bluuebunny/crossref_metadata_2025_split huggingface dataset:
Post Mid‐Cretaceous Tectonic and Topographic Evolution of Western Marie Byrd Land, WestAntarctica: Insights from Apatite FissionTrack and (U‐Th‐Sm)/He Data
Authors: Zundel Maximilian , Spiegel Cornelia , Lisker Frank , Monien Patrick 
Published: October 2019

AbstractNew low‐temperature thermochronological data from granitic basement of western Marie Byrd Land (MBL) provide insights into the still poorly constrained tectonic and topographic evolution of West Antarctica during and after continental breakup. Here, we present the first apatite (U‐Th‐Sm)/He data from the Devonian Ford Granodiorite and the mid‐Cretaceous Byrd Coast Granite suites from the Ford Ranges and the Edward VII Peninsula. Thermal history modeling integrating apatite (U‐Th‐Sm)/He dates of 109–68 Ma with revised apatite fission track data in combination with geologic information indicates a thermal history with diachronous enhanced cooling at ~100–60 Ma and subsequent slow cooling until the present day. Enhanced cooling at ~100–70 Ma was related to activity of the West Antarctic rift system and to continental breakup, thereby exhuming most samples to shallow crustal levels. Localized cooling at ~75–60 Ma is interpreted as resulting from faulting in the eastern Ross Sea region. Slow cooling after ~70–60 Ma corresponds with formation of erosion surfaces in western MBL. Comparison of our results from western MBL with data from the literature indicates progressive formation of erosion surfaces from west to east along the MBL‐Thurston Island crustal blocks. Late Cenozoic activity of the West Antarctic rift system and MBL dome uplift appear to have caused only minor exhumation of <1.5 km in western MBL.
The Cold Ion Population at Geosynchronous Orbit and Transport to the Dayside Magnetopause: September 2015 to February 2016
Authors: Denton M. H. , Henderson M. G. , Maruyama N. , Fuselier S. A. 
Published: October 2019

AbstractDuring intervals of enhanced magnetospheric convection, a high‐density plume of cold ions is eroded from the plasmasphere and can flow toward the dayside magnetopause where it has the potential to reduce the rate of magnetic reconnection. In any interval of long‐duration enhanced convection, tons of ions may follow such a trajectory. The study here concerns cold ion observations from geosynchronous orbit (GEO) during both calm and active periods. Probability distributions of the cold ion density and cold ion flow speed are determined during the 6‐month period from September 2015 to February 2016, inclusive. During low geomagnetic activity, the cold, dense ions are in corotation with the Earth, and flow speeds rarely exceed 10 km/s. During elevated geomagnetic activity, the cold ions between 12 and 18 magnetic local time are observed to flow toward the dayside magnetosphere with a speed of >10 km/s approximately 50% of the time. The Shue et al. (1998, https://doi.org/10.1029/98JA01103) model of the magnetopause location is used to derive the distribution of approximate minimum times for the cold ions to be transported from GEO to the dayside magnetopause. On average, during enhanced convection periods (Kp > 3) ions will take a mean time of ~4.5 hr to travel from GEO to the dayside magnetopause.
Mapping Deep Electrical Conductivity Structure in the Mount Isa region, Northern Australia: Implications for Mineral Prospectivity
Authors: Jiang Wenping , Korsch Russell J. , Doublier Michael P. , Duan Jingming , Costelloe Ross 
Published: October 2019

AbstractThe Mount Isa Province in northern Australia is one of the world's most strongly endowed regions for base metals and host to major iron–oxide–copper–gold (IOCG) deposits. The Carpentaria conductivity anomaly at the eastern margin of the province is a major electrical conductivity structure of the Australian continent. We use magnetotelluric data to image the crustal architecture in this highly mineralized region. The resistivity models reveal a number of prominent crustal‐scale conductors, suggesting that the Carpentaria conductivity anomaly is likely caused by a series of isolated or interconnected bodies. These conductors confirm the position and geometry of the ancient Gidyea Suture zone, the eastern boundary of the Mount Isa Province, interpreted as a west‐dipping subduction zone. The Carpentaria conductivity anomaly may record the activity of fluid dehydration involved during a subduction event, with the enhanced conductivity likely being caused by deformation or mineralization of graphitic or sulfidic rocks during orogenesis. The major iron oxide in the Ernest Henry IOCG deposit located in the hanging wall of the Gidyea Suture zone is magnetite, suggesting another possible conductive source. The distribution of known gold and copper deposits shows a close spatial correlation with the suture zone, suggesting that this structure is potentially a fundamental control on IOCG deposits in its vicinity. The implication is that crustal‐penetrating structures act as potential pathways for fluid movement to form mineral deposits in the upper crust. The significance of mapping such structures using geophysics is highlighted for mineral exploration.
Hf and Nd Isotopic Constraints on Pre‐ and Syn‐collisional Crustal Thickness of Southern Tibet
Authors: Alexander E. W. , Wielicki M. M. , Harrison T. M. , DePaolo D. J. , Zhao Z. D. , Zhu D. C. 
Published: October 2019

