Pub Date : 2017-03-08DOI: 10.4138/ATLGEOL.2017.002
C. Álvarez-Vázquez, R. Wagner
As part of a larger project to revise the systematics of lower Westphalian floras of Nova Scotia and New Brunswick, the sphenopsid taxa are presently reviewed. We recognize 15 species, of which one, Annularia stopesiae , is new. Detailed synonymy lists allow a refinement of the stratigraphic and geographic ranges of these species. Scant attention has been paid previously to Canadian species in the European literature. For example, Annularia latifolia was described later from Europe as Annularia jongmansii . The identical composition of Westphalian floras from Canada and western Europe is striking.
{"title":"A revision of Annularia and Asterophyllites species from the lower Westphalian (Middle Pennsylvanian) of the Maritime Provinces of Canada","authors":"C. Álvarez-Vázquez, R. Wagner","doi":"10.4138/ATLGEOL.2017.002","DOIUrl":"https://doi.org/10.4138/ATLGEOL.2017.002","url":null,"abstract":"As part of a larger project to revise the systematics of lower Westphalian floras of Nova Scotia and New Brunswick, the sphenopsid taxa are presently reviewed. We recognize 15 species, of which one, Annularia stopesiae , is new. Detailed synonymy lists allow a refinement of the stratigraphic and geographic ranges of these species. Scant attention has been paid previously to Canadian species in the European literature. For example, Annularia latifolia was described later from Europe as Annularia jongmansii . The identical composition of Westphalian floras from Canada and western Europe is striking.","PeriodicalId":49235,"journal":{"name":"Atlantic Geology","volume":"53 1","pages":"017-062"},"PeriodicalIF":1.6,"publicationDate":"2017-03-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49016571","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-02-08DOI: 10.4138/ATLGEOL.2017.001
Olivia A. King, Randall F. Miller, M. Stimson
The Campbellton Formation has long been known to yield a fossil assemblage of Devonian (Emsian) fish and eurypterids at its westernmost exposure near Campbellton and Atholville, and a well described flora and early land animal fauna toward its easternmost exposure near Dalhousie Junction. Although the body fossil assemblage (paleobotany, vertebrate and invertebrate paleontology), paleoecology and paleoenvironmental context of the formation have been extensively studied, ichnofossils are rare and have not been described previously. Fossils from the vertebrate and eurypterid bearing ‘Atholville Beds’ contain a low diversity ichnofossil assemblage represented by three ichnotaxa: Monomorphichnus , ? Taenidium and Helminthoidichnites . Monomorphichnus is proposed here as being produced by the produced by the activity of the eurypterid Pterygotus anglicus .
{"title":"Ichnology of the Devonian (Emsian) Campbellton Formation, New Brunswick, Canada","authors":"Olivia A. King, Randall F. Miller, M. Stimson","doi":"10.4138/ATLGEOL.2017.001","DOIUrl":"https://doi.org/10.4138/ATLGEOL.2017.001","url":null,"abstract":"The Campbellton Formation has long been known to yield a fossil assemblage of Devonian (Emsian) fish and eurypterids at its westernmost exposure near Campbellton and Atholville, and a well described flora and early land animal fauna toward its easternmost exposure near Dalhousie Junction. Although the body fossil assemblage (paleobotany, vertebrate and invertebrate paleontology), paleoecology and paleoenvironmental context of the formation have been extensively studied, ichnofossils are rare and have not been described previously. Fossils from the vertebrate and eurypterid bearing ‘Atholville Beds’ contain a low diversity ichnofossil assemblage represented by three ichnotaxa: Monomorphichnus , ? Taenidium and Helminthoidichnites . Monomorphichnus is proposed here as being produced by the produced by the activity of the eurypterid Pterygotus anglicus .","PeriodicalId":49235,"journal":{"name":"Atlantic Geology","volume":"53 1","pages":"001-015"},"PeriodicalIF":1.6,"publicationDate":"2017-02-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41800810","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-01-13DOI: 10.4138/ATLGEOL.2016.013
P. Getty
Characters differentiating the arthropod trackway Bifurculapes from the similar ichnogenera Lithographus and Copeza include the position, arrangement and orientation of the tracks within the series. Of the five species of Bifurculapes originally described, only Bifurculapes laqueatus and Bifurculapes scolopendroideus are recognized herein; the other three ichnospecies are considered to be nomina dubia or junior subjective synonyms of Bifurculapes laqueatus . Two new specimens, recovered from the Early Jurassic East Berlin Formation of the Hartford Basin in Holyoke, Massachusetts, represent only the second unequivocal occurrence of the ichnogenus outside of the Deerfield Basin. Bifurculapes is currently known only from the Early Jurassic.
