W. Lyons, A. Carey, P. Croot, T. Henry, Sue A. Welch, Devin F. Smith, C. Gardner
Abstract:The denudation of any landscape occurs by both physical means (i.e. mechanical weathering and erosion) and also chemical means (i.e. dissolution of minerals). The rates of these different processes can vary greatly in both time and lithology. Herein we present the rates of physical weathering and also data on aluminosilicate and carbonate mineral weathering in a dozen Irish catchments using newly collected river geochemical data and previously published riverine suspended sediment information. Our carbonate denudation yields range from approximately 30 to 145 tons km-2 yr-1, while physical erosion yields are at least an order of magnitude less in most cases and silicate weathering yields are mostly <1 ton km-2 yr-1. Our analysis clearly demonstrates the importance of carbonate mineral dissolution in landscape lowering, supporting the notion previously put forward by Simms (2004a,b) of the analogy of the tortoise and the hare in geomorphologically shaping the surface of Ireland.
{"title":"Current chemical denudation, silicate mineral weathering and erosion in Irish catchments: reflections on the tortoise and the hare","authors":"W. Lyons, A. Carey, P. Croot, T. Henry, Sue A. Welch, Devin F. Smith, C. Gardner","doi":"10.3318/ijes.2020.38.3","DOIUrl":"https://doi.org/10.3318/ijes.2020.38.3","url":null,"abstract":"Abstract:The denudation of any landscape occurs by both physical means (i.e. mechanical weathering and erosion) and also chemical means (i.e. dissolution of minerals). The rates of these different processes can vary greatly in both time and lithology. Herein we present the rates of physical weathering and also data on aluminosilicate and carbonate mineral weathering in a dozen Irish catchments using newly collected river geochemical data and previously published riverine suspended sediment information. Our carbonate denudation yields range from approximately 30 to 145 tons km-2 yr-1, while physical erosion yields are at least an order of magnitude less in most cases and silicate weathering yields are mostly <1 ton km-2 yr-1. Our analysis clearly demonstrates the importance of carbonate mineral dissolution in landscape lowering, supporting the notion previously put forward by Simms (2004a,b) of the analogy of the tortoise and the hare in geomorphologically shaping the surface of Ireland.","PeriodicalId":35911,"journal":{"name":"Irish Journal of Earth Sciences","volume":"38 1","pages":"15 - 23"},"PeriodicalIF":0.0,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48093116","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract:South Mayo occupies a unique position in the British and Irish Caledonides in preserving little deformed Ordovician sedimentary and volcanic rocks between outcrops of a Laurentian cover sequence (Dalradian Supergroup) that shows evidence for the Grampian Orogeny and now lie both to the north and the south. The regionally significant arc volcanic rocks of the Lough Nafooey Group (LNG) display a simple northward dipping and younging succession that shows overall change from more primitive to more evolved magmatic compositions with time. New field data are used to reject the previous interpretation of an isoclinal fold pair within the group. The age range of the LNG remains poorly constrained. The upper parts are early Ordovician in age, but the lower parts are likely to be Cambrian. The LNG can be shown to be unconformably overlain by patches of Floian-aged limestone (Currarevagh Limestone Formation) which in turn is unconformably overlain by clastic sediments of the Darriwilian-aged Rosroe Formation. The Rosroe Formation has a muddy basal subunit (Bencraff Member) in the west that appears to die out eastwards. The clear unconformity bounded stratigraphic sequence of the southern limb of the South Mayo Trough allows rejection of the hypothesis that it represents a dismembered faulted succession. Although there are clearly episodes of early Ordovician tilting, the first major compressional deformation that produced folds affecting the South Mayo Trough occurred sometime between the Late Ordovician (Sandbian) and Early Silurian (Telychian).
