Mass‐wasting of ancient aeolian dunes and sand fluidization during a period of global warming and inferred brief high precipitation: the Hopeman Sandstone (late Permian), Scotland

Large‐scale deformation structures in late Permian aeolian dune sands are associated with sand fluidization and injection. Exceptional precipitation and flooding of the desert margin are believed to have caused mass‐wasting by gravitational collapse and sliding of water‐saturated dunes, which loaded down‐dip strata, thus generating overpressure and triggering sand injection. This short‐lived but heavy precipitation seems to have been associated with a climatic change from arid Rotliegend dune deposition to widespread Zechstein marine conditions within the greater North Sea area, probably just before or coinciding with deposition of the rapidly expanding marine Kupferschiefer.     

New records of Ediacaran Acraman ejecta in drillholes from the Stuart Shelf and Officer Basin,South Australia

Abstract— New occurrences of the Acraman impact ejecta layer were recently discovered in two South Australian drillholes, SCYW‐79 1a (Stuart Shelf) and Munta 1 (Officer Basin) using lithostratigraphy, acritarch biostratigraphy, carbon isotope stratigraphy, and biomarker anomalies to predict the stratigraphic position. The ejecta layer is conspicuous because it consists of pink, sandsized, angular fragments of volcanic rock distributed along the bedding plane surface of green marine siltstone. In SCYW‐79 1a it forms a layer 5 mm thick; in Munta 1 the ejecta layer is thin and discontinuous because of its distance (?550 km) from the impact structure. Palynological, biomarker, and carbon isotope anomalies can now be shown to coincide with the ejecta layer in SCYW‐79 1a and Munta 1 suggesting the Acraman impact event may have had far reaching influences on the rapidly evolving Ediacaran biological and geochemical cycles.     

Topography,climate and ice masses: a review

Topography acts as a filter between regional climate and the consequent response of a glacier or ice sheet. It influences the mass and energy inputs and modifies the ice dynamics. The evolution of the ice sheet surface and, over longer time scales, of the bed topography modulates the climatic forcing. Until we have a better understanding of these topographic linkages, the use of geophysical signals from former ice masses to determine palaeoclimates must be regarded as fundamentally flawed.     

Near-infrared spectroscopic search for the close orbiting planet HD 75289b

We present a search for the near-infrared spectroscopic signature of the close orbiting extrasolar giant planet HD 75289b. We obtained ∼230 spectra in the wavelength range 2.18–2.19 μm using the Phoenix spectrograph at Gemini South. By considering the direct spectrum, derived from irradiated model atmospheres, we search for the absorption profile signature present in the combined star and planet light. Since the planetary spectrum is separated from the stellar spectrum at most phases, we apply a phase-dependent orbital model and tomographic techniques to search for absorption signatures.
Because the absorption signature lies buried in the noise of a single exposure we apply a multiline deconvolution to the spectral lines available in order to boost the effective signal-to-noise ratio (S/N) of the data. The wavelength coverage of 80 Å is expected to contain ∼100 planetary lines, enabling a mean line with S/N of 800 to be achieved after deconvolution. We are nevertheless unable to detect the presence of the planet in the data and carry out further simulations to show that broader wavelength coverage should enable a planet like HD 75289b to be detected with 99.9 per cent confidence. We investigate the sensitivity of our method and estimate detection tolerances for mismatches between observed and model planetary atmospheres.     

ANALYSIS OF COUNT DATA USING POISSON REGRESSION*

In geographical research the data of interest are often in the form of counts. Standard regression analysis is inappropriate for such data, but if certain assumptions are met, a form of regression based on the Poisson distribution can be used. This paper illustrates the use of Poisson regression in the computer package GLIM with an example from historical geography. Apprentice migration to Edinburgh is regressed on a combination of categorical, count, and continuous explanatory variables.     

Late Quaternary stratigraphy of the northern Rockall trough and Faeroe-Shetland channel,northeast Atlantic Ocean

A late Quaternary deep-water stratigraphic framework has been established for the deep-water areas (>450m) of the northern Rockall Trough and Faeroe-Shetland Channel. Four stratigraphic units (1–4) are identified; these are primarily biostratigraphic units based on dinoflagellate cyst evidence. Unit 1 represents the late Weichselian glacial (pre-13 000 yr BP); unit 2 the Late Glacial Interstadial (11 000-13 000 yr BP); unit 3 is of Younger Dryas age (10 000-11 000 yr BP); and unit 4 represents the Holocene interglacial (post-10 000 yr BP). This stratigraphy is supported by the discovery of the mixed Vedde Ash (10 600 yr BP) and North Atlantic Ash zone 1, and the Saksunarvatn Ash (9000–9100 yr BP), concentrated in units 3 and 4 respectively. The sedimentology indicates that the oceanographic regime underwent a major change between the glacial and interglacial stages. This is marked by the onset of strong bottom current activity, allied to the restoration of overflow of the Norwegian Sea Deep Water into the North Atlantic, towards the end of the Younger Dryas Stadial. Despite intense bioturbation and bottom-current reworking the basic stratigraphic framework is maintained. Recognition of two volcanic ash markers enables correlation with established onshore and offshore sequences of marine and non-marine environments.     

A Milankovitch scale for Cenomanian time

A detailed cyclostratigraphy is present in the rhythmically bedded Cenomanian hemipelagic chalks of the northern Anglo-Paris Basin, which can be correlated over 100,000 km². Individual decimetre-scale couplets probably represent the precession cycle (modes at 18 or 23 kyr), and can be readily grouped in sets averaging five, indicative of the short cycle of eccentricity (100 kyr). A composite cyclostratigraphy for the basin is presented here, and is used as the basis for a Cenomanian time-scale (20 and 100 kyr units). The total duration of the Cenomanian thus obtained (4.4 Myr) compares well with recent radiometric dates of 4.0–4.5 Myr. The time-scale is used to estimate the length of ammonite, inoceramid, and planktonic foraminiferal zones, the rates of formation of authigenic minerals (glauconite), sedimentation rates and the duration of transgressions and anoxic events.     

Bianchi model CMB polarization and its implications for CMB anomalies

We derive the cosmic microwave background (CMB) radiative transfer equation in the form of a multipole hierarchy in the nearly Friedmann–Robertson–Walker limit of homogeneous, but anisotropic, universes classified via their Bianchi type. Compared with previous calculations, this allows a more sophisticated treatment of recombination, produces predictions for the polarization of the radiation and allows for reionization. Our derivation is independent of any assumptions about the dynamical behaviour of the field equations, except that it requires anisotropies to be small back to recombination; this is already demanded by observations.
We calculate the polarization signal in the Bianchi VII _h case, with the parameters recently advocated to mimic the several large-angle anomalous features observed in the CMB. We find that the peak polarization signal is  ∼1.2 μK  for the best-fitting model to the temperature anisotropies, and is mostly confined to multipoles   l < 10  . Remarkably, the predicted large-angle EE and TE power spectra in the Bianchi model are consistent with Wilkinson Microwave Anisotropy Probe ( WMAP ) observations that are usually interpreted as evidence of early reionization. However, the power in B-mode polarization is predicted to be similar to the E-mode power and parity-violating correlations are also predicted by the model; the WMAP non-detection of either of these signals casts further strong doubts on the veracity of attempts to explain the large-angle anomalies with global anisotropy. On the other hand, given that there exist further dynamical degrees of freedom in the VII _h universes that are yet to be compared with CMB observations, we cannot at this time definitively reject the anisotropy explanation.