Pub Date : 2019-09-30DOI: 10.1080/11035897.2019.1625073
V. Ershova, A. S. Ivleva, V. N. Podkovyrov, A. Khudoley, Petr V. Fedorov, D. Stockli, O. Anfinson, A. Maslov, V. Khubanov
ABSTRACT Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U–Pb detrital zircon isotope data from Mesoproterozoic to Lower Cambrian strata of the St Petersburg region are used to characterize the paleogeographic and tectonic evolution of the Baltica continent. We dated fifteen samples and divided them into three groups based on their distribution of detrital zircons. The first group (comprising Lower Mesoproterozoic rocks) is dominated by Early Mesoproterozoic and Late Paleoproterozoic zircons, mostly derived from weathering of proximal source region including rapakivi granites exposed across the neighboring Baltic Shield. The second group includes Upper Ediacaran samples (Redkino and Kotlin Regional Stages), with major zircon populations ranging in age between 1970–1850 and 1600–1550 Ma, respectively, correlating with magmatic and metamorphic events within the Svecofennian Orogeny and rapakivi granite igneous activity in the interior of Fennoscandia. The third group of samples, collected from both the uppermost Ediacaran and lowermost Cambrian deposits (Kotlin, Lontova and Dominopol Regional Stages), contains older Paleo-Mesoproterozoic zircons as well as Late Neoproterozoic-earliest Cambrian zircons, indicating a Timanian source area and exhibiting a age spectra similar to spectra for coeval rocks of the Scandinavian Caledonides. Therefore, we conclude that reworking and transport of continental detritus from the Timanian Orogen began during Late Ediacaran, earlier than previously supposed, with transport of Timanian detritus not only to the marginal part of Baltica (known from the Scandinavian Caledonides), but also to the distal interior of Baltica.
{"title":"Detrital zircon record of the Mesoproterozoic to Lower Cambrian sequences of NW Russia: implications for the paleogeography of the Baltic interior","authors":"V. Ershova, A. S. Ivleva, V. N. Podkovyrov, A. Khudoley, Petr V. Fedorov, D. Stockli, O. Anfinson, A. Maslov, V. Khubanov","doi":"10.1080/11035897.2019.1625073","DOIUrl":"https://doi.org/10.1080/11035897.2019.1625073","url":null,"abstract":"ABSTRACT Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U–Pb detrital zircon isotope data from Mesoproterozoic to Lower Cambrian strata of the St Petersburg region are used to characterize the paleogeographic and tectonic evolution of the Baltica continent. We dated fifteen samples and divided them into three groups based on their distribution of detrital zircons. The first group (comprising Lower Mesoproterozoic rocks) is dominated by Early Mesoproterozoic and Late Paleoproterozoic zircons, mostly derived from weathering of proximal source region including rapakivi granites exposed across the neighboring Baltic Shield. The second group includes Upper Ediacaran samples (Redkino and Kotlin Regional Stages), with major zircon populations ranging in age between 1970–1850 and 1600–1550 Ma, respectively, correlating with magmatic and metamorphic events within the Svecofennian Orogeny and rapakivi granite igneous activity in the interior of Fennoscandia. The third group of samples, collected from both the uppermost Ediacaran and lowermost Cambrian deposits (Kotlin, Lontova and Dominopol Regional Stages), contains older Paleo-Mesoproterozoic zircons as well as Late Neoproterozoic-earliest Cambrian zircons, indicating a Timanian source area and exhibiting a age spectra similar to spectra for coeval rocks of the Scandinavian Caledonides. Therefore, we conclude that reworking and transport of continental detritus from the Timanian Orogen began during Late Ediacaran, earlier than previously supposed, with transport of Timanian detritus not only to the marginal part of Baltica (known from the Scandinavian Caledonides), but also to the distal interior of Baltica.","PeriodicalId":55094,"journal":{"name":"Gff","volume":"141 1","pages":"279 - 288"},"PeriodicalIF":1.0,"publicationDate":"2019-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/11035897.2019.1625073","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48016787","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 : 2019-09-25DOI: 10.1080/11035897.2019.1622151
C. Knudsen, D. Gee, S. Sherlock, Li Yu
ABSTRACT The petrography, detrital zircon age distribution and 40Ar–39Ar ages of three samples from the Nagurskaya drill core of westernmost Franz Josef Land have been analyzed and are compared to similar rocks from the Lomonosov Ridge. The analyzed rocks, from near the base of the drill hole, consist of fine-grained psammitic to semipelitic schists, metamorphosed under greenschist-facies conditions. They are lithologically very similar to the recently analyzed metasediments from the Lomonosov Ridge. The detrital zircon age spectra of the samples from both the Lomonosov Ridge and beneath Franz Josef Land span the Meso- to Palaeoproterozoic with a main peak around 1.6 Ga, similar to lower Neoproterozoic metasedimentary rocks in East Greenland, on Svalbard and northern Norway, as well as from Cambrian sediments in Estonia and Silurian–Devonian sediments on Novaya Zemlya. Biotite in metasedimentary rocks from the Nagurskaya drill core indicate an Early Devonian 40Ar–39Ar metamorphic age of c. 400 Ma, possibly superimposed on an earlier, Ordovician history similar to that of the metasediments from the Lomonosov Ridge at 470 Ma. Previously published 40Ar–39Ar analyses of Nagurskaya muscovite yielded c. 600 Ma ages, characteristic of the Timanian Orogen. Together with the new biotite data, these isotope ages favor the interpretation that the Caledonian suture is located between Svalbard and Franz Josef Land, and the Caledonian deformation front between the latter and Novaya Zemlya.
