https://earthwise.bgs.ac.uk/index.php?title=Obduction_of_the_Ballantrae_Complex,_Southern_Uplands&feed=atom&action=historyObduction of the Ballantrae Complex, Southern Uplands - Revision history2024-03-28T11:31:10ZRevision history for this page on the wikiMediaWiki 1.41.0https://earthwise.bgs.ac.uk/index.php?title=Obduction_of_the_Ballantrae_Complex,_Southern_Uplands&diff=34865&oldid=prevDbk: Text replacement - "'''From: Stone, P, McMillan, A A, Floyd, J D, Barnes, R P, and Phillips, E R. 2012. British regional geology: South of Scotland. Fourth edition. Keyworth, Nottingham: British Geological Survey.'''" to "{{SSRG}}"2018-02-01T15:11:05Z<p>Text replacement - "'''From: Stone, P, McMillan, A A, Floyd, J D, Barnes, R P, and Phillips, E R. 2012. <a href="/index.php/British_regional_geology:_South_of_Scotland" title="British regional geology: South of Scotland">British regional geology: South of Scotland.</a> Fourth edition. Keyworth, Nottingham: British Geological Survey.'''" to "{{SSRG}}"</p>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>== The following are related articles: ==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>== The following are related articles: ==</div></td></tr>
</table>Dbkhttps://earthwise.bgs.ac.uk/index.php?title=Obduction_of_the_Ballantrae_Complex,_Southern_Uplands&diff=19879&oldid=prevScotfot at 19:48, 26 July 20152015-07-26T19:48:07Z<p></p>
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 19:48, 26 July 2015</td>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>== Obduction of the Ballantrae Complex ==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>== Obduction of the Ballantrae Complex ==</div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>The Ballantrae Complex is an assemblage of mantle and crustal rocks formed in a variety of geotectonic settings: island arc, marginal basin and oceanic island. The various components were dismembered and juxtaposed during the obduction of the Ballantrae Complex onto the margin of Laurentia, which can be regarded as part of the Grampian Event. The initiation of obduction is dated by the radiometric (K-Ar) age of 478±8 Ma obtained from amphibolite within the dynamothermal metamorphic aureole at the base of the northern serpentinite belt. The graptolite fauna from mudstone associated with a serpentinite conglomerate at North Ballaird is likely to date ‘obduction-in-progress’ to the late Arenig. Obduction would then have been complete prior to the deposition of the Llanvirn basal beds of the Barr Group (the Kirkland Conglomerate Formation) on top of the assembled Ballantrae Complex. Detailed structure within the obducted ophiolite is difficult to unravel, but some indication of the structural complexity is shown by the tectonic repetition of a thin, fossiliferous mudstone–chert–lava succession between Bennane Head and Balcreuchan Port ([[Media:P912322.<del style="font-weight: bold; text-decoration: none;">png</del>|P912322]]). The structural contacts between the different components of the complex are generally steep, and there is evidence for widespread strike-slip movement along the major faults.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">[[File:P912322.jpg|thumbnail|Geological sketch map of the Balcreuchan Port to Bennane Head area showing the structural repetition of the volcanosedimentary succession. P912322.]]</ins></div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">[[File:P912321.jpg|thumbnail|Possible model for the development of the various components of the Ballantrae Complex within an oceanic volcanic arc and backarc basin. P912321.]]</ins></div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>The Ballantrae Complex is an assemblage of mantle and crustal rocks formed in a variety of geotectonic settings: island arc, marginal basin and oceanic island. The various components were dismembered and juxtaposed during the obduction of the Ballantrae Complex onto the margin of Laurentia, which can be regarded as part of the Grampian Event. The initiation of obduction is dated by the radiometric (K-Ar) age of 478±8 Ma obtained from amphibolite within the dynamothermal metamorphic aureole at the base of the northern serpentinite belt. The graptolite fauna from mudstone associated with a serpentinite conglomerate at North Ballaird is likely to date ‘obduction-in-progress’ to the late Arenig. Obduction would then have been complete prior to the deposition of the Llanvirn basal beds of the Barr Group (the Kirkland Conglomerate Formation) on top of the assembled Ballantrae Complex. Detailed structure within the obducted ophiolite is difficult to unravel, but some indication of the structural complexity is shown by the tectonic repetition of a thin, fossiliferous mudstone–chert–lava succession between Bennane Head and Balcreuchan Port ([[Media:P912322.<ins style="font-weight: bold; text-decoration: none;">jpg</ins>|P912322]]). The structural contacts between the different components of the complex are generally steep, and there is evidence for widespread strike-slip movement along the major faults.