Abstract

The production rates of terrestrial in situ cosmogenic nuclides depend on the altitude and can therefore be used to constrain paleoaltitudes if the history of cosmogenic-nuclide production in a region can be constrained. This chapter discusses the theory behind cosmogenic-nuclide paleoaltimetry, sampling strategies, and practical limitations of the technique. Three exposure scenarios may allow for the calculation of past altitudes: 1) exposure for a finite time period at a single elevation and without erosion or burial, followed by immediate shielding from further production of cosmogenic nuclides; 2) steady uplift of a surface throughout nuclide production, without erosion or burial; and 3) exposure of a sample without erosion or burial for a sufficient duration that the concentration of a cosmogenic radionuclide has reached equilibrium. To constrain paleoelevation, all exposure scenarios require independent evidence of the depth-history of a sample during exposure to cosmic rays because production rates attenuate rapidly in rock. Depth profiles and measuring multiple nuclides allow for better constraints of parameters in paleoaltitude calculations.

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