Pub Date : 2020-10-01DOI: 10.1080/11035897.2020.1819407
Stephan C. Oborny, B. Cramer, C. Brett
ABSTRACT Silurian strata within the tristate area of Indiana, Ohio, and Kentucky have been thoroughly studied for well over a century. Due to rapid facies changes throughout the region numerous lithostratigraphic terminologies were established, many of which were difficult to correlate even over short distances. Recently these stratigraphic complexities have received renewed interest due to advancements in bio-, chemo-, and sequence stratigraphy that greatly improved our understanding of the tristate area. These improvements had significant implications for our ability to correlate Rhuddanian through lower Sheinwoodian strata between the Appalachian and Illinois basins and allowed unified nomenclatural and sequence stratigraphic hierarchies for this interval to be developed across the Cincinnati Arch. Recent advancements in regional chronostratigraphy of Silurian strata, however, highlight several discrepancies with regards to the 3rd- and 4th-order sequence stratigraphic hierarchies assigned within these basins. In an effort to alleviate these points of disagreement, we contribute new δ13Ccarb chemostratigraphic and sequence stratigraphic analyses of a basinward Appalachian section from Scioto County, Ohio, spanning upper Telychian through Gorstian strata assigned to the Estill through Tymochtee formations, complemented by gamma-ray core scans for localities traversing northwestward from the sampled core section into western Ohio. These new data allow unified nomenclatural and sequence stratigraphic hierarchies to be developed throughout the region for strata spanning the upper Telychian through Gorstian stages. Additionally, these findings highlight a significant shift in the primary sites of sediment accommodation during the studied depositional interval.
{"title":"High-resolution event stratigraphy (HiRES) of the Silurian across the Cincinnati Arch (USA) through integrating conodont and carbon isotope biochemostratigraphy, with gamma-ray and sequence stratigraphy","authors":"Stephan C. Oborny, B. Cramer, C. Brett","doi":"10.1080/11035897.2020.1819407","DOIUrl":"https://doi.org/10.1080/11035897.2020.1819407","url":null,"abstract":"ABSTRACT Silurian strata within the tristate area of Indiana, Ohio, and Kentucky have been thoroughly studied for well over a century. Due to rapid facies changes throughout the region numerous lithostratigraphic terminologies were established, many of which were difficult to correlate even over short distances. Recently these stratigraphic complexities have received renewed interest due to advancements in bio-, chemo-, and sequence stratigraphy that greatly improved our understanding of the tristate area. These improvements had significant implications for our ability to correlate Rhuddanian through lower Sheinwoodian strata between the Appalachian and Illinois basins and allowed unified nomenclatural and sequence stratigraphic hierarchies for this interval to be developed across the Cincinnati Arch. Recent advancements in regional chronostratigraphy of Silurian strata, however, highlight several discrepancies with regards to the 3rd- and 4th-order sequence stratigraphic hierarchies assigned within these basins. In an effort to alleviate these points of disagreement, we contribute new δ13Ccarb chemostratigraphic and sequence stratigraphic analyses of a basinward Appalachian section from Scioto County, Ohio, spanning upper Telychian through Gorstian strata assigned to the Estill through Tymochtee formations, complemented by gamma-ray core scans for localities traversing northwestward from the sampled core section into western Ohio. These new data allow unified nomenclatural and sequence stratigraphic hierarchies to be developed throughout the region for strata spanning the upper Telychian through Gorstian stages. Additionally, these findings highlight a significant shift in the primary sites of sediment accommodation during the studied depositional interval.","PeriodicalId":55094,"journal":{"name":"Gff","volume":"142 1","pages":"309 - 324"},"PeriodicalIF":1.0,"publicationDate":"2020-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/11035897.2020.1819407","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49394519","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 : 2020-10-01DOI: 10.1080/11035897.2020.1822438
A. Petersson, L. Tual
ABSTRACT Several orogenies have shaped the bedrock of southern Sweden. While mafic intrusions represent significant sources of information for reconstructing geodynamics and crustal evolution, the characterization of the various generations of such intrusions in Sweden remains limited. We report in situ zircon U–Pb ages and Hf isotope data from a Fe-Ti eclogite and a coronitic metagabbro from the Eastern Segment in southern Sweden. Crystallisation ages at 1683 ± 17 Ma of the eclogite suggest affiliation with the surrounding 1730–1660 Ma Transscandinavian Igneous Belt intrusions that dominate the Eastern Segment. Secondary zircon growth and Pb-loss in the eclogite sample at 1459 ± 44 Ma and the crystallisation of the metagabbro at 1431 ± 26 Ma overlap and are related to magmatic activity during the Hallandian orogeny. Zircon Hf isotope signatures with chondritic and sub-chondritic values at ~1683 Ma and ~1431 Ma, respectively, correspond to an enriched (or mildly depleted) source in line with a “Mixed Svecofennian Crustal Reservoir”. These isotope signatures are more enriched than those in the surrounding gneisses. Zircon isotope data from the herein analysed zircon grains indicate that the eclogite and metagabbro had an enriched mafic source in the mid to lower crust, or within the subcontinental lithospheric mantle below Fennoscandia.
