TY - JOUR A1 - Soumaya, Abdelkader A1 - Ben Ayed, Noureddine A1 - Rajabi, Mojtaba A1 - Meghraoui, Mustapha A1 - Delvaux, Damien A1 - Kadri, Ali A1 - Ziegler, Moritz A1 - Maouche, Said A1 - Braham, Ahmed T1 - Active Faulting Geometry and Stress Pattern Near Complex Strike-Slip Systems Along the Maghreb Region BT - Constraints on Active Convergence in the Western Mediterranean JF - Tectonics N2 - The Maghreb region (from Tunisia to Gibraltar) is a key area in the western Mediterranean to study the active tectonics and stress pattern across the Africa-Eurasia convergent plate boundary. In the present study, we compile comprehensive data set of well-constrained crustal stress indicators (from single focal mechanism solutions, formal inversion of focal mechanism solutions, and young geologic fault slip data) based on our and published data analyses. Stress inversion of focal mechanisms reveals a first-order transpression-compatible stress field and a second-order spatial variation of tectonic regime across the Maghreb region, with a relatively stable S-Hmax orientation from east to west. Therefore, the present-day active contraction of the western Africa-Eurasia plate boundary is accommodated by (1) E-W strike-slip faulting with reverse component along the Eastern Tell and Saharan-Tunisian Atlas, (2) a predominantly NE trending thrust faulting with strike-slip component in the Western Tell part, and (3) a conjugate strike-slip faulting regime with normal component in the Alboran/Rif domain. This spatial variation of the present-day stress field and faulting regime is relatively in agreement with the inferred stress information from neotectonic features. According to existing and newly proposed structural models, we highlight the role of main geometrically complex shear zones in the present-day stress pattern of the Maghreb region. Then, different geometries of these major inherited strike-slip faults and its related fractures (V-shaped conjugate fractures, horsetail splays faults, and Riedel fractures) impose their component on the second- and third-order stress regimes. Neotectonic and smoothed present-day stress map (mean S-Hmax orientation) reveal that plate boundary forces acting on the Africa-Eurasia collisional plates control the long wavelength of the stress field pattern in the Maghreb. The current tectonic deformations and the upper crustal stress field in the study area are governed by the interplay of the oblique plate convergence (i.e., Africa-Eurasia), lithosphere-mantle interaction, and preexisting tectonic weakness zones. KW - Maghreb KW - strike-slip system KW - conjugate fractures KW - horsetail splays KW - active stress KW - tectonic regime Y1 - 2018 U6 - https://doi.org/10.1029/2018TC004983 SN - 0278-7407 SN - 1944-9194 VL - 37 IS - 9 SP - 3148 EP - 3173 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Graf, Lukas A1 - Moreno-de-las-Heras, Mariano A1 - Ruiz, Maurici A1 - Calsamiglia, Aleix A1 - García-Comendador, Julián A1 - Fortesa, Josep A1 - López-Tarazón, José A. A1 - Estrany, Joan T1 - Accuracy assessment of digital terrain model dataset sources for hydrogeomorphological modelling in small mediterranean catchments JF - Remote sensing N2 - Digital terrain models (DTMs) are a fundamental source of information in Earth sciences. DTM-based studies, however, can contain remarkable biases if limitations and inaccuracies in these models are disregarded. In this work, four freely available datasets, including Shuttle Radar Topography Mission C-Band Synthetic Aperture Radar (SRTM C-SAR V3 DEM), Advanced Spaceborne Thermal Emission and Reflection Radiometer Global Digital Elevation Map (ASTER GDEM V2), and two nationwide airborne light detection and ranging (LiDAR)-derived DTMs (at 5-m and 1-m spatial resolution, respectively) were analysed in three geomorphologically contrasting, small (3–5 km2) catchments located in Mediterranean landscapes under intensive human influence (Mallorca Island, Spain). Vertical accuracy as well as the influence of each dataset’s characteristics on hydrological and geomorphological modelling applicability were assessed by using ground-truth data, classic geometric and morphometric parameters, and a recently proposed index of sediment connectivity. Overall vertical accuracy—expressed as the root mean squared error (RMSE) and normalised median deviation (NMAD)—revealed the highest accuracy for the 1-m (RMSE = 1.55 m; NMAD = 0.44 m) and 5-m LiDAR DTMs (RMSE = 1.73 m; NMAD = 0.84 m). Vertical accuracy of the SRTM data was lower (RMSE = 6.98 m; NMAD = 5.27 m), but considerably higher than for the ASTER data (RMSE = 16.10 m; NMAD = 11.23 m). All datasets were affected by systematic distortions. Propagation of these errors and coarse horizontal resolution caused negative impacts on flow routing, stream network, and catchment delineation, and