Calcareous

Decreases in carbonate ions can make building and maintaining shells and other calcium carbonate structures difficult for calcifying organisms such as oysters, clams, sea urchins, shallow water corals, deep sea corals, and calcareous plankton.

The traveller from the coast, who, after plodding northward for a score of miles over calcareous downs and corn-lands, suddenly reaches the verge of one of these escarpments[.]

Cellariiform, the orifices nearly confined to the convex frontal and lateral surfaces; the basal surface with a strong median calcareous keel, almost concealed by a flat membranous epitheca, which covers the whole zoarium […]

Instead, the spoil will be used in part to create 127 hectares of new calcareous grassland (alkaline grassland), woodland, wood pasture, and wetland habitats.