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Jens Ulrich - One of the best experts on this subject based on the ideXlab platform.
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A ~565 Ma old glaciation in the Ediacaran of peri-Gondwanan West Africa
International Journal of Earth Sciences, 2018Co-Authors: Ulf Linnemann, Agustín Pieren Pidal, Kerstin Drost, Linda Marko, J. Zieger, Cecilio Quesada, Mandy Hofmann, Andreas Gartner, Axel Gerdes, Jens UlrichAbstract:In the Cadomian orogen of the NE Bohemian Massif and of SW Iberia, a post-Gaskiers glacial event dated at c. 565 Ma has been detected. Such Ediacaran-aged glaciomarine deposits occur in the Weesenstein and Clanzschwitz groups of the Saxo-Thuringian zone (Bohemia) and in the Lower Alcudian group of the southern Central Iberian zone (Iberia). Both areas are parts of Cadomia situated in the Western and Central European Variscides. Glaciomarine sedimentary rocks are characterized by such features as dropstones, flat iron-shaped pebbles (“ Bügeleisen - Geschiebe ”), facetted pebbles, dreikanters, and zircon grains affected by Ice Abrasion. For age and provenance determination, LA–ICP–MS U–Pb ages ( n = 1124) and Hf isotope ( n = 446) analyses were performed. The maximum age of the glaciomarine deposits within a Cadomian back-arc basin based on U–Pb analytics resulted in the youngest detrital zircon populations showing ages of 562–565 Ma and of c. 566–576 Ma old zircon derived from granitoid pebbles within the diamictites. The youngest age recorded was 538–540 Ma based on zircon from the plutons which had intruded the previously deformed Ediacaran metasedimentary rocks. Previously described glaciomarine diamictites of Cadomia (Weesenstein, Clanzschwitz, and Orellana diamictites) are most definitely younger than the c. 579–581 Ma Gaskiers glaciation in Newfoundland (Gaskiers) and in SE New England (Squantum). We propose the term Weesenstein – Orellana glaciation for this new Ediacaran glacial event, named after the most relevant regions of exposure. Palaeogeographically, these glaciomarine diamictites and related sedimentary deposits lie on the periphery of the West African Craton (western peri-Gondwana), and evidence has been provided by detrital zircon U–Pb ages and their Hf isotope composition. Correlation with similar glaciomarine deposits in the Anti-Atlas (Bou Azzer) and Saudi Arabia suggests a continued distribution of post-Gaskiers glacial deposits along the Gondwana margin of Northern Africa. The Weesenstein – Orellana glaciation correlates in part with the Shuram–Wonoka δ^13C anomaly.
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A ~565 Ma old glaciation in the Ediacaran of peri-Gondwanan West Africa
International Journal of Earth Sciences, 2018Co-Authors: Ulf Linnemann, Agustín Pieren Pidal, Kerstin Drost, Linda Marko, J. Zieger, Cecilio Quesada, Mandy Hofmann, Andreas Gartner, Axel Gerdes, Jens UlrichAbstract:In the Cadomian orogen of the NE Bohemian Massif and of SW Iberia, a post-Gaskiers glacial event dated at c. 565 Ma has been detected. Such Ediacaran-aged glaciomarine deposits occur in the Weesenstein and Clanzschwitz groups of the Saxo-Thuringian zone (Bohemia) and in the Lower Alcudian group of the southern Central Iberian zone (Iberia). Both areas are parts of Cadomia situated in the Western and Central European Variscides. Glaciomarine sedimentary rocks are characterized by such features as dropstones, flat iron-shaped pebbles (“ Bügeleisen - Geschiebe ”), facetted pebbles, dreikanters, and zircon grains affected by Ice Abrasion. For age and provenance determination, LA–ICP–MS U–Pb ages ( n = 1124) and Hf isotope ( n = 446) analyses were performed. The maximum age of the glaciomarine deposits within a Cadomian back-arc basin based on U–Pb analytics resulted in the youngest detrital zircon populations showing ages of 562–565 Ma and of c. 566–576 Ma old zircon derived from granitoid pebbles within the diamictites. The youngest age recorded was 538–540 Ma based on zircon from the plutons which had intruded the previously deformed Ediacaran metasedimentary rocks. Previously described glaciomarine diamictites of Cadomia (Weesenstein, Clanzschwitz, and Orellana diamictites) are most definitely younger than the c. 579–581 Ma Gaskiers glaciation in Newfoundland (Gaskiers) and in SE New England (Squantum). We propose the term Weesenstein – Orellana glaciation for this new Ediacaran glacial event, named after the most relevant regions of exposure. Palaeogeographically, these glaciomarine diamictites and related sedimentary deposits lie on the periphery of the West African Craton (western peri-Gondwana), and evidence has been provided by detrital zircon U–Pb ages and their Hf isotope composition. Correlation with similar glaciomarine deposits in the Anti-Atlas (Bou Azzer) and Saudi Arabia suggests a continued distribution of post-Gaskiers glacial deposits along the Gondwana margin of Northern Africa. The Weesenstein – Orellana glaciation correlates in part with the Shuram–Wonoka δ^13C anomaly.
