In Joyces Country in western Ireland, the ~ E-W striking axial plane of the D7 Ben Levy anticline folded Dalradian and unconformable Silurian rocks. The north side of the fold is mostly coincident with the contemporaneous ESE-WNW striking steeply dipping Coolin Fault close to the Dalradian-basal Silurian contact. This fault was first initiated by sinistral strike-slip motion, probably of Ordovician age, and then secondly used by post-Wenlock down throw on the north side to form the D7 anticline. Later a newly recognised third motion of reverse reactivation on the fault uplifted the north limb of the fold and locally overturned the Silurian succession against irregularities in the SSW dip of the fault. Still later, but pre-374Ma (Devonian), NE-SW faulting exposed different previous levels of the Coolin Fault zone. The superb Dalradian rock exposure provides details not generally apparent on other reactivated faults in Connemara.
{"title":"New Data on the Ben Levy Anticline, With Reverse Reactivation on the Coolin Fault Giving Up-Side-Down Silurian Rocks in Joyces Country, Connemara","authors":"B. Leake","doi":"10.1353/ijes.0.a916010","DOIUrl":"https://doi.org/10.1353/ijes.0.a916010","url":null,"abstract":"In Joyces Country in western Ireland, the ~ E-W striking axial plane of the D7 Ben Levy anticline folded Dalradian and unconformable Silurian rocks. The north side of the fold is mostly coincident with the contemporaneous ESE-WNW striking steeply dipping Coolin Fault close to the Dalradian-basal Silurian contact. This fault was first initiated by sinistral strike-slip motion, probably of Ordovician age, and then secondly used by post-Wenlock down throw on the north side to form the D7 anticline. Later a newly recognised third motion of reverse reactivation on the fault uplifted the north limb of the fold and locally overturned the Silurian succession against irregularities in the SSW dip of the fault. Still later, but pre-374Ma (Devonian), NE-SW faulting exposed different previous levels of the Coolin Fault zone. The superb Dalradian rock exposure provides details not generally apparent on other reactivated faults in Connemara.","PeriodicalId":35911,"journal":{"name":"Irish Journal of Earth Sciences","volume":"8 ","pages":"-"},"PeriodicalIF":0.0,"publicationDate":"2023-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139024511","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}
Most of the Connemara granites, including the Galway Granite batholith, have a clearly defined circular or ellipsoidal outcrop shape and are I-Type granites often with K-feldspar phenocrysts, whereas the Oughterard Granite (OG) forms numerous small intrusions scattered east-west over 40km with two larger linked bodies near Oughterard and is S-Type and aphyric. The only comprehensive mapping, mineralogical and chemical study of the OG was published over 50 years ago before the important 1974 recognition of the distinction of I- and S-Type granites was first made. New mapping of the southern Oughterard area with small OG intrusions is presented and many scattered published chemical and Rb, Sr, S and Pb isotopic studies integrated to confirm overall their individual conclusions that the peraluminous OG is of S-Type, being formed from melted Dalradian rocks as are the fluid-carried associated uneconomic mineral deposits. The OG is confined to the high sillimanite zone, mostly south of, and mainly later than, the 465-464Ma D4 Connemara Antiform, where a wide (>15km N-S) >70km E-W band of 469Ma gabbros and 467Ma quartz diorite gneisses intruded into already hot Dalradian rocks undergoing regional metamorphism. This generated the OG magmas by partial melting of pelites and semi-pelites. The upward intrusion of the OG magma was significantly delayed, as has been shown by precise dating in other granites elsewhere, to ~464-461Ma during the late stages and mostly after D4 but before the country rocks had completely cooled. The OG intrusions as a whole probably form the second largest area of S-Type granite in Ireland, after the Leinster Granite.
