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Brittle tectonism in relation to the Palaeogene evolution of the Thulean/NE Atlantic domain: a study in Ulster
Author(s) -
GEOFFROY LAURENT,
BERGERAT FRANCOISE,
ANGELIER JACQUES
Publication year - 1996
Publication title -
geological journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.721
H-Index - 54
eISSN - 1099-1034
pISSN - 0072-1050
DOI - 10.1002/(sici)1099-1034(199609)31:3<259::aid-gj711>3.0.co;2-8
Subject(s) - geology , paleogene , tectonics , paleontology , cretaceous , mantle plume , igneous rock , seismology , lithosphere
The tectonic effects of the Thulean mantle plume on the opening of the North Atlantic Ocean is still poorly understood. An analysis of the brittle deformation affecting the Late Cretaceous Chalk and Lower Tertiary igneous formations cropping out in Ulster (Northern Ireland), part of the Thulean Province, leads to the recognition of two tectonic phases. Each of these phases is characterized by different stress regimes with similar trends of the horizontal maximum principal stress σ H . The first phase, syn‐magmatic and dominated by NE–SW to ENE–WSW extension, occurred during the Palaeocene. It is followed by a second post‐magmatic phase, characterized initially by a probably Eocene strike‐slip to compressional palaeo‐stress regime with σ 1 (=σ H ) trending NE–SW to NNE–SSW associated with the partial reactivation (as reverse faults) of normal faults formed during the first phase NE–SW extension. This episode is postdated by an Oligocene extension, with σ H (=σ 2 ) still striking NNE–SSW/NE–SW, which reactivated Eocene strike‐slip faults as nearly vertical dip‐slip normal faults. This Palaeogene tectonic evolution is consistent with the tectonic evolution of similar age in western Scotland and in the Faeroe Islands. In particular, the post‐magmatic NE–SW compression is here related to the ‘Faeroe compressive event’, which is related to the earliest stages of drift of the Greenland plate.