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| Open AccessTectonic control on the persistence of glacially sculpted topography
U-shaped glacial valleys dominate >10 ka since the last major glaciation and the transitions from glacier-dominated to fluvial regimes are poorly understood. Here, the authors use digital topographic data to show that glacial topography is rapidly replaced by fluvial topography where rock uplift rates are high.
- Günther Prasicek
- , Isaac J. Larsen
- & David R. Montgomery
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Exceptional river gorge formation from unexceptional floods
Previous studies suggest that rates of gorge formation are controlled by bedrock erodibility, erosion mechanism and hillslope processes. Here, the authors show evidence of rapid gorge formation in granite bedrock and report no relationship with flood size or bedload, attributing the rate to pre-existing jointing.
- L. Anton
- , A. E. Mather
- & G. De Vicente
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| Open AccessHail formation triggers rapid ash aggregation in volcanic plumes
The behaviour of airborne fine ash during explosive volcanic eruptions is poorly understood. Here, the authors study hail formation during an eruption, proposing a mechanism of particle aggregation that leads to the fallout of fine ash and the occurrence of concentrically layered aggregates in volcanic deposits
- Alexa R. Van Eaton
- , Larry G. Mastin
- & Amanda B. Clarke
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Article
| Open AccessAntiquity of the South Atlantic Anomaly and evidence for top-down control on the geodynamo
The rapid decay of Earth’s dipole magnetic field has recently captured the public imagination. Here, the authors present a southern hemisphere magnetic record from South African Iron Age sites using oriented samples in the floors and suggest that the anomalous field behaviour is not just a recent feature.
- John A. Tarduno
- , Michael K. Watkeys
- & Courtney L. Wagner
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| Open AccessGeologic controls on supercritical geothermal resources above magmatic intrusions
Utilizing supercritical geothermal water could multiply energy production, but the abundance, location and size of such resources is unclear. Here, the authors present numerical simulations and suggest that supercritical water may play a key role in removing heat from all magmatic intrusions.
- Samuel Scott
- , Thomas Driesner
- & Philipp Weis
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| Open AccessHow and when plume zonation appeared during the 132 Myr evolution of the Tristan Hotspot
Striped geochemical zonation has been observed along parts of hotspot tracks, although its origin is not well-understood. Here, the authors present Sr–Nd–Pb–Hf isotope data and present a model that can explain the evolution of zonation in both Tristan-Gough and Hawaiian hotspots, reflecting two end members.
- Kaj Hoernle
- , Joana Rohde
- & Jason P. Morgan
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Continental flood basalts derived from the hydrous mantle transition zone
The Earth’s mantle transition zone may play a key role in large-scale intraplate magmatism and plate tectonics. Here, the authors provide evidence for the origin of continental flood basalts in this zone, by combining oxygen isotope and geochemical evidence from the late Cenozoic Chifeng volcanics of East Asia.
- Xuan-Ce Wang
- , Simon A. Wilde
- & Ya-Nan Yang
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| Open AccessNew streams and springs after the 2014 Mw6.0 South Napa earthquake
Following the Mw6 South Napa earthquake in California, previously dry streams and springs began to flow. Here, the authors present data from repeated stream surveys and laboratory measurements and suggest that the new flows originated from groundwater in the mountains and were released by the earthquake.
- Chi-Yuen Wang
- & Michael Manga
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| Open AccessExtensive volatile loss during formation and differentiation of the Moon
Recent studies suggest that the Moon is not as volatile-poor as once thought, and that volatile elements should be concentrated in crustal materials. Here, the authors present Zn isotopic and abundance data as evidence of evaporative loss of volatiles during formation of the Moon, supporting alternative models.
- Chizu Kato
- , Frederic Moynier
- & James M.D. Day
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| Open AccessVariable Holocene deformation above a shallow subduction zone extremely close to the trench
Information regarding tectonic motion from before instrumental records can be found from palaeoshorelines and the reconstruction of sea level from observations. Here, the authors study corals uplifted by past earthquakes near the Solomon Islands and assess the Holocene deformation that took place there.
- Kaustubh Thirumalai
- , Frederick W. Taylor
- & Alison K. Papabatu
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| Open AccessLow-buoyancy thermochemical plumes resolve controversy of classical mantle plume concept
The classic mantle plume concept explains large igneous provinces and hotspot magmatism, but often contradicts observed surface uplift and plume morphology. Here, the authors present a plume model that better supports observations by considering low-buoyancy plumes containing up to 15% of recycled oceanic crust.
- Juliane Dannberg
- & Stephan V. Sobolev
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| Open AccessCausal factors for seismicity near Azle, Texas
Whether exploration causes earthquakes has been a matter of recent contention particularly regarding shale gas exploration. Here, the authors use hydraulic modelling and earthquake locations to show that brine production and wastewater injection in the Azle area are likely causing earthquakes.
- Matthew J. Hornbach
- , Heather R. DeShon
- & James H. Luetgert
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Did diamond-bearing orangeites originate from MARID-veined peridotites in the lithospheric mantle?