{"title":"Bifurculapes Hitchcock 1858: a revision of the ichnogenus","authors":"P. Getty","doi":"10.4138/ATLGEOL.2016.013","DOIUrl":"https://doi.org/10.4138/ATLGEOL.2016.013","url":null,"abstract":"Characters differentiating the arthropod trackway Bifurculapes from the similar ichnogenera Lithographus and Copeza include the position, arrangement and orientation of the tracks within the series. Of the five species of Bifurculapes originally described, only Bifurculapes laqueatus and Bifurculapes scolopendroideus are recognized herein; the other three ichnospecies are considered to be nomina dubia or junior subjective synonyms of Bifurculapes laqueatus . Two new specimens, recovered from the Early Jurassic East Berlin Formation of the Hartford Basin in Holyoke, Massachusetts, represent only the second unequivocal occurrence of the ichnogenus outside of the Deerfield Basin. Bifurculapes is currently known only from the Early Jurassic.","PeriodicalId":49235,"journal":{"name":"Atlantic Geology","volume":"52 1","pages":"247-255"},"PeriodicalIF":1.6,"publicationDate":"2017-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45824630","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-11-26DOI: 10.4138/ATLGEOL.2016.011
S. Donovan, Randall F. Miller
The New Brunswick Museum’s collection of Silurian crinoids from eastern Canada is small, and includes specimens from New Brunswick, Quebec and Nova Scotia. Material considered herein is, with one exception, from New Brunswick. Included are: the cladid Syndetocrinus dartae (Upper Silurian of Quebec); the camerates Scyphocrinites sp. (Pridoli or Lochkovian) and camerate crinoid arms gen. et sp. indet. (Lower Silurian); columnal morphotaxa Floricrinus (col.) sp. (Ludlow or Pridoli) and Lanxocolumnus (col.) sp. cf. L. chaleurensis Donovan and Keighley (probably Llandovery, Telychian); distal dendritic radicular attachments (Ludlow or Pridoli); and disarticulated brachials (Ludlow or Pridoli). ἀe fossil record of crinoids from the Silurian of New Brunswick appears depauperate, but this most likely reḀects the poor preservation of the specimens (commonly disarticulated and moldic) and the lack of interest shown by collectors. ἀe only remedy for this problem would be either discovery of a crinoid Lagerstatte, which would be attractive to collectors, or a focused campaign of collecting of disarticulated material from multiple outcrops.
{"title":"Silurian crinoids of the New Brunswick Museum, Saint John, Canada","authors":"S. Donovan, Randall F. Miller","doi":"10.4138/ATLGEOL.2016.011","DOIUrl":"https://doi.org/10.4138/ATLGEOL.2016.011","url":null,"abstract":"The New Brunswick Museum’s collection of Silurian crinoids from eastern Canada is small, and includes specimens from New Brunswick, Quebec and Nova Scotia. Material considered herein is, with one exception, from New Brunswick. Included are: the cladid Syndetocrinus dartae (Upper Silurian of Quebec); the camerates Scyphocrinites sp. (Pridoli or Lochkovian) and camerate crinoid arms gen. et sp. indet. (Lower Silurian); columnal morphotaxa Floricrinus (col.) sp. (Ludlow or Pridoli) and Lanxocolumnus (col.) sp. cf. L. chaleurensis Donovan and Keighley (probably Llandovery, Telychian); distal dendritic radicular attachments (Ludlow or Pridoli); and disarticulated brachials (Ludlow or Pridoli). ἀe fossil record of crinoids from the Silurian of New Brunswick appears depauperate, but this most likely reḀects the poor preservation of the specimens (commonly disarticulated and moldic) and the lack of interest shown by collectors. ἀe only remedy for this problem would be either discovery of a crinoid Lagerstatte, which would be attractive to collectors, or a focused campaign of collecting of disarticulated material from multiple outcrops.","PeriodicalId":49235,"journal":{"name":"Atlantic Geology","volume":"21 1","pages":"223-236"},"PeriodicalIF":1.6,"publicationDate":"2016-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70755297","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-11-10DOI: 10.4138/ATLGEOL.2016.010
