Discussion on Mesozoic cover over northern England: interpretation of apatite fission track data

Abstract

A. A. McCulloch writes: In a recent Special paper, Holliday (1993) attempted to 'reconcile AFTA-derived palaeo-temperatures with observed geological information and the probable Mesozoic burial history of N and E England'. The thermal history interpretation of the apatite fission track data from northern England (Green 1986; Lewis et al. 1992), on which the analysis by Holliday (1993) relies, is based principally on those samples which were totally annealed prior to cooling. The thermal history interpretation of these samples is then extended to understand the remaining results in terms of a common thermal history involving cooling at 65 ± 5 Ma. The primary purpose of this comment is to highlight to readers unfamiliar with apatite fission track analysis, the shortcomings in this interpretation of the fission track data and to stress the absence of an express link, implicit in the analysis of Holliday (1993), between a rigorous thermal history interpretation of the fission track data and Early Tertiary uplift and erosion. An alternative geological interpretation of the thermal history of northern England, described in more detail in McCulloch (1993), is briefly outlined. Thermal history interpretation of N England fission track data. In samples which give mean track lengths between 14 and 15.5 pm and standard deviations around 1 pm, the apatite fission track age may be interpreted as indicating a distinct cooling event from palaeotemperatures greater than 110 ºC to less than 50 ºC (Gleadow et al. 1986). Using this standard criterion, the data reported by Lewis et al. 1992 and