Terrestrial cosmogenic nuclide dating

In NGU's projects on unstable rock slopes in Norway, TCN dating is used to date 1) rock-avalanche deposits and 2) sliding surfaces.

Ages of rock avalanche deposits throughout Norway cluster in the first few thousand years after deglaciation, however ages throughout the entire Holocene have also been obtained.

Alluvial fan surfaces older than ~ 70 ka have begun to undergo sufficient erosion such that the majority of Be TCN ages for beach bars near Beatty Junction and shorelines ~ 8 km south of Furnace Creek is large, ranging from ~ 119 ka to ~ 385 ka and ~ 109 ka to ~ 465 ka, respectively.

Displacements rates measured today by differential Global Navigation Systems Satellite Systems (GPS) indicate the same velocity suggesting that the rockslide has been moving nearly constantly over the past 14 thousand years.

The basic principle is that these radionuclides are produced at a known rate, and also decay at a known rate.

Accordingly, by measuring the concentration of these cosmogenic nuclides in a rock sample, and accounting for the flux of the cosmic rays and the half-life of the nuclide, it is possible to estimate how long the sample has been exposed to cosmic rays.

This disparity between dates determined by different dating methods and the large spread of TCN ages suggests that the cobbles and boulders have considerable inherited Be concentrations, suggesting that the clasts have been derived from older shorelines or associated landforms.

These results highlight the problems associated with using surface cobbles and boulders to date Quaternary surfaces in Death Valley and emphasizes the need to combine multiple, different dating methods to accurately date landforms in similar dryland regions elsewhere in the world.

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  1. “When it was under the AOP, it was all centered on committee-based decisions,” said Julia Smith, who spearheads the alliance and will continue leading it as general manager of Symmachia. Pangaea is a group formed of The Guardian, Financial Times, CNN International and Reuters, with inventory also supplied by The Economist.