S. Donovan, D. Keighley
Silurian strata of Atlantic Canada and southern Quebec locally preserve common fossil crinoids, albeit mostly as disarticulated remains. New crinoids from the Chaleurs Group, West Point Formation (Ludlow to Pridoli?; Upper Silurian) of the Gaspe Peninsula include Iocrinus ? maennili (Yeltysheva) (otherwise known from the Katian of Estonia), Bystrowicrinus (col.) depressus sp. nov. and Cyclocyclicus (col.) sp. aἀ. C. (col.) echinus Donovan. On the basis of both its gross morphology and stratigraphic position, Iocrinus ? maennili is unlikely to be an iocrinid disparid, a family that became extinct at the end of the Ordovician. The trivial name has hitherto been erroneously spelled as mannili , mannili and mjannili . Most specimens of the common Bystrowicrinus (col.) depressus appear cyclocyclic because the pentastellate lumen occurs in a deeply sunken claustrum that is commonly occluded by sediment; clean specimens are highly distinctive. Cyclocyclicus (col.) sp. aἀ. C. (col.) echinus is similar to a species known from the Katian of North Wales. Taken together, this assemblage is more reminiscent of Katian strata (Upper Ordovician). Ḁis is problematic given the current mapping of the outcrop as West Point Formation (Upper Silurian), suggesting further stratigraphic studies in the area are required.
{"title":"Fossil crinoids from the basal West Point Formation (Silurian), southeast Gaspé Peninsula, Québec, eastern Canada","authors":"S. Donovan, D. Keighley","doi":"10.4138/ATLGEOL.2016.010","DOIUrl":"https://doi.org/10.4138/ATLGEOL.2016.010","url":null,"abstract":"Silurian strata of Atlantic Canada and southern Quebec locally preserve common fossil crinoids, albeit mostly as disarticulated remains. New crinoids from the Chaleurs Group, West Point Formation (Ludlow to Pridoli?; Upper Silurian) of the Gaspe Peninsula include Iocrinus ? maennili (Yeltysheva) (otherwise known from the Katian of Estonia), Bystrowicrinus (col.) depressus sp. nov. and Cyclocyclicus (col.) sp. aἀ. C. (col.) echinus Donovan. On the basis of both its gross morphology and stratigraphic position, Iocrinus ? maennili is unlikely to be an iocrinid disparid, a family that became extinct at the end of the Ordovician. The trivial name has hitherto been erroneously spelled as mannili , mannili and mjannili . Most specimens of the common Bystrowicrinus (col.) depressus appear cyclocyclic because the pentastellate lumen occurs in a deeply sunken claustrum that is commonly occluded by sediment; clean specimens are highly distinctive. Cyclocyclicus (col.) sp. aἀ. C. (col.) echinus is similar to a species known from the Katian of North Wales. Taken together, this assemblage is more reminiscent of Katian strata (Upper Ordovician). Ḁis is problematic given the current mapping of the outcrop as West Point Formation (Upper Silurian), suggesting further stratigraphic studies in the area are required.","PeriodicalId":49235,"journal":{"name":"Atlantic Geology","volume":"52 1","pages":"211-222"},"PeriodicalIF":1.6,"publicationDate":"2016-11-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70755226","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-10-24DOI: 10.4138/ATLGEOL.2016.009
Z. Azadbakht, C. McFarlane, D. Lentz
The South Nepisiguit River Plutonic Suite consists of various phases of felsic to mafic plutonic rocks of early Devonian age in northern New Brunswick. The felsic portion of this intrusive suite includes a large pluton of homogeneous, peraluminous biotite granite (the Mount Elizabeth Granite), which is flanked on its western side by the alkaline Mount LaTour Granite. New in situ and mineral separate U-Pb Laser Ablation-Inductively Coupled Plasma Mass Spectro -m etry analyses of monazite and zircon grains from both sides of the suite define a crystallization age of 417.3 ± 0.96 Ma for the Mount Elizabeth Granite and 417.7 ± 4.4 Ma for the Mount LaTour Granite. The new data confirm previous geochronological work and indicate a close temporal relationship between these felsic phases of this plutonic suite.
