ALBERT

Description: Ion microprobe dating in Wedel Jarlsberg Land, southwestern Spitsbergen, provides new evidence of early Neoproterozoic ( c . 950 Ma) meta-igneous rocks, the Berzeliuseggene Igneous Suite, and late Neoproterozoic ( c . 640 Ma) amphibolite-facies metamorphism. The older ages are similar to those obtained previously in northwestern Spitsbergen and Nordaustlandet where they are related to the Tonian age Nordaustlandet Orogeny. The younger ages complement those obtained recently from elsewhere in Wedel Jarlsberg Land of Torellian deformation and metamorphism at 640 Ma. The Berzeliuseggene Igneous Suite occurs in gently N-dipping, top-to-the-S-directed thrust sheets on the eastern and western sides of Antoniabreen where it is tectonically intercalated with younger Neoproterozoic sedimentary formations, suggesting that it provided a lower Tonian basement on which upper Tonian to Cryogenian sediments (Deilegga Group) were deposited. They were deformed together during the Torellian Orogeny, prior to deposition of Ediacaran successions (Sofiebogen Group) and overlying Cambro-Ordovician shelf carbonates, and subsequent Caledonian and Cenozoic deformation. The regional importance of the late Neoproterozoic Torellian Orogeny in Svalbard's Southwestern Province and its correlation in time with the Timanian Orogeny in the northern Urals as well as tectonostratigraphic similarities between the Timanides and Pearya (northwestern Ellesmere Island) favour connection of these terranes prior to the opening of the Iapetus Ocean and Caledonian Orogeny.

Description: Here we record the occurrence of a new species of the Herefordshire Lagerstätte ostracod genus Pauline from the Lower Silurian (upper Telychian) of North Greenland. Pauline nivisis sp. nov. was recovered from a limestone boulder (Pentamerus Bjerge Formation) collected south of Kap Schuchert, Washington Land. It is reasonable to transpose the palaeobiology known from the Herefordshire Pauline avibella – body, limbs including swimming antennae, lateral eyes, gills and alimentary system – into the carapace of the Greenland species, which represents the oldest cylindroleberidid myodocopid and almost the oldest known myodocope, and is the first record of a Herefordshire Lagerstätte genus from outside the Welsh Borderland locality. Morphological, sedimentological and faunal evidence suggest that the Greenland species was nektobenthic. This is compatible with the notion that ostracods (specifically myodocopids) did not invade the water column until later in the Silurian, in the Wenlock and Ludlow epochs. Pauline is an Early Silurian link between ‘Baltic-British’ and North Laurentian ostracod faunas, endorsing the idea that the UK and Greenland were in close geographical proximity, near a remnant Iapetus Ocean, during late Llandovery time.

Description: We present large-eddy simulations (LES) of turbulent mixing at a perturbed, spherical interface separating two fluids of differing densities and subsequently impacted by a spherically imploding shock wave. This paper focuses on the differences between two fundamental configurations, keeping fixed the initial shock Mach number 1.2, the density ratio (precisely |A0| 0.67) and the perturbation shape (dominant spherical wavenumber l0=40 and amplitude-to-initial radius of 3%): the incident shock travels from the lighter fluid to the heavy fluid or, inversely, from the heavy to the light fluid. After describing the computational problem we present results on the radially symmetric flow, the mean flow, and the growth of the mixing layer. Turbulent statistics are developed in Part 2 (Lombardini, M., Pullin, D. I. & Meiron, D. I. J. Fluid Mech., vol. 748, 2014, pp. 113-142). A wave-diagram analysis of the radially symmetric flow highlights that the light-heavy mixing layer is processed by consecutive reshocks, and not by reverberating rarefaction waves as is usually observed in planar geometry. Less surprisingly, reshocks process the heavy-light mixing layer as in the planar case. In both configurations, the incident imploding shock and the reshocks induce Richtmyer-Meshkov (RM) instabilities at the density layer. However, we observe differences in the mixing-layer growth because the RM instability occurrences, Rayleigh-Taylor (RT) unstable scenarios (due to the radially accelerated motion of the layer) and phase inversion events are different. A small-amplitude stability analysis along the lines of Bell (Los Alamos Scientific Laboratory Report, LA-1321, 1951) and Plesset (J. Appl. Phys., vol. 25, 1954, pp. 96-98) helps quantify the effects of the mean flow on the mixing-layer growth by decoupling the effects of RT/RM instabilities from Bell-Plesset effects associated with geometric convergence and compressibility for arbitrary convergence ratios. The analysis indicates that baroclinic instabilities are the dominant effect, considering the low convergence ratio (2) and rather high (l 〉10) mode numbers considered. © 2014 Cambridge University Press.