Due to entrainment of mantle and crustal fragments, orangeites provide information about the deep Earth; however, the nature of the source of orangeites remains uncertain. Here, the authors suggest that mica-amphibole-rutile-ilmenite-diopside (MARID) enriched mantle produces the orangeite magmas.
- Andrea Giuliani
- , David Phillips
- & Richard A. Armstrong
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Cracks in Martian boulders exhibit preferred orientations that point to solar-induced thermal stress
Many rock cracks on Earth point north, suggesting that the Sun may be involved in their formation. Here, the authors compile this Earth data, collect similar data for rock cracks on Mars, and present modelling results, linking the origin of Mars rock cracks to thermal stress from the Sun.
- Martha-Cary Eppes
- , Andrew Willis
- & Beibei Zhou
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Selective ingress of a Samoan plume component into the northern Lau backarc basin
Ocean island basalts contain primordial and recycled crustal components, sourced from the deep mantle by plumes. Here, the authors examine Hf-Nd-He isotopes in ocean floor basalts south of Samoa and suggest that selective ingress of only the primordial component from the Samoan plume can occur.
- Oliver Nebel
- & Richard J. Arculus
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Micro-trace fossils reveal pervasive reworking of Pliocene sapropels by low-oxygen-adapted benthic meiofauna
Meiofaunal burrowing is thought to produce sediment textures that appear devoid of animal activity, thus the record of meiofaunal activity remains unknown. Here, the authors apply a novel sampling and electron imaging approach to identify meiofaunal traces in Pliocene sapropels, a classic anoxic facies.
- S.C. Löhr
- & M.J. Kennedy
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Tetrahedrally coordinated carbonates in Earth’s lower mantle
The behaviour of subducted carbonates at high pressures within the Earth is still poorly understood. Here, the authors present experimental and theoretical evidence of a new carbon–oxygen bond in a high-pressure mineral phase, which has implications for the viscosity and mobility of carbonate melts.
- Eglantine Boulard
- , Ding Pan
- & Wendy L. Mao
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| Open AccessThe pervasive role of biological cohesion in bedform development
The role of cohesion is vital to our understanding of how sedimentary bedforms evolve. Here, the authors show that microorganisms within the sediment affect cohesion and demonstrate that ripples can take up to one hundred times as long to develop when extracellular polymeric substances are present.
- Jonathan Malarkey
- , Jaco H. Baas
- & Peter D. Thorne
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A very long-term transient event preceding the 2011 Tohoku earthquake
Slow slip events have been observed in different subduction zones, but their relationship to megathrust earthquakes remains elusive. Here, the authors postulate that a transient event may have led to the 2011 Tohoku earthquake as the hypocentre falls within a zone of positive Coloumb stress change.
- Yusuke Yokota
- & Kazuki Koketsu
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High-pressure radiative conductivity of dense silicate glasses with potential implications for dark magmas
Understanding of the Earth’s interior requires insight into the thermal properties of silicate melts under high pressure. Here, the authors present high-pressure spectroscopic measurements of iron-enriched dense silicate glasses and infer the radiative conductivity of dense melts at the core–mantle boundary.
- Motohiko Murakami
- , Alexander F. Goncharov
- & Craig R. Bina
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Interpreting carbonate and organic carbon isotope covariance in the sedimentary record
To date, covariance of carbonate and organic carbon isotope records has been assumed to denote fidelity of the original signal. This study shows that post-depositional alteration can create strong correlations, raising doubts about the use of correlated records to imply important changes in past global carbon cycling.
- Amanda M. Oehlert
- & Peter K. Swart
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Evidence for the alkaline nature of parental carbonatite melts at Oka complex in Canada
With the exception of one occurrence, carbonatites worldwide are curiously deficient in alkalis. Here, Chen et al.present new melt inclusion data from plutonic relics in Canada that hint at a wider prevalence of alkali-enriched parental carbonatite in the geological record than previously thought.
- Wei Chen
- , Vadim S. Kamenetsky
- & Antonio Simonetti
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| Open AccessSequestration of Martian CO2 by mineral carbonation
The mechanism by which Mars lost its early dense and carbon dioxide-rich atmosphere remains relatively unknown. Here, via mineralogical analysis of the Lafayette Martian meteorite, Tomkinson et al. infer that carbonation was an effective carbon dioxide sequestration mechanism on an early, water-rich Mars.
- Tim Tomkinson
- , Martin R. Lee
- & Caroline L. Smith
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| Open AccessOsmium isotope evidence for a large Late Triassic impact event
Before the mass extinction that characterized the Late Triassic period, there were a series of biotic turnover events, the cause of which are the subject of debate. Sato et al. present geochemical evidence in support of the theory that extraterrestrial impacts had an important role in these events.
- Honami Sato
- , Tetsuji Onoue
- & Katsuhiko Suzuki
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| Open AccessTime-calibrated Milankovitch cycles for the late Permian
The astronomical time scale is an essential geochronological tool, but is presently limited to the Cenozoic and Mesozoic eras. Here, Wuet al.time-calibrate Milankovitch cycles identified in strata from South China and extend this essential tool into the late Permian.
