Birch Creek, a small stream with headwaters in the White Mountains of eastern California, was studied during the spring of 1961 and the summer of 1962 to determine the environmental controls on travertine deposition. Although in an arid region and ephemeral for most of its length, Birch Creek has perennial flow which starts with ground-water discharge in a wet meadow and continues for about14 miles before disappearing into valley alluvium. In 1961, travertine occurred as isolated hummocks of calcite associated with algal colonies just downstream from the wet meadow and increased in abundance downstream with increasingly abundant plant life. In the spring of 1962, from 4 to 8 inches (10-20 cm) of streambed material, including algae and %-11/4 inches of travertine crust, was scoured away by high flow resulting from unusually heavy precipitation in February and May. Travertine is estimated to form at the maximum rate of 5-10 mm per year, as determined from deposits on plexi- glass plates. Thus, the eroded travertine may have represented 4-6 years accumulation.
Water properties varied daily, with downstream distance, and between the two periods of study. Ground water emerged super- saturated with respect to calcite and carbon dioxide. Calcite was precipitated as water flowed downstream, resulting in de- creased concentrations of solutes, chiefly free carbon dioxide, bicarbonate, and calcium ions. Dissolved oxygen concentration was inversely related to water temperature, but in 1961 when algae were abundant, percent saturation was higher during the day and lower at night than in the following year. This is interpreted to have been the result of greater photosynthesis and respiration in 1961. There were also differences in concentrations of calcium and bicarbonate ions and of free carbon dioxide between years. The magnitude of daily variations in physical and chemical properties of the stream and its surroundings increased downstream. Short-term changes in water composition were most frequent during daylight at upstream stations.
Separate identification of inorganic and organic controls on travertine genesis is difficult because both factors are directly influenced by solar radiation.