摘要对Franz Josef Land最西部Nagurskaya钻孔岩芯的三个样品的岩石学、碎屑锆石年龄分布和40Ar–39Ar年龄进行了分析，并与罗蒙诺索夫山脊的类似岩石进行了比较。所分析的岩石位于钻孔底部附近，由细粒砂质至半泥质片岩组成，在绿片岩相条件下变质。它们在岩性上与最近分析的罗蒙诺索夫山脊的变质沉积物非常相似。罗蒙诺索夫山脊和Franz Josef Land下方样品的碎屑锆石年龄谱横跨中元古代至古元古代，主峰约1.6 Ga，类似于东格陵兰、斯瓦尔巴群岛和挪威北部的下新元古代变质沉积岩，以及爱沙尼亚的寒武纪沉积物和Novaya Zemlya的志留纪-泥盆纪沉积物。Nagurskaya钻孔岩芯中变质沉积岩中的黑云母表明，早泥盆纪40Ar–39Ar变质年龄约为400 Ma，可能叠加在更早的奥陶纪历史上，该历史类似于470 Ma罗蒙诺索夫山脊的变质沉积。之前发表的Nagurskaya-白云母40Ar-39Ar分析得出了约600 Ma的年龄，这是Timanian造山带的特征。结合新的黑云母数据，这些同位素年龄有利于解释喀里多尼亚缝合线位于斯瓦尔巴群岛和弗朗茨·约瑟夫地之间，以及后者和Novaya-Zemlya之间的喀里多尼亚变形锋。
{"title":"Caledonian metamorphism of metasediments from Franz Josef Land","authors":"C. Knudsen, D. Gee, S. Sherlock, Li Yu","doi":"10.1080/11035897.2019.1622151","DOIUrl":"https://doi.org/10.1080/11035897.2019.1622151","url":null,"abstract":"ABSTRACT The petrography, detrital zircon age distribution and 40Ar–39Ar ages of three samples from the Nagurskaya drill core of westernmost Franz Josef Land have been analyzed and are compared to similar rocks from the Lomonosov Ridge. The analyzed rocks, from near the base of the drill hole, consist of fine-grained psammitic to semipelitic schists, metamorphosed under greenschist-facies conditions. They are lithologically very similar to the recently analyzed metasediments from the Lomonosov Ridge. The detrital zircon age spectra of the samples from both the Lomonosov Ridge and beneath Franz Josef Land span the Meso- to Palaeoproterozoic with a main peak around 1.6 Ga, similar to lower Neoproterozoic metasedimentary rocks in East Greenland, on Svalbard and northern Norway, as well as from Cambrian sediments in Estonia and Silurian–Devonian sediments on Novaya Zemlya. Biotite in metasedimentary rocks from the Nagurskaya drill core indicate an Early Devonian 40Ar–39Ar metamorphic age of c. 400 Ma, possibly superimposed on an earlier, Ordovician history similar to that of the metasediments from the Lomonosov Ridge at 470 Ma. Previously published 40Ar–39Ar analyses of Nagurskaya muscovite yielded c. 600 Ma ages, characteristic of the Timanian Orogen. Together with the new biotite data, these isotope ages favor the interpretation that the Caledonian suture is located between Svalbard and Franz Josef Land, and the Caledonian deformation front between the latter and Novaya Zemlya.","PeriodicalId":55094,"journal":{"name":"Gff","volume":"141 1","pages":"295 - 307"},"PeriodicalIF":1.0,"publicationDate":"2019-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/11035897.2019.1622151","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49508822","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 : 2019-09-25DOI: 10.1080/11035897.2019.1633396
B. Coakley, Jeffery R Johnson, J. Beale, R. Ganley, M. Youngman
ABSTRACT Incremental improvements to the Arctic Gravity Project (AGP) grid have accumulated through the steady acquisition of marine gravity anomaly data in the Arctic Ocean and other data sets. The explosion of data collected to establish the Extended Continental Shelves of the Arctic coastal states has increased the available data in and around the Arctic Ocean. A consistent issue with the AGP grid has been a very irregular distribution of gravity anomaly data in Alaska. While parts of the state have been well-surveyed (e.g. the North Slope) much of this remote region has not. Access is difficult. Control points for gravity ties are non-existent. As a result, the anomalous field for Alaska has not been well determined. This may be changing due to the extensive airborne survey conducted by the US National Geodetic Survey. Nearly all of continental Alaska has been flown at ~6 km elevation with a 10 km line spacing as a part of the GRAV-D project. These data have been collected by a single group, using consistent procedures and the same equipment. These data form an ideal basis for a new gravity anomaly map for the State of Alaska. Using the new data, collected from ships and the airborne data collected through the GRAV-D project in conjunction with satellite and land data will substantially improve knowledge of the gravity field. All of the new data will be included in the updated AGP grid, which should be available in a year, updating the last release from 2008.
