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.