Late Caledonian sinistral displacements in Britain: Implications for a three‐plate collision model

Abstract

In recent years, most geotectonic syntheses of the North Atlantic Caledonides have adopted a two plate configuration, with a roughly E‐W closure direction between Laurentia and Baltica producing the N‐S striking Scandinavian and East Greenland Caledonides and inducing dextral strike‐slip along the NE‐SW oriented British sector of the Iapetus suture. The North German‐Polish Caledonides are a third arm to the Appalachian‐N. Atlantic Caledonide orogen. Recently, Ziegler has proposed that the mid‐Palaeozoic deformation belts of S. Britain ‐ N. Germany‐Poland and also of central Europe were produced by the northward impact of microcontinental fragments onto the southern margin of the already sutured continental mass of Laurentia‐Baltica. Some ascribe the whole Appalachian orogen to a sequence of terrane accretion events in mid‐Ordovician through mid‐Devonian time. A N‐S collision direction would induce sinistral shear across the British sector of the Iapetus suture. In this paper, we outline the evidence for sinistral displacements within the British Caledonides and for their age. We conclude that the “non‐metamorphic Caledonides” were produced by the northerly accretion of a Cadomian terrane in late Silurian‐early Devonian time, and that this event was entirely separate from the earlier Laurentia‐Baltica collision which produced the post‐Grampian thrust related “metamorphic Caledonides” of Scotland.

The North Pennine batholith (Weardale Granite) of northern England: new data on its age and form

“…Such transpression could have provided mechanisms both for triggering the generation of magma and for controlling its emplacement (Leake 1990;Hutton & Reavy 1992). Given that the shear sense was sinistral on these structures (Soper & Hutton 1984), the disposition of the plutons is compatible with their development along tensional fracture systems bridging between major shear zones on the north and south side of the Alston Block. To the north, a concealed Acadian thrust zone along strike from the Causey Pike Thrust has been interpreted by Chadwick & Holliday (1991) The gravity modelling is not particularly sensitive to the geometry assumed for the bases of the plutons (e.g.…”

How the Neoproterozoic S-isotope record illuminates the genesis of vein gold systems: an example from the Dalradian Supergroup in Scotland

“…The northwards drift of Laurentia relative to Gondwana at c. 570 Ma began to open the Iapetus Ocean (Cawood et al 2001). The subsequent closure of the Iapetus Ocean caused the Grampian Orogenic Event during the mid-Palaeozoic (Soper & Hutton 1984;Pickering et al 1988;Soper et al 1992). …”

Transitional geometries between gently plunging and steeply plunging folds: an example from the Lower Palaeozoic Brabant Massif, Anglo-Brabant deformation belt, Belgium

“…The domains in the Southern Uplands form part of a transpression zone related to the oblique closure of the Iapetus Ocean (Soper & Hutton 1984;Soper et al 1992). In contrast, although oblate strains, as inferred in the transition zone, are considered a common feature in transpression zones (Sanderson & Marchini 1984;Fossen & Tikoff 1993;Dewey et al 1998) and the Zshaped geometry of the type B folds may be compatible with a dextral shear during contraction, we do not have field evidence for an overall transpressive deformation.…”