Thermochronology, erosion surfaces and missing section in West Greenland

In central West Greenland, Palaeogene volcanic sequences deposited during post-rift subsidence are exposed in mountains reaching 2 km above sea level (a.s.l.), with Palaeocene marine deposits within this section at elevations up to 1.2 km a.s.l. This clearly shows that present-day elevated topography of the West Greenland margin is not a remnant of the rifting process but developed later. Integrating such geological constraints with landscape analysis and thermochronological data shows that mountain summits in central West Greenland represent an Oligocene-Miocene peneplain, which is the counterpart of a correlative unconformity offshore separating Eocene from Middle Miocene sedimentary units. Onshore the peneplain has been exhumed, uplifted to its present altitude and progressively dissected since the Late Miocene. Redfield (Journal of the Geological Society, London, 167, 261-271, 2010) questioned numerous aspects of this interpretation, suggesting that 'the AFT model-based hypothesis that [the elevated topography of West Greenland] was constructed in purely Neogene time remains an unproven speculation'. But as we illustrate here, evidence for Neogene uplift is provided by landscape analysis and geological evidence, as well as thermochronology, and integration of these independent lines of investigation provides a consistent synthesis that we regard as highly reliable. The resulting history of episodic burial and exhumation cannot be simply dismissed, and poses a major challenge to accepted tectonic and geomorphological models for the development of rifted continental margins: how do mountains form along passive continental margins millions of years after rifting and breakup?