cometadata/datacite-titles-descriptions-related-identifiers huggingface dataset:
DOI: 10.6084/m9.figshare.3454130.v1
title: Evidence from Rb–Sr mineral ages for multiple orogenic events in the Caledonides of Shetland, Scotland

description: Shetland occupies a unique central location within the North Atlantic Caledonides. Thirty-three new high-precision Rb–Sr mineral ages indicate a polyorogenic history. Ages of 723–702 Ma obtained from the vicinity of the Wester Keolka Shear Zone indicate a Neoproterozoic (Knoydartian) age and preclude its correlation with the Silurian Moine Thrust. Ordovician ages of <em>c</em>. 480–443 Ma obtained from the Yell Sound Group and the East Mainland Succession constrain deformation fabrics and metamorphic assemblages to have formed during Grampian accretionary orogenic events, broadly contemporaneously with orogenesis of the Dalradian Supergroup in Ireland and mainland Scotland. The relative paucity of Silurian ages is attributed to a likely location at a high structural level in the Scandian nappe pile relative to mainland Scotland. Ages of <em>c</em>. 416 and <em>c</em>. 411 Ma for the Uyea Shear Zone suggest a late orogenic evolution that has more in common with East Greenland and Norway than with northern mainland Scotland. <strong>Supplementary material:</strong> Detailed appraisal of biotite petrography is available at http://www.geolsoc.org.uk/SUP18887.
DOI: 10.6084/m9.figshare.3454127
title: Reconnaissance thermochronology of southern Zealandia

description: We report new fission-track, (U–Th)/He and <sup>40</sup>Ar/<sup>39</sup>Ar ages for minerals in surface, dredge and borehole cuttings samples from the southern South Island, Campbell Plateau and Chatham Rise regions of the Zealandia continent. Our results indicate that much of southern Zealandia underwent rapid cooling in the interval 105–80 Ma, probably during widespread intracontinental rifting before Zealandia split from Gondwana. The 108 ± 11 Ma rapid exhumation of a zircon He retention zone in the Chatham Schist, however, may record cessation of long-lived subduction at the Gondwana margin owing to Hikurangi Plateau collision and/or the onset of the extensional rifting episode. Locally, basement rocks have been appreciably heated, and thermochronological systems reset, in response to deepening of the Great South Basin and by local Miocene intraplate volcanism. An apatite fission-track age of 179 ± 17 Ma from a dredge sample of Precambrian granite at the southern tip of the Campbell Plateau indicates that it is probably ice-rafted, thus <em>in situ</em> Precambrian crust in Zealandia is still unconfirmed. In contrast, a zircon (U–Th)/He age of 99 ± 9 Ma from a Precambrian metarhyolite from Iselin Bank at the conjugate Antarctic continental margin plausibly indicates an <em>in situ</em> position.
DOI: 10.6084/m9.figshare.3454127.v1
title: Reconnaissance thermochronology of southern Zealandia

description: We report new fission-track, (U–Th)/He and <sup>40</sup>Ar/<sup>39</sup>Ar ages for minerals in surface, dredge and borehole cuttings samples from the southern South Island, Campbell Plateau and Chatham Rise regions of the Zealandia continent. Our results indicate that much of southern Zealandia underwent rapid cooling in the interval 105–80 Ma, probably during widespread intracontinental rifting before Zealandia split from Gondwana. The 108 ± 11 Ma rapid exhumation of a zircon He retention zone in the Chatham Schist, however, may record cessation of long-lived subduction at the Gondwana margin owing to Hikurangi Plateau collision and/or the onset of the extensional rifting episode. Locally, basement rocks have been appreciably heated, and thermochronological systems reset, in response to deepening of the Great South Basin and by local Miocene intraplate volcanism. An apatite fission-track age of 179 ± 17 Ma from a dredge sample of Precambrian granite at the southern tip of the Campbell Plateau indicates that it is probably ice-rafted, thus <em>in situ</em> Precambrian crust in Zealandia is still unconfirmed. In contrast, a zircon (U–Th)/He age of 99 ± 9 Ma from a Precambrian metarhyolite from Iselin Bank at the conjugate Antarctic continental margin plausibly indicates an <em>in situ</em> position.
DOI: 10.6084/m9.figshare.3454124
title: An example of low-Th/U zircon overgrowths of magmatic origin in a late orogenic Variscan intrusion: the San Ciprián massif (NW Spain)

