TY  - JOUR
A1  - Esfahani, Reza Dokht Dolatabadi
A1  - Gholami, Ali
A1  - Ohrnberger, Matthias
T1  - An inexact augmented Lagrangian method for nonlinear dispersion-curve inversion using Dix-type global linear approximation
JF  - Geophysics : a journal of general and applied geophysics
N2  - Dispersion-curve inversion of Rayleigh waves to infer subsurface shear-wave velocity is a long-standing problem in seismology. Due to nonlinearity and ill-posedness, sophisticated regularization techniques are required to solve the problem for a stable velocity model. We have formulated the problem as a minimization problem with nonlinear operator constraint and then solve it by using an inexact augmented Lagrangian method, taking advantage of the Haney-Tsai Dix-type relation (a global linear approximation of the nonlinear forward operator). This replaces the original regularized nonlinear problem with iterative minimization of a more tractable regularized linear problem followed by a nonlinear update of the phase velocity (data) in which the update can be performed accurately with any forward modeling engine, for example, the finite-element method. The algorithm allows discretizing the medium with thin layers (for the finite-element method) and thus omitting the layer thicknesses from the unknowns and also allows incorporating arbitrary regularizations to shape the desired velocity model. In this research, we use total variation regularization to retrieve the shear-wave velocity model. We use two synthetic and two real data examples to illustrate the performance of the inversion algorithm with total variation regularization. We find that the method is fast and stable, and it converges to the solution of the original nonlinear problem.
KW  - surface wave
KW  - nonlinear
KW  - inversion
KW  - modeling
KW  - finite element
Y1  - 2020
U6  - https://doi.org/10.1190/geo2019-0717.1
SN  - 0016-8033
SN  - 1942-2156
VL  - 85
IS  - 3
SP  - EN77
EP  - EN85
PB  - GeoScienceWorld
CY  - Tulsa, Okla.
ER  - 
TY  - JOUR
A1  - Kumar, Rohini
A1  - Hesse, Fabienne
A1  - Rao, P. Srinivasa
A1  - Musolff, Andreas
A1  - Jawitz, James
A1  - Sarrazin, Francois
A1  - Samaniego, Luis
A1  - Fleckenstein, Jan H.
A1  - Rakovec, Oldrich
A1  - Thober, S.
A1  - Attinger, Sabine
T1  - Strong hydroclimatic controls on vulnerability to subsurface nitrate contamination across Europe
JF  - Nature Communications
N2  - Subsurface contamination due to excessive nutrient surpluses is a persistent and widespread problem in agricultural areas across Europe. The vulnerability of a particular location to pollution from reactive solutes, such as nitrate, is determined by the interplay between hydrologic transport and biogeochemical transformations. Current studies on the controls of subsurface vulnerability do not consider the transient behaviour of transport dynamics in the root zone. Here, using state-of-the-art hydrologic simulations driven by observed hydroclimatic forcing, we demonstrate the strong spatiotemporal heterogeneity of hydrologic transport dynamics and reveal that these dynamics are primarily controlled by the hydroclimatic gradient of the aridity index across Europe. Contrasting the space-time dynamics of transport times with reactive timescales of denitrification in soil indicate that similar to 75% of the cultivated areas across Europe are potentially vulnerable to nitrate leaching for at least onethird of the year. We find that neglecting the transient nature of transport and reaction timescale results in a great underestimation of the extent of vulnerable regions by almost 50%. Therefore, future vulnerability and risk assessment studies must account for the transient behaviour of transport and biogeochemical transformation processes.
KW  - travel time distributions
KW  - groundwater vulnerability
KW  - flux tracking
KW  - transit-time
KW  - water age
KW  - nitrogen
KW  - model
KW  - dynamics
KW  - pollution
KW  - patterns
Y1  - 2020
U6  - https://doi.org/10.1038/s41467-020-19955-8
SN  - 2041-1723
VL  - 11
IS  - 1
SP  - 1
EP  - 10
PB  - Nature Publishing Group UK
CY  - London
ER  - 
TY  - JOUR
A1  - Palmer, Matthew D.
A1  - Gregory, Jonathan
A1  - Bagge, Meike
A1  - Calvert, Daley
A1  - Hagedoorn, Jan Marius
A1  - Howard, Tom
A1  - Klemann, Volker
A1  - Lowe, Jason A.
A1  - Roberts, Chris
A1  - Slangen, Aimee B. A.
A1  - Spada, Giorgio
T1  - Exploring the drivers of global and local sea‐level change over the 21st century and beyond
JF  - Earth's future
N2  - We present a new set of global and local sea‐level projections at example tide gauge locations under the RCP2.6, RCP4.5, and RCP8.5 emissions scenarios. Compared to the CMIP5‐based sea‐level projections presented in IPCC AR5, we introduce a number of methodological innovations, including (i) more comprehensive treatment of uncertainties, (ii) direct traceability between global and local projections, and (iii) exploratory extended projections to 2300 based on emulation of individual CMIP5 models. Combining the projections with observed tide gauge records, we explore the contribution to total variance that arises from sea‐level variability, different emissions scenarios, and model uncertainty. For the period out to 2300 we further breakdown the model uncertainty by sea‐level component and consider the dependence on geographic location, time horizon, and emissions scenario. Our analysis highlights the importance of local variability for sea‐level change in the coming decades and the potential value of annual‐to‐decadal predictions of local sea‐level change. Projections to 2300 show a substantial degree of committed sea‐level rise under all emissions scenarios considered and highlight the reduced future risk associated with RCP2.6 and RCP4.5 compared to RCP8.5. Tide gauge locations can show large ( > 50%) departures from the global average, in some cases even reversing the sign of the change. While uncertainty in projections of the future Antarctic ice dynamic response tends to dominate post‐2100, we see substantial differences in the breakdown of model variance as a function of location, time scale, and emissions scenario.
KW  - climate change
KW  - CMIP5 models
KW  - RCP scenarios
KW  - sea-level projections
KW  - tide gauge observations
Y1  - 2020
U6  - https://doi.org/10.1029/2019EF001413
SN  - 2328-4277
VL  - 8
IS  - 9
SP  - 1
EP  - 25
PB  - Wiley-Blackwell
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Jones, Benjamin M.
A1  - Arp, Christopher D.
A1  - Grosse, Guido
A1  - Nitze, Ingmar
A1  - Lara, Mark J.
A1  - Whitman, Matthew S.
A1  - Farquharson, Louise M.
A1  - Kanevskiy, Mikhail
A1  - Parsekian, Andrew D.
A1  - Breen, Amy L.
A1  - Ohara, Nori
A1  - Rangel, Rodrigo Correa
A1  - Hinkel, Kenneth M.
T1  - Identifying historical and future potential lake drainage events on the western Arctic coastal plain of Alaska
JF  - Permafrost and Periglacial Processes
N2  - Arctic lakes located in permafrost regions are susceptible to catastrophic drainage. In this study, we reconstructed historical lake drainage events on the western Arctic Coastal Plain of Alaska between 1955 and 2017 using USGS topographic maps, historical aerial photography (1955), and Landsat Imagery (ca. 1975, ca. 2000, and annually since 2000). We identified 98 lakes larger than 10 ha that partially (>25% of area) or completely drained during the 62-year period. Decadal-scale lake drainage rates progressively declined from 2.0 lakes/yr (1955-1975), to 1.6 lakes/yr (1975-2000), and to 1.2 lakes/yr (2000-2017) in the ~30,000-km(2) study area. Detailed Landsat trend analysis between 2000 and 2017 identified two years, 2004 and 2006, with a cluster (five or more) of lake drainages probably associated with bank overtopping or headward erosion. To identify future potential lake drainages, we combined the historical lake drainage observations with a geospatial dataset describing lake elevation, hydrologic connectivity, and adjacent lake margin topographic gradients developed with a 5-m-resolution digital surface model. We identified ~1900 lakes likely to be prone to drainage in the future. Of the 20 lakes that drained in the most recent study period, 85% were identified in this future lake drainage potential dataset. Our assessment of historical lake drainage magnitude, mechanisms and pathways, and identification of potential future lake drainages provides insights into how arctic lowland landscapes may change and evolve in the coming decades to centuries.
KW  - Arctic lakes
KW  - drained lake basins
KW  - lake drainage
KW  - permafrost regions
KW  - thermokarst lakes
Y1  - 2020
U6  - https://doi.org/10.1002/ppp.2038
VL  - 31
IS  - 1
SP  - 110
EP  - 127
PB  - Wiley
CY  - New York
ER  - 
TY  - JOUR
A1  - Foster, William J.
A1  - Garvie, Christopher L.
A1  - Weiss, Anna M.
A1  - Muscente, A. Drew
A1  - Aberhan, Martin
A1  - Counts, John W.
A1  - Martindale, Rowan C.
T1  - Resilience of marine invertebrate communities during the early Cenozoic hyperthermals
JF  - Scientific Reports
N2  - The hyperthermal events of the Cenozoic, including the Paleocene-Eocene Thermal Maximum, provide an opportunity to investigate the potential effects of climate warming on marine ecosystems. Here, we examine the shallow benthic marine communities preserved in the late Cretaceous to Eocene strata on the Gulf Coastal Plain (United States). In stark contrast to the ecological shifts following the end-Cretaceous mass extinction, our data show that the early Cenozoic hyperthermals did not have a long-term impact on the generic diversity nor composition of the Gulf Coastal Plain molluscan communities. We propose that these communities were resilient to climate change because molluscs are better adapted to high temperatures than other taxa, as demonstrated by their physiology and evolutionary history. In terms of resilience, these communities differ from other shallow-water carbonate ecosystems, such as reef communities, which record significant changes during the early Cenozoic hyperthermals. These data highlight the strikingly different responses of community types, i.e., the almost imperceptible response of molluscs versus the marked turnover of foraminifera and reef faunas. The impact on molluscan communities may have been low because detrimental conditions did not devastate the entire Gulf Coastal Plain, allowing molluscs to rapidly recolonise vacated areas once harsh environmental conditions ameliorated.
KW  - eocene thermal maximum
KW  - gulf coastal plain
KW  - climate-change
KW  - ocean acidification
KW  - extinction event
KW  - carbon-cycle
KW  - heat-stress
KW  - origination
KW  - ecosystems
KW  - diversity
Y1  - 2020
U6  - https://doi.org/10.1038/s41598-020-58986-5
SN  - 2045-2322
VL  - 10
IS  - 1
SP  - 1
EP  - 11
PB  - Springer Nature
CY  - London
ER  - 
TY  - JOUR
A1  - Tardif-Becquet, Delphine
A1  - Fluteau, Frédéric
A1  - Donnadieu, Yannick
A1  - Le Hir, Guillaume
A1  - Ladant, Jean-Baptiste
A1  - Sepulchre, Pierre
A1  - Licht, Alexis
A1  - Poblete, Fernando
A1  - Dupont-Nivet, Guillaume
T1  - The origin of Asian monsoons
BT  - a modelling perspective
JF  - Climate of the Past
N2  - The Cenozoic inception and development of the Asian monsoons remain unclear and have generated much debate, as several hypotheses regarding circulation patterns at work in Asia during the Eocene have been proposed in the few last decades. These include (a) the existence of modern-like monsoons since the early Eocene; (b) that of a weak South Asian monsoon (SAM) and little to no East Asian monsoon (EAM); or (c) a prevalence of the Intertropical Convergence Zone (ITCZ) migrations, also referred to as Indonesian-Australian monsoon (I-AM). As SAM and EAM are supposed to have been triggered or enhanced primarily by Asian palaeogeographic changes, their possible inception in the very dynamic Eocene palaeogeographic context remains an open question, both in the modelling and field-based communities. We investigate here Eocene Asian climate conditions using the IPSL-CM5A2 (Sepulchre et al., 2019) earth system model and revised palaeogeographies. Our Eocene climate simulation yields atmospheric circulation patterns in Asia substantially different from modern conditions. A large high-pressure area is simulated over the Tethys ocean, which generates intense low tropospheric winds blowing southward along the western flank of the proto-Himalayan-Tibetan plateau (HTP) system. This low-level wind system blocks, to latitudes lower than 10 degrees N, the migration of humid and warm air masses coming from the Indian Ocean. This strongly contrasts with the modern SAM, during which equatorial air masses reach a latitude of 20-25 degrees N over India and southeastern China. Another specific feature of our Eocene simulation is the widespread subsidence taking place over northern India in the midtroposphere (around 5000 m), preventing deep convective updraught that would transport water vapour up to the condensation level. Both processes lead to the onset of a broad arid region located over northern India and over the HTP. More humid regions of high seasonality in precipitation encircle this arid area, due to the prevalence of the Intertropical Convergence Zone (ITCZ) migrations (or Indonesian-Australian monsoon, I-AM) rather than monsoons. Although the existence of this central arid region may partly result from the specifics of our simulation (model dependence and palaeogeographic uncertainties) and has yet to be confirmed by proxy records, most of the observational evidence for Eocene monsoons are located in the highly seasonal transition zone between the arid area and the more humid surroundings. We thus suggest that a zonal arid climate prevailed over Asia before the initiation of monsoons that most likely occurred following Eocene palaeogeographic changes. Our results also show that precipitation seasonality should be used with caution to infer the presence of a monsoonal circulation and that the collection of new data in this arid area is of paramount importance to allow the debate to move forward.