{"title":"Improving the Arctic Gravity Project grid and making a gravity anomaly map for the State of Alaska","authors":"B. Coakley, Jeffery R Johnson, J. Beale, R. Ganley, M. Youngman","doi":"10.1080/11035897.2019.1633396","DOIUrl":"https://doi.org/10.1080/11035897.2019.1633396","url":null,"abstract":"ABSTRACT Incremental improvements to the Arctic Gravity Project (AGP) grid have accumulated through the steady acquisition of marine gravity anomaly data in the Arctic Ocean and other data sets. The explosion of data collected to establish the Extended Continental Shelves of the Arctic coastal states has increased the available data in and around the Arctic Ocean. A consistent issue with the AGP grid has been a very irregular distribution of gravity anomaly data in Alaska. While parts of the state have been well-surveyed (e.g. the North Slope) much of this remote region has not. Access is difficult. Control points for gravity ties are non-existent. As a result, the anomalous field for Alaska has not been well determined. This may be changing due to the extensive airborne survey conducted by the US National Geodetic Survey. Nearly all of continental Alaska has been flown at ~6 km elevation with a 10 km line spacing as a part of the GRAV-D project. These data have been collected by a single group, using consistent procedures and the same equipment. These data form an ideal basis for a new gravity anomaly map for the State of Alaska. Using the new data, collected from ships and the airborne data collected through the GRAV-D project in conjunction with satellite and land data will substantially improve knowledge of the gravity field. All of the new data will be included in the updated AGP grid, which should be available in a year, updating the last release from 2008.","PeriodicalId":55094,"journal":{"name":"Gff","volume":"141 1","pages":"308 - 315"},"PeriodicalIF":1.0,"publicationDate":"2019-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/11035897.2019.1633396","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43493377","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 : 2019-09-06DOI: 10.1080/11035897.2019.1621371
Nikola Koglin, Solveig Estrada, A. Gerdes
ABSTRACT The Voykar Massif of the Polar Urals in Russia consists of an ultramafic complex (mantle section) in the northwest, followed by a late Cambrian to Silurian mafic complex (intra-oceanic primitive island arc) and early Devonian intrusive rocks of an evolved island arc to the southeast. These complexes represent tectonic nappes thrust over the East European continental margin during the late Palaeozoic Uralian Orogeny. LA-ICP-MS U-Pb dating of zircon grains (n = 42) from an antigorite-serpentinite lens within the mafic complex yielded a Concordia age of 542 ± 2 Ma with an age range of 549–527 Ma. Additionally, few grains contain inherited domains with ages between ~990 and 3277 Ma. Hafnium isotopic data of the main age group show 176Hf/177Hft from 0.28242 to 028249 and εHft ranging from +1.9 to −6.5. The evolved Hf isotope data and the trace-element composition of the zircon grains point to an involvement of a continental crustal component in the parental magma. The zircon grains originate from igneous rocks formed during the Timanian Orogeny that affected the East European margin in the latest Neoproterozoic. During the Timanian or Uralian Orogeny, the magmatic zircons were eroded and shallowly recycled into the serpentinised mantle above the subduction zone. Finally, Uralian thrusting led to juxtaposition and imbrication of the zircon-bearing serpentinite and intra-oceanic volcanic rocks of the mafic complex.
