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Stewart G. Molyneux - One of the best experts on this subject based on the ideXlab platform.
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Silurian palynology and correlation of Inliers in the Midland Valley of Scotland
2001Co-Authors: Stewart G. Molyneux, Hugh F. Barron, Richard SmithAbstract:Silurian palynology and correlation of Inliers in the Midland Valley of Scotland Stewart Molyneux1, Hugh Barron2 and Richard Smith2 1British Geological Survey, Keyworth, Nottingham NG12 5GG, U.K. 2British Geological Survey, Murchison House, West Mains Road, Edinburgh EH9 3LA, U.K. Silurian successions in the Midland Valley of Scotland record the infilling of a Llandovery-Wenlock basin, but differences of detail between Silurian Inliers suggest the presence of local sub-basins with different histories of sedimentation. Unravelling the sedimentary and tectonic history of the Midland Valley depends on correlation between the Inliers. Llandovery marine facies have yielded graptolite and shelly faunas, and both have been used for correlation, but marine palynomorphs (acritarchs, chitinozoa) are also present. In the North Esk Inlier, the lowest palynological assemblage, from the late Llandovery Reservoir Formation, is reasonably diverse, but dominated by sphaeromorph acritarchs and species of Tylotopalla (T. deerlijkianum, T. astrifera). The assemblage suggests a comparatively shallow marine environment, consistent with interpretation of the graptolite fauna. The sphaeromorph-Tylotopalla assemblage also occurs in the Drumyork Flags Formation of the Girvan Main Inlier, at about the same chronostratigraphic level. Overlying successions in the North Esk and Girvan Main Inliers have yielded marine assemblages of lower diversity. Assemblages from the highest formation in the North Esk Inlier, the non-marine Henshaw Formation of Wenlock age, comprise mainly cryptospores and simple trilete spores (Ambitisporites), in contrast to the marginal marine assemblage from the Straiton Grits Formation of Wenlock age at Girvan.
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the age and correlation of skiddaw group early ordovician sediments in the cross fell Inlier northern england
Geological Magazine, 1990Co-Authors: A H Cooper, Stewart G. MolyneuxAbstract:The Skiddaw Group in the Cross Fell Inlier comprises the Catterpallot Formation of latest Tremadoc or earliest Arenig age, the Murton Formation of Arenig age, and the Kirkland Formation of early Llanvirn age. Each of these formations can be correlated with formations in the Skiddaw Group of the Lake District. The faulted contact of the Catterpallot and Kirkland formations is the probable extension of the Causey Pike Fault (CPF), which separates two distinct sequences in the Skiddaw Inlier of the northern Lake District. Contrasts across the CPF in the Cross Fell Inlier reflect those seen in the Skiddaw Inlier. The CPF is a major basement structure, separating markedly different successions in the Ordovician strata of northern England.
Abdelilah Fekkak - One of the best experts on this subject based on the ideXlab platform.
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Early Neoproterozoic rift-related magmatism in the Anti-Atlas margin of the West African craton, Morocco
Precambrian Research, 2014Co-Authors: J. Javier Álvaro, André Pouclet, Hassan Ezzouhairi, Abderrahmane Soulaimani, El Hafid Bouougri, Andrés Gil Imaz, Abdelilah FekkakAbstract:The Moroccan Anti-Atlas contains the relics of a Tonian(?)-early Cryogenian rift developed along the northern margin of the West African craton. A distinct tholeiitic volcanic suite of lava flows, sills and dikes is encased in the Jbel Lkest Group (Kerdous Inlier), the Taghdout Group (Zenaga Inlier), the U1–U4 units of the Bleida-Tachdamt Group (Bouazzer Elgraara Inlier), and the Lower Sedimentary Ensemble and Middle Volcanic Unit of the Tizi n’Taghatine Group (Siroua, Zenaga and Bouazzer Elgraara Inliers). Two magmatic groups are distinguished that originated from a spinel–garnet transition zone ranging from zero garnet content to moderately enriched residual garnet content in the source, and partial melting degrees decreasing from 10% to 3%. Incompatible element patterns indicate contribution of both asthenospheric and lithospheric components suggesting an initial rifting geotectonic context, with lithosphere thinning and asthenosphere upwelling, similar to other complex systems of rifts that dissected Rodinia during the Early Neoproterozoic.
Jun Ota - One of the best experts on this subject based on the ideXlab platform.
