BIOLOGICAL INDICATORS OF HOLOCENE SEA-LEVEL AND CLIMATIC VARIATIONS ON ROCKY COASTS OF TROPICAL AND SUBTROPICAL REGIONS

Over more than twenty years research in stable regions of tropical and subtropical Atlantic as well as in tectonically active regions of the Eastern Mediterranean coast, we have made use of biological sea-level indicators (Bio sli) of past sea-levels. The latter include rock-buil ding species (vermetid gastropods, coralline algae and corals), as wel l as smaller fixed invertebrates, whose frail skeletons are preserved in case of a rapid uplift, but rarely in case of a slow elevation or s ubmersion. Reef-building Bio sli are adapted to the detection of slow relative movements (tectonic or eustatic) whereas frail species allow a reconstitution of rapid, co-seismic elevations or complex up and dow n movements. The composition of a recent fossil fauna along a tropical coast may present some differences with that of fauna presently livin g along the same shore. Such differences can sometimes be interpreted as being of climatic origin. in regions subjected to rapid climatic va riations, a periodical survey of the repartition of a number of specie s may help detecting rapid climatic variations.