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Wolf Uwe Reimold - One of the best experts on this subject based on the ideXlab platform.
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Digital Elevation Models of Shatter Cones
2018Co-Authors: D. Baratoux, Wolf Uwe Reimold, Sylvain Bouley, Lenka BaratouxAbstract:20 Digital Elevation Model of Shatter Cones Haughton Dome (1 model using Helicon Focus, 1 Model from Laser Scanning) Jebal Waqf as Suwwan (1 model using Helicon Focus, 1 Model from Laser Scanning) Gosses Bluff (4 models using Helicon Focus) Serra da Cangalhia (1 model from Laser Scanning) Rochechouart (2 models from Laser Scanning) Steinheim Basin (3 models from Laser Scanning) Vargeão Dome (1 model from Laser Scanning) Vista Alegre (1 model from Laser Scanning) Vredefort (4 models from Laser Scanning)
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Microcomputed tomography and shock microdeformation studies on Shatter Cones
Meteoritics & Planetary Science, 2016Co-Authors: Patrice Tristan Zaag, Wolf Uwe Reimold, Christy A. HipsleyAbstract:One of the aspects of impact cratering that are still not fully understood is the formation of Shatter Cones and related fracturing phenomena. Yet, Shatter Cones have been applied as an impact-diagnostic criterion for decades without the role of shock waves and target rock defects in their formation having been elucidated ever. We have tested the application of the nondestructive microcomputed tomography (μCT) method to visualize the interior of Shatter Cones in order to possibly resolve links between fracture patterns and Shatter cone surface features (striations and intervening “valleys”). Shatter-coned samples from different impact sites and in different lithologies were investigated for their μCT suitability, with a Shatter cone in sandstone from the Serra da Cangalha impact structure (Brazil) remaining as the most promising candidate because of the fracture resolution achieved. To validate the obtained CT data, the scanned specimen was cut into three orthogonal sets of thin sections. Scans with 13 μm resolution were obtained. μCT scans and microscopic analysis unraveled an orientation of subplanar fractures and related fluid inclusion trails, and planar fracture (PF) orientations in the interior of Shatter Cones. Planar deformation features (PDF) were observed predominantly near the Shatter cone surface. Previously undescribed varieties of feather features (FF), in the form of lamellae emanating from curviplanar and curved fractures, as well as an “arrowhead”-like FF development with microlamellae originating from both sides of a PF, were observed. The timing of Shatter cone formation was investigated by establishing temporal relations to the generation of various shock microscopic effects. Shatter Cones are, thus, generated post- or syn-formation of PF, FF, subplanar fractures, and PDF. The earliest possible time for Shatter cone formation is during the late stage of the compressional phase, that is, shock wave passage, of an impact event.
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The current state of knowledge about Shatter Cones: Introduction to the special issue
Meteoritics & Planetary Science, 2016Co-Authors: D. Baratoux, Wolf Uwe ReimoldAbstract:Shatter Cones are a fracture phenomenon that is exclusively associated with shock metamorphism and has also been produced in the laboratory in several shock experiments. The occurrence of Shatter Cones is the only accepted meso- to macroscopic recognition criterion for impact structures. Shatter Cones exhibit a number of geometric characteristics (orientation, apical angles, striation angles, sizes) that can be best described as varied, from case to case. Possible links between geometric properties with impact or crater parameters have remained controversial and the lack of understanding of the mechanism of formation of Shatter Cones does not offer a physical framework to discuss or understand them. A database of Shatter cone occurrences has been produced for this introduction paper to the special issue of Meteoritics and Planetary Science on Shatter Cones. Distribution of Shatter Cones with respect to crater size and lithology suggests that Shatter Cones do not occur in impact craters less than a few kilometers in diameter, with a few, currently questionable exceptions. All pertinent hypotheses of formation are presented and discussed. Several may be discarded in light of the most recent observations. The branching fracture mechanism and the interference models proposed, respectively, by Sagy et al. (2002) and Baratoux and Melosh (2003) require further evaluation. New observations, experiments, or theoretical considerations presented in this special issue promise an important step forward, based on a renewed effort to resolve the enigmatic origin of these important features.
