cometadata/datacite-titles-descriptions-related-identifiers huggingface dataset:
DOI: 10.6084/m9.figshare.3454268.v1
title: The extensional Messaria shear zone and associated brittle detachment faults, Aegean Sea, Greece

description: Structural, thermochronological and metamorphic data are used to elucidate the tectonic nature and evolution of the ductile extensional Messaria shear zone and the associated brittle Messaria and Fanari detachment faults, which exhumed their footwall from mid-crustal depths on the island of Ikaria in the Aegean. Thermobarometric data indicate that the Messaria shear zone formed at 350–&gt;400 °C and 3–4 kbar (i.e. at a depth of <em>c</em>. 15 km). Normal faulting was accompanied by the intrusion of two granites, which together with the thermobarometric data indicate a relatively high thermal field gradient of 25–35 °C km<sup>−1</sup>. Zircon and apatite fission-track and apatite (U–Th)/He ages demonstrate rapid cooling in the footwall of the Messaria detachment from <em>c</em>. 400 °C to <em>c</em>. 40 °C between 11 and 3 Ma. Age–distance relationships of the data suggest that the Messaria shear zone and the Messaria detachment slipped at apparent rates of <em>c</em>. 6–9 km Ma<sup>−1</sup>. Kinematic indicators show a consistent top-to-the-NNE shear sense for the extensional faults. However, at the southern part of the Messaria detachment some late-stage shear-sense indicators are top-to-the-SSW and are assumed to be associated with updoming of the footwall. Numerous deformed pegmatite veins in the Messaria shear zone allow the reconstruction of deformation and flow parameters. The mean kinematic vorticity number ranges from 0.13 to 0.80, indicating that shearing deviated significantly from simple shear; that is, extensional shearing was associated with vertical ductile thinning, which contributed to tectonic exhumation. Finite strain shows oblate geometries and axial ratios of the finite-strain ellipse in sections parallel to tectonic transport and normal to the mylonitic foliation range from 1.8 to 19.9. We calculate, using a 1D numerical model, that vertical ductile thinning contributed <em>c</em>. 20% to exhumation during extensional shearing. Normal faulting was the major agent exhuming the footwall from <em>c</em>. 15 km depth.
DOI: 10.6084/m9.figshare.3454265
title: Dinoflagellate cysts and acritarchs from the Oligocene–Lower Miocene interval of the Alma-1X well, Danish North Sea

description: This palynological study of cuttings samples from the Lark Formation in the Danish North Sea well Alma-1X documents for the first time in the public domain the succession of last occurrences of dinoflagellate cysts and acritarchs in the Oligocene–Lower Miocene interval of the Central North Sea. The distribution of dinoflagellates and acritarchs in the well demonstrates the potential for the development of a detailed subdivision of the Oligocene–Lower Miocene in the Central North Sea, based on the first downhole occurrences of key taxa. Five regional intra-Lark Formation seismic and petrophysical log markers can be dated with precision using dinoflagellate biostratigraphy. Four new species and one new subspecies of dinoflagellates are described from the study interval: <em>Amphorosphaeridium</em>? <em>almae</em> sp. nov., <em>Filisphaera pachyderma</em> sp. nov., <em>Pentadinium corium</em> sp. nov., <em>Spiniferites pseudofurcatus verrucosus</em> ssp. nov. and <em>Thalassiphora rota</em> sp. nov<em>. Pseudospiniferites manumii</em> Lund, 2002 is emended and transferred to the genus <em>Spiniferites</em>.
DOI: 10.6084/m9.figshare.3454265.v1
title: Dinoflagellate cysts and acritarchs from the Oligocene–Lower Miocene interval of the Alma-1X well, Danish North Sea

description: This palynological study of cuttings samples from the Lark Formation in the Danish North Sea well Alma-1X documents for the first time in the public domain the succession of last occurrences of dinoflagellate cysts and acritarchs in the Oligocene–Lower Miocene interval of the Central North Sea. The distribution of dinoflagellates and acritarchs in the well demonstrates the potential for the development of a detailed subdivision of the Oligocene–Lower Miocene in the Central North Sea, based on the first downhole occurrences of key taxa. Five regional intra-Lark Formation seismic and petrophysical log markers can be dated with precision using dinoflagellate biostratigraphy. Four new species and one new subspecies of dinoflagellates are described from the study interval: <em>Amphorosphaeridium</em>? <em>almae</em> sp. nov., <em>Filisphaera pachyderma</em> sp. nov., <em>Pentadinium corium</em> sp. nov., <em>Spiniferites pseudofurcatus verrucosus</em> ssp. nov. and <em>Thalassiphora rota</em> sp. nov<em>. Pseudospiniferites manumii</em> Lund, 2002 is emended and transferred to the genus <em>Spiniferites</em>.
DOI: 10.6084/m9.figshare.3454262
title: Volcanic and morphological evolution of La Gomera (Canary Islands), based on new K–Ar ages and magnetic stratigraphy: implications for oceanic island evolution

