Abstract

The Adirondack Mountains in northern New York State form an elongate, domal exposure of mainly high-grade metamorphic tectonites in a mountainous setting with topographic relief of ∼1 km. The origin of the Adirondack Mountains and this relief has long been enigmatic, since the Adirondacks presently lie within an intracratonic setting, inboard of the North American passive margin and far from any active plate boundaries. Through the application of apatite fission-track (AFT) thermochronology and apatite (U-Th)/He (AHe) dating within the eastern Adirondack Mountains, this study provides constraints on both the thermal and erosional effects of Mesozoic passage near a hotspot and the timing of relief development.

AFT thermochronology and AHe dating record relatively stable thermal conditions within the eastern Adirondacks from the Middle Jurassic into the Early Cretaceous. During the Early Cretaceous (ca. 130–120 Ma), the region underwent heating associated with progressive movement near the Great Meteor hotspot, resulting in the temporary establishment of an elevated geothermal gradient. Following regional heating, cooling rates increased considerably (ca. 105–95 Ma), likely due to both thermal doming, producing an increase in erosion rate, and the relaxation of isotherms after passage near the hotspot.

The regional distribution of AFT ages across the eastern Adirondacks reveals no systematic age gradient from core to periphery, which would be expected under conditions of persistent high relief during the decay of a crustal root over many tens to hundreds of millions of years. Instead, thermochronological data suggest that the present relief developed during the Late Cretaceous–Cenozoic through plateau dissection during periodic base-level changes.

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