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Shatter Cones at the Keurusselkä impact structure and their relation to local jointing
Meteoritics & Planetary Science, 2016Co-Authors: Maximilian Hasch, Wolf Uwe Reimold, Ulli Raschke, Patrice Tristan ZaagAbstract:Shatter Cones are the only distinct meso- to macroscopic recognition criterion for impact structures, yet not all is known about their formation. The Keurusselka impact structure, Finland, is interesting in that it presents a multitude of well-exposed Shatter Cones in medium- to coarse-grained granitoids. The allegedly 27 km wide Keurusselka impact structure was formed about 1150 Ma ago in rocks of the Central Finland Granitoid Complex. Special attention was paid in this work to possible relationships between Shatter Cones and local, as well as regionally occurring, fracture or joint systems. A possible Shatter cone find outside the previously suggested edge of the structure could mean that the Keurusselka impact structure is larger than previously thought. The spacing between joints/fractures from regional joint systems was influenced by the impact, but impact-induced fractures strongly follow the regional joint orientation trends. There is a distinct relationship between Shatter Cones and joints: Shatter Cones occur on and against joint surfaces of varied orientations and belonging to the regional orientation trends. Planar fractures (PF) and planar deformation features (PDF) were found in three Shatter cone samples from the central-most part of the impact structure, whereas other country rock samples from the same level of exposure but further from the assumed center lack shock deformation features. PDF occurrence is enhanced within 5 mm of Shatter cone surfaces, which is interpreted to suggest that shock wave reverberation at preimpact joints could be responsible for this local enhancement of shock deformation. Some Shatter cone surfaces are coated with a quasi-opaque material which is also found in conspicuous veinlets that branch off from Shatter cone surfaces and resemble pseudotachylitic breccia veins. The vein-filling is composed of two mineral phases, one of which could be identified as a montmorillonitic phyllosilicate. The second phase could not be identified yet. The original composition of the fill could not be determined. Further work is required on this material. Observed joints and fractures were discussed against findings from Barringer impact crater. They show that impact-induced joints in the basement rock do not follow impact-specific orientations (such as radial, conical, or concentric).
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The Agoudal (High Atlas Mountains, Morocco) Shatter cone conundrum: A recent meteorite fall onto the remnant of an impact site
Meteoritics & Planetary Science, 2016Co-Authors: Hasnaa Chennaoui Aoudjehane, Wolf Uwe Reimold, D. Baratoux, Christian Koeberl, Sylvain Bouley, Houda El Kerni, Mohamed AoudjehaneAbstract:Associations between impact structures and meteorite occurrences are rare and restricted to very young structures. Meteorite fragments are often disrupted in the atmosphere, and in most cases, meteorite falls that have been decelerated by atmospheric drag do not form a crater. Furthermore, meteorites are rapidly weathered. In this context, the finding of Shatter Cones in Jurassic marly limestone in the same location as a recent (105 ± 40 ka) iron meteorite fall near the village of Agoudal (High Atlas Mountains, Morocco) is enigmatic. The Shatter Cones are the only piece of evidence of a meteorite impact in the area. The overlap of a meteorite strewn field with the area of occurrence of Shatter Cones led previous researchers to consider that the meteorite fall was responsible for the formation of Shatter Cones in the context of formation of one or several small (
C. Champollion - One of the best experts on this subject based on the ideXlab platform.
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Geophysical signature of the Tunnunik impact structure, Northwest Territories, Canada
Meteoritics and Planetary Science, 2020Co-Authors: Y. Quesnel, W. Zylberman, P. Rochette, Minoru Uehara, Jerome Gattacceca, G. Osinski, P. Dussouillez, C. Lepaulard, C. ChampollionAbstract:In 2011, the discovery of Shatter Cones confirmed the 28 km-diameter Tunnunik complex impact structure, Northwest Territories, Canada. This study presents the first results of ground-based electromagnetic, gravimetric and magnetic surveys over this impact structure. Its central area is characterized by a ~10 km wide negative gravity anomaly of about 3 mGal amplitude, roughly corresponding to the area of Shatter Cones, and associated with a positive magnetic field anomaly of ~120 nT amplitude and 3 km wavelength. The latter correlates well with the location of the deepest uplifted strata, an impact-tilted Proterozoic dolomite layer of the Shaler Supergroup exposed near the center of the structure and intruded by dolerite dykes. Locally, electromagnetic field data unveil a conductive superficial formation which corresponds to an 80-100 m thick sand layer covering the impact structure. Based on measurements of magnetic properties of rock samples, we model the source of the magnetic anomaly as the magnetic sediments of the Shaler Supergroup combined with a core of uplifted crystalline basement with enhanced magnetization. More classically, the low gravity signature is attributed to a reduction in density measured on the brecciated target rocks and to the isolated sand formations. However, the present-day fractured zone does not extend deeper than ~1 km in our model, indicating a possible 1.5 km of erosion since the time of impact, about 430 Ma ago.
