The steep path that leads to this stop develops in a low bush and at times presents banks of quartz conglomerate (fluvial-delta environment) and algal limestone (marine environment). Among the latter, there is a very characteristic one: it is only 80 cm thick and is formed by billions of fusulinid shells, one on top of the other! These are single-celled organisms with a fusiform carbonate shell that can reach over 1 cm; they were extinct at the end of the Permian. Another peculiarity of this fusulinid bank is that all the shells are silicified: the silica has chemically replaced most of the calcium carbonate of which they were originally made. It is believed that to form such particular calcareous bank the fusulines either were exterminated by a very violent storm, or by temporary lack of oxygen in the water, perhaps connected to an abnormal and pervasive algal proliferation.

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A huge”water spill” from the sandy Carboniferous marine sediments