AbstractIn Southern Tibet, voluminous granitoids emplaced between 225‐20 Ma provide a spatiotemporal window into the geochemical and tectonic evolution of the crust. Hf and O isotope geochemistry of whole rocks and constituent zircons together with whole‐rock chemistry reveal a coherent magmatic history of Gangdese granitoids, and by extension, crustal thickening history of S. Tibet. We observe a spatial isotopic gradient with N‐S distance from the Indus‐Tsangpo Suture (ITS), with younger, more εHf‐positive granitoids adjacent the ITS. Zircons range from εHf = ‐13 to +11 in a broadly systematic fashion from north to south, generally independent of 206Pb/238U age. Adjacent to the ITS, syncollisional (<50 Ma) rocks have generally more heterogeneous εHf than precollisional (>70 Ma) and early syncollisional (50‐70 Ma) granitoids, likely reflecting increased assimilation of crustal material in syncollisional magmas as the crust thickened. Zircon δ18O ranges between +4 and +8‰; syncollisional samples have exclusively mantle‐like values (+5.5 to +6‰), with greater heterogeneity in precollisional samples. Zircon and whole‐rock εHf data reported here are consistent with previous Nd‐based thermoisotopic models indicating that the Lhasa block maintained a wedge‐shaped crustal geometry from the early Jurassic until the onset of collision. Given evidence of minimal post‐50 Ma upper‐crustal shortening, these results support earlier findings that the Tibetan crust reached its present ~75 km thickness via a roughly equal mixture of upper plate accretion and juvenile magmatic inflation on top of the ~30 km‐thick of Indian crust underthrust beneath the Lhasa block.
Seismic Structure of the Antarctic Upper Mantle Imaged with Adjoint Tomography
Authors: Lloyd A. J. , Wiens D. A. , Zhu H. , Tromp J. , Nyblade A. A. , Aster R. C. , Hansen S. E. , Dalziel I. W. D. , Wilson T.J. , Ivins E. R. , O’Donnell J. P. 
Published: October 2019

AbstractThe upper mantle and transition zone beneath Antarctica and the surrounding oceans are among the poorest‐imaged regions of the Earth's interior. Over the last 15 years, several large broadband regional seismic arrays have been deployed, as have new permanent seismic stations. Using data from 297 Antarctic and 26 additional seismic stations south of ~40°S, we image the seismic structure of the upper mantle and transition zone using adjoint tomography. Over the course of 20 iterations, we utilize phase observations from three‐component seismograms containing P, S, Rayleigh, and Love waves, including reflections and overtones, generated by 270 earthquakes that occurred from 2001–2003 and 2007–2016. The new continental‐scale seismic model (ANT‐20) possesses regional‐scale resolution south of 60°S. In East Antarctica, thinner continental lithosphere is found beneath areas of Dronning Maud Land and Enderby‐Kemp Land. A continuous slow wave speed anomaly extends from the Balleny Islands through the western Ross Embayment and delineates areas of Cenozoic extension and volcanism that span both oceanic and continental regions. Slow wave speed anomalies are also imaged beneath Marie Byrd Land and along the Amundsen Sea Coast, extending to the Antarctic Peninsula. These anomalies are confined to the upper 200–250 km of the mantle, except in the vicinity of Marie Byrd Land where they extend into the transition zone and possibly deeper. Finally, slow wave speeds along the Amundsen Sea Coast link to deeper anomalies offshore, suggesting a possible connection with deeper mantle processes.
Confirmation of a Late Miocene Subchron C4n.2n‐1r From the Eastern Qaidam Basin in the NE Tibetan Plateau
Authors: Gao Peng , Nie Junsheng , Li Mingsong , Li Pu 
Published: October 2019

