Surface exposure dating with cosmogenic nuclides fresno speed dating

Assuming that the boulder remains in a stable position, and does not roll or move after deposition, this boulder will give an excellent Exposure Age estimate for the moraine.

Rates of ice-sheet thinning We can use cosmogenic nuclide dating to work out how thick ice sheets were in the past and to reconstruct rates of thinning.

The Production Rate of cosmogenic nuclides varies spatially, but is generally assumed to have remained constant at a particular location.

In rock and other materials of similar density, most of the cosmic ray flux is absorbed within the first meter of exposed material in reactions that produce new isotopes called cosmogenic nuclides.

For a rock to be suitable for cosmogenic nuclide dating, quartz must occur in the rock in sufficient quantities and in the sufficient size fraction.

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Scientists must therefore carefully measure the horizon line all for degrees all around their boulder.

Alternatively, if the boulder has not undergone sufficient erosion to remove previously accumulated cosmogenic nuclides, it will have an older than expected age. This can be a particular problem in Antarctica, where cold-based ice may repeatedly cover a boulder, preventing the accumulation of cosmogenic nuclides, without eroding or even moving the rock.

Rocks can therefore be left in a stable position or moved slightly, without having suffiicient erosion to remove cosmogenic nuclides from a previous exposure. This is typically characterised by spread of exposure ages across a single landform.

This is crucial data for numerical ice sheet models.

As well as using cosmogenic nuclide dating to work out the past extent of ice sheets and the rate at which they shrank back, we can use it to work out ice-sheet thicknesses and rates of thinning[5, 6].

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