A review of the origin and setting of tepees and their associated fabrics

Carbonate hardgrounds often occur at the surface of shallow subtidal to supratidal, lacustrine, and subaerial carbonate shelf sediments. These are commonly disrupted and brecciated when the surface area of these crusts increases. In the subtidal environment, megapolygons form when cementation of the matrix causes the surface area of the hardgrounds to expand. Similar megapolygons form in the supratidal, lacustrine and subaerial settings when repeated incremental fracturing and fracture fill by sediment and/or cement also causes the area of the hardgrounds to expand. The arched up antiform margins of expansion megapolygons are known as tepees. The types of tepees found in the geological record include: (1) Submarine tepees which form in shallow carbonate-saturated waters where fractured and bedded marine grainstones are bound by isopachous marine-phreatic acicular and micritic cements. The surfaces of these brecciated crusts have undergone diagenesis and are bored. Unlike tepees listed below they contain no vadose pisolites or gravity cements; (2) Peritidal and lacustrine tepees are formed of crusts characterized by fenestral. pisolitic and laminar algal fabrics. This similarity in fabric makes these tepees of different origins difficult to separate. Peritidal tepees occur where the marine phreatic lens is close to the sediment surface and the climate is tropical. They are associated with fractured and bedded tidal flat carbonates. Their fracture fills contain geopetal asymmetric travertines of marine-vadose origin and/or marine phreatic travertines and/or Terra rossa sediments. The senile form of these peritidal tepees are cut by labyrinthic dissolution cavities filled by the same material. Lacustrine tepees form in the margins of shallow salinas where periodic groundwater resurgence is common. They include groundwater tepees which form over evaporitic ‘boxwork’ carbonates, and extrusion tepees which also form where periodic groundwater resurgence occurs at the margins of shallow salinas, but the dominant sediment type is carbonate mud. These latter tepee crusts are coated and crosscut by laminated micrite; the laminae extend from the fractures downward into the underlying dolomitic micrite below the crust. Both peritidal and lacustrine tepees form where crusts experience alternating phreatic and vadose conditions, in time intervals of days to years. Cement morphologies reflect this and the crusts often contain gravitational, meniscus vadose cements as well as phreatic isopachous cement rinds. (3) Caliche tepees which are developed within soil profiles in a continental setting. They are formed by laminar crusts which contain pisolites, and fractures filled by micritic laminae, microspar, spar and Terra rossa. Most of the cements are gravitational and/or meniscoid. In ancient carbonates, when their cementation and diagenetic fabric can be interpreted, tepee structures can be used as environmental indicators. They can also be used to trace the evolution of the depositional and hydrological setting.     

Volcans de la chaîne des Puys (Massif central,France) : point sur la chronologie Vasset–Kilian–Pariou–Chopine

On the basis of radiocarbon ages obtained on wood burned by base surges and tephrochronological observations, it has been possible to assess that the Puy Chopine, aged ca 9700 yr is older by a few centuries than both the Vasset and Kilian volcanoes. The last two have nearly the same age, ca 9300–9400 yr. Layers of trachytic tephra, most probably originated from Kilian or Vasset, can be observed overlapping those from the Pariou. This last volcano had been previously thought to be the younger of the area on the basis of the observation of trachytic tephra beneath its own tephra. However, new observations allow us to assume that those trachytes originated from the acid phase of the Pariou itself. Therefore, it can be assessed that the four volcanoes erupted according to the following sequence: Chopine/Pariou/?Vasset?/Kilian; the chronological situation of Vasset lies on poor arguments and it should be confirmed. To cite this article: D. Miallier et al., C. R. Geoscience 336 (2004).     

United States lunar mapping — a basis for and result of project apollo

This paper includes 3 related presentations on United State lunar mapping made to the International symposium A Hundred Years of Lunar Mapping at Athens, Greece in May 1978. It reviews Project Apollo's role as both stimulas to and beneficiary of lunar mapping. Lunar cartographic technology and products employed and produced by the U.S. Defense Mapping Agency and its predecessor organizations, are discussed.Presented at the IAU-COSPAR Julius Schmidt Symposium on 100 Years of Lunar Mapping held at Lagonissi, Greece, 25–27 May, 1978.     