KW  - earth system model
KW  - early eocene
KW  - tibetan plateau
KW  - climate-change
KW  - oligocene climate
KW  - summer monsoon
KW  - global monsoon
KW  - ice sheet
KW  - part 1
KW  - China
Y1  - 2020
U6  - https://doi.org/10.5194/cp-16-847-2020
SN  - 1814-9332
SN  - 1814-9324
VL  - 16
IS  - 3
SP  - 847
EP  - 865
PB  - Copernicus Publications
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Schuck, Bernhard
A1  - Schleicher, Anja Maria
A1  - Janssen, Christoph
A1  - Toy, Virginia G.
A1  - Dresen, Georg
T1  - Fault zone architecture of a large plate-bounding strike-slip fault
BT  - A case study from the Alpine Fault, New Zealand
JF  - Solid Earth
N2  - New Zealand's Alpine Fault is a large, platebounding strike-slip fault, which ruptures in large (M-w > 8) earthquakes. We conducted field and laboratory analyses of fault rocks to assess its fault zone architecture. Results reveal that the Alpine Fault Zone has a complex geometry, comprising an anastomosing network of multiple slip planes that have accommodated different amounts of displacement. This contrasts with the previous perception of the Alpine Fault Zone, which assumes a single principal slip zone accommodated all displacement. This interpretation is supported by results of drilling projects and geophysical investigations. Furthermore, observations presented here show that the young, largely unconsolidated sediments that constitute the footwall at shallow depths have a significant influence on fault gouge rheological properties and structure.
KW  - san andreas fault
KW  - thickness-displacement relationships
KW  - central south island
KW  - Ion-Beam (FIB)
KW  - internal structure
KW  - hanging wall
KW  - Fluid Flow
KW  - frictional properties
KW  - weakening mechanisms
KW  - strain localization
Y1  - 2020
U6  - https://doi.org/10.5194/se-11-95-2020
SN  - 1869-9529
VL  - 11
IS  - 1
SP  - 95
EP  - 124
PB  - Copernicus Publications
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Olen, Stephanie M.
A1  - Bookhagen, Bodo
A1  - Strecker, Manfred
T1  - Corrigendum to:  Olen, Stephanie M.; Bookhagen, Bodo; Strecker, Manfred R. : Role of climate and vegetation density in modulating denudation rates in the Himalaya. - Earth and planetary science letters. - 445 (2016), S. 57 - 67. - doi: https://doi.org/10.1016/j.epsl.2016.03.047
JF  - Earth and planetary science letters
N2  - Vegetation has long been hypothesized to influence the nature and rates of surface processes. We test the possible impact of vegetation and climate on denudation rates at orogen scale by taking advantage of a pronounced along-strike gradient in rainfall and vegetation density in the Himalaya. We combine 12 new 10Be denudation rates from the Sutlej Valley and 123 published denudation rates from fluvially- dominated catchments in the Himalaya with remotely-sensed measures of vegetation density and rainfall metrics, and with tectonic and lithologic constraints. In addition, we perform topographic analyses to assess the contribution of vegetation and climate in modulating denudation rates along strike. We observe variations in denudation rates and the relationship between denudation and topography along strike that are most strongly controlled by local rainfall amount and vegetation density, and cannot be explained by along-strike differences in tectonics or lithology. A W–E along-strike decrease in denudation rate variability positively correlates with the seasonality of vegetation density (R = 0.95, p < 0.05), and negatively correlates with mean vegetation density (R = −0.84, p < 0.05). Vegetation density modulates the topographic response to changing denudation rates, such that the functional relationship between denudation rate and topographic steepness becomes increasingly linear as vegetation density increases. We suggest that while tectonic processes locally control the pattern of denudation rates across strike of the Himalaya (i.e., S–N), along strike of the orogen (i.e., E–W) climate exerts a measurable influence on how denudation rates scatter around long-term, tectonically-controlled erosion, and on the functional relationship between topography and denudation
Y1  - 2020
U6  - https://doi.org/10.1016/j.epsl.2020.116252
SN  - 0012-821X
SN  - 1385-013X
VL  - 540
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Krüger, Frank
A1  - Dahm, Torsten
A1  - Hannemann, Katrin
T1  - Mapping of Eastern North Atlantic Ocean seismicity from Po/So observations at a mid-aperture seismological broad-band deep sea array
JF  - Geophysical journal international
N2  - A mid-aperture broad-band test array (OBS array DOCTAR) was deployed from June 2011 to April 2012 about 100 km north of the Gloria fault in the Eastern North Atlantic in about 5000 m water depth. In addition arrays were installed on Madeira Island and in western Portugal mainland. For the first time in the Eastern North Atlantic, we recorded a large number of high frequency Po and So waves from local and regional small and moderate earthquakes (M-L < 4). An incoherent beamforming method was adapted to scan continuous data for such Po and So arrivals applying a sliding window waveform migration and frequency-wavenumber technique. We identify about 320 Po and 1550 So arrivals and compare the phase onsets with the ISC catalogue (ISC 2015) for the same time span. Up to a distance of 6 degrees to the DOCTAR stations all events listed in the ISC catalogue could be associated to Po and So phases. Arrivals from events in more than 10 degrees distance could be identified only in some cases. Only few Po and/or So arrivals were detected for earthquakes from the European and African continental area, the continental shelf regions and for earthquakes within or northwest of the Azores plateau. Unexpectedly, earthquake clusters are detected within the oceanic plates north and south of the Gloria fault and far from plate boundaries, indicating active intraplate structures. We also observe and locate numerous small magnitude earthquakes on the segment of the Gloria fault directly south of DOCTAR, which likely coincides with the rupture of the 25 November 1941 event. Local small magnitude earthquakes located beneath DOCTAR show hypocentres up to 30 km depth and strike-slip focal mechanisms. A comparison with detections at temporary mid-aperture arrays on Madeira and in western Portugal shows that the deep ocean array performs much better than the island and the continental array regarding the detection threshold for events in the oceanic plates. 
 We conclude that sparsely distributed mid-aperture seismic arrays in the deep ocean could decrease the detection and location threshold for seismicity with M-L < 4 in the oceanic plate and might constitute a valuable tool to monitor oceanic plate seismicity.
KW  - body waves
KW  - earthquake source observations
KW  - seismicity and tectonics
Y1  - 2020
U6  - https://doi.org/10.1093/gji/ggaa054
SN  - 0956-540X
SN  - 1365-246X
VL  - 221
IS  - 2
SP  - 1055
EP  - 1080
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Grotheer, Hendrik
A1  - Meyer, Vera
A1  - Riedel, Theran
A1  - Pfalz, Gregor
A1  - Mathieu, Lucie
A1  - Hefter, Jens H.
A1  - Gentz, Torben
A1  - Lantuit, Hugues
A1  - Mollennauer, Gesine
A1  - Fritz, Michael
T1  - Burial and origin of permafrost-derived carbon in the nearshore zone of the southern Canadian Beaufort Sea
JF  - Geophysical research letters
N2  - Detailed organic geochemical and carbon isotopic (delta C-13 and Delta C-14) analyses are performed on permafrost deposits affected by coastal erosion (Herschel Island, Canadian Beaufort Sea) and adjacent marine sediments (Herschel Basin) to understand the fate of organic carbon in Arctic nearshore environments. We use an end-member model based on the carbon isotopic composition of bulk organic matter to identify sources of organic carbon. Monte Carlo simulations are applied to quantify the contribution of coastal permafrost erosion to the sedimentary carbon budget. The models suggest that similar to 40% of all carbon released by local coastal permafrost erosion is efficiently trapped and sequestered in the nearshore zone. This highlights the importance of sedimentary traps in environments such as basins, lagoons, troughs, and canyons for the carbon sequestration in previously poorly investigated, nearshore areas. 

Plain Language Summary Increasing air and sea surface temperatures at high latitudes leads to accelerated thaw, destabilization, and erosion of perennially frozen soils (i.e., permafrost), which are often rich in organic carbon. Coastal erosion leads to an increased mobilization of organic carbon into the Arctic Ocean, which there can be converted into greenhouse gases and may therefore contribute to further warming. Carbon decomposition can be limited if organic matter is efficiently deposited on the seafloor, buried in marine sediments, and thus removed from the short-term carbon cycle. Basins, canyons, and troughs near the coastline can serve as sediment traps and potentially accommodate large quantities of organic carbon along the Arctic coast. Here we use biomarkers (source-specific molecules), stable carbon isotopes, and radiocarbon to identify the sources of organic carbon in the nearshore zone of the southern Canadian Beaufort Sea near Herschel Island. We quantify the contribution of coastal permafrost erosion to the sedimentary carbon budget of the area and estimate that more than a third of all carbon released by local permafrost erosion is efficiently trapped in marine sediments. This highlights the importance of regional sediment traps for carbon sequestration.
Y1  - 2020
U6  - https://doi.org/10.1029/2019GL085897
SN  - 0094-8276
SN  - 1944-8007
VL  - 47
IS  - 3
PB  - Wiley
CY  - Hoboken, NJ
ER  - 
TY  - JOUR
A1  - Powali, Debarchan
A1  - Sharma, Shubham
A1  - Mandal, Riddhi
A1  - Mitra, Supriyo
T1  - A reappraisal of the 2005 Kashmir (M-w 7.6) earthquake and its aftershocks
BT  - seismotectonics of NW Himalaya
JF  - Tectonophysics : international journal of geotectonics and the geology and physics of the interior of the earth
N2  - We study the source properties of the 2005 Kashmir earthquake and its aftershocks to unravel the seismotectonics of the NW Himalayan syntaxis. The mainshock and larger aftershocks have been simultaneously relocated using phase data. We use back-projection of high-frequency energy from multiple teleseismic arrays to model the spatio-temporal evolution of the mainshock rupture. Our analysis reveal a bilateral rupture, which initially propagated SE and then NW of the epicenter, with an average rupture velocity of similar to 2 km s(-1). The area of maximum energy release is parallel to and bound by the surface rupture. Incorporating rupture propagation and velocity, we model the mainshock as a line source using P- and SH-waveform inversion. Our result confirms that the mainshock occurred on a NE dipping (similar to 35 degrees) fault plane, with centroid depth of similar to 10 km. Integrated source time function show that majority of the energy was released in the first similar to 20 s, and was confined above the hypocenter. From waveform inverted fault dimension and seismic moment, we argue that the mainshock had an additional similar to 25 km blind rupture beyond the NW Himalayan syntaxis. Combining this with findings from previous studies, we conjecture that the blind rupture propagated NW of the syntaxis underneath a weak detachment overlain by infra-Cambrian salt layer, and terminated in a wedge thrust. All moderate-to-large aftershocks, NW of the mainshock rupture, are concentrated at the edge of the blind rupture termination. Source modeling of these aftershocks reveal thrust mechanism with centroid depths of 2-10 km, and fault planes oriented subparallel to the mainshock rupture. To study the influence of mainshock rupture on aftershock occurrence, we compute Coulomb failure stress on aftershock faults. All these aftershocks lie in the positive Coulomb stress change region. This suggest that the aftershocks have been triggered by either co-seismic or post-seismic slip on the mainshock fault.
KW  - Kashmir earthquake
KW  - Aftershocks
KW  - High frequency back-projection
KW  - Source
KW  - mechanism
KW  - Coulomb failure stress
KW  - Seismo-tectonics
Y1  - 2020
U6  - https://doi.org/10.1016/j.tecto.2020.228501
SN  - 0040-1951
SN  - 1879-3266
VL  - 789
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Volante, Silvia
A1  - Pourteau, Amaury
A1  - Collins, William J.
A1  - Blereau, Eleanore
A1  - Li, Zheng-Xiang
A1  - Smit, Matthijs Arjen
A1  - Evans, Noreen
A1  - Nordsvan, Adam R.
A1  - Spencer, Chris J.
A1  - McDonald, Brad J.