description: Th/U values in zircon are commonly used to discriminate between metamorphic (Th/U 0.1) origin for zircon overgrowths. We test this hypothesis in the San Ciprián massif, a late orogenic granitic intrusion in the hinterland of the Variscan orogeny. Zircon grains from this granite have cores with inherited Ediacaran ages and Th/U &gt; 0.1, whereas zircon mantles yield an age of about 287 Ma, interpreted as the time of crystallization of the granite, and have Th/U
DOI: 10.6084/m9.figshare.3454124.v1
title: An example of low-Th/U zircon overgrowths of magmatic origin in a late orogenic Variscan intrusion: the San Ciprián massif (NW Spain)

description: Th/U values in zircon are commonly used to discriminate between metamorphic (Th/U 0.1) origin for zircon overgrowths. We test this hypothesis in the San Ciprián massif, a late orogenic granitic intrusion in the hinterland of the Variscan orogeny. Zircon grains from this granite have cores with inherited Ediacaran ages and Th/U &gt; 0.1, whereas zircon mantles yield an age of about 287 Ma, interpreted as the time of crystallization of the granite, and have Th/U
DOI: 10.6084/m9.figshare.3454121
title: U–Pb and Lu–Hf zircon data in young sediments reflect sedimentary recycling in eastern South Africa

description: Detrital zircon from unconsolidated, Cenozoic sediments from eastern South Africa has been analysed for U–Pb and Lu–Hf isotopes by laser ablation inductively coupled plasma mass spectrometry. Identifiable bedrock sources have made local contributions to the detrital zircon populations, but the dominant zircon components are of regional distribution: late Mesoproterozoic (ε<sub>Hf</sub> = –5 to +10), Neoproterozoic to early Palaeozoic (ε<sub>Hf</sub> = –10 to +10), and minor late Palaeozoic (ε<sub>Hf</sub> ≈ 0). Archaean zircons are scarce even in sediments deposited on exposed Archaean basement or by rivers eroding it. The dominant components cannot be tied to specific first-generation sources in southern Africa or its former Gondwana neighbours. Instead, we see the effect of mixing and remobilization of debris from large parts of the supercontinent in the early Phanerozoic, which was stored in the Karoo basin and other continental cover sequences and shed from there to the present site of deposition. Therefore, data from detrital zircon in these deposits tell us less about the path of detritus from source to sink in a recent sedimentary system than about processes in much earlier erosion–transport–deposition cycles. To facilitate comparison of detrital zircon age distribution patterns, a simple and intuitive method that takes sampling uncertainty explicitly into account is proposed.
DOI: 10.6084/m9.figshare.3454115
title: Detrital zircon in a supercontinental setting: locally derived and far-transported components in the Ordovician Natal Group, South Africa

