Lithification of peritidal carbonates by continental brines at Fisherman Bay, South Australia, to form a megapolygon/spelean limestone association.

Abstract

Saline springs emerge at Fisherman Bay through an extensive supratidal flat and cement the carbonate sand to form a lithified crust as the water evaporates. The crust forms in concentric bands around each point of emergence, and consists of large and small polygons which, as they grow, impinge on each other to form small tepee structures. The cementing mineral is aragonite, with a little gypsum in places. The crust is <3000 yr old and is still forming. It contains small caverns, which in turn contain pisolites and other structures similar to those found in limestone caverns inland. The water has acquired its load of dissolved salts from the adjacent semi-arid coastal plain. It is saturated for aragonite, and is high in calcium, bicarbonate, sulphate and chloride. -H.R.B. Show more