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an accurate and efficient voting scheme for a maximally all Inlier 3d correspondence set
IEEE Transactions on Pattern Analysis and Machine Intelligence, 2020Co-Authors: Hamdi Sahloul, Shouhei Shirafuji, Jun OtaAbstract:We present a highly accurate and efficient, yet simple, two-stage voting scheme for distinguishing Inlier 3D correspondences by densely assessing and ranking their local and global geometric consistencies. The strength of the proposed method stems from both the novel idea of post-validated voting set, as well as single-point superimposition transforms, which are computationally cheap and avoid rotational ambiguities. Using a well-known dataset consisting of various 3D models and numerous scenes that include different occlusion rates, the proposed scheme is evaluated against state-of-the-art 3D voting schemes, in terms of both the correspondence PR (precision-recall) AUC (area under curve), and the execution time. A total of 374 experiments were conducted for each method, which involved a combination of four models, 50 scenes, and two down-samplings. The proposed scheme outperforms the state-of-the-art 3D voting schemes in terms of both accuracy and speed. Quantitatively, the proposed scheme scores 97.0%±12.9% on the PR AUC metric, averaged over all of the experiments, while the two state-of-the-art schemes score 74.2%±22.2% and 78.3%±26.4%. Furthermore, the proposed scheme requires only 24.1%±6.0% of the time consumed by the fastest state-of-the-art scheme. The proposed voting scheme also demonstrates high robustness against occlusions and scarce Inliers.
Abderrahmane Soulaimani - One of the best experts on this subject based on the ideXlab platform.
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Early Neoproterozoic rift-related magmatism in the Anti-Atlas margin of the West African craton, Morocco
Precambrian Research, 2014Co-Authors: J. Javier Álvaro, André Pouclet, Hassan Ezzouhairi, Abderrahmane Soulaimani, El Hafid Bouougri, Andrés Gil Imaz, Abdelilah FekkakAbstract:The Moroccan Anti-Atlas contains the relics of a Tonian(?)-early Cryogenian rift developed along the northern margin of the West African craton. A distinct tholeiitic volcanic suite of lava flows, sills and dikes is encased in the Jbel Lkest Group (Kerdous Inlier), the Taghdout Group (Zenaga Inlier), the U1–U4 units of the Bleida-Tachdamt Group (Bouazzer Elgraara Inlier), and the Lower Sedimentary Ensemble and Middle Volcanic Unit of the Tizi n’Taghatine Group (Siroua, Zenaga and Bouazzer Elgraara Inliers). Two magmatic groups are distinguished that originated from a spinel–garnet transition zone ranging from zero garnet content to moderately enriched residual garnet content in the source, and partial melting degrees decreasing from 10% to 3%. Incompatible element patterns indicate contribution of both asthenospheric and lithospheric components suggesting an initial rifting geotectonic context, with lithosphere thinning and asthenosphere upwelling, similar to other complex systems of rifts that dissected Rodinia during the Early Neoproterozoic.
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Geochronological constraints on the polycyclic magmatism in the Bou Azzer-El Graara Inlier (Central Anti-Atlas Morocco)
Journal of African Earth Sciences, 2014Co-Authors: Olivier Blein, Dominique Gasquet, Abderrahmane Soulaimani, Thierry Baudin, Philippe Chevremont, Hassan Admou, Alain Cocherie, Emmanuel Egal, Nasrrddine Youbi, Philippe RazinAbstract:New U-Pb SHRIMP zircon ages from the Bou Azzer-El Graara onlier constrains the Neoproterozoic evolution of the Anti-Atlas during Pan-African orogenesis. Within the Central Anti-Atlas, the Bou Azzer-El Graara Inlier exposes a dismembered ophiolite, long considered to mark a late Neoproterozoic suture between the West African Craton in the south, and Neoproterozoic arcs to the north. From north to south, this Inlier includes four main geological units: a volcanic-arc, an ophiolite, a metamorphic complex and a continental platform. Several plutons intrude the volcanic-arc, the ophiolite, the metamorphic complex, and post-orogenic volcanic and sedimentary deposits unconformably cover these terranes. The age of the volcanic-arc is reported here for the first time. Analyses of zircon of two rhyolites provide ages of 761 ± 7 Ma and 767 ± 7 Ma. Zircons from two gneisses provide dates of 755 ± 9 Ma and 745 ± 5 Ma. Both dates are considered best estimates of the crystallization ages of their igneous protoliths. Analyses of zircon from two granitic bodies, which crosscut gneisses, provide younger dates of 702 ± 5 Ma and 695 ± 7 Ma. The age of an aplitic body of the ophiolite is reported here for the first time, as 658 ± 8 Ma (SHRIMP U-Pb on zircons). Theses ages suggest the existence of three distinct orogenic events during Cryogenian times: (i) 770-760 Ma Tasriwine-Tichibanine orogeny with rollback of the subducting oceanic plate, leading to the formation of back-arc basins; (ii) 755-695 Ma Iriri-n'Bougmmane orogeny; and (iii) the 660-640 Ma Bou Azzer orogeny involving the formation and the emplacement of the Bou Azer ophiolite. During Ediacaran times, the Bou Azzer-El Graara Inlier is characterized with the development of a continental volcanic arc between 630 and 580 Ma (Bou Lbarod Group, 625 ± 8 Ma; Bleïda granodiorite, 586 ± 15 Ma), and strike-slip pull-apart basins (Tiddiline Group, 606 ± 4 Ma and 606 ± 5 Ma). These volcanic and sedimentary Lower Ediacaran sequences are deformed before the felsic pyroclastic deposits of the Ouarzazate Group (567 ± 5 Ma and 566 ± 4 Ma). Finally, the Ouarzazate Group is overlain by early Cambrian volcanic deposits of the Jbel Boho Formation (541 ± 6 Ma).