Elmar Buchner - One of the best experts on this subject based on the ideXlab platform.
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An approach towards the projectile trajectory during the oblique Steinheim meteorite impact by the interpretation of structural crater features and the distribution of Shatter Cones
Geological Magazine, 2017Co-Authors: Elmar BuchnerAbstract:AbstractThe distinct alignment of the Steinheim Basin and the Nördlinger Ries impact structures in SW Germany and the Central European tektite strewn field suggest ENE-directed trajectories of the Ries and Steinheim impacting bodies. From impact experiments, the asymmetry of the Steinheim crater and the arrangement of structural features therein are in good agreement with features produced during an oblique impact at 30° from the horizontal. The restriction of Shatter Cones to the eastern segment of the Steinheim Basin crater also suggests a west–east-directed trend of the impact direction, and supports previous models that favoured such impactor trajectory.
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Rare metals on Shatter cone surfaces from the Steinheim Basin (SW Germany) – remnants of the impacting body?
Geological Magazine, 2017Co-Authors: Elmar Buchner, Martin SchmiederAbstract:The ~3.8 km Steinheim Basin in SW Germany is a well-preserved complex impact structure characterized by a prominent central uplift and well-developed Shatter Cones that occur in different shocked target lithologies. Scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy and electron probe microanalysis have revealed, for the first time, the occurrence of rare metals on the Steinheim Shatter cone surfaces. Shatter Cones produced from the Middle Jurassic (Aalenian) Opalinus Claystone (‘Opalinuston’), temporarily exposed in the central uplift in spring 2010, and Shatter Cones in Upper Jurassic (Oxfordian) limestones from the southeastern crater rim domain are commonly covered by faint coatings. The Opalinus Claystone Shatter cone surfaces carry coatings dominated by Fe, Ca, P, S and Al, and are covered by abundant small, finely dispersed microparticles and aggregates of native gold, as well as locally elevated concentrations of Pt. On several surfaces of the claystone Shatter Cones, additional Fe, Ni and Co was detected. The Ca–Mn-rich coatings on the limestone Shatter cone surfaces locally include patches of Fe, Ni, Co, Cu and Au in variable amounts and proportions. The intriguing coatings on the Steinheim Shatter Cones could either stem from the impacted Lower Jurassic to Palaeogene sedimentary target rocks; from the crystalline-metamorphic Variscan crater basement; or, alternatively, these coatings might represent altered meteoritic matter from the Steinheim impactor, possibly an iron meteorite, which may have been remobilized during post-impact hydrothermal activity. We here discuss the most plausible source for the rare metals found adherent to the Shatter cone surfaces.
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Comment on “Some observations facing the interpretation of Waqf as Suwwan structure, SE desert of Jordan, as an impact crater”, by A. M. Abed et al. (2014), Arab J Geosci
Arabian Journal of Geosciences, 2015Co-Authors: Martin Schmieder, Elmar Buchner, Elias Salameh, Hani KhouryAbstract:In their recent article, Abed et al. (Arab J Geosci DOI: 10.1007/s12517-014-1427-6, 2014 ) critically address the impact nature of the ∼6 km Jebel Waqf as Suwwan impact structure in eastern Jordan. We here comment on several statements the authors make in their study. Altogether, the presence of a very typical impact crater structure and morphology, well-developed Shatter Cones in situ, and planar fractures in combination with feather features and transmission electron microscopy (TEM)-verified planar deformation features (PDF) in quartz collectively fulfills several shock metamorphic criteria that convincingly characterize the Jebel Waqf as Suwwan structure as a complex meteorite impact structure well accessible for geologic study.
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Meteorite traces on a Shatter cone surface from the Agoudal impact site, Morocco
Geological Magazine, 2015Co-Authors: Martin Schmieder, Elmar Buchner, H. Chennaoui Aoudjehane, Eric TohverAbstract:The recently discovered Agoudal impact site in Morocco is a small, eroded impact structure with well-developed Shatter Cones. A scanning electron microscopic study of a Shatter cone surface has revealed the presence of schreibersite – a phosphide very rare on Earth but common in iron meteorites – and Fe–Ni oxides. This is the first reported evidence for primary meteoritic matter adherent to Shatter Cones and suggests that the Agoudal crater was formed by the impact of an iron meteorite, probably the Agoudal IIAB iron. Shatter Cones from other terrestrial impact structures might also hold valuable information about the nature of the impacting projectiles.
