Pub Date : 2020-01-24DOI: 10.1080/11035897.2019.1701547
A. Holmqvist, C. Alwmark, H. Dypvik, O. Nilsen
ABSTRACT The origin of the more than 100 km wide Lycksele ring structure in Sweden has puzzled geoscientists for years. In this short note we present results from field analysis, detailed sampling and laboratory analysis executed in search for evidence of an impact, e.g. shatter cones and shock features in minerals. Both approaches gave negative results and consequently an impact origin could neither be confirmed nor rejected. The circular structure of the Lycksele ring and its central uplift are, however, typical features of large, complex impact structures.
{"title":"The Lycksele ring structure – still no proof of an impact origin","authors":"A. Holmqvist, C. Alwmark, H. Dypvik, O. Nilsen","doi":"10.1080/11035897.2019.1701547","DOIUrl":"https://doi.org/10.1080/11035897.2019.1701547","url":null,"abstract":"ABSTRACT The origin of the more than 100 km wide Lycksele ring structure in Sweden has puzzled geoscientists for years. In this short note we present results from field analysis, detailed sampling and laboratory analysis executed in search for evidence of an impact, e.g. shatter cones and shock features in minerals. Both approaches gave negative results and consequently an impact origin could neither be confirmed nor rejected. The circular structure of the Lycksele ring and its central uplift are, however, typical features of large, complex impact structures.","PeriodicalId":55094,"journal":{"name":"Gff","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2020-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/11035897.2019.1701547","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48517588","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 : 2020-01-24DOI: 10.1080/11035897.2019.1708451
A. Gubanov, J. R. Ebbestad, P. Männik, O. Bogolepova
ABSTRACT Jinonicella kolebabai Pokorný, 1978, a small problematic “mollusc” of unknown origin is described from the early Silurian (early to mid Llandovery) of east Siberia. This is the first record of Jinonicella from Siberia. Previous Silurian records of Jinonicella were from the late Llandovery (Telychian) of North America and the Wenlock to Ludlow of Europe (Bohemia, Gotland and the Carnic Alps of Austria). Jinonicella shows a wide range of geographic and stratigraphic distribution. It was reported from three palaeocontinents and several smaller terranes. It also demonstrates adaptation to different environments from shallow to deep-water settings, and spans several climatic zones from equatorial to temperate belts. The wide distribution and adaptation to a broad range of environments allow Jinonicella to subsist for about 100 my, i.e., from the Middle Ordovician to the Late Devonian surviving through two major extinction events.
{"title":"New data on the problematic mollusc Jinonicella from the early Silurian of east Siberia","authors":"A. Gubanov, J. R. Ebbestad, P. Männik, O. Bogolepova","doi":"10.1080/11035897.2019.1708451","DOIUrl":"https://doi.org/10.1080/11035897.2019.1708451","url":null,"abstract":"ABSTRACT Jinonicella kolebabai Pokorný, 1978, a small problematic “mollusc” of unknown origin is described from the early Silurian (early to mid Llandovery) of east Siberia. This is the first record of Jinonicella from Siberia. Previous Silurian records of Jinonicella were from the late Llandovery (Telychian) of North America and the Wenlock to Ludlow of Europe (Bohemia, Gotland and the Carnic Alps of Austria). Jinonicella shows a wide range of geographic and stratigraphic distribution. It was reported from three palaeocontinents and several smaller terranes. It also demonstrates adaptation to different environments from shallow to deep-water settings, and spans several climatic zones from equatorial to temperate belts. The wide distribution and adaptation to a broad range of environments allow Jinonicella to subsist for about 100 my, i.e., from the Middle Ordovician to the Late Devonian surviving through two major extinction events.","PeriodicalId":55094,"journal":{"name":"Gff","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2020-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/11035897.2019.1708451","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45888192","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 : 2020-01-24DOI: 10.1080/11035897.2019.1701548
E. Liñán, J. Gámez Vintaned, T. Palacios, R. Gozalo
ABSTRACT New trilobites from the upper part of the Pusa Formation (base of Cambrian Stage 3) in Central Spain are studied for their systematic and biostratigraphic significance. The trilobites Proabadiella toletana n. gen. et sp., Proabadiella vidalii n. gen. et sp., and a genus et species indet. are recorded with other fossils from the lower Ovetian regional Stage and archaeocyathan Zone I, which had, until now, provided only undetermined trilobites. The Proabadiella morphology is intermediate between that of the oldest genera of trilobites belonging to the families Abadiellidae and Bigotinidae, confirming the old age inferred for the new trilobites co-occurring with the archaeocyathan assemblage. Our findings permit presenting a new trilobite zonation for the lower Ovetian regional Stage (lower Cambrian Stage 3). A correlation is proposed with the other stratigraphically lowermost trilobites recorded globally.