{"title":"Shallow reworking of magmatic zircon grains of latest Neoproterozoic (Timanian) age in serpentinite of the Voykar Massif, Polar Urals: new constraints from U-Pb isotopic data, and first trace elements and Lu-Hf isotopic data","authors":"Nikola Koglin, Solveig Estrada, A. Gerdes","doi":"10.1080/11035897.2019.1621371","DOIUrl":"https://doi.org/10.1080/11035897.2019.1621371","url":null,"abstract":"ABSTRACT The Voykar Massif of the Polar Urals in Russia consists of an ultramafic complex (mantle section) in the northwest, followed by a late Cambrian to Silurian mafic complex (intra-oceanic primitive island arc) and early Devonian intrusive rocks of an evolved island arc to the southeast. These complexes represent tectonic nappes thrust over the East European continental margin during the late Palaeozoic Uralian Orogeny. LA-ICP-MS U-Pb dating of zircon grains (n = 42) from an antigorite-serpentinite lens within the mafic complex yielded a Concordia age of 542 ± 2 Ma with an age range of 549–527 Ma. Additionally, few grains contain inherited domains with ages between ~990 and 3277 Ma. Hafnium isotopic data of the main age group show 176Hf/177Hft from 0.28242 to 028249 and εHft ranging from +1.9 to −6.5. The evolved Hf isotope data and the trace-element composition of the zircon grains point to an involvement of a continental crustal component in the parental magma. The zircon grains originate from igneous rocks formed during the Timanian Orogeny that affected the East European margin in the latest Neoproterozoic. During the Timanian or Uralian Orogeny, the magmatic zircons were eroded and shallowly recycled into the serpentinised mantle above the subduction zone. Finally, Uralian thrusting led to juxtaposition and imbrication of the zircon-bearing serpentinite and intra-oceanic volcanic rocks of the mafic complex.","PeriodicalId":55094,"journal":{"name":"Gff","volume":"141 1","pages":"253 - 262"},"PeriodicalIF":1.0,"publicationDate":"2019-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/11035897.2019.1621371","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47407756","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 : 2019-09-06DOI: 10.1080/11035897.2019.1621373
A. Prokopiev, V. Ershova, D. Stockli
ABSTRACT U–Pb dating of detrital zircons collected from the Middle–Upper Palaeozoic strata of the Prikolyma terrane (Verkhoyansk–Kolyma orogen) provide the first insight into provenance areas and the Middle–Late Palaeozoic geological history of the Russian Far East. Detrital zircon ages from the Lower–Middle Devonian sandstones group around 395–405 M (Emsian–Eifelian) which correlate well to trachyte of the Uvyazka zone and the Kedon Complex of the North Okhotsk active continental margin located on the Omolon terrane. Precambrian-aged zircons group around 1740–2080 and 2460–2800 Ma, respectively, suggesting possible sources within metamorphic rocks of the basement of the Omolon terrane or the Siberian Craton. The majority of the zircons from the Lower and Upper Carboniferous sandstones group around 333–375 Ma, suggesting that the principle source of the clastics were volcanic rocks and comagmatic felsic intrusions of the Kedon Complex of the North Okhotsk active continental margin. Our new data allow us to evaluate and revise the available palaeotectonic reconstructions of northeast Asia for the Devonian and Carboniferous.