包括戈尔韦花岗岩浴成岩在内的大多数康尼马拉花岗岩都有明确的圆形或椭圆形露头形状，属于 I 型花岗岩，通常带有 K 长石表晶；而奥特拉德花岗岩（OG）则形成了许多小型侵入体，东西向散布在 40 公里的范围内，在奥特拉德附近有两个较大的相连岩体，属于 S 型花岗岩和斑岩。在 1974 年首次确认 I 型和 S 型花岗岩的重要区别之前，对 OG 进行的唯一一次全面测绘、矿物学和化学研究是在 50 多年前发表的。本报告介绍了带有小型 OG 侵入体的奥特拉德（Oughterard）南部地区的新测绘情况，并整合了许多分散出版的化学和 Rb、Sr、S 和 Pb 同位素研究报告，从总体上证实了它们各自的结论，即过铝 OG 属于 S 型，与流体携带的相关非经济矿藏一样，是由熔化的达拉地岩形成的。OG 局限于高矽卡岩区，主要位于 465-464Ma D4 康尼马拉锑化岩以南，主要晚于 465-464Ma D4 康尼马拉锑化岩，在这里，469Ma 的辉长岩和 467Ma 的石英闪长岩片麻岩组成的宽阔（南北方向大于 15 千米）、东西方向大于 70 千米的岩带侵入了正在进行区域变质作用的热达拉地岩。通过辉长岩和半辉长岩体的部分熔融，产生了OG岩浆。正如其他地区花岗岩的精确测年所显示的那样，OG岩浆的向上侵入明显延迟，在晚期阶段延迟到~464-461Ma，主要是在D4之后，但在乡土岩完全冷却之前。整个 OG 侵入体可能是爱尔兰仅次于莱恩斯特花岗岩的第二大 S 型花岗岩区域。
{"title":"New Light on the Oughterard Granite: Connemara’s S-Type Granite, Ireland","authors":"B. Leake","doi":"10.1353/ijes.0.a916009","DOIUrl":"https://doi.org/10.1353/ijes.0.a916009","url":null,"abstract":"Most of the Connemara granites, including the Galway Granite batholith, have a clearly defined circular or ellipsoidal outcrop shape and are I-Type granites often with K-feldspar phenocrysts, whereas the Oughterard Granite (OG) forms numerous small intrusions scattered east-west over 40km with two larger linked bodies near Oughterard and is S-Type and aphyric. The only comprehensive mapping, mineralogical and chemical study of the OG was published over 50 years ago before the important 1974 recognition of the distinction of I- and S-Type granites was first made. New mapping of the southern Oughterard area with small OG intrusions is presented and many scattered published chemical and Rb, Sr, S and Pb isotopic studies integrated to confirm overall their individual conclusions that the peraluminous OG is of S-Type, being formed from melted Dalradian rocks as are the fluid-carried associated uneconomic mineral deposits. The OG is confined to the high sillimanite zone, mostly south of, and mainly later than, the 465-464Ma D4 Connemara Antiform, where a wide (>15km N-S) >70km E-W band of 469Ma gabbros and 467Ma quartz diorite gneisses intruded into already hot Dalradian rocks undergoing regional metamorphism. This generated the OG magmas by partial melting of pelites and semi-pelites. The upward intrusion of the OG magma was significantly delayed, as has been shown by precise dating in other granites elsewhere, to ~464-461Ma during the late stages and mostly after D4 but before the country rocks had completely cooled. The OG intrusions as a whole probably form the second largest area of S-Type granite in Ireland, after the Leinster Granite.","PeriodicalId":35911,"journal":{"name":"Irish Journal of Earth Sciences","volume":"5 3","pages":"-"},"PeriodicalIF":0.0,"publicationDate":"2023-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139016725","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}
The Killary Harbour–Joyce Country succession of Silurian rocks forms the remnant of one of three successor basins that developed after the Grampian Orogeny and which are preserved in western Ireland. Its outcrop everywhere obscures the contact between the Dalradian rocks of Connemara and the Ordovician rocks of the South Mayo Trough. The outcrop is bisected by the prominent north-west trending Maam Valley Fault Zone that is shown to have a component of synsedimentary movement down-throwing to the southwest. The original basin margins lay well outside the current outcrop area. North-south shortening and inversion of the basin was accomplished by reactivation and inversion of earlier fault structures and was exclusively in the brittle zone. Folding of the Silurian rocks with weak to moderate cleavage and deformation of the basement rocks of Connemara was accomplished by largely vertical movements along numerous strike parallel and oblique fractures. Break-back inversion structures were developed along the southern margin of the South Mayo Trough, which include thrusting associated with footwall shortcut faults and clockwise rotation. Although the timing of deformation overlaps that of diorite sill emplacement, it remains poorly constrained in absolute terms.