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>Though there is no proof of the subduction polarity, it is conceptually easier to envisage southward subduction of marginal basin crust beneath an Iapetus island arc, since this would make arc–continent collision inevitable ([[Media:P912321.<del style="font-weight: bold; text-decoration: none;">png</del>|P912321]]). To continue the closure of the Iapetus Ocean, collision and ophiolite obduction must then have been followed by a reversal in subduction direction (a well-established phenomenon elsewhere in the geological record), so that the ocean crust was lost northward beneath the Laurentian continental margin, now endowed with an attached ophiolite complex. Once northward subduction was established, the build-up of the Southern Uplands accretionary terrane could commence.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>Though there is no proof of the subduction polarity, it is conceptually easier to envisage southward subduction of marginal basin crust beneath an Iapetus island arc, since this would make arc–continent collision inevitable ([[Media:P912321.<ins style="font-weight: bold; text-decoration: none;">jpg</ins>|P912321]]). To continue the closure of the Iapetus Ocean, collision and ophiolite obduction must then have been followed by a reversal in subduction direction (a well-established phenomenon elsewhere in the geological record), so that the ocean crust was lost northward beneath the Laurentian continental margin, now endowed with an attached ophiolite complex. Once northward subduction was established, the build-up of the Southern Uplands accretionary terrane could commence.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>== Bibliography ==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>== Bibliography ==</div></td></tr>
</table>Scotfothttps://earthwise.bgs.ac.uk/index.php?title=Obduction_of_the_Ballantrae_Complex,_Southern_Uplands&diff=19114&oldid=prevScotfot at 21:25, 20 July 20152015-07-20T21:25:17Z<p></p>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>__FORCETOC__</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>__FORCETOC__</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>== The following are related articles: ==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>== The following are related articles: ==</div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>: Obduction of the Ballantrae Complex, Southern Uplands</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>: <ins style="font-weight: bold; text-decoration: none;">[[</ins>Obduction of the Ballantrae Complex, Southern Uplands<ins style="font-weight: bold; text-decoration: none;">]]</ins></div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>: Deformation of the Girvan succession, Southern Uplands</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>: <ins style="font-weight: bold; text-decoration: none;">[[</ins>Deformation of the Girvan succession, Southern Uplands<ins style="font-weight: bold; text-decoration: none;">]]</ins></div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>: Southern Uplands accretionary complex</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>: <ins style="font-weight: bold; text-decoration: none;">[[</ins>Southern Uplands accretionary complex<ins style="font-weight: bold; text-decoration: none;">]]</ins></div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>: Late Caledonian dyke swarms, Southern Uplands</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>: <ins style="font-weight: bold; text-decoration: none;">[[</ins>Late Caledonian dyke swarms, Southern Uplands<ins style="font-weight: bold; text-decoration: none;">]]</ins></div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>: Late Caledonian plutonic rocks, Southern Uplands</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>: <ins style="font-weight: bold; text-decoration: none;">[[</ins>Late Caledonian plutonic rocks, Southern Uplands<ins style="font-weight: bold; text-decoration: none;">]]</ins></div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>== Obduction of the Ballantrae Complex ==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>== Obduction of the Ballantrae Complex ==</div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>The Ballantrae Complex is an assemblage of mantle and crustal rocks formed in a variety of geotectonic settings: island arc, marginal basin and oceanic island. The various components were dismembered and juxtaposed during the obduction of the Ballantrae Complex onto the margin of Laurentia, which can be regarded as part of the Grampian Event. The initiation of obduction is dated by the radiometric (K-Ar) age of 478±8 Ma obtained from amphibolite within the dynamothermal metamorphic aureole at the base of the northern serpentinite belt. The graptolite fauna from mudstone associated with a serpentinite conglomerate at North Ballaird is likely to date ‘obduction-in-progress’ to the late Arenig. Obduction would then have been complete prior to the deposition of the Llanvirn basal beds of the Barr Group (the Kirkland Conglomerate Formation) on top of the assembled Ballantrae Complex. Detailed structure within the obducted ophiolite is difficult to unravel, but some indication of the structural complexity is shown by the tectonic repetition of a thin, fossiliferous mudstone–chert–lava succession between Bennane Head and Balcreuchan Port (P912322). The structural contacts between the different components of the complex are generally steep, and there is evidence for widespread strike-slip movement along the major faults.