Lyell Collection
Journal of the Geological Society
Lyell Centre  |   Lyell Collection  |   Subscriptions   |   Geological Society  |   Email alerts  |   Online bookshop  |   Help

Keywords:
Author:
Advanced search>>
This Article
Right arrow Full Text (PDF)
Right arrow References
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow Request Permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by PHILLIPS, E.
Right arrow Search for Related Content
GeoRef
Right arrow GeoRef Citation
Journal of the Geological Society; 1991; v. 148; issue.6; p. 1091-1100;
DOI: 10.1144/gsjgs.148.6.1091
© 1991 Geological Society of London

Article

Progressive deformation of the South Stack and New Harbour Groups, Holy Island, western Anglesey, North Wales

EMRYS PHILLIPS

Department of Geology, University of Wales, PO Box 914, Cardiff

The Monian Supergroup of western Anglesey comprises three major lithostratigraphic units: the South Stack (oldest), New Harbour and Gwna Groups. In northern and western Anglesey, deformation and metamorphism each increase in intensity downward through the Monian Supergroup, especially towards the base of the New Harbour Group. The variation in style and apparent intensity of deformation recorded by the South Stack and New Harbour Groups were governed by gross lithological differences. A correlation is proposed between the deformation histories of the New Harbour and South Stack Groups. Early deformation of the supergroup produced a pervasive bedding-parallel S1 fabric (chlorite) in both the New Harbour and, to a lesser extent, South Stack Groups. Development of the major, SE-verging F2 Penrhyn Mawr and Rhoscolyn anticlines, and associated minor folds also produced an axial planar S2 pressure solution and crenulation cleavage (phengite). The Rhoscolyn anticline was subsequently modified by the localized development of recumbent, mesoscale F3 folds with an axial planar pressure-solution cleavage (phengite to phengitic muscovite). The F3 event may have accompanied an episode of thrust faulting. Deformation of the South Stack and New Harbour Groups was accompanied by a progressive regional greenschist facies metamorphic event. The simplest interpretation of the deformation history of the Monian Supergroup involves a progressive SE-directed shear event which occurred prior to the deposition of an Ordovician overstep sequence on Anglesey.





This article has been cited by other articles:


Home page
 Journal of the Geological SocietyHome page
S. H. Treagus, S. H. Treagus, J. E. Treagus, and G. T. R. Droop
Superposed deformations and their hybrid effects: the Rhoscolyn Anticline unravelled
Journal of the Geological Society, 2003; 160: 117 - 136.
[Abstract] [Full Text] [PDF]

Home page
 Geological Society, London, Special PublicationsHome page
J. F. W. Stowell, A. P. Watson, and N. F. C. Hudson
Geometry and population systematics of a quartz vein set, Holy Island, Anglesey, North Wales
Geological Society, London, Special Publications, 1999; 155: 17 - 33.
[Abstract] [PDF]