cometadata/datacite-titles-descriptions-related-identifiers huggingface dataset:
DOI: 10.6084/m9.figshare.3453239
title: Direct measurement of recoil effects on <sup>40</sup>Ar/<sup>39</sup>Ar standards

description: Advances in the <sup>40</sup>Ar/<sup>39</sup>Ar method using new techniques have led to considerable efforts to improve the accuracy of the calibration of interlaboratory standards. However, the accuracy of the method ultimately relies on the measurement of <sup>40</sup>Ar*/<sup>39</sup>Ar<sub>K</sub> ratios on standards that have been calibrated with the K–Ar method. Usually a <sup>40</sup>Ar/<sup>39</sup>Ar total gas age is assumed to equate to a K–Ar age, but this assumes that there is zero loss of <sup>39</sup>Ar due to recoil. Traditional <sup>40</sup>Ar/<sup>39</sup>Ar total gas ages are Ar retention ages and are not strictly comparable to K–Ar ages. Efforts to estimate the importance of this effect on standards have relied on indirect evidence for <sup>39</sup>Ar recoil. We report direct measurements of <sup>39</sup>Ar recoil for primary and secondary standards using the vacuum-encapsulation technique and show that adjustments to some standard ages may be needed. Revised ages corrected for recoil are given for hornblendes MMhb-1 and Hb3gr, biotites GA1550 and FCT-3 and sanidines FCT-2 and TCR-2. The results show that, in most cases, recoil loss exceeds that which would be expected from grain size and geometry. Internal defects within mineral grains are likely the dominant control on the fraction of recoiled <sup>39</sup>Ar lost from these standards.
DOI: 10.6084/m9.figshare.3453239.v1
title: Direct measurement of recoil effects on <sup>40</sup>Ar/<sup>39</sup>Ar standards

description: Advances in the <sup>40</sup>Ar/<sup>39</sup>Ar method using new techniques have led to considerable efforts to improve the accuracy of the calibration of interlaboratory standards. However, the accuracy of the method ultimately relies on the measurement of <sup>40</sup>Ar*/<sup>39</sup>Ar<sub>K</sub> ratios on standards that have been calibrated with the K–Ar method. Usually a <sup>40</sup>Ar/<sup>39</sup>Ar total gas age is assumed to equate to a K–Ar age, but this assumes that there is zero loss of <sup>39</sup>Ar due to recoil. Traditional <sup>40</sup>Ar/<sup>39</sup>Ar total gas ages are Ar retention ages and are not strictly comparable to K–Ar ages. Efforts to estimate the importance of this effect on standards have relied on indirect evidence for <sup>39</sup>Ar recoil. We report direct measurements of <sup>39</sup>Ar recoil for primary and secondary standards using the vacuum-encapsulation technique and show that adjustments to some standard ages may be needed. Revised ages corrected for recoil are given for hornblendes MMhb-1 and Hb3gr, biotites GA1550 and FCT-3 and sanidines FCT-2 and TCR-2. The results show that, in most cases, recoil loss exceeds that which would be expected from grain size and geometry. Internal defects within mineral grains are likely the dominant control on the fraction of recoiled <sup>39</sup>Ar lost from these standards.
DOI: 10.6084/m9.figshare.3453233
title: The Cretaceous–Tertiary boundary (KTB) transition in NE Brazil

description: At 7800 km from Yucatan the Cretaceous–Tertiary boundary (KTB) transition of the Poty Quarry, NE Brazil, is the most distant locality with published accounts of Chicxulub impact–tsunami deposits, impact spherules and Ir anomaly. New investigations based on sedimentology, biostratigraphy, mineralogy and geochemistry fail to confirm these reports. Latest Maastrichtian planktic foraminiferal zones CF1 below an erosive and bioturbated disconformity and early Danian zone P1a(1) above indicate a short hiatus, with the KTB clay (zone P0), the Ir anomaly and the characteristic negative δ<sup>13</sup>C excursion missing. The disconformity coincides with the globally recognized latest Maastrichtian sea-level fall. Above the disconformity, an upward-fining micro-conglomerate with abundant reworked Cretaceous foraminifera, sub-angular phosphate clasts, calcitic and phosphatic spheroids along with an early Danian zone P1a(1) assemblage is interpreted as a gravity-flow deposit. Common spheroids throughout the late Campanian–Maastrichtian appear to be chamber infillings of the benthic foraminifer <em>Dentalina alternata</em>. Minor Ir anomalies in thin clay layers of zone Pla and no evidence of the Chicxulub impact reveal that the Poty Quarry section remains a very important example of the complex global environmental and sea-level changes observed in KT sequences from North America to Central America that are commonly misinterpreted as impact–tsunami events.
DOI: 10.6084/m9.figshare.3453233.v1
title: The Cretaceous–Tertiary boundary (KTB) transition in NE Brazil

