SEISMIC EVIDENCE OF ASTHENOSPHERE UPWELLING DRIVING THE UPLIFT OF THE ADIRONDACK MOUNTAINS

The origin of intracratonic uplifts, such as the Adirondack Mountains in the northeastern United States, has been mysterious. Based on thermal geochronological studies, doming of the Adirondack Mountains has been attributed to heating induced by the Great Meteor hotspot in the early Cretaceous. However, subsurface structural constraints on this hotspot-driven mechanism and its connection with mantle dynamics, which are critical for our understanding of the origin of the Adirondack Mountains as well as intraplate uplifts in general, are limited. Here we present a 3-D shear velocity model from full-wave seismic tomography, which reveals a distinct low-velocity column in the mantle lithosphere directly beneath the Adirondack Mountains. This feature is connected, at greater depths, with the previously observed large-scale low-velocity anomaly beneath most of the northern Appalachian Province. These two anomalies may reflect the asthenosphere upwelling triggered by edge-driven convections together with the Great Meteor hotspot. Based on isostatic modeling we conclude that the buoyancy from the asthenosphere upwelling beneath the Adirondack Mountains provides the primary force driving the uplift of the Adirondack Mountains. Our findings imply that mantle dynamics, such as asthenosphere upwelling, plays a significant role in uplifting cratonic interiors.