{"title":"Provenance of the Devonian–Carboniferous clastics of the southern part of the Prikolyma terrane (Verkhoyansk–Kolyma orogen) based on U–Pb dating of detrital zircons","authors":"A. Prokopiev, V. Ershova, D. Stockli","doi":"10.1080/11035897.2019.1621373","DOIUrl":"https://doi.org/10.1080/11035897.2019.1621373","url":null,"abstract":"ABSTRACT U–Pb dating of detrital zircons collected from the Middle–Upper Palaeozoic strata of the Prikolyma terrane (Verkhoyansk–Kolyma orogen) provide the first insight into provenance areas and the Middle–Late Palaeozoic geological history of the Russian Far East. Detrital zircon ages from the Lower–Middle Devonian sandstones group around 395–405 M (Emsian–Eifelian) which correlate well to trachyte of the Uvyazka zone and the Kedon Complex of the North Okhotsk active continental margin located on the Omolon terrane. Precambrian-aged zircons group around 1740–2080 and 2460–2800 Ma, respectively, suggesting possible sources within metamorphic rocks of the basement of the Omolon terrane or the Siberian Craton. The majority of the zircons from the Lower and Upper Carboniferous sandstones group around 333–375 Ma, suggesting that the principle source of the clastics were volcanic rocks and comagmatic felsic intrusions of the Kedon Complex of the North Okhotsk active continental margin. Our new data allow us to evaluate and revise the available palaeotectonic reconstructions of northeast Asia for the Devonian and Carboniferous.","PeriodicalId":55094,"journal":{"name":"Gff","volume":"141 1","pages":"272 - 278"},"PeriodicalIF":1.0,"publicationDate":"2019-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/11035897.2019.1621373","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44879065","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 : 2019-09-06DOI: 10.1080/11035897.2019.1622150
A. Moiseev, M. Luchitskaya, S. Sokolov, B. Belyatsky
ABSTRACT Ediacaran and Permian‒Triassic stages of plagiogranite magmatism are distinguished for the Ust-Bel’sky and Algansky terranes of the West Koryak fold belt, NE Russia. The U‒Pb ages of Ediacaran plagiogranites are 556 ± 3 Ma (SIMS data) and 538 ± 7 Ma (LA–ICP–MS data), respectively, and 235 ± 2 Ma (SIMS data) for the Permian‒Triassic plagiogranites. The Ediacaran and Permian‒Triassic plagiogranites are low-K igneous rocks. Sr‒Nd isotopy and REE patterns of both plagiogranite suites allow suggesting their formation via partial melting of primary mantle material or fractional crystallization of basaltic magma. Ediacaran plagiogranites were formed in the oceanic arc setting contemporaneously with the volcanic-sedimentary complex of Otrozhnaya slice, Ust-Bel’sky terrane. Tuffaceous conglomerates in the lower part of this complex contain Ediacaran zircons with a peak age of 571 Ma. Formation of the Permian‒Triassic plagiogranites took place within the Ust-Bel’sky segment of the Koni‒Taigonos arc via partial melting of melanocratic ophiolite material in the accretionary structure of this arc or fractional crystallization of basaltic magma, melted from such substrate.
{"title":"Geodynamic setting of Ediacaran and Permian–Triassic plagiogranites of the Ust-Bel’sky and Algansky terranes, West Koryak fold belt, NE Russia: insights from U–Pb geochronology and geochemistry","authors":"A. Moiseev, M. Luchitskaya, S. Sokolov, B. Belyatsky","doi":"10.1080/11035897.2019.1622150","DOIUrl":"https://doi.org/10.1080/11035897.2019.1622150","url":null,"abstract":"ABSTRACT Ediacaran and Permian‒Triassic stages of plagiogranite magmatism are distinguished for the Ust-Bel’sky and Algansky terranes of the West Koryak fold belt, NE Russia. The U‒Pb ages of Ediacaran plagiogranites are 556 ± 3 Ma (SIMS data) and 538 ± 7 Ma (LA–ICP–MS data), respectively, and 235 ± 2 Ma (SIMS data) for the Permian‒Triassic plagiogranites. The Ediacaran and Permian‒Triassic plagiogranites are low-K igneous rocks. Sr‒Nd isotopy and REE patterns of both plagiogranite suites allow suggesting their formation via partial melting of primary mantle material or fractional crystallization of basaltic magma. Ediacaran plagiogranites were formed in the oceanic arc setting contemporaneously with the volcanic-sedimentary complex of Otrozhnaya slice, Ust-Bel’sky terrane. Tuffaceous conglomerates in the lower part of this complex contain Ediacaran zircons with a peak age of 571 Ma. Formation of the Permian‒Triassic plagiogranites took place within the Ust-Bel’sky segment of the Koni‒Taigonos arc via partial melting of melanocratic ophiolite material in the accretionary structure of this arc or fractional crystallization of basaltic magma, melted from such substrate.","PeriodicalId":55094,"journal":{"name":"Gff","volume":"141 1","pages":"241 - 252"},"PeriodicalIF":1.0,"publicationDate":"2019-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/11035897.2019.1622150","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49295037","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 : 2019-09-06DOI: 10.1080/11035897.2019.1621372