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>The Ballantrae Complex is an assemblage of mantle and crustal rocks formed in a variety of geotectonic settings: island arc, marginal basin and oceanic island. The various components were dismembered and juxtaposed during the obduction of the Ballantrae Complex onto the margin of Laurentia, which can be regarded as part of the Grampian Event. The initiation of obduction is dated by the radiometric (K-Ar) age of 478±8 Ma obtained from amphibolite within the dynamothermal metamorphic aureole at the base of the northern serpentinite belt. The graptolite fauna from mudstone associated with a serpentinite conglomerate at North Ballaird is likely to date ‘obduction-in-progress’ to the late Arenig. Obduction would then have been complete prior to the deposition of the Llanvirn basal beds of the Barr Group (the Kirkland Conglomerate Formation) on top of the assembled Ballantrae Complex. Detailed structure within the obducted ophiolite is difficult to unravel, but some indication of the structural complexity is shown by the tectonic repetition of a thin, fossiliferous mudstone–chert–lava succession between Bennane Head and Balcreuchan Port (<ins style="font-weight: bold; text-decoration: none;">[[Media:</ins>P912322<ins style="font-weight: bold; text-decoration: none;">.png|P912322]]</ins>). The structural contacts between the different components of the complex are generally steep, and there is evidence for widespread strike-slip movement along the major faults.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>Though there is no proof of the subduction polarity, it is conceptually easier to envisage southward subduction of marginal basin crust beneath an Iapetus island arc, since this would make arc–continent collision inevitable (P912321). To continue the closure of the Iapetus Ocean, collision and ophiolite obduction must then have been followed by a reversal in subduction direction (a well-established phenomenon elsewhere in the geological record), so that the ocean crust was lost northward beneath the Laurentian continental margin, now endowed with an attached ophiolite complex. Once northward subduction was established, the build-up of the Southern Uplands accretionary terrane could commence.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>Though there is no proof of the subduction polarity, it is conceptually easier to envisage southward subduction of marginal basin crust beneath an Iapetus island arc, since this would make arc–continent collision inevitable (<ins style="font-weight: bold; text-decoration: none;">[[Media:</ins>P912321<ins style="font-weight: bold; text-decoration: none;">.png|P912321]]</ins>). To continue the closure of the Iapetus Ocean, collision and ophiolite obduction must then have been followed by a reversal in subduction direction (a well-established phenomenon elsewhere in the geological record), so that the ocean crust was lost northward beneath the Laurentian continental margin, now endowed with an attached ophiolite complex. Once northward subduction was established, the build-up of the Southern Uplands accretionary terrane could commence.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>== Bibliography ==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>== Bibliography ==</div></td></tr>
</table>Scotfothttps://earthwise.bgs.ac.uk/index.php?title=Obduction_of_the_Ballantrae_Complex,_Southern_Uplands&diff=18825&oldid=prevDbk: 1 revision imported2015-07-20T13:46:54Z<p>1 revision imported</p>
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<p><b>New page</b></p><div>'''From: Stone, P, McMillan, A A, Floyd, J D, Barnes, R P, and Phillips, E R. 2012. [[British regional geology: South of Scotland|British regional geology: South of Scotland.]] Fourth edition. Keyworth, Nottingham: British Geological Survey.'''<br />
__FORCETOC__<br />
== The following are related articles: ==<br />
: Obduction of the Ballantrae Complex, Southern Uplands<br />
: Deformation of the Girvan succession, Southern Uplands<br />
: Southern Uplands accretionary complex<br />
: Late Caledonian dyke swarms, Southern Uplands<br />
: Late Caledonian plutonic rocks, Southern Uplands<br />
<br />
== Obduction of the Ballantrae Complex ==<br />
