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Simms M.J.,National Museums Northern Ireland
Proceedings of the Geologists' Association | Year: 2015

The Stac Fada Member, an impact ejecta deposit within the Mesoproterozoic Stoer Group, is represented today by just a narrow outcrop, truncated by faulting and erosion, extending for 50. km north-south along the coast of north-west Scotland. It appears to represent a non-erosive Single Layer Ejecta deposit rather than the erosively emplaced Double Layer Ejecta deposits characteristic of terrestrial impact craters and it is unique in preserving spallation debris, ejected very early in the impact process, beneath the ejecta blanket. Various sedimentary structures associated with the Stac Fada Member, from ejecta intrusions along bedding planes immediately beneath it, to erosional troughs eroded into its top, consistently indicate emplacement from the east. No surface manifestation of an impact crater has been identified but there is a remarkable correspondence between its location, as inferred from these directional data, and the position of the Lairg Gravity Low, an ~40. km diameter geophysical anomaly centred more than 50. km east of the closest point on the Stoer Group outcrop. Proximal-distal facies changes along the outcrop of the ejecta deposit are consistent with this inferred relationship between the ejecta deposit and the gravity low. Post-impact drainage reconfiguration suggests a regional isostatic doming in response to excavation of the crater that also appears to be centred on the Lairg Gravity Low. Comparison with gravity data from impact craters elsewhere suggests that the Lairg Gravity Low represents a complex crater at least 40. km in diameter that now lies buried beneath the Moine Thrust complex. © 2015 The Geologists' Association. Source


McNeill G.,Agri Food and Biosciences Institute AFBI | Nunn J.,National Museums Northern Ireland | Minchin D.,Marine Organism Investigations
Aquatic Invasions | Year: 2010

Chains and solitary individuals of the slipper limpet Crepidula fornicata were found, some with egg capsules, at several localities within Belfast Lough on the north-east coast of Ireland during 2009. The species is widely dispersed, being found on the lower shore to depths of 7 m attached to scallops, mussels and stones and so is considered to be established. Shell winter growth checks indicated a possible arrival in or before 2004. While there have been previous records of this invasive species in Ireland, this is the only known established population. © 2010 The Author(s). Source


Paul C.R.C.,University of Bristol | Simms M.J.,National Museums Northern Ireland
Proceedings of the Geologists' Association | Year: 2012

Ammonites with bivalves or worm tubes attached are relatively rare among the abundant specimens in the Lower Jurassic (Sinemurian) mudstones at Bishop's Cleeve, Gloucestershire, UK, but provide evidence for ammonite taphonomy, environmental conditions and biological interactions between ammonites and epifauna. Epifauna attached only to one side or within the body chambers of ammonites usually indicate post-mortem attachment. Epifauna on both sides of, or overgrown by, ammonites attached in vivo. One large example of Oxynoticeras has at least 51 encrusting bivalves attached exclusively to one side indicating it formed a 'benthic island'. Four, presumably annual, bivalve cohorts are recognized, with variation in preferred orientation in each cohort suggesting that current direction varied. Both the ammonite and its epifauna were buried by a single sedimentation event. Other informative examples include a Cheltonia that overgrew an epifaunal bivalve, and an example of Bifericeras which bears two clusters of four worm tubes, one of which apparently attached in vivo, the other post-mortem. Other examples bear too few specimens to be certain of the timing of attachment, but most probably attached post-mortem. © 2011 The Geologists' Association. Source


Farrant A.R.,British Geological Survey | Simms M.J.,National Museums Northern Ireland
Cave and Karst Science | Year: 2011

Discovered in 1994, Ogof Draenen is currently the longest cave in Britain and among the thirty longest caves in the World, with a surveyed length in excess of 70km. Like other great caves, Ogof Draenen has had a complex multiphase history. This interpretation of the genesis of the cave is based on speleo-morphological observations throughout the system. Evidence of at least four phases of cave development can be identified, associated with major shifts in resurgence location and changes in flow direction of up to 180°. Joints have had a dominant influence on passage genesis. In particular joints have facilitated the development of maze networks and remarkably shallow horizontal phreatic conduits. The amplitude of these conduits is much shallower than predicted by models based on flow path length and stratal dip. Here, we suggest that presence of laterally extensive open joints, orientated perpendicular to the regional neo-tectonic principal stress field, determines the depth of flow in the aquifer, rather than fissure frequency per se as suggested in Ford's Four State Model. We argue that the rate of base-level lowering, coupled with the depth of karstification determines whether a cave responds by phreatic capture or vadose incision. Maze cave networks within Ogof Draenen were probably initiated by bedrock-hosted sulphide oxidation and sulphuric acid speleogenesis. © British Cave Research Association 2011. Source


Morrow C.C.,Queens University of Belfast | Picton B.E.,National Museums Northern Ireland | Erpenbeck D.,Ludwig Maximilians University of Munich | Boury-Esnault N.,Aix - Marseille University | And 2 more authors.
Molecular Phylogenetics and Evolution | Year: 2012

The current morphological classification of the Demospongiae G4 clade was tested using large subunit ribosomal RNA (LSU rRNA) sequences from 119 taxa. Fifty-three mitochondrial cytochrome oxidase 1 (CO1) barcoding sequences were also analysed to test whether the 28S phylogeny could be recovered using an independent gene. This is the largest and most comprehensive study of the Demospongiae G4 clade. The 28S and CO1 genetrees result in congruent clades but conflict with the current morphological classification. The results confirm the polyphyly of Halichondrida, Hadromerida, Dictyonellidae, Axinellidae and Poecilosclerida and show that several of the characters used in morphological classifications are homoplasious. Robust clades are clearly shown and a new hypothesis for relationships of taxa allocated to G4 is proposed. © 2011 Elsevier Inc. Source

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