cometadata/datacite-titles-descriptions-related-identifiers huggingface dataset:
DOI: 10.6084/m9.figshare.3454238
title: Phanerozoic history of deep-sea trace fossils

description: The Phanerozoic diversity of deep-sea trace fossils, based on 151 flysch formations, displays distinct, non-linear changes through the Phanerozoic, with peaks in the Ordovician-Early Silurian and Early Carboniferous, lowered in the Permian-older Late Jurassic, a peak in the Tithonian-Aptian, lowered in the Albian, and the maximum in the Eocene. The contribution of graphoglyptids in trace fossil assemblages rises gradually up to the end of the Cretaceous, shows a peak in the Palaeocene-Eocene but a depression in the Oligocene. All the changes were probably influenced by competition for food and food supply, bottom water temperatures and oxygenation, and frequency of flysch habitats. There is no clear influence of major biotic crises (Ordovician/Silurian, Cretaceous/Tertiary, Palaeocene/Eocene) on the diversity of deep trace fossils, except the Eocene/Oligocene crisis.
DOI: 10.6084/m9.figshare.3454238.v1
title: Phanerozoic history of deep-sea trace fossils

description: The Phanerozoic diversity of deep-sea trace fossils, based on 151 flysch formations, displays distinct, non-linear changes through the Phanerozoic, with peaks in the Ordovician-Early Silurian and Early Carboniferous, lowered in the Permian-older Late Jurassic, a peak in the Tithonian-Aptian, lowered in the Albian, and the maximum in the Eocene. The contribution of graphoglyptids in trace fossil assemblages rises gradually up to the end of the Cretaceous, shows a peak in the Palaeocene-Eocene but a depression in the Oligocene. All the changes were probably influenced by competition for food and food supply, bottom water temperatures and oxygenation, and frequency of flysch habitats. There is no clear influence of major biotic crises (Ordovician/Silurian, Cretaceous/Tertiary, Palaeocene/Eocene) on the diversity of deep trace fossils, except the Eocene/Oligocene crisis.
DOI: 10.6084/m9.figshare.3454235
title: U–Pb zircon (SHRIMP) ages for the Lebombo rhyolites, South Africa: refining the duration of Karoo volcanism

description: U–Pb SHRIMP ages are reported for three rhyolite flows from the Lebombo rift region of the Karoo volcanic province. Two flows are interbedded with the Sabie River Basalt Formation and a third sample is from the overlying rhyolitic Jozini Formation. The interbedded rhyolites yield ages of 182.0 ± 2.1 and 179.9 ± 1.8 Ma, whilst the overlying Jozini Formation rhyolite yields an age of 182.1 ± 2.9 Ma. Combined with existing <sup>40</sup>Ar/<sup>39</sup>Ar geochronology, the new SHRIMP data fine-tunes the chronology of the Karoo volcanic province and indicates the 12 km succession of volcanic rocks in the Lebombo rift were erupted in 1–2 million years and lends considerable support to the links between the Pleinsbachian–Toarcian extinction event and the global environmental impact of Karoo volcanism.
DOI: 10.6084/m9.figshare.3454235.v1
title: U–Pb zircon (SHRIMP) ages for the Lebombo rhyolites, South Africa: refining the duration of Karoo volcanism

description: U–Pb SHRIMP ages are reported for three rhyolite flows from the Lebombo rift region of the Karoo volcanic province. Two flows are interbedded with the Sabie River Basalt Formation and a third sample is from the overlying rhyolitic Jozini Formation. The interbedded rhyolites yield ages of 182.0 ± 2.1 and 179.9 ± 1.8 Ma, whilst the overlying Jozini Formation rhyolite yields an age of 182.1 ± 2.9 Ma. Combined with existing <sup>40</sup>Ar/<sup>39</sup>Ar geochronology, the new SHRIMP data fine-tunes the chronology of the Karoo volcanic province and indicates the 12 km succession of volcanic rocks in the Lebombo rift were erupted in 1–2 million years and lends considerable support to the links between the Pleinsbachian–Toarcian extinction event and the global environmental impact of Karoo volcanism.
DOI: 10.6084/m9.figshare.3454232
title: The White Stone Band of the Kimmeridge Clay Formation, an integrated high-resolution approach to understanding environmental change