AbstractRefining reversal ages and improving reversal patterns for the geomagnetic polarity timescale are a major task for the paleomagnetic community. The Late Miocene is a period during which the geomagnetic field experienced frequent perturbations and which dramatic environmental changes occurred. Thus, improved (sub)chron definition during this period will enable to provide additional age control points for better understanding age of paleoenvironmental changes. A prior study of the Late Miocene C4n.2n magnetic polarity zone at Ocean Drilling Program Site 1092 in the sub‐Antarctic South Atlantic Ocean has revealed the potential existence of a subchron (C4n.2n‐1r). However, this subchron has not been incorporated into the geomagnetic polarity timescale yet because its existence has not been confirmed. Moreover, the low sediment accumulation rate of 1.32 cm/kyr at Site 1092 hampers a confident estimation of the age and duration of this subchron. Here we present a high‐resolution paleomagnetic data set covering C4n.2n from the Huaitoutala section in the eastern Qaidam Basin, Northwest China, with an average sediment accumulation rate of ~22 cm/kyr. Nine reversed declination/inclination data points define a subchron near the top of C4n.2n, similar to age of reported C4n.2n‐1r at Ocean Drilling Program Site 1092. Cyclostratigraphy of the magnetic susceptibility record of the Huaitoutala section suggests that the age and duration of the C4n.2n‐1r are 7.7612–7.7554 Ma and 5.8 ± 2.1 kyr, respectively. Confirming the existence of C4n.2n‐1r from a northern hemisphere terrestrial site suggests that two geomagnetic reversals bounding this subchron have global imprints and that this subchron can potentially serve as marker for stratigraphic correlation.
Fault Reactivation During Fluid Pressure Oscillations: Transition From Stable to Unstable Slip
Authors: Noël Corentin , Passelègue François X. , Giorgetti Carolina , Violay Marie 
Published: October 2019

AbstractHigh‐pressure fluid injection in deep georeservoirs can induce earthquakes. Recent observations suggest that cyclic injections might trigger less seismicity than monotonic injections. Here, we report triaxial laboratory experiments conducted on faulted quartz‐rich sandstone that provide new insight into the physics of fault‐fluid interactions subjected to cyclic fluid pressure variations. The experiments were performed at 30 and 45 MPa confining pressure, imposing constant or sinusoidal fluid pressure oscillations of amplitudes ranging from 0 to 8 MPa in addition to a far‐field constant loading rate (10−4 and 10−3 mm s−1). The results show that (i) in agreement with the Mohr‐Coulomb theory, faults reactivate at the static friction criterion, which is generally reached at the maximum fluid pressure during oscillations. (ii) Oscillating fluid pressure perturbations promote seismic behavior rather than aseismic slip, and (iii) increasing the oscillation's amplitude enhances the onset of seismic activity along the fault. We demonstrate that this behavior is caused by slip rate variations resulting from the fluid pressure oscillations. Without fluid pressure oscillations, increasing the far‐field loading rate also promotes seismic activity. Our experiments demonstrate that the seismicity intensification due to cyclic fluid injections could be promoted at shallow depth, where confining pressure is relatively low, resulting in large strain rate perturbations.
The Variability of Winds and Fluxes Observed Near Submesoscale Fronts
Authors: Shao Mingming , Ortiz‐Suslow David G. , Haus Brian K. , Lund Björn , Williams Neil J. , Özgökmen Tamay M. , Laxague Nathan J. M. , Horstmann Jochen , Klymak Jody M. 
Published: October 2019