description: The spatial and chronological evolution of Canary Islands volcanism is due to eastward progression of the slow-moving African plate over a mantle plume. La Gomera is located between the western shield stage islands (&lt;2 Ma) and the central rejuvenated stage islands (&gt;12 Ma). With 23 K–Ar ages and palaeomagnetic data, we can constrain the timing of the main subaerial volcanic phases of La Gomera: the shield volcano (<em>c</em>. 9.4–8.0 Ma), the postshield peripheral lava flows (<em>c</em>. 7.4–5.0 Ma), the postshield horizontal lava flows (<em>c</em>. 5.4–4.3 Ma), and late intra-canyon lava flows (<em>c</em>. 1.9 Ma). The horizontal lava flows fill a 10 km wide depression formed by a giant landslide (Garajonay). The entire structure of La Gomera is in relief inversion. Declining volcanic construction rates from the shield to the postshield stages are correlated with increasing erosion rates, whereas the period of volcanic quiescence (hiatus) has low erosion rates. The succession and duration of the hotspot volcanic stages in the Canary Islands are compared with those in the Hawaiian Islands, thus underlining differences between slow-moving and fast-moving plate settings.
DOI: 10.6084/m9.figshare.3454262.v1
title: Volcanic and morphological evolution of La Gomera (Canary Islands), based on new K–Ar ages and magnetic stratigraphy: implications for oceanic island evolution

description: The spatial and chronological evolution of Canary Islands volcanism is due to eastward progression of the slow-moving African plate over a mantle plume. La Gomera is located between the western shield stage islands (&lt;2 Ma) and the central rejuvenated stage islands (&gt;12 Ma). With 23 K–Ar ages and palaeomagnetic data, we can constrain the timing of the main subaerial volcanic phases of La Gomera: the shield volcano (<em>c</em>. 9.4–8.0 Ma), the postshield peripheral lava flows (<em>c</em>. 7.4–5.0 Ma), the postshield horizontal lava flows (<em>c</em>. 5.4–4.3 Ma), and late intra-canyon lava flows (<em>c</em>. 1.9 Ma). The horizontal lava flows fill a 10 km wide depression formed by a giant landslide (Garajonay). The entire structure of La Gomera is in relief inversion. Declining volcanic construction rates from the shield to the postshield stages are correlated with increasing erosion rates, whereas the period of volcanic quiescence (hiatus) has low erosion rates. The succession and duration of the hotspot volcanic stages in the Canary Islands are compared with those in the Hawaiian Islands, thus underlining differences between slow-moving and fast-moving plate settings.
DOI: 10.6084/m9.figshare.3454259
title: Quantification of exhumation in the Eromanga Basin and its implications for hydrocarbon exploration

description: Exhumation in the Eromanga Basin of South Australia and Queensland has been quantified using compaction methodology. All methods of estimating exhumation utilize rock properties that are affected by, and retain a memory of, burial in excess of that presently observed. The tool used for estimating the exhumation in this study is analysis of the degree of overcompaction of rock units. Since porosity describes compaction state, the sonic log, controlled strongly by the amount of porosity, is an appropriate indicator of compaction and, hence, is used for quantifying exhumation from compaction. The standard method of estimating exhumation based on the degree of overcompaction of a single shale unit has been modified, and seven units, predominantly shales ranging in age from the Cretaceous to the Jurassic, have been analysed. All units yield similar results. Burial at depth greater than currently observed is the most likely cause of overcompaction since it is unlikely that sedimentological and/or diagenetic processes are responsible for similar amounts of overcompaction in different lithologies. The results of the compaction analysis reveal that Late Cretaceous–Tertiary exhumation increases eastwards from the Patchawarra Trough, through the Gidgealpa–Merrimelia–Innamincka Trend and Nappamerri Trough into the Queensland sector of the basins. This study has major implications for hydrocarbon exploration. Predicted maturation of source rocks will be greater for any given geothermal history if exhumation is incorporated in maturation modelling. The exhumation study helps to quantify velocity anomalies associated with overcompaction. Exhumation values can also be used to improve porosity predictions of reservoir units in undrilled targets.
DOI: 10.6084/m9.figshare.3454259.v1
title: Quantification of exhumation in the Eromanga Basin and its implications for hydrocarbon exploration