description: U–Pb and Lu–Hf signatures of detrital zircon from conglomerates and sandstones of the Ordovician Natal Group, South Africa were determined using laser ablation inductively coupled plasma mass spectrometry. The basal conglomerates are dominated by Palaeo- to Mesoarchaean detrital zircon with ε<sub>Hf</sub> values from +3 to −4 with minor Mesoproterozoic input, indicating a proximal source in the Kaapvaal Craton and minor input from rocks of the Natal Sector of the Mesoproterozoic Namaqua–Natal Province. The sandstones are all dominated by a combination of juvenile Mesoproterozoic zircon and Neoproterozoic zircon derived from Mesoproterozoic rocks that were reworked during the Pan-African Orogeny. Several sedimentary sequences from former Gondwana with Neoproterozoic to Permian depositional ages show similar detrital zircon signatures. Sedimentary sequences of such vast temporal and geographical distribution are unlikely to have been fed by a single source, making it more likely that these sequences were fed by several different (Pan-Gondwana) source terranes with closely similar U–Pb and Lu–Hf zircon signatures. The results show that source terrane non-uniqueness can make ascertaining sedimentary provenance from detrital zircon impossible, and should be taken as a reminder when using detrital zircon as evidence for far-reaching conclusions in basin evolution studies and palaeogeography.
DOI: 10.6084/m9.figshare.3454109
title: Synchronous Last Glacial Maximum across the Anatolian peninsula

description: Uludağ is a prominent mountain in northwestern Turkey where glacial deposits have been documented in the Kovuk Valley and the glacial history has been reconstructed based on 31 cosmogenic <sup>10</sup>Be exposure ages from glacially transported boulders and bedrock. The results suggest that the Kovuk Glacier began advancing before 26.5±1.6 ka. It reached its maximum extent at 20.3±1.3 ka, followed by a re-advance at 19.3±1.2 ka, both during the global Last Glacial Maximum (LGM) within Marine Isotope Stage 2. The timing of the LGM glaciations in the Kovuk Valley is consistent with the investigated LGM glaciations in other mountains of Anatolia, the Mediterranean and the Alps. Based on the geomorphological ice margin reconstruction and using the accumulation/ablation area ratio (AAR) approach, the equilibrium line altitude (ELA) of the Kovuk LGM glacier was <em>c.</em> 2000 m above sea level for an estimated AAR of 0.67. This indicates a <em>c.</em> 1000 m lowering of the ELA for the LGM compared with the modern ELA estimate. These lines of evidence are consistent with the LGM glaciers that have been documented elsewhere in the Anatolian Mountains.
DOI: 10.6084/m9.figshare.3454109.v1
title: Synchronous Last Glacial Maximum across the Anatolian peninsula

description: Uludağ is a prominent mountain in northwestern Turkey where glacial deposits have been documented in the Kovuk Valley and the glacial history has been reconstructed based on 31 cosmogenic <sup>10</sup>Be exposure ages from glacially transported boulders and bedrock. The results suggest that the Kovuk Glacier began advancing before 26.5±1.6 ka. It reached its maximum extent at 20.3±1.3 ka, followed by a re-advance at 19.3±1.2 ka, both during the global Last Glacial Maximum (LGM) within Marine Isotope Stage 2. The timing of the LGM glaciations in the Kovuk Valley is consistent with the investigated LGM glaciations in other mountains of Anatolia, the Mediterranean and the Alps. Based on the geomorphological ice margin reconstruction and using the accumulation/ablation area ratio (AAR) approach, the equilibrium line altitude (ELA) of the Kovuk LGM glacier was <em>c.</em> 2000 m above sea level for an estimated AAR of 0.67. This indicates a <em>c.</em> 1000 m lowering of the ELA for the LGM compared with the modern ELA estimate. These lines of evidence are consistent with the LGM glaciers that have been documented elsewhere in the Anatolian Mountains.
DOI: 10.6084/m9.figshare.3454106
title: Cosmogenic <sup>36</sup>Cl geochronology of late Quaternary glaciers in the Bolkar Mountains, south central Turkey