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A ~565 Ma old glaciation in the Ediacaran of peri-Gondwanan West Africa
International Journal of Earth Sciences, 2017Co-Authors: Ulf Linnemann, Agustín Pieren Pidal, Kerstin Drost, Linda Marko, J. Zieger, Cecilio Quesada, Mandy Hofmann, Andreas Gartner, Axel Gerdes, Jens UlrichAbstract:In the Cadomian orogen of the NE Bohemian Massif and of SW Iberia, a post-Gaskiers glacial event dated at c. 565 Ma has been detected. Such Ediacaran-aged glaciomarine deposits occur in the Weesenstein and Clanzschwitz groups of the Saxo-Thuringian zone (Bohemia) and in the Lower Alcudian group of the southern Central Iberian zone (Iberia). Both areas are parts of Cadomia situated in the Western and Central European Variscides. Glaciomarine sedimentary rocks are characterized by such features as dropstones, flat iron-shaped pebbles (“Bugeleisen-Geschiebe”), facetted pebbles, dreikanters, and zircon grains affected by Ice Abrasion. For age and provenance determination, LA–ICP–MS U–Pb ages (n = 1124) and Hf isotope (n = 446) analyses were performed. The maximum age of the glaciomarine deposits within a Cadomian back-arc basin based on U–Pb analytics resulted in the youngest detrital zircon populations showing ages of 562–565 Ma and of c. 566–576 Ma old zircon derived from granitoid pebbles within the diamictites. The youngest age recorded was 538–540 Ma based on zircon from the plutons which had intruded the previously deformed Ediacaran metasedimentary rocks. Previously described glaciomarine diamictites of Cadomia (Weesenstein, Clanzschwitz, and Orellana diamictites) are most definitely younger than the c. 579–581 Ma Gaskiers glaciation in Newfoundland (Gaskiers) and in SE New England (Squantum). We propose the term Weesenstein–Orellana glaciation for this new Ediacaran glacial event, named after the most relevant regions of exposure. Palaeogeographically, these glaciomarine diamictites and related sedimentary deposits lie on the periphery of the West African Craton (western peri-Gondwana), and evidence has been provided by detrital zircon U–Pb ages and their Hf isotope composition. Correlation with similar glaciomarine deposits in the Anti-Atlas (Bou Azzer) and Saudi Arabia suggests a continued distribution of post-Gaskiers glacial deposits along the Gondwana margin of Northern Africa. The Weesenstein–Orellana glaciation correlates in part with the Shuram–Wonoka δ13C anomaly.
Ulf Linnemann - One of the best experts on this subject based on the ideXlab platform.