{"title":"Structural Control of the Deposition and Subsequent Deformation of the Killary Habour-Joyce Country Silurian Succession","authors":"Michael Badley, John Graham, B. Leake","doi":"10.1353/ijes.0.a916339","DOIUrl":"https://doi.org/10.1353/ijes.0.a916339","url":null,"abstract":"The Killary Harbour–Joyce Country succession of Silurian rocks forms the remnant of one of three successor basins that developed after the Grampian Orogeny and which are preserved in western Ireland. Its outcrop everywhere obscures the contact between the Dalradian rocks of Connemara and the Ordovician rocks of the South Mayo Trough. The outcrop is bisected by the prominent north-west trending Maam Valley Fault Zone that is shown to have a component of synsedimentary movement down-throwing to the southwest. The original basin margins lay well outside the current outcrop area. North-south shortening and inversion of the basin was accomplished by reactivation and inversion of earlier fault structures and was exclusively in the brittle zone. Folding of the Silurian rocks with weak to moderate cleavage and deformation of the basement rocks of Connemara was accomplished by largely vertical movements along numerous strike parallel and oblique fractures. Break-back inversion structures were developed along the southern margin of the South Mayo Trough, which include thrusting associated with footwall shortcut faults and clockwise rotation. Although the timing of deformation overlaps that of diorite sill emplacement, it remains poorly constrained in absolute terms.","PeriodicalId":35911,"journal":{"name":"Irish Journal of Earth Sciences","volume":"15 12","pages":"-"},"PeriodicalIF":0.0,"publicationDate":"2023-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139024877","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}
The impact of the Earth’s rotation on circulation patterns in homogenous basins has been well studied using numerical models. This contribution addresses the need for supporting observational studies. Bottom mounted acoustic doppler current (ADCP) velocity profiles are analysed alongside drifter tracks and numerical solutions in order to demonstrate how rotation modifies circulation patterns and horizontal velocity profiles in Lough Corrib, Ireland. The wind driven circulation in Lough Corrib forms a system of topographic gyres, shaped by the complex bathymetry of the basin. Surface and benthic frictional boundary layers are demonstrated to be closely described by classical Ekman theory, despite the system being constrained by shallow water depths (mean depth = 8.4m) and small horizontal dimensions (~10km). Observed velocity profiles can be derived theoretically by summing the two driving forces of the flow (the barotropic pressure gradient force and the surface wind stress force) and their opposing forces (internal friction and Coriolis acceleration). Rotation introduces a significant cross-wind component to the flow, which is thus described as being quasi-geostrophic. The barotropic pressure gradient force is empirically quantified as a function of wind stress by relating surface set-up to the surface water shear velocity. The vertical eddy viscosity profile, derived from ADCP data, increases approximately linearly with increasing depth and is largest at the upper interface of the benthic boundary layer.
{"title":"The Impact of Topography and Rotation in Shaping the Basin-Scale Circulation in Lough Corrib, Ireland, Under Homogenous Conditions","authors":"Heather Cannaby, Martin White","doi":"10.1353/ijes.0.a916338","DOIUrl":"https://doi.org/10.1353/ijes.0.a916338","url":null,"abstract":"The impact of the Earth’s rotation on circulation patterns in homogenous basins has been well studied using numerical models. This contribution addresses the need for supporting observational studies. Bottom mounted acoustic doppler current (ADCP) velocity profiles are analysed alongside drifter tracks and numerical solutions in order to demonstrate how rotation modifies circulation patterns and horizontal velocity profiles in Lough Corrib, Ireland. The wind driven circulation in Lough Corrib forms a system of topographic gyres, shaped by the complex bathymetry of the basin. Surface and benthic frictional boundary layers are demonstrated to be closely described by classical Ekman theory, despite the system being constrained by shallow water depths (mean depth = 8.4m) and small horizontal dimensions (~10km). Observed velocity profiles can be derived theoretically by summing the two driving forces of the flow (the barotropic pressure gradient force and the surface wind stress force) and their opposing forces (internal friction and Coriolis acceleration). Rotation introduces a significant cross-wind component to the flow, which is thus described as being quasi-geostrophic. The barotropic pressure gradient force is empirically quantified as a function of wind stress by relating surface set-up to the surface water shear velocity. The vertical eddy viscosity profile, derived from ADCP data, increases approximately linearly with increasing depth and is largest at the upper interface of the benthic boundary layer.","PeriodicalId":35911,"journal":{"name":"Irish Journal of Earth Sciences","volume":"189 ","pages":"-"},"PeriodicalIF":0.0,"publicationDate":"2023-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139012476","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}