{"title":"Precise U-Pb ages for the cogenetic alkaline Mount LaTour and peraluminous Mount Elizabeth granites of the South Nepisiguit River Plutonic Suite, northern New Brunswick, Canada","authors":"Z. Azadbakht, C. McFarlane, D. Lentz","doi":"10.4138/ATLGEOL.2016.009","DOIUrl":"https://doi.org/10.4138/ATLGEOL.2016.009","url":null,"abstract":"The South Nepisiguit River Plutonic Suite consists of various phases of felsic to mafic plutonic rocks of early Devonian age in northern New Brunswick. The felsic portion of this intrusive suite includes a large pluton of homogeneous, peraluminous biotite granite (the Mount Elizabeth Granite), which is flanked on its western side by the alkaline Mount LaTour Granite. New in situ and mineral separate U-Pb Laser Ablation-Inductively Coupled Plasma Mass Spectro -m etry analyses of monazite and zircon grains from both sides of the suite define a crystallization age of 417.3 ± 0.96 Ma for the Mount Elizabeth Granite and 417.7 ± 4.4 Ma for the Mount LaTour Granite. The new data confirm previous geochronological work and indicate a close temporal relationship between these felsic phases of this plutonic suite.","PeriodicalId":49235,"journal":{"name":"Atlantic Geology","volume":"52 1","pages":"189-210"},"PeriodicalIF":1.6,"publicationDate":"2016-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70755124","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-06-30DOI: 10.4138/ATLGEOL.2016.008
D. P. West, D. Bradley, R. Coish
The Litchfield pluton is a poorly exposed 7 km 2 composite alkalic intrusive complex that cuts previously deformed and metamorphosed Silurian turbidites in south-central Maine. The pluton includes a variety of alkaline syenites, including the type locality of “litchfieldite”, a coarse-grained cancrinite, sodalite, and lepidomelane bearing nepheline syenite first recognized over 150 years ago and common in many petrologic collections. A new U-Pb zircon age of 321 ± 2 Ma from the nepheline syenite is interpreted to represent the crystallization age of the plutonic complex. A new biotite 40 Ar/ 39 Ar age of 239 ± 1 Ma from the syenite is similar to previously published mica ages from the surrounding country rocks and dates the time of regional cooling in the area below ~ 300°C. Whole rock geochemical analyses from rocks of the Litchfield pluton are compatible with strongly alkaline A-type granitoid rocks that formed in a within plate or continental rift tectonic setting. The age and geochemical characteristics of the alkalic igneous rocks near Litchfield are consistent with a model that invokes the generation of a small volume of alkalic magma beneath south-central Maine during a period of Carboniferous transcurrent tectonism in the northern Appalachian orogen.
{"title":"The Litchfield Pluton in South-Central Maine: Carboniferous Alkalic Magmatism in northern New England, USA","authors":"D. P. West, D. Bradley, R. Coish","doi":"10.4138/ATLGEOL.2016.008","DOIUrl":"https://doi.org/10.4138/ATLGEOL.2016.008","url":null,"abstract":"The Litchfield pluton is a poorly exposed 7 km 2 composite alkalic intrusive complex that cuts previously deformed and metamorphosed Silurian turbidites in south-central Maine. The pluton includes a variety of alkaline syenites, including the type locality of “litchfieldite”, a coarse-grained cancrinite, sodalite, and lepidomelane bearing nepheline syenite first recognized over 150 years ago and common in many petrologic collections. A new U-Pb zircon age of 321 ± 2 Ma from the nepheline syenite is interpreted to represent the crystallization age of the plutonic complex. A new biotite 40 Ar/ 39 Ar age of 239 ± 1 Ma from the syenite is similar to previously published mica ages from the surrounding country rocks and dates the time of regional cooling in the area below ~ 300°C. Whole rock geochemical analyses from rocks of the Litchfield pluton are compatible with strongly alkaline A-type granitoid rocks that formed in a within plate or continental rift tectonic setting. The age and geochemical characteristics of the alkalic igneous rocks near Litchfield are consistent with a model that invokes the generation of a small volume of alkalic magma beneath south-central Maine during a period of Carboniferous transcurrent tectonism in the northern Appalachian orogen.","PeriodicalId":49235,"journal":{"name":"Atlantic Geology","volume":"52 1","pages":"169-187"},"PeriodicalIF":1.6,"publicationDate":"2016-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70755064","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-04-29DOI: 10.4138/ATLGEOL.2016.007
