Early lithification of beach sand.  This is part of the How To…series  on carbonate rocks

One of the most recognizable products of seafloor cementation is beachrock; lithified beach sand. Modern beachrock is common on tropical coasts, those that are wave-washed and quieter shores sheltered by reefs and island barriers. It is less likely to be found bordering cooler seas. Beachrock forms in clean carbonate and siliciclastic-volcaniclastic sands. Lithification occurs so rapidly (months, years)  that one can find all sorts of interesting relics entombed – shells, fish skeletons, coconuts, the flotsam and jetsam of wars, boats that have come to grief, or the refuse strewn by centuries of ocean travelers.

Beachrock affords a domicile for algae and invertebrates that would not normally enjoy living on a soft sand beach; thus, its formation may change existing biotas. It also provides a protective carapace to a beach, reducing the impact of waves. Formation of beachrock potentially changes the beach dynamics. Continue reading →