The post-orogenic evolution of the Northeast Greenland Caledonides constrained from apatite fission track analysis and inverse geodynamic modelling

Abstract

We present new apatite fission track (AFT) data from the Northeast Greenland passive margin, between 75.8 and 81°N, where elevations reach over 1000m and no signs of magmatism related to the opening of the North Atlantic exist. The AFT ages are old, ranging from just less than 200Ma up to more than 350Ma, and the length distributions are predominantly narrow unimodal, with c-axis projected mean track lengths between 13.3 and 15.0μm. The passive margin of Northeast Greenland differs from other studied passive margins in terms of AFT age trends, as we observe no correlation with elevation or characteristic trends relative to mean track length.Using these new data and inverse geodynamic modelling, we constrain the evolution in the area since the orogenic collapse of the Caledonides. Exhumation histories are inferred using a uniform stretching model, incorporating variable rates of erosion or deposition, and thermal histories are found by solving the one-dimensional transient conduction–advection heat equation. These thermal histories are used with the observed fission track data to constrain acceptable strain rate histories and exhumation paths.The results suggest that rifting has been focused mainly in the now offshore regions since ~300Ma, or in minor local areas onshore, not affecting the sampled areas significantly. The present-day high topography is therefore suggested simply to represent remnants of the original Caledonian topography, modified during early rifting and, other than the flexural isostatic response to erosional unloading, we find no need for introducing post-rift related uplift mechanisms.