The geology of SW Iberia records a sequence of geologic events from the Cambrian-Early Ordovician rifting and subsequent passive margin development along the southern flank of the Rheic Ocean, to onset of oblique (sinistral) subduction in the Devonian, followed by oblique terrane accretion, ocean closure/continental collision and orogenic collapse. As a result, SW Iberia contains the southernmost exposure of the Pangean suture in the European Variscides. This suture zone is characterized by a belt of dismembered oceanic-related rocks and HP metamorphic complexes which are tectonically juxtaposed with the Gondwanan passive margin to the north (OMZ) and with the exotic South Portuguese Terrane to the south, which is thought to be either a remnant of Avalonia or Meguma.

Synorogenic basins formed in all lithospheric units involved in the Variscan orogeny, i.e. the Gondwanan and Laurussian continental margins and also in the oceanic realm. However, examples of the latter are only preserved in SW Iberia. On the other hand, synorogenic deposits of the Gondwanan foreland are only preserved in NW Iberia, whereas remains of both continental margins exist in SW Iberia. Record of Variscan synorogenic basins also exists in basement exposures within the Alpine realm that occupies the eastern half of the Iberian Peninsula and the Balearic Islands. These, which are less known and in some cases of uncertain affinities, are described in a separate section.

The Silurian – Early Devonian Arisaig Group of the Avalon terrane in northern mainland Nova Scotia consists mainly of thinly bedded sandstones, siltstones, and shales deposited in a near shore environment. These strata were deformed in the middle Devonian to form regional northeast- to NNE-trending folds and record deformation processes in the shallow crust during the Acadian orogeny, one of the most regionally extensive orogenic events in the Canadian Appalachians. Structural features in the Arisaig Group are consistent with fold propagation associated with thrust fault geometry and coeval local extension recorded by a set of conjugate normal faults. Many outcrop-scale folds have sheared limbs and show evidence of a complex progressive deformation. Folding was predominantly accomplished by bulk rotation and flattening above thrust fault tips. Early structures (D1–D2) produced regional cylindrical folds, whereas later (D3a, D3b, D3c) structures produced conical folds. D1–D3 fold orientations show high variability, but are consistent with progressive deformation related to reactivation and coeval dextral strike-slip movement along the Hollow Fault. The style of deformation is compatible with models in which strain is partitioned into preexisting shear zones in the basement, with folds in the overlying Arisaig Group initiated above the tips of upward-propagating thrusts as second-order structures related to movement along those shear zones. Taken together, these data indicate that fold mechanisms and geometry in the shallow crust during the Acadian orogeny in mainland Nova Scotia may be related to dextral strike-slip along major faults in the basement and co-genetic upward-propagating thrusts that rotated and flattened overlying strata.

Health Libraries ReviewVolume 3, Issue 4 p. 255-256 Free Access Electronic requesting, storage and delivery of documents J. A. Braid, J. A. Braid The British Library Document Supply CentreSearch for more papers by this author J. A. Braid, J. A. Braid The British Library Document Supply CentreSearch for more papers by this author First published: December 1986 https://doi.org/10.1046/j.1365-2532.1986.3402484.xAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Volume3, Issue4December 1986Pages 255-256 RelatedInformation