Thermochronology, denudation and variations in palaeosurface temperature: a case study from the North Slope foreland basin, Alaska

Abstract

Integration of vitrinite reflectance (Ro) and apatite fission track (AFT) data from well sequences can provide a direct estimate of the geothermal gradient at the time of maximum palaeotemperatures and the time at which sequences began to cool from maximum palaeotemperatures. These values, plus an understanding of the effects of cooling in response to long‐term climatic changes, are particularly important when estimating the amount of denudation experienced by the sequences during cooling from maximum palaeotemperatures. In this case study, AFT data have been generated for subsurface samples from eight wells drilled within the North Slope foreland basin of northern Alaska in an effort to study the thermal history of the basin. The combination of Ro and AFT data establish that maximum palaeotemperatures were attained within the North Slope foreland basin prior to cooling beginning in the Palaeocene. Furthermore, they indicate that palaeogeothermal gradients when cooling began were close to the present‐day values, and that Cenozoic surface cooling resulted in a significant amount of ‘apparent’ denudation. These results suggest that heating throughout the basin was largely due to deeper burial, and that cooling was due to both removal of section by denudation and a drop in the mean annual surface temperature.