A1  - Li, Jiangyu
A1  - Günter, Christina
T1  - Multiple P-T-d-t paths reveal the evolution of the final Nuna assembly in northeast Australia
JF  - Journal of metamorphic geology
N2  - The final assembly of the Mesoproterozoic supercontinent Nuna was marked by the collision of Laurentia and Australia at 1.60 Ga, which is recorded in the Georgetown Inlier of NE Australia. Here, we decipher the metamorphic evolution of this final Nuna collisional event using petrostructural analysis, major and trace element compositions of key minerals, thermodynamic modelling, and multi-method geochronology. The Georgetown Inlier is characterised by deformed and metamorphosed 1.70-1.62 Ga sedimentary and mafic rocks, which were intruded byc. 1.56 Ga old S-type granites. Garnet Lu-Hf and monazite U-Pb isotopic analyses distinguish two major metamorphic events (M1 atc. 1.60 Ga and M2 atc. 1.55 Ga), which allows at least two composite fabrics to be identified at the regional scale-c. 1.60 Ga S1 (consisting in fabrics S1a and S1b) andc. 1.55 Ga S2 (including fabrics S2a and S2b). Also, three tectono-metamorphic domains are distinguished: (a) the western domain, with S1 defined by low-P(LP) greenschist facies assemblages; (b) the central domain, where S1 fabric is preserved as medium-P(MP) amphibolite facies relicts, and locally as inclusion trails in garnet wrapped by the regionally dominant low-Pamphibolite facies S2 fabric; and (c) the eastern domain dominated by upper amphibolite to granulite facies S2 foliation. In the central domain, 1.60 GaMP-medium-T(MT) metamorphism (M1) developed within the staurolite-garnet stability field, with conditions ranging from 530-550 degrees C at 6-7 kbar (garnet cores) to 620-650 degrees C at 8-9 kbar (garnet rims), and it is associated with S1 fabric. The onset of 1.55 GaLP-high-T(HT) metamorphism (M2) is marked by replacement of staurolite by andalusite (M2a/D2a), which was subsequently pseudomorphed by sillimanite (M2b/D2b) where granite and migmatite are abundant.P-Tconditions ranged from 600 to 680 degrees C and 4-6 kbar for the M2b sillimanite stage. 1.60 Ga garnet relicts within the S2 foliation highlight the progressive obliteration of the S1 fabric by regional S2 in the central zone during peak M2 metamorphism. In the eastern migmatitic complex, partial melting of paragneiss and amphibolite occurred syn- to post-S2, at 730-770 degrees C and 6-8 kbar, and at 750-790 degrees C and 6 kbar, respectively. The pressure-temperature-deformation-time paths reconstructed for the Georgetown Inlier suggest ac. 1.60 Ga M1/D1 event recorded under greenschist facies conditions in the western domain and under medium-Pand medium-Tconditions in the central domain. This event was followed by the regional 1.56-1.54 Ga low-Pand high-Tphase (M2/D2), extensively recorded in the central and eastern domains. Decompression between these two metamorphic events is ascribed to an episode of exhumation. The two-stage evolution supports the previous hypothesis that the Georgetown Inlier preserves continental collisional and subsequent thermal perturbation associated with granite emplacement.
KW  - continental collision
KW  - Lu-Hf in garnet
KW  - petrostructural analysis
KW  - P-T-d-tpaths
KW  - supercontinent Nuna
Y1  - 2020
U6  - https://doi.org/10.1111/jmg.12532
SN  - 0263-4929
SN  - 1525-1314
VL  - 38
IS  - 6
SP  - 593
EP  - 627
PB  - Wiley-Blackwell
CY  - Oxford [u.a.]
ER  - 
TY  - JOUR
A1  - Hennig, Theresa
A1  - Stockmann, Madlen
A1  - Kühn, Michael
T1  - Simulation of diffusive uranium transport and sorption processes in the Opalinus Clay
JF  - Applied geochemistry : journal of the International Association of Geochemistry and Cosmochemistry
N2  - Diffusive transport and sorption processes of uranium in the Swiss Opalinus Clay were investigated as a function of partial pressure of carbon dioxide pCO(2), varying mineralogy in the facies and associated changes in porewater composition. Simulations were conducted in one-dimensional diffusion models on the 100 m-scale for a time of one million years using a bottom-up approach based on mechanistic surface complexation models as well as cation exchange to quantify sorption. Speciation calculations have shown, uranium is mainly present as U(VI) and must therefore be considered as mobile for in-situ conditions. Uranium migrated up to 26 m in both, the sandy and the carbonate-rich facies, whereas in the shaly facies 16 m was the maximum. The main species was the anionic complex CaUO2(CO3)(3)(2-) . Hence, anion exclusion was taken into account and further reduced the migration distances by 30 %. The concentrations of calcium and carbonates reflected by the set pCO(2) determine speciation and activity of uranium and consequently the sorption behaviour. Our simulation results allow for the first time to prioritize on the far-field scale the governing parameters for diffusion and sorption of uranium and hence outline the sensitivity of the system. Sorption processes are controlled in descending priority by the carbonate and calcium concentrations, pH, pe and the clay mineral content. Therefore, the variation in porewater composition resulting from the heterogeneity of the facies in the Opalinus Clay formation needs to be considered in the assessment of uranium migration in the far field of a potential repository.
KW  - reactive transport
KW  - facies
KW  - heterogeneity
KW  - carbonate
KW  - PHREEQC
KW  - Mont Terri
KW  - speciation
Y1  - 2020
U6  - https://doi.org/10.1016/j.apgeochem.2020.104777
SN  - 0883-2927
SN  - 1872-9134
VL  - 123
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Tranter, Morgan Alan
A1  - De Lucia, Marco
A1  - Wolfgramm, Markus
A1  - Kühn, Michael
T1  - Barite scale formation and injectivity loss models for geothermal systems
JF  - Water
N2  - Barite scales in geothermal installations are a highly unwanted effect of circulating deep saline fluids. They build up in the reservoir if supersaturated fluids are re-injected, leading to irreversible loss of injectivity. A model is presented for calculating the total expected barite precipitation. To determine the related injectivity decline over time, the spatial precipitation distribution in the subsurface near the injection well is assessed by modelling barite growth kinetics in a radially diverging Darcy flow domain. Flow and reservoir properties as well as fluid chemistry are chosen to represent reservoirs subject to geothermal exploration located in the North German Basin (NGB) and the Upper Rhine Graben (URG) in Germany. Fluids encountered at similar depths are hotter in the URG, while they are more saline in the NGB. The associated scaling amount normalised to flow rate is similar for both regions. The predicted injectivity decline after 10 years, on the other hand, is far greater for the NGB (64%) compared to the URG (24%), due to the temperature- and salinity-dependent precipitation rate. The systems in the NGB are at higher risk. Finally, a lightweight score is developed for approximating the injectivity loss using the Damkohler number, flow rate and total barite scaling potential. This formula can be easily applied to geothermal installations without running complex reactive transport simulations.
KW  - reactive transport
KW  - radial flow
KW  - geothermal energy
KW  - scaling
KW  - phreeqc
KW  - formation damage
Y1  - 2020
U6  - https://doi.org/10.3390/w12113078
SN  - 2073-4441
VL  - 12
IS  - 11
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Castino, Fabiana
A1  - Bookhagen, Bodo
A1  - De la Torre, Alejandro
T1  - Atmospheric dynamics of extreme discharge events from 1979 to 2016 in the southern Central Andes
JF  - Climate dynamics : observational, theoretical and computational research on the climate system
N2  - During the South-American Monsoon season, deep convective systems occur at the eastern flank of the Central Andes leading to heavy rainfall and flooding. We investigate the large- and meso-scale atmospheric dynamics associated with extreme discharge events (> 99.9th percentile) observed in two major river catchments meridionally stretching from humid to semi-arid conditions in the southern Central Andes. Based on daily gauge time series and ERA-Interim reanalysis, we made the following three key observations: (1) for the period 1940-2016 daily discharge exhibits more pronounced variability in the southern, semi-arid than in the northern, humid catchments. This is due to a smaller ratio of discharge magnitudes between intermediate (0.2 year return period) and rare events (20 year return period) in the semi-arid compared to the humid areas; (2) The climatological composites of the 40 largest discharge events showed characteristic atmospheric features of cold surges based on 5-day time-lagged sequences of geopotential height at different levels in the troposphere; (3) A subjective classification revealed that 80% of the 40 largest discharge events are mainly associated with the north-northeastward migration of frontal systems and 2/3 of these are cold fronts, i.e. cold surges. This work highlights the importance of cold surges and their related atmospheric processes for the generation of heavy rainfall events and floods in the southern Central Andes.
KW  - South American monsoon system
KW  - cold surges
KW  - orographic barrier
KW  - mesoscale convective systems
KW  - extreme discharge
KW  - daily-discharge time
KW  - series ERA-interim
Y1  - 2019
U6  - https://doi.org/10.1007/s00382-020-05458-1
SN  - 0930-7575
SN  - 1432-0894
VL  - 55
IS  - 11-12
SP  - 3485
EP  - 3505
PB  - Springer
CY  - Berlin ; Heidelberg [u.a.]
ER  - 
TY  - JOUR
A1  - Ramachandran, Srikanthan
A1  - Rupakheti, Maheswar
A1  - Lawrence, Mark
T1  - Black carbon dominates the aerosol absorption over the Indo-Gangetic Plain and the Himalayan foothills
JF  - Environment international : a journal of science, technology, health, monitoring and policy
N2  - This study, based on new and high quality in situ observations, quantifies for the first time, the individual contributions of light-absorbing aerosols (black carbon (BC), brown carbon (BrC) and dust) to aerosol absorption over the Indo-Gangetic Plain (IGP) and the Himalayan foothill region, a relatively poorly studied region with several sensitive ecosystems of global importance, as well as highly vulnerable populations. The annual and seasonal average single scattering albedo (SSA) over Kathmandu is the lowest of all the locations. The SSA over Kathmandu is < 0.89 during all seasons, which confirms the dominance of light-absorbing carbonaceous aerosols from local and regional sources over Kathmandu. It is observed here that the SSA decreases with increasing elevation, confirming the dominance of light absorbing carbonaceous aerosols at higher elevations. In contrast, the SSA over the IGP does not exhibit a pronounced spatial variation. BC dominates (>= 75%) the aerosol absorption over the IGP and the Himalayan foothills throughout the year. Higher BC concentration at elevated locations in the Himalayas leads to lower SSA at elevated locations in the Himalayas. The contribution of dust to aerosol absorption is higher throughout the year over the IGP than over the Himalayan foothills. The aerosol absorption over South Asia is very high, exceeding available observations over East Asia, and also exceeds previous model estimates. This quantification will be valuable as observational constraints to help improve regional simulations of climate change, impacts on the glaciers and the hydrological cycle, and will help to direct the focus towards BC as the main contributor to aerosol-induced warming in the region.
KW  - atmospheric aerosols
KW  - characteristics
KW  - absorption
KW  - black carbon
KW  - brown
KW  - carbon
KW  - dust
KW  - Himalayas
KW  - IGP
KW  - South Asia
Y1  - 2020
U6  - https://doi.org/10.1016/j.envint.2020.105814
SN  - 0160-4120
SN  - 1873-6750
VL  - 142
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Durand, Virginie
A1  - Bentz, Stephan
A1  - Kwiatek, Grzegorz
A1  - Dresen, Georg
A1  - Wollin, Christopher
A1  - Heidbach, Oliver
A1  - Martinez-Garzon, Patricia
A1  - Cotton, Fabrice
A1  - Nurlu, Murat
A1  - Bohnhoff, Marco
T1  - A two-scale preparation phase preceded an M-w 5.8 earthquake in the sea of marmara offshore Istanbul, Turkey
JF  - Seismological research letters
N2  - We analyze the spatiotemporal evolution of seismicity during a sequence of moderate (an M-w 4.7 foreshock and M-w 5.8 mainshock) earthquakes occurring in September 2019 at the transition between a creeping and a locked segment of the North Anatolian fault in the central Sea of Marmara, northwest Turkey. To investigate in detail the seismicity evolution, we apply a matched-filter technique to continuous waveforms, thus reducing the magnitude threshold for detection. Sequences of foreshocks preceding the two largest events are clearly seen, exhibiting two different behaviors: a long-term activation of the seismicity along the entire fault segment and a short-term concentration around the epicenters of the large events. We suggest a two-scale preparation phase, with aseismic slip preparing the mainshock final rupture a few days before, and a cascade mechanism leading to the nucleation of the mainshock. Thus, our study shows a combination of seismic and aseismic slip during the foreshock sequence changing the strength of the fault, bringing it closer to failure.
Y1  - 2020
U6  - https://doi.org/10.1785/0220200110
SN  - 0895-0695
SN  - 1938-2057
VL  - 91
IS  - 6
SP  - 3139
EP  - 3147
CY  - Boulder
ER  - 
TY  - JOUR
A1  - Zozulya, Dmitry R.
A1  - Kullerud, Kare
A1  - Ribacki, Enrico
A1  - Altenberger, Uwe
A1  - Sudo, Masafumi
A1  - Savchenko, Yevgeny E.
T1  - The newly discovered neoproterozoic aillikite occurrence in Vinoren (Southern Norway)
BT  - age, geodynamic position and mineralogical evidence of diamond-bearing mantle source
JF  - Minerals
N2  - During the period 750-600 Ma ago, prior to the final break-up of the supercontinent Rodinia, the crust of both the North American Craton and Baltica was intruded by significant amounts of rift-related magmas originating from the mantle. In the Proterozoic crust of Southern Norway, the 580 Ma old Fen carbonatite-ultramafic complex is a representative of this type of rocks. In this paper, we report the occurrence of an ultramafic lamprophyre dyke which possibly is linked to the Fen complex, although Ar-40/Ar-39 data from phenocrystic phlogopite from the dyke gave an age of 686 +/- 9 Ma. The lamprophyre dyke was recently discovered in one of the Kongsberg silver mines at Vinoren, Norway. Whole rock geochemistry, geochronological and mineralogical data from the ultramafic lamprophyre dyke are presented aiming to elucidate its origin and possible geodynamic setting. From the whole-rock composition of the Vinoren dyke, the rock could be recognized as transitional between carbonatite and kimberlite-II (orangeite). From its diagnostic mineralogy, the rock is classified as aillikite. The compositions and xenocrystic nature of several of the major and accessory minerals from the Vinoren aillikite are characteristic for diamondiferous rocks (kimberlites/lamproites/UML): Phlogopite with kinoshitalite-rich rims, chromite-spinel-ulvospinel series, Mg- and Mn-rich ilmenites, rutile and lucasite-(Ce). We suggest that the aillikite melt formed during partial melting of a MARID (mica-amphibole-rutile-ilmenite-diopside)-like source under CO2 fluxing. The pre-rifting geodynamic setting of the Vinoren aillikite before the Rodinia supercontinent breakup suggests a relatively thick SCLM (Subcontinental Lithospheric Mantle) during this stage and might indicate a diamond-bearing source for the parental melt. This is in contrast to the about 100 Ma younger Fen complex, which were derived from a thin SCLM.