description: The Kimmeridge Clay is a Jurassic mudrock succession that shows Milankovitch Band climatic cyclicity. A key issue is to determine how the subtle changes that define this cyclicity result from climatic change. Using material from the Natural Environment Research Council Rapid Global Geological Events (RGGE) Kimmeridge Drilling Project boreholes, the White Stone Band was investigated at the lamination scale using backscattered electron imagery and quantitative palynofacies. Fabric analysis shows the lamination to represent successive deposition of coccolith-rich and organic-matter-rich layers. Individual laminae contain unsorted palynological debris with a consistent ratio of marine and terrestrial components. Such mixed organic matter input is interpreted as the result of storm transport. Linking water column processes to laminae deposition suggests seasonal input with a coccolith bloom followed by a more diverse assemblage including dinoflagellates and photosynthetic chlorobiacean bacteria. As the photic zone extended into the euxinic water column organic matter export to the sea bed underwent minimal cycling through oxidation and subsequently became preserved through sulphurization with greatly increased sequestration of carbon. This was significantly increased by late season storm-driven mixing of euxinic water into the photic zone. Increased frequency of storm systems would therefore dilute the coccolith input to give an oil shale. Hence climatically induced changes in storm frequency would progressively vary the organic content of the sediment and generate the climate cycle signal.
DOI: 10.6084/m9.figshare.3454232.v1
title: The White Stone Band of the Kimmeridge Clay Formation, an integrated high-resolution approach to understanding environmental change

description: The Kimmeridge Clay is a Jurassic mudrock succession that shows Milankovitch Band climatic cyclicity. A key issue is to determine how the subtle changes that define this cyclicity result from climatic change. Using material from the Natural Environment Research Council Rapid Global Geological Events (RGGE) Kimmeridge Drilling Project boreholes, the White Stone Band was investigated at the lamination scale using backscattered electron imagery and quantitative palynofacies. Fabric analysis shows the lamination to represent successive deposition of coccolith-rich and organic-matter-rich layers. Individual laminae contain unsorted palynological debris with a consistent ratio of marine and terrestrial components. Such mixed organic matter input is interpreted as the result of storm transport. Linking water column processes to laminae deposition suggests seasonal input with a coccolith bloom followed by a more diverse assemblage including dinoflagellates and photosynthetic chlorobiacean bacteria. As the photic zone extended into the euxinic water column organic matter export to the sea bed underwent minimal cycling through oxidation and subsequently became preserved through sulphurization with greatly increased sequestration of carbon. This was significantly increased by late season storm-driven mixing of euxinic water into the photic zone. Increased frequency of storm systems would therefore dilute the coccolith input to give an oil shale. Hence climatically induced changes in storm frequency would progressively vary the organic content of the sediment and generate the climate cycle signal.
DOI: 10.6084/m9.figshare.3454229
title: Laurentian provenance and an intracratonic tectonic setting for the Moine Supergroup, Scotland, constrained by detrital zircons from the Loch Eil and Glen Urquhart successions

description: Detrital zircons in psammite from the type section of the Loch Eil Group of the Moine Supergroup, NW Scotland, and from an unnamed quartzose psammite, interstratified with marble, at Glen Urquhart yield similar U–Pb detrital zircon ages ranging from <em>c</em>. 2300 to 900 Ma. Both samples show age peaks at <em>c</em>. 1680–1630 Ma, 1510–1490 Ma, 1430–1330 Ma and 1110–1040 Ma. Archaean age grains are absent and Palaeoproterozoic grains older than 1800 Ma are rare. Sediment accumulation occurred in the early Neoproterozoic post <em>c</em>. 900 Ma but prior to emplacement of the 870 Ma West Highland granite gneiss. The Glen Urquhart sample has previously been considered to form part of the Albynian sequence lying between the Moine and Dalradian supergroups. The similar detrital zircon age signature of the two samples is consistent with the Glen Urquhart material representing part of the upper Moine succession. In both samples, detrital age peaks at around 1650 Ma and 1500 Ma correspond closely to the Labradorian and Pinware magmatic events in NE Laurentia and Baltica whereas the younger age peaks at <em>c</em>. 1400 and 1100 Ma correspond to phases of the Grenville orogen in Laurentia. The presence of detritus at <em>c</em>. 1650 Ma argues against input from Amazonia, which lacks any recorded magmatic activity in the range 1700–1600 Ma. The absence of Archaean and late Palaeoproterozoic detritus, which is present in Laurentia-derived units younger than the Moine, such as the Dalradian and Western Newfoundland strata, suggests that the Labradorian and Pinware magmatic arcs retained sufficient topographic relief to mask and block any input of older detritus into the Neoproterozoic Moine basin. The Laurentian provenance of the zircons argues against an exotic origin for the Moine Supergroup. Palaeogeographical reconstructions suggest that the Moine succession accumulated in an intracratonic setting within Rodinia near the nexus of Laurentia, Baltica and Amazonia. Closure during the mid-Neoproterozoic of this site of lithospheric extension along with its record of Knoydartian deformation and metamorphism may be analogous to the intracratonic tectonic history of central Australia during the Neoproterozoic and Palaeozoic that developed in response to far-field effects on the active Gondwana margin.
DOI: 10.6084/m9.figshare.3454229.v1
title: Laurentian provenance and an intracratonic tectonic setting for the Moine Supergroup, Scotland, constrained by detrital zircons from the Loch Eil and Glen Urquhart successions