The Ballantrae Complex is an assemblage of mantle and crustal rocks formed in a variety of geotectonic settings: island arc, marginal basin and oceanic island. The various components were dismembered and juxtaposed during the obduction of the Ballantrae Complex onto the margin of Laurentia, which can be regarded as part of the Grampian Event. The initiation of obduction is dated by the radiometric (K-Ar) age of 478±8 Ma obtained from amphibolite within the dynamothermal metamorphic aureole at the base of the northern serpentinite belt. The graptolite fauna from mudstone associated with a serpentinite conglomerate at North Ballaird is likely to date ‘obduction-in-progress’ to the late Arenig. Obduction would then have been complete prior to the deposition of the Llanvirn basal beds of the Barr Group (the Kirkland Conglomerate Formation) on top of the assembled Ballantrae Complex. Detailed structure within the obducted ophiolite is difficult to unravel, but some indication of the structural complexity is shown by the tectonic repetition of a thin, fossiliferous mudstone–chert–lava succession between Bennane Head and Balcreuchan Port (P912322). The structural contacts between the different components of the complex are generally steep, and there is evidence for widespread strike-slip movement along the major faults.<br />
<br />
Though there is no proof of the subduction polarity, it is conceptually easier to envisage southward subduction of marginal basin crust beneath an Iapetus island arc, since this would make arc–continent collision inevitable (P912321). To continue the closure of the Iapetus Ocean, collision and ophiolite obduction must then have been followed by a reversal in subduction direction (a well-established phenomenon elsewhere in the geological record), so that the ocean crust was lost northward beneath the Laurentian continental margin, now endowed with an attached ophiolite complex. Once northward subduction was established, the build-up of the Southern Uplands accretionary terrane could commence.<br />
<br />
== Bibliography ==<br />
Akhurst, M C, McMillan, A A, Kimbell, G S, Stone, P, and Merriman, R J. 2001. Silurian subduction-related assembly of fault-defined tracts at the Laurieston Fault, Southern Uplands accretionary terrane, Scotland, UK. Transactions of the Royal Society of Edinburgh: Earth Sciences, Vol. 91, 435–446.<br />
<br />
Anderson, T B. 2001. Structural interpretations of the Southern Uplands Terrane. Transactions of the Royal Society of Edinburgh: Earth Sciences, Vol. 91, 363–373.<br />
<br />
Anderson, T B, and Oliver, G J H. 1986. The Orlock Bridge Fault: a major late Caledonian sinistral fault in the Southern Uplands terrane, British Isles. Transactions of the Royal Society of Edinburgh: Earth Sciences, Vol. 77, 203–222.<br />
<br />
Armstrong, H A, Owen, A W, Scrutton, C T, Clarkson, E N K, and Taylor, C M. 1996. Evolution of the Northern Belt, Southern Uplands: implications for the Southern Uplands controversy. Journal of the Geological Society of London, Vol. 153, 197–205.<br />
<br />
Barnes, R P, and Stone, P. 1999. Trans-Iapetus contrasts in the geological development of southern Scotland (Laurentia) and the Lakesman Terrane (Avalonia). 307–323 in In sight of the Suture: the Palaeozoic geology of the Isle of Man in its Iapetus Ocean context. Woodcock, N H, Quirk, D G, Fitches, W R, and Barnes, R P (editors). Geological Society of London Special Publication, No. 160.<br />
<br />
Barnes, R P, Lintern, B C, and Stone, P. 1989. Timing and regional implications of deformation in the Southern Uplands of Scotland. Journal of the Geological Society of London, Vol. 146, 905–908.<br />
<br />
Kimbell, G S, and Stone, P. 1995. Crustal magnetisation variations across the Iapetus Suture Zone. Geological Magazine, Vol. 132, 599–609.<br />
<br />
Leake, R C, and Cooper, C. 1983. The Black Stockarton Moor subvolcanic complex, Galloway. Journal of the Geological Society of London, Vol. 140, 665–676.<br />
<br />
McCurry, J A, and Anderson, T B. 1989. Landward vergence in the Lower Palaeozoic, Southern Uplands–Down–Longford terrane. Geology, Vol. 17, 630–633.<br />
<br />
Merriman, R J, and Roberts, B. 2001. Low-grade metamorphism in the Scottish Southern Uplands terrane: deciphering the patterns of accretionary burial, shearing and cryptic aureoles. Transactions of the Royal Society of Edinburgh: Earth Sciences, Vol. 91, 521–537.<br />
<br />
Needham, D T. 2004. Deformation in Moffat Shale detachment zones in the western part of the Scottish Southern Uplands. Geological Magazine, Vol.141, 441–453.<br />
<br />
Needham, D T, and Knipe, R J. 1986. Accretion- and collision-related deformation in the Southern Uplands accretionary wedge. Geology, Vol. 14, 303–306.<br />
<br />
Phillips, E R, Barnes, R P, Boland, M P, Fortey, N J, and McMillan, A A. 1995. The Moniaive Shear Zone: a major zone of sinistral strike-slip deformation in the Southern Uplands of Scotland. Scottish Journal of Geology, Vol. 31, 139–149.<br />
<br />
Rock, N M S, Gaskarth, J W, and Rundle, C C. 1986. Late Caledonian dyke-swarms in southern Scotland: a regional zone of primitive K-rich lamprophyres and associated veins. Journal of Geology, Vol. 94, 505–522.<br />
<br />
Rushton, A W A, Stone, P, and Hughes, R A. 1996. Biostratigraphical control of thrust models for the Southern Uplands of Scotland. Transactions of the Royal Society of Edinburgh: Earth Sciences, Vol. 86, 137–152.<br />
<br />
Thirlwall, M F. 1988. Geochronology of late Caledonian magmatism in Northern Britain. Journal of the Geological Society of London, Vol. 145, 951–967.<br />
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[[Category:South of Scotland]]</div>Lmo