description: At 7800 km from Yucatan the Cretaceous–Tertiary boundary (KTB) transition of the Poty Quarry, NE Brazil, is the most distant locality with published accounts of Chicxulub impact–tsunami deposits, impact spherules and Ir anomaly. New investigations based on sedimentology, biostratigraphy, mineralogy and geochemistry fail to confirm these reports. Latest Maastrichtian planktic foraminiferal zones CF1 below an erosive and bioturbated disconformity and early Danian zone P1a(1) above indicate a short hiatus, with the KTB clay (zone P0), the Ir anomaly and the characteristic negative δ<sup>13</sup>C excursion missing. The disconformity coincides with the globally recognized latest Maastrichtian sea-level fall. Above the disconformity, an upward-fining micro-conglomerate with abundant reworked Cretaceous foraminifera, sub-angular phosphate clasts, calcitic and phosphatic spheroids along with an early Danian zone P1a(1) assemblage is interpreted as a gravity-flow deposit. Common spheroids throughout the late Campanian–Maastrichtian appear to be chamber infillings of the benthic foraminifer <em>Dentalina alternata</em>. Minor Ir anomalies in thin clay layers of zone Pla and no evidence of the Chicxulub impact reveal that the Poty Quarry section remains a very important example of the complex global environmental and sea-level changes observed in KT sequences from North America to Central America that are commonly misinterpreted as impact–tsunami events.
DOI: 10.6084/m9.figshare.3453230
title: The anatomy of a Fenland roddon: sedimentation and environmental change in a lowland Holocene tidal creek environment

description: A Holocene sand/silt-filled tidal creek, locally called a roddon, excavated at Must Farm near Whittlesey, Cambridgeshire, within the English Fenland, preserves an unprecedented record of Fenland tidal creek evolution. The tidal creek was formed sometime between <em>c</em>. 4735 BP and <em>c</em>. 3645 BP. Its infill comprised centimetre-scale, laminated, tidal sand-mud couplets, numbering some 600 in total, with microfossils that show marine and coastal derivation of the sediment. The nature of the infill suggests rapid sedimentation that choked the creek system, perhaps in as little as a few years. At least three successive generations of roddons are present in the Fenland, suggesting at least three distinct episodes of tidal creek formation. The Must Farm roddon belongs to the first generation. A later, mud-filled channel was subsequently incised into the roddon, perhaps initiated by a marine surge. It quickly transformed into a slowly flowing river, as suggested by molluscs, ostracods and diatoms. Infill of this late-stage channel was slow, perhaps over about 1200 years between <em>c</em>. 3250 and 2050 BP (<em>c</em>. 1300–100 cal BC), as shown by archaeological finds. The mud-filled channel superficially resembles late-stage, organic-rich channel infills visible on aerial photographs, but is wider and deeper and might have been part of a more substantial long-lived ‘river’, perhaps a tributary of the proto-Nene.
DOI: 10.6084/m9.figshare.3453230.v1
title: The anatomy of a Fenland roddon: sedimentation and environmental change in a lowland Holocene tidal creek environment

description: A Holocene sand/silt-filled tidal creek, locally called a roddon, excavated at Must Farm near Whittlesey, Cambridgeshire, within the English Fenland, preserves an unprecedented record of Fenland tidal creek evolution. The tidal creek was formed sometime between <em>c</em>. 4735 BP and <em>c</em>. 3645 BP. Its infill comprised centimetre-scale, laminated, tidal sand-mud couplets, numbering some 600 in total, with microfossils that show marine and coastal derivation of the sediment. The nature of the infill suggests rapid sedimentation that choked the creek system, perhaps in as little as a few years. At least three successive generations of roddons are present in the Fenland, suggesting at least three distinct episodes of tidal creek formation. The Must Farm roddon belongs to the first generation. A later, mud-filled channel was subsequently incised into the roddon, perhaps initiated by a marine surge. It quickly transformed into a slowly flowing river, as suggested by molluscs, ostracods and diatoms. Infill of this late-stage channel was slow, perhaps over about 1200 years between <em>c</em>. 3250 and 2050 BP (<em>c</em>. 1300–100 cal BC), as shown by archaeological finds. The mud-filled channel superficially resembles late-stage, organic-rich channel infills visible on aerial photographs, but is wider and deeper and might have been part of a more substantial long-lived ‘river’, perhaps a tributary of the proto-Nene.
DOI: 10.6084/m9.figshare.3453224
title: Detrital zircon data reveal the origin of Australia’s largest delta system

