Regional Intraplate Exhumation Related to Plate Boundary Deformation:

Paul Green¹, Ian Duddy¹, and Simon Holford^2
1Geotrack International, Melbourne, Australia
²University of Adelaide, Adelaide, Australia

The sedimentary basins of the UK, surrounded by plate boundaries variously active from Mesozoic to Cenozoic times, provide a superb natural laboratory for studying intraplate effects. AFTA studies in the Irish Sea Basin System have revealed a series of exhumation episodes, each of regional extent (~106 km²) involving removal of around 1 km or more of section. Structural evidence of correlative events on the offshore North Atlantic Margin has attracted appreciable recent interest, but onshore the effects of these episodes are much more pronounced (to such a degree that no corresponding stratigraphic evidence is preserved). These episodes correlate closely with key events at adjacent plate boundaries, suggesting a causative link. Similar km-scale erosional events are revealed by thermochronologic studies in other intraplate regions, e.g. SE Australia, South Africa, Brazil. Sequence stratigraphic studies on the Arabia Platform have reported striking evidence of similar effects on a smaller (~10-100 m) vertical scale, suggesting a continuum of events exists, only the larger of which can be resolved by paleo-thermal methods. The resulting low angle unconformities, often interpreted as representing periods of non-deposition, may actually disguise episodes of km-scale burial and subsequent exhumation. This lack of significant angular disconformity has also led to an erroneous view of the stability of many cratonic areas. As yet no convincing mechanism has been put forward for producing such events, despite the fact that they can exert critical control on regional hydrocarbon prospectivity. We suggest that serious attention should be directed to investigating the underlying mechanisms.

AAPG Search and Discovery Article #90072 © 2007 AAPG and AAPG European Region Conference, Athens, Greece