Terrestrial cosmogenic nuclides, produced by secondary cosmic-ray interactions in the atmosphere and in situ within minerals in the shallow lithosphere, are widely used to date surface exposure of rocks and sediments, to estimate erosion and weathering rates, and to date sediment deposition or burial. Their use has transformed geomorphology and Quaternary geology, for the fi rst time allowing landforms to be dated and denudation rates to be measured over soil-forming time scales. The application of cosmogenic nuclides to geology began soon after the invention of accelerator mass spectrometry (AMS) in 1977 and increased dramatically with the measurement of in situ-produced nuclides in mineral grains near Earth's surface in the 1980s. The past 25 yr have witnessed the development of cosmogenic nuclides from their initial detection to their prevalence today as a standard geochronological and geochemical tool. This review covers the major developments of the past 25 yr by comparing the state of the fi eld in 1988 with that of today, and by identifying key advances in that period that moved the fi eld forward. We emphasize the most commonly used in situ-produced nuclides measured by AMS for geological applications, but we also discuss other nuclides where their applications overlap. Our review covers AMS instrumentation, cosmogenic nuclide production rates, the methods of surface exposure dating, measurement of erosion and weathering, and burial dating, and meteoric 10 Be.-In memoriam: Devendra Lal (1929Lal ( -2012, whose vision inspired the fi eld. 10 Be-Beryllium-10 produced in the atmosphere is ubiquitous on Earth's surface and is typically present at concentrations far greater than the in situ-produced variety. Its concentration in soils, sediment, and ice depends on many factors, including production rates, atmospheric circulation, and precipitation, as well as weathering and erosion.
Gas Ionization Detector
R30 Detector R45Gas filled Magnet ExB velocity selectors Figure 1. A schematic of the PRIME Laboratory accelerator mass spectrometer (AMS). Every AMS consists of at least fi ve basic parts: (1) a negative ion source, followed by (2) a mass-selective element such as a magnetic sector, (3) an accelerator with an electron stripper, (4) a second mass-selective element, and fi nally (5) a particle detector. Additional elements such as velocity selectors, electrostatic elements, and gas-fi lled magnets may be employed at individual laboratories to enhance the selectivity of the AMS, but the overall architecture remains similar. PRIME Laboratory employs two discrete detector beam lines. For scale, the accelerator tank is ~13 m long.on August 24, 2013 gsabulletin.gsapubs.org Downloaded from