摘要对西班牙中部普萨组上部(寒武系第三期基底)的新三叶虫进行了系统和生物地层学研究。三叶虫:托勒塔拟abadiella toletana n. gen. et sp.、维达拟abadiella vidalii n. gen. et sp.和一属一种indeindet。与其他来自下奥维梯地区阶段和古藻世第一区的化石记录在一起，到目前为止，这些化石只提供了尚未确定的三叶虫。原abadiella的形态介于Abadiellidae和Bigotinidae最古老的三叶虫属之间，证实了与古草藻组合共存的新三叶虫的古老推断。我们的发现为下奥维梯区域阶段(下寒武纪第3阶段)提出了一个新的三叶虫分区，并与全球记录的其他地层最底层三叶虫进行了对比。
{"title":"The lower Ovetian Stage (lower Cambrian Stage 3) trilobite zonation in Spain and correlation with West Gondwana","authors":"E. Liñán, J. Gámez Vintaned, T. Palacios, R. Gozalo","doi":"10.1080/11035897.2019.1701548","DOIUrl":"https://doi.org/10.1080/11035897.2019.1701548","url":null,"abstract":"ABSTRACT New trilobites from the upper part of the Pusa Formation (base of Cambrian Stage 3) in Central Spain are studied for their systematic and biostratigraphic significance. The trilobites Proabadiella toletana n. gen. et sp., Proabadiella vidalii n. gen. et sp., and a genus et species indet. are recorded with other fossils from the lower Ovetian regional Stage and archaeocyathan Zone I, which had, until now, provided only undetermined trilobites. The Proabadiella morphology is intermediate between that of the oldest genera of trilobites belonging to the families Abadiellidae and Bigotinidae, confirming the old age inferred for the new trilobites co-occurring with the archaeocyathan assemblage. Our findings permit presenting a new trilobite zonation for the lower Ovetian regional Stage (lower Cambrian Stage 3). A correlation is proposed with the other stratigraphically lowermost trilobites recorded globally.","PeriodicalId":55094,"journal":{"name":"Gff","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2020-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/11035897.2019.1701548","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44203838","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 : 2020-01-02DOI: 10.1080/11035897.2019.1631883
S. M. Bergström, B. Schmitz, F. Terfelt, M. Eriksson, P. Ahlberg
ABSTRACT The δ13C chemostratigraphy of five of the seven Ordovician global stages has been published previously but no such data have been available from the Floian GSSP and most of the Sandbian GSSP in Sweden. This lack of information has now been remedied by isotope data obtained from series of closely spaced shale samples collected from the Floian stratotype at Diabasbrottet in Västergötland and the Sandbian stratotype at Fågelsång in Scania. Although the bases of these stages cannot be precisely tied to levels of conspicuous δ13C excursions, that of the Floian Stage, which is marked by the appearance of the graptolite Tetragraptus approximatus, is between the closely spaced excursions named LTNICE and BFICE. The base of the Sandbian Stage, which is defined as the appearance level of the graptolite Nemagraptus gracilis, is just below a negative excursion previously known as the “Upper Kukruse Low”, which is nowadays known as the LSNICE. The relations between chemostratigraphy and graptolite and conodont biostratigraphy in the Swedish GSSPs and some coeval key sections in Baltoscandia, China, and America are briefly discussed. It is concluded that the data at hand indicate that there is good regional agreement in these relations.