Évolution temporelle et architecture interne d'un banc sableux estuarien : la Longe de Boyard (littoral atlantique,France)

The evolution and the internal architecture of an estuary type sand ridge has been studied with a set of bathymetric data recorded during the last two centuries and with a dense grid of recent very high resolution seismic profiles. Bathymetric data of the so-called, Longe de Boyard sand ridge, displays sand losts due to wave and tide erosion. Internal geometry, through seismic profile analysis, indicates two main phases of deposition recording both, a recent high energy environment and an older low energy one, respectively. Such an evolution is believed to record changes in sedimentation processes mainly related to the end of the Holocene transgression (8 000–5 000 yr BP). To cite this article: É. Chaumillon et al., C. R. Geoscience 334 (2002) 119–126.     

Virtual MHD Jets on Grids

As network performance has outpaced computational power and storage capacity, a new paradigm has evolved to enable the sharing of geographically distributed resources. This paradigm is known as Grid computing and aims to offer access to distributed resource irrespective of their physical location. Many national, European and international projects have been launched during the last years trying to explore the Grid and to change the way we are doing our everyday work. In Ireland, we have started the CosmoGrid project that is a collaborative project aimed to provide high performance super-computing environments. This will help to address complex problems such as magnetohydrodynamic outflows and jets in order to model and numerically simulate them. Indeed, the numerical modeling of plasma jets requires massive computations, due to the wide range of spatial-temporal scales involved. We present here the first jet simulations and their corresponding models that could help to understand results from laboratory experiments.     

Breeding biology of dark-bellied brent geese Branta b. bernicla in Taimyr in 1990 in the absence of arctic foxes and under favourable weather conditions

In combination with observations in spring staging and wintering grounds in western Europe, a detailed etho-ecological study of nesting dark-bellied brent geese Branta b. bernicla in western Taimyr, Krasnoyarsk, Russia, was made in 1990. Most brent geese arrived on the breeding grounds from 14–19 June and started nesting within a few days. In the study area 264 nests of breeding brent geese were found, mainly on islands but also along small rivers on the mainland. The mean clutch size was 3.0 and 80% of the eggs hatched. Time budget studies showed that incubating females spent on average 138 minutes per 24 hours on feeding. Despite favourable weather conditions and a low density of arctic foxes, only about one-third of the mature birds in the study area bred. In the autumn an intermediate breeding success of 20% juveniles was recorded in the wintering areas. This was probably due to the relatively poor condition in which the brent geese left their spring staging areas.     

From the green color of eskolaite to the red color of ruby: an X-ray absorption spectroscopy study

The best known cause for colors in insulating minerals is due to transition metal ions as impurities. As an example, Cr³⁺ is responsible for the red color of ruby (α-Al₂O₃:Cr³⁺) and the green color of eskolaite (α-Cr₂O₃). Using X-ray absorption measurements, we connect the colors of the Cr _x Al_2−x O₃ series with the structural and electronic local environment around Cr. UV–VIS electronic parameters, such as the crystal field and the Racah parameter B, are related to those deduced from the analysis of the isotropic and XMCD spectra at the Cr L_2,3-edges in Cr_0.07Al_1.93O₃ and eskolaite. The Cr–O bond lengths are extracted by EXAFS at the Cr K-edge in the whole Cr _x Al_2−x O₃ (0.07≤x< 2) solid solution series. The variation of the mean Cr–O distance between Cr_0.07Al_1.93O₃ and α-Cr₂O₃ is evaluated to be 0.01₅ Å (≈1%). The variation of the crystal field in the Cr _x Al_2−x O₃ series is discussed in relation with the variation of the averaged Cr–O distances.     

An asymptotic solution for the Trojan case of the plane elliptic restricted problem of three bodies

The planar motion of a Trojan asteroid is considered within the framework of the elliptic restricted three-body problem. The solution is derived asymptotically to second order taking the square root of the Jupiter-Sun mass ratio and the orbital eccentricity of Jupiter as first order quantities. The results are given in explicit form for the coordinates as functions of the true anomaly of Jupiter including both short and long periodic terms resulting from the orbital accentricity of Jupiter.