Alteration of the Limestone
Redistribution of calcium carbonate
Over time, Bermuda's limestone deposits have been chemically altered and lithified. The process involved are associated with the percolation of rain water through the pores of the sediment.
Microbial activity within the surface soil, related to the decay of vegetation, results in the enrichment of percolating water with carbon dioxide. The associated increase in acidity of the water causes it to dissolve limestone at the soil base and carry it downward in solution. Subsequently, at a lower level, as carbon dioxide levels decline, the calcium carbonate is precipitated within the pores of the sediment as a cement. In this way diagenesis causes a redistribution of calcium carbonate.
Chemical removal of material at the soil base results in the gradual lowering of the land surface. Although this is an inperceptively slow process, it has a significant impact over geologic time. The topography tends to become enhanced due to the more rapid lowering of valley areas, and ultimately, these chemically deepened valleys can develop into sea-level marshes and ponds.
Where calcium carbonate is being precipitated in the limestone by percolating water, the voids between the grains are filled. At the end point very little uncemented limestone remains. Passage of the water through the pores becomes restricted and the flow becomes concentrated in preferred channels within the rock.