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U.S. GEOLOGICAL SURVEY
Data Series 280

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Conversion Factors, Datum, Definitions, and Abbreviations and Acronyms

Conversion Factors

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows:

°F=(1.8×°C)+32.

Datum

Horizontal coordinates convention: Horizontal coordinates, given in meters, are referenced to the Universal Transverse Mercator (UTM) system of Easting (X coordinate) and Northing (Y coordinate) distances within Zone 11 and are based on the North American datum of 1927 (NAD27).

Definitions

Isotope notation conventions: Strontium isotopic compositions are given as both atomic ratios of ⁸⁷Sr/⁸⁶Sr as well as delta strontium-87 (δ⁸⁷Sr) calculated using the formula:

δ⁸⁷Sr = [(⁸⁷Sr/⁸⁶Sr_sample/⁸⁷Sr/⁸⁶Sr_msw)-1]×1000,

where ⁸⁷Sr/⁸⁶Sr_msw is the value for modern sea water (msw) of 0.70920, and the resulting value is in parts per thousand or per mil (‰). In addition, delta strontium-87 can be calculated using the value for seawater ⁸⁷Sr/⁸⁶Sr at the time of rock deposition and is designated as δ⁸⁷Sr_t.

Geochronological conventions: Abbreviations used to designate geologic time in this report are mega-annum (Ma) to specify a specific time in millions of years before the present, and millions of years (m.y.) to specify the duration of a remote time interval.

Units of concentration: Concentrations of chemical constituents measured in unknown rock samples are given in weight percent (parts per hundred, abbreviated by wt. %) for major elements in the form of oxides, and micrograms per gram (parts per million, abbreviated by µg/g) for trace elements. Concentrations of acids used to digest the carbonate fraction of rock samples are given in Molarity units equal to the number of moles of a solute per liter of solvent (abbreviated as M).

Abbreviations and Acronyms

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