We characterize oxygen isotope zoning within single titanite crystals from the Carthage-Colton mylonite zone (CCMZ), Adirondack Mountains (New York State, United States), by ion microprobe. Smooth gradients of δ18O, up to 0.6‰ over 90 μm, resulted from diffusive exchange of oxygen during cooling from peak metamorphic temperatures of 650–700 °C. Modeling of the observed profile indicates punctuated cooling rates of 30–60 °C/m.y. along the CCMZ, set within long periods of much slower cooling. These results indicate a previously unrecognized period of rapid cooling along the CCMZ that is interpreted to result from the post-Ottawan collapse of the Grenville mountain belt and exhumation of the central Adirondack Highlands at ca. 1050 Ma.