{"title":"The δ13C chemostratigraphy of Ordovician global stage stratotypes: geochemical data from the Floian and Sandbian GSSPs in Sweden","authors":"S. M. Bergström, B. Schmitz, F. Terfelt, M. Eriksson, P. Ahlberg","doi":"10.1080/11035897.2019.1631883","DOIUrl":"https://doi.org/10.1080/11035897.2019.1631883","url":null,"abstract":"ABSTRACT The δ13C chemostratigraphy of five of the seven Ordovician global stages has been published previously but no such data have been available from the Floian GSSP and most of the Sandbian GSSP in Sweden. This lack of information has now been remedied by isotope data obtained from series of closely spaced shale samples collected from the Floian stratotype at Diabasbrottet in Västergötland and the Sandbian stratotype at Fågelsång in Scania. Although the bases of these stages cannot be precisely tied to levels of conspicuous δ13C excursions, that of the Floian Stage, which is marked by the appearance of the graptolite Tetragraptus approximatus, is between the closely spaced excursions named LTNICE and BFICE. The base of the Sandbian Stage, which is defined as the appearance level of the graptolite Nemagraptus gracilis, is just below a negative excursion previously known as the “Upper Kukruse Low”, which is nowadays known as the LSNICE. The relations between chemostratigraphy and graptolite and conodont biostratigraphy in the Swedish GSSPs and some coeval key sections in Baltoscandia, China, and America are briefly discussed. It is concluded that the data at hand indicate that there is good regional agreement in these relations.","PeriodicalId":55094,"journal":{"name":"Gff","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2020-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/11035897.2019.1631883","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48848432","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 : 2020-01-02DOI: 10.1080/11035897.2019.1708450
Å. Johansson, A. Karlsson
ABSTRACT The Herräng mafic dykes form an E-W-trending dyke swarm within the Bergslagen lithotectonic unit of the Svecofennian orogen in east-central Sweden. They intrude the Svecofennian supracrustal rocks and early-orogenic granitoids, but are themselves cut by late Svecofennian pegmatites, and have undergone Svecofennian amphibolite-facies metamorphism, leading to their classification as “intraorogenic” Svecofennian dykes. They can be assigned an age between 1870 and 1850 Ma, with metamorphism of the dykes dated at 1848 ± 13 Ma by U-Pb in titanite. Their current mineralogy is dominated by metamorphic plagioclase and amphibole, with variable amounts of quartz and biotite, and minor to accessory titanite, apatite, epidote, pyrite, magnetite, ilmenite and zircon. Textures range from massive to strongly foliated. Twenty samples of dyke rocks from three subareas in the Roslagen region, including the Herräng type area, range in composition from basaltic to andesitic with 47 to 60 wt% SiO2, broadly similar to the Dannemora dykes and the Avesta-Östhammar gabbros and diorites. Initial 87Sr/86Sr ratios (at 1870 Ma) varies between 0.7026 and 0.7038, corresponding to initial εSr between +5 and +21, and initial εNd between −0.4 and +1.3, suggesting a slightly enriched to mildly depleted mantle source, similar to other Svecofennian mafic rocks. The dykes dominantly show a calc-alkaline volcanic arc signature related to subduction. They formed during an extensional episode, possibly related to incipient back-arc spreading or subduction roll-back following the main early-orogenic subduction-related Svecofennian magmatism, but penecontemporaneous with amphibolite-facies metamorphism in the area.
{"title":"The “intraorogenic” Svecofennian Herräng mafic dyke swarm in east-central Sweden: age, geochemistry and tectonic significance","authors":"Å. Johansson, A. Karlsson","doi":"10.1080/11035897.2019.1708450","DOIUrl":"https://doi.org/10.1080/11035897.2019.1708450","url":null,"abstract":"ABSTRACT The Herräng mafic dykes form an E-W-trending dyke swarm within the Bergslagen lithotectonic unit of the Svecofennian orogen in east-central Sweden. They intrude the Svecofennian supracrustal rocks and early-orogenic granitoids, but are themselves cut by late Svecofennian pegmatites, and have undergone Svecofennian amphibolite-facies metamorphism, leading to their classification as “intraorogenic” Svecofennian dykes. They can be assigned an age between 1870 and 1850 Ma, with metamorphism of the dykes dated at 1848 ± 13 Ma by U-Pb in titanite. Their current mineralogy is dominated by metamorphic plagioclase and amphibole, with variable amounts of quartz and biotite, and minor to accessory titanite, apatite, epidote, pyrite, magnetite, ilmenite and zircon. Textures range from massive to strongly foliated. Twenty samples of dyke rocks from three subareas in the Roslagen region, including the Herräng type area, range in composition from basaltic to andesitic with 47 to 60 wt% SiO2, broadly similar to the Dannemora dykes and the Avesta-Östhammar gabbros and diorites. Initial 87Sr/86Sr ratios (at 1870 Ma) varies between 0.7026 and 0.7038, corresponding to initial εSr between +5 and +21, and initial εNd between −0.4 and +1.3, suggesting a slightly enriched to mildly depleted mantle source, similar to other Svecofennian mafic rocks. The dykes dominantly show a calc-alkaline volcanic arc signature related to subduction. They formed during an extensional episode, possibly related to incipient back-arc spreading or subduction roll-back following the main early-orogenic subduction-related Svecofennian magmatism, but penecontemporaneous with amphibolite-facies metamorphism in the area.","PeriodicalId":55094,"journal":{"name":"Gff","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2020-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/11035897.2019.1708450","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45744086","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 : 2020-01-02DOI: 10.1080/11035897.2019.1621376
J. S. Peel
ABSTRACT Two described specimens of the gastropod Bellerophon tenuifascia J. de C. Sowerby, 1824, from the Carboniferous (Asbian) of the Isle of Man, United Kingdom, preserve repaired injuries resulting from environmental breakage and failed, non-lethal, predatory attacks. Deep scars attributed to predatory attacks are assigned to the ichnofossil Caedichnus and were focused on the mid-dorsal area of the aperture. Abundant small-scale scallops and chipping of growth lamellae distributed around the apertural margin are mainly the result of environmental damage. A deeply incised injury in the aperture of one specimen was probably a fatal injury.
