England, and with bibliographical review, I discussed algal effects which include calcification (encrustation, infiltration and substitution) , trapping and binding effects, assimilation and secretion on the processes of terrestrial freshwater carbonate sedimentation like tufas and travertine, algal micro-reefs and coated grains etc.Some algae were related to various freshwater carbonates as a result of my observation Based on the observation, a new proposed algal effect-Shoring effects was also presented in the paper The algal effects on subaerial karst sedimental processes have been classified. Shoring effect is a synthesis mechanism in which algae and their secreted mucus play an essential role.In the process, algae and the mucus play roles both as component of deposit and as shores to support precipited clcite. Shoring effect causes micro-porousity of carbonate deposits.In conclusion, it is very common for algae to exist in various types of freshwater terrestrial carbonate deposits. All of algal effects can be classified into three groups named as active, promoting and passive ones. Micro-morphology or micro-fabrics of subaerial karst deposits can be a kind of key for people to understand the algal effects on its formation