tufa - hand/display specimen from the paleoshoreline of ice age Lake Lahontan

Tufa is a calcium carbonate deposit that forms around the outlet of a hot spring that emerges below the surface of a body of water. These examples were formed during the Pleistocene high-stand of Lake Lahontan, which filled a connected grouping of basins in Nevada east of Reno. It was similar to ice age Lake Bonneville in Utah, and now is greatly reduced in size. Its peak was approximately 12,700 years ago and its largest remnant is Pyramid Lake, currently around 500 feet deep. The water depth there during the Pleistocene was 900 feet, and ancient shorelines can be seen far above the current lake suface, as strand lines on the surrounding mountains.  With the climate drying at the end of the Pleistocene, endorheic lakes in the Basin and Range Province, which are lakes with no outlet to the the sea, gradually evaporated, leaving salt-flat playas in the bottoms of the basins.    This tufa was formed where springs emerged from a limestone block below Lake Lahontan's surface and near the l