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A ~565 Ma old glaciation in the Ediacaran of peri-Gondwanan West Africa
International Journal of Earth Sciences, 2018Co-Authors: Ulf Linnemann, Agustín Pieren Pidal, Kerstin Drost, Linda Marko, J. Zieger, Cecilio Quesada, Mandy Hofmann, Andreas Gartner, Axel Gerdes, Jens UlrichAbstract:In the Cadomian orogen of the NE Bohemian Massif and of SW Iberia, a post-Gaskiers glacial event dated at c. 565 Ma has been detected. Such Ediacaran-aged glaciomarine deposits occur in the Weesenstein and Clanzschwitz groups of the Saxo-Thuringian zone (Bohemia) and in the Lower Alcudian group of the southern Central Iberian zone (Iberia). Both areas are parts of Cadomia situated in the Western and Central European Variscides. Glaciomarine sedimentary rocks are characterized by such features as dropstones, flat iron-shaped pebbles (“ Bügeleisen - Geschiebe ”), facetted pebbles, dreikanters, and zircon grains affected by Ice Abrasion. For age and provenance determination, LA–ICP–MS U–Pb ages ( n = 1124) and Hf isotope ( n = 446) analyses were performed. The maximum age of the glaciomarine deposits within a Cadomian back-arc basin based on U–Pb analytics resulted in the youngest detrital zircon populations showing ages of 562–565 Ma and of c. 566–576 Ma old zircon derived from granitoid pebbles within the diamictites. The youngest age recorded was 538–540 Ma based on zircon from the plutons which had intruded the previously deformed Ediacaran metasedimentary rocks. Previously described glaciomarine diamictites of Cadomia (Weesenstein, Clanzschwitz, and Orellana diamictites) are most definitely younger than the c. 579–581 Ma Gaskiers glaciation in Newfoundland (Gaskiers) and in SE New England (Squantum). We propose the term Weesenstein – Orellana glaciation for this new Ediacaran glacial event, named after the most relevant regions of exposure. Palaeogeographically, these glaciomarine diamictites and related sedimentary deposits lie on the periphery of the West African Craton (western peri-Gondwana), and evidence has been provided by detrital zircon U–Pb ages and their Hf isotope composition. Correlation with similar glaciomarine deposits in the Anti-Atlas (Bou Azzer) and Saudi Arabia suggests a continued distribution of post-Gaskiers glacial deposits along the Gondwana margin of Northern Africa. The Weesenstein – Orellana glaciation correlates in part with the Shuram–Wonoka δ^13C anomaly.
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A ~565 Ma old glaciation in the Ediacaran of peri-Gondwanan West Africa
International Journal of Earth Sciences, 2018Co-Authors: Ulf Linnemann, Agustín Pieren Pidal, Kerstin Drost, Linda Marko, J. Zieger, Cecilio Quesada, Mandy Hofmann, Andreas Gartner, Axel Gerdes, Jens UlrichAbstract:In the Cadomian orogen of the NE Bohemian Massif and of SW Iberia, a post-Gaskiers glacial event dated at c. 565 Ma has been detected. Such Ediacaran-aged glaciomarine deposits occur in the Weesenstein and Clanzschwitz groups of the Saxo-Thuringian zone (Bohemia) and in the Lower Alcudian group of the southern Central Iberian zone (Iberia). Both areas are parts of Cadomia situated in the Western and Central European Variscides. Glaciomarine sedimentary rocks are characterized by such features as dropstones, flat iron-shaped pebbles (“ Bügeleisen - Geschiebe ”), facetted pebbles, dreikanters, and zircon grains affected by Ice Abrasion. For age and provenance determination, LA–ICP–MS U–Pb ages ( n = 1124) and Hf isotope ( n = 446) analyses were performed. The maximum age of the glaciomarine deposits within a Cadomian back-arc basin based on U–Pb analytics resulted in the youngest detrital zircon populations showing ages of 562–565 Ma and of c. 566–576 Ma old zircon derived from granitoid pebbles within the diamictites. The youngest age recorded was 538–540 Ma based on zircon from the plutons which had intruded the previously deformed Ediacaran metasedimentary rocks. Previously described glaciomarine diamictites of Cadomia (Weesenstein, Clanzschwitz, and Orellana diamictites) are most definitely younger than the c. 579–581 Ma Gaskiers glaciation in Newfoundland (Gaskiers) and in SE New England (Squantum). We propose the term Weesenstein – Orellana glaciation for this new Ediacaran glacial event, named after the most relevant regions of exposure. Palaeogeographically, these glaciomarine diamictites and related sedimentary deposits lie on the periphery of the West African Craton (western peri-Gondwana), and evidence has been provided by detrital zircon U–Pb ages and their Hf isotope composition. Correlation with similar glaciomarine deposits in the Anti-Atlas (Bou Azzer) and Saudi Arabia suggests a continued distribution of post-Gaskiers glacial deposits along the Gondwana margin of Northern Africa. The Weesenstein – Orellana glaciation correlates in part with the Shuram–Wonoka δ^13C anomaly.
