NEW SPECIMENS FROM THE FAUCETT,MISSOURI, METEORITE LOCALITY

In December, 1966, Brookins and Twiss reported the finding of two specimens of an olivine-bronzite chondrite near Faucett, Missouri. Since that date, six additional specimens have been found. Another probable specimen was found but later lost. This paper describes the circumstances of all nine finds and presents a map of the discovery sites.     

Kimberlite AT-56: a mantle sample from the north central Superior craton, Canada

Kimberlite AT-56, discovered in February 2001, represents the most recent addition to the Attawapiskat kimberlite cluster, located in the James Bay Lowlands of Ontario, Canada. AT-56 is a small kimberlite body with a surface diameter of approximately 40 m and a steep southeastern plunge. It consists of a medium to coarse-grained matrix supported kimberlite with abundant olivine, clinopyroxene, garnet, ilmenite and mica macrocrysts in a green-black to orange-black matrix. The kimberlite is classified as a hypabyssal facies sparsely macrocrystic calcite kimberlite. Heavy mineral concentrates from two representative samples of AT-56 have been analyzed to characterize the mantle sampled by the kimberlite. Both samples yielded large heavy mineral concentrates comprised of roughly equal proportions of Mg-ilmenite, Cr-diopside, high-Cr garnet and low-Cr garnet. Mg-chromite is also present in quantities an order of magnitude less than the other constituents.

The high-Cr peridotitic garnet macrocrysts are only slightly more abundant than the low-Cr varieties, the population being dominated by G9 (lherzolitic) types with only a few (less than 10%) weakly sub-calcic G10 (probable harzburgitic) garnets present. Ni thermometry results for a representative selection of G9 and G10 garnets indicate that the majority equilibrated at temperatures ranging from 1000 to 1250 °C. A significant proportion of the low-Cr garnet population derived from AT-56 is characterized by relatively low-Ti (0.2 to 0.4 wt.% TiO₂) and elevated Na (0.07 to 0.13 wt.% Na₂O) contents characteristic of Group 1, diamond inclusion type eclogite garnets. These sodic garnets have elevated Cr₂O₃ contents (typically 1 to 2 wt.% Cