PLUME/LITHOSPHERE INTERACTIONS AND THEIR GEODYNAMIC EFFECTS; POSSIBLE EXAMPLES FROM THE CRETACEOUS OF THE NORTH ATLANTIC

Numerous studies of the effects of mantle plumes on the geological development of an area have shown how they can exert considerable influence on the surrounding sedimentary record. Within the North Atlantic region, to date, only one such plume, the Tertiary Iceland Plume has been clearly observed. Interactions between it and the lithosphere have been studied for a number of years and its role in e.g. regional uplift and crustal extension/compression has been well documented. Recent work, however, suggests the possible influence of two other plumes in the development of this region during the Cretaceous.

Evidence for this comes from a number of sources including new interpretations of geophysical data, a synthesis of published constraints on depositional history and recently acquired geochemical analyses of igneous rocks. The widespread Early Cretaceous inversion of the North Atlantic margin basins that has been observed is similar to that associated with the Iceland Plume. The epicentre of this uplift appears to be in the southern Rockall-Hatton area where geophysical data suggests the presence of a large, deeply-buried igneous province of Early Cretaceous age. Although no definitive geochemical data exists, the scale of volcanism and uplift that is seen is compatible with the known activity of other mantle plumes. It is suggested that the thermal decay of this proposed plume and accompanying crustal subsidence played an important role in the development of mid-Cretaceous North Atlantic paleo-oceanography.

Anomalous Late Cretaceous uplift events and associated igneous activity are also seen further to the north, principally in the Faeroe-Shetland and Rockall basins. These events have been attributed by many authors to the early stages of incubation of the Iceland Plume. There are many problems with this current hypothesis, however, and new lines of evidence invoke the presence of another distinct plume to explain these observations.