Cauldron subsidence at Ascutney Mountain, Vermont

Summary results of the Glens Falls CUSMAP project, New York, Vermont, and New Hampshire

“…However, unlike the gravity field anomaly, the western magnetic anomaly has much greater amplitude. The intense aeromagnetic anomaly associated with the gabbro-diorite has gradient maxima that closely conform to the contacts as mapped by Chapman and Chapman (1940), except in the southeastern quadrant. Whereas the surface outline of the pluton is gourdlike and has an eastward-projecting neck, the magnetic data suggest that the subsurface outline is more rectangular.…”

“…Geologic observations from both studies indicate that the outer walls of the syenite and granite bodies are nearly vertical at the surface. Contacts of the gabbro-diorite are not well exposed (Chapman and Chapman, 1940). On the complete Bouguer gravity anomaly map ( fig.…”

“…2) consists of (1) Figure 2. Geologic map of the Mount Ascutney, Vt., area (from Chapman, 1940, andothers, 1961). Profile A-A' modeled in figure 4.…”

“…that is cut by smaller syenite plugs at Pierson Peak and Little Ascutney Mountain and (2) an eastern oval body of syenite at Mount Ascutney that is cut by a circular plug of biotite granite (Daly, 1903;Chapman and Chapman, 1940). Geologic observations from both studies indicate that the outer walls of the syenite and granite bodies are nearly vertical at the surface.…”

“…Radiometric dates of 96.4 and 100±2 Ma (Armstrong and Stump, 1971) for the complex at Cuttingsville and 122.2± 1.2 Ma (Foland and others, 1985) for the complex at Mount Ascutney have been obtained. At Mount Ascutney the intrusive center apparently migrated about 6 km through time from west to east and changed in composition from gabbro and diorite to syenite to granite (Daly, 1903;Chapman and Chapman, 1940). The intrusive center at Cuttingsville, however, remained relatively fixed in location through several intrusive events.…”