Tectonic significance of Late Paleozoic deformation in the Cape George Peninsula, Antigonish Highlands, Nova Scotia

Late Paleozoic deformation of the Cape George Peninsula, Antigonish Highlands, Nova Scotia, provides information on post-accretionary fault movements associated with waning stages of Appalachian orogenic activity. Anomalously intense brittle to ductile deformation of the low-grade Late Paleozoic rocks of the peninsula occurred along east-west shear zones in a ca. 4 km-wide belt bounded by the NE-trending Hollow and Greendale faults. Deformation adjacent to, and between, these two faults resulted in brecciation, folding and thrusting, the development of slickensides on major dislocation surfaces, the local development of S-C fabrics and stretching lineations defined by elongate pebbles, and/or the production of extensional fractures and veins. The data suggest dextral and subordinate thrust components of movement along the east-west shear zones. Deformation is attributed to dextrally oblique compression between the bounding Hollow and Greendale faults along which significant reverse displacements are proposed on the basis of fault geometry and kinematics. The Cape George Peninsula is interpreted as a "popup" structure between these back-to-back oblique-slip reverse faults and is considered to occupy a strongly transpressive step-over zone between them. The east-west shear zones, which record dextral transpressive motion and steepen towards the north in a positive half-flower structure configuration, are parallel to Reidel R-shears of the shear fracture array and are interpreted to be transfer faults within the step-over zone along which oblique slip with dextral and reverse components of motion was transferred from the Hollow Fault to the Greendale Fault. Development of the regional stress regime required by these fault kinematics is consistent with coeval post-accretionary dextral motion between the Meguma and Avalon composite terranes along the east-west Cobcquid-Chedabucto fault system. RÉSUMÉ La déformation du Paléozoique tandif de la péninsule dc Cap George, dans les hautes terres d'Antigonish en Nouvelle-Écosse, fournit des informations sur les mouvements de failles post-accrétionaires associés aux stades terminaux de l'activité orogénique appalachienne. Une déformation fragile à ductile anormalement intense des roches du Paléozoique supérieur de faible grade s'est produite le long de zones de cisaillement est-ouest dans une ceinture d'environ 4 km de largeur limited par les failles de Hollow et de Greendale d'orientation nord-est. La déformation adjacente et entre ces failles a résulté en de la bélchification, du plissement et du chevauchement, le développement de slickensides sur des surfaces de dislocation majeures, le développement local de fabriques C-S et de linéations d'étirement définies par des cailloux allongés, et/ou la production de fractures et de veines d'extension. Les données suggèrent des composantes de mouvement dextres et, dans une moindre mesure, de chevauchement le long des zones de cisaillement est-ouest. La déformation est attributée à une compression dextre oblique entre les failles limitrophes de Hollow et de Greendale le long desquelles des deplacements inverses importants sont proposés sur la base de la géométrie et de la cinémalique des failles. La péninsule de Cap George est interprét6e comme une structure d'extrusion verticale entre ces deux failles obliques a mouvement inverse, dos à dos, et est considérée comme occupant une zone de recouvrement fortement transpressive entre elles. Les zones de cisaillement est-ouest, qui montrent un mouvement de transpression dextre et deviennent plus abruples vers le nord en une configuration de demie "flower structure" positive, sont parallèles aux riedels synlhétiques du réseau de fractures de cisaillement et sont interprétées comme étant des failles de transfert à l'intérieur de la zone de transfert suivant lesquelles un mouvement oblique avec des composantes de mouvement dextre et inverse furent transferées de la faille de Hollow à la faille de Greendale. Le développement du régime de contrainte régional requis par ces cindmatiques de failles est en accord avec un mouvement post-accrétionaire dextre entre les terrains de Meguma et d'Avalon composite le long du systeme de faille est-ouest de Cobcquid-Chedabucto. [Traduit par la rédaction

BGS Karst Report Series: P1. Karst in the northern outcrop of Permian limestones

This report documents the evidence for karst and rapid groundwater flow in the northern outcrop of the Permian dolomitic limestones and their associated gypsum sequences in County Durham and a small part of North Yorkshire, in northern England. It is part of the BGS karst report series on those karst aquifers in England in which cave development is limited – principally the Upper Cretaceous Chalk and the Jurassic and Permian limestones. The term “karst” applies to rocks that are soluble. In classic karst there are extensive caves and large-scale surface karst landforms such as dolines, shafts, stream/river sinks, and springs. In the past, the Chalk and the Jurassic and Permian limestones of England were not considered karstic because they have limited cave development, and because karst features are usually small and have not been well documented. The reports provide data and information on karst in each area. There is clear evidence for karstic development in the Permian dolomitic limestones in the P1 area. Some short caves occur which appear to be fully or partially karstic in origin, and although they are now predominantly dry, they demonstrate that cave sized voids can develop in the limestones. Other caves and voids related to mass-movement are also present. There are also smaller karstic conduits, solutional fissures, dolines, dissolution pipes, stream sinks and springs present. However, there are no comprehensive datasets on these features and information on their frequency, distributions and characteristics is generally scarce. There is some further evidence that karstic networks of solutional fissures and conduits occur in the saturated zone, with some high transmissivities and yields, and large fissure inflows during construction. Both the unsaturated and saturated zones of the aquifer are impacted by karst, with a proportion of rapid recharge via surface karst features and solutional fissures, as well as some saturated zone networks of solutional conduits and fissures. These networks are likely to result in groundwater flow in unexpected directions and potentially over long distances. Considerable further work is needed to develop better datasets on karst features, and to assess the role of karst in the limestones in this area. There is more information on gypsum karst in the area, which is well-developed and poses significant engineering hazards and challenges, and also impacts on the limestones which collapse into the gypsum karst. The presence of sulphate-rich groundwater and springs indicate the interconnection of limestone and gypsum sequences in the Permian strata in the area, highlighting the complexity and connectivity between different geologies

