Hard X-ray stereographic microscopy for single-shot differential phase imaging

The characterisation of fast phenomena at the microscopic scale is required for the understanding of catastrophic responses of materials to loads and shocks, the processing of materials by optical or mechanical means, the processes involved in many key technologies such as additive manufacturing and microfluidics, and the mixing of fuels in combustion. Such processes are usually stochastic in nature and occur within the opaque interior volumes of materials or samples, with complex dynamics that evolve in all three dimensions at speeds exceeding many meters per second. There is therefore a need for the ability to record three-dimensional X-ray movies of irreversible processes with resolutions of micrometers and frame rates of microseconds. Here we demonstrate a method to achieve this by recording a stereo phase-contrast image pair in a single exposure. The two images are combined computationally to reconstruct a 3D model of the object. The method is extendable to more than two simultaneous views. When combined with megahertz pulse trains of X-ray free-electron lasers (XFELs) it will be possible to create movies able to resolve 3D trajectories with velocities of kilometers per second

Constraining long-term denudation and faulting history in intraplate regions by multisystem thermochronology: An example of the Sudetic Marginal Fault (Bohemian Massif, central Europe)

The Rychlebské hory Mountain region in the Sudetes (NE Bohemian Massif) provides a natural laboratory for studies of postorogenic landscape evolution. This work reveals both the exhumation history of the region and the paleoactivity along the Sudetic Marginal Fault (SMF) using zircon (U-Th)/He (ZHe), apatite fission track (AFT), and apatite (U-Th)/He (AHe) dating of crystalline basement and postorogenic sedimentary samples. Most significantly, and in direct contradiction of traditional paleogeographic reconstructions, this work has found evidence of a large Cretaceous sea and regional burial (to >6.5 km) of the Carboniferous-Permian basement in the Late Cretaceous (~95–80 Ma). During the burial by sediments of the Bohemian Cretaceous Basin System, the SMF acted as a normal fault as documented by offset ZHe ages across the fault. At 85–70 Ma, the basin was inverted, Cretaceous strata eroded, and basement blocks were exhumed to the near surface at a rate of ~300 m/Ma as evidenced by Late Cretaceous–Paleocene AFT ages and thermal modeling results. There is no appreciable difference in AFT and AHe ages across the fault, suggesting that the SMF acted as a reverse fault during exhumation. In the late Eocene–Oligocene, the basement was locally heated to <70°C by magmatic activity related to opening of the Eger rift system. Neogene or younger thermal activity was not recorded in the thermochronological data, confirming that late Cenozoic uplift and erosion of the basement blocks was limited to less than ∼1.5 km in the study area

Fire-prone plant communities and palaeoclimate of a Late Cretaceous fluvial to estuarine environment, Pecinov quarry, Czech Republic

The botanical identity and facies distribution of fossil charcoal is described from Middle to Late Cenomanian (90–94 Ma) fluvial to estuarine units at Pecínov quarry, near Prague, Czech Republic. Braided alluvial facies associations contain charred conifer woods (family Pinaceae) possibly derived from upland forest fires, and abundant charred angiosperm woods, flowers and inflorescences (families Lauraceae and ?Platanaceae) derived from riparian gallery forest fires (Unit 2). Retrogradational coastal salt marsh facies associations contain abundant charred conifer wood (families Cheirolepidiaceae and Cupressaceae/Taxodiaceae) derived from fires in halophytic backswamp forest, and rare pinaceous charred cones and lauraceous angiosperm wood washed downstream from fires further inland (Units 3–4). Progradational coastal facies associations within an estuary mouth setting contain abundant charred conifer wood (family Cupressaceae/Taxodiaceae), common taxodiaceous conifer and angiosperm leaves, fern rachises, and lycopsid stems derived from fires in mesic backswamp taxodiaceous forests and supra-tidal fern-lycopsid thickets (Unit 5). Growth rings in angiosperm and conifer woods, leaf physiognomy and computer models indicate that climate was equable, warm and humid, but that there was a short annual dry season; most fires probably occurred during these annual drought periods. The abundance of charcoal and the diversity of taxa preserved in this state indicate that nearly all plant communities were fire-prone. Physiognomically, the Pecínov flora resembles present-day seasonally-dry subtropical forests where fires are a common occurrence

