Organic Reef or Bioherm
A ridge or mound composed mostly of the skeletons of sedentary calcareous organisms.
Requires warm, shallow seawater relatively free of suspended, land-derived sediment, so that photosynthesizers and filter feeders can survive.
Characterized by high biodiversity.
Fossilized reefs occur encased in rock, usually of a different lithology.
Silurian reef complex, Gotland, Sweden. ►
Image courtesy of Hannes Grobe.