Oxygen isotope ratio cycle likely driven by the Lomagundi carbon isotope excursion. Oxygen isotope ratio cycle Oxygen isotope ratio cycles are cyclical variations in the ratio of the abundance of oxygen with an atomic mass of 18 to the abundance of oxygen with an atomic mass of 16 present in some substances, such as polar ice or calcite in ocean core samples, measured with the isotope fractionation. The ratio is linked to water temperature of ancient oceans, which in turn reflects ancient climates. Cycles in the ratio mirror climate changes in geologic history. Oxygen (chemical symbol O) has three naturally occurring isotopes: O, O,
Standard atomic weight "atomic" either, as it does not correspond to the property of any individual atom. The same argument could be made against "relative atomic mass" used in this sense. IUPAC publishes one formal value for each stable element, called the "standard atomic weight". Any updates are published biannually (in uneven years). The last change was published in 2015, setting a new value for ytterbium In 2017, no changes were published. The value published can have and uncertainty be an "interval" like for neon: , or can be an interval, like for boron: [10.806, 10.821]. Next to these 84 values, IUPAC also