ALBERT

Description: 〈span〉〈div〉Abstract〈/div〉The Outer Hebridean islands of Scotland host a ∼200 km long fault zone that was active between 1100 and 250 Ma, during which a belt of fault rock several kilometres wide was created. The fault zone hosts crush breccias, phyllonite, mylonite and pseudotachylyte. The latter unit is frequently found in major fault zones and within meteorite impact structures. Although pseudotachylyte is widely believed to be a product of frictional melting within the fault zone, there is still controversy over the specific formational mechanisms. For this study pseudotachylyte was collected from the southern block of the Outer Hebrides Fault Zone. A recently developed geochemical mixing model was applied to reconstruct the geochemistry of the pseudotachylyte matrix using locally available lithologies. The results demonstrate that pseudotachylyte could be derived from local country rock, though some mixing was necessary to provide accurate reconstructions, suggesting a degree of mixing between melts derived from different protoliths. Petrographic observations identified additional characteristics of melt transportation, including transported clasts, aligned fragments, melt segregation, and injection of melt into tensile fractures. The latter likely served as the transport mechanism, drawing melt into low pressure, tensile structures that developed adjacent to the melt forming zones within the fault plane.〈strong〉Supplementary material:〈/strong〉〈a href="https://doi.org/10.6084/m9.figshare.c.4567931"〉https://doi.org/10.6084/m9.figshare.c.4567931〈/a〉〈/span〉

Description: 〈span〉〈div〉Abstract〈/div〉The ecological significance of ice-rafted dropstones in present-day glacial marine benthic environments has received considerable attention from ecologists, but similar studies based on the geological records of dropstones and associated fossils are rare. In this study, we report statistically significant co-occurrences of ice-rafted dropstones with brachiopod shells in multiple stratigraphic horizons at multiple sites from the Middle Permian Wandrawandian Siltstone of the southern Sydney Basin in southeastern Australia. We analysed the distribution patterns of both dropstones and brachiopod-dominated fossil assemblages by using a quadrat-based sampling method and spatial point pattern analysis. It was revealed that the co-occurrences of ice-rafted dropstones and brachiopod shells are not random; rather, they demonstrate statistically significant and stratigraphically recurring associations that are here interpreted to represent dropstone-associated, brachiopod-dominated palaeoecological communities. In these recurring palaeocommunities, the presence of ice-rafted dropstones is considered to have added habitat complexity and heterogeneity to the benthic environment, especially suited to the settlement of brachiopods. In addition, the sinking of dropstones, from floating ice masses through the water column to the silty seafloor, is interpreted to have enriched the nutrient and oxygen supply to the benthic environment, further aiding the flourishing and maintenance of a diverse and stable marine benthic fauna.〈strong〉Supplementary material:〈/strong〉 Original data collection (Supplementary material 1) and spatial point pattern analysis results of rest quadrats (Supplementary material 2) are available at 〈a href="https://doi.org/10.6084/m9.figshare.c.4101743"〉https://doi.org/10.6084/m9.figshare.c.4101743〈/a〉〈/span〉

Description: 〈span〉〈div〉Abstract〈/div〉Most British railway embankments were constructed between 120 and 180 years ago without the benefit of modern design and construction methods. This can result in undesirable load-deformation characteristics and consequent disruption to present-day railway operations, for which there is unprecedented demand. Annual rail passenger kilometres have approximately doubled in the last 20 years and freight has increased by 60% over the same period. Whereas elements such as rails or bridges can be refurbished or replaced to meet increasing demand, the same is not usually feasible for embankments. Development of techniques to assess embankment performance risks posed by operational capacity enhancements is therefore of increasing significance to railway geotechnical asset management. The two case studies presented in this paper demonstrate how geospatial analysis and data management techniques may be applied to this challenge at both strategic (regional or national) and tactical (site-specific) scales for embankments incorporating plastic clay fill. The case studies also demonstrate, in a world of ever more abundant data, the growing need for engineering geologists and geotechnical engineers to augment their traditional knowledge with comprehensive data management and geospatial analysis skills, these being essential for modern infrastructure asset management.〈strong〉Thematic collection:〈/strong〉 This article is part of the ‘Ground-related risk to transportation infrastructure’ collection available at: 〈a href="https://www.lyellcollection.org/cc/Ground-related-risk-to-transportation-infrastructure"〉https://www.lyellcollection.org/cc/Ground-related-risk-to-transportation-infrastructure〈/a〉〈/span〉

Description: 〈span〉〈div〉Abstract〈/div〉Most British railway embankments were constructed between 120 and 180 years ago without the benefit of modern design and construction methods. This can result in undesirable load-deformation characteristics and consequent disruption to present-day railway operations, for which there is unprecedented demand. Annual rail passenger kilometres have approximately doubled in the last 20 years and freight has increased by 60% over the same period. Whereas elements such as rails or bridges can be refurbished or replaced to meet increasing demand, the same is not usually feasible for embankments. Development of techniques to assess embankment performance risks posed by operational capacity enhancements is therefore of increasing significance to railway geotechnical asset management. The two case studies presented in this paper demonstrate how geospatial analysis and data management techniques may be applied to this challenge at both strategic (regional or national) and tactical (site-specific) scales for embankments incorporating plastic clay fill. The case studies also demonstrate, in a world of ever more abundant data, the growing need for engineering geologists and geotechnical engineers to augment their traditional knowledge with comprehensive data management and geospatial analysis skills, these being essential for modern infrastructure asset management.〈strong〉Thematic collection:〈/strong〉 This article is part of the ‘Ground-related risk to transportation infrastructure’ collection available at: 〈a href="https://www.lyellcollection.org/cc/Ground-related-risk-to-transportation-infrastructure"〉https://www.lyellcollection.org/cc/Ground-related-risk-to-transportation-infrastructure〈/a〉〈/span〉