The myth of the Highland Cretaceous revealed by the art of palaeogeographic mapping

Abstract

Since the term was coined in 1873, paleogeography has provided a powerful map-based tool for synthesising, visualising, and testing diverse regional data and hypotheses, but there are problems in deducing the palaeogeography of areas with few data points. As an example, the Scottish Highlands are better mapped and more studied than almost any other ancient orogen, yet questions remain on the persistence of topography since the Caledonian orogeny and the possibility of Cretaceous marine inundation. This paper reviews the data available on Scottish Cretaceous outcrops using published geological maps and memoirs to extract data: outcrop length, stratigraphic thickness and component units, elevation range of the outcrop, and subcrop formations. All Cretaceous rocks in western Scotland were deposited in shallow marine and shoreline environments; deposits thin northwards and appear to be close to a feather edge. Elevation data are used to construct a Cretaceous surface which intersects present-day topography at low to intermediate altitudes. It is concluded that the Scottish Highlands were largely emergent during the Late Cretaceous, confirming previous palaeogeographic studies.