Comment on “Apatite fission track and (U–Th)/He data from Fennoscandia: An example of underestimation of fission track annealing in apatite” by Hendriks and Redfield [Earth Planet. Sci. Lett. 236 (443–458)

Abstract

In a recent paper Hendriks and Redfield question the existence of major episodes of burial and subsequent denudation in old cratonic settings. They use Fennoscandia as an example, a continental shield region once covered by foreland basin deposits related to the Caledonian orogen, but today characterized by an exposed Precambrian basement. Hendriks and Redfield argue against a significant Caledonian foreland basin cover, referring to a selection of the numerous thermal indicator studies that have been performed in the region. Furthermore, they discern an inconsistency between previously published fission track and (U–Th)/He results in the region, and suggest an alternative interpretation of the apatite fission-track data from Fennoscandia. Here we present geological arguments and highlight the numerous studies, only briefly mentioned or not referred to at all by Hendriks and Redfield, that strongly support the former existence of thick and extensive deposits on the Caledonian foreland. Furthermore, we discuss the alleged inconsistency between the different data sets by examining the data referred to more closely. Finally, we evaluate the significance of the suggested inverse correlation between fission track age and 238U concentration presented by Hendriks and Redfield. There is, in fact, no published example of an inconsistency between the two methods concerning Paleozoic cooling in Fennoscandia at present, and the inverse relationship stated by the authors is poorly constrained. Therefore, although radiation-enhanced lattice recovery may have an influence on the apatite fission-track age and should be examined further we conclude that the study by Hendriks and Redfield is poorly constrained, their argumentation weakly and sometimes wrongly founded, and that the thermochronology data from Fennoscandia indeed do reflect sedimentary loading.