ALBERT

Description: In the race against time, the European Union must move swiftly to navigate the green transition. This imperative isn't just about staying ahead in the global green technology competition; it is about securing the future of Europe's economy while combating climate change. Ahead of the EU elections looming, the urgency of this dual challenge cannot be overstated. With a new pro-EU Polish government in place, the Weimar Triangle - a trilateral forum that brings together Poland, France and Germany - could provide the ideal place to offer a new bold industrial policy leadership in Europe.

Description: Global coupled climate models are in continuous need for evaluation against independent observations to reveal systematic model deficits and uncertainties. Changes in terrestrial water storage (TWS) as measured by satellite gravimetry missions GRACE and GRACE-FO provide valuable information on wetting and drying trends over the continents. Challenges arising from a comparison of observed and modelled water storage trends are related to gravity observations including non-water related variations such as, for example, glacial isostatic adjustment (GIA). Therefore, correcting secular changes in the Earth's gravity field caused by ongoing GIA is important for the monitoring of long-term changes in terrestrial water from GRACE in particular in former ice-covered regions. By utilizing a new ensemble of 56 individual realizations of GIA signals based on perturbations of mantle viscosities and ice history, we find that many of those alternative GIA corrections change the direction of GRACE-derived water storage trends, for example, from gaining mass into drying conditions, in particular in Eastern Canada. The change in the sign of the TWS trends subsequently impacts the conclusions drawn from using GRACE as observational basis for the evaluation of climate models as it influences the dis-/agreement between observed and modelled wetting/drying trends. A modified GIA correction, a combined GRACE/GRACE-FO data record extending over two decades, and a new generation of climate model experiments leads to substantially larger continental areas where wetting/drying trends currently observed by satellite missions coincide with long-term predictions obtained from climate model experiments.

Description: Although many collisional orogens form after subduction of oceanic lithosphere between two continents, some orogens result from strain localization within a continent via inversion of structures inherited from continental rifting. Intracontinental rift-inversion orogens exhibit a range of structural styles, but the underlying causes of such variability have not been extensively explored. We use numerical models of intracontinental rift inversion to investigate the impact of parameters including rift structure, rift duration, post-rift cooling, and convergence velocity on orogen structure. Our models reproduce the natural variability of rift-inversion orogens and can be categorized using three endmember styles: asymmetric underthrusting (AU), distributed thickening (DT), and localized polarity flip (PF). Inversion of narrow rifts tends to produce orogens with more localized deformation (styles AU and PF) than those resulting from wide rifts. However, multiple combinations of the parameters we investigated can produce the same structural style. Thus, our models indicate no unique relationship between orogenic structure and the conditions prior to and during inversion. Because the style of rift-inversion orogenesis is highly contingent upon the rift history prior to inversion, knowing the geologic history that preceded rift inversion is essential for translating orogenic structure into the processes that produced that structure.

Description: The investigation of key minerals including zircon, apatite, titanite, rutile, monazite, xenotime, allanite, baddeleyite and garnet can retain critical information about petrogenetic and geodynamic processes and may be utilized to understand complex geological histories and the dynamic evolution of the continental crust. They act as small but often robust petrochronological capsules and provide information about crustal evolution, from local processes to plate tectonics and supercontinent cycles. They offer us insights into processes of magmatism, sedimentation, metamorphism and alteration, even when the original protolith is not preserved. In situ techniques have enabled a more in-depth understanding of trace element behaviour in these minerals within their textural context. This has led to more meaningful ages for many stages of geological events. New developments of analytical procedures have further allowed us to expand our petrochronological toolbox while improving precision and accuracy. Combining multiple proxies with multiple minerals has contributed to new interpretations of the crustal history of our planet.