description: Exhumation in the Eromanga Basin of South Australia and Queensland has been quantified using compaction methodology. All methods of estimating exhumation utilize rock properties that are affected by, and retain a memory of, burial in excess of that presently observed. The tool used for estimating the exhumation in this study is analysis of the degree of overcompaction of rock units. Since porosity describes compaction state, the sonic log, controlled strongly by the amount of porosity, is an appropriate indicator of compaction and, hence, is used for quantifying exhumation from compaction. The standard method of estimating exhumation based on the degree of overcompaction of a single shale unit has been modified, and seven units, predominantly shales ranging in age from the Cretaceous to the Jurassic, have been analysed. All units yield similar results. Burial at depth greater than currently observed is the most likely cause of overcompaction since it is unlikely that sedimentological and/or diagenetic processes are responsible for similar amounts of overcompaction in different lithologies. The results of the compaction analysis reveal that Late Cretaceous–Tertiary exhumation increases eastwards from the Patchawarra Trough, through the Gidgealpa–Merrimelia–Innamincka Trend and Nappamerri Trough into the Queensland sector of the basins. This study has major implications for hydrocarbon exploration. Predicted maturation of source rocks will be greater for any given geothermal history if exhumation is incorporated in maturation modelling. The exhumation study helps to quantify velocity anomalies associated with overcompaction. Exhumation values can also be used to improve porosity predictions of reservoir units in undrilled targets.
DOI: 10.6084/m9.figshare.3454256
title: Timing of tectonic events in the Alpujárride Complex, Betic Cordillera, southern Spain

description: Ar–Ar and fission-track dating from four low-grade sections in the Alpujárride Complex sheds light on the timing of the early contractional history of these high-pressure metamorphic units, and their subsequent exhumation during the early Miocene extensional collapse of the Betic orogen. White mica grains from the lowest-grade rocks yield partly reset detrital Ar–Ar ages; where deformation and recrystallization are more intense, however, they yield reproducible ages as old as <em>c</em>. 48 Ma, which we interpret as the approximate timing of the main contractional event and associated high-pressure metamorphism in these units. Rocks from slightly higher-grade sections give reproducible Ar–Ar ages between 30 and 40 Ma, but these younger ages probably reflect the interplay of growth and cooling in fine-grained micas heated to between 300 °C and 400 °C during prograde metamorphism. In each of the four areas studied the low-grade rocks are separated by an extensional detachment or shear zone from medium-grade rocks below. In two areas these detachments have been folded around major overturned north-vergent folds. Ar–Ar data from structurally below the detachments, and fission-track ages from all structural levels, indicate the onset of significant cooling in the early Miocene, which corresponds to the age of the extensional event. The folds must therefore be early Miocene or younger.
DOI: 10.6084/m9.figshare.3454256.v1
title: Timing of tectonic events in the Alpujárride Complex, Betic Cordillera, southern Spain

description: Ar–Ar and fission-track dating from four low-grade sections in the Alpujárride Complex sheds light on the timing of the early contractional history of these high-pressure metamorphic units, and their subsequent exhumation during the early Miocene extensional collapse of the Betic orogen. White mica grains from the lowest-grade rocks yield partly reset detrital Ar–Ar ages; where deformation and recrystallization are more intense, however, they yield reproducible ages as old as <em>c</em>. 48 Ma, which we interpret as the approximate timing of the main contractional event and associated high-pressure metamorphism in these units. Rocks from slightly higher-grade sections give reproducible Ar–Ar ages between 30 and 40 Ma, but these younger ages probably reflect the interplay of growth and cooling in fine-grained micas heated to between 300 °C and 400 °C during prograde metamorphism. In each of the four areas studied the low-grade rocks are separated by an extensional detachment or shear zone from medium-grade rocks below. In two areas these detachments have been folded around major overturned north-vergent folds. Ar–Ar data from structurally below the detachments, and fission-track ages from all structural levels, indicate the onset of significant cooling in the early Miocene, which corresponds to the age of the extensional event. The folds must therefore be early Miocene or younger.
DOI: 10.6084/m9.figshare.3454253
title: Grenvillian massif-type anorthosites in the Sierras Pampeanas

