When the water from the Cuisance river emerges from the limestone rocks at the bottom of the Arbois blind valley, it abruptly loses the carbon dioxide it has taken on while circulating in the groundwater. It then forms by precipitation a sedimentary rock called tuff or travertine which gives rise to all forms of concretions, like the Tufs waterfall of Planches-près-Arbois. These sediments generally trap plant debris, the imprint of which is preserved in the rock.