Clay-mineral diagenesis and apatite fission-track age data indicate that the maximum burial temperatures to which the Middle Devonian Tioga metabentonite was exposed rise abruptly from low values in western New York State to higher values in the east. The highest temperatures, which approach 175 °C, were reached just west of Syracuse. Neither the pattern nor the magnitude of burial temperatures can be explained solely by burial of lihe metabentonite beneath Upper Devonian sediments. Although spatial variations in the geothermal gradient could have produced the observed pattern of burial temperatures it is more likely that Carboniferous sediments, no longer preserved in the area, were responsible for the indicated burial. The inferred presence of thick Carboniferous sequences in western New York State suggests that the Allegheny orogeny had a stronger influence on sedimentation in the northern Appalachian Basin than has been previously recognized.