description: We report the discovery of massif-type anorthosites in the Andean basement of the Western Sierras Pampeanas of Argentina. U–Pb zircon dating (by sensitive high-resolution ion microprobe) of a cogenetic gabbronorite dyke yields ages of 1070 ± 41 Ma for igneous emplacement and 431 ± 40 Ma for metamorphism. These anorthosites are petrologically and geochemically comparable with those of the Grenville province of Laurentia. Palaeogeographical reconstructions of Rodinia at 1.0–1.1 Ga suggest that the Sierras Pampeanas anorthosites were part of a large anorthosite province in the late Mesoproterozoic.
DOI: 10.6084/m9.figshare.3454253.v1
title: Grenvillian massif-type anorthosites in the Sierras Pampeanas

description: We report the discovery of massif-type anorthosites in the Andean basement of the Western Sierras Pampeanas of Argentina. U–Pb zircon dating (by sensitive high-resolution ion microprobe) of a cogenetic gabbronorite dyke yields ages of 1070 ± 41 Ma for igneous emplacement and 431 ± 40 Ma for metamorphism. These anorthosites are petrologically and geochemically comparable with those of the Grenville province of Laurentia. Palaeogeographical reconstructions of Rodinia at 1.0–1.1 Ga suggest that the Sierras Pampeanas anorthosites were part of a large anorthosite province in the late Mesoproterozoic.
DOI: 10.6084/m9.figshare.3454250
title: Formation and emplacement of the Northland ophiolite, northern New Zealand: SW Pacific tectonic implications

description: Petrological, geochemical, geochronological and palaeomagnetic data for rocks of the Northland ophiolite terrane of northern New Zealand suggest that it formed in a suprasubduction-zone setting between <em>c</em>. 29 and 26 Ma, at <em>c</em>. 35°S, close to its Late Oligocene obduction site. Cretaceous igneous rocks formerly considered to be part of the ophiolite probably represent the basement upon which the ophiolite was emplaced, and are probably part of the Mount Camel arc-related terrane. The ophiolite is believed to have been generated in the southeastern South Fiji Basin, close to a NW–SE-oriented transform fault located to the SW of the Vening Meinesz Fracture Zone, and was probably emplaced in response to the collision of the Hikurangi Plateau with eastern New Zealand at the end of the Oligocene. This collision would have involved a major adjustment on the transform fault, thereby allowing a portion of the upper-crustal section of the southern South Fiji Basin to be emplaced southwestward onto northern New Zealand as well as the coeval emplacement of the East Cape Allochthon to the south. Concomitant subduction of the lower crust–mantle section led to the initiation of arc volcanism that resulted in the Northland Lower Miocene volcanic–plutonic suite.
DOI: 10.6084/m9.figshare.3454250.v1
title: Formation and emplacement of the Northland ophiolite, northern New Zealand: SW Pacific tectonic implications

description: Petrological, geochemical, geochronological and palaeomagnetic data for rocks of the Northland ophiolite terrane of northern New Zealand suggest that it formed in a suprasubduction-zone setting between <em>c</em>. 29 and 26 Ma, at <em>c</em>. 35°S, close to its Late Oligocene obduction site. Cretaceous igneous rocks formerly considered to be part of the ophiolite probably represent the basement upon which the ophiolite was emplaced, and are probably part of the Mount Camel arc-related terrane. The ophiolite is believed to have been generated in the southeastern South Fiji Basin, close to a NW–SE-oriented transform fault located to the SW of the Vening Meinesz Fracture Zone, and was probably emplaced in response to the collision of the Hikurangi Plateau with eastern New Zealand at the end of the Oligocene. This collision would have involved a major adjustment on the transform fault, thereby allowing a portion of the upper-crustal section of the southern South Fiji Basin to be emplaced southwestward onto northern New Zealand as well as the coeval emplacement of the East Cape Allochthon to the south. Concomitant subduction of the lower crust–mantle section led to the initiation of arc volcanism that resulted in the Northland Lower Miocene volcanic–plutonic suite.
DOI: 10.6084/m9.figshare.3454244
title: Provenance and age constraints of the South Stack Group, Anglesey, UK: U–Pb SIMS detrital zircon data.

description: U–Th–Pb Secondary Ion Mass Spectrometry (SIMS) data from detrital zircons extracted from the South Stack Group, Anglesey, UK, indicate that: (1) the maximum depositional age of the Holyhead Formation (South Stack Group, Monian Supergroup) is 501 ± 10 Ma; (2) the Monian Supergroup was deposited between <strong><em>c.</em></strong> 500 and 475 Ma and is part of the Cambrian–Lower Ordovician succession found in southern Britain and Ireland; (3) Avalonia was a major sediment source (age maxima at 543–552 and 604–627 Ma); (4) Amazonia probably also provided zircons (common Neoarchaean–Mesoproterozoic grains) weakening suggestions that Avalonia had rifted off Gondwana by Cambrian times.
DOI: 10.6084/m9.figshare.3454244.v1
title: Provenance and age constraints of the South Stack Group, Anglesey, UK: U–Pb SIMS detrital zircon data.