{"title":"Biogenic and abiogenic injuries in a Carboniferous Bellerophon (Gastropoda) from the Isle of Man, United Kingdom","authors":"J. S. Peel","doi":"10.1080/11035897.2019.1621376","DOIUrl":"https://doi.org/10.1080/11035897.2019.1621376","url":null,"abstract":"ABSTRACT Two described specimens of the gastropod Bellerophon tenuifascia J. de C. Sowerby, 1824, from the Carboniferous (Asbian) of the Isle of Man, United Kingdom, preserve repaired injuries resulting from environmental breakage and failed, non-lethal, predatory attacks. Deep scars attributed to predatory attacks are assigned to the ichnofossil Caedichnus and were focused on the mid-dorsal area of the aperture. Abundant small-scale scallops and chipping of growth lamellae distributed around the apertural margin are mainly the result of environmental damage. A deeply incised injury in the aperture of one specimen was probably a fatal injury.","PeriodicalId":55094,"journal":{"name":"Gff","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2020-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/11035897.2019.1621376","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48336113","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 : 2020-01-02DOI: 10.1080/11035897.2019.1655790
Oskar Bremer, E. Jarochowska, T. Märss
ABSTRACT A long history of geological research on the island of Gotland, Sweden, has resulted in a detailed biostratigraphy based on conodonts for the Gotland sedimentary succession, but the relation between the Hamra and Sundre formations, the youngest strata on southern Gotland, has remained poorly resolved. These formations have also remained relatively poorly described in terms of vertebrates compared to other parts of the succession. A survey of museum collections and newly sampled material reveal that the taxonomical compositions and richness of vertebrate faunas remain similar compared to the underlying Burgsvik Sandstone and Oolite members. However, the relative abundance of the respective groups changes: Paralogania ludlowiensis and rare osteostracan remains of Tahulaspis sp. only occur in samples from the lower Hamra Formation, while Thelodus sculptilis becomes more common in samples from Sundre Formation. Conodont and isotope data give support to previous suggestions that the Hamra and Sundre formations may be largely isochronous, and it is possible that the observed differences in vertebrate faunas reflect changes in depositional setting. This interval on Gotland has been suggested to represent a hiatus in the East Baltic sections, where younger strata show an increased importance of acanthodians in the vertebrate faunas. Gotland could therefore give insights into the early stages of this diversification of gnathostomes during late Silurian times. However, this has to be done in combination with data from other areas, as well as with a review and revision of the scale-based taxonomy of Silurian acanthodians from the Baltic Basin.