{"title":"Zircon U–Pb-Hf isotope data in eclogite and metagabbro from southern Sweden reveal a common long-lived evolution and enriched source","authors":"A. Petersson, L. Tual","doi":"10.1080/11035897.2020.1822438","DOIUrl":"https://doi.org/10.1080/11035897.2020.1822438","url":null,"abstract":"ABSTRACT Several orogenies have shaped the bedrock of southern Sweden. While mafic intrusions represent significant sources of information for reconstructing geodynamics and crustal evolution, the characterization of the various generations of such intrusions in Sweden remains limited. We report in situ zircon U–Pb ages and Hf isotope data from a Fe-Ti eclogite and a coronitic metagabbro from the Eastern Segment in southern Sweden. Crystallisation ages at 1683 ± 17 Ma of the eclogite suggest affiliation with the surrounding 1730–1660 Ma Transscandinavian Igneous Belt intrusions that dominate the Eastern Segment. Secondary zircon growth and Pb-loss in the eclogite sample at 1459 ± 44 Ma and the crystallisation of the metagabbro at 1431 ± 26 Ma overlap and are related to magmatic activity during the Hallandian orogeny. Zircon Hf isotope signatures with chondritic and sub-chondritic values at ~1683 Ma and ~1431 Ma, respectively, correspond to an enriched (or mildly depleted) source in line with a “Mixed Svecofennian Crustal Reservoir”. These isotope signatures are more enriched than those in the surrounding gneisses. Zircon isotope data from the herein analysed zircon grains indicate that the eclogite and metagabbro had an enriched mafic source in the mid to lower crust, or within the subcontinental lithospheric mantle below Fennoscandia.","PeriodicalId":55094,"journal":{"name":"Gff","volume":"142 1","pages":"253 - 266"},"PeriodicalIF":1.0,"publicationDate":"2020-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/11035897.2020.1822438","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48857047","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 : 2020-10-01DOI: 10.1080/11035897.2020.1822437
A. Goodship, H. Alexanderson
ABSTRACT Värmland in south western Sweden lies across the established zone of marine-terrestrial transition of the Scandinavian Ice Sheet (SIS) margin. The region lies inside the Younger Dryas maximum limit reached at 12.7 cal ka BP and the area of rapid final SIS retreat from 11.5 cal ka BP. LiDAR data across Värmland allows more detailed observation and analysis of glacial landforms formed during this stage than previously possible. This study synthesises geomorphological mapping performed on highly detailed digital elevation models (DEMs) and field observations across the region around Torsby in northern Värmland to reconstruct the dynamics of the ice sheet as it retreated. Several landforms that developed during deglaciation are identified and clearly reflect the change from a marine to terrestrially terminating ice margin. Ice-marginal deltas suggest a slowing of retreat at the point of marine-terrestrial transition. Increased topographic control on ice-sheet flow, pattern of drainage and ice sheet decay is indicated by the distribution of streamlined terrain, eskers, and outwash material. Hummocky terrain across low ground and incised valleys suggest persistence of ice in topographic lows beyond the retreat of the main ice front. Combined analysis of identified landforms allows a model for the pattern of retreat to be produced that traces the retreating ice sheet margin in far greater detail than previously has been possible in this area. This provides important data for understanding the final retreat of the SIS and details processes likely occurring beneath the margin of the Greenland Ice Sheet today.