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A ~565 Ma old glaciation in the Ediacaran of peri-Gondwanan West Africa
International Journal of Earth Sciences, 2017Co-Authors: Ulf Linnemann, Agustín Pieren Pidal, Kerstin Drost, Linda Marko, J. Zieger, Cecilio Quesada, Mandy Hofmann, Andreas Gartner, Axel Gerdes, Jens UlrichAbstract:In the Cadomian orogen of the NE Bohemian Massif and of SW Iberia, a post-Gaskiers glacial event dated at c. 565 Ma has been detected. Such Ediacaran-aged glaciomarine deposits occur in the Weesenstein and Clanzschwitz groups of the Saxo-Thuringian zone (Bohemia) and in the Lower Alcudian group of the southern Central Iberian zone (Iberia). Both areas are parts of Cadomia situated in the Western and Central European Variscides. Glaciomarine sedimentary rocks are characterized by such features as dropstones, flat iron-shaped pebbles (“Bugeleisen-Geschiebe”), facetted pebbles, dreikanters, and zircon grains affected by Ice Abrasion. For age and provenance determination, LA–ICP–MS U–Pb ages (n = 1124) and Hf isotope (n = 446) analyses were performed. The maximum age of the glaciomarine deposits within a Cadomian back-arc basin based on U–Pb analytics resulted in the youngest detrital zircon populations showing ages of 562–565 Ma and of c. 566–576 Ma old zircon derived from granitoid pebbles within the diamictites. The youngest age recorded was 538–540 Ma based on zircon from the plutons which had intruded the previously deformed Ediacaran metasedimentary rocks. Previously described glaciomarine diamictites of Cadomia (Weesenstein, Clanzschwitz, and Orellana diamictites) are most definitely younger than the c. 579–581 Ma Gaskiers glaciation in Newfoundland (Gaskiers) and in SE New England (Squantum). We propose the term Weesenstein–Orellana glaciation for this new Ediacaran glacial event, named after the most relevant regions of exposure. Palaeogeographically, these glaciomarine diamictites and related sedimentary deposits lie on the periphery of the West African Craton (western peri-Gondwana), and evidence has been provided by detrital zircon U–Pb ages and their Hf isotope composition. Correlation with similar glaciomarine deposits in the Anti-Atlas (Bou Azzer) and Saudi Arabia suggests a continued distribution of post-Gaskiers glacial deposits along the Gondwana margin of Northern Africa. The Weesenstein–Orellana glaciation correlates in part with the Shuram–Wonoka δ13C anomaly.
Stefan Jacobsen - One of the best experts on this subject based on the ideXlab platform.
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Topography studies of concrete abraded with Ice
Wear, 2019Co-Authors: Guzel Shamsutdinova, Max A.n. Hendriks, Stefan JacobsenAbstract:Abstract Topography studies of concrete-Ice Abrasion were made to proceed in our understanding of the mechanisms of concrete wear by Ice on Arctic offshore structures. The effects on various initial surfaces of a B75 normal-weight concrete (smooth, rough, sawn) and on the sawn surface of a LB60 lightweight concrete were studied during concrete-Ice Abrasion experiments. The degradation of a concrete surface appears mainly as valley formation resulting from air voids opening, or aggregate protrusion and cutting of peaks. The various initial roughness conditions were found to lead to an evolution with both increasing (at both meso- and microscale) and converging roughness. Protrusions from both lightweight and normal-weight aggregates were observed on sawn surfaces. Greater Abrasion is seen on lightweight concrete and its initial roughness was much affected by the porous aggregate.
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Concrete-Ice Abrasion: Wear, coefficient of friction and Ice consumption
Wear, 2018Co-Authors: Guzel Shamsutdinova, Max A.n. Hendriks, Stefan JacobsenAbstract:Abstract Concrete structures in the Arctic offshore are often exposed to drifting Ice causing Abrasion of concrete surfaces. This paper presents the results of a laboratory study of concrete-Ice Abrasion. The sawn concrete surfaces (two high-performance concrete mixes and one light weight mix of concrete) were exposed to sliding fresh-water Ice under 1 MPa pressure for 3 km of sliding distance. The effect of concrete compressive strength, Ice consumption, and the coefficient of friction on Abrasion was studied simultaneously. The results show a low Abrasion of concrete, the maximum Abrasion depth (0.35 mm) after 3 km of sliding test was found for the concrete samples with the lowest compressive strength. All tests showed a severe-to-mild wear transition, with the maximum wear rate in the first sliding kilometre. The coefficient of friction was high when Ice consumption was high due to Ice spallation and pulverization, whereas the coefficient of friction was not directly correlated to the wear. The wear or consumption of the Ice (abrasive) was in the order of 30,000–100,000 times that of concrete despite of its strength and stiffness 1–10 times lower than that of concrete.
