- ItemStructure and internal deformation of thrust sheets in the Sawtooth Range, Montana: insights from anisotropy of magnetic susceptibility(Geological Society of London, 2020-01) McCarthy, Dave J.; Meere, Patrick A.; Petronis, Michael S.; Irish Research Council for Science, Engineering and TechnologyGeological strain analysis of sedimentary rocks is commonly carried out using clast-based techniques. In the absence of valid strain markers, it can be difficult to identify the presence of an early tectonic fabric development and resulting layer parallel shortening (LPS). In order to identify early LPS, we carried out anisotropy of magnetic susceptibility (AMS) analyses on Mississippian limestones from the Sawtooth Range of Montana. The Sawtooth Range is an arcuate zone of north-trending, closely spaced, west-dipping, imbricate thrust sheets that place Mississippian Madison Group carbonates above Cretaceous shales and sandstones. This structural regime is part of the cordilleran mountain belt of North America, which resulted from accretion of allochthonous terrains to the western edge of the North American continent.Although the region has a general east-west increase in thrust displacement and related brittle deformation, a similar trend in penetrative deformation or the distribution of tectonic fabrics is not observed in the field or in the AMS results. The range of magnetic fabrics identified in each thrust sheet ranges from bedding controlled depositional fabrics to tectonic fabrics at a high angle to bedding.
- ItemDetermining finite strain: how far have we progressed?(Geological Society of London, 2020-01) McCarthy, Dave; Meere, Patrick A.; Mulchrone, Kieran; Bond, C. E.; Lebit, H. D.One of the main aims in the field of structural geology is the identification and quantification of deformation or strain. This pursuit has occupied geologists since the 1800s, but has evolved dramatically since those early studies. The quantification of strain in sedimentary lithologies was initially restricted to lithologies of known initial shape, such as fossils or reduction spots. In 1967, Ramsay presented a series of methods and calculations, which allowed populations of clasts to be used as strain markers. These methods acted as a foundation for modern strain analysis, and have influenced thousands of studies. This review highlights the significance of Ramsay's contribution to modern strain analysis. We outline the advances in the field over the 50 years since publication of Folding and Fracturing of Rocks, review the existing limitations of strain analysis methods and look to future developments.
- ItemPrivate groundwater supply management as a response to flooding events: Perceptions of Irish well owners(Springer Nature Switzerland AG, 2021-03-31) de Andrade, Luisa A.; McDowell, Cillian P.; O'Dwyer, Jean; O'Neill, Eoin; Mooney, Simon; Hynds, Paul D.Over 720,000 people in the Republic of Ireland rely on private groundwater resources (i.e. private wells) for daily consumption, and as these extractions are unregulated, users are solely responsible for managing/mitigating contamination risks to their supplies. However, low levels of exposure to appropriate guidance on well water protection and ongoing maintenance are not uncommon, particularly regarding responses to sporadic environmental threats, such as significant flooding. Despite this, very little is known regarding the factors leading to (or inhibiting) preparedness among groundwater-reliant individuals in the context of health threats triggered by flooding events. Accordingly, the purpose of this study is to bridge this knowledge gap and explore current behaviours, knowledge, risk perception, and experience relating to this issue in the Irish context. This was attempted via a combination of quantitative and qualitative methodologies, including a nation-wide online survey with 405 Irish well owners and six localized focus group meetings. Results show the need to go beyond knowledge-based interventions, and use socio-hydrogeological and/or socio-epidemiological approaches to target risk perception and potential structural constraints as a mean to turn protective intentions into protective actions when dealing with adverse effects of sporadic natural events, particularly in a changing climate.
- ItemWomen at the dawn of diamond discovery in Siberia or how two women discovered the Siberian diamond province(The Geological Society of London, 2020-07) Kiseeva, Ekaterina S.; Yuzmukhametov, Rishat N.; Natural Environment Research CouncilExploration for diamonds in the Soviet Union started in the 1940s, however it was not until the beginning of 1950s that the government acknowledged a strong need for locally mined diamonds. In this article, based on publications from Russian literature, we recount a story of two female geologists, Larisa Popugaeva and Natalia Sarsadskhih. Natalia was the head of the mineralogical laboratory who implemented a new methodology to search for mineral indicators of primary diamond deposits. Larisa was a young geologist who joined Natalia's team in 1953. The work of these women led to the discovery in 1954 of the first diamond deposit in the country – a kimberlite pipe “Zarnitsa”. In 1954 Natalia was unable to go into the field, therefore the discovery was made by Larisa. Credit for this discovery, however, was claimed by the higher officials from the Amakinskaya expedition, one of the largest diamond exploration organisations in the country. Multiple efforts to restore justice did not succeed, with Larisa only being awarded the title of the “Discoverer” in 1970, and Natalia not until 1990. This article provides a description of Larisa's and Natalia's life up until the discovery of Zarnitsa, and a few significant events after.
- ItemCO2-rich melts in Earth(Cambridge University Press, 2019-10) Yaxley, Gregory M.; Ghosh, Sujoy; Kiseeva, Ekaterina S.; Mallik, Ananya; Spandler, Carl; Thomson, Andrew R.; Walter, Michael J.; Orcutt, Beth N.; Daniel, Isabelle; Dasgupta, RajdeepThis chapter reviews the systematics of partial melting of mantle lithologies – like peridotite and eclogite – in the presence of carbon dioxide. It discusses the composition of mantle-derived magmas generated in the presence of carbon dioxide and whether magmas erupted on Earth’s surface resemble carbonated magmas from the mantle. It reviews how the production of carbon dioxide-rich magma in the mantle varies as a function of tectonic settings – beneath continents and oceans and in subduction zones – and time.