{"title":"Dynamics of a retreating ice sheet: a LiDAR study in Värmland, SW Sweden","authors":"A. Goodship, H. Alexanderson","doi":"10.1080/11035897.2020.1822437","DOIUrl":"https://doi.org/10.1080/11035897.2020.1822437","url":null,"abstract":"ABSTRACT Värmland in south western Sweden lies across the established zone of marine-terrestrial transition of the Scandinavian Ice Sheet (SIS) margin. The region lies inside the Younger Dryas maximum limit reached at 12.7 cal ka BP and the area of rapid final SIS retreat from 11.5 cal ka BP. LiDAR data across Värmland allows more detailed observation and analysis of glacial landforms formed during this stage than previously possible. This study synthesises geomorphological mapping performed on highly detailed digital elevation models (DEMs) and field observations across the region around Torsby in northern Värmland to reconstruct the dynamics of the ice sheet as it retreated. Several landforms that developed during deglaciation are identified and clearly reflect the change from a marine to terrestrially terminating ice margin. Ice-marginal deltas suggest a slowing of retreat at the point of marine-terrestrial transition. Increased topographic control on ice-sheet flow, pattern of drainage and ice sheet decay is indicated by the distribution of streamlined terrain, eskers, and outwash material. Hummocky terrain across low ground and incised valleys suggest persistence of ice in topographic lows beyond the retreat of the main ice front. Combined analysis of identified landforms allows a model for the pattern of retreat to be produced that traces the retreating ice sheet margin in far greater detail than previously has been possible in this area. This provides important data for understanding the final retreat of the SIS and details processes likely occurring beneath the margin of the Greenland Ice Sheet today.","PeriodicalId":55094,"journal":{"name":"Gff","volume":"142 1","pages":"325 - 345"},"PeriodicalIF":1.0,"publicationDate":"2020-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/11035897.2020.1822437","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45529206","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 : 2020-09-24DOI: 10.1080/11035897.2020.1819406
Anette E. S. Högström, J. R. Ebbestad, Yutaro Suzuki
ABSTRACT A new rare Upper Ordovician mound dwelling palaeoloricate chiton is described as Crassaplax collicola gen. et sp. nov. from three large isolated intermediate valves from the Katian carbonate mud mounds of the Boda Limestone in the Siljan district of central Sweden. Together with the previously known Spicuchelodes? sp., also from the Boda Limestone, these are the only known Late Ordovician mound dwellers so far among the palaeoloricates, adding to Ordovician environments with reported chiton remains. Crassaplax collicola is distinguished from other Ordovician palaeoloricate chitons by their thick and large valves that can be 2 cm in length, and especially the clear differentiation between the lateral and central valve areas.
{"title":"A new large mound dwelling chiton (Mollusca), from the Late Ordovician Boda Limestone of central Sweden","authors":"Anette E. S. Högström, J. R. Ebbestad, Yutaro Suzuki","doi":"10.1080/11035897.2020.1819406","DOIUrl":"https://doi.org/10.1080/11035897.2020.1819406","url":null,"abstract":"ABSTRACT A new rare Upper Ordovician mound dwelling palaeoloricate chiton is described as Crassaplax collicola gen. et sp. nov. from three large isolated intermediate valves from the Katian carbonate mud mounds of the Boda Limestone in the Siljan district of central Sweden. Together with the previously known Spicuchelodes? sp., also from the Boda Limestone, these are the only known Late Ordovician mound dwellers so far among the palaeoloricates, adding to Ordovician environments with reported chiton remains. Crassaplax collicola is distinguished from other Ordovician palaeoloricate chitons by their thick and large valves that can be 2 cm in length, and especially the clear differentiation between the lateral and central valve areas.","PeriodicalId":55094,"journal":{"name":"Gff","volume":"142 1","pages":"297 - 303"},"PeriodicalIF":1.0,"publicationDate":"2020-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/11035897.2020.1819406","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47466250","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 : 2020-09-22DOI: 10.1080/11035897.2020.1819408
J. Pettersson, P. Ahlberg, Anders Lindskog, J. Lindgren, M. Eriksson
ABSTRACT In 2006, a new species of non-calcified dasycladalean alga, Chaetocladus gracilis, from the upper Silurian of Skåne (Scania), southernmost Sweden, was erected. The original description was based on a single incomplete fossil recovered from the abandoned limestone quarry at Bjärsjölagård, a classic geologic locality in Scania. Here we present four additional and, importantly, more complete specimens from this same site and type stratum. This new material largely corroborates the general anatomical features of C. gracilis, but also adds some intricate details, most notably with regards to the external sheet-like phytoleim and organisation of the laterals. Elemental mapping confirmed an expected carbonaceous composition of the fossils, which are embedded in a calcareous mudstone. These additional fossils show that the originally described specimen was not a singular occurrence at this locality. Based on the state of preservation of our algal fossils, we note that the mudstone facies of the Ludlow Bjärsjölagård Limestone Member of the Klinta Formation (Öved-Ramsåsa Group), from which all C. gracilis have been recovered, share characteristics with deposits typically referred to as “algal-Lagerstätten”.