{"title":"The structure and stratigraphical relations of the Lough Nafooey Group, South Mayo","authors":"J. R. Graham","doi":"10.3318/ijes.2019.37.1","DOIUrl":"https://doi.org/10.3318/ijes.2019.37.1","url":null,"abstract":"Abstract:South Mayo occupies a unique position in the British and Irish Caledonides in preserving little deformed Ordovician sedimentary and volcanic rocks between outcrops of a Laurentian cover sequence (Dalradian Supergroup) that shows evidence for the Grampian Orogeny and now lie both to the north and the south. The regionally significant arc volcanic rocks of the Lough Nafooey Group (LNG) display a simple northward dipping and younging succession that shows overall change from more primitive to more evolved magmatic compositions with time. New field data are used to reject the previous interpretation of an isoclinal fold pair within the group. The age range of the LNG remains poorly constrained. The upper parts are early Ordovician in age, but the lower parts are likely to be Cambrian. The LNG can be shown to be unconformably overlain by patches of Floian-aged limestone (Currarevagh Limestone Formation) which in turn is unconformably overlain by clastic sediments of the Darriwilian-aged Rosroe Formation. The Rosroe Formation has a muddy basal subunit (Bencraff Member) in the west that appears to die out eastwards. The clear unconformity bounded stratigraphic sequence of the southern limb of the South Mayo Trough allows rejection of the hypothesis that it represents a dismembered faulted succession. Although there are clearly episodes of early Ordovician tilting, the first major compressional deformation that produced folds affecting the South Mayo Trough occurred sometime between the Late Ordovician (Sandbian) and Early Silurian (Telychian).","PeriodicalId":35911,"journal":{"name":"Irish Journal of Earth Sciences","volume":"37 1","pages":"1 - 18"},"PeriodicalIF":0.0,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49583924","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract:A database of thermal conductivity values for 50 formations of Irish rock has been established and is presented here. All of the testing was carried out on a single divided bar apparatus at University College Dublin (UCD). The aim of this work is to provide thermal conductivity input parameters for the design of future small to medium-scale geothermal projects in Ireland. Some tests were repeated and additional tests were carried out on two other independent devices in order to prove the reliability and repeatability of the UCD divided bar device. Results were generally found to be within ±5% of one another. The resulting thermal conductivity values are in a narrow range and are consistent with worldwide published values for similar rocks found elsewhere. Rock porosity and the relative abundances of the mineral compositions were found to be the main controlling factors on the thermal conductivity values. No variation with thermal conductivity with depth or rock density was found. Further thermal conductivity tests carried out on rock chippings, 1.8mm to 5mm in size, of some of the lithologies; suggest that this may be a viable measurement technique, though further testing is required to verify this.
{"title":"Thermal conductivity of Irish rocks","authors":"M. Long, S. Murray, R. Pasquali","doi":"10.3318/IJES.2018.36.63","DOIUrl":"https://doi.org/10.3318/IJES.2018.36.63","url":null,"abstract":"Abstract:A database of thermal conductivity values for 50 formations of Irish rock has been established and is presented here. All of the testing was carried out on a single divided bar apparatus at University College Dublin (UCD). The aim of this work is to provide thermal conductivity input parameters for the design of future small to medium-scale geothermal projects in Ireland. Some tests were repeated and additional tests were carried out on two other independent devices in order to prove the reliability and repeatability of the UCD divided bar device. Results were generally found to be within ±5% of one another. The resulting thermal conductivity values are in a narrow range and are consistent with worldwide published values for similar rocks found elsewhere. Rock porosity and the relative abundances of the mineral compositions were found to be the main controlling factors on the thermal conductivity values. No variation with thermal conductivity with depth or rock density was found. Further thermal conductivity tests carried out on rock chippings, 1.8mm to 5mm in size, of some of the lithologies; suggest that this may be a viable measurement technique, though further testing is required to verify this.","PeriodicalId":35911,"journal":{"name":"Irish Journal of Earth Sciences","volume":"36 1","pages":"63 - 80"},"PeriodicalIF":0.0,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69516427","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract:Inter-tidal environments play a central role in relative sea level (RSL) reconstruction studies and the use of composite records developed from elemental (organic carbon, total nitrogen) and isotopie (δ¹³C) data have recently been applied in these environments. Sample pretreatment to remove inorganic carbon is a critical first step in this approach, but can distort the data. This paper presents the results of a comparative pilot study examining the performance of two acid preparation techniques (acid rinsing and acid fumigation) when applied to saltmarsh sediments from the Portmarnock and Shannon estuaries. In high marsh to supratidal settings, acid rinsing caused depletion of both C org and N tot, though no significant change to Corg/Ntot (C/N) was recorded. At lower altitudes, increased Ntot losses led to distortion of C/N ratios. Both pre-treatment methods produced comparable δ¹³C signatures in higher elevation contexts, but acid rinsing produced a depletion of 0.6‰ in low marsh and tidal flat samples. Whilst differences between pretreatment methods are observed, offsets are relatively small when compared to the range of elemental and isotopie values encountered across a saltmarsh and should not affect environmental interpretations when used for RSL reconstruction.
