Graben width controlling syn-rift sedimentation: the Palaeogene southern Upper Rhine Graben as an example

Eocene to Early Oligocene syn-rift deposits of the southern Upper Rhine Graben (URG) accumulated in restricted environments. Sedimentation was controlled by local clastic supply from the graben flanks, as well as by strong intra-basinal variations in accommodation space due to differential tectonic subsidence, that in turn led to pronounced lateral variations in depositional environment. Three large-scale cycles of intensified evaporite sedimentation were interrupted by temporary changes towards brackish or freshwater conditions. They form three major base level cycles that can be traced throughout the basin, each of them representing a stratigraphic sub-unit. A relatively constant amount of horizontal extension (ΔL) in the range of 4-5km has been estimated for the URG from numerous cross-sections. The width of the rift (L f ), however, varies between 35 and more than 60km, resulting in a variable crustal stretching factor between the bounding masterfaults. Apart from block tilting, tectonic subsidence was, therefore, largely controlled by changes in the initial rift width (L 0). The along-strike variations of the graben width are responsible for the development of a deep, trough-like evaporite basin (Potash Basin) in the narrowest part of the southern URG, adjacent to shallow areas in the wider parts of the rift such as the Colmar Swell in the north and the Rhine Bresse Transfer Zone that delimits the URG to the south. Under a constant amount of extension, the along-strike variation in rift width is the principal factor controlling depo-centre development in extensional basin

Upper Rhine Graben: quantitative aspects of rifting and syn-rift sedimentation with focus on the Palaeogene series in the southern part

Basin evolution in the Upper Rhine Graben (URG) was studied according to palecology, sedimentology, cross-section balancing and numerical modelling, with focus on the genesis of the Palaeogene series of the southern URG. Middle Eocene to Early Oligocene deposits accumulated under restricted conditions during an under filled basin stage. Sedimentation was controlled by differential tectonic subsidence and re-sedimentation of graben shoulder derived clastics within the graben and involved various depositional settings. Evaporites and marls were deposited in the depo-centre and a lacustrine to brackish facies developed in the marginal parts of the basin, while alluvial fans formed along the border faults. During Middle to Late Oligocene the URG was affected by supra-regional subsidence and connected to the overfilled North Alpine Foreland Basin, as reflected by a major marine transgression. The rift basin was converted into an over-filled open depositional system. Palecology of Early Oligocene laminites suggest marine influenced to isolated lake settings that experienced rapid fluctuations in salinity and lake level. Next to fluctuating Palaeo humidity the depositional dynamics were controlled by the elevated rift shoulders forming a barrier against external sediment/ water supply. Syn-rift subsidence was first order controlled by the width of the graben compartments and can be explained with extensional strain partitioning. Cross-section balancing shows that that the extension among the different rift compartments is almost the same and amounts to about 5 km. Consequently high extensional strain led to depo-centre formation in the narrow rift compartments, while relative low strain and subsidence occurred in the broad rift segments. Rifting durated from the Middle Eocene to the Early Miocene, renewed extension occurred during the Pliopleistocene. It occurred at constant but very low strain rates (1.7*10-16s-1) and involved brittle crustal deformation on a high viscous mantle. The necking level in the URG is located near the Moho. Under this circumstanced crustal extension is entirely compensated by rift basin formation. This will lead to strong static unloading equating the load of the replaced crust (Basin volume * crustal density). Flexural Isostasy modelling shows the Recent pattern of shoulder uplift can be explained with long term changes in crustal static loading due to URG rifting and Alpine Orogeny and an elastic plate thickness of 15 km, however the real observed rock uplift is higher than the modelled one. Eocene to Early Oligocene Rifting is likely to have occurred on a wide Alpine subduction related flexural forebulge. Regional subsidence during the middle Oligocene in the URG area might be explained with relaxation of this forebulge due to mechanical slab failure occurring at the transition from syn-post collisional Alpine orogeny stage. Renewed uplift that finalised Palaeogene sedimentary deposition and rifting however corresponds to a change in stress field from extension to compression and caused Neogene rise of the Vosges Black Forest Arc

Efficient melt stabilization of polyethylene with quercetin, a flavonoid type natural antioxidant

The potential use of quercetin, a flavonoid type natural antioxidant, as a stabilizer in polyethylene was explored in this work. Its efficiency was compared to that of Irganox 1010, a hindered phenolic antioxidant used routinely in industrial practice, both in the presence and the absence of a phosphorous secondary stabilizer. The study was carried out with a Phillips type polyethylene and the efficiency of the additive packages was checked by various methods on samples produced by multiple extrusions. Quercetin content changed from 0 to 1000 ppm in 10 steps. The results showed that quercetin is a very effi-cient antioxidant. It prevents the formation of long chain branches already at a concentra-tion as small as 50 ppm and its dosage at 250 ppm renders the polymer sufficient long term residual stability. The efficiency of quercetin is considerably better than that of Irganox 1010, the hindered phenolic antioxidant used as reference stabilizer. The difference in efficiency might be explained with the dissimilar number of active –OH groups on the two molecules, but the stabilization mechanism of quercetin may be also different from that of I1010. Quercetin interacts with the phosphonite secondary stabilizer used, which improves dispersion and increases efficiency. Besides its advantages, quercetin has also some drawbacks (very high melting temperature, poor solubility in polyethylene and strong yellow color), which must be overcome before the substance can be used in practice

RESSEÇÃO ESPACIAL EM FOTOGRAMETRIA COM QUATÉRNIOS

A fotogrametria usa comumente a Equação da colinearidade com as rotações segundo os eixos cartesianos dadas com os ângulos de Euler. No entanto, podem ocorrer combinações desses ângulos que torna a matriz de rotação instável e as soluções podem não convergir ou serem indefinidas. Este problema, chamado de gimbal lock, é muito comum em robótica, visão por computadores e aeronáutica, quando é necessário definir a posição e orientação de uma câmara no espaço tridimensional e tem sido resolvido com a substituição dos ângulos de Euler pelo uso dos quatérnios. Este trabalho tem por objetivo usar esta solução para resolver os problemas de orientações críticas em fotogrametria nos casos de resseção espacial. Foram implementados programas com métodos iterativos e diretos com substituição dos ângulos de Euler pelos quatérnios para comparações com o métoda Equação da colinearidade, usando dados de situações reais de medições obtidas com fotogrametria terrestre. Os diferentes testes e implementações efetuados mostraram as vantagens e desvantagens de cada um dos métodos e comprovou que os quatérnios são mais robustos, fornecem resultados mais confiáveis e permitem cálculos de resseção espacial de fotografias em posições com ambiguidades de rotações e situações críticas de gimbal lock