A. Khudoley, N. Sobolev, E. O. Petrov, V. Ershova, Alexander A. Makariev, E. Makarieva, C. Gaina, P. Sobolev
ABSTRACT Combined U–Pb detrital zircon dating of 21 samples, along with whole-rock chemical composition and Sm–Nd isotopic studies of 39 samples of Triassic and Jurassic rocks from Franz Josef Land and wells in the southern part of the Russian (eastern) Barents Sea, were analyzed for a reconnaissance provenance study. The similarity of detrital zircon age distributions was statistically assessed using the Kolmogorov–Smirnov (K–S) test and points to a common source area for the clastic material of Triassic to Middle Jurassic age. Uralian-age detrital zircons predominate in all samples, with a comparably smaller portion of Caledonian- and Timanian-age detrital zircons. The number of Palaeoproterozoic and Archean grains is very small and becomes significant only in a few Jurassic samples. εNd(t) values gradually decrease from −1.5 to +2.5 in Lower Triassic rocks, to −2.0 to −8.2 in Jurassic rocks, suggesting an increasing influence of ancient metamorphic basement erosion in the younger Jurassic rocks. High Co/Th ratios, suggesting the erosion of mafic rocks, were mainly recorded in Lower Triassic rocks, whereas increasing Th/Sc ratios, suggesting the erosion of felsic rocks, were recorded only in some uppermost Triassic and Jurassic rocks. We identify the Urals and, in addition during the Triassic, the basement of the West Siberian Basin as the main provenance for the studied clastic rocks. By contrast, only a small volume of fine-grained clastic detritus was derived from basement erosion of the East European Craton, which was characterized by a subdued relief during this time.
{"title":"A reconnaissance provenance study of Triassic–Jurassic clastic rocks of the Russian Barents Sea","authors":"A. Khudoley, N. Sobolev, E. O. Petrov, V. Ershova, Alexander A. Makariev, E. Makarieva, C. Gaina, P. Sobolev","doi":"10.1080/11035897.2019.1621372","DOIUrl":"https://doi.org/10.1080/11035897.2019.1621372","url":null,"abstract":"ABSTRACT Combined U–Pb detrital zircon dating of 21 samples, along with whole-rock chemical composition and Sm–Nd isotopic studies of 39 samples of Triassic and Jurassic rocks from Franz Josef Land and wells in the southern part of the Russian (eastern) Barents Sea, were analyzed for a reconnaissance provenance study. The similarity of detrital zircon age distributions was statistically assessed using the Kolmogorov–Smirnov (K–S) test and points to a common source area for the clastic material of Triassic to Middle Jurassic age. Uralian-age detrital zircons predominate in all samples, with a comparably smaller portion of Caledonian- and Timanian-age detrital zircons. The number of Palaeoproterozoic and Archean grains is very small and becomes significant only in a few Jurassic samples. εNd(t) values gradually decrease from −1.5 to +2.5 in Lower Triassic rocks, to −2.0 to −8.2 in Jurassic rocks, suggesting an increasing influence of ancient metamorphic basement erosion in the younger Jurassic rocks. High Co/Th ratios, suggesting the erosion of mafic rocks, were mainly recorded in Lower Triassic rocks, whereas increasing Th/Sc ratios, suggesting the erosion of felsic rocks, were recorded only in some uppermost Triassic and Jurassic rocks. We identify the Urals and, in addition during the Triassic, the basement of the West Siberian Basin as the main provenance for the studied clastic rocks. By contrast, only a small volume of fine-grained clastic detritus was derived from basement erosion of the East European Craton, which was characterized by a subdued relief during this time.","PeriodicalId":55094,"journal":{"name":"Gff","volume":"141 1","pages":"263 - 271"},"PeriodicalIF":1.0,"publicationDate":"2019-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/11035897.2019.1621372","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42846138","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 : 2019-07-03DOI: 10.1080/11035897.2019.1624978
R. Gabrielsen, O. Olesen, A. Braathen, J. Faleide, V. Baranwal, C. Lindholm