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reply to comment on u pb baddeleyite ages and geochemistry of dolerite dykes in the bas draa Inlier of the anti atlas of morocco newly identified 1380 ma event in the west african craton by andre michard and dominique gasquet
Lithos, 2013Co-Authors: Abderrahmane Soulaimani, Nasrrddine Youbi, Ulf Soderlund, Mauricio Ibanezmejia, Abdelhakim El Bahat, Richard E Ernst, Moha Ikenne, Brian CousensAbstract:Baddeleyite (ZrO2) is today recognized as the key mineral for dating the emplacement of mantle-derived igneous rocks, primarily gabbro and dolerite dykes and sills. The comment by Michard and Gasquet calls for a discussion on the significance of baddeleyite U-Pb TIMS dates of two dykes in the Bas-Draa Inlier, dated at 1381 +/- 8 and 1384 +/- 6 Ma, presented in El Bahat et al. (2013-in this issue). They suggest that the U-Pb systematics were "seriously perturbed in the Bas-Draa region" with the main argument being a lack of age matches between the ca. 1385 Ma dykes in Bas-Draa and the 2040, 1650 and 885 Ma dykes in adjacent Inliers to the east. To infer an older age for these dykes, as suggested by Michard and Gasquet, and explain the ca. 1385 Ma TIMS results would require two separate events of perturbation, in the Mesoproterozoic and a subsequent Variscan event. However, such an alternative is improbable from basic theoretical reasoning using U-Pb isotopic systematics and our current understanding of the behaviour of baddeleyite in metamorphic systems. In addition, we present new LA-ICPMS U-Pb age data of baddeleyite from one of the dated dykes from Bas-Draa. The new LA-ICPMS U-Pb age of 1416 +/- 7 Ma is slightly but significantly older than our TIMS 1384 +/- 6 Ma upper intercept age, nevertheless confirming this dyke could not correspond to any of the other mafic intrusions dated in the Inliers to the east. The IA-ICPMS result also contributes to a deeper understanding on the effects of secondary processes in baddeleyite in general, and suggests a modified methodological approach for samples with complex geological histories. (C) 2013 Elsevier B.V. All rights reserved. (Less)
Jim Finlay - One of the best experts on this subject based on the ideXlab platform.
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evolution of the mount woods Inlier northern gawler craton southern australia an integrated structural and aeromagnetic analysis
Tectonophysics, 2003Co-Authors: Peter G Betts, Rick Valenta, Jim FinlayAbstract:Structural mapping integrated with interpretation and forward modelling of aeromagnetic data form complimentary and powerful tools for regional structural analysis because both techniques focus on architecture and overprinting relationships. This approach is used to constrain the geometry and evolution of the sparsely exposed Mount Woods Inlier in the northern Gawler Craton. The Mount Woods Inlier records a history of poly-phase deformation, high-temperature metamorphism, and syn- and post-orogenic magmatism between ca. 1736 and 1584 Ma. The earliest deformation involved isoclinal folding, and the development of bedding parallel and axial planar gneissic foliation (S1). This was accompanied by high-temperature, upper amphibolite to granulite facies metamorphism at ca. 1736 Ma. During subsequent north–south shortening (D2), open to isoclinal south–southeast-oriented F2 folds developed as the Palaeoproterozoic successions of the Inlier were thrust over the Archaean nuclei of the Gawler Craton. The syn-D2 Engenina Adamellite was emplaced at ca. 1692 Ma. The post-D2 history involved shear zone development and localised folding, exhumation of metamorphic rocks, and deposition of clastic sediments prior to the emplacement of the ca. 1584 Ma Granite Balta Suite. The Mount Woods Inlier is interpreted as the northern continuation of the Kimban Orogen.
