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Abstract:
EVOLUTION OF THE PACIFIC OCEAN KARSTS - Karst phenomena constitute one of the main characteristics of the "high carbonate islands" of the Pacific Ocean. They are the key to the under-standing of the geological evolution, the stratigraphy, from Lower Miocene to Pleistocene and mid-Holocene, the diagenesis, mainly dolomitization and the current economic interest based on bauxite and phosphate. The eustatic variations have been numerous over the past 25 million years and can be added or substracted from the emersion and submersion movements of the plate supporting these carbonate platforms. Each island therefore has its own complex geological background with dolomitization, calcrete, bauxitic soils, fossil marine notches and karst surface either submerged or filled with phosphate, which can be mined for profit. Thanks to a thorough study of these platforms, it has been possible to establish an evolution of karst genesis in accordance with the evolution of the Pacific lithosphere and also to draw up a new model of phosphate genesis linked to phosphato-bauxitic soils and meromictic anoxic lakes.