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Travertine (carbonate; marl) benches, Havasu Canyon, Arizona
When water percolates through soils it picks up high concentrations of carbon dioxide. This, in turn, can dissolve carbonate rocks in the groundwater. Here, a large spring has emerged in Havasu Canyon, Arizona (USA), and since the water is not longer pressurized, the carbon dioxide is released into the atmosphere, allowing the dissolved calcium carbonate to precipitate to form striking marl (travertine) benches.