Regional Intraplate Exhumation Episodes Related to Plate Boundary Deformation

Simon P. Holford¹, Paul F. Green², Ian Duddy², Jonathan Turner³, and Richard Hillis^1
1Australian School of Petroleum, University of Adelaide, Adelaide, SA, Australia
²Geotrack International Pty Ltd, Melbourne, VIC, Australia
³School of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham, United Kingdom

The sedimentary basins of the British Isles, surrounded by plate boundaries variously active from Mesozoic to Cenozoic times, provide a superb natural laboratory for studying the influence of plate boundary forces on intraplate vertical motions. Synthesis of apatite fission-track analysis (AFTA) data from the Irish Sea Basin System and adjacent regions of the western British Isles reveals a series of cooling episodes during the Cretaceous-Cenozoic. Each episode is of regional extent and represents a major period of exhumation involving removal of ~1 km or more of section. These exhumation episodes can be correlated with major tectonic unconformities recognised within the sedimentary succession of the NE Atlantic Margin, but across the western British Isles the substantially higher exhumation means that little corresponding stratigraphic evidence for these events is preserved. These exhumation episodes correlate closely with key deformation events at adjacent plate boundaries, suggesting a causative link despite the large distances (up to 1500 km) separating the closest plate boundaries from the zones of exhumation. Similar km-scale erosional events are revealed by thermochronological studies in other intraplate regions, e.g. SE Australia, South Africa, Brazil. The low angle unconformities which result from these regional episodes of km-scale burial and subsequent exhumation have often been interpreted as representing periods of non-deposition and tectonic stability. Similar considerations have led to an erroneous view of the stability of many cratonic areas. Our results indicate that km-scale regional exhumation has affected many regions previously interpreted as areas of long-term stability, and that plate boundary deformation exerts the primary control on such episodes.

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