description: We present the first quantitative late Quaternary cosmogenic <sup>36</sup>Cl glacial geochronology from the Bolkar Mountains of south central Turkey. Thirty samples were collected from three glaciated valleys. The geomorphological investigations indicate that the palaeoglaciers deposited their moraines between 3200 and 2200 m above sea level on the north- and south-facing valleys. We recognize four glacial periods, with the oldest one dating back to about 46.0±7.0 ka in the northern Karagöl Valley. Later, glaciers reached their maximum positions (∼5.5 km from cirque to snout) by 18.9±3.3 ka (during the local Last Glacial Maximum; LGM) in the Karagöl Valley. Late-glacial moraines were dated to between 15.2±1.6 and 12.6±2.3 ka in both northern Alagöl and southern Elmalı Valleys, respectively. The final deglaciation in the mountain commenced in the early Holocene (9.0±0.9 ka in the Karagöl Valley; 8.5±1.8 ka in the Elmalı Valley). A contemporaneous outwash plain dates to 8.4±1.0 ka at the outlet of the Alagöl Valley. Our results agree well with the glacial chronologies obtained from other Turkish and Mediterranean mountains.
DOI: 10.6084/m9.figshare.3454106.v1
title: Cosmogenic <sup>36</sup>Cl geochronology of late Quaternary glaciers in the Bolkar Mountains, south central Turkey

description: We present the first quantitative late Quaternary cosmogenic <sup>36</sup>Cl glacial geochronology from the Bolkar Mountains of south central Turkey. Thirty samples were collected from three glaciated valleys. The geomorphological investigations indicate that the palaeoglaciers deposited their moraines between 3200 and 2200 m above sea level on the north- and south-facing valleys. We recognize four glacial periods, with the oldest one dating back to about 46.0±7.0 ka in the northern Karagöl Valley. Later, glaciers reached their maximum positions (∼5.5 km from cirque to snout) by 18.9±3.3 ka (during the local Last Glacial Maximum; LGM) in the Karagöl Valley. Late-glacial moraines were dated to between 15.2±1.6 and 12.6±2.3 ka in both northern Alagöl and southern Elmalı Valleys, respectively. The final deglaciation in the mountain commenced in the early Holocene (9.0±0.9 ka in the Karagöl Valley; 8.5±1.8 ka in the Elmalı Valley). A contemporaneous outwash plain dates to 8.4±1.0 ka at the outlet of the Alagöl Valley. Our results agree well with the glacial chronologies obtained from other Turkish and Mediterranean mountains.
DOI: 10.6084/m9.figshare.3454103
title: The geology and tectonics of central Bhutan

description: Lithotectonic mapping, metamorphic observations and U–Pb zircon ages underpin a substantial revision of central Bhutan geology, notably a more extensive and continuous outcrop of the Tethyan Sedimentary Series (TSS) than previously mapped. Metamorphic grade in the TSS increases downward towards a basal north-vergent tectonic contact with the underlying Greater Himalayan Series (GHS), interpreted as a southward continuation of the South Tibetan Detachment (STD). Miocene (<em>c</em>. 17–20 Ma) leucogranite sheets are associated with the STD in this region but appear to diminish southwards. Two leucogranite dykes that cross-cut TSS structures yield ages of 17.8 ± 0.2 and 17.9 ± 0.5 Ma. A 500 ± 4 Ma (U–Pb zircon) metamorphosed ash bed in the Pele La Group within the psammite-dominated lower TSS yields the first direct isotopic age for the TSS in the eastern Himalaya, confirming existing age constraints from detrital zircon and fossil studies. A continuation of the Paro metasedimentary unit underlying the GHS was mapped near Wangdue Phodrang. Our observations, notably the exposure of a wholly ductile STD so far south and the significance of large nappe-like structures in the TSS, prompt a major revision to the geological map of the Bhutan Himalaya and require a reassessment of tectonic interpretations of the Bhutan Himalaya.
DOI: 10.6084/m9.figshare.3454103.v1
title: The geology and tectonics of central Bhutan