Intercontinental correlation of organic carbon and carbonate stable-isotope records: evidence of climate and sea-level change during the Turonian (Cretaceous)

Carbon (δ13Corg, δ13Ccarb) and oxygen (δ18Ocarb) isotope records are presented for an expanded Upper Cretaceous (Turonian–Coniacian) hemipelagic succession cored in the central Bohemian Cretaceous Basin, Czech Republic. Geophysical logs, biostratigraphy and stable carbon isotope chemostratigraphy provide a high-resolution stratigraphic framework. The δ13Ccarb and δ13Corg profiles are compared, and the time series correlated with published coeval marine and non-marine isotope records from Europe, North America and Japan. All previously named Turonian carbon isotope events are identified and correlated at high-resolution between multiple sections, in different facies, basins and continents. The viability of using both carbonate and organic matter carbon isotope chemostratigraphy for improved stratigraphic resolution, for placing stage boundaries, and for intercontinental correlation is demonstrated, but anchoring the time series using biostratigraphic data is essential. An Early to Middle Turonian thermal maximum followed by a synchronous episode of stepped cooling throughout Europe during the Middle to Late Turonian is evidenced by bulk carbonate and brachiopod shell δ18Ocarb data, and regional changes in the distribution and composition of macrofaunal assemblages. The Late Turonian Cool Phase in Europe was coincident with a period of long-term sea-level fall, with significant water-mass reorganization occurring during the mid-Late Turonian maximum lowstand. Falling Δ13C (δ13Ccarb – δ13Corg) trends coincident with two major cooling pulses, point to pCO2 drawdown accompanying cooling, but the use of paired carbon isotopes as a high-resolution pCO2 proxy is compromised in the low-carbonate sediments of the Bohemian Basin study section by diagenetic overprinting of the δ13Ccarb record. Carbon isotope chemostratigraphy is confirmed as a powerful tool for testing and refining intercontinental and marine to terrestrial correlations

Cretaceous

The Cretaceous evolution of sedimentary basins in Central Europe was influenced by the interplay of two main processes: plate tectonics and eustatic sea-level change. Global plate-tectonic reconfiguration resulted in the widening of the Central Atlantic, the opening of the Bay of Biscay, and the opening of the South Atlantic Ocean causing a counter-clockwise rotation of Africa coeval with the closure of the Tethys Ocean. Convergence between the European and African plates led to the formation of the Alps and the Western Carpathians as a classic thrust orogen. Several orogenic phases can be distinguished. The Jurassic - Cretaceous, Eo-Alpine orogeny was followed by Meso- and Neo-Alpine deformational events (e.g. Faupl & Wagreich 2000; see also Froitzheim et al. 2008; Reicherter et al. 2008). During the Early Cretaceous, ongoing rifting of the North Sea Graben system and the resulting stress pattern produced a variety of smaller, partly isolated basins in Central Europe. The late Palaeozoic - early Mesozoic rifting in the North Sea ceased in late Early Cretaceous times and thermal subsidence prevailed in western and central Europe from the Albian to the Turonian. Elevated spreading rates along mid-ocean ridges and increased rates of intra-oceanic plateau volcanism resulted in the highest global sea level during Phanerozoic times (Haq et al. 1988; Hardenbol et al. 1998). The former margins of Early Cretaceous basins were flooded worldwide, and several new seaways connected the cold Boreal areas of the Arctic and western Siberia with the warm subtropical Tethys Ocean. Central Europe evolved into an extended epicontinental shelf sea with a variety of intrashelf basins. The palaeogeography of southern Central Europe is determined by the convergence of Europe and Africa and can be divided into: (1) a southern European passive margin, which comprising the Helvetic, the Outer Carpathians and other comparable European shelf units on continental crust (including Subpenninic units sensu Schmid et al. 2004); (2) the units of the Liguria-Piemont-Penninic ocean system; and (3) the northern margin of the Adriatic plate comprising the Austro-Alpine, the Inner Western Carpathians (Fatric, Tatric), and the Southern Alpine units