{"title":"The fossil alga Chaetocladus gracilis revisited: new material from the Silurian of Sweden","authors":"J. Pettersson, P. Ahlberg, Anders Lindskog, J. Lindgren, M. Eriksson","doi":"10.1080/11035897.2020.1819408","DOIUrl":"https://doi.org/10.1080/11035897.2020.1819408","url":null,"abstract":"ABSTRACT In 2006, a new species of non-calcified dasycladalean alga, Chaetocladus gracilis, from the upper Silurian of Skåne (Scania), southernmost Sweden, was erected. The original description was based on a single incomplete fossil recovered from the abandoned limestone quarry at Bjärsjölagård, a classic geologic locality in Scania. Here we present four additional and, importantly, more complete specimens from this same site and type stratum. This new material largely corroborates the general anatomical features of C. gracilis, but also adds some intricate details, most notably with regards to the external sheet-like phytoleim and organisation of the laterals. Elemental mapping confirmed an expected carbonaceous composition of the fossils, which are embedded in a calcareous mudstone. These additional fossils show that the originally described specimen was not a singular occurrence at this locality. Based on the state of preservation of our algal fossils, we note that the mudstone facies of the Ludlow Bjärsjölagård Limestone Member of the Klinta Formation (Öved-Ramsåsa Group), from which all C. gracilis have been recovered, share characteristics with deposits typically referred to as “algal-Lagerstätten”.","PeriodicalId":55094,"journal":{"name":"Gff","volume":"142 1","pages":"304 - 308"},"PeriodicalIF":1.0,"publicationDate":"2020-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/11035897.2020.1819408","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41628162","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 : 2020-09-07DOI: 10.1080/11035897.2020.1809823
R. Lilljequist, A. Zang
One of Sweden’s most successful geologists, Professor Ove Stephansson, passed away on February, 19 2020. During his professional life he published more than 200 articles, conference papers and book...
{"title":"Ove Stephansson, 1938-2020","authors":"R. Lilljequist, A. Zang","doi":"10.1080/11035897.2020.1809823","DOIUrl":"https://doi.org/10.1080/11035897.2020.1809823","url":null,"abstract":"One of Sweden’s most successful geologists, Professor Ove Stephansson, passed away on February, 19 2020. During his professional life he published more than 200 articles, conference papers and book...","PeriodicalId":55094,"journal":{"name":"Gff","volume":"142 1","pages":"346 - 347"},"PeriodicalIF":1.0,"publicationDate":"2020-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/11035897.2020.1809823","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46250950","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 : 2020-07-03DOI: 10.1080/11035897.2020.1762723
M. Aubrechtová, T. Meidla
ABSTRACT Cephalopods of the order Lituitida Starobogatov, 1983 from the late Darriwilian and early Sandbian strata of Estonia are revised herein. During that time, the lituitids reached their peak abundance and were among the key components of cephalopod faunas on Baltica, as well as in other mid- and low-latitude palaeogeographic locations. The Estonian lituitids mostly come from localities representing more off-shore environments with deeper-water sedimentation in the Middle Ordovician. This supports previous assumptions that lituitids preferred pelagic environments and were capable of long-distance migration. In the studied lituitid collection, two genera were identified – Lituites Bertrand, 1763 and Ancistroceras Boll, 1857. Three species – Ancistroceras ristnensis sp. nov., Ancistroceras vahikuelaensis sp. nov. and Lituites nehatuensis sp. nov. – were newly established. However, species determinations were often hindered by high intraspecific variability and fragmentary preservation. Investigation of cameral deposits using median sections showed that: connecting rings in chambers with deposits are commonly broken or missing; oriented fragments of connecting rings are present, sometimes overgrown by primary deposits; several generations of primary deposits can be developed; simultaneous presence of both broken and intact connecting rings in the same specimen is usual. These observations elucidate the formation of cameral deposits in lituitids. Currently, this process is explained either by passive deposition from cameral fluids, or active secretion by cameral mantle. The evidence collected herein from Estonian lituitids reveals, however, that both modes of formation might have occurred successively during the lituitid ontogeny and that a gradual, life-time destruction of connecting rings was possibly involved.