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LattIce Modelling of the Onset of Concrete-Ice Abrasion
Key Engineering Materials, 2016Co-Authors: N. Ramos, Guzel Shamsutdinova, Max A.n. Hendriks, Stefan JacobsenAbstract:The last decades the concrete-Ice Abrasion process has been well known as a concrete surface degradation mechanism due to Ice sliding. The topic is especially relevant for concrete gravity based structures in the Arctic offshore. The article presents a numerical model in which the onset of wear in the concrete-Ice Abrasion process is simulated. The simulations are performed on meso-scale, which means that concrete is modelled as a three-phase material in which paste, aggregates and the interface transition zone are distinguished. LattIce modelling is adopted for the numerical modeling. Hertzian contact theory which predicts excessive tensile stresses on the concrete surface due to sliding of Ice asperities is used as an analytical basis for the numerical model. It was concluded that such model is able to capture both surface and subsurface cracking in the concrete.
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concrete Ice Abrasion mechanics
Cement and Concrete Research, 2015Co-Authors: Stefan Jacobsen, George W. Scherer, Erland M. SchulsonAbstract:Abstract The mechanisms of Abrasion of concrete by Ice are investigated by review of lab and field studies, wear theory, fracture-, contact- and poromechanics. Experience indicates that Ice Abrasion does not require freeze/thaw cycles. Three distinct mechanisms may contribute to Abrasion damage of concrete: (1) asperities of Ice sliding on concrete can create tensile stresses sufficient to initiate cracks (with fatigue from repeated contacts playing an important role); (2) debris released from the surface of the concrete can act as sharp abrasive particles that enhance the damage as the Ice drags them along the surface; and (3) water forced into surface defects can create pressure that propagates cracks. Topics for further research and recommendations for minimizing Abrasion are suggested.
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Concrete Ice Abrasion rig and wear measurements
2015Co-Authors: Guzel Shamsutdinova, Paal B Rike, Max A.n. Hendriks, Stefan JacobsenAbstract:The wear of concrete material due to Ice movement is a challenge for offshore and coastal structures. Concrete surfaces exposed to moving Ice are subjected to wear at various rates depending on concrete and Ice properties. At NTNU, Department of Structural Engineering, concrete Ice Abrasion phenomena are studied both theoretically and experimentally. This paper describes the accelerated concrete Ice Abrasion rig which was comprehensively improved recently. Together with surface measurement equipment, it is believed that the new experimental facility will give new input for understanding of the underlying mechanisms of Ice Abrasion.
Andreas Gartner - One of the best experts on this subject based on the ideXlab platform.
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A ~565 Ma old glaciation in the Ediacaran of peri-Gondwanan West Africa
International Journal of Earth Sciences, 2018Co-Authors: Ulf Linnemann, Agustín Pieren Pidal, Kerstin Drost, Linda Marko, J. Zieger, Cecilio Quesada, Mandy Hofmann, Andreas Gartner, Axel Gerdes, Jens UlrichAbstract:In the Cadomian orogen of the NE Bohemian Massif and of SW Iberia, a post-Gaskiers glacial event dated at c. 565 Ma has been detected. Such Ediacaran-aged glaciomarine deposits occur in the Weesenstein and Clanzschwitz groups of the Saxo-Thuringian zone (Bohemia) and in the Lower Alcudian group of the southern Central Iberian zone (Iberia). Both areas are parts of Cadomia situated in the Western and Central European Variscides. Glaciomarine sedimentary rocks are characterized by such features as dropstones, flat iron-shaped pebbles (“ Bügeleisen - Geschiebe ”), facetted pebbles, dreikanters, and zircon grains affected by Ice Abrasion. For age and provenance determination, LA–ICP–MS U–Pb ages ( n = 1124) and Hf isotope ( n = 446) analyses were performed. The maximum age of the glaciomarine deposits within a Cadomian back-arc basin based on U–Pb analytics resulted in the youngest detrital zircon populations showing ages of 562–565 Ma and of c. 566–576 Ma old zircon derived from granitoid pebbles within the diamictites. The youngest age recorded was 538–540 Ma based on zircon from the plutons which had intruded the previously deformed Ediacaran metasedimentary rocks. Previously described glaciomarine diamictites of Cadomia (Weesenstein, Clanzschwitz, and Orellana diamictites) are most definitely younger than the c. 579–581 Ma Gaskiers glaciation in Newfoundland (Gaskiers) and in SE New England (Squantum). We propose the term Weesenstein – Orellana glaciation for this new Ediacaran glacial event, named after the most relevant regions of exposure. Palaeogeographically, these glaciomarine diamictites and related sedimentary deposits lie on the periphery of the West African Craton (western peri-Gondwana), and evidence has been provided by detrital zircon U–Pb ages and their Hf isotope composition. Correlation with similar glaciomarine deposits in the Anti-Atlas (Bou Azzer) and Saudi Arabia suggests a continued distribution of post-Gaskiers glacial deposits along the Gondwana margin of Northern Africa. The Weesenstein – Orellana glaciation correlates in part with the Shuram–Wonoka δ^13C anomaly.