BGS karst report series : P2. Karst in the southern outcrop of Permian limestones (and associated gypsum)

This report documents the evidence for karst and rapid groundwater flow in the southern outcrop of the Permian limestones in Northern England, together with the associated gypsum karst. It is part of the BGS karst report series on those karst aquifers in England in which cave development is limited – principally the Upper Cretaceous Chalk and the Jurassic and Permian limestones. The term “karst” applies to rocks that are soluble. In classic karst there are extensive caves and large-scale surface karst landforms such as dolines, shafts, stream/river sinks, and springs. In the past, the Chalk and the Jurassic and Permian limestones of England were not considered karstic because they have limited cave development, and because karst features are usually small and have not been well documented. These reports provide data and information on karst in each area. The Permian dolomitic limestones comprise the Cadeby Formation and the Brotherton Formation. These formations are separated by the Edlington Formation and overlain by the Roxby Formation, both of which contain extensive evaporite karst (in gypsum and anhydrite) interspersed with low permeability mudstones penetrated by karstic collapse features. This report is primarily focused on the dolomitic limestone karst, but the variable geology results in high complexity with interactions between the limestone and evaporite karst. Karst in the Permian gypsum associated with the limestones has not been well-recognised in hydrogeological studies. Evaporite karst in the area is well developed and documented with caves, dolines, and dissolution pipes. Collapse features extend into the limestones, especially in the Brotherton Formation, and there is evidence of groundwater connectivity between the evaporite and limestone karst, for example with sulphate-rich groundwater in the limestones and overlying strata. The gypsum sequences in contact with the limestones result in locally very high transmissivities and mixing of waters from the two types of karstified rocks. There is also clear evidence for karstification within the dolomitic limestones. Quite large, although short and dry, dolomitic limestone caves occur in the Cadeby Formation, with 21 karst caves recorded, ranging from 2.5 to 290 m in length. There is also evidence that smaller solutional conduits and fissures occur in the limestones which are likely to be an important component of groundwater flow. There are many other caves, some of which are formed by mass movement (slip rift caves) and some for which it is unclear whether they are mass movement caves or karst caves. In some instances, slip rift caves form a focus for recharge to the limestones, but many may be largely dry. There are significant karst stream sinks into the Cadeby Formation at Wadworth Wood near Doncaster and near Darrington, and a major karst river sink into the Cadeby Formation on the River Skell. Some limestone dolines and dissolution pipes have been recorded in the Cadeby and Brotherton formations. There are large numbers of springs in the Permian limestones, and although their flows and characteristics are generally not well documented, it appears that many are quite small, and a few may have substantial flows. Tracer tests have been carried out at one location, and these demonstrated connectivity between a groundwater abstraction and both a leaking sewer and a surface water course, over distances of 10s to 100s metres. At this locality high transmissivity, and high yields (> 80 l/s) also indicate solutional development of permeability. There are other abstractions in the P2 area with high yields and transmissivities of > 1000 m2/day suggesting they may be supplied by karstic solutional networks. Detailed borehole investigations using slug tests and water level monitoring have revealed rapid flow velocities of 13 to 242 m/day in the Cadeby Formation at the Leeds University study site, and modelling work over a wider area suggested very rapid flows of up to 9000 m/day (Medici et al 2019a,b). These studies also showed that very low effective porosities (2.8 x 10-4) are needed to represent the karstic development of permeability in the Permian limestones and the potential large scale of contaminant transport. The data collated in this report demonstrate that a component of unsaturated zone flow in the Permian limestones is rapid, but the proportion of rapid flow, and the frequency of rapid flowpaths that extend through the entire unsaturated zone, is uncertain. Evidence of cave, conduit and solutional fissure development; and some high transmissivities and high borehole yields, especially where gypsum is present, suggest that there are saturated zone networks of solutional fissures and conduits which might enable pollutant transport over long distances and in unexpected directions, but further work is needed to determine how frequently these networks occur and how extensive they are. Such networks can form along stream sink to spring flowpaths or through mixing corrosion. Overall, this report highlights the importance of karst in the Permian limestones, the complexities of the interactions with the evaporite karst, and the need for further development of karst datasets and conceptualisation of the karst hydrogeology to assist with groundwater studies and management in this area

Diffraction Symmetry in Crystalline, Close-Packed C60

We have grown crystals of the carbon structure C60 by sublimation. In contrast to solution-grown crystals, the sublimed crystals have long range order with no evidence of solvent inclusions. Sublimed C60 forms three dimensional, faceted crystals with a close-packed, face-centered cubic unit cell. We have refined a crystal structure using the "soccer ball" model of the C60 molecule. The results indicate that the C60 molecule has the expected spherical shape, however the data are not sufficiently accurate to unambiguously determine atomic positions