{"title":"Lituitid cephalopods from the upper Darriwilian and basal Sandbian (Middle–Upper Ordovician) of Estonia","authors":"M. Aubrechtová, T. Meidla","doi":"10.1080/11035897.2020.1762723","DOIUrl":"https://doi.org/10.1080/11035897.2020.1762723","url":null,"abstract":"ABSTRACT Cephalopods of the order Lituitida Starobogatov, 1983 from the late Darriwilian and early Sandbian strata of Estonia are revised herein. During that time, the lituitids reached their peak abundance and were among the key components of cephalopod faunas on Baltica, as well as in other mid- and low-latitude palaeogeographic locations. The Estonian lituitids mostly come from localities representing more off-shore environments with deeper-water sedimentation in the Middle Ordovician. This supports previous assumptions that lituitids preferred pelagic environments and were capable of long-distance migration. In the studied lituitid collection, two genera were identified – Lituites Bertrand, 1763 and Ancistroceras Boll, 1857. Three species – Ancistroceras ristnensis sp. nov., Ancistroceras vahikuelaensis sp. nov. and Lituites nehatuensis sp. nov. – were newly established. However, species determinations were often hindered by high intraspecific variability and fragmentary preservation. Investigation of cameral deposits using median sections showed that: connecting rings in chambers with deposits are commonly broken or missing; oriented fragments of connecting rings are present, sometimes overgrown by primary deposits; several generations of primary deposits can be developed; simultaneous presence of both broken and intact connecting rings in the same specimen is usual. These observations elucidate the formation of cameral deposits in lituitids. Currently, this process is explained either by passive deposition from cameral fluids, or active secretion by cameral mantle. The evidence collected herein from Estonian lituitids reveals, however, that both modes of formation might have occurred successively during the lituitid ontogeny and that a gradual, life-time destruction of connecting rings was possibly involved.","PeriodicalId":55094,"journal":{"name":"Gff","volume":"142 1","pages":"267 - 296"},"PeriodicalIF":1.0,"publicationDate":"2020-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/11035897.2020.1762723","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46905377","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 : 2020-07-02DOI: 10.1080/11035897.2020.1762722
L. Collantes, E. Mayoral, J. Chirivella, R. Gozalo
ABSTRACT The present work is an overview of the current knowledge about the genus Marocella on the Iberian Peninsula, describing new specimens from the lower and middle Cambrian (Cambrian Series 2 and Miaolingian) of the southwestern Ossa-Morena Zone and Iberian Chains. Specimens from the lower Cambrian of the Ossa-Morena Zone are described as M. morenensis. Also, we found specimens in the Iberian Chains, which have been described earlier from the Cantabrian Mountains and dealt with as Marocella cf. morenensis. These specimens were found in strata of the latest Stage 4 of Cambrian or earliest Wuliuan. The youngest specimens from the upper Leonian to middle Caesaraugustian regional Stage (Wuliuan to early Drumian) of Iberian Chains are newly discovered material and classified as M. aff. morenensis. On the basis of new material of M. morenensis, M. mira and M. morenensis are regarded as different species herein, and the biostratigraphic and palaeobiogeographic distribution of Marocella is reviewed.
{"title":"New data on Marocella (Mollusca, Helcionelloida) from the Cambrian (Series 2–Miaolingian) of the Iberian Peninsula","authors":"L. Collantes, E. Mayoral, J. Chirivella, R. Gozalo","doi":"10.1080/11035897.2020.1762722","DOIUrl":"https://doi.org/10.1080/11035897.2020.1762722","url":null,"abstract":"ABSTRACT The present work is an overview of the current knowledge about the genus Marocella on the Iberian Peninsula, describing new specimens from the lower and middle Cambrian (Cambrian Series 2 and Miaolingian) of the southwestern Ossa-Morena Zone and Iberian Chains. Specimens from the lower Cambrian of the Ossa-Morena Zone are described as M. morenensis. Also, we found specimens in the Iberian Chains, which have been described earlier from the Cantabrian Mountains and dealt with as Marocella cf. morenensis. These specimens were found in strata of the latest Stage 4 of Cambrian or earliest Wuliuan. The youngest specimens from the upper Leonian to middle Caesaraugustian regional Stage (Wuliuan to early Drumian) of Iberian Chains are newly discovered material and classified as M. aff. morenensis. On the basis of new material of M. morenensis, M. mira and M. morenensis are regarded as different species herein, and the biostratigraphic and palaeobiogeographic distribution of Marocella is reviewed.","PeriodicalId":55094,"journal":{"name":"Gff","volume":"142 1","pages":"190 - 205"},"PeriodicalIF":1.0,"publicationDate":"2020-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/11035897.2020.1762722","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44110380","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 : 2020-07-02DOI: 10.1080/11035897.2020.1781245
S. McLoughlin
ABSTRACT An assemblage of permineralized conifer and angiosperm woods collected from Paleogene marine strata on Seymour Island during the Swedish Antarctic expedition of 1901–1903 includes many specimens with internal damage caused by an array of xylophagous organisms. Short, broad, clavate borings referable to Gastrochaenolites clavatus are attributed to pholadid bivalves. Elongate borings with carbonate linings referable to Apectoichnus longissimus were produced by teredinid bivalves. Slender, cylindrical tunnels cross-cutting growth rings and backfilled in meniscoid fashion by frass composed of angular tracheid fragments were probably produced by a terrestrial beetle borer. They are most similar to tunnels generated by modern cerambycid and ptinid coleopterans. Less regular, spindle-shaped cavities and degraded zones flanking growth rings are similar to fungi-generated modern white pocket rot. Larger chambers in the heartwood referable to the ichnotaxon Asthenopodichnium lignorum were produced by an alternative mode of fungal degradation. The biological interactions evident in the fossil woods illustrate additional terrestrial trophic levels enhancing the known complexity of ecosystems on and around the Antarctic Peninsula shortly before the initial pulse of mid-Cenozoic glaciation in Antarctica that caused extirpation of the majority of plants and animals in that region.