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A ~565 Ma old glaciation in the Ediacaran of peri-Gondwanan West Africa
International Journal of Earth Sciences, 2018Co-Authors: Ulf Linnemann, Agustín Pieren Pidal, Kerstin Drost, Linda Marko, J. Zieger, Cecilio Quesada, Mandy Hofmann, Andreas Gartner, Axel Gerdes, Jens UlrichAbstract:In the Cadomian orogen of the NE Bohemian Massif and of SW Iberia, a post-Gaskiers glacial event dated at c. 565 Ma has been detected. Such Ediacaran-aged glaciomarine deposits occur in the Weesenstein and Clanzschwitz groups of the Saxo-Thuringian zone (Bohemia) and in the Lower Alcudian group of the southern Central Iberian zone (Iberia). Both areas are parts of Cadomia situated in the Western and Central European Variscides. Glaciomarine sedimentary rocks are characterized by such features as dropstones, flat iron-shaped pebbles (“ Bügeleisen - Geschiebe ”), facetted pebbles, dreikanters, and zircon grains affected by Ice Abrasion. For age and provenance determination, LA–ICP–MS U–Pb ages ( n = 1124) and Hf isotope ( n = 446) analyses were performed. The maximum age of the glaciomarine deposits within a Cadomian back-arc basin based on U–Pb analytics resulted in the youngest detrital zircon populations showing ages of 562–565 Ma and of c. 566–576 Ma old zircon derived from granitoid pebbles within the diamictites. The youngest age recorded was 538–540 Ma based on zircon from the plutons which had intruded the previously deformed Ediacaran metasedimentary rocks. Previously described glaciomarine diamictites of Cadomia (Weesenstein, Clanzschwitz, and Orellana diamictites) are most definitely younger than the c. 579–581 Ma Gaskiers glaciation in Newfoundland (Gaskiers) and in SE New England (Squantum). We propose the term Weesenstein – Orellana glaciation for this new Ediacaran glacial event, named after the most relevant regions of exposure. Palaeogeographically, these glaciomarine diamictites and related sedimentary deposits lie on the periphery of the West African Craton (western peri-Gondwana), and evidence has been provided by detrital zircon U–Pb ages and their Hf isotope composition. Correlation with similar glaciomarine deposits in the Anti-Atlas (Bou Azzer) and Saudi Arabia suggests a continued distribution of post-Gaskiers glacial deposits along the Gondwana margin of Northern Africa. The Weesenstein – Orellana glaciation correlates in part with the Shuram–Wonoka δ^13C anomaly.
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A ~565 Ma old glaciation in the Ediacaran of peri-Gondwanan West Africa
International Journal of Earth Sciences, 2017Co-Authors: Ulf Linnemann, Agustín Pieren Pidal, Kerstin Drost, Linda Marko, J. Zieger, Cecilio Quesada, Mandy Hofmann, Andreas Gartner, Axel Gerdes, Jens UlrichAbstract:In the Cadomian orogen of the NE Bohemian Massif and of SW Iberia, a post-Gaskiers glacial event dated at c. 565 Ma has been detected. Such Ediacaran-aged glaciomarine deposits occur in the Weesenstein and Clanzschwitz groups of the Saxo-Thuringian zone (Bohemia) and in the Lower Alcudian group of the southern Central Iberian zone (Iberia). Both areas are parts of Cadomia situated in the Western and Central European Variscides. Glaciomarine sedimentary rocks are characterized by such features as dropstones, flat iron-shaped pebbles (“Bugeleisen-Geschiebe”), facetted pebbles, dreikanters, and zircon grains affected by Ice Abrasion. For age and provenance determination, LA–ICP–MS U–Pb ages (n = 1124) and Hf isotope (n = 446) analyses were performed. The maximum age of the glaciomarine deposits within a Cadomian back-arc basin based on U–Pb analytics resulted in the youngest detrital zircon populations showing ages of 562–565 Ma and of c. 566–576 Ma old zircon derived from granitoid pebbles within the diamictites. The youngest age recorded was 538–540 Ma based on zircon from the plutons which had intruded the previously deformed Ediacaran metasedimentary rocks. Previously described glaciomarine diamictites of Cadomia (Weesenstein, Clanzschwitz, and Orellana diamictites) are most definitely younger than the c. 579–581 Ma Gaskiers glaciation in Newfoundland (Gaskiers) and in SE New England (Squantum). We propose the term Weesenstein–Orellana glaciation for this new Ediacaran glacial event, named after the most relevant regions of exposure. Palaeogeographically, these glaciomarine diamictites and related sedimentary deposits lie on the periphery of the West African Craton (western peri-Gondwana), and evidence has been provided by detrital zircon U–Pb ages and their Hf isotope composition. Correlation with similar glaciomarine deposits in the Anti-Atlas (Bou Azzer) and Saudi Arabia suggests a continued distribution of post-Gaskiers glacial deposits along the Gondwana margin of Northern Africa. The Weesenstein–Orellana glaciation correlates in part with the Shuram–Wonoka δ13C anomaly.