KW  - aillikite
KW  - phlogopite
KW  - carbonate
KW  - spinel
KW  - ilmenite
KW  - titanite
KW  - diamond
KW  - Vinoren
KW  - Southern Norway
Y1  - 2020
U6  - https://doi.org/10.3390/min10111029
SN  - 2075-163X
VL  - 10
IS  - 11
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - von Specht, Sebastian
A1  - Cotton, Fabrice
T1  - A link between machine learning and optimization in ground-motion model development
BT  - weighted mixed-effects regression with data-driven probabilistic earthquake classification
JF  - Bulletin of the Seismological Society of America
N2  - The steady increase of ground-motion data not only allows new possibilities but also comes with new challenges in the development of ground-motion models (GMMs). Data classification techniques (e.g., cluster analysis) do not only produce deterministic classifications but also probabilistic classifications (e.g., probabilities for each datum to belong to a given class or cluster). One challenge is the integration of such continuous classification in regressions for GMM development such as the widely used mixed-effects model. We address this issue by introducing an extension of the mixed-effects model to incorporate data weighting. The parameter estimation of the mixed-effects model, that is, fixed-effects coefficients of the GMMs and the random-effects variances, are based on the weighted likelihood function, which also provides analytic uncertainty estimates. The data weighting permits for earthquake classification beyond the classical, expert-driven, binary classification based, for example, on event depth, distance to trench, style of faulting, and fault dip angle. We apply Angular Classification with Expectation-maximization, an algorithm to identify clusters of nodal planes from focal mechanisms to differentiate between, for example, interface- and intraslab-type events. Classification is continuous, that is, no event belongs completely to one class, which is taken into account in the ground-motion modeling. The theoretical framework described in this article allows for a fully automatic calibration of ground-motion models using large databases with automated classification and processing of earthquake and ground-motion data. As an example, we developed a GMM on the basis of the GMM by Montalva et al. (2017) with data from the strong-motion flat file of Bastias and Montalva (2016) with similar to 2400 records from 319 events in the Chilean subduction zone. Our GMM with the data-driven classification is comparable to the expert-classification-based model. Furthermore, the model shows temporal variations of the between-event residuals before and after large earthquakes in the region.
Y1  - 2020
U6  - https://doi.org/10.1785/0120190133
SN  - 0037-1106
SN  - 1943-3573
VL  - 110
IS  - 6
SP  - 2777
EP  - 2800
PB  - Seismological Society of America
CY  - Albany
ER  - 
TY  - JOUR
A1  - Sieber, Melanie Jutta
A1  - Yaxley, Gregory M.
A1  - Hermann, Jörg
T1  - Investigation of fluid-driven carbonation of a hydrated, forearc mantle wedge using serpentinite cores in high-pressure experiments
JF  - Journal of petrology
N2  - High-pressure experiments were performed to investigate the effectiveness, rate and mechanism of carbonation of serpentinites by a carbon-saturated COH fluid at 1.5-2.5 GPa and 375-700 degrees C. This allows a better understanding of the fate and redistribution of slab-derived carbonic fluids when they react with the partially hydrated mantle within and above the subducting slab under pressure and temperature conditions corresponding to the forearc mantle. Interactions between carbon-saturated CO2-H2O-CH4 fluids and serpentinite were investigated using natural serpentinite cylinders with natural grain sizes and shapes in piston-cylinder experiments. The volatile composition of post-run fluids was quantified by gas chromatography. Solid phases were examined by Raman spectroscopy, electron microscopy and laser ablation inductively coupled plasma mass spectrometry. Textures, porosity and phase abundances of recovered rock cores were visualized and quantified by three-dimensional, high-resolution computed tomography. We find that carbonation of serpentinites is efficient at sequestering CO2 from the interacting fluid into newly formed magnesite. Time-series experiments demonstrate that carbonation is completed within similar to 96 h at 2 GPa and 600 degrees C. With decreasing CO2, aq antigorite is replaced first by magnesite + quartz followed by magnesite + talc + chlorite in distinct, metasomatic fronts. Above antigorite stability magnesite + enstatite + talc + chlorite occur additionally. The formation of fluid-permeable reaction zones enhances the reaction rate and efficiency of carbonation. Carbonation probably occurs via an interface-coupled replacement process, whereby interconnected porosity is present within reaction zones after the experiment. Consequently, carbonation of serpentinites is self-promoting and efficient even if fluid flow is channelized into veins. We conclude that significant amounts of carbonates may accumulate, over time, in the hydrated forearc mantle.
KW  - serpentinite carbonation
KW  - deep carbon cycle
KW  - COH fluid
KW  - forearc
KW  - CO2
KW  - sequestration
Y1  - 2020
U6  - https://doi.org/10.1093/petrology/egaa035
SN  - 0022-3530
SN  - 1460-2415
VL  - 61
IS  - 3
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Calitri, Francesca
A1  - Sommer, Michael
A1  - van der Meij, Marijn W.
A1  - Egli, Markus
T1  - Soil erosion along a transect in a forested catchment: recent or ancient processes?
JF  - Catena : an interdisciplinary journal of soil science, hydrology, geomorphology focusing on geoecology and landscape evolution
N2  - Forested areas are assumed not to be influenced by erosion processes. However, forest soils of Northern Germany in a hummocky ground moraine landscape can sometimes exhibit a very shallow thickness on crest positions and buried soils on slope positions. The question consequently is: Are these on-going or ancient erosional and depositional processes? Plutonium isotopes act as soil erosion/deposition tracers for recent (last few decades) processes. Here, we quantified the 239+240PU inventories in a small, forested catchment (ancient forest "Melzower Forst", deciduous trees), which is characterised by a hummocky terrain including a kettle hole. Soil development depths (depth to C horizon) and 239+240PU inventories along a catena of sixteen different profiles were determined and correlated to relief parameters. Moreover, we compared different modelling approaches to derive erosion rates from Pu data. <br /> We find a strong relationship between soil development depths, distance-to-sink and topography along the catena. Fully developed Retisols (thicknesses > 1 m) in the colluvium overlay old land surfaces as documented by fossil Ah horizons. However, we found no relationship of Pu-based erosion rates to any relief parameter. Instead, 239+240PU inventories showed a very high local, spatial variability (36-70 Bq m(-2)). Low annual rainfall, spatially distributed interception and stem flow might explain the high variability of the 239+240PU inventories, giving rise to a patchy input pattern. Different models resulted in quite similar erosion and deposition rates (max: -5 t ha(-1) yr(-1) to +7.3 t ha(-1) yr(-1)). Although some rates are rather high, the magnitude of soil erosion and deposition - in terms of soil thickness change - is negligible during the last 55 years. The partially high values are an effect of the patchy Pu deposition on the forest floor. This forest has been protected for at least 240 years. Therefore rather natural events and anthropogenic activities during medieval times or even earlier must have caused the observed soil pattern, which documents strong erosion and deposition processes.
KW  - Soil erosion
KW  - 239+240 Plutonium
KW  - Forest
KW  - Moraine landscape
KW  - Soil catena
Y1  - 2020
U6  - https://doi.org/10.1016/j.catena.2020.104683
SN  - 0341-8162
SN  - 1872-6887
VL  - 194
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Zhang, Liyu
A1  - Chen, Daizhao
A1  - Kuang, Guodun
A1  - Guo, Zenghui
A1  - Zhang, Gongjing
A1  - Wang, Xia
T1  - Persistent oxic deep ocean conditions and frequent volcanic activities during the Frasnian-Famennian transition recorded in South China
JF  - Global and planetary change
N2  - The Frasnian-Famennian (F-F) transition of Late Devonian was a critical episode in geological history, recording a major mass extinction event. In this study, we focus on an F-F succession from a deep marine context in Bancheng, southern Guangxi, South China, to investigate coeval changes in pelagic environments of the Paleo-Tethys Ocean. The studied succession is exclusively composed of bedded cherts intercalated with multiple siliceous volcanic ash beds. A SIMS zircon U-Pb Concordia age of 367.8 +/- 2.5 Ma is reported for a tuffaceous layer slightly above the F-F boundary. Geochemical ratios of Al/(Al + Fe + Mn), Ce/Ce*, Y/Ho, and Al, Fe contents in bedded cherts indicate that they are of predominantly biogenic/chemical origin with some terrigenous inputs. Negligible enrichment of redox sensitive elements (Mo, U, V) and low V/Cr ratios (<2) suggest persistently oxic conditions existed in the deep pelagic basin at Bancheng, South China during the F-F transition. These findings call into question the widely held hypothesis that marine anoxia was the primary killing mechanism for the F-F crisis. In contrast, multiple tuffaceous layers throughout the F-F boundary succession indicate frequent volcanic activity, which could have released massive amounts of greenhouse gases into the atmosphere, inducing climate warming. This scenario may have increased continental weathering and riverine fluxes into the ocean, reconciling the increases in Al2O3 content and Al/(Al + Fe + Mn) ratio across the F-F boundary. Documentation of persistently oxic conditions and frequent volcanic activitiy provides new perspectives on the inter-relationship between volcanism, climate, and oceanic redox fluctuation during the F-F biotic crisis.
KW  - Late Devonian
KW  - Bedded chert
KW  - Major and trace elements
KW  - Deep ocean redox condition
KW  - Volcanic activity
KW  - Zircon U-Pb dating
Y1  - 2020
U6  - https://doi.org/10.1016/j.gloplacha.2020.103350
SN  - 0921-8181
VL  - 195
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Brill, Fabio Alexander
A1  - Passuni Pineda, Silvia
A1  - Espichan Cuya, Bruno
A1  - Kreibich, Heidi
T1  - A data-mining approach towards damage modelling for El Nino events in Peru
JF  - Geomatics, natural hazards and risk
N2  - Compound natural hazards likeEl Ninoevents cause high damage to society, which to manage requires reliable risk assessments. Damage modelling is a prerequisite for quantitative risk estimations, yet many procedures still rely on expert knowledge, and empirical studies investigating damage from compound natural hazards hardly exist. A nationwide building survey in Peru after theEl Ninoevent 2017 - which caused intense rainfall, ponding water, flash floods and landslides - enables us to apply data-mining methods for statistical groundwork, using explanatory features generated from remote sensing products and open data. We separate regions of different dominant characteristics through unsupervised clustering, and investigate feature importance rankings for classifying damage via supervised machine learning. Besides the expected effect of precipitation, the classification algorithms select the topographic wetness index as most important feature, especially in low elevation areas. The slope length and steepness factor ranks high for mountains and canyons. Partial dependence plots further hint at amplified vulnerability in rural areas. An example of an empirical damage probability map, developed with a random forest model, is provided to demonstrate the technical feasibility.
KW  - Natural hazard
KW  - damage model
KW  - residential buildings
KW  - data-mining
KW  - remote
KW  - sensing
KW  - open data
Y1  - 2020
U6  - https://doi.org/10.1080/19475705.2020.1818636
SN  - 1947-5705
SN  - 1947-5713
VL  - 11
IS  - 1
SP  - 1966
EP  - 1990
PB  - Routledge, Taylor & Francis Group
CY  - Abingdon
ER  - 
TY  - JOUR
A1  - Wietzke, Luzie M.
A1  - Merz, Bruno
A1  - Gerlitz, Lars
A1  - Kreibich, Heidi
A1  - Guse, Björn
A1  - Castellarin, Attilio
A1  - Vorogushyn, Sergiy
T1  - Comparative analysis of scalar upper tail indicators
JF  - Hydrological sciences journal = Journal des sciences hydrologiques
N2  - Different upper tail indicators exist to characterize heavy tail phenomena, but no comparative study has been carried out so far. We evaluate the shape parameter (GEV), obesity index, Gini index and upper tail ratio (UTR) against a novel benchmark of tail heaviness - the surprise factor. Sensitivity analyses to sample size and changes in scale-to-location ratio are carried out in bootstrap experiments. The UTR replicates the surprise factor best but is most uncertain and only comparable between records of similar length. For samples with symmetric Lorenz curves, shape parameter, obesity and Gini indices provide consistent indications. For asymmetric Lorenz curves, however, the first two tend to overestimate, whereas Gini index tends to underestimate tail heaviness. We suggest the use of a combination of shape parameter, obesity and Gini index to characterize tail heaviness. These indicators should be supported with calculation of the Lorenz asymmetry coefficients and interpreted with caution.