The paper details the sedimentary infill of the northwest part of the Porcupine Basin, offshore west Ireland, during the Cretaceous. This is a critical area for understanding the sediment input and incremental infilling of the basin, particularly during the early Cretaceous. Late Jurassic rifting and early Berriasian erosion produced a northward narrowing valley on the Base Cretaceous unconformity surface, which provided an entry point for sediment into the basin and also constrained the lateral extent of initial sedimentation. Following Berriasian marine transgression, the first deposits in the Porcupine Basin were turbidites located in localised depressions on the unconformity surface (named here informally as Basal Deposits 1–4). As the unconformity surface became smoother, the succeeding layers were more widespread (Sequences 1–3, the top being of probable Barremian age). Several features, interpreted as mounded fans sourced from the basin flanks, are developed in the Valanginian-Barremian section. Where drilled, the Berriasian to Barremian section is predominantly fine-grained. The rifted marginal horsts were covered in late Barremian time, and Aptian and later sediments onlapped the flanks of the Porcupine High to the west. The ‘Near Base Aptian’ is a well-defined prograding surface and the ‘Near Top Aptian’ horizon is a marked unconformity. The Aptian section is comprised predominantly of deep-water mudrocks and siltstones, although a distinctive, possibly shallower, erosive Intra-Aptian event was also mapped. A renewed sediment influx, comprising of sand prone deltaics, occurred at the northern margin of the basin during the Albian. Sand content decreases southwards into the basin. Sedimentation in the late Cretaceous was dominated by the basinwide deposition of the Chalk Group (Cenomanian-Selandian) deposited in a stable thermal subsidence setting. At the northern basin margin Upper Cretaceous deposits are thin and lithologically variable. The well-defined ‘Top Chalk’ reflector, which shows mounded features, is overlain unconformably by Paleocene clastics.
{"title":"Deposition in the Northwest Porcupine Basin During the Cretaceous","authors":"Tareq Shath, David Naylor","doi":"10.1353/ijes.0.a915717","DOIUrl":"https://doi.org/10.1353/ijes.0.a915717","url":null,"abstract":"The paper details the sedimentary infill of the northwest part of the Porcupine Basin, offshore west Ireland, during the Cretaceous. This is a critical area for understanding the sediment input and incremental infilling of the basin, particularly during the early Cretaceous. Late Jurassic rifting and early Berriasian erosion produced a northward narrowing valley on the Base Cretaceous unconformity surface, which provided an entry point for sediment into the basin and also constrained the lateral extent of initial sedimentation. Following Berriasian marine transgression, the first deposits in the Porcupine Basin were turbidites located in localised depressions on the unconformity surface (named here informally as Basal Deposits 1–4). As the unconformity surface became smoother, the succeeding layers were more widespread (Sequences 1–3, the top being of probable Barremian age). Several features, interpreted as mounded fans sourced from the basin flanks, are developed in the Valanginian-Barremian section. Where drilled, the Berriasian to Barremian section is predominantly fine-grained. The rifted marginal horsts were covered in late Barremian time, and Aptian and later sediments onlapped the flanks of the Porcupine High to the west. The ‘Near Base Aptian’ is a well-defined prograding surface and the ‘Near Top Aptian’ horizon is a marked unconformity. The Aptian section is comprised predominantly of deep-water mudrocks and siltstones, although a distinctive, possibly shallower, erosive Intra-Aptian event was also mapped. A renewed sediment influx, comprising of sand prone deltaics, occurred at the northern margin of the basin during the Albian. Sand content decreases southwards into the basin. Sedimentation in the late Cretaceous was dominated by the basinwide deposition of the Chalk Group (Cenomanian-Selandian) deposited in a stable thermal subsidence setting. At the northern basin margin Upper Cretaceous deposits are thin and lithologically variable. The well-defined ‘Top Chalk’ reflector, which shows mounded features, is overlain unconformably by Paleocene clastics.","PeriodicalId":35911,"journal":{"name":"Irish Journal of Earth Sciences","volume":"270 ","pages":"-"},"PeriodicalIF":0.0,"publicationDate":"2023-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139013962","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}
A reassessment of existing data and additional testing on sediment core samples from one site was used to study the extent, nature, composition and engineering properties of the Quaternary interglacial deposits in an area of Cork city and harbour where many future developments are planned. A clear link is apparent between rockhead elevation and the presence of the interglacial deposits. Well-defined pockets of the deposit were proven. These are found mostly on the southern side of the Cork buried valley axis and increase in thickness to the north. The base of the interglacial deposits appears to mirror that of the rockhead and the western extent of the former coincides with a steep drop off in the latter. Much of the deposit encountered in commercial investigations is a thick relatively uniform silt/clay consistent with that described in previous studies. The sediment is predominantly silt sized, but its behaviour and engineering properties are consistent with those of a stiff clay. Sample disturbance effects were found to be significant and these likely result in an underestimation of the preconsolidation stress and the undrained shear strength of the material. Future work would benefit from the use of in-situ site investigation and geophysical techniques.