Description: GPS satellite observations indicate that in the tectonically complex eastern Mediterranean and east African regions microplates rotate counterclockwise with respect to the neighboring African plate. Using 3D numerical models, Glerum relates these observations of crustal deformation to the dynamics of the lithosphere and the underlying mantle that may cause this deformation. Glerum first describes her additions to the ASPECT software necessary for numerically modeling the upper mantle and lithosphere dynamics of convergent and divergent plate boundaries. These additions include the tracking of multiple materials with different physical properties and nonlinear viscous as well as viscoplastic rheologies. The implementations of complex, multi-material rheologies are verified with well-known 2D benchmarks and multi-material viscoplasticity is applied in 3D time-dependent thermomechanical models of oceanic subduction. Subsequently, Glerum uses ASPECT to investigate the sensitivity of horizontal surface motions to individual geodynamic processes in the eastern Mediterranean. Identification of all mantle drivers that should participate in modeling attempts to explain observations of crustal flow is essential to fully exploit the information contained by surface motions about their driving processes. Glerum therefore employs 3D data-driven instantaneous dynamics models of compressible flow including a complete set of possible mantle drivers of surface deformation. The reference instantaneous flow model results indicate that mantle processes can explain a large part of the crustal motion of the Aegean-Anatolian microplate. Subsequent systematic perturbations of model properties with respect to this reference model help estimate the individual contributions of tectonic plate motions, slab pull and trench suction, and density-induced mantle flow interacting with the slab and overlying plates while moderated by the mantle’s bulk viscosity. In order of regional importance, the predicted crustal flow of the Aegean-Anatolian region is most sensitive to slab pull, followed by slab-mantle interaction and basal drag, mantle rheology, and the absolute plate motion reference frame. Lastly, Glerum demonstrates a possible mechanism for the counterclockwise rotation of the Victoria microplate in the East African Rift System, which is in striking contrast to the clockwise motion of the surrounding plates. 3D models of the divergent system show that Victoria’s rotation can be caused by the drag of the African and Somalian plates along the strong edges of the microplate, while the rift segments along inherited lithospheric weaknesses facilitate Victoria’s rotation. The amount of rotation is therefore primarily controlled by the distribution of preexisting stronger regions and the weaker Precambrian mobile belts that surround Victoria. The induced counterclockwise rotation of the microplate leads to a clockwise shift of the local extension direction from E-W to more WNW-ESE along the overlapping rift branches. Comparison of the resulting predicted stress field and tectonic regimes to observations helps to elucidate the interpretation of local stress and strain indicators and to reconcile different opening models used to interpret the East African Rift System.

Description: Silicon isotope fractionation during silicification is poorly understood and impedes our ability to decipher paleoenvironmental conditions from Si isotopes in ancient cherts. To investigate isotope fractionation during silica-for‑carbonate replacement we analyzed the microscale Si and O isotope composition in different silica phases in a silicified zebra dolostone as well as their bulk δ18O and Δ’17O compositions. The subsequent replacement of carbonate layers is mimicked by decreasing δ18O and δ30Si. The textural relationship and magnitude of Si and O isotope fractionation is best explained by near-quantitative silica precipitation in an open system with finite Si. A Rayleigh model for silicification suggests positive Ɛ30/28Si during silicification, conforming with predictions for isotope distribution at chemical equilibrium from ab-initio models. Application of the modelled Ɛ30Si-T relationship yields silicification temperatures of approx. 50 °C. To reconcile the δ18Ochert composition with these temperatures, the δ18O of the fluid must have been between −2.5 and − 4 ‰, compositions for which the quartz phases fall close to the oxygen equilibrium fractionation line in three-isotope space. Diagenetic silica replacement appears to occur in O and Si isotopic equilibrium allowing reconstructions of temperatures of silicification from Si isotopes and derive the δ18O composition of the fluid – a highly desired value needed for accurate reconstructions of the temperature- and δ18O histories of the oceans.

Description: Lower crustal flow in regions of post-orogenic extension has been inferred to explain the exhumation of metamorphic core complexes and associated low-angle normal (detachment) fault systems. However, the origin of detachment faults, whether initially formed as high-angle or low-angle shear zones, and the extension is symmetric or asymmetric remains enigmatic. Here, we use numerical modeling constrained by geophysical and geological data to show that symmetric extension in the central Menderes Massif of western Anatolia is accommodated by the crustal flow. Our geodynamic model explains how opposite dipping Gediz and Büyük Menderes detachment faults are formed by ∼40° footwall rotation. Model predictions agree with seismic tomography data that suggests updoming of lower crust beneath the exhumed massifs, represented as “twin domes” and a flat Moho. Our work helps to account for the genetic relation between the exhumation of metamorphic core complexes and low-angle normal faulting in both Cordillera and Aegean orogenic regions and has important implications on crustal dynamics in extensional provinces.