KW  - upper tail behaviour
KW  - heavy-tailed distributions
KW  - extremes
KW  - diagnostics
KW  - surprise
Y1  - 2020
U6  - https://doi.org/10.1080/02626667.2020.1769104
SN  - 0262-6667
SN  - 2150-3435
VL  - 65
IS  - 10
SP  - 1625
EP  - 1639
PB  - Routledge, Taylor & Francis Group
CY  - Abingdon
ER  - 
TY  - JOUR
A1  - Kruse, Stefan
A1  - Kolmogorov, Aleksey I.
A1  - Pestryakova, Luidmila Agafyevna
A1  - Herzschuh, Ulrike
T1  - Long-lived larch clones may conserve adaptations that could restrict treeline migration in northern Siberia
JF  - Ecology and evolution
N2  - The occurrence of refugia beyond the arctic treeline and genetic adaptation therein play a crucial role of largely unknown effect size. While refugia have potential for rapidly colonizing the tundra under global warming, the taxa may be maladapted to the new environmental conditions. Understanding the genetic composition and age of refugia is thus crucial for predicting any migration response. 
Here, we genotype 194 larch individuals from an similar to 1.8 km(2)area in northcentral Siberia on the southern Taimyr Peninsula by applying an assay of 16 nuclear microsatellite markers. For estimating the age of clonal individuals, we counted tree rings at sections along branches to establish a lateral growth rate that was then combined with geographic distance.
Findings reveal that the predominant reproduction type is clonal (58.76%) by short distance spreading of ramets. One outlier of clones 1 km apart could have been dispersed by reindeer. In clonal groups and within individuals, we find that somatic mutations accumulate with geographic distance. Clonal groups of two or more individuals are observed. Clonal age estimates regularly suggest individuals as old as 2,200 years, which coincides with a major environmental change that forced a treeline retreat in the region. 
We conclude that individuals with clonal growth mode were naturally selected as it lowers the likely risk of extinction under a harsh environment. We discuss this legacy from the past that might now be a maladaptation and hinder expansion under currently strongly increasing temperatures.
KW  - adaptation
KW  - clonal growth
KW  - growth rate
KW  - Larix
KW  - leading edge
KW  - treeline
KW  - migration
Y1  - 2020
U6  - https://doi.org/10.1002/ece3.6660
SN  - 2045-7758
VL  - 10
IS  - 18
SP  - 10017
EP  - 10030
PB  - Wiley
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Voss, Katalyn A.
A1  - Bookhagen, Bodo
A1  - Sachse, Dirk
A1  - Chadwick, Oliver A.
T1  - Variation of deuterium excess in surface waters across a 5000-m elevation gradient in eastern Nepal
JF  - Journal of hydrology
N2  - The strong elevation gradient of the Himalaya allows for investigation of altitude and orographic impacts on surface water delta O-18 and delta D stable isotope values. This study differentiates the time- and altitude-variable contributions of source waters to the Arun River in eastern Nepal. It provides isotope data along a 5000-m gradient collected from tributaries as well as groundwater, snow, and glacial-sourced surface waters and time-series data from April to October 2016. We find nonlinear trends in delta O-18 and delta D lapse rates with high-elevation lapse rates (4000-6000 masl) 5-7 times more negative than low-elevation lapse rates (1000-3000 masl). A distinct seasonal signal in delta O-18 and delta D lapse rates indicates time-variable source-water contributions from glacial and snow meltwater as well as precipitation transitions between the Indian Summer Monsoon and Winter Westerly Disturbances. Deuterium excess correlates with the extent of snowpack and tracks melt events during the Indian Summer Monsoon season. Our analysis identifies the influence of snow and glacial melt waters on river composition during low-flow conditions before the monsoon (April/May 2016) followed by a 5-week transition to the Indian Summer Monsoon-sourced rainfall around mid-June 2016. In the post-monsoon season, we find continued influence from glacial melt waters as well as ISM-sourced groundwater.
KW  - stable isotopes
KW  - Himalaya
KW  - glacier
KW  - snow
KW  - precipitation
KW  - seasonality
Y1  - 2020
U6  - https://doi.org/10.1016/j.jhydrol.2020.124802
SN  - 0022-1694
SN  - 1879-2707
VL  - 586
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Ganguli, Poulomi
A1  - Paprotny, Dominik
A1  - Hasan, Mehedi
A1  - Güntner, Andreas
A1  - Merz, Bruno
T1  - Projected changes in compound flood hazard from riverine and coastal floods in northwestern Europe
JF  - Earth's future
N2  - Compound flooding in coastal regions, that is, the simultaneous or successive occurrence of high sea levels and high river flows, is expected to increase in a warmer world. To date, however, there is no robust evidence on projected changes in compound flooding for northwestern Europe. We combine projected storm surges and river floods with probabilistic, localized relative sea-level rise (SLR) scenarios to assess the future compound flood hazard over northwestern coastal Europe in the high (RCP8.5) emission scenario. We use high-resolution, dynamically downscaled regional climate models (RCM) to drive a storm surge model and a hydrological model, and analyze the joint occurrence of high coastal water levels and associated river peaks in a multivariate copula-based approach. The RCM-forced multimodel mean reasonably represents the observed spatial pattern of the dependence strength between annual maxima surge and peak river discharge, although substantial discrepancies exist between observed and simulated dependence strength. All models overestimate the dependence strength, possibly due to limitations in model parameterizations. This bias affects compound flood hazard estimates and requires further investigation. While our results suggest decreasing compound flood hazard over the majority of sites by 2050s (2040-2069) compared to the reference period (1985-2005), an increase in projected compound flood hazard is limited to around 34% of the sites. Further, we show the substantial role of SLR, a driver of compound floods, which has frequently been neglected. Our findings highlight the need to be aware of the limitations of the current generation of Earth system models in simulating coastal compound floods.
KW  - compound flood
KW  - storm surge
KW  - river floods
KW  - sea level rise
KW  - climate
KW  - change
KW  - Europe
Y1  - 2020
U6  - https://doi.org/10.1029/2020EF001752
SN  - 2328-4277
VL  - 8
IS  - 11
PB  - Wiley-Blackwell
CY  - Hoboken, NJ
ER  - 
TY  - JOUR
A1  - Vogt-Vincent, Noam
A1  - Lippold, Jörg
A1  - Kaboth-Bahr, Stefanie
A1  - Blaser, Patrick
T1  - Ice-rafted debris as a source of non-conservative behaviour for the epsilon Nd palaeotracer
BT  - insights from a simple model
JF  - Geo-marine letters : an international journal of marine geology
N2  - Neodymium isotopic composition (epsilon Nd) has enjoyed widespread use as a palaeotracer, principally because it behaves quasi-conservatively in the modern ocean. However, recent bottom water epsilon Nd reconstructions from the eastern North Atlantic are difficult to interpret under assumptions of conservative behaviour. The observation that this apparent departure from conservative behaviour increases with enhanced ice-rafted debris (IRD) fluxes has resulted in the suggestion that IRD leads to the overprinting of bottom water epsilon Nd through reversible scavenging. In this study, a simple water column model successfully reproduces epsilon Nd reconstructions from the eastern North Atlantic at the Last Glacial Maximum and Heinrich Stadial 1, and demonstrates that the changes in scavenging intensity required for good model-data fit is in good agreement with changes in the observed IRD flux. Although uncertainties in model parameters preclude a more definitive conclusion, the results indicate that the suggestion of IRD as a source of non-conservative behaviour in the epsilon Nd tracer is reasonable and that further research into the fundamental chemistry underlying the marine neodymium cycle is necessary to increase confidence in assumptions of conservative epsilon Nd behaviour in the past.
KW  - Neodymium isotopes
KW  - epsilon Nd
KW  - ice-rafted debris
KW  - IRD
KW  - last glacial
KW  - maximum
KW  - LGM
KW  - Heinrich event
KW  - Palaeoceanography
KW  - Paleoceanography
KW  - model
KW  - reversible scavenging
KW  - conservative
KW  - ocean circulation
KW  - atlantic
KW  - meridional overturning circulation
KW  - geochemical cycling
Y1  - 2020
U6  - https://doi.org/10.1007/s00367-020-00643-x
SN  - 0276-0460
SN  - 1432-1157
VL  - 40
IS  - 3
SP  - 325
EP  - 340
PB  - Springer
CY  - Berlin
ER  - 
TY  - JOUR
A1  - Huang, Sichao
A1  - Herzschuh, Ulrike
A1  - Pestryakova, Luidmila Agafyevna
A1  - Zimmermann, Heike Hildegard
A1  - Davydova, Paraskovya
A1  - Biskaborn, Boris
A1  - Shevtsova, Iuliia
A1  - Stoof-Leichsenring, Kathleen Rosemarie
T1  - Genetic and morphologic determination of diatom community composition in surface sediments from glacial and thermokarst lakes in the Siberian Arctic
JF  - Journal of paleolimnolog
N2  - Lakes cover large parts of the climatically sensitive Arctic landscape and respond rapidly to environmental change. Arctic lakes have different origins and include the predominant thermokarst lakes, which are small, young and highly dynamic, as well as large, old and stable glacial lakes. Freshwater diatoms dominate the primary producer community in these lakes and can be used to detect biotic responses to climate and environmental change. We used specific diatom metabarcoding on sedimentary DNA, combined with next-generation sequencing and diatom morphology, to assess diatom diversity in five glacial and 15 thermokarst lakes within the easternmost expanse of the Siberian treeline ecotone in Chukotka, Russia. We obtained 163 verified diatom sequence types and identified 176 diatom species morphologically. Although there were large differences in taxonomic assignment using the two approaches, they showed similar high abundances and diversity of Fragilariceae and Aulacoseiraceae. In particular, the genetic approach detected hidden within-lake variations of fragilarioids in glacial lakes and dominance of centric Aulacoseira species, whereas Lindavia ocellata was predominant using morphology. In thermokarst lakes, sequence types and valve counts also detected high diversity of Fragilariaceae, which followed the vegetation gradient along the treeline. Ordination analyses of the genetic data from glacial and thermokarst lakes suggest that concentrations of sulfate (SO42-), an indicator of the activity of sulfate-reducing microbes under anoxic conditions, and bicarbonate (HCO3-), which relates to surrounding vegetation, have a significant influence on diatom community composition. For thermokarst lakes, we also identified lake depth as an important variable, but SO42- best explains diatom diversity derived from genetic data, whereas HCO3- best explains the data from valve counts. Higher diatom diversity was detected in glacial lakes, most likely related to greater lake age and different edaphic settings, which gave rise to diversification and endemism. In contrast, small, dynamic thermokarst lakes are inhabited by stress-tolerant fragilarioids and are related to different vegetation types along the treeline ecotone. Our study demonstrated that genetic investigations of lake sediments can be used to interpret climate and environmental responses of diatoms. It also showed how lake type affects diatom diversity, and that such genetic analyses can be used to track diatom community changes under ongoing warming in the Arctic.
KW  - diatoms
KW  - diversity
KW  - glacial lakes
KW  - sedimentary DNA
KW  - Siberian arctic
KW  - thermokarst
Y1  - 2020
U6  - https://doi.org/10.1007/s10933-020-00133-1
SN  - 0921-2728
SN  - 1573-0417
VL  - 64
IS  - 3
SP  - 225
EP  - 242
PB  - Springer
CY  - Dordrecht
ER  - 
TY  - JOUR
A1  - Guzman, Diego A.
A1  - Samprogna Mohor, Guilherme
A1  - Mendiondo, Eduardo Mario
T1  - Multi-year index-based insurance for adapting Water Utility Companies to hydrological drought
BT  - case study of a water supply system of the Sao Paulo metropolitan region, Brazil
JF  - Water
N2  - The sustainability of water utility companies is threatened by non-stationary drivers, such as climate and anthropogenic changes. To cope with potential economic losses, instruments such as insurance are useful for planning scenarios and mitigating impacts, but data limitations and risk uncertainties affect premium estimation and, consequently, business sustainability. This research estimated the possible economic impacts of business interruption to the Sao Paulo Water Utility Company derived from hydrological drought and how this could be mitigated with an insurance scheme. Multi-year insurance (MYI) was proposed through a set of "change" drivers: the climate driver, through forcing the water evaluation and planning system (WEAP) hydrological tool; the anthropogenic driver, through water demand projections; and the economic driver, associated with recent water price policies adopted by the utility company during water scarcity periods. In our study case, the evaluated indices showed that MYI contracts that cover only longer droughts, regardless of the magnitude, offer better financial performance than contracts that cover all events (in terms of drought duration). Moreover, through MYI contracts, we demonstrate solvency for the insurance fund in the long term and an annual average actuarially fair premium close to the total expected revenue reduction.
