How Old are Fens?
In the Rocky Mountains, David Cooper indicates that peat accumulates very slowly, from 11 to 41 centimeters per thousand years. Inglenook Fen on the northern California coast is probably only 3,000 to 4,000 years old.
Bartolome et al., in 1990 studied six fens at Sagehen Creek on the Tahoe National Forest. According to their study based upon using radiocarbon methods revealed that the fens were of recent origin, originating at different times between 8,700 and 810 years before present. This places their origin in the Holocene. The variation in fen ages at Sagehen Creek indicates that their origin is probably due to recurring natural phenomena affecting the water supply. They conclude that these fens at this location are stable features, and not fragile vestiges of ancient glacial events.
According to Bartolome et al., in 1990, determined the age of Kiln Fen to be about 2,150 years old before the present. Bartolome did not age the other fens in Sagehen Creek, some of them displayed in the photos below.
Kiln Fen, Sagehen Creek, Tahoe National Forest. Photo by Carl Wishner.
Kiln Fen, Sagehen Creek, Tahoe National Forest. Photo by Carl Wishner.
Kiln Fen, Sagehen Creek, Tahoe National Forest. Photo by Carl Wishner.
Kiln Fen, Sagehen Creek, Tahoe National Forest. Photo by Carl Wishner.
Fen in mid elevations in Sagehen Basin, habitat for Botrychium and Meesia, Tahoe National Forest. Photo by Susan Urie.
Fen at mid elevations, Sagehen Basin, habitat for Meesia uliginosa, Tahoe National Forest. Photo by Susan Urie.
Fen in Upper Sagehen Basin, Tahoe National Forest. Photo by Susan Urie.
Fen in Upper Sagehen Basin, Tahoe National Forest. Photo by Susan Urie.
Accumulating the 20 to 40 centimeters of peat to be classified as a fen indicates a very long period of hydrologic and geomorphic stability. The exact ages of fens throughout California remains open for further study.