The uplift history of the Adirondack anorthosite has been clarified by analyzing apatite using the fission-track method. Ages ranged from 86 to 147 m.y. on samples collected over an elevation difference of 11,560 m in the anorthosite massif. An uplift rate of about 0.03 mm/yr is obtained for the 61-m.y. interval from 86 to 147 m.y. ago, on the basis of the correlation between fission-track age and elevation. The calculated value for the uplift rate during the past 86 m.y. is 0.05 mm/yr. A Mesozoic “hotspot epeirogeny” is not required to explain the uplift rates based on apatite fission-track data.

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