description: Lithotectonic mapping, metamorphic observations and U–Pb zircon ages underpin a substantial revision of central Bhutan geology, notably a more extensive and continuous outcrop of the Tethyan Sedimentary Series (TSS) than previously mapped. Metamorphic grade in the TSS increases downward towards a basal north-vergent tectonic contact with the underlying Greater Himalayan Series (GHS), interpreted as a southward continuation of the South Tibetan Detachment (STD). Miocene (<em>c</em>. 17–20 Ma) leucogranite sheets are associated with the STD in this region but appear to diminish southwards. Two leucogranite dykes that cross-cut TSS structures yield ages of 17.8 ± 0.2 and 17.9 ± 0.5 Ma. A 500 ± 4 Ma (U–Pb zircon) metamorphosed ash bed in the Pele La Group within the psammite-dominated lower TSS yields the first direct isotopic age for the TSS in the eastern Himalaya, confirming existing age constraints from detrital zircon and fossil studies. A continuation of the Paro metasedimentary unit underlying the GHS was mapped near Wangdue Phodrang. Our observations, notably the exposure of a wholly ductile STD so far south and the significance of large nappe-like structures in the TSS, prompt a major revision to the geological map of the Bhutan Himalaya and require a reassessment of tectonic interpretations of the Bhutan Himalaya.
DOI: 10.6084/m9.figshare.3454094
title: Gondwana break-up related magmatism in the Falkland Islands

description: Jurassic dykes (<em>c</em>. 182 Ma) are widespread across the Falkland Islands and exhibit considerable geochemical variability. Orthopyroxene-bearing NW–SE-oriented quartz-tholeiite dykes underwent fractional crystallization at &gt;1 GPa, and major element constraints suggest that they were derived by melting of a pyroxenite-rich source. They have εNd<sub>182</sub> in the range −6 to −11 and <sup>87</sup>Sr/<sup>86</sup>Sr<sub>182</sub> &gt;0.710 and therefore require an old lithospheric component in their source. A suite of basaltic-andesites and andesites exhibit geochemical compositions transitional between Ferrar and Karoo magma types, and are similar to those seen in the KwaZulu-Natal region of southern Africa and the Theron Mountains of Antarctica. Olivine-phyric intrusions equilibrated at &lt;0.5 GPa, and have isotopic compositions (εNd<sub>182</sub> 1.6–3.6 and <sup>87</sup>Sr/<sup>86</sup>Sr<sub>182</sub> 0.7036–0.7058) that require limited interaction with old continental lithosphere. A suite of plagioclase-phyric intrusions with <sup>87</sup>Sr/<sup>86</sup>Sr<sub>182</sub> <em>c</em>. 0.7035 and εNd<sub>182</sub> <em>c</em>. +4, and low Th/Ta and La/Ta ratios (<em>c</em>. 1 and <em>c</em>. 15, respectively) also largely escaped interaction with the lithosphere. These isotopically depleted intrusions were probably emplaced synchronously with Gondwana fragmentation and the formation of new oceanic lithosphere. Estimates of mantle potential temperature from olivine equilibration temperatures do not provide unequivocal evidence for the presence of a plume thermal anomaly beneath the Falkland Islands at 182 Ma.
DOI: 10.6084/m9.figshare.3454094.v1
title: Gondwana break-up related magmatism in the Falkland Islands