description: The Late Cretaceous Ceduna Delta is the largest deltaic system on the Australian continent, yet its source is unknown. Apatite fission-track data reveal widespread Late Cretaceous exhumation across the southern Australian margin. New detrital zircon analysis of 786 grains from the Gnarlyknots-1 well, which penetrated the offshore delta top, show that the upper part of the delta (Santonian–Maastrichtian) was sourced largely from recycled Permian to Early Cretaceous cover and underlying basement eroded from the margin, proximal to the basin. This challenges the widely accepted model involving distal provenance of &gt;2000 km from the eastern margin of Australia.
DOI: 10.6084/m9.figshare.3453224.v1
title: Detrital zircon data reveal the origin of Australia’s largest delta system

description: The Late Cretaceous Ceduna Delta is the largest deltaic system on the Australian continent, yet its source is unknown. Apatite fission-track data reveal widespread Late Cretaceous exhumation across the southern Australian margin. New detrital zircon analysis of 786 grains from the Gnarlyknots-1 well, which penetrated the offshore delta top, show that the upper part of the delta (Santonian–Maastrichtian) was sourced largely from recycled Permian to Early Cretaceous cover and underlying basement eroded from the margin, proximal to the basin. This challenges the widely accepted model involving distal provenance of &gt;2000 km from the eastern margin of Australia.
DOI: 10.6084/m9.figshare.3453221
title: Volcanic hotspots of the central and southern Andes as seen from space by ASTER and MODVOLC between the years 2000 and 2010

description: We examine 150 volcanoes and geothermal areas in the central, southern and austral Andes for thermal anomalies between the years 2000 and 2010 from two different spaceborne sensors: (1) those automatically detected by the MODVOLC algorithm from MODIS; and (2) manually identified hotspots in night-time images from ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer). Based on previous work, we expected to find eight volcanoes displaying thermal anomalies (Ubinas, Villarrica, Copahue, Láscar, Llaima, Chaitén, Lonquimay and Chiliques). We document 35 volcanic areas with pixel-integrated temperatures of 4 up to more than 100 K above background in at least two images, and another 16 areas that have questionable hotspots with either smaller anomalies or a hotspot identified in only one image. Most of the thermal anomalies are related to known activity (i.e. lava and pyroclastic flows, growing lava domes, fumaroles, and lakes) while others are of unknown origin or reflect activity at volcanoes that were not thought to have surface activity. A handful of volcanoes exhibit temporal variations in the magnitude and location of their temperature anomalies that can be related to both documented and undocumented pulses of activity. Our survey reveals that low-amplitude volcanic hotspots detectable from space are more common than expected, based on lower spatial resolution data, and that these features could be more widely used to monitor changes in the activity of remote volcanoes. We find no evidence from ASTER or MODVOLC that the thermal anomalies were affected by six earthquakes with <em>M</em><sub>w</sub> above 7 in our study area from 2000 to 2010, although the observations may not have been optimal to detect such anomalies.
DOI: 10.6084/m9.figshare.3453215
title: Field relations, geochemistry and origin of the Upper Cretaceous volcaniclastic Kannaviou Formation in western Cyprus: evidence of a southerly Neotethyan volcanic arc

description: The Kannaviou Formation (up to 750 m thick) accumulated in a deep-sea setting in west Cyprus during Campanian–Early(?) Maastrichtian time. The formation depositionally overlies Upper Cretaceous ophiolitic lavas, including those associated with serpentinite-hosted arcuate lineaments. The Kannaviou Formation locally overlies ophiolitic serpentinite, indicating that mantle rocks were exposed on the seafloor prior to sediment deposition. Geochemical analyses of basalts that depositionally underlie the Kannaviou Formation, within the arcuate lineaments, indicate close similarities with the boninitic lavas of the South Troodos Transform Fault Zone in south Cyprus. Abundant volcanogenic and minor terrigenous and pelagic sedimentary rock material is present within the Kannaviou Formation, while kaolinite is common within interbedded red clays. Suitable terrigenous source lithologies are present in the deformed continental margin/deep-sea sedimentary rocks of the Mamonia Complex in west Cyprus. Whole-rock chemical analysis of sandstones of predominantly volcaniclastic origin indicates an intermediate arc-like composition. Electron microprobe analysis shows that glass is silicic, with a tholeiitic fractionation trend. Similar arc-like volcanic rocks of Late Cretaceous age are exposed in the western Kyrenia (Girne) Range, north Cyprus. The provenance of the Kannaviou Formation provides evidence of Late Cretaceous northwards subduction of the South Neotethys beneath a continental margin to the north.
DOI: 10.6084/m9.figshare.3453215.v1
title: Field relations, geochemistry and origin of the Upper Cretaceous volcaniclastic Kannaviou Formation in western Cyprus: evidence of a southerly Neotethyan volcanic arc