Reginald A. Wilson, S. Kamo
The central part of the Central plutonic belt in New Brunswick is underlain by numerous plutons of calc-alkaline, foliated and unfoliated granite that intrude Cambrian to Early Ordovician metasedimentary rocks. U-Pb (zircon) dating demonstrates that granites range in age from Middle Ordovician to Late Devonian, although most are late Silurian to Early Devonian. An age of 467 ± 7 Ma has been obtained on the foliated McKiel Lake Granite, whereas unfoliated intrusions yield ages of 423.2 ± 3.2 Ma (Bogan Brook Granodiorite), 420.7 +1.8/-2.0 Ma (Nashwaak Granite), 419.0 ± 0.5 Ma (Redstone Mountain Granite), 416.1 ± 0.5 Ma (Beadle Mountain Granite), 415.8 ± 0.3 Ma (Juniper Barren Granite), 409.7 ± 0.5 Ma (Lost Lake Granite), and 380.6 ± 0.3 Ma (Burnthill Granite). All plutons exhibit mixed arc-like and within-plate geochemical signatures, although the Redstone Mountain and Burnthill granites are dominantly of within-plate type. Trace element data reveal a close overall geochemical similarity between Ordovician and Silurian – Devonian plutons, indicating that all were generated by partial melting of the same crustal source. Late Silurian to Early Devonian plutons mainly comprise biotite and/or muscovite-bearing, peraluminous granite and are considered prospective for granophile-element mineralization. All plutons contain Sn well in excess of the granite global average abundance, and several contain average tin values comparable to productive stanniferous granites elsewhere. The Burnthill, Lost Lake, Beadle Mountain, and Nashwaak granites are geochemically most evolved and enriched in Sn and W. The Burnthill Granite in particular has experienced late-stage hydrothermal processes that have resulted in local enrichments of these elements.
新不伦瑞克省中央深部岩体带的中部为大量侵入寒武纪至早奥陶世变质沉积岩的钙碱性、片理和非片理花岗岩岩体。U-Pb(锆石)测年表明，花岗岩的年龄范围为中奥陶世至晚泥盆世，但大部分为晚志留世至早泥盆世。McKiel湖花岗岩的年龄为467±7 Ma，而非叶理岩体的年龄为423.2±3.2 Ma (Bogan Brook花岗闪长岩)、420.7±1.8/-2.0 Ma (Nashwaak花岗岩)、419.0±0.5 Ma (Redstone Mountain花岗岩)、416.1±0.5 Ma (Beadle Mountain花岗岩)、415.8±0.3 Ma (Juniper Barren花岗岩)、409.7±0.5 Ma (Lost Lake花岗岩)和380.6±0.3 Ma (Burnthill花岗岩)。所有岩体均表现出弧状和板内混合地球化学特征，但红石山和burnhill花岗岩以板内型为主。微量元素数据显示，奥陶系和志留系—泥盆系岩体在整体地球化学上具有密切的相似性，表明它们都是由同一地壳源的部分熔融作用产生的。晚志留世至早泥盆世岩体主要由黑云母和/或含白云母的过铝质花岗岩组成，被认为是嗜花岗元素成矿的远景区。所有岩体的锡含量都远远超过花岗岩的全球平均丰度，其中一些岩体的锡含量与其他地方的生产性含锡花岗岩相当。Burnthill花岗岩、Lost Lake花岗岩、Beadle Mountain花岗岩和Nashwaak花岗岩在地球化学上的演化和富集程度最高，特别是Burnthill花岗岩经历了晚期热液作用，导致这些元素在局部富集。
{"title":"Geochronology and lithogeochemistry of granitoid rocks from the central part of the Central plutonic belt, New Brunswick, Canada: implications for Sn-W-Mo exploration","authors":"Reginald A. Wilson, S. Kamo","doi":"10.4138/ATLGEOL.2016.007","DOIUrl":"https://doi.org/10.4138/ATLGEOL.2016.007","url":null,"abstract":"The central part of the Central plutonic belt in New Brunswick is underlain by numerous plutons of calc-alkaline, foliated and unfoliated granite that intrude Cambrian to Early Ordovician metasedimentary rocks. U-Pb (zircon) dating demonstrates that granites range in age from Middle Ordovician to Late Devonian, although most are late Silurian to Early Devonian. An age of 467 ± 7 Ma has been obtained on the foliated McKiel Lake Granite, whereas unfoliated intrusions yield ages of 423.2 ± 3.2 Ma (Bogan Brook Granodiorite), 420.7 +1.8/-2.0 Ma (Nashwaak Granite), 419.0 ± 0.5 Ma (Redstone Mountain Granite), 416.1 ± 0.5 Ma (Beadle Mountain Granite), 415.8 ± 0.3 Ma (Juniper Barren Granite), 409.7 ± 0.5 Ma (Lost Lake Granite), and 380.6 ± 0.3 Ma (Burnthill Granite). All plutons exhibit mixed arc-like and within-plate geochemical signatures, although the Redstone Mountain and Burnthill granites are dominantly of within-plate type. Trace element data reveal a close overall geochemical similarity between Ordovician and Silurian – Devonian plutons, indicating that all were generated by partial melting of the same crustal source. Late Silurian to Early Devonian plutons mainly comprise biotite and/or muscovite-bearing, peraluminous granite and are considered prospective for granophile-element mineralization. All plutons contain Sn well in excess of the granite global average abundance, and several contain average tin values comparable to productive stanniferous granites elsewhere. The Burnthill, Lost Lake, Beadle Mountain, and Nashwaak granites are geochemically most evolved and enriched in Sn and W. The Burnthill Granite in particular has experienced late-stage hydrothermal processes that have resulted in local enrichments of these elements.","PeriodicalId":49235,"journal":{"name":"Atlantic Geology","volume":"52 1","pages":"125-167"},"PeriodicalIF":1.6,"publicationDate":"2016-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70754891","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-04-10DOI: 10.4138/ATLGEOL.2016.006
P. Getty
The type and only specimen of the ichnospecies Megapezia longipes , from the Pennsylvanian Rhode Island Forma-tion of Plainville, Massachusetts, consists of two poorly defined tracks, one made by a manus and the other by a pes, rather than a single pedal imprint. Whereas the type species of Megapezia , Megapezia pineoi , has tetradactyl pedal imprints, the pes imprint of Megapezia longipes is pentadactyl, a feature that precludes assignment to this ichnogenus. Rather, the tracks share two characteristics with the ichnogenus Matthewichnus , namely elongate digits II and III on the manus, and a pes imprint oriented anterolaterally to the manus imprint, and are thus tentatively reassigned to that ichnogenus. Cf. Matthewichnus longipes is retained as a separate ichnospecies pending the collection of additional ma-terial that can be compared with other species within the ichnogenus. With the tentative reassignment of the Plainville tracks to Matthewichnus , Megapezia becomes monospecific and is no longer recorded in New England. The tracks are the first known occurrence of Matthewichnus from this region.
{"title":"Megapezia longipes Willard and Cleaves 1930 from the Pennsylvanian Rhode Island Formation of Massachusetts: ichnotaxonomic status","authors":"P. Getty","doi":"10.4138/ATLGEOL.2016.006","DOIUrl":"https://doi.org/10.4138/ATLGEOL.2016.006","url":null,"abstract":"The type and only specimen of the ichnospecies Megapezia longipes , from the Pennsylvanian Rhode Island Forma-tion of Plainville, Massachusetts, consists of two poorly defined tracks, one made by a manus and the other by a pes, rather than a single pedal imprint. Whereas the type species of Megapezia , Megapezia pineoi , has tetradactyl pedal imprints, the pes imprint of Megapezia longipes is pentadactyl, a feature that precludes assignment to this ichnogenus. Rather, the tracks share two characteristics with the ichnogenus Matthewichnus , namely elongate digits II and III on the manus, and a pes imprint oriented anterolaterally to the manus imprint, and are thus tentatively reassigned to that ichnogenus. Cf. Matthewichnus longipes is retained as a separate ichnospecies pending the collection of additional ma-terial that can be compared with other species within the ichnogenus. With the tentative reassignment of the Plainville tracks to Matthewichnus , Megapezia becomes monospecific and is no longer recorded in New England. The tracks are the first known occurrence of Matthewichnus from this region.","PeriodicalId":49235,"journal":{"name":"Atlantic Geology","volume":"52 1","pages":"119-124"},"PeriodicalIF":1.6,"publicationDate":"2016-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70754778","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：