{"title":"Marine and terrestrial invertebrate borings and fungal damage in Paleogene fossil woods from Seymour Island, Antarctica","authors":"S. McLoughlin","doi":"10.1080/11035897.2020.1781245","DOIUrl":"https://doi.org/10.1080/11035897.2020.1781245","url":null,"abstract":"ABSTRACT An assemblage of permineralized conifer and angiosperm woods collected from Paleogene marine strata on Seymour Island during the Swedish Antarctic expedition of 1901–1903 includes many specimens with internal damage caused by an array of xylophagous organisms. Short, broad, clavate borings referable to Gastrochaenolites clavatus are attributed to pholadid bivalves. Elongate borings with carbonate linings referable to Apectoichnus longissimus were produced by teredinid bivalves. Slender, cylindrical tunnels cross-cutting growth rings and backfilled in meniscoid fashion by frass composed of angular tracheid fragments were probably produced by a terrestrial beetle borer. They are most similar to tunnels generated by modern cerambycid and ptinid coleopterans. Less regular, spindle-shaped cavities and degraded zones flanking growth rings are similar to fungi-generated modern white pocket rot. Larger chambers in the heartwood referable to the ichnotaxon Asthenopodichnium lignorum were produced by an alternative mode of fungal degradation. The biological interactions evident in the fossil woods illustrate additional terrestrial trophic levels enhancing the known complexity of ecosystems on and around the Antarctic Peninsula shortly before the initial pulse of mid-Cenozoic glaciation in Antarctica that caused extirpation of the majority of plants and animals in that region.","PeriodicalId":55094,"journal":{"name":"Gff","volume":"142 1","pages":"223 - 236"},"PeriodicalIF":1.0,"publicationDate":"2020-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/11035897.2020.1781245","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44287041","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 : 2020-07-02DOI: 10.1080/11035897.2020.1781246
A. Hall, Mikis van Boeckel
ABSTRACT The present marine Baltic Sea basin (BSB) occupies an eroded Proterozoic intra-cratonic basin on the Fennoscandian shield. Competing models propose a Neogene fluvial origin, with later modification by glacial erosion, or a much younger development, with overdeepening beneath the Fennoscandian Ice Sheet (FIS). We test these alternatives using a first order source to sink sediment budget for the catchment of the BSB. Best estimates derived from geomorphic and cosmogenic nuclide evidence suggest depths of erosion over the last 1 Ma of 20 m in basement and 40 m in sedimentary rocks that surround the BSB. As the BSB has been overdeepened below a regional base level provided by the shallow Darss Sill at the boundary with the Kattegat, erosion of the BSB may be interpreted as glacial in origin, without a fluvial component. The estimated total volume of source area erosion is 30,628 km3 of which 87% is derived from the present BSB. Sediment volumes in the sink area within the limits of maximum Pleistocene glaciation are estimated at a minimum of 37,629 km3, after correction for local erosion, porosity, and carbonate losses. Marine Isotope Stage 12 and younger sediments account for 87% of the total Pleistocene sediment volume in the sink in Poland. Although significant uncertainties remain, the sediment budget is consistent with erosion of the BSB entirely by the FIS, mainly when the ice sheet reached its maximum extent and thickness during the Middle and Late Pleistocene glaciations.
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