description: Detrital zircons in psammite from the type section of the Loch Eil Group of the Moine Supergroup, NW Scotland, and from an unnamed quartzose psammite, interstratified with marble, at Glen Urquhart yield similar U–Pb detrital zircon ages ranging from <em>c</em>. 2300 to 900 Ma. Both samples show age peaks at <em>c</em>. 1680–1630 Ma, 1510–1490 Ma, 1430–1330 Ma and 1110–1040 Ma. Archaean age grains are absent and Palaeoproterozoic grains older than 1800 Ma are rare. Sediment accumulation occurred in the early Neoproterozoic post <em>c</em>. 900 Ma but prior to emplacement of the 870 Ma West Highland granite gneiss. The Glen Urquhart sample has previously been considered to form part of the Albynian sequence lying between the Moine and Dalradian supergroups. The similar detrital zircon age signature of the two samples is consistent with the Glen Urquhart material representing part of the upper Moine succession. In both samples, detrital age peaks at around 1650 Ma and 1500 Ma correspond closely to the Labradorian and Pinware magmatic events in NE Laurentia and Baltica whereas the younger age peaks at <em>c</em>. 1400 and 1100 Ma correspond to phases of the Grenville orogen in Laurentia. The presence of detritus at <em>c</em>. 1650 Ma argues against input from Amazonia, which lacks any recorded magmatic activity in the range 1700–1600 Ma. The absence of Archaean and late Palaeoproterozoic detritus, which is present in Laurentia-derived units younger than the Moine, such as the Dalradian and Western Newfoundland strata, suggests that the Labradorian and Pinware magmatic arcs retained sufficient topographic relief to mask and block any input of older detritus into the Neoproterozoic Moine basin. The Laurentian provenance of the zircons argues against an exotic origin for the Moine Supergroup. Palaeogeographical reconstructions suggest that the Moine succession accumulated in an intracratonic setting within Rodinia near the nexus of Laurentia, Baltica and Amazonia. Closure during the mid-Neoproterozoic of this site of lithospheric extension along with its record of Knoydartian deformation and metamorphism may be analogous to the intracratonic tectonic history of central Australia during the Neoproterozoic and Palaeozoic that developed in response to far-field effects on the active Gondwana margin.
DOI: 10.6084/m9.figshare.3454226
title: Underplating-related finite-strain patterns in the Gran Paradiso massif, Western Alps, Italy: heterogeneous ductile strain superimposed on a nappe stack

description: A finite-strain study in the central and northern Gran Paradiso massif of the Italian Western Alps has been carried out to elucidate whether ductile strain shows a relationship to nappe contacts and to shed light on the nature of the subhorizontal foliation typical of the gneiss nappes in the Alps. The <em>R</em><sub>f</sub>/φ and Fry methods were used on feldspar porphyroclasts from 98 samples of the Gran Paradiso unit (upper tectonic unit of the Gran Paradiso massif) and 12 samples from the underlying Erfaulet unit (lower unit of the Gran Paradiso massif). Microstructures and thermobarometric data show that feldspar ductility at temperatures higher than <em>c</em>. 450 °C occurred only during high-pressure metamorphism, when the rocks were underplated beneath the overriding Adriatic plate. Therefore, the finite-strain data can be related to high-pressure metamorphism in the Alpine subduction zone. The augen gneiss was heterogeneously deformed and axial ratios of the strain ellipse in <em>xz</em> sections range from 2.1 to 69.8. The long axes of the finite-strain ellipsoids trend west–WNW and the short axes are subvertical, associated with a subhorizontal foliation. The strain magnitudes do not increase towards the nappe contacts. The data indicate flattening strain type in the Gran Paradiso unit and constrictional strain type in the Erfaulet unit and prove deviations from simple shear. We conclude that nappe stacking occurred early during subduction probably by brittle imbrication and that ductile strain was superimposed on and modified the nappe structure during high-pressure underplating in the Alpine subduction zone. The accumulation of ductile strain during underplating was not by simple shear and involved a component of vertical shortening, which caused the subhorizontal foliation in the Gran Paradiso massif.
DOI: 10.6084/m9.figshare.3454226.v1
title: Underplating-related finite-strain patterns in the Gran Paradiso massif, Western Alps, Italy: heterogeneous ductile strain superimposed on a nappe stack