to a lower extent, on the distribution of slope values. These limitations should be carefully considered when applying DTMs for catchment hydrogeomorphological modelling. KW - digital terrain models KW - DTM vertical accuracy KW - DTM comparison KW - hydrogeomorphological modelling KW - Mediterranean catchments Y1 - 2018 U6 - https://doi.org/10.3390/rs10122014 SN - 2072-4292 VL - 10 IS - 12 PB - MDPI CY - Basel ER - TY - JOUR A1 - Kutzschbach, Martin A1 - Guttmann, Peter A1 - Marquardt, K. A1 - Werner, S. A1 - Henzler, K. D. A1 - Wilke, Max T1 - A transmission x-ray microscopy and NEXAFS approach for studying corroded silicate glasses at the nanometre scale JF - European journal of glass science and technology / Deutsche Glastechnische Gesellschaft (DGG) and the Society of Glass Technology (SGT). B, Physics and chemistry of glasses N2 - In this study transmission X-ray microscopy (TXM) was tested as a method to investigate the chemistry and structure of corroded silicate glasses at the nanometer scale. Three different silicate glasses were altered in static corrosion experiments for 1-336 hours at temperatures between 60 degrees C and 85 degrees C using a 25% HCl solution. Thin lamellas were cut perpendicular to the surface of corroded glass monoliths and were analysed with conventional TEM as well as with TXM. By recording optical density profiles at photon energies around the Na and O K-edges, the shape of the corrosion rim/pristine glass interfaces and the thickness of the corrosion rims has been determined. Na and O near-edge X-ray absorption fine-structure spectra (NEXAFS) were obtained without inducing irradiation damage and have been used to detect chemical changes in the corrosion rims. Spatially resolved NEXAFS spectra at the O K-edge provided insight to structural changes in the corrosion layer on the atomic scale. By comparison to O K-edge spectra of silicate minerals and (hydrous) albite glass as well as to O K-edge NEXAFS of model structures simulated with ab initio calculations, evidence is provided that changes of the fine structure at the O K-edge are assigned to the formation of siloxane groups in the corrosion rim. Y1 - 2018 U6 - https://doi.org/10.13036/17533562.59.1.043 SN - 1753-3562 VL - 59 IS - 1 SP - 11 EP - 26 PB - Society of Glass Technology CY - Sheffield ER - TY - JOUR A1 - Dommain, René A1 - Frolking, Steve A1 - Jeltsch-Thömmes, Aurich A1 - Joos, Fortunat Ulrich A1 - Couwenberg, John A1 - Glaser, Paul H. T1 - A radiative forcing analysis of tropical peatlands before and after their conversion to agricultural plantations JF - Global change biology N2 - The tropical peat swamp forests of South-East Asia are being rapidly converted to agricultural plantations of oil palm and Acacia creating a significant global “hot-spot” for CO2 emissions. However, the effect of this major perturbation has yet to be quantified in terms of global warming potential (GWP) and the Earth's radiative budget. We used a GWP analysis and an impulse-response model of radiative forcing to quantify the climate forcing of this shift from a long-term carbon sink to a net source of greenhouse gases (CO2 and CH4). In the GWP analysis, five tropical peatlands were sinks in terms of their CO2 equivalent fluxes while they remained undisturbed. However, their drainage and conversion to oil palm and Acacia plantations produced a dramatic shift to very strong net CO2-equivalent sources. The induced losses of peat carbon are ~20× greater than the natural CO2 sequestration rates. In contrast, a radiative forcing model indicates that the magnitude of this shift from a net cooling to warming effect is ultimately related to the size of an individual peatland's carbon pool. The continuous accumulation of carbon in pristine tropical peatlands produced a progressively negative radiative forcing (i.e., cooling) that ranged from −2.1 to −6.7 nW/m2 per hectare peatland by 2010 CE, referenced to zero at the time of peat initiation. Peatland conversion to plantations leads to an immediate shift from negative to positive trend in radiative forcing (i.e., warming). If drainage persists, peak warming ranges from +3.3 to +8.7 nW/m2 per hectare of drained peatland. More importantly, this net warming impact on the Earth's radiation budget will persist for centuries to millennia after all the peat has been oxidized to CO2. This previously unreported and undesirable impact on the Earth's radiative balance provides a scientific rationale for conserving tropical peatlands in their pristine state. KW - Acacia plantation KW - CO2 emissions KW - drainage-based land use KW - global warming potential KW - oil palm plantation KW - radiative forcing KW - tropical peatland Y1 - 2018 U6 - https://doi.org/10.1111/gcb.14400 SN - 1354-1013 SN - 1365-2486 VL - 24 IS - 11 SP - 5518 EP - 5533 PB - Wiley CY - Hoboken ER -