The multi-scale control of crustal structures on the exhumation of the
British-Irish Isles, revealed by 40 years of AFT studies
Abstract
A compilation of legacy and new low-temperature thermochronological data
from the British-Irish Isles and their surrounding offshore shelves
yielded c. 700 AFT ages and c. 180 AHe ages from 29 peer-reviewed
papers, 27 Geotrack industry reports and several new unpublished studies
from offshore Ireland. The compilation shows for the first time a
regional age pattern, with older AFT ages in Scotland and Northern
Ireland than in the rest of Ireland. This pattern is tentatively
attributed to the influence of the Anton-Dohrn Transfer Zone (ADTZ)
during an Early Cretaceous phase of plate-wide uplift that resulted in
more exhumation to the SW of the transfer zone than to the NE.
Caledonian faults might also create differential exhumation of the
tectonic blocks between them, as is observed in the compilation of AFT
data from northern Scotland and this could explain the dispersion in the
timing of exhumation seen on the North Porcupine High, offshore Ireland.
Finally, the Paleogene exhumation visible in the Central Irish Sea, and
attributed in recent years to igneous underplating, has not been
detected in the Malin Sea-Outer Hebrides, despite the area being
underlain by a high-velocity body also interpreted as igneous
underplating. In conclusion, a detailed analysis of a large dataset of
low-temperature thermochronological has revealed the possible influence
of major crustal structure on the Mesozoic exhumation of this part of
the NE Atlantic Margin, with large-scale decoupling occurring at a
transfer zone and medium-scale decoupling occurring along regional-scale
faults. The dataset also shed some doubts on the generic nature of
exhumation caused by igneous underplating which has been much discussed
in recent years.