{"title":"EVALUATING THE INFLUENCE OF SELECTED ACID PRE-TREATMENT METHODS ON C/N AND δ¹³C OF TEMPERATE INTER-TIDAL SEDIMENTS FOR RELATIVE SEA LEVEL RECONSTRUCTION","authors":"K. Craven, R. Edwards, R. Goodhue, C. Rocha","doi":"10.1353/ijes.2013.0004","DOIUrl":"https://doi.org/10.1353/ijes.2013.0004","url":null,"abstract":"Abstract:Inter-tidal environments play a central role in relative sea level (RSL) reconstruction studies and the use of composite records developed from elemental (organic carbon, total nitrogen) and isotopie (δ¹³C) data have recently been applied in these environments. Sample pretreatment to remove inorganic carbon is a critical first step in this approach, but can distort the data. This paper presents the results of a comparative pilot study examining the performance of two acid preparation techniques (acid rinsing and acid fumigation) when applied to saltmarsh sediments from the Portmarnock and Shannon estuaries. In high marsh to supratidal settings, acid rinsing caused depletion of both C org and N tot, though no significant change to Corg/Ntot (C/N) was recorded. At lower altitudes, increased Ntot losses led to distortion of C/N ratios. Both pre-treatment methods produced comparable δ¹³C signatures in higher elevation contexts, but acid rinsing produced a depletion of 0.6‰ in low marsh and tidal flat samples. Whilst differences between pretreatment methods are observed, offsets are relatively small when compared to the range of elemental and isotopie values encountered across a saltmarsh and should not affect environmental interpretations when used for RSL reconstruction.","PeriodicalId":35911,"journal":{"name":"Irish Journal of Earth Sciences","volume":"31 1","pages":"25 - 42"},"PeriodicalIF":0.0,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46460235","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J. Murray, H. Nasheuer, C. Seoighe, G. McCormack, D. M. Williams, D. Harper
Abstract:AbstractThe study of human evolution began in earnest with the discovery of fossil human remains in a cave in the Neander Valley of Germany in 1856. William King (1809–1886), Professor of Geology and Mineralogy at Queen's College Galway, as NUI Galway was then known, obtained a plaster replica of the skullcap and, following careful examination, proposed the name Homo neanderthalensis for the specimen at the 1863 meeting of the British Association for the Advancement of Science. This suggestion was both extraordinary and revolutionary for its time. To his lasting credit, William King remains the first scientist to name a new and extinct species of human based on actual fossil hominin material. King's proposal effectively marked the beginning of one of the longest standing debates in human evolutionary studies—the precise taxonomic and phylogenetic position of Neanderthals. Opinion remains divided as to whether they should be given specific (sensu King) or subspecific status, and studies of Neanderthal ancient DNA have further fuelled this debate. Palaeoanthropology as a scientific discipline began with the acceptance that different species of human had existed in the past and King made a singular contribution to that development.