KW  - multi-year insurance
KW  - climate change
KW  - hydrological drought
KW  - water
KW  - security and economy
Y1  - 2020
U6  - https://doi.org/10.3390/w12112954
SN  - 2073-4441
VL  - 12
IS  - 11
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Izgi, Gizem
A1  - Eken, Tuna
A1  - Gaebler, Peter
A1  - Eulenfeld, Tom
A1  - Taymaz, Tuncay
T1  - Crustal seismic attenuation parameters in the western region of the North Anatolian Fault Zone
JF  - Journal of geodynamics
N2  - Detailed knowledge of the crustal structure along the North Anatolian Fault Zone can help in understanding past and present tectonic processes in relation to the deformation history. To estimate the frequency-dependent crustal attenuation parameters beneath the western part of the North Anatolian Fault Zone we apply acoustic radiative transfer theory under the assumption of multiple isotropic scattering to generate synthetic seismogram envelopes. The inversion depends on finding an optimal fit between observed and synthetically computed coda wave envelopes in five frequency bands. 2-D lateral variation of intrinsic and scattering attenuation at various frequencies tends to three crustal blocks (i.e., Armutlu-Almacik, Istanbul-Zonguldak and Sakarya Zones) separated by the southern and northern branches of the western part of the North Anatolian Fault Zone. Overall, scattering attenuation appears to be dominant over intrinsic attenuation in the study area at lower frequencies. Relatively low attenuation properties are observed beneath the older Istanbul Zone whereas higher attenuation properties are found for the younger Sakarya Zone. The Armutlu Almacik Zone exhibits more complex lateral variations. Very high attenuation values towards the west characterize the area of the Kuzuluk Basin, a pull-apart basin formed under west-east extension. Our coda-derived moment magnitudes are similar to the local magnitude estimates that were previously calculated for the same earthquakes. For smaller earthquakes (M-L < 2.5), however, the relation between local and moment magnitudes appears to lose its coherency. This may stem from various reasons including the use of seismic data recorded in finite sampling interval, possible biases in local magnitude estimates of earthquake catalogues as well as biases due to wrong assumptions to consider anelastic attenuation terms.
Y1  - 2020
U6  - https://doi.org/10.1016/j.jog.2020.101694
SN  - 0264-3707
VL  - 134
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Reschke, Maria
A1  - Kröner, Igor
A1  - Laepple, Thomas
T1  - Testing the consistency of Holocene and Last Glacial Maximum spatial correlations in temperature proxy records
JF  - Journal of quaternary science : JQS
N2  - Holocene temperature proxy records are commonly used in quantitative synthesis and model-data comparisons. However, comparing correlations between time series from records collected in proximity to one another with the expected correlations based on climate model simulations indicates either regional or noisy climate signals in Holocene temperature proxy records. In this study, we evaluate the consistency of spatial correlations present in Holocene proxy records with those found in data from the Last Glacial Maximum (LGM). Specifically, we predict correlations expected in LGM proxy records if the only difference to Holocene correlations would be due to more time uncertainty and more climate variability in the LGM. We compare this simple prediction to the actual correlation structure in the LGM proxy records. We found that time series data of ice-core stable isotope records and planktonic foraminifera Mg/Ca ratios were consistent between the Holocene and LGM periods, while time series of Uk'37 proxy records were not as we found no correlation between nearby LGM records. Our results support the finding of highly regional or noisy marine proxy records in the compilation analysed here and suggest the need for further studies on the role of climate proxies and the processes of climate signal recording and preservation.
KW  - Holocene
KW  - LGM
KW  - spatial correlation
KW  - temperature
KW  - Uk'37
Y1  - 2020
U6  - https://doi.org/10.1002/jqs.3245
SN  - 0267-8179
SN  - 1099-1417
VL  - 36
IS  - 1
SP  - 20
EP  - 28
PB  - Wiley
CY  - New York
ER  - 
TY  - JOUR
A1  - Zimmermann, Heike Hildegard
A1  - Stoof-Leichsenring, Kathleen Rosemarie
A1  - Kruse, Stefan
A1  - Müller, Juliane
A1  - Stein, Ruediger
A1  - Tiedemann, Ralf
A1  - Herzschuh, Ulrike
T1  - Changes in the composition of marine and sea-ice diatoms derived from sedimentary ancient DNA of the eastern Fram Strait over the past 30 000 years
JF  - Ocean science
N2  - The Fram Strait is an area with a relatively low and irregular distribution of diatom microfossils in surface sediments, and thus microfossil records are scarce, rarely exceed the Holocene, and contain sparse information about past richness and taxonomic composition. These attributes make the Fram Strait an ideal study site to test the utility of sedimentary ancient DNA (sedaDNA) metabarcoding. Amplifying a short, partial rbcL marker from samples of sediment core MSM05/5-712-2 resulted in 95.7% of our sequences being assigned to diatoms across 18 different families, with 38.6% of them being resolved to species and 25.8% to genus level. Independent replicates show a high similarity of PCR products, especially in the oldest samples. Diatom sedaDNA richness is highest in the Late Weichselian and lowest in Mid- and Late Holocene samples. Taxonomic composition is dominated by cold-water and sea-ice-associated diatoms and suggests several reorganisations - after the Last Glacial Maximum, after the Younger Dryas, and after the Early and after the Mid-Holocene. Different sequences assigned to, amongst others, Chaetoceros socialis indicate the detectability of intra-specific diversity using sedaDNA. We detect no clear pattern between our diatom sedaDNA record and the previously published IP25 record of this core, although proportions of pennate diatoms increase with higher IP25 concentrations and proportions of Nitzschia cf. frigida exceeding 2% of the assemblage point towards past sea-ice presence.
Y1  - 2020
U6  - https://doi.org/10.5194/os-16-1017-2020
SN  - 1812-0784
VL  - 16
IS  - 5
SP  - 1017
EP  - 1032
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Montero-Lopez, Carolina
A1  - Hongn, Fernando D.
A1  - Lopez Steinmetz, Romina L.
A1  - Aramayo, Alejandro
A1  - Pingel, Heiko
A1  - Strecker, Manfred
A1  - Cottle, John
A1  - Bianchi, Carlos
T1  - Development of an incipient Paleogene topography between the present-day Eastern Andean Plateau (Puna) and the Eastern Cordillera, southern Central Andes, NW Argentina
JF  - Basin research / publ. in conjunction with the European Association of Geoscientists & Engineers and the International Association of Sedimentologists
N2  - The structural and topographic evolution of orogenic plateaus is an important research topic because of its impact on atmospheric circulation patterns, the amount and distribution of rainfall, and resulting changes in surface processes. The Puna region in the north-western Argentina (between 13 degrees S and 27 degrees S) is part of the Andean Plateau, which is the world's second largest orogenic plateau. In order to investigate the deformational events responsible for the initial growth of this part of the Andean plateau, we carried out structural and stratigraphic investigations within the present-day transition zone between the northern Puna and the adjacent Eastern Cordillera to the east. This transition zone is characterized by ubiquitous exposures of continental middle Eocene redbeds of the Casa Grande Formation. Our structural mapping, together with a sedimentological analysis of these units and their relationships with the adjacent mountain ranges, has revealed growth structures and unconformities that are indicative of syntectonic deposition. These findings support the notion that tectonic shortening in this part of the Central Andes was already active during the middle Paleogene, and that early Cenozoic deformation in the region that now constitutes the Puna occurred in a spatially irregular manner. The patterns of Paleogene deformation and uplift along the eastern margin of the present-day plateau correspond to an approximately north-south oriented swath of reactivated basement heterogeneities (i.e. zones of mechanical weakness) stemming from regional Paleozoic mountain building that may have led to local concentration of deformation belts.
KW  - Andean Plateau
KW  - Eastern Cordillera
KW  - Eocene deformation
KW  - growth structures
KW  - northern Puna
KW  - north-western Argentina
KW  - southern Central Andes
Y1  - 2020
U6  - https://doi.org/10.1111/bre.12510
SN  - 0950-091X
SN  - 1365-2117
VL  - 33
IS  - 2
SP  - 1194
EP  - 1217
PB  - Wiley-Blackwell
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Zhou, Renjie
A1  - Aitchison, Jonathan C.
A1  - Lokho, Kapesa
A1  - Sobel, Edward
A1  - Feng, Yuexing
A1  - Zhao, Jian-xin
T1  - Unroofing the Ladakh Batholith: constraints from autochthonous molasse of the Indus Basin, NW Himalaya
JF  - Journal of the Geological Society
N2  - The Indus Molasse records orogenic sedimentation associated with uplift and erosion of the southern margin of Asia in the course of ongoing India-Eurasia collision. Detailed field investigation clarifies the nature and extent of the depositional contact between this molasse and the underlying basement units. We report the first dataset on detrital zircon U-Pb ages, Hf isotopes and apatite U-Pb ages for the autochthonous molasse in the Indus Suture Zone. A latest Oligocene depositional age is proposed on the basis of the youngest detrital zircon U-Pb age peak and is consistent with published biostratigraphic data. Multiple provenance indicators suggest exclusively northerly derivation with no input from India in the lowermost parts of the section. The results provide constraints on the uplift and erosion history of the Ladakh Range following the initial India-Asia collision.
Y1  - 2020
U6  - https://doi.org/10.1144/jgs2019-188
SN  - 0016-7649
SN  - 2041-479X
VL  - 177
IS  - 4
SP  - 818
EP  - 825
PB  - Geological Society (London)
CY  - London
ER  - 
TY  - JOUR
A1  - Bahr, André
A1  - Kolber, Gilles
A1  - Kaboth-Bahr, Stefanie
A1  - Reinhardt, Lutz
A1  - Friedrich, Oliver
A1  - Pross, Jörg
T1  - Mega-monsoon variability during the late Triassic
BT  - re-assessing the role of orbital forcing in the deposition of playa sediments in the Germanic Basin
JF  - Sedimentology : the journal of the International Association of Sedimentologists
N2  - The formation of the supercontinent Pangaea during the Permo-Triassic gave rise to an extreme monsoonal climate (often termed 'mega-monsoon') that has been documented by numerous palaeo-records. However, considerable debate exists about the role of orbital forcing in causing humid intervals in an otherwise arid climate. To shed new light on the forcing of monsoonal variability in subtropical Pangaea, this study focuses on sediment facies and colour variability of playa and alluvial fan deposits in an outcrop from the late Carnian (ca 225 Ma) in the southern Germanic Basin, south-western Germany. The sediments were deposited against a background of increasingly arid conditions following the humid Carnian Pluvial Event (ca 234 to 232 Ma). The ca 2 center dot 4 Myr long sedimentary succession studied shows a tripartite long-term evolution, starting with a distal mud-flat facies deposited under arid conditions. This phase was followed by a highly variable playa-lake environment that documents more humid conditions and finally a regression of the playa-lake due to a return of arid conditions. The red-green (a*) and lightness (L*) records show that this long-term variability was overprinted by alternating wet/dry cycles driven by orbital precession and ca 405 kyr eccentricity, without significant influence of obliquity. The absence of obliquity in this record indicates that high-latitude forcing played only a minor role in the southern Germanic Basin during the late Carnian. This is different from the subsequent Norian when high-latitude signals became more pronounced, potentially related to the northward drift of the Germanic Basin. The recurring pattern of pluvial events during the late Triassic demonstrates that orbital forcing, in particular eccentricity, stimulated the occurrence and intensity of wet phases. It also highlights the possibility that the Carnian Pluvial Event, although most likely triggered by enhanced volcanic activity, may also have been modified by an orbital stimulus.
KW  - Carnian Pluvial Event
KW  - Germanic Basin
KW  - Late Triassic
KW  - mega-monsoon
KW  - orbital forcing
KW  - playa-lake
Y1  - 2019
U6  - https://doi.org/10.1111/sed.12668
SN  - 0037-0746
SN  - 1365-3091
VL  - 67
IS  - 2
SP  - 951
EP  - 970
PB  - Wiley-Blackwell
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Glerum, Anne
A1  - Brune, Sascha
A1  - Stamps, D. Sarah
A1  - Strecker, Manfred
T1  - Victoria continental microplate dynamics controlled by the lithospheric strength distribution of the East African Rift
JF  - Nature Communications
N2  - The Victoria microplate between the Eastern and Western Branches of the East African Rift System is one of the largest continental microplates on Earth. In striking contrast to its neighboring plates, Victoria rotates counterclockwise with respect to Nubia. The underlying cause of this distinctive rotation has remained elusive so far. Using 3D numerical models, we investigate the role of pre-existing lithospheric heterogeneities in continental microplate rotation. We find that Victoria's rotation is primarily controlled by the distribution of rheologically stronger zones that transmit the drag of the major plates to the microplate and of the mechanically weaker mobile belts surrounding Victoria that facilitate rotation. Our models reproduce Victoria's GPS-derived counterclockwise rotation as well as key complexities of the regional tectonic stress field. These results reconcile competing ideas on the opening of the rift system by highlighting differences in orientation of the far-field divergence, local extension, and the minimum horizontal stress. One of the largest continental microplates on Earth is situated in the center of the East African Rift System, and oddly, the Victoria microplate rotates counterclockwise with respect to the neighboring African tectonic plate. Here, the authors' modelling results suggest that Victoria microplate rotation is caused by edge-driven lithospheric processes related to the specific geometry of rheologically weak and strong regions.