description: A finite-strain study in the central and northern Gran Paradiso massif of the Italian Western Alps has been carried out to elucidate whether ductile strain shows a relationship to nappe contacts and to shed light on the nature of the subhorizontal foliation typical of the gneiss nappes in the Alps. The <em>R</em><sub>f</sub>/φ and Fry methods were used on feldspar porphyroclasts from 98 samples of the Gran Paradiso unit (upper tectonic unit of the Gran Paradiso massif) and 12 samples from the underlying Erfaulet unit (lower unit of the Gran Paradiso massif). Microstructures and thermobarometric data show that feldspar ductility at temperatures higher than <em>c</em>. 450 °C occurred only during high-pressure metamorphism, when the rocks were underplated beneath the overriding Adriatic plate. Therefore, the finite-strain data can be related to high-pressure metamorphism in the Alpine subduction zone. The augen gneiss was heterogeneously deformed and axial ratios of the strain ellipse in <em>xz</em> sections range from 2.1 to 69.8. The long axes of the finite-strain ellipsoids trend west–WNW and the short axes are subvertical, associated with a subhorizontal foliation. The strain magnitudes do not increase towards the nappe contacts. The data indicate flattening strain type in the Gran Paradiso unit and constrictional strain type in the Erfaulet unit and prove deviations from simple shear. We conclude that nappe stacking occurred early during subduction probably by brittle imbrication and that ductile strain was superimposed on and modified the nappe structure during high-pressure underplating in the Alpine subduction zone. The accumulation of ductile strain during underplating was not by simple shear and involved a component of vertical shortening, which caused the subhorizontal foliation in the Gran Paradiso massif.
DOI: 10.6084/m9.figshare.3454223
title: Cyclostratigraphy, orbital tuning and inferred productivity for the type Kimmeridge Clay (Late Jurassic), Southern England

description: Three independently measured variables (magnetic susceptibility, photoelectric factor and total gamma-ray) obtained from throughout the type Kimmeridge Clay Fm in Dorset (Southern England) were used to identify regular metre-scale, sedimentary cycles. Spectral analysis demonstrates that for long stratigraphical intervals the cycles are expressed as large-amplitude cycles of 1.87–4.05 m wavelength and smaller-amplitude cycles of around half that wavelength. These cycles are interpreted to record orbital obliquity and precession, respectively. The much larger amplitude of the inferred obliquity cycles compared with the precession cycles may indicate a high-latitude climatic forcing transferred to lower latitudes via sea-level variations. Orbital tuning indicates that the Early Kimmeridgian (<em>sensu anglico</em>) lasted at least 3.6 Ma (95 longer-wavelength cycles) and the Late Kimmeridgian at least 3.9 Ma (103 longer-wavelength cycles). The first detailed productivity estimates for the Kimmeridge Clay Fm, on a cycle-by-cycle calculation, indicate that average productivity of the type Kimmeridge Clay (220 g m<sup>−2</sup> a<sup>−1</sup>) was less than the average productivity on modern continental shelves. The high average organic carbon content of the type Kimmeridge Clay (3.8% total organic carbon) cannot be attributed to high average productivity. However, the average organic carbon content is consistent with low siliciclastic mineral dilution of organic matter and/or elevated preservation linked to reduced bottom-water oxygenation.
DOI: 10.6084/m9.figshare.3454223.v1
title: Cyclostratigraphy, orbital tuning and inferred productivity for the type Kimmeridge Clay (Late Jurassic), Southern England