{"title":"The Contribution of William King to the Early Development of Palaeoanthropology","authors":"J. Murray, H. Nasheuer, C. Seoighe, G. McCormack, D. M. Williams, D. Harper","doi":"10.3318/IJES.2015.33.1","DOIUrl":"https://doi.org/10.3318/IJES.2015.33.1","url":null,"abstract":"Abstract:AbstractThe study of human evolution began in earnest with the discovery of fossil human remains in a cave in the Neander Valley of Germany in 1856. William King (1809–1886), Professor of Geology and Mineralogy at Queen's College Galway, as NUI Galway was then known, obtained a plaster replica of the skullcap and, following careful examination, proposed the name Homo neanderthalensis for the specimen at the 1863 meeting of the British Association for the Advancement of Science. This suggestion was both extraordinary and revolutionary for its time. To his lasting credit, William King remains the first scientist to name a new and extinct species of human based on actual fossil hominin material. King's proposal effectively marked the beginning of one of the longest standing debates in human evolutionary studies—the precise taxonomic and phylogenetic position of Neanderthals. Opinion remains divided as to whether they should be given specific (sensu King) or subspecific status, and studies of Neanderthal ancient DNA have further fuelled this debate. Palaeoanthropology as a scientific discipline began with the acceptance that different species of human had existed in the past and King made a singular contribution to that development.","PeriodicalId":35911,"journal":{"name":"Irish Journal of Earth Sciences","volume":"33 1","pages":"1 - 16"},"PeriodicalIF":0.0,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3318/IJES.2015.33.1","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44825965","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-01-01DOI: 10.3318/IRISJEARTSCIE.2019.09
A. Brooks, R. Edwards
Abstract:Despite a corpus of qualitative relative sea-level (RSL) data from Ireland, there exists a comparative paucity of precise and reliable information concerning changes since the Last Glacial Maximum (LGM). Much of the existing data are disparate in nature, having been produced by a range of studies employing different methodologies and often not specifically concerned with sea-level reconstruction. Consequently, there are large spatial and temporal gaps in our understanding of RSL changes, whilst other data are ambiguous and prone to misinterpretation. This paper presents a new database of sea-level information extracted from existing publications. Data are screened and classified into one of four groups according to their utility as indicators of RSL change. This objective classification, based upon well-established sea-level methodology, permits researchers to readily identify the most reliable trends in the available information, and helps to discriminate potentially erroneous data. The database is freely available on-line and should prove a valuable resource to researchers working in coastal environments around Ireland. It will be updated as new information becomes available, ensuring maximum value is extracted from the collection of new sea-level data and highlighting areas where more work is urgently needed.
{"title":"The Development of a Sea-Level Database for Ireland","authors":"A. Brooks, R. Edwards","doi":"10.3318/IRISJEARTSCIE.2019.09","DOIUrl":"https://doi.org/10.3318/IRISJEARTSCIE.2019.09","url":null,"abstract":"Abstract:Despite a corpus of qualitative relative sea-level (RSL) data from Ireland, there exists a comparative paucity of precise and reliable information concerning changes since the Last Glacial Maximum (LGM). Much of the existing data are disparate in nature, having been produced by a range of studies employing different methodologies and often not specifically concerned with sea-level reconstruction. Consequently, there are large spatial and temporal gaps in our understanding of RSL changes, whilst other data are ambiguous and prone to misinterpretation. This paper presents a new database of sea-level information extracted from existing publications. Data are screened and classified into one of four groups according to their utility as indicators of RSL change. This objective classification, based upon well-established sea-level methodology, permits researchers to readily identify the most reliable trends in the available information, and helps to discriminate potentially erroneous data. The database is freely available on-line and should prove a valuable resource to researchers working in coastal environments around Ireland. It will be updated as new information becomes available, ensuring maximum value is extracted from the collection of new sea-level data and highlighting areas where more work is urgently needed.","PeriodicalId":35911,"journal":{"name":"Irish Journal of Earth Sciences","volume":"24 1","pages":"13 - 27"},"PeriodicalIF":0.0,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45273388","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract:Retepora undata M'Coy, 1844, from the Mississippian of Ireland is shown to be a phylloporinid bryozoan of the genus Chainodictyon Foerste, 1887. It forms reticulated zoaria of anastomosing branches with characteristic droplet-shaped fenestrules. The status of the genus Phylloporella Frederiks, 1916, which was originally named with two type species is here formalised through designation of Retepora undata M'Coy, 1844, as the type species. Phylloporella Frederiks, 1916, is a junior synonym of Chainodictyon, Foerste, 1887.