{"title":"The Distribution and Engineering Properties of Interglacial Deposits in Cork City and Harbour","authors":"Stephen Curtis, Michael Long","doi":"10.1353/ijes.0.a915719","DOIUrl":"https://doi.org/10.1353/ijes.0.a915719","url":null,"abstract":"A reassessment of existing data and additional testing on sediment core samples from one site was used to study the extent, nature, composition and engineering properties of the Quaternary interglacial deposits in an area of Cork city and harbour where many future developments are planned. A clear link is apparent between rockhead elevation and the presence of the interglacial deposits. Well-defined pockets of the deposit were proven. These are found mostly on the southern side of the Cork buried valley axis and increase in thickness to the north. The base of the interglacial deposits appears to mirror that of the rockhead and the western extent of the former coincides with a steep drop off in the latter. Much of the deposit encountered in commercial investigations is a thick relatively uniform silt/clay consistent with that described in previous studies. The sediment is predominantly silt sized, but its behaviour and engineering properties are consistent with those of a stiff clay. Sample disturbance effects were found to be significant and these likely result in an underestimation of the preconsolidation stress and the undrained shear strength of the material. Future work would benefit from the use of in-situ site investigation and geophysical techniques.","PeriodicalId":35911,"journal":{"name":"Irish Journal of Earth Sciences","volume":"58 1","pages":"-"},"PeriodicalIF":0.0,"publicationDate":"2023-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138993878","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}
A vertically embedded orthoconic nautiloid is recorded for the first time from the Clare Shale Formation (Carboniferous; Pennsylvanian) of County Clare, Ireland. The specimen is compared to the few recorded examples of vertically preserved orthocones in the rock record and previously proposed models of this unusual preservation are reviewed. A new model of self-propelled accidental emplacement during predator avoidance manoeuvres is proposed as one possible mode of emplacement.
{"title":"A Vertically Embedded Orthoconic Nautiloid From the Pennsylvanian of County Clare, Ireland – An Unusual Case of ‘Distraction Sinking’?","authors":"Eamon Doyle","doi":"10.1353/ijes.0.a909326","DOIUrl":"https://doi.org/10.1353/ijes.0.a909326","url":null,"abstract":"A vertically embedded orthoconic nautiloid is recorded for the first time from the Clare Shale Formation (Carboniferous; Pennsylvanian) of County Clare, Ireland. The specimen is compared to the few recorded examples of vertically preserved orthocones in the rock record and previously proposed models of this unusual preservation are reviewed. A new model of self-propelled accidental emplacement during predator avoidance manoeuvres is proposed as one possible mode of emplacement.","PeriodicalId":35911,"journal":{"name":"Irish Journal of Earth Sciences","volume":"155 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135605281","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}
The tenth-century high crosses at Monasterboice, with their remarkable panels of stone carving, are unusually well preserved compared with other monuments of the time. A clue to their durability recently came to light during examination of fragments of a small cross discovered at the site that are carved from sandstone impregnated with bitumen. If the major crosses at Monasterboice were carved from the same sandstone, as seems likely, the quality of the carving and its state of preservation might well have been enhanced by the bitumen acting as a weak binding agent and as a water repellent.