Axel Gerdes - One of the best experts on this subject based on the ideXlab platform.
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A ~565 Ma old glaciation in the Ediacaran of peri-Gondwanan West Africa
International Journal of Earth Sciences, 2018Co-Authors: Ulf Linnemann, Agustín Pieren Pidal, Kerstin Drost, Linda Marko, J. Zieger, Cecilio Quesada, Mandy Hofmann, Andreas Gartner, Axel Gerdes, Jens UlrichAbstract:In the Cadomian orogen of the NE Bohemian Massif and of SW Iberia, a post-Gaskiers glacial event dated at c. 565 Ma has been detected. Such Ediacaran-aged glaciomarine deposits occur in the Weesenstein and Clanzschwitz groups of the Saxo-Thuringian zone (Bohemia) and in the Lower Alcudian group of the southern Central Iberian zone (Iberia). Both areas are parts of Cadomia situated in the Western and Central European Variscides. Glaciomarine sedimentary rocks are characterized by such features as dropstones, flat iron-shaped pebbles (“ Bügeleisen - Geschiebe ”), facetted pebbles, dreikanters, and zircon grains affected by Ice Abrasion. For age and provenance determination, LA–ICP–MS U–Pb ages ( n = 1124) and Hf isotope ( n = 446) analyses were performed. The maximum age of the glaciomarine deposits within a Cadomian back-arc basin based on U–Pb analytics resulted in the youngest detrital zircon populations showing ages of 562–565 Ma and of c. 566–576 Ma old zircon derived from granitoid pebbles within the diamictites. The youngest age recorded was 538–540 Ma based on zircon from the plutons which had intruded the previously deformed Ediacaran metasedimentary rocks. Previously described glaciomarine diamictites of Cadomia (Weesenstein, Clanzschwitz, and Orellana diamictites) are most definitely younger than the c. 579–581 Ma Gaskiers glaciation in Newfoundland (Gaskiers) and in SE New England (Squantum). We propose the term Weesenstein – Orellana glaciation for this new Ediacaran glacial event, named after the most relevant regions of exposure. Palaeogeographically, these glaciomarine diamictites and related sedimentary deposits lie on the periphery of the West African Craton (western peri-Gondwana), and evidence has been provided by detrital zircon U–Pb ages and their Hf isotope composition. Correlation with similar glaciomarine deposits in the Anti-Atlas (Bou Azzer) and Saudi Arabia suggests a continued distribution of post-Gaskiers glacial deposits along the Gondwana margin of Northern Africa. The Weesenstein – Orellana glaciation correlates in part with the Shuram–Wonoka δ^13C anomaly.