{"title":"RETEPORA UNDATA M'COY, 1844, TYPE SPECIES OF PHYLLOPORELLA FREDERIKS, 1916, A JUNIOR SYNONYM OF CHAINODICTYON FOERSTE, 1887: A PHYLLOPORINID BRYOZOAN FROM THE MISSISSIPPIAN OF IRELAND REDESCRIBED","authors":"P. W. Jackson, F. Mckinney, A. Ernst","doi":"10.3318/IJES.2010.28.53","DOIUrl":"https://doi.org/10.3318/IJES.2010.28.53","url":null,"abstract":"Abstract:Retepora undata M'Coy, 1844, from the Mississippian of Ireland is shown to be a phylloporinid bryozoan of the genus Chainodictyon Foerste, 1887. It forms reticulated zoaria of anastomosing branches with characteristic droplet-shaped fenestrules. The status of the genus Phylloporella Frederiks, 1916, which was originally named with two type species is here formalised through designation of Retepora undata M'Coy, 1844, as the type species. Phylloporella Frederiks, 1916, is a junior synonym of Chainodictyon, Foerste, 1887.","PeriodicalId":35911,"journal":{"name":"Irish Journal of Earth Sciences","volume":"28 1","pages":"53 - 60"},"PeriodicalIF":0.0,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46236572","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract:The discovery of a dolerite dike exposed near Ross, Ballynakill Harbour, in north-western Connemara has re-opened investigation into two contrasting dolerite dike populations in Connemara, of respective mid-Paleozoic and Paleocene age. Initial examination of the Ross dike found it to share characteristics with both populations. Its mineralogical alteration and structural parameters appear to match those of the mid-Paleozoic dikes, whereas its geochemistry shows similarities with the Paleocene dikes; however, trace element and rare-earth element data assign it convincingly with the latter, despite differences that are explicable. A review of incompatible trace element parameters for the two suites confirms that the mid-Paleozoic magmas were volcanic-arc type basalts and the Paleocene magmas a singular species of within-plate type basalts. Initial 87Sr/86Sr ratios for the Paleocene dolerites fall in a tight cluster around 0.704. A wider range of 0.704–0.708 for the mid-Paleozoic dikes is attributed to a regionally imposed retrograde hydrothermal metamorphism. This is confirmed from an additional 39Ar-40Ar analysis to have a late Triassic age. The mid-Paleozoic dikes are further constrained to be of late Devonian age.
{"title":"Distinguishing dolerite dike populations in post-grampian Connemara","authors":"P. Mohr, J. Hunt, Helen Riekstins, P. Kennan","doi":"10.3318/IJES.2018.36.1","DOIUrl":"https://doi.org/10.3318/IJES.2018.36.1","url":null,"abstract":"Abstract:The discovery of a dolerite dike exposed near Ross, Ballynakill Harbour, in north-western Connemara has re-opened investigation into two contrasting dolerite dike populations in Connemara, of respective mid-Paleozoic and Paleocene age. Initial examination of the Ross dike found it to share characteristics with both populations. Its mineralogical alteration and structural parameters appear to match those of the mid-Paleozoic dikes, whereas its geochemistry shows similarities with the Paleocene dikes; however, trace element and rare-earth element data assign it convincingly with the latter, despite differences that are explicable. A review of incompatible trace element parameters for the two suites confirms that the mid-Paleozoic magmas were volcanic-arc type basalts and the Paleocene magmas a singular species of within-plate type basalts. Initial 87Sr/86Sr ratios for the Paleocene dolerites fall in a tight cluster around 0.704. A wider range of 0.704–0.708 for the mid-Paleozoic dikes is attributed to a regionally imposed retrograde hydrothermal metamorphism. This is confirmed from an additional 39Ar-40Ar analysis to have a late Triassic age. The mid-Paleozoic dikes are further constrained to be of late Devonian age.","PeriodicalId":35911,"journal":{"name":"Irish Journal of Earth Sciences","volume":"36 1","pages":"1 - 16"},"PeriodicalIF":0.0,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47115316","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-01-01DOI: 10.3318/IJES.2005.23.1.1
P. Cózar, I. Somerville, M. Aretz, H. Herbig
Abstract:Foraminiferans, calcareous algae and rugose corals from many sections in the Glencar Limestone, Dartry Limestone, Bricklieve Limestone and Meenymore formations in north-western Ireland have been analysed. Results from the fauna and microflora suggest that these formations constitute the early to late Asbian for the Glencar Limestone Formation and lower Bricklieve Limestone Formation (Cf6β-Cf6γ foraminiferal subzones), and the upper part of the late Asbian for the Dartry Limestone Formation and upper Bricklieve Limestone Formation (Cf6γ Subzone). The succeeding Meenymore Formation in the studied area is assigned to the Brigantian (Cf6δ Subzone). Goniatite biozonal schemes established previously for equivalent strata to the east in the Cuilcagh Mountains that are not in harmony with the dating proposed here are discussed.
