Analysis of burnt schist outcrops in the alps: Relation to historical archaeology and Hannibal's crossing in 218 B.C.

Identification of the exact route followed by Hannibal during his invasion of Italia in the Second Punic War is one of the major questions of antiquity and one that historians/archaeologists have long studied. One of the many clues in the ancient literature that can help answer this question is the mention of fired rock, the result of a conflagration Hannibal is reputed to have employed to reduce the size of boulders in a blocking rockslide some distance down from the high col on the Italian side. The only route with evidence of fired rock along the roadway leading into Italia follows the Col du Clapier, one of the possible northern routes discussed by historians. Radiocarbon dating of calcined rocks is not possible, but whereas Time‐of‐Flight Secondary Ion Mass Spectrometry (ToF‐SIMS), Field Emission Scanning Electron Microscope (FESEM‐EDS), backscatter electron scanning microscopy (BSE), High Resolution Transmission Electron Microscope (HRTEM), and Raman Spectroscopic data do not provide an age for the burnt rock, compositional evidence of the conflagration derived from these analyses may shed light on Hannibal's actual route. © 2007 Wiley Periodicals, Inc.     

Geomagnetic control of the foF2 long-term trends

Further development of the method proposed by Danilov and Mikhailov is presented. The method is applied to reveal the foF2 long-term trends on 30 Northern Hemisphere ionosonde stations. Most of them show significant foF2 trends. A pronounced dependence of trend magnitude on geomagnetic (invariant) latitude is confirmed. Periods of negative/positive foF2 trends corresponding to the periods of long-term increasing/decreasing geomagnetic activity are revealed for the first time. Pronounced diurnal variations of the foF2 trend magnitude are found. Strong positive foF2 trends in the post-midnight-early-morning LT sector and strong negative trends during daytime hours are found on the sub-auroral stations for the period with increasing geomagnetic activity. On the contrary middle and lower latitude stations demonstrate negative trends in the early-morning LT sector and small negative or positive trends during daytime hours for the same period. All the morphological features revealed of the foF2 trends may be explained in the framework of contemporary F2-region storm mechanisms. This newly proposed F2-layer geomagnetic storm concept casts serious doubts on the hypothesis relating the F2-layer parameter long-term trends to the thermosphere cooling due to the greenhouse effect.     

Chicxulub impactites: Geochemical clues to the precursor rocks

Abstract— The 65 Ma Chicxulub impact structure, Mexico, with a diameter of ～180 km is the focus of geoscientific research because of its link to the mass extinction event at the Cretaceous‐Tertiary (K/T) boundary. Chicxulub, now buried beneath thick post‐impact sediments, is probably one of the best‐preserved terrestrial impact structures known. Because of its inaccessibility, only limited samples on the impact lithologies from a few drill cores are available. We report major element and Sr‐, Nd‐, O‐, and C‐isotopic data for Chicxulub impact‐melt lithologies and basement clasts in impact breccias of drill cores C‐1 and Y‐6, and for melt particles in the Chicxulub ejecta horizon at the K/T boundary in Beloc, Haiti. The melt lithologies with SiO₂ ranging from 58 to ～63 wt% show significant variations in the content of Al, Ca, and the alkalies. In the melt matrix samples, δ¹³C of the calcite is about ?3%o. The δ¹⁸O values for the siliceous melt matrices of Y‐6 samples range from 9.9 to 12.4%o. Melt lithologies and the black Haitian glass have rather uniform ⁸⁷Sr/⁸⁶Sr ratios (0.7079 to 0.7094); only one lithic fragment displays ⁸⁷Sr/⁸⁶Sr of 0.7141. The Sr model ages T^SrUR for most lithologies range from 830 to 1833 Ma; unrealistic negative model ages point to an open Rb‐Sr system with loss of Rb in a hydrothermal process. The ¹⁴³Nd/¹⁴⁴Nd ratios for all samples, except one basement clast with ¹⁴³Nd/¹⁴⁴Nd of 0.5121, cluster at 0.5123 to 0.5124. In an ?_Nd‐?_Sr diagram, impactites plot in a field delimited by ?_Nd of ?2 to ?6, and ?_Sr of 55 to 69. This field is not defined by the basement lithologies described to occur as lithic clasts in impact breccias and Cretaceous sediments. At least one additional intermediate to mafic precursor component is required to explain the data.     

Geochemical types of Volkhovites and possible diamond resource potential of areas occupied by Holocene fluidisites

Volkhovites—tektite-like glasses—have been detected in the Holocene glacial drift along the right bank of the Volkhov River. A cryptomagmatic model of their formation and pre-Holocene age of volkhovite melts, cinder, and frothed glasses has been suggested (Skublov et al., 2007). Four geochemical types of volkhovites are distinguished: (1) manganous (Mn, Fe, Cr, V, Si, Nb, Pb, H), (2) magnesian (Mg, Al, Ti, F, B), (3) potassic (K, Rb, Cs), and (4) calcic (Ca, REEs, Ba, U, Th, Ta, Hf, Y, Sc, Cl). In light of the geochemical data, volkhovites are regarded as natural silicate glasses of kimberlite-carbonatite composition. Their types are called kimberlitic (Mn type), kimberlitic-carbonatitic (Mg type), lamproitic-carbonatitic (K type), and carbonatitic (Ca type). Volkhovites are suggested to be indicators of undiscovered diamond mineralization of kimberlite or carbonatite (Chagatai) types.     

