Travertine: Yellowstone’s Hydrothermal Timekeeper | Open spaces


The travertine age-determining technique was originally used by Neil Sturchio and his USGS collaborators on old travertines from Terrace Mountain and Mammoth Hot Springs in the northern part of Yellowstone National Park. They used these ages to determine the timing of glacial advance and retreat during past ice ages at Yellowstone, finding that the travertine deposit hot springs migrated to higher elevations when glaciers occupied valleys or ceased altogether. their activity when glaciers covered the whole region.

The most well-known hydrothermal area of ​​travertine deposit in Yellowstone is Mammoth Hot Springs. There, new travertine is permanently deposited and the old travertine outcrops stretch for many miles to the north and south. Travertine is also found in small amounts at other locations in Yellowstone National Park, including Upper Geyser Basin, near Firehole Lake in the Lower Geyser Basin, at Terrace Spring near Madison Junction, and along the Upper Snake River near the southern boundary of Yellowstone National Park. .

Travertine deposited outside the Yellowstone caldera, such as at Mammoth Hot Springs, occurs in thick deposits because the subterranean geology outside the caldera includes shallow Paleozoic and Mesozoic sedimentary rocks that the Warm waters dissolve as they flow, providing the large amounts of calcium and carbonate necessary for formation of travertine. Conversely, the subsoil of the Yellowstone Caldera rests on thick rhyolite flows which are generally low in calcium, so thermal waters have much lower calcium concentrations. The existence of travertine in the Yellowstone Caldera, such as at Lower Geyser Basin, therefore requires different conditions than Mammoth Hot Springs, such as large influxes of cold meteoric water into the hydrothermal system to cool and dilute the amount of silica in the thermal caldera. waters. One potential source of this water is the melting of glaciers which, during the last ice age, covered the geyser basins of the caldera with up to a kilometer of ice until they retreated about 15 thousand years ago. Another possibility is that the travertine deposits in the geyser basin record periods of extreme precipitation that have lasted for hundreds to thousands of years and therefore can be a great indicator of past climatic conditions in Yellowstone.

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