{"title":"Biostratigraphical Dating of Upper Viséan Limestones (NW Ireland) using Foraminiferans, Calcareous Algae and Rugose Corals","authors":"P. Cózar, I. Somerville, M. Aretz, H. Herbig","doi":"10.3318/IJES.2005.23.1.1","DOIUrl":"https://doi.org/10.3318/IJES.2005.23.1.1","url":null,"abstract":"Abstract:Foraminiferans, calcareous algae and rugose corals from many sections in the Glencar Limestone, Dartry Limestone, Bricklieve Limestone and Meenymore formations in north-western Ireland have been analysed. Results from the fauna and microflora suggest that these formations constitute the early to late Asbian for the Glencar Limestone Formation and lower Bricklieve Limestone Formation (Cf6β-Cf6γ foraminiferal subzones), and the upper part of the late Asbian for the Dartry Limestone Formation and upper Bricklieve Limestone Formation (Cf6γ Subzone). The succeeding Meenymore Formation in the studied area is assigned to the Brigantian (Cf6δ Subzone). Goniatite biozonal schemes established previously for equivalent strata to the east in the Cuilcagh Mountains that are not in harmony with the dating proposed here are discussed.","PeriodicalId":35911,"journal":{"name":"Irish Journal of Earth Sciences","volume":"23 1","pages":"1 - 23"},"PeriodicalIF":0.0,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44373985","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-01-01DOI: 10.3318/IJES.2004.22.1.15
P. Mohr
Abstract:Composite dolerite-rhyolite dikes traverse the Galway Granite batholith and its adjacent envelope. The dikes pertain to the Teach Dóite suite and were previously considered to be of Carboniferous age. New and extended examination of field relationships supports recent radiometric dating for an intrusive period that overlapped with the final consolidation of the Galway batholith. Regional crustal extension produced a complex pattern of fissuring, controlled by various pre-existing structures, which permitted ascent of mantle-derived melts into and around the Galway batholith. Ponding of mafic magma at an intermediate level facilitated crustal partial melting and the generation of high-silica, high-alumina rhyolitic melts. The two contrasting magmas then rose into common or proximate dike fissures, rhyolitic injection immediately following that of dolerite. Magma storage in stratified chambers occasionally resulted in the development of a hybrid magma layer, but in all cases minor mingling and mixing beween dolerite and rhyolite magma continued up into the dikes. Rhyolite geochemistry precludes a genetic relationship with the Galway granitoids, despite a few instances where granitic material was entrained into rhyolitic magma.
{"title":"Late Magmatism of the Galway Granite Batholith: II. Composite Dolerite-Rhyolite Dikes","authors":"P. Mohr","doi":"10.3318/IJES.2004.22.1.15","DOIUrl":"https://doi.org/10.3318/IJES.2004.22.1.15","url":null,"abstract":"Abstract:Composite dolerite-rhyolite dikes traverse the Galway Granite batholith and its adjacent envelope. The dikes pertain to the Teach Dóite suite and were previously considered to be of Carboniferous age. New and extended examination of field relationships supports recent radiometric dating for an intrusive period that overlapped with the final consolidation of the Galway batholith. Regional crustal extension produced a complex pattern of fissuring, controlled by various pre-existing structures, which permitted ascent of mantle-derived melts into and around the Galway batholith. Ponding of mafic magma at an intermediate level facilitated crustal partial melting and the generation of high-silica, high-alumina rhyolitic melts. The two contrasting magmas then rose into common or proximate dike fissures, rhyolitic injection immediately following that of dolerite. Magma storage in stratified chambers occasionally resulted in the development of a hybrid magma layer, but in all cases minor mingling and mixing beween dolerite and rhyolite magma continued up into the dikes. Rhyolite geochemistry precludes a genetic relationship with the Galway granitoids, despite a few instances where granitic material was entrained into rhyolitic magma.","PeriodicalId":35911,"journal":{"name":"Irish Journal of Earth Sciences","volume":"22 1","pages":"15 - 32"},"PeriodicalIF":0.0,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44458438","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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