{"title":"Is Bitumen the Key to the Quality of the Monasterboice Stone Crosses?","authors":"George Sevastopulo, Roger Stalley, Ian Sanders","doi":"10.1353/ijes.0.a907888","DOIUrl":"https://doi.org/10.1353/ijes.0.a907888","url":null,"abstract":"The tenth-century high crosses at Monasterboice, with their remarkable panels of stone carving, are unusually well preserved compared with other monuments of the time. A clue to their durability recently came to light during examination of fragments of a small cross discovered at the site that are carved from sandstone impregnated with bitumen. If the major crosses at Monasterboice were carved from the same sandstone, as seems likely, the quality of the carving and its state of preservation might well have been enhanced by the bitumen acting as a weak binding agent and as a water repellent.","PeriodicalId":35911,"journal":{"name":"Irish Journal of Earth Sciences","volume":"41 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135388685","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}
The ichnogenus Oichnus Bromley (= small round holes) is uncommon between the Carboniferous and Triassic. Fossil crinoids from Salthill Quarry, Lancashire, England (Mississippian, Chadian) were uncommonly infested by pits assigned to Oichnus paraboloides Bromley. These may be solitary in the disparid Synbathocrinus conicus Phillips or gregarious in the monobathrid Amphoracrinus gilbertsoni (Miller) and certain pluricolumnals. The infesting organisms were not predatory; the pits were certainly protective domiciles and harvesting of plankton may be considered parasitic on the host’s food source. The two contrasting habits of O. paraboloides suggests that these identical pits were produced by two different species with contrasting habits. The organisms that produced solitary O. paraboloides were likely reproducing by shedding their gametes into the water column. In contrast, gregariousness may have been necessary of an organism that reproduced by copulation, a habit similar to extant balanid barnacles.
{"title":"Palaeoecology of Small Round Holes in Mississippian Crinoids: Salthill Quarry, Clitheroe, UK","authors":"S. Donovan","doi":"10.1353/ijes.0.a904063","DOIUrl":"https://doi.org/10.1353/ijes.0.a904063","url":null,"abstract":"The ichnogenus Oichnus Bromley (= small round holes) is uncommon between the Carboniferous and Triassic. Fossil crinoids from Salthill Quarry, Lancashire, England (Mississippian, Chadian) were uncommonly infested by pits assigned to Oichnus paraboloides Bromley. These may be solitary in the disparid Synbathocrinus conicus Phillips or gregarious in the monobathrid Amphoracrinus gilbertsoni (Miller) and certain pluricolumnals. The infesting organisms were not predatory; the pits were certainly protective domiciles and harvesting of plankton may be considered parasitic on the host’s food source. The two contrasting habits of O. paraboloides suggests that these identical pits were produced by two different species with contrasting habits. The organisms that produced solitary O. paraboloides were likely reproducing by shedding their gametes into the water column. In contrast, gregariousness may have been necessary of an organism that reproduced by copulation, a habit similar to extant balanid barnacles.","PeriodicalId":35911,"journal":{"name":"Irish Journal of Earth Sciences","volume":"1 1","pages":"-"},"PeriodicalIF":0.0,"publicationDate":"2023-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49352207","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}
Gyracanthid fish spines are described in detail for the first time from the Pennsylvanian (Langsettian)-aged Jarrow Assemblage in southeast Ireland. The spines are divided into pectoral, pelvic and anal spine morphotypes. The Jarrow gyracanthid is assigned to Gyracanthus sp. based on the morphology of its pectoral spines, which display U-shaped transections that possess ornament ridges on the exsertion area that do not change orientation distally along the length of the spine.
{"title":"Diverse Gyracanthus Spine Morphologies From the Jarrow Assemblage (Pennsylvanian), County Kilkenny, Ireland","authors":"Aodhán Ó Gogáin","doi":"10.1353/ijes.0.0007","DOIUrl":"https://doi.org/10.1353/ijes.0.0007","url":null,"abstract":"Gyracanthid fish spines are described in detail for the first time from the Pennsylvanian (Langsettian)-aged Jarrow Assemblage in southeast Ireland. The spines are divided into pectoral, pelvic and anal spine morphotypes. The Jarrow gyracanthid is assigned to Gyracanthus sp. based on the morphology of its pectoral spines, which display U-shaped transections that possess ornament ridges on the exsertion area that do not change orientation distally along the length of the spine.","PeriodicalId":35911,"journal":{"name":"Irish Journal of Earth Sciences","volume":"1 1","pages":"-"},"PeriodicalIF":0.0,"publicationDate":"2022-12-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66358615","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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