ABSTRACT The Listafjord–Drangedal Fault Complex is a central structure in the NE-SW-trending Agder–Telemark Lineament Zone that dominates the structural grain and topography of southernmost tip of Norway. The fault can be followed for a distance of more than 170 km from the shelf area off Listafjorden–Fedafjorden in Vest Agder county to Drangedal in Telemark county. It has been analyzed by the use of digital topographic, remote sensing and potential field data, supported by field investigations. At least seven separate left-stepping fault segments have been identified. These are characterized by numerous internal fault lenses, separate fault strands and fault splays, partly displaying contrasting fault attitude and style of deformation. The northeastern termination of the Listafjord–Drangedal Fault Complex consists of fanning fault branches (horse-tailing), whereas its southwestern termination is buried below sediments in the continental shelf and remains obscure. The fault rocks of the various fault segments include cataclasites and mylonites that in places are interlayered with zones of fault gouge. By tentative correlation to the Hunnedalen dyke system in Rogaland, the age of initiation for the Listafjord–Drangedal Fault Complex is suggested to be Late Proterozoic. Parts of the fault complex were affected by at least two stages of faulting including (dextral?) shear and top-to-the-SE extension. The latter stage is assumed to be of post-Caledonian age, and recent seismic activity suggests that this ancient structural grain is still seismically active.
{"title":"The Listafjorden–Drangedal Fault Complex of the Agder–Telemark Lineament Zone, southern Norway. A structural analysis based on remote sensing and potential field data","authors":"R. Gabrielsen, O. Olesen, A. Braathen, J. Faleide, V. Baranwal, C. Lindholm","doi":"10.1080/11035897.2019.1624978","DOIUrl":"https://doi.org/10.1080/11035897.2019.1624978","url":null,"abstract":"ABSTRACT The Listafjord–Drangedal Fault Complex is a central structure in the NE-SW-trending Agder–Telemark Lineament Zone that dominates the structural grain and topography of southernmost tip of Norway. The fault can be followed for a distance of more than 170 km from the shelf area off Listafjorden–Fedafjorden in Vest Agder county to Drangedal in Telemark county. It has been analyzed by the use of digital topographic, remote sensing and potential field data, supported by field investigations. At least seven separate left-stepping fault segments have been identified. These are characterized by numerous internal fault lenses, separate fault strands and fault splays, partly displaying contrasting fault attitude and style of deformation. The northeastern termination of the Listafjord–Drangedal Fault Complex consists of fanning fault branches (horse-tailing), whereas its southwestern termination is buried below sediments in the continental shelf and remains obscure. The fault rocks of the various fault segments include cataclasites and mylonites that in places are interlayered with zones of fault gouge. By tentative correlation to the Hunnedalen dyke system in Rogaland, the age of initiation for the Listafjord–Drangedal Fault Complex is suggested to be Late Proterozoic. Parts of the fault complex were affected by at least two stages of faulting including (dextral?) shear and top-to-the-SE extension. The latter stage is assumed to be of post-Caledonian age, and recent seismic activity suggests that this ancient structural grain is still seismically active.","PeriodicalId":55094,"journal":{"name":"Gff","volume":"141 1","pages":"200 - 215"},"PeriodicalIF":1.0,"publicationDate":"2019-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/11035897.2019.1624978","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41349916","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 : 2019-07-03DOI: 10.1080/11035897.2019.1636860
C. V. Rubinstein, V. Vajda
ABSTRACT The origin of land plants is one of the most important evolutionary events in Earth’s history. The mode and timing of the terrestrialization of plants remains debated and previous data indicate Gondwana to be the center of land-plant radiation at ~ 470–460 Ma. Here we present the oldest occurrences of trilete spores, probably the earliest traces of vascular land plants yet recorded. The spores occur in Ordovician, Sandbian (455 million years old) successions in central Sweden, once part of the paleocontinent Baltica. These strata are independently dated by marine microfossils (conodonts) and 206Pb/238U dating of volcanic ash deposits. Our discovery extends the record of trilete spores globally by ~8 million years, and for Baltica by ~25 million years. Additionally, cryptospore assemblages are identified revealing a diverse and stable mid-Ordovician (Darriwilian: ~ 460 Ma) vegetation of free-sporing plants. The formation of regolith substrates on land as a consequence of permanent plant cover must in turn have affected the marine biota. We link these early land plant spore occurrences to the extensive, nutrient-rich volcanic ash deposits and propose Baltica as the possible original region of the radiation of early land plants.