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A ~565 Ma old glaciation in the Ediacaran of peri-Gondwanan West Africa
International Journal of Earth Sciences, 2018Co-Authors: Ulf Linnemann, Agustín Pieren Pidal, Kerstin Drost, Linda Marko, J. Zieger, Cecilio Quesada, Mandy Hofmann, Andreas Gartner, Axel Gerdes, Jens UlrichAbstract:In the Cadomian orogen of the NE Bohemian Massif and of SW Iberia, a post-Gaskiers glacial event dated at c. 565 Ma has been detected. Such Ediacaran-aged glaciomarine deposits occur in the Weesenstein and Clanzschwitz groups of the Saxo-Thuringian zone (Bohemia) and in the Lower Alcudian group of the southern Central Iberian zone (Iberia). Both areas are parts of Cadomia situated in the Western and Central European Variscides. Glaciomarine sedimentary rocks are characterized by such features as dropstones, flat iron-shaped pebbles (“ Bügeleisen - Geschiebe ”), facetted pebbles, dreikanters, and zircon grains affected by Ice Abrasion. For age and provenance determination, LA–ICP–MS U–Pb ages ( n = 1124) and Hf isotope ( n = 446) analyses were performed. The maximum age of the glaciomarine deposits within a Cadomian back-arc basin based on U–Pb analytics resulted in the youngest detrital zircon populations showing ages of 562–565 Ma and of c. 566–576 Ma old zircon derived from granitoid pebbles within the diamictites. The youngest age recorded was 538–540 Ma based on zircon from the plutons which had intruded the previously deformed Ediacaran metasedimentary rocks. Previously described glaciomarine diamictites of Cadomia (Weesenstein, Clanzschwitz, and Orellana diamictites) are most definitely younger than the c. 579–581 Ma Gaskiers glaciation in Newfoundland (Gaskiers) and in SE New England (Squantum). We propose the term Weesenstein – Orellana glaciation for this new Ediacaran glacial event, named after the most relevant regions of exposure. Palaeogeographically, these glaciomarine diamictites and related sedimentary deposits lie on the periphery of the West African Craton (western peri-Gondwana), and evidence has been provided by detrital zircon U–Pb ages and their Hf isotope composition. Correlation with similar glaciomarine deposits in the Anti-Atlas (Bou Azzer) and Saudi Arabia suggests a continued distribution of post-Gaskiers glacial deposits along the Gondwana margin of Northern Africa. The Weesenstein – Orellana glaciation correlates in part with the Shuram–Wonoka δ^13C anomaly.
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A ~565 Ma old glaciation in the Ediacaran of peri-Gondwanan West Africa
International Journal of Earth Sciences, 2017Co-Authors: Ulf Linnemann, Agustín Pieren Pidal, Kerstin Drost, Linda Marko, J. Zieger, Cecilio Quesada, Mandy Hofmann, Andreas Gartner, Axel Gerdes, Jens UlrichAbstract:In the Cadomian orogen of the NE Bohemian Massif and of SW Iberia, a post-Gaskiers glacial event dated at c. 565 Ma has been detected. Such Ediacaran-aged glaciomarine deposits occur in the Weesenstein and Clanzschwitz groups of the Saxo-Thuringian zone (Bohemia) and in the Lower Alcudian group of the southern Central Iberian zone (Iberia). Both areas are parts of Cadomia situated in the Western and Central European Variscides. Glaciomarine sedimentary rocks are characterized by such features as dropstones, flat iron-shaped pebbles (“Bugeleisen-Geschiebe”), facetted pebbles, dreikanters, and zircon grains affected by Ice Abrasion. For age and provenance determination, LA–ICP–MS U–Pb ages (n = 1124) and Hf isotope (n = 446) analyses were performed. The maximum age of the glaciomarine deposits within a Cadomian back-arc basin based on U–Pb analytics resulted in the youngest detrital zircon populations showing ages of 562–565 Ma and of c. 566–576 Ma old zircon derived from granitoid pebbles within the diamictites. The youngest age recorded was 538–540 Ma based on zircon from the plutons which had intruded the previously deformed Ediacaran metasedimentary rocks. Previously described glaciomarine diamictites of Cadomia (Weesenstein, Clanzschwitz, and Orellana diamictites) are most definitely younger than the c. 579–581 Ma Gaskiers glaciation in Newfoundland (Gaskiers) and in SE New England (Squantum). We propose the term Weesenstein–Orellana glaciation for this new Ediacaran glacial event, named after the most relevant regions of exposure. Palaeogeographically, these glaciomarine diamictites and related sedimentary deposits lie on the periphery of the West African Craton (western peri-Gondwana), and evidence has been provided by detrital zircon U–Pb ages and their Hf isotope composition. Correlation with similar glaciomarine deposits in the Anti-Atlas (Bou Azzer) and Saudi Arabia suggests a continued distribution of post-Gaskiers glacial deposits along the Gondwana margin of Northern Africa. The Weesenstein–Orellana glaciation correlates in part with the Shuram–Wonoka δ13C anomaly.