{"title":"Vertebrate remains and conodonts in the upper Silurian Hamra and Sundre formations of Gotland, Sweden","authors":"Oskar Bremer, E. Jarochowska, T. Märss","doi":"10.1080/11035897.2019.1655790","DOIUrl":"https://doi.org/10.1080/11035897.2019.1655790","url":null,"abstract":"ABSTRACT A long history of geological research on the island of Gotland, Sweden, has resulted in a detailed biostratigraphy based on conodonts for the Gotland sedimentary succession, but the relation between the Hamra and Sundre formations, the youngest strata on southern Gotland, has remained poorly resolved. These formations have also remained relatively poorly described in terms of vertebrates compared to other parts of the succession. A survey of museum collections and newly sampled material reveal that the taxonomical compositions and richness of vertebrate faunas remain similar compared to the underlying Burgsvik Sandstone and Oolite members. However, the relative abundance of the respective groups changes: Paralogania ludlowiensis and rare osteostracan remains of Tahulaspis sp. only occur in samples from the lower Hamra Formation, while Thelodus sculptilis becomes more common in samples from Sundre Formation. Conodont and isotope data give support to previous suggestions that the Hamra and Sundre formations may be largely isochronous, and it is possible that the observed differences in vertebrate faunas reflect changes in depositional setting. This interval on Gotland has been suggested to represent a hiatus in the East Baltic sections, where younger strata show an increased importance of acanthodians in the vertebrate faunas. Gotland could therefore give insights into the early stages of this diversification of gnathostomes during late Silurian times. However, this has to be done in combination with data from other areas, as well as with a review and revision of the scale-based taxonomy of Silurian acanthodians from the Baltic Basin.","PeriodicalId":55094,"journal":{"name":"Gff","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2020-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/11035897.2019.1655790","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"59720660","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 : 2020-01-02DOI: 10.1080/11035897.2019.1621370
J. Maletz, P. Ahlberg
ABSTRACT The upper Middle to basal Upper Ordovician succession (Darriwilian to Sandbian) of the Fågelsång-3 drill core provides new important information on the graptolite biostratigraphy of Scania, southern Sweden. The Scanian succession is known largely from drill cores and a few scattered outcrops exposing only parts of the interval. The Darriwilian Almelund Shale Formation overlies the Komstad Limestone Formation and has a thickness of more than 42 m in the Fågelsång-3 drill core. A seemingly complete succession through the Holmograptus lentus, Nicholsonograptus fasciculatus, Pterograptus elegans, Pseudamplexograptus distichus and Jiangxigraptus vagus biozones can be recognized. Some intervals are poorly documented by their respective graptolite faunas or show extensive post-depositional tectonic deformation. The Nemagraptus gracilis Biozone of earliest Sandbian age cannot be positively identified, even though fragments of Nemagraptus have been discovered in the uppermost part of the Almelund Shale below the Fågelsång Phosphorite Bed.
{"title":"Graptolite biostratigraphy of the Ordovician Almelund and Sularp Shale formations of the Fågelsång-3 drill core, Scania, Sweden","authors":"J. Maletz, P. Ahlberg","doi":"10.1080/11035897.2019.1621370","DOIUrl":"https://doi.org/10.1080/11035897.2019.1621370","url":null,"abstract":"ABSTRACT The upper Middle to basal Upper Ordovician succession (Darriwilian to Sandbian) of the Fågelsång-3 drill core provides new important information on the graptolite biostratigraphy of Scania, southern Sweden. The Scanian succession is known largely from drill cores and a few scattered outcrops exposing only parts of the interval. The Darriwilian Almelund Shale Formation overlies the Komstad Limestone Formation and has a thickness of more than 42 m in the Fågelsång-3 drill core. A seemingly complete succession through the Holmograptus lentus, Nicholsonograptus fasciculatus, Pterograptus elegans, Pseudamplexograptus distichus and Jiangxigraptus vagus biozones can be recognized. Some intervals are poorly documented by their respective graptolite faunas or show extensive post-depositional tectonic deformation. The Nemagraptus gracilis Biozone of earliest Sandbian age cannot be positively identified, even though fragments of Nemagraptus have been discovered in the uppermost part of the Almelund Shale below the Fågelsång Phosphorite Bed.","PeriodicalId":55094,"journal":{"name":"Gff","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2020-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/11035897.2019.1621370","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41839630","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 : 2019-10-02DOI: 10.1080/11035897.2019.1583685
G. Meinhold, K. Wemmer, Anette E. S. Högström, J. R. Ebbestad, S. Jensen, T. Palacios, M. Høyberget, Heda Agić, W. Taylor
ABSTRACT Fine-fraction K‒Ar dating and illite crystallinity determination were applied on a peculiar pale olive green shale sample from the upper Ediacaran Indreelva Member (Stáhpogieddi Formation, Vestertana Group, Gaissa Nappe Complex) of the Digermulen Peninsula in Finnmark, Arctic Norway, to constrain the age and metamorphic conditions of tectono-thermal overprint. The <2 and <0.2 µm grain-size fractions are almost purely illite and yielded an illite crystallinity (expressed as the Kübler index) of 0.215 Δ° 2θ and 0.228 ∆° 2θ and K‒Ar ages of 403.9 ± 4.2 and 391.5 ± 4.0 Ma, respectively. The K‒Ar ages are interpreted to present late-stage thermal overprint under low epizonal conditions along a localised shear zone, likely post-dating the peak of metamorphism and cleavage generation on the Digermulen Peninsula. Thus, a later tectono-metamorphic event related to the late stage of the Scandian orogeny is locally recorded in the Gaissa Nappe Complex of the Caledonides of Finnmark. This late Scandian event was probably caused by orogenic extensional collapse and appears to have extended at least into Mid-Devonian time.