description: Three independently measured variables (magnetic susceptibility, photoelectric factor and total gamma-ray) obtained from throughout the type Kimmeridge Clay Fm in Dorset (Southern England) were used to identify regular metre-scale, sedimentary cycles. Spectral analysis demonstrates that for long stratigraphical intervals the cycles are expressed as large-amplitude cycles of 1.87–4.05 m wavelength and smaller-amplitude cycles of around half that wavelength. These cycles are interpreted to record orbital obliquity and precession, respectively. The much larger amplitude of the inferred obliquity cycles compared with the precession cycles may indicate a high-latitude climatic forcing transferred to lower latitudes via sea-level variations. Orbital tuning indicates that the Early Kimmeridgian (<em>sensu anglico</em>) lasted at least 3.6 Ma (95 longer-wavelength cycles) and the Late Kimmeridgian at least 3.9 Ma (103 longer-wavelength cycles). The first detailed productivity estimates for the Kimmeridge Clay Fm, on a cycle-by-cycle calculation, indicate that average productivity of the type Kimmeridge Clay (220 g m<sup>−2</sup> a<sup>−1</sup>) was less than the average productivity on modern continental shelves. The high average organic carbon content of the type Kimmeridge Clay (3.8% total organic carbon) cannot be attributed to high average productivity. However, the average organic carbon content is consistent with low siliciclastic mineral dilution of organic matter and/or elevated preservation linked to reduced bottom-water oxygenation.
DOI: 10.6084/m9.figshare.3454220
title: Phytoplankton evidence for the timing and correlation of palaeoceanographical changes during the early Toarcian oceanic anoxic event (Early Jurassic)

description: The causes and duration of the early Toarcian anoxic event are controversial. Integration of data from calcareous and organic phytoplankton provides a biochronological framework that allows precise correlations across the western Tethys. In particular, the <em>Carinolithus superbus</em> nannofossil Zone can be used to correlate the levels enriched in organic matter and the related <em>δ</em><sup>13</sup>C negative excursion. Although a variable duration is given in the literature for this negative excursion, it is likely that it lasted between 520 and 650 ka. Increased atmospheric <em>p</em>CO<sub>2</sub>, related to excess volcanic emissions (magmatic activity in the Karoo and Ferrar Provinces), had an impact on climate and ocean chemistry, and marked the inception of a biotic crisis affecting many organisms. The beginning of the crisis within shallow carbonate platforms, documented at southern latitudes, predates the levels enriched in organic matter. Dinoflagellate cysts experienced a decrease in abundance in the <em>C. superbus</em> Zone, until they temporarily disappeared. The nannoplankton crisis was twofold: a decrease in size and low calcified specimens are observed in addition to a drastic decrease in absolute abundance. The increased atmospheric <em>p</em>CO<sub>2</sub>, as a result of the magmatic activity and temporarily amplified by transient methane release, could have been the trigger for the biocalcification crisis, which first affected the probably more reactive neritic system, and eventually the nannoplankton community.
DOI: 10.6084/m9.figshare.3454220.v1
title: Phytoplankton evidence for the timing and correlation of palaeoceanographical changes during the early Toarcian oceanic anoxic event (Early Jurassic)

description: The causes and duration of the early Toarcian anoxic event are controversial. Integration of data from calcareous and organic phytoplankton provides a biochronological framework that allows precise correlations across the western Tethys. In particular, the <em>Carinolithus superbus</em> nannofossil Zone can be used to correlate the levels enriched in organic matter and the related <em>δ</em><sup>13</sup>C negative excursion. Although a variable duration is given in the literature for this negative excursion, it is likely that it lasted between 520 and 650 ka. Increased atmospheric <em>p</em>CO<sub>2</sub>, related to excess volcanic emissions (magmatic activity in the Karoo and Ferrar Provinces), had an impact on climate and ocean chemistry, and marked the inception of a biotic crisis affecting many organisms. The beginning of the crisis within shallow carbonate platforms, documented at southern latitudes, predates the levels enriched in organic matter. Dinoflagellate cysts experienced a decrease in abundance in the <em>C. superbus</em> Zone, until they temporarily disappeared. The nannoplankton crisis was twofold: a decrease in size and low calcified specimens are observed in addition to a drastic decrease in absolute abundance. The increased atmospheric <em>p</em>CO<sub>2</sub>, as a result of the magmatic activity and temporarily amplified by transient methane release, could have been the trigger for the biocalcification crisis, which first affected the probably more reactive neritic system, and eventually the nannoplankton community.