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New Insights into the Steinheim Central Uplift - Part I: Shatter Cones in Claystone Lithologies (`Opalinuston', Middle Jurassic)
2010Co-Authors: Elmar Buchner, Martin SchmiederAbstract:Introduction: The ~3.8 km Steinheim Basin in SW Germany is a complex impact crater with central uplift hosted by a sequence of Triassic to Jurassic sedimentary rocks. The sedimentary rocks of the crater floor, as well as the intensely brecciated blocks that form the crater rim, consist of Upper Jurassic limestones. Findings of Shatter Cones were so far restricted to micritic Upper Jurassic limestones at the rim of the Steinheim Basin. Middle Jurassic sandstones and claystones crop out on top of the Steinheim central uplift. The construction of a water catchment on the central peak actually provides new insights into this Middle Jurassic sedimentary suite affected by the impact. New Observations: Shatter Cones in micritic Upper Jurassic limestones are well-known from the Steinheim impact structure. In addition, we here newly report Shatter Cones in fine-grained sandstones (Middle Jurassic ‘Eisensandstein’), as well as in up to dm-sized concretionary claystone nodules of the underlying Middle Jurassic ‘Opalinuston’ claystone that build up the central uplift. Shatter Cones are well-defined (up to ~5 cm in length; Fig. 1) and show variable orientations [1].
Martin Schmieder - One of the best experts on this subject based on the ideXlab platform.
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Rare metals on Shatter cone surfaces from the Steinheim Basin (SW Germany) – remnants of the impacting body?
Geological Magazine, 2017Co-Authors: Elmar Buchner, Martin SchmiederAbstract:The ~3.8 km Steinheim Basin in SW Germany is a well-preserved complex impact structure characterized by a prominent central uplift and well-developed Shatter Cones that occur in different shocked target lithologies. Scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy and electron probe microanalysis have revealed, for the first time, the occurrence of rare metals on the Steinheim Shatter cone surfaces. Shatter Cones produced from the Middle Jurassic (Aalenian) Opalinus Claystone (‘Opalinuston’), temporarily exposed in the central uplift in spring 2010, and Shatter Cones in Upper Jurassic (Oxfordian) limestones from the southeastern crater rim domain are commonly covered by faint coatings. The Opalinus Claystone Shatter cone surfaces carry coatings dominated by Fe, Ca, P, S and Al, and are covered by abundant small, finely dispersed microparticles and aggregates of native gold, as well as locally elevated concentrations of Pt. On several surfaces of the claystone Shatter Cones, additional Fe, Ni and Co was detected. The Ca–Mn-rich coatings on the limestone Shatter cone surfaces locally include patches of Fe, Ni, Co, Cu and Au in variable amounts and proportions. The intriguing coatings on the Steinheim Shatter Cones could either stem from the impacted Lower Jurassic to Palaeogene sedimentary target rocks; from the crystalline-metamorphic Variscan crater basement; or, alternatively, these coatings might represent altered meteoritic matter from the Steinheim impactor, possibly an iron meteorite, which may have been remobilized during post-impact hydrothermal activity. We here discuss the most plausible source for the rare metals found adherent to the Shatter cone surfaces.
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Comment on “Some observations facing the interpretation of Waqf as Suwwan structure, SE desert of Jordan, as an impact crater”, by A. M. Abed et al. (2014), Arab J Geosci
Arabian Journal of Geosciences, 2015Co-Authors: Martin Schmieder, Elmar Buchner, Elias Salameh, Hani KhouryAbstract:In their recent article, Abed et al. (Arab J Geosci DOI: 10.1007/s12517-014-1427-6, 2014 ) critically address the impact nature of the ∼6 km Jebel Waqf as Suwwan impact structure in eastern Jordan. We here comment on several statements the authors make in their study. Altogether, the presence of a very typical impact crater structure and morphology, well-developed Shatter Cones in situ, and planar fractures in combination with feather features and transmission electron microscopy (TEM)-verified planar deformation features (PDF) in quartz collectively fulfills several shock metamorphic criteria that convincingly characterize the Jebel Waqf as Suwwan structure as a complex meteorite impact structure well accessible for geologic study.