Y1  - 2020
U6  - https://doi.org/10.1038/s41467-020-16176-x
SN  - 2041-1723
VL  - 11
IS  - 1
PB  - Nature Publishing Group
CY  - London
ER  - 
TY  - JOUR
A1  - Bentz, Stephan
A1  - Kwiatek, Grzegorz
A1  - Martinez-Garzon, Patricia
A1  - Bohnhoff, Marco
A1  - Dresen, Georg
T1  - Seismic moment evolution during hydraulic stimulations
JF  - Geophysical research letters
N2  - Analysis of past and present stimulation projects reveals that the temporal evolution and growth of maximum observed moment magnitudes may be linked directly to the injected fluid volume and hydraulic energy. Overall evolution of seismic moment seems independent of the tectonic stress regime and is most likely governed by reservoir specific parameters, such as the preexisting structural inventory. Data suggest that magnitudes can grow either in a stable way, indicating the constant propagation of self-arrested ruptures, or unbound, for which the maximum magnitude is only limited by the size of tectonic faults and fault connectivity. Transition between the two states may occur at any time during injection or not at all. Monitoring and traffic light systems used during stimulations need to account for the possibility of unstable rupture propagation from the very beginning of injection by observing the entire seismicity evolution in near-real time and at high resolution for an immediate reaction in injection strategy. 

Plain Language Summary Predicting and controlling the size of earthquakes caused by fluid injection is currently the major concern of many projects associated with geothermal energy production. Here, we analyze the magnitude and seismic moment evolution with injection parameters for prominent geothermal and scientific projects to date. Evolution of seismicity seems to be largely independent of the tectonic stress background and seemingly depends on reservoir specific characteristics. We find that the maximum observed magnitudes relate linearly to the injected volume or hydraulic energy. A linear relation suggests stable growth of induced ruptures, as predicted by current models, or rupture growth may no longer depend on the stimulated volume but on tectonics. A system may change between the two states during the course of fluid injection. Close-by and high-resolution monitoring of seismic and hydraulic parameters in near-real time may help identify these fundamental changes in ample time to change injection strategy and manage maximum magnitudes.
Y1  - 2020
U6  - https://doi.org/10.1029/2019GL086185
SN  - 0094-8276
SN  - 1944-8007
VL  - 47
IS  - 5
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Forbriger, Thomas
A1  - Gao, Lingli
A1  - Malischewsky, Peter
A1  - Ohrnberger, Matthias
A1  - Pan, Yudi
T1  - A single Rayleigh mode may exist with multiple values of phase-velocity at one frequency
JF  - Geophysical journal international
N2  - Other than commonly assumed in seismology, the phase velocity of Rayleigh waves is not necessarily a single-valued function of frequency. In fact, a single Rayleigh mode can exist with three different values of phase velocity at one frequency. We demonstrate this for the first higher mode on a realistic shallow seismic structure of a homogeneous layer of unconsolidated sediments on top of a half-space of solid rock (LOH). In the case of LOH a significant contrast to the half-space is required to produce the phenomenon. In a simpler structure of a homogeneous layer with fixed (rigid) bottom (LFB) the phenomenon exists for values of Poisson's ratio between 0.19 and 0.5 and is most pronounced for P-wave velocity being three times S-wave velocity (Poisson's ratio of 0.4375). A pavement-like structure (PAV) of two layers on top of a half-space produces the multivaluedness for the fundamental mode. Programs for the computation of synthetic dispersion curves are prone to trouble in such cases. Many of them use mode-follower algorithms which loose track of the dispersion curve and miss the multivalued section. We show results for well established programs. Their inability to properly handle these cases might be one reason why the phenomenon of multivaluedness went unnoticed in seismological Rayleigh wave research for so long. For the very same reason methods of dispersion analysis must fail if they imply wave number k(l)(omega) for the lth Rayleigh mode to be a single-valued function of frequency.. This applies in particular to deconvolution methods like phase-matched filters. We demonstrate that a slant-stack analysis fails in the multivalued section, while a Fourier-Bessel transformation captures the complete Rayleigh-wave signal. Waves of finite bandwidth in the multivalued section propagate with positive group-velocity and negative phase-velocity. Their eigenfunctions appear conventional and contain no conspicuous feature.
KW  - Surface waves and free oscillations
KW  - Theoretical seismology
KW  - Wave
KW  - propagation
Y1  - 2020
U6  - https://doi.org/10.1093/gji/ggaa123
SN  - 0956-540X
SN  - 1365-246X
VL  - 222
IS  - 1
SP  - 582
EP  - 594
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Menges, Johanna
A1  - Hovius, Niels
A1  - Andermann, Christoff
A1  - Lupker, Maarten
A1  - Haghipour, Negar
A1  - Märki, Lena
A1  - Sachse, Dirk
T1  - Variations in organic carbon sourcing along a trans-Himalayan river determined by a Bayesian mixing approach
JF  - Geochimica et cosmochimica acta : journal of the Geochemical Society and the Meteoritical Society
N2  - Rivers transfer particulate organic carbon (POC) from eroding mountains into geological sinks. Organic carbon source composition and selective mobilization have been shown to affect the type and quantity of POC export, but their combined effects across complex mountain ranges remain underexplored. Here, we examine the variation in organic carbon sourcing and transport in the trans-Himalayan Kali Gandaki River catchment, along strong gradients in precipitation, rock type and vegetation. Combining bulk stable nitrogen, and stable and radioactive organic carbon isotopic composition of bedrock, litter, soil and river sediment samples with a Bayesian end-member mixing approach, we differentiate POC sources along the river and quantify their export. Our analysis shows that POC export from the Tibetan segment of the catchment, where carbon bearing shales are partially covered by aged and modern soils, is dominated by petrogenic POC. Based on our data we re-assess the presence of aged biospheric OC in this part of the catchment, and its contribution to the river load. In the High Himalayan segment, we observed low inputs of petrogenic and biospheric POC, likely due to very low organic carbon concentrations in the metamorphic bedrock, combined with erosion dominated by deep-seated landslides. Our findings show that along the Kali Gandaki River, the sourcing of sediment and organic carbon are decoupled, due to differences in rock organic carbon content, soil and above ground carbon stocks, and geomorphic process activity. While the fast eroding High Himalayas are the principal source of river sediment, the Tibetan headwaters, where erosion rates are lower, are the principal source of organic carbon. To robustly estimate organic carbon export from the Himalayas, the mountain range should be divided into tectono-physiographic zones with distinct organic carbon yields due to differences in substrate and erosion processes and rates.
KW  - particulate organic carbon
KW  - Himalaya
KW  - rivers
KW  - carbon cycle
KW  - stable
KW  - isotopes
KW  - erosion
KW  - end-member mixing
Y1  - 2020
U6  - https://doi.org/10.1016/j.gca.2020.07.003
SN  - 0016-7037
VL  - 286
SP  - 159
EP  - 176
PB  - Elsevier
CY  - New York [u.a.]
ER  - 
TY  - JOUR
A1  - Obreht, Igor
A1  - Wörmer, Lars
A1  - Brauer, Achim
A1  - Wendt, Jenny
A1  - Alfken, Susanne
A1  - De Vleeschouwer, David
A1  - Elvert, Marcus
A1  - Hinrichs, Kai-Uwe
T1  - An annually resolved record of Western European vegetation response to Younger Dryas cooling
JF  - Quaternary science reviews : the international multidisciplinary research and review journal
N2  - The regional patterns and timing of the Younger Dryas cooling in the North Atlantic realm were complex and are mechanistically incompletely understood. To enhance understanding of regional climate patterns, we present molecular biomarker records at subannual to annual resolution by mass spectrometry imaging (MSI) of sediments from the Lake Meerfelder Maar covering the Allerod-Younger Dryas transition. These analyses are supported by conventional extraction-based molecular-isotopic analyses, which both validate the imaging results and constrain the sources of the target compounds. The targeted fatty acid biomarkers serve as a gauge of the response of the local aquatic and terrestrial ecosystem to climate change. Based on the comparison of our data with existing data from Meerfelder Maar, we analyse the short-term environmental evolution in Western Europe during the studied time interval and confirm the previously reported delayed hydrological response to Greenland cooling. However, despite a detected delay of Western European environmental change of similar to 135 years, our biomarker data show statistically significant correlation with deuterium excess in Greenland ice core at - annual resolution during this time-transgressive cooling. This suggests a coherent atmospheric forcing across the North Atlantic realm during this transition. We propose that Western European cooling was postponed due to major reorganization of the westerlies that were intermittently forcing warmer and wetter air masses from lower latitudes to Western Europe and thus resulted in delayed cooling relative to Greenland.
KW  - lateglacial
KW  - paleoclimatology
KW  - Western Europe
KW  - Meerfelder Maar
KW  - high-resolution biomarkers
KW  - fatty acids
KW  - FT-ICR-MS
KW  - mass spectrometry
KW  - imaging
Y1  - 2020
U6  - https://doi.org/10.1016/j.quascirev.2020.106198
SN  - 0277-3791
VL  - 231
PB  - Elsevier
CY  - Amsterdam [u.a.]
ER  - 
TY  - JOUR
A1  - Krmíček, Lukáš
A1  - Timmerman, Martin Jan
A1  - Ziemann, Martin Andreas
A1  - Sudo, Masafumi
A1  - Ulrych, Jaromir
T1  - 40Ar/39Ar step-heating dating of phlogopite and kaersutite megacrysts from the Železná hůrka (Eisenbühl) Pleistocene scoria cone, Czech Republic
JF  - Geologica Carpathica
N2  - (40)A/Ar-39 step-heating of mica and amphibole megacrysts from hauyne-bearing olivine melilitite scoria/tephra from the Zelezna hurka yielded a 435 +/- 108 ka isotope correlation age for phlogopite and a more imprecise 1.55 Ma total gas age of the kaersutite megacryst. The amphibole megacrysts may constitute the first, and the younger phlogopite megacrysts the later phase of mafic, hydrous melilitic magma crystallization. It cannot be ruled out that the amphibole megacrysts are petrogenetically unrelated to tephra and phlogopite megacrysts and were derived from mantle xenoliths or disaggregated older, deep crustal pegmatites. This is in line both with the rarity of amphibole at Zelezna hurka and with the observed signs of magmatic resorption at the edges of amphibole crystals.
KW  - Bohemian Massif
KW  - Zelezna hurka
KW  - Eisenbuhl
KW  - argon dating
KW  - mica
KW  - amphibole
KW  - melilitite
Y1  - 2020
U6  - https://doi.org/10.31577/GeolCarp.71.4.6
SN  - 1335-0552
SN  - 1336-8052
VL  - 71
IS  - 4
SP  - 382
EP  - 387
PB  - Veda
CY  - Bratislava
ER  - 
TY  - JOUR
A1  - Rybski, Diego
A1  - Dawson, Richard J.
A1  - Kropp, Jürgen
T1  - Comparing generic and case study damage functions
BT  - London storm-surge example
JF  - Natural hazards review
N2  - Two different approaches are used to assess the impacts associated with natural hazards and climate change in cities. A bottom-up approach uses high resolution data on constituent assets within the urban area. In contrast, a top-down approach uses less detailed information but is consequently more readily transferable. Here, we compare damage curves generated by each approach for coastal flooding in London. To compare them, we fit a log-logistic regression with three parameters to the calculated damage curves. We find that the functions are remarkably similar in their shape, albeit with different inflection points and a maximum damage that differs by 13%-25%. If rescaled, the curves agree almost exactly, which enables damage assessment to be undertaken following the calculation of the three parameters.
Y1  - 2020
U6  - https://doi.org/10.1061/(ASCE)NH.1527-6996.0000336
SN  - 1527-6988
SN  - 1527-6996
VL  - 21
IS  - 1
PB  - American Society of Civil Engineers
CY  - Reston
ER  - 
TY  - JOUR
A1  - Baes, Marzieh
A1  - Sobolev, Stephan
A1  - Gerya, Taras V.
A1  - Brune, Sascha
T1  - Plume-induced subduction initiation
BT  - single-slab or multi-slab subduction?
JF  - Geochemistry, geophysics, geosystems
N2  - Initiation of subduction following the impingement of a hot buoyant mantle plume is one of the few scenarios that allow breaking the lithosphere and recycling a stagnant lid without requiring any preexisting weak zones. Here, we investigate factors controlling the number and shape of retreating subducting slabs formed by plume-lithosphere interaction. Using 3-D thermomechanical models we show that the deformation regime, which defines formation of single-slab or multi-slab subduction, depends on several parameters such as age of oceanic lithosphere, thickness of the crust and large-scale lithospheric extension rate. Our model results indicate that on present-day Earth multi-slab plume-induced subduction is initiated only if the oceanic lithosphere is relatively young (<30-40 Myr, but >10 Myr), and the crust has a typical thickness of 8 km. In turn, development of single-slab subduction is facilitated by older lithosphere and pre-imposed extensional stresses. In early Earth, plume-lithosphere interaction could have led to formation of either episodic short-lived circular subduction when the oceanic lithosphere was young or to multi-slab subduction when the lithosphere was old.
