Apatite fission track thermochronology: an overview of its potential and limitations in geomorphology

Abstract

The specific time window of apatite fission track thermochronology (AFTT) places it in a unique position to offer continuous time–temperature baseline histories for relatively stable shield, rift and passive margin environments, spanning several geological eras. Fission tracks anneal partially at temperatures between ≈110 °C and ≈60 °C and thereby provide information on residence times within specific levels of the crust. Most samples collected from these terrains, however, are usually found to have cooled out of the apatite partial annealing zone (APAZ) by the mid‐Cenozoic at the latest. Owing to the stability, at geological timescales, of tracks at temperatures <60 °C (i.e. within depths of 0–2.5 km at normal geothermal gradients), a significant loss of resolution must therefore be reckoned with at shallow, although geomorphologically crucial, crustal depths. Indeed, the Neogene and Quaternary are understood to have been most influential in generating the scenery of today, and a use of radiometric and stratigraphic techniques in a nested, multisystem approach can assist in bridging the resolution gap. This paper examines and illustrates, mostly with original examples, the uses and limitations of AFTT in addressing the response of Earth surface systems to event patterns in global tectonics, the controls of lithology and structure on denudation rates, the origin and evolution of passive margin escarpments, the mass‐balanced reconstruction of palaeoelief, the use of apatites as tracers for understanding provenance in sediment routing systems, and the tempo (or episodicity) of denudation as postulated by W. M. Davis’ canons of the ‘geographical cycle’. Alongside efforts towards standardizing the supply of analytically robust AFT results in the laboratory, a more standardized geoscientific interpretation of AFT data is also desirable in order to build a consistent world base of geomorphic rates which can be made available to – and used with confidence by – non‐AFTT specialists.