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Meteorite traces on a Shatter cone surface from the Agoudal impact site, Morocco
Geological Magazine, 2015Co-Authors: Martin Schmieder, Elmar Buchner, H. Chennaoui Aoudjehane, Eric TohverAbstract:The recently discovered Agoudal impact site in Morocco is a small, eroded impact structure with well-developed Shatter Cones. A scanning electron microscopic study of a Shatter cone surface has revealed the presence of schreibersite – a phosphide very rare on Earth but common in iron meteorites – and Fe–Ni oxides. This is the first reported evidence for primary meteoritic matter adherent to Shatter Cones and suggests that the Agoudal crater was formed by the impact of an iron meteorite, probably the Agoudal IIAB iron. Shatter Cones from other terrestrial impact structures might also hold valuable information about the nature of the impacting projectiles.
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New Insights into the Steinheim Central Uplift - Part I: Shatter Cones in Claystone Lithologies (`Opalinuston', Middle Jurassic)
2010Co-Authors: Elmar Buchner, Martin SchmiederAbstract:Introduction: The ~3.8 km Steinheim Basin in SW Germany is a complex impact crater with central uplift hosted by a sequence of Triassic to Jurassic sedimentary rocks. The sedimentary rocks of the crater floor, as well as the intensely brecciated blocks that form the crater rim, consist of Upper Jurassic limestones. Findings of Shatter Cones were so far restricted to micritic Upper Jurassic limestones at the rim of the Steinheim Basin. Middle Jurassic sandstones and claystones crop out on top of the Steinheim central uplift. The construction of a water catchment on the central peak actually provides new insights into this Middle Jurassic sedimentary suite affected by the impact. New Observations: Shatter Cones in micritic Upper Jurassic limestones are well-known from the Steinheim impact structure. In addition, we here newly report Shatter Cones in fine-grained sandstones (Middle Jurassic ‘Eisensandstein’), as well as in up to dm-sized concretionary claystone nodules of the underlying Middle Jurassic ‘Opalinuston’ claystone that build up the central uplift. Shatter Cones are well-defined (up to ~5 cm in length; Fig. 1) and show variable orientations [1].
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NEW INSIGHTS INTO THE STEINHEIM CENTRAL UPLIFT - PART I: Shatter Cones IN CLAYSTONE
2010Co-Authors: Elmar Buchner, Martin SchmiederAbstract:The ~3.8 km Steinheim Basin in SW Germany is a complex impact crater with central uplift hosted by a se-quence of Triassic to Jurassic sedimentary rocks. The sedimen-tary rocks of the crater floor, as well as the intensely brecciated blocks that form the crater rim, consist of Upper Jurassic lime-stones. Findings of Shatter Cones were so far restricted to micritic Upper Jurassic limestones at the rim of the Steinheim Basin. Middle Jurassic sandstones and claystones crop out on top of the Steinheim central uplift. The construction of a water catchment on the central peak actually provides new insights into this Mid-dle Jurassic sedimentary suite affected by the impact.
Y. Quesnel - One of the best experts on this subject based on the ideXlab platform.
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Geophysical signature of the Tunnunik impact structure, Northwest Territories, Canada
Meteoritics and Planetary Science, 2020Co-Authors: Y. Quesnel, W. Zylberman, P. Rochette, Minoru Uehara, Jerome Gattacceca, G. Osinski, P. Dussouillez, C. Lepaulard, C. ChampollionAbstract:In 2011, the discovery of Shatter Cones confirmed the 28 km-diameter Tunnunik complex impact structure, Northwest Territories, Canada. This study presents the first results of ground-based electromagnetic, gravimetric and magnetic surveys over this impact structure. Its central area is characterized by a ~10 km wide negative gravity anomaly of about 3 mGal amplitude, roughly corresponding to the area of Shatter Cones, and associated with a positive magnetic field anomaly of ~120 nT amplitude and 3 km wavelength. The latter correlates well with the location of the deepest uplifted strata, an impact-tilted Proterozoic dolomite layer of the Shaler Supergroup exposed near the center of the structure and intruded by dolerite dykes. Locally, electromagnetic field data unveil a conductive superficial formation which corresponds to an 80-100 m thick sand layer covering the impact structure. Based on measurements of magnetic properties of rock samples, we model the source of the magnetic anomaly as the magnetic sediments of the Shaler Supergroup combined with a core of uplifted crystalline basement with enhanced magnetization. More classically, the low gravity signature is attributed to a reduction in density measured on the brecciated target rocks and to the isolated sand formations. However, the present-day fractured zone does not extend deeper than ~1 km in our model, indicating a possible 1.5 km of erosion since the time of impact, about 430 Ma ago.