Abstract of Straccia, F.J., B.H. Wilkinson, and G.R. Smith. 1990. Miocene lacustrine algal reefs--southwestern Snake River Plain Idaho. Sedimentary Geology 67:7-23.

The Hot Spring Limestone is a 5m thick shallow-water algal carbonate at the base of the Chalk Hills Formation, SW Idaho. Reefal bodies consist of hollow, closely packed algal cylinders 0.3-0.4 M high; these formed reefal columns exposed to wave action and erosion. The sedimentary matrix of the interstices accumulated fossils of hundreds of species of diatoms as well as mollusks, sponges, and fishes.