ABSTRACT Granitoid batholiths dominated by felsic to intermediate compositions are commonly associated with mafic plutons and enclaves; however, the genetic relationship between the apparently coeval but compositionally dissimilar magmas is unclear. Here, we reviewed the age and lithogeochemical and Nd-Sr isotopic compositions of some classic plutonic rocks emplaced in the Northern Highlands, Grampian and Connemara terranes of the Caledonide orogen of Scotland and Ireland. The Northern Highlands terrane consists mostly of Neoproterozoic metasedimentary rocks of the Moine Supergroup and is located north of the Great Glen fault. The Grampian terrane also consists of Neoproterozoic metasedimentary rocks (Dalradian Supergroup) and is located south of the Great Glen fault in both Scotland and Ireland. Amphibolite-facies metasedimentary rocks in the Connemara terrane are correlated with the Dalradian Supergroup, and the terrane is bounded by splays of the Highland Boundary and Southern Uplands faults. These three terranes were intruded by Silurian–Devonian mafic and felsic to intermediate plutonic rocks that display field evidence for mingling and mixing and have a similar range (between ca. 437 and 370 Ma) in emplacement ages. This range implies they were intruded during and after the late Caledonian Scandian orogenic event that resulted from the mid- to late Silurian collision of amalgamated Avalonia and Baltica with Laurentia and the final closure of the Iapetus Ocean. Our review supports the contention that the Great Glen fault represents a major compositional boundary in the Silurian lithosphere. Felsic to intermediate plutons that occur north of the Great Glen fault are more enriched in light rare earth elements and Ba-Sr-K compared to those to the south. Isotopic compositions of these late Caledonian plutonic rocks on both sides of the Great Glen fault indicate that metasomatism and enrichment of the subcontinental lithospheric mantle beneath the Northern Highlands terrane occurred just prior to emplacement of late Caledonian plutons. Within the same terrane, mafic and felsic to intermediate rocks display similar trace-element and rare earth element concentrations compatible with models implying that fractionation of a mafic magma played an important role in generating the felsic to intermediate magmas. The onset of slab failure magmatism may have been diachronous along the length of the collision zone. If so, slab failure may have propagated laterally, possibly initiating where promontories collided.

Abstract Connemara Marble, a well-known distinctive decorative stone from the west of Ireland, is herein proposed as a Global Heritage Stone Resource. Connemara Marble is a sillimanite-grade ophicarbonate, dominated by dolomite and calcite with varying proportions of serpentine, diopside, forsterite, tremolite clinochlore and phlogopite. The marble displays intricate corrugated layers that range in colour from white through sepias to various shades of green. These features impart unique characteristics that set the marble apart from other ornamental stones. Characteristics reflect amphibolite-grade metamorphism of an impure siliceous dolomitic limestone during the Grampian orogeny (475–463 Ma). Olivine, diopside, tremolite along with calcite and dolomite were formed during the peak of metamorphism which was followed by a later pervasive hydrothermal metamorphism that led to the extensive growth of serpentine after olivine and diopside. It has been used since Neolithic times, but has been quarried and fashioned in Connemara since the eighteenth century, and widely utilized in buildings in Ireland and the UK, for cladding, banisters, columns and church fittings. Later in the late nineteenth and early twentieth centuries it was exported in large quantities to the USA for use in civic and educational buildings. Its many uses as an ornamental stone in the interiors of buildings and in Irish jewellery commands worldwide acclaim.

Abstract Peat is a highly compressible geological material whose time-dependent consolidation and rheological behaviour is determined by peat structure, degree of humification and hydraulic properties. This chapter reviews the engineering background to peat compression, describes the distribution of peat soils in the UK, provides examples of the hazards associated with compressible peat deposits and considers ways these hazards might be mitigated. Although some generalizations can be made about gross differences between broad peat types, no simple relationship exists between the magnitude and rate of compression of peat and loading. Based on examples described here, land failures resulting from peat compression are locally generated, but due to the sensitive nature of peat these can result in runaway failures that pose great risk. Understanding the geological hazards associated with compressible peat soils is challenging because peat is geotechnically highly variable and the mapped extent of peat in the UK is subject to considerable error due to inconsistencies in the definition of peat. Mitigating compression hazards in peat soils is therefore subject to considerable uncertainty; however, a combination of improved understanding of the properties of compressible peat, better mapping and land use zoning, and appropriate construction will help to mitigate risk.

Abstract The spatial and temporal complexities of flooding in karst terrains pose unique challenges in flood risk management. Lowland karst landscapes can be particularly susceptible to groundwater flooding due to a combination of low aquifer storage, high diffusivity and limited or absent surface drainage. Numerous notable groundwater flood events have been recorded in the Republic of Ireland throughout the twentieth century, but flooding during the winters of 2009 and 2015 was the most severe on record, causing widespread and prolonged disruption and damage to property and infrastructure. Effective flood risk management requires an understanding of the recharge, storage and transport mechanisms governing water movement across the landscape during flood conditions. Using information gathered from recent events, the main hydrological and geomorphological factors influencing flooding in these complex lowland karst groundwater systems are elucidated. Observed flood mechanisms included backwater flooding of sinks, high water levels in ephemerally flooded basins (turloughs), overtopping of depressions, and discharges from springs and resurgences. This paper addresses the need to improve our understanding of groundwater flooding in karst terrains to ensure efficient flood prevention and mitigation in the future, and thus helps to achieve the aims of the European Union Floods Directive.