description: Jurassic dykes (<em>c</em>. 182 Ma) are widespread across the Falkland Islands and exhibit considerable geochemical variability. Orthopyroxene-bearing NW–SE-oriented quartz-tholeiite dykes underwent fractional crystallization at &gt;1 GPa, and major element constraints suggest that they were derived by melting of a pyroxenite-rich source. They have εNd<sub>182</sub> in the range −6 to −11 and <sup>87</sup>Sr/<sup>86</sup>Sr<sub>182</sub> &gt;0.710 and therefore require an old lithospheric component in their source. A suite of basaltic-andesites and andesites exhibit geochemical compositions transitional between Ferrar and Karoo magma types, and are similar to those seen in the KwaZulu-Natal region of southern Africa and the Theron Mountains of Antarctica. Olivine-phyric intrusions equilibrated at &lt;0.5 GPa, and have isotopic compositions (εNd<sub>182</sub> 1.6–3.6 and <sup>87</sup>Sr/<sup>86</sup>Sr<sub>182</sub> 0.7036–0.7058) that require limited interaction with old continental lithosphere. A suite of plagioclase-phyric intrusions with <sup>87</sup>Sr/<sup>86</sup>Sr<sub>182</sub> <em>c</em>. 0.7035 and εNd<sub>182</sub> <em>c</em>. +4, and low Th/Ta and La/Ta ratios (<em>c</em>. 1 and <em>c</em>. 15, respectively) also largely escaped interaction with the lithosphere. These isotopically depleted intrusions were probably emplaced synchronously with Gondwana fragmentation and the formation of new oceanic lithosphere. Estimates of mantle potential temperature from olivine equilibration temperatures do not provide unequivocal evidence for the presence of a plume thermal anomaly beneath the Falkland Islands at 182 Ma.
DOI: 10.6084/m9.figshare.3454088
title: The Egiin Davaa prehistoric rupture, central Mongolia: a large magnitude normal faulting earthquake on a reactivated fault with little cumulative slip located in a slowly deforming intraplate setting

description: The prehistoric Egiin Davaa earthquake rupture is well-preserved in late Quaternary deposits within the Hangay Mountains of central Mongolia. The rupture is expressed by a semi-continuous 80 km-long topographic scarp. Geomorphological reconstructions reveal a relatively constant scarp height of 4–4.5 m and a NW-directed slip vector. Previous researchers have suggested that the scarp's exceptional geomorphological preservation indicates that it may correspond to an earthquake that occurred in the region <em>c.</em> 500 years ago. However, we constrain the last rupture to have been at least 4 ka ago from morphological dating and &lt;7.4 ka ago based on radiocarbon dating from one of two palaeoseismic trenches. Our study shows that discrete earthquake ruptures, along with details such as the locations of partially infilled fissures, can be preserved for periods well in excess of 1000 years in the interior of Asia, providing an archive of fault movements that can be directly read from the Earth's surface over a timescale appropriate for the study of slowly deforming continental interiors. The Egiin Davaa rupture involved <em>c.</em> 8 m of slip which, along with the observations that it is largely unsegmented along its length and that the ratio of cumulative slip (<em>c.</em> 250 m) to fault length (<em>c.</em> 80 km) is small, suggests relatively recent reactivation of a pre-existing geological structure.
DOI: 10.6084/m9.figshare.3454088.v1
title: The Egiin Davaa prehistoric rupture, central Mongolia: a large magnitude normal faulting earthquake on a reactivated fault with little cumulative slip located in a slowly deforming intraplate setting

description: The prehistoric Egiin Davaa earthquake rupture is well-preserved in late Quaternary deposits within the Hangay Mountains of central Mongolia. The rupture is expressed by a semi-continuous 80 km-long topographic scarp. Geomorphological reconstructions reveal a relatively constant scarp height of 4–4.5 m and a NW-directed slip vector. Previous researchers have suggested that the scarp's exceptional geomorphological preservation indicates that it may correspond to an earthquake that occurred in the region <em>c.</em> 500 years ago. However, we constrain the last rupture to have been at least 4 ka ago from morphological dating and &lt;7.4 ka ago based on radiocarbon dating from one of two palaeoseismic trenches. Our study shows that discrete earthquake ruptures, along with details such as the locations of partially infilled fissures, can be preserved for periods well in excess of 1000 years in the interior of Asia, providing an archive of fault movements that can be directly read from the Earth's surface over a timescale appropriate for the study of slowly deforming continental interiors. The Egiin Davaa rupture involved <em>c.</em> 8 m of slip which, along with the observations that it is largely unsegmented along its length and that the ratio of cumulative slip (<em>c.</em> 250 m) to fault length (<em>c.</em> 80 km) is small, suggests relatively recent reactivation of a pre-existing geological structure.