description: U–Th–Pb Secondary Ion Mass Spectrometry (SIMS) data from detrital zircons extracted from the South Stack Group, Anglesey, UK, indicate that: (1) the maximum depositional age of the Holyhead Formation (South Stack Group, Monian Supergroup) is 501 ± 10 Ma; (2) the Monian Supergroup was deposited between <strong><em>c.</em></strong> 500 and 475 Ma and is part of the Cambrian–Lower Ordovician succession found in southern Britain and Ireland; (3) Avalonia was a major sediment source (age maxima at 543–552 and 604–627 Ma); (4) Amazonia probably also provided zircons (common Neoarchaean–Mesoproterozoic grains) weakening suggestions that Avalonia had rifted off Gondwana by Cambrian times.
DOI: 10.6084/m9.figshare.3454241
title: Isotopic signals from late Jurassic–early Cretaceous (Volgian–Valanginian) sub-Arctic belemnites, Yatria River, Western Siberia

description: This contribution presents the first detailed oxygen and carbon isotope record from the latest Jurassic–early Cretaceous interval of the Yatria River, subpolar Urals, Siberia. Isotopic compositions have been determined on well-preserved belemnite samples from the genera <em>Lagonibelus</em>, <em>Cylindroteuthis</em> and <em>Acroteuthis</em>. These new data indicate a shift to lower temperatures from the late Volgian into the late Valanginian, with some warmer phases recognized within the Ryazanian and earliest Valanginian. The lowest temperatures of the late Valanginian, consistent with subfreezing polar temperatures, are coincident with an inferred eustatic sea-level fall. A late Valanginian positive shift in carbon isotopes correlates with the carbon isotope excursion recorded from Tethyan successions. The most positive carbon isotope values correspond to the most positive oxygen isotope values (and hence lowest palaeotemperatures). In the absence of widespread Valanginian organic-rich black shale deposition, the carbon isotope excursion may point to increased storage of organic carbon in coastal areas and/or enhanced preservation within stratified waters in high-latitude basins. At these higher latitudes, where rates of weathering were presumably much lower because of the prevalent cold climate, the isotopic data may point to pulses of productivity being brought about by increased riverine nutrient transfer and also by nutrients being released by the melting of ice. The correlation between positive carbon isotopes and cool climates may indicate the effectiveness of these high-latitude carbon sinks and their ability to draw down atmospheric CO<sub>2</sub>, resulting in an ‘inverse greenhouse’ effect.
DOI: 10.6084/m9.figshare.3454241.v1
title: Isotopic signals from late Jurassic–early Cretaceous (Volgian–Valanginian) sub-Arctic belemnites, Yatria River, Western Siberia

description: This contribution presents the first detailed oxygen and carbon isotope record from the latest Jurassic–early Cretaceous interval of the Yatria River, subpolar Urals, Siberia. Isotopic compositions have been determined on well-preserved belemnite samples from the genera <em>Lagonibelus</em>, <em>Cylindroteuthis</em> and <em>Acroteuthis</em>. These new data indicate a shift to lower temperatures from the late Volgian into the late Valanginian, with some warmer phases recognized within the Ryazanian and earliest Valanginian. The lowest temperatures of the late Valanginian, consistent with subfreezing polar temperatures, are coincident with an inferred eustatic sea-level fall. A late Valanginian positive shift in carbon isotopes correlates with the carbon isotope excursion recorded from Tethyan successions. The most positive carbon isotope values correspond to the most positive oxygen isotope values (and hence lowest palaeotemperatures). In the absence of widespread Valanginian organic-rich black shale deposition, the carbon isotope excursion may point to increased storage of organic carbon in coastal areas and/or enhanced preservation within stratified waters in high-latitude basins. At these higher latitudes, where rates of weathering were presumably much lower because of the prevalent cold climate, the isotopic data may point to pulses of productivity being brought about by increased riverine nutrient transfer and also by nutrients being released by the melting of ice. The correlation between positive carbon isotopes and cool climates may indicate the effectiveness of these high-latitude carbon sinks and their ability to draw down atmospheric CO<sub>2</sub>, resulting in an ‘inverse greenhouse’ effect.