AbstractSubmesoscale oceanic fronts (SFs), which typically occur on a spatial scale of 0.1–10 km, may have a large influence on the atmospheric surface layer (ASL). However, due to their short temporal‐spatial scales, evaluating their direct impact on this layer remains challenging and characterizing the nature of SF‐ASL interaction has not been done in the field. To address this, a study of the air‐sea response to SFs was conducted using observations collected during the Lagrangian Submesoscale Experiment, which took place in the northern Gulf of Mexico. This manuscript focuses on the meteorological measurements made from a pair of masts installed on the bow of the R/V Walton Smith. This work represents one of the first observation‐based investigations into the potential influence that SFs have on the ASL. Contemporaneous measurements from an X‐band marine radar, moving vessel profiler, and Lagrangian drifters were also used to analyze the SF dynamics. Systematic surface wind velocity changes over several cross‐frontal transects were observed, a process previously associated with mesoscale fronts. A comparison between the eddy covariance and parameterized (COARE 3.5) air‐sea fluxes revealed that the directly observed heat flux was 1.5 times larger than the bulk value in the vicinity of the SFs. This suggests that the hydrodynamic processes near the front enhance the local exchange of sensible and latent heat. Given the prevalence of SF over the global upper ocean, these findings suggest that these features may have a widely distributed and cumulative impact on air‐sea interactions.
Suppressed CO2 Outgassing by an Enhanced Biological Pump in the Eastern Tropical Pacific
Authors: Kim Hyung Jeek , Kim Tae‐Wook , Hyeong Kiseong , Yeh Sang‐Wook , Park Jong‐Yeon , Yoo Chan Min , Hwang Jeomshik 
Published: October 2019

AbstractThe Eastern Tropical Pacific (ETP) is the largest oceanic source of carbon dioxide (CO2) to the atmosphere. Sinking particle fluxes at a depth of 4,950 m (50 m above the seafloor) in the ETP were monitored from 2003 to 2013, during which the Pacific decadal oscillation (PDO) shifted from a positive to negative phase. We show a disproportionate increase in the efficiency of the biological pump in this region relative to the increase in primary production that occurred during La Niña years following the shift of the PDO in 2008. Biogenic carbon export from the surface mixed layer was estimated from the observed particulate organic carbon and inorganic carbon fluxes at a depth of 4,950 m and from empirical equations of the vertical attenuation of carbon flux. Enhanced biological carbon export accounted for 2.3–5.5 mol C m–2 year–1 during the La Niña events. Despite a large uncertainty associated with these estimates, we propose that CO2 outgassing was largely suppressed by an enhanced biological pump during the La Niña events in the negative PDO phase.
Flood Inundation Generation Mechanisms and Their Changes in 1953–2004 in Global Major River Basins
Authors: Mao Yuna , Zhou Tian , Leung L. Ruby , Tesfa Teklu K. , Li Hong‐Yi , Wang Kaicun , Tan Zeli , Getirana Augusto 
Published: October 2019

AbstractDespite the serious threats posed by floods, the driving mechanisms of floods are still not well understood. Here we apply a physically based inundation model coupled with a river routing model (Model for Scale Adaptive River Transport (MOSART)) within the Energy Exascale Earth System Model (E3SM) framework to investigate flood inundation dynamics. After calibration using observed streamflow and satellite‐derived flood extent, the model is used to simulate global flood inundation from 1953 to 2004. The mean date and seasonality of annual maximum flood, defined based on flood extent, exhibit significant regional differences across 16 major basins. Generally, soil moisture and monthly maximum daily rainfall (MMR) are the dominant drivers of flood in tropical basins while monthly maximum daily snowmelt (MMS) is the dominant driver in high‐latitude basins. From 1953–1982 to 1975–2004, significant changes in flood generation mechanisms are found in some basins such as Amazon, Lena, Yenisey, and Kolyma. Analysis of the rainfall seasonality and water balance at grid scale reveals a stronger rainfall seasonality in the Amazon during the later period that increases the synchrony between extreme rainfall and wet soil. With high antecedent soil moisture coinciding with rainfall, MMR contributes more to flood in the later period. Fewer extreme rainfall events and increasing soil moisture reduced the contribution of MMR and increased the role of MMS in floods in the Lena and Yenisey basins, respectively. Lastly, increased soil moisture and frequency of large MMS reduced the contribution of the latter to floods in the Kolyma basin.
From Toppling to Sliding: Progressive Evolution of the Moosfluh Landslide, Switzerland
Authors: Glueer Franziska , Loew Simon , Manconi Andrea , Aaron Jordan 
Published: October 2019

AbstractThis paper presents a detailed analysis of a dramatic rock slope acceleration that occurred in fall 2016 at the Moosfluh Landslide, located at the glacier tongue of the Great Aletsch Glacier (Switzerland). The acceleration that occurred in 2016 was unanticipated and exposed the valley bottom and an adjacent damned lake to high risk. This acceleration occurred in an active deep‐seated gravitational slope deformation (DSGSD) controlled primarily by deep block‐flexural toppling. In 2013, a highly accurate displacement monitoring system was developed and installed in the surroundings of the Great Aletsch Glacier, including a time‐lapse camera, GNSS, and robotic total stations. This monitoring system provided unique data during the 2016 slope acceleration which are used in this study to assess failure mechanisms, landslide volumes, and subsurface displacement geometry. Based on a novel displacement vector analysis, we find that three retrogressive secondary rockslides developed during the first six weeks of the slope acceleration, with rupture surface depths of 30 to 40 m, and estimated volumes between 1 and 4 Mm3. These rockslides display complex deformation features, including head and lateral scarps, which developed during the slope acceleration. The kinematics of these secondary rockslides changed through time, from primarily toppling to combined toppling and sliding. Our results provide a uniquely detailed understanding of the spatial and temporal evolution of deformation features and movement kinematics that occur when several sectors of a slowly moving DSGSD transitions into rapid rockslides.
Galileo Ionospheric Correction Algorithm: An Optimization Study of NeQuick‐G
Authors: Aragon‐Angel A. , Zürn M. , Rovira‐Garcia A. 
Published: October 2019

AbstractAt present most low‐cost GNSS receivers operate one frequency in the L band. For them one of the largest error contributions is the delay of radio signals in the Ionosphere. NeQuick‐G is the official ionospheric correction algorithm (ICA), which has been adopted for Galileo, the European GNSS Programme. The NeQuick‐G implementation is complex when compared with other ICAs. It is also demanding in terms of computational resources. The Joint Research Centre completed a reference implementation of NeQuick‐G based on the official document “Ionospheric Correction Algorithm for Galileo Single Frequency Users” provided by the European Global Navigation Satellite Systems Agency. The rationale behind the JRC implementation of NeQuick‐G was the intent to write an independent source code from scratch, without using the pseudo‐codes from the reference document and solely relying on the physics descriptions. Using such implementation as baseline, this paper describes an optimization attempt of the official pseudo‐code from an algorithmic perspective. The objective was to reduce the computational load while not sacrificing the performance. The new proposed integration method is able to speed up calculations to 21% and 49% with respect the two official integration algorithms. The overall computational burden depends on the number of operations, which is eventually closely correlated to the number of calls of the ionospheric model. This underlines the quest to find an integration method reducing this number of calls. Moreover, based on the findings of this study, the authors strongly recommend revisiting the convergence control of the integration routines introduced in (European Commission, 2016, https://www.gsc‐europa.eu/sites/default/files/sites/all/files/Galileo_Ionospheric_Model.pdf).
Detrital Zircon Geochronology of Upper Cretaceous to Paleocene Sandstones From South‐Central Wyoming: Evidence for Middle Campanian Laramide Deformation
Authors: Lynds R. M. , Xie X. 
Published: October 2019

AbstractLaramide deformation during the Late Cretaceous through early Eocene interrupted the east‐flowing drainage systems from the Sevier hinterland and segmented the Western Interior Foreland Basin in much of western North America into a series of intermontane basins and Precambrian basement‐cored uplifts. In Wyoming, the timing of Laramide deformation and its impacts on drainage patterns during the overlap in the Sevier and Laramide orogenies remain under debate. New detrital zircon U‐Pb geochronologic data from 11 outcrop samples (n = 3,085) in south‐central Wyoming suggest at least two provenance‐distribution phases, distinguished by a substantial increase in zircons of late Paleoproterozoic age (1800–1600 Ma) recorded at approximately 79 Ma. The most likely source of late Paleoproterozoic age zircons is Precambrian basement‐cored uplifts, specifically the Sierra Madre Mountains, signaling the possible middle Campanian initiation of Laramide uplift, earlier than previously recorded. When combined with complementary data sets from surrounding basins, the first provenance‐distribution phase is age discordant, with the earliest evidence of 1800–1600 Ma zircons in the Piceance Basin of Colorado (late Santonian to early Campanian). The second provenance phase shows repeating age distribution patterns that begin with significant contributions from 1800 to 1600 Ma zircon grains and end with much broader and evenly distributed population signatures, confirming previous interpretations of significant Laramide deformation during the Maastrichtian (approximately 70 Ma) as well as uplift and recycling of Upper Cretaceous formations at about 67 Ma.