KW  - subduction zone
KW  - plume
KW  - numerical model
KW  - singleslab
KW  - multi-slab
Y1  - 2020
U6  - https://doi.org/10.1029/2019GC008663
SN  - 1525-2027
VL  - 21
IS  - 2
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Liu, Qi
A1  - Adler, Karsten
A1  - Lipus, Daniel
A1  - Kämpf, Horst
A1  - Bussert, Robert
A1  - Plessen, Birgit
A1  - Schulz, Hans-Martin
A1  - Krauze, Patryk
A1  - Horn, Fabian
A1  - Wagner, Dirk
A1  - Mangelsdorf, Kai
A1  - Alawi, Mashal
T1  - Microbial signatures in deep CO2-saturated miocene sediments of the active Hartousov mofette system (NW Czech Republic)
JF  - Frontiers in microbiology
N2  - The Hartousov mofette system is a natural CO2 degassing site in the central Cheb Basin (Eger Rift, Central Europe). In early 2016 a 108 m deep core was obtained from this system to investigate the impact of ascending mantle-derived CO2 on indigenous deep microbial communities and their surrounding life habitat. During drilling, a CO2 blow out occurred at a depth of 78.5 meter below surface (mbs) suggesting a CO2 reservoir associated with a deep low-permeable CO2-saturated saline aquifer at the transition from Early Miocene terrestrial to lacustrine sediments. Past microbial communities were investigated by hopanoids and glycerol dialkyl glycerol tetraethers (GDGTs) reflecting the environmental conditions during the time of deposition rather than showing a signal of the current deep biosphere. The composition and distribution of the deep microbial community potentially stimulated by the upward migration of CO2 starting during Mid Pleistocene time was investigated by intact polar lipids (IPLs), quantitative polymerase chain reaction (qPCR), and deoxyribonucleic acid (DNA) analysis. The deep biosphere is characterized by microorganisms that are linked to the distribution and migration of the ascending CO2-saturated groundwater and the availability of organic matter instead of being linked to single lithological units of the investigated rock profile. Our findings revealed high relative abundances of common soil and water bacteria, in particular the facultative, anaerobic and potential iron-oxidizing Acidovorax and other members of the family Comamonadaceae across the whole recovered core. The results also highlighted the frequent detection of the putative sulfate-oxidizing and CO2-fixating genus Sulfuricurvum at certain depths. A set of new IPLs are suggested to be indicative for microorganisms associated to CO2 accumulation in the mofette system.
KW  - geo-bio interaction
KW  - CO2
KW  - mofette systems
KW  - Eger Rift
KW  - microbial lipid
KW  - biomarker
KW  - microbial diversity
KW  - deep biosphere
KW  - saline groundwater
Y1  - 2020
U6  - https://doi.org/10.3389/fmicb.2020.543260
SN  - 1664-302X
VL  - 11
PB  - Frontiers Media
CY  - Lausanne
ER  - 
TY  - JOUR
A1  - Mogrovejo Arias, Diana Carolina
A1  - Brill, Florian H. H.
A1  - Wagner, Dirk
T1  - Potentially pathogenic bacteria isolated from diverse habitats in Spitsbergen, Svalbard
JF  - Environmental earth sciences
N2  - The Arctic ecosystem, a reservoir of genetic microbial diversity, represents a virtually unlimited source of microorganisms that could interact with human beings. Despite continuous exploration of Arctic habitats and description of their microbial communities, bacterial phenotypes commonly associated with pathogenicity, such as hemolytic activity, have rarely been reported. In this study, samples of snow, fresh and marine water, soil, and sediment from several habitats in the Arctic archipelago of Svalbard were collected during Summer, 2017. Bacterial isolates were obtained after incubation on oligotrophic media at different temperatures and their hemolytic potential was assessed on sheep blood agar plates. Partial (alpha) or true (beta) hemolysis was observed in 32 out of 78 bacterial species. Genes expressing cytolytic compounds, such as hemolysins, likely increase the general fitness of the producing microorganisms and confer a competitive advantage over the availability of nutrients in natural habitats. In environmental species, the nutrient-acquisition function of these compounds presumably precedes their function as toxins for mammalian erythrocytes. However, in the light of global warming, the presence of hemolytic bacteria in Arctic environments highlights the possible risks associated with these microorganisms in the event of habitat melting/destruction, ecosystem transition, and re-colonization.
KW  - Arctic
KW  - Svalbard
KW  - hemolysins
KW  - climate change
KW  - pathogens
KW  - virulence
Y1  - 2020
U6  - https://doi.org/10.1007/s12665-020-8853-4
SN  - 1866-6280
SN  - 1866-6299
VL  - 79
IS  - 5
PB  - Springer
CY  - Berlin ; Heidelberg
ER  - 
TY  - JOUR
A1  - Niemz, Peter
A1  - Cesca, Simone
A1  - Heimann, Sebastian
A1  - Grigoli, Francesco
A1  - von Specht, Sebastian
A1  - Hammer, Conny
A1  - Zang, Arno
A1  - Dahm, Torsten
T1  - Full-waveform-based characterization of acoustic emission activity in a mine-scale experiment
BT  - a comparison of conventional and advanced hydraulic fracturing schemes
JF  - Geophysical journal international / the Royal Astronomical Society, the Deutsche Geophysikalische Gesellschaft and the European Geophysical Society
N2  - Understanding fracturing processes and the hydromechanical relation to induced seismicity is a key question for enhanced geothermal systems (EGS). Commonly massive fluid injection, predominately causing hydroshearing, are used in large-scale EGS but also hydraulic fracturing approaches were discussed. To evaluate the applicability of hydraulic fracturing techniques in EGS, six in situ, multistage hydraulic fracturing experiments with three different injection schemes were performed under controlled conditions in crystalline rock at the Aspo Hard Rock Laboratory (Sweden). During the experiments the near-field ground motion was continuously recorded by 11 piezoelectric borehole sensors with a sampling rate of 1 MHz. The sensor network covered a volume of 30x30x30 m around a horizontal, 28-m-long injection borehole at a depth of 410 m. To extract and characterize massive, induced, high-frequency acoustic emission (AE) activity from continuous recordings, a semi-automated workflow was developed relying on full waveform based detection, classification and location procedures. The approach extended the AE catalogue from 196 triggered events in previous studies to more than 19600 located AEs. The enhanced catalogue, for the first time, allows a detailed analysis of induced seismicity during single hydraulic fracturing experiments, including the individual fracturing stages and the comparison between injection schemes. Beside the detailed study of the spatio-temporal patterns, event clusters and the growth of seismic clouds, we estimate relative magnitudes and b-values of AEs for conventional, cyclic progressive and dynamic pulse injection schemes, the latter two being fatigue hydraulic fracturing techniques. While the conventional fracturing leads to AE patterns clustered in planar regions, indicating the generation of a single main fracture plane, the cyclic progressive injection scheme results in a more diffuse, cloud-like AE distribution, indicating the activation of a more complex fracture network. For a given amount of hydraulic energy (pressure multiplied by injected volume) pumped into the system, the cyclic progressive scheme is characterized by a lower rate of seismicity, lower maximum magnitudes and significantly larger b-values, implying an increased number of small events relative to the large ones. To our knowledge, this is the first direct comparison of high resolution seismicity in a mine-scale experiment induced by different hydraulic fracturing schemes.
KW  - Fracture and flow
KW  - Spatial analysis
KW  - Statistical methods
KW  - Time-series analysis
KW  - Induced seismicity
Y1  - 2020
U6  - https://doi.org/10.1093/gji/ggaa127
SN  - 0955-419X
SN  - 1365-246X
VL  - 222
IS  - 1
SP  - 189
EP  - 206
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Wang, Lei
A1  - Dresen, Georg
A1  - Rybacki, Erik
A1  - Bonnelye, Audrey
A1  - Bohnhoff, Marco
T1  - Pressure-dependent bulk compressibility of a porous granular material modeled by improved contact mechanics and micromechanical approaches
BT  - effects of surface roughness of grains
JF  - Acta materialia
N2  - The change of the mechanical properties of granular materials with pressure is an important topic associated with many industrial applications. In this paper we investigate the influence of hydrostatic pressure (P-e) on the effective bulk compressibility (C-eff) of a granular material by applying two modified theoretical approaches that are based on contact mechanics and micromechanics, respectively. For a granular material composed of rough grains, an extended contact model is developed to elucidate the effect of roughness of grain surfaces on bulk compressibility. At relatively low pressures, the model predicts that the decrease of bulk compressibility with pressure may be described by a power law with an exponent of -1/2 (i.e., C-eff proportional to P-e(1/2) ), but deviates at intermediate pressures. At elevated pressures beyond full contact, bulk compressibility remains almost unchanged, which may be roughly evaluated by continuum contact mechanics. As an alternative explanation of pressure-dependent bulk compressibility, we suggest a micromechanical model that accounts for effects of different types of pore space present in granular materials. Narrow and compliant inter-granular cracks are approximated by three-dimensional oblate spheroidal cracks with rough surfaces, whereas the equant and stiff pores surrounded by three and four neighboring grains are modeled as tubular pores with cross sections of three and four cusp-like corners, respectively. In this model, bulk compressibility is strongly reduced with increasing pressure by progressive closure of rough-walled cracks. At pressures exceeding crack closure pressure, deformation of the remaining equant pores is largely insensitive to pressure, with almost no further change in bulk compressibility. To validate these models, we performed hydrostatic compression tests on Bentheim sandstone (a granular rock consisting of quartz with high porosity) under a wide range of pressure. The relation between observed microstructures and measured pressure-dependent bulk compressibility is well explained by both suggested models.
KW  - Bulk compressibility
KW  - Granular materials
KW  - Roughness
KW  - Micromechanical model
KW  - Contact model
Y1  - 2020
U6  - https://doi.org/10.1016/j.actamat.2020.01.063
SN  - 1359-6454
SN  - 1873-2453
VL  - 188
SP  - 259
EP  - 272
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Pradhan, Prajal
A1  - Kriewald, Steffen
A1  - Costa, Luís Fílípe Carvalho da
A1  - Rybski, Diego
A1  - Benton, Tim G.
A1  - Fischer, Günther
A1  - Kropp, Jürgen
T1  - Urban food systems: how regionalization can contribute to climate change mitigation
JF  - Environmental science & technology
N2  - Cities will play a key role in the grand challenge of nourishing a growing global population, because, due to their population density, they set the demand. To ensure that food systems are sustainable, as well as nourishing, one solution often suggested is to shorten their supply chains toward a regional rather than a global basis. While such regional systems may have a range of costs and benefits, we investigate the mitigation potential of regionalized urban food systems by examining the greenhouse gas emissions associated with food transport. Using data on food consumption for 7108 urban administrative units (UAUs), we simulate total transport emissions for both regionalized and globalized supply chains. In regionalized systems, the UAUs' demands are fulfilled by peripheral food production, whereas to simulate global supply chains, food demand is met from an international pool (where the origin can be any location globally). We estimate that regionalized systems could reduce current emissions from food transport. However, because longer supply chains benefit from maximizing comparative advantage, this emission reduction would require closing yield gaps, reducing food waste, shifting toward diversified farming, and consuming seasonal produce. Regionalization of food systems will be an essential component to limit global warming to well below 2 degrees C in the future.
Y1  - 2020
U6  - https://doi.org/10.1021/acs.est.0c02739
SN  - 0013-936X
SN  - 1520-5851
VL  - 54
IS  - 17
SP  - 10551
EP  - 10560
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Schönfeldt, Elisabeth
A1  - Pánek, Tomáš
A1  - Winocur, Diego
A1  - Silhan, Karel
A1  - Korup, Oliver
T1  - Postglacial Patagonian mass movement
BT  - from rotational slides and spreads to earthflows
JF  - Geomorphology : an international journal on pure and applied geomorphology
N2  - Many of the volcanic plateau margins of the eastern, formerly glaciated, foreland of the Patagonian Andes are undermined by giant landslides (>= 10(8) m(3)). One cluster of such landslides extends along the margin of the Meseta del Lago Buenos Aires (MLBA) plateau that is formed mainly by Neogene-Quaternary basalts. The dry climate is at odds with numerous >2-km long earthflows nested within older and larger compound landslides. We present a hydrological analysis, a detailed geomorphic map, interpretations of exposed landslide interiors, and radiocarbon dating of the El Mirador landslide, which is one of the largest and morphologically most representative landslide. We find that the presence of lakes on top of the plateau, causing low infiltration rates, correlates negatively with the abundance of earthflows on compound landslides along the plateau margins. Field outcrops show that the pattern of compound landslides and earthflows is likely controlled by groundwater seepage at the contact between the basalts and underlying soft Miocene molasse. Numerous peat bogs store water and sediment and are more abundant in earthflow-affected areas than in their contributing catchment areas. <br /> Radiocarbon dates indicate that these earthflows displaced metre-thick layers of peat in the late Holocene (<2.5 ka). We conclude that earthflows of the MLBA plateau might be promising proxies of past hydroclimatic conditions in the Patagonian foreland, if strong earthquakes or gradual crustal stress changes due to glacioisostatic rebound can be ruled out.
KW  - landslide
KW  - lateral spread
KW  - earthflow
KW  - Patagonia
Y1  - 2020
U6  - https://doi.org/10.1016/j.geomorph.2020.107316
SN  - 0169-555X
SN  - 1872-695X
VL  - 367
PB  - Elsevier
CY  - Amsterdam
ER  -