Description: We present large-eddy simulations (LES) of turbulent mixing at a perturbed, spherical interface separating two fluids of differing densities and subsequently impacted by a spherically imploding shock wave. This paper focuses on the differences between two fundamental configurations, keeping fixed the initial shock Mach number 1.2, the density ratio (precisely |A0| 0.67) and the perturbation shape (dominant spherical wavenumber 0=40 and amplitude-to-initial radius of 3 %): the incident shock travels from the lighter fluid to the heavy one, or inversely, from the heavy to the light fluid. In Part 1 (Lombardini, M., Pullin, D. I. & Meiron, D. I., J. Fluid Mech., vol. 748, 2014, pp. 85-112), we described the computational problem and presented results on the radially symmetric flow, the mean flow, and the growth of the mixing layer. In particular, it was shown that both configurations reach similar convergence ratios 2. Here, turbulent mixing is studied through various turbulence statistics. The mixing activity is first measured through two mixing parameters, the mixing fraction parameter Θ and the effective Atwood ratio Ae, which reach similar late time values in both light-heavy and heavy-light configurations. The Taylor-scale Reynolds numbers attained at late times are estimated at approximately 2000 in the light-heavy case and 1000 in the heavy-light case. An analysis of the density self-correlation b, a fundamental quantity in the study of variable-density turbulence, shows asymmetries in the mixing layer and non-Boussinesq effects generally observed in high-Reynolds-number Rayleigh-Taylor (RT) turbulence. These traits are more pronounced in the light-heavy mixing layer, as a result of its flow history, in particular because of RT-unstable phases (see Part 1). Another measure distinguishing light-heavy from heavy-light mixing is the velocity-to-scalar Taylor microscales ratio. In particular, at late times, larger values of this ratio are reported in the heavy-light case. The late-time mixing displays the traits some of the traits of the decaying turbulence observed in planar Richtmyer-Meshkov (RM) flows. Only partial isotropization of the flow (in the sense of turbulent kinetic energy (TKE) and dissipation) is observed at late times, the Reynolds normal stresses (and, thus, the directional Taylor microscales) being anisotropic while the directional Kolmogorov microscales approach isotropy. A spectral analysis is developed for the general study of statistically isotropic turbulent fields on a spherical surface, and applied to the present flow. The resulting angular power spectra show the development of an inertial subrange approaching a Kolmogorov-like -5/3 power law at high wavenumbers, similarly to the scaling obtained in planar geometry. It confirms the findings of Thomas & Kares (Phys. Rev. Lett., vol. 109, 2012, 075004) at higher convergence ratios and indicates that the turbulent scales do not seem to feel the effect of the spherical mixing-layer curvature. © 2014 Cambridge University Press.

Description: The theory to predict the performance and loads on rotors (propellers, screws, windmills) has a history of more than a century. Apart from modern computational fluid dynamics and vortex panel models taking the true blade geometry into account, most other models proceed from an infinitely thin actuator disc or line. These models assume an externally defined force field distributed at the disc or line, representing the loads on the real rotor. Given this force field, the flow is solved by momentum balances or by the equations of motion. The use of external force fields was discussed in textbooks of the first decades of the 20th century, but has received little attention since then. This paper investigates the higher-order effect of adding thickness to the actuator disc or changing the actuator line to a blade with cross-sectional dimensions. For the generation of a Rankine vortex by a force field acting on an actuator disc with thickness, an exact solution has been found in which not only the thrust and torque determine the flow, but also a radial force. This force is conservative, in contrast to the other force components. For rotor blades, a conservative normal and radial force acting on the chordwise bound vorticity is present. This explains the experimentally observed inboard motion of the tip vortex of model wind turbine rotors before the wake induction field drives it outboard. Simulations by computational fluid mechanics and a vortex panel code reproduce the inboard motion, but an actuator line analysis, in which the chordwise vorticity is absent, does not. The conservative load is only 1-2% of the thrust on the entire blade but ∼ 10% of the thrust at the tip (r/R〉0:9).Conservative forces at the disc and rotor blade vanish for vanishing disc thickness or blade cross-section, so play no role in any of the infinitely thin actuator disc or line methods. However, if higher-order effects of non-zero dimensions are to be modelled, the conservative force field has to be included. © 2014 Cambridge University Press.