{"title":"A late Caledonian tectono-thermal event in the Gaissa Nappe Complex, Arctic Norway: evidence from fine-fraction K‒Ar dating and illite crystallinity from the Digermulen Peninsula","authors":"G. Meinhold, K. Wemmer, Anette E. S. Högström, J. R. Ebbestad, S. Jensen, T. Palacios, M. Høyberget, Heda Agić, W. Taylor","doi":"10.1080/11035897.2019.1583685","DOIUrl":"https://doi.org/10.1080/11035897.2019.1583685","url":null,"abstract":"ABSTRACT Fine-fraction K‒Ar dating and illite crystallinity determination were applied on a peculiar pale olive green shale sample from the upper Ediacaran Indreelva Member (Stáhpogieddi Formation, Vestertana Group, Gaissa Nappe Complex) of the Digermulen Peninsula in Finnmark, Arctic Norway, to constrain the age and metamorphic conditions of tectono-thermal overprint. The <2 and <0.2 µm grain-size fractions are almost purely illite and yielded an illite crystallinity (expressed as the Kübler index) of 0.215 Δ° 2θ and 0.228 ∆° 2θ and K‒Ar ages of 403.9 ± 4.2 and 391.5 ± 4.0 Ma, respectively. The K‒Ar ages are interpreted to present late-stage thermal overprint under low epizonal conditions along a localised shear zone, likely post-dating the peak of metamorphism and cleavage generation on the Digermulen Peninsula. Thus, a later tectono-metamorphic event related to the late stage of the Scandian orogeny is locally recorded in the Gaissa Nappe Complex of the Caledonides of Finnmark. This late Scandian event was probably caused by orogenic extensional collapse and appears to have extended at least into Mid-Devonian time.","PeriodicalId":55094,"journal":{"name":"Gff","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2019-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/11035897.2019.1583685","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48926686","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 : 2019-09-30DOI: 10.1080/11035897.2019.1641548
V. Kostyleva, E. Shchepetova, A. Kotelnikov
ABSTRACT Four separate rhyolitic ash layers (from 0.3 to 2.5 m in thickness) and dispersed fine-sized pyroclastic material were found for the first time within Turonian-Coniacian volcaniclastic–siliciclastic coal-bearing Derevyannye Gory Formation. It was concluded the terrigenous sedimentation in the studied area was affected by long-term explosive volcanic activity during Turonian-Coniacian, and centres of eruptions were located closely to modern Novaya Sibir Island territory. Pyroclastics under consideration are petrochemically similar to Lower Albian volcanic rocks from Anjou archipelago (Kotelny Island). The centres of long-time Early Albian to Turonian-Coniacian subaerial volcanism were located probably in the modern territories of Zemlya Bunge and Faddeya islands, and along the northern edge of the Sannikov Strait.
{"title":"Upper Cretaceous rhyolitic ash beds from the Novaya Sibir Island (New Siberian Islands)","authors":"V. Kostyleva, E. Shchepetova, A. Kotelnikov","doi":"10.1080/11035897.2019.1641548","DOIUrl":"https://doi.org/10.1080/11035897.2019.1641548","url":null,"abstract":"ABSTRACT Four separate rhyolitic ash layers (from 0.3 to 2.5 m in thickness) and dispersed fine-sized pyroclastic material were found for the first time within Turonian-Coniacian volcaniclastic–siliciclastic coal-bearing Derevyannye Gory Formation. It was concluded the terrigenous sedimentation in the studied area was affected by long-term explosive volcanic activity during Turonian-Coniacian, and centres of eruptions were located closely to modern Novaya Sibir Island territory. Pyroclastics under consideration are petrochemically similar to Lower Albian volcanic rocks from Anjou archipelago (Kotelny Island). The centres of long-time Early Albian to Turonian-Coniacian subaerial volcanism were located probably in the modern territories of Zemlya Bunge and Faddeya islands, and along the northern edge of the Sannikov Strait.","PeriodicalId":55094,"journal":{"name":"Gff","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2019-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/11035897.2019.1641548","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46070214","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：