description: The Kannaviou Formation (up to 750 m thick) accumulated in a deep-sea setting in west Cyprus during Campanian–Early(?) Maastrichtian time. The formation depositionally overlies Upper Cretaceous ophiolitic lavas, including those associated with serpentinite-hosted arcuate lineaments. The Kannaviou Formation locally overlies ophiolitic serpentinite, indicating that mantle rocks were exposed on the seafloor prior to sediment deposition. Geochemical analyses of basalts that depositionally underlie the Kannaviou Formation, within the arcuate lineaments, indicate close similarities with the boninitic lavas of the South Troodos Transform Fault Zone in south Cyprus. Abundant volcanogenic and minor terrigenous and pelagic sedimentary rock material is present within the Kannaviou Formation, while kaolinite is common within interbedded red clays. Suitable terrigenous source lithologies are present in the deformed continental margin/deep-sea sedimentary rocks of the Mamonia Complex in west Cyprus. Whole-rock chemical analysis of sandstones of predominantly volcaniclastic origin indicates an intermediate arc-like composition. Electron microprobe analysis shows that glass is silicic, with a tholeiitic fractionation trend. Similar arc-like volcanic rocks of Late Cretaceous age are exposed in the western Kyrenia (Girne) Range, north Cyprus. The provenance of the Kannaviou Formation provides evidence of Late Cretaceous northwards subduction of the South Neotethys beneath a continental margin to the north.
DOI: 10.6084/m9.figshare.3453212
title: Paramagnetic metamorphic mineral assemblages controlling AMS in low-grade deformed metasediments and the implications with respect to the use of AMS as a strain marker

description: A regional analysis of the anisotropy of magnetic susceptibility (AMS) has been performed on low-grade metamorphic, deformed homogeneous siltstone beds (HSBs) of the Plougastel Formation in the Central Armorican Domain together with exhaustive compositional analyses of the studied specimens. Despite sampling a single horizon, different paramagnetic minerals are controlling the AMS in the Crozon peninsula sites (white mica and chlorite) and in the inland sites of the Central Armorican Domain (white mica, chloritoid and some chlorite). Both the Crozon peninsula and inland datasets show a hockey-stick shaped pattern on a plot of the shape parameter <em>T</em> versus the corrected degree of anisotropy <em>P</em><sub>J</sub>, although the whole pattern is shifted to higher <em>P</em><sub>J</sub> values for the inland dataset. High-field AMS indicates that the low-field <em>P</em><sub>J</sub> and <em>T</em> values from two inland sites are slightly enhanced by a small ferromagnetic (<em>sensu lato</em>) contribution. Furthermore, variation in <em>P</em><sub>J</sub> and <em>T</em> values within single sites can be attributed to an effect of the observed quartz/white mica ratio, as quartz grains disrupt the petrofabric intensity. Our findings clearly demonstrate that the AMS of the HSBs in the Central Armorican Domain is strongly influenced by compositional variations and does not merely indicate tectonic strain, even in very similar tectonostratigraphic settings.
DOI: 10.6084/m9.figshare.3453212.v1
title: Paramagnetic metamorphic mineral assemblages controlling AMS in low-grade deformed metasediments and the implications with respect to the use of AMS as a strain marker

description: A regional analysis of the anisotropy of magnetic susceptibility (AMS) has been performed on low-grade metamorphic, deformed homogeneous siltstone beds (HSBs) of the Plougastel Formation in the Central Armorican Domain together with exhaustive compositional analyses of the studied specimens. Despite sampling a single horizon, different paramagnetic minerals are controlling the AMS in the Crozon peninsula sites (white mica and chlorite) and in the inland sites of the Central Armorican Domain (white mica, chloritoid and some chlorite). Both the Crozon peninsula and inland datasets show a hockey-stick shaped pattern on a plot of the shape parameter <em>T</em> versus the corrected degree of anisotropy <em>P</em><sub>J</sub>, although the whole pattern is shifted to higher <em>P</em><sub>J</sub> values for the inland dataset. High-field AMS indicates that the low-field <em>P</em><sub>J</sub> and <em>T</em> values from two inland sites are slightly enhanced by a small ferromagnetic (<em>sensu lato</em>) contribution. Furthermore, variation in <em>P</em><sub>J</sub> and <em>T</em> values within single sites can be attributed to an effect of the observed quartz/white mica ratio, as quartz grains disrupt the petrofabric intensity. Our findings clearly demonstrate that the AMS of the HSBs in the Central Armorican Domain is strongly influenced by compositional variations and does not merely indicate tectonic strain, even in very similar tectonostratigraphic settings.
DOI: 10.6084/m9.figshare.3453209
title: New U–Pb SHRIMP ages from the Lubango region, SW Angola: insights into the Palaeoproterozoic evolution of the Angolan Shield, southern Congo Craton, Africa