{"title":"Baltica cradle of early land plants? Oldest record of trilete spores and diverse cryptospore assemblages; evidence from Ordovician successions of Sweden","authors":"C. V. Rubinstein, V. Vajda","doi":"10.1080/11035897.2019.1636860","DOIUrl":"https://doi.org/10.1080/11035897.2019.1636860","url":null,"abstract":"ABSTRACT The origin of land plants is one of the most important evolutionary events in Earth’s history. The mode and timing of the terrestrialization of plants remains debated and previous data indicate Gondwana to be the center of land-plant radiation at ~ 470–460 Ma. Here we present the oldest occurrences of trilete spores, probably the earliest traces of vascular land plants yet recorded. The spores occur in Ordovician, Sandbian (455 million years old) successions in central Sweden, once part of the paleocontinent Baltica. These strata are independently dated by marine microfossils (conodonts) and 206Pb/238U dating of volcanic ash deposits. Our discovery extends the record of trilete spores globally by ~8 million years, and for Baltica by ~25 million years. Additionally, cryptospore assemblages are identified revealing a diverse and stable mid-Ordovician (Darriwilian: ~ 460 Ma) vegetation of free-sporing plants. The formation of regolith substrates on land as a consequence of permanent plant cover must in turn have affected the marine biota. We link these early land plant spore occurrences to the extensive, nutrient-rich volcanic ash deposits and propose Baltica as the possible original region of the radiation of early land plants.","PeriodicalId":55094,"journal":{"name":"Gff","volume":"141 1","pages":"181 - 190"},"PeriodicalIF":1.0,"publicationDate":"2019-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/11035897.2019.1636860","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45492090","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 : 2019-07-03DOI: 10.1080/11035897.2019.1621375
J. Botting, R. Yakupov
ABSTRACT Despite the recent discovery of abundant and diverse latest Ordovician sponges in China, early Silurian sponges are generally scarce, and non-lithistid, spiculate sponges remain poorly known. This is particularly true outside of a few well-studied regions, and monographic biases strongly influence the published record of the group. A new, well-preserved example of the spinose reticulosan Acutipuerilis from the Silurian of the southern Ural Mountains represents the first such fossil from this region and the first post-Ordovician asthenospongiid. Hexaradiate heteractinid spicules assigned to Toquimiella? sp. co-occur in the same rocks with fragments of other reticulosans including the reticulosan Plectoderma? sp., but no other fully articulated remains have been found. These three genera were previously known only from their type localities in Laurentia and Avalonia, in different environments, and the remarkable co-occurrence here raises the possibility of a change in sponge ecology and distribution following the Hirnantian Extinction.
{"title":"Acutipuerilis and other non-lithistid sponges from the early Silurian of the Southern Urals, Russia","authors":"J. Botting, R. Yakupov","doi":"10.1080/11035897.2019.1621375","DOIUrl":"https://doi.org/10.1080/11035897.2019.1621375","url":null,"abstract":"ABSTRACT Despite the recent discovery of abundant and diverse latest Ordovician sponges in China, early Silurian sponges are generally scarce, and non-lithistid, spiculate sponges remain poorly known. This is particularly true outside of a few well-studied regions, and monographic biases strongly influence the published record of the group. A new, well-preserved example of the spinose reticulosan Acutipuerilis from the Silurian of the southern Ural Mountains represents the first such fossil from this region and the first post-Ordovician asthenospongiid. Hexaradiate heteractinid spicules assigned to Toquimiella? sp. co-occur in the same rocks with fragments of other reticulosans including the reticulosan Plectoderma? sp., but no other fully articulated remains have been found. These three genera were previously known only from their type localities in Laurentia and Avalonia, in different environments, and the remarkable co-occurrence here raises the possibility of a change in sponge ecology and distribution following the Hirnantian Extinction.","PeriodicalId":55094,"journal":{"name":"Gff","volume":"141 1","pages":"191 - 199"},"PeriodicalIF":1.0,"publicationDate":"2019-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/11035897.2019.1621375","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46900292","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}
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