Description: The Dead Sea fault (DSF) is one of the most active plate boundaries in the world. Understanding the Quaternary history and sediments of the DSF requires investigation into the Neogene development of this plate boundary. DSF lateral motion preceded significant extension and rift morphology by ~10 Ma. Sediments of the Sedom Formation, dated here between 5.0 ± 0.5 Ma and 6.2−2.1+inf Ma, yielded extremely low 10Be concentrations and 26Al is absent. These reflect the antiquity of the sediments, deposited in the Sedom Lagoon, which evolved in a subdued landscape and was connected to the Mediterranean Sea. The base of the overlying Amora Formation, deposited in the terminal Amora Lake which developed under increasing relief that promoted escarpment incision, was dated at 3.3−0.8+0.9 Ma. Burial ages of fluvial sediments within caves (3.4 ± 0.2 Ma and 3.6 ± 0.4 Ma) represent the timing of initial incision. Initial DSF topography coincides with the earliest Red Sea MORB's and the East Anatolian fault initiation. These suggest a change in the relative Arabian–African plate motion. This change introduced the rifting component to the DSF followed by a significant subsidence, margin uplift, and a reorganization of relief and drainage pattern in the region resulting in the topographic framework observed today.

Description: Since the beginning of the Holocene, hunter-gatherers have occupied the central-south Brazilian coast, as it was a very productive estuarine environment. Living as fishers and mollusk gatherers, they built prehistoric shellmounds, known assambaqui, up to 30 m high, which can still be found today from the Espírito Santo (21°S) to Rio Grande do Sul (32°S) states, constituting an important testimony of paleodiversity and Brazilian prehistory. The chronology of the Sambaqui da Tarioba, situated in Rio das Ostras, Rio de Janeiro, is discussed herein. Selected well-preserved shells ofIphigenia brasilianaand charcoal from fireplaces in sequential layers were used for radiocarbon dating analysis. Based on a statistical model developed using OxCal software, the results indicate that the settlement occupation begun most probably around 3800 cal BP and lasted for up to 5 centuries.

Description: Since the beginning of the Holocene, hunter-gatherers have occupied the central-south Brazilian coast, as it was a very productive estuarine environment. Living as fishers and mollusk gatherers, they built prehistoric shellmounds, known as sambaqui, up to 30 m high, which can still be found today from the Espírito Santo (21°S) to Rio Grande do Sul (32°S) states, constituting an important testimony of paleodiversity and Brazilian prehistory. The chronology of the Sambaqui da Tarioba, situated in Rio das Ostras, Rio de Janeiro, is discussed herein. Selected well-preserved shells of Iphigenia brasiliana and charcoal from fireplaces in sequential layers were used for radiocarbon dating analysis. Based on a statistical model developed using OxCal software, the results indicate that the settlement occupation begun most probably around 3800 cal BP and lasted for up to 5 centuries.

Description: This article presents a set of accelerator mass spectrometry (AMS) radiocarbon dates derived from human bone within burial contexts at CA-NAP-399 in Napa County, California, USA.

Description: The study of the evolution of organic matter subjected to space conditions, and more specifically to Solar photons in the vacuum ultraviolet range (120–200 nm) has been undertaken in low-Earth orbit since the 1990s, and implemented on various space platforms. This paper describes a photochemistry experiment called AMINO, conducted during 22 months between 2009 and 2011 on the EXPOSE-R ESA facility, outside the International Space Station. Samples with relevance to astrobiology (connected to comets, carbonaceous meteorites and micrometeorites, the atmosphere of Titan and RNA world hypothesis) have been selected and exposed to space environment. They have been analysed after return to the Earth. This paper is not discussing the results of the experiment, but rather gives a general overview of the project, the details of the hardware used, its configuration and recent developments to enable long-duration exposure of gaseous samples in tight closed cells enabling for the first time to derive quantitative results from gaseous phase samples exposed in space.