description: In an attempt to better understand the tectonic evolution of the continental crust forming SW Angola, zircon grains from the principal Precambrian rock types exposed in the Lubango area have been analysed using the sensitive high-resolution ion microprobe method. U–Pb ages of 2038 ± 28 Ma and 1954 ± 6 Ma were obtained on weakly deformed granite samples from the basement below the Humpata Plateau. The Chela Group on the Humpata Plateau is a relatively undeformed Palaeoproterozoic supracrustal sequence with an eruptive age of 1798 ± 11 Ma on ignimbrite of the Humpata Formation. The age of the northern part of the Kunene Complex is constrained by zircon data from a xenolith of basement gneiss and a mangerite dyke cutting anorthosite, which give an emplacement age of 1385 ± 7 Ma. The <em>c</em>. 2.0 Ga granites below the Chela Group are part of a Palaeoproterozoic granitoid terrane that extends from north of Lubango in Angola into NW Namibia. This terrane is referred to as the Angolan Shield. Regionally, the Angolan Shield is interpreted to be part of a Palaeoproterozoic magmatic arc that extends NE from Angola and Namibia under Phanerozoic cover into NW Zambia. The resultant crustal terrane defined the southern margin of the developing Congo Craton at <em>c</em>. 2.0 ± 0.04 Ga.
DOI: 10.6084/m9.figshare.3453209.v1
title: New U–Pb SHRIMP ages from the Lubango region, SW Angola: insights into the Palaeoproterozoic evolution of the Angolan Shield, southern Congo Craton, Africa

description: In an attempt to better understand the tectonic evolution of the continental crust forming SW Angola, zircon grains from the principal Precambrian rock types exposed in the Lubango area have been analysed using the sensitive high-resolution ion microprobe method. U–Pb ages of 2038 ± 28 Ma and 1954 ± 6 Ma were obtained on weakly deformed granite samples from the basement below the Humpata Plateau. The Chela Group on the Humpata Plateau is a relatively undeformed Palaeoproterozoic supracrustal sequence with an eruptive age of 1798 ± 11 Ma on ignimbrite of the Humpata Formation. The age of the northern part of the Kunene Complex is constrained by zircon data from a xenolith of basement gneiss and a mangerite dyke cutting anorthosite, which give an emplacement age of 1385 ± 7 Ma. The <em>c</em>. 2.0 Ga granites below the Chela Group are part of a Palaeoproterozoic granitoid terrane that extends from north of Lubango in Angola into NW Namibia. This terrane is referred to as the Angolan Shield. Regionally, the Angolan Shield is interpreted to be part of a Palaeoproterozoic magmatic arc that extends NE from Angola and Namibia under Phanerozoic cover into NW Zambia. The resultant crustal terrane defined the southern margin of the developing Congo Craton at <em>c</em>. 2.0 ± 0.04 Ga.
DOI: 10.6084/m9.figshare.3453206
title: Function significance

description: function significance of the age vs. wealth crossed-categorization
DOI: 10.6084/m9.figshare.3453206.v1
title: function significance

description: function significance of the age vs. wealth crossed-categorization
DOI: 10.6084/m9.figshare.3453206.v2
title: Function significance

description: function significance of the age vs. wealth crossed-categorization
DOI: 10.6084/m9.figshare.3453206.v3
title: Function significance

description: function significance of the age vs. wealth crossed-categorization
DOI: 10.6084/m9.figshare.3453206.v4
title: Function significance

description: function significance of the age vs. wealth crossed-categorization
DOI: 10.6084/m9.figshare.3453206.v5
title: Function significance

description: function significance of the age vs. wealth crossed-categorization
DOI: 10.6084/m9.figshare.3453206.v6
title: Function significance

description: function significance of the age vs. wealth crossed-categorization