GGR Biennial Critical Review: Analytical Developments Since 2014

This GGR biennial critical review covers developments and innovations in key analytical methods published since January 2014, relevant to the chemical, isotopic and crystallographic characterisation of geological and environmental materials. In nine selected analytical fields, publications considered to be of wide significance are summarised, background information is provided and their importance evaluated. In addition to instrumental technologies, this review also presents a summary of new developments in the preparation and characterisation of rock, microanalytical and isotopic reference materials, including a précis of recent changes and revisions to ISO guidelines for reference material characterisation and reporting. Selected reports are provided of isotope ratio determinations by both solution nebulisation MC‐ICP‐MS and laser ablation‐ICP‐MS, as well as of radioactive isotope geochronology by LA‐ICP‐MS. Most of the analytical techniques elaborated continue to provide new applications for geochemical analysis; however, it is noted that instrumental neutron activation analysis has become less popular in recent years, mostly due to the reduced availability of nuclear reactors to act as a neutron source. Many of the newer applications reported here provide analysis at increasingly finer resolution. Examples include atom probe tomography, a very sensitive method providing atomic scale information, nanoscale SIMS, for isotopic imaging of geological and biological samples, and micro‐XRF, which has a spatial resolution many orders of magnitude smaller than conventional XRF.     

Micro-environmental controls on biomineralization: superficial processes of apatite and calcite precipitation in Quaternary soils, Roussillon, France

Calcium hydroxyapatite and calcite precipitates around bacteria were observed in 2-week-old alluvial topsoil (Roussillon area, SE France). This observation prompted a laboratory study of Ca²⁺ and PO₄³⁻ incorporation into hydroxyapatite and Ca²⁺ into calcite mediated by bacteria using similar topsoil material, but free from apatite and calcite. Subsamples were prepared using three different grain sizes, and experiments were undertaken using sucrose and different contents of Ca²⁺ and PO₄³⁻. Mineralization experiments proceeded over 5 days. Calcium and PO₄³⁻ sorption onto clay influenced the Ca/P ratio in the solutions. Hydroxyapatite and calcite precipitation only occurred in unsterilized samples. The presence of clay minerals promoted biomineralization.     

The impact of high altitude aircraft on the ozone layer in the stratosphere

The paper discusses the potential effects on the ozone layer of gases released by the engines of proposed high altitude supersonic aircraft. The major problem arises from the emissions of nitrogen oxides which have the potential to destroy significant quantities of ozone in the stratosphere. The magnitude of the perturbation is highly dependent on the cruise altitude of the aircraft. Furthermore, the depletion of ozone is substantially reduced when heterogeneous conversion of nitrogen oxides into nitric acid on sulfate aerosol particles is taken into account in the calculation. The sensitivity of the aerosol load on stratospheric ozone is investigated. First, the model indicates that the aerosol load induced by the SO₂ released by aircraft is increased by about 10–20% above the background aerosols at mid-high latitude of the Northern Hemisphere at 15 km for the NASA emission scenario A (the NASA emission scenarios are explained in Tables I to III). This increase in aerosol has small effects on stratospheric ozone. Second, when the aerosol load is increased following a volcanic eruption similar to the eruption of El Chichon (Mexico, April 1982), the ozone column in spring increases by as much as 9% in response to the injection of NO _x from the aircraft with the NASA emission scenario A. Finally, the modeled suggests that significant ozone depletion could result from the formation of additional polar stratospheric clouds produced by the injection of H₂O and HNO₃ by the aircraft engines.     

The LMDZ4 general circulation model: climate performance and sensitivity to parametrized physics with emphasis on tropical convection

The LMDZ4 general circulation model is the atmospheric component of the IPSL–CM4 coupled model which has been used to perform climate change simulations for the 4th IPCC assessment report. The main aspects of the model climatology (forced by observed sea surface temperature) are documented here, as well as the major improvements with respect to the previous versions, which mainly come form the parametrization of tropical convection. A methodology is proposed to help analyse the sensitivity of the tropical Hadley–Walker circulation to the parametrization of cumulus convection and clouds. The tropical circulation is characterized using scalar potentials associated with the horizontal wind and horizontal transport of geopotential (the Laplacian of which is proportional to the total vertical momentum in the atmospheric column). The effect of parametrized physics is analysed in a regime sorted framework using the vertical velocity at 500 hPa as a proxy for large scale vertical motion. Compared to Tiedtke’s convection scheme, used in previous versions, the Emanuel’s scheme improves the representation of the Hadley–Walker circulation, with a relatively stronger and deeper large scale vertical ascent over tropical continents, and suppresses the marked patterns of concentrated rainfall over oceans. Thanks to the regime sorted analyses, these differences are attributed to intrinsic differences in the vertical distribution of convective heating, and to the lack of self-inhibition by precipitating downdraughts in Tiedtke’s parametrization. Both the convection and cloud schemes are shown to control the relative importance of large scale convection over land and ocean, an important point for the behaviour of the coupled model.