- Huaichun Wu
- , Shihong Zhang
- & Tianshui Yang
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Constraining timescales of focused magmatic accretion and extension in the Afar crust using lava geochronology
In mature continental rifts, magma intrusion appears to accommodate significant crustal extension. Here, radiometric ages for lavas suggest that this style of focused magmatic accretion and rifting remained stable in the Ethiopian crust for at least ~200 kyr, prior to the onset of true oceanic spreading.
- David J. Ferguson
- , Andrew T. Calvert
- & Tim J. Wright
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| Open AccessHigh heat flow and ocean acidification at a nascent rift in the northern Gulf of California
Active seafloor spreading has been documented in some of the tectonically active basins of the Gulf of California. This work presents new geophysical and geochemical data as evidence that active seafloor spreading is also occurring in the northernmost Wagner and Consag basins of the Gulf.
- Rosa Ma Prol-Ledesma
- , Marco-Antonio Torres-Vera
- & Carlos Robinson
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A four-dimensional X-ray tomographic microscopy study of bubble growth in basaltic foam
Changes in bubble foam structure influence magma strength. Here, Bakeret al. measure bubble size and wall thickness of basaltic foams and find that basaltic magmas are most likely to fail immediately upon vesiculation, but a permeability increase within a few seconds may reduce the risk of explosive eruptions.
- Don R. Baker
- , Francesco Brun
- & Mark Rivers
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The origin of pelletal lapilli in explosive kimberlite eruptions
Kimberlites are volatile-rich magmas that form diverging pipes containing pelletal lapilli - well rounded clasts that consist of an inner seed particle. Gernonet al. suggest that pelletal lapilli are formed when fluid volatile-rich melts intrude into earlier volcaniclastic infill close to the diatreme root zone.
- T.M. Gernon
- , R.J. Brown
- & T.K. Hincks
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Stress-induced chemical waves in sediment burial diagenesis
Dolomite sedimentary rock has lateral metre-scale periodic variations in porosity and composition, which may provide information on formation and transformation. This study suggests that such variations are fossilized chemical waves emerging from stress-mediated mineral-water interaction during sediment burial diagenesis.
- Yifeng Wang
- & David A. Budd
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Melt migration in basalt columns driven by crystallization-induced pressure gradients
The internal textures of columnar-jointed lava flows and intrusions are poorly understood. Mattssonet al. propose a melt-migration model for Icelandic basalt driven by crystallization and volume decrease inside cooling columns, which explains the macroscopic features observed in columnar-jointed basalts.
- Hannes B. Mattsson
- , Luca Caricchi
- & Ann M. Hirt
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Prevailing oxic environments in the Pacific Ocean during the mid-Cretaceous Oceanic Anoxic Event 2
The second oceanic anoxic event occurred 94 million years ago and constituted a very large perturbation of the Earth's carbon cycle. Here, the authors study carbon isotopes and degrees of pyritization and demonstrate that, unlike other oceans, the Pacific remained oxygenated for most of this period.
- Reishi Takashima
- , Hiroshi Nishi
- & Keiichi Hayashi
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Historical land use change has lowered terrestrial silica mobilization
Continental export of silicon to the coast is linked to ocean carbon sinks, but terrestrial silicon fluxes have not been quantified. Here, human deforestation and cultivation of the landscape are shown to be the most important factors in silicon mobilization in temperate European watersheds.
- Eric Struyf
- , Adriaan Smis
- & Patrick Meire
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| Open AccessDiscovery of a black smoker vent field and vent fauna at the Arctic Mid-Ocean Ridge
The Arctic Mid-Ocean Ridge spreads extremely slowly and hydrothermal vent fields have not been reported in its vicinity. Pedersenet al. describe a black smoker vent field with large hydrothermal deposits and novel fauna distinct from those found in similar environments in the Atlantic.
- Rolf B. Pedersen
- , Hans Tore Rapp
- & Steffen L. Jorgensen
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Evidence for infragravity wave-tide resonance in deep oceans
Ocean tides and infragravity waves—the Earths 'hum'—have very different periods and wavelengths. Sugioka and colleagues report resonance between these two phenomena using arrays of broadband ocean-bottom seismometers and show that some tidal energy is transferred to the deep oceans through this coupling.
- Hiroko Sugioka
- , Yoshio Fukao
- & Toshihiko Kanazawa
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Crustaceans from bitumen clast in Carboniferous glacial diamictite extend fossil record of copepods
Copepod crustaceans are extremely abundant but fossilize poorly given their fragility; the earliest known fossils are from the Cretaceous period. Selden and colleagues report copepod fossils dating from the Carboniferous in a bitumen clast in Oman, extending their fossil record by 188 million years.
- Paul A. Selden
- , Rony Huys
- & Paul N. Taylor
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A new Argentinean nesting site showing neosauropod dinosaur reproduction in a Cretaceous hydrothermal environment
Dinosaur nesting sites have been found in many different places, but the factors that influenced the choice of location are unclear. Here, a sauropod nesting site is described in a geothermal setting in the Sanagasta Valley, suggesting that the dinosaurs used the warm environment to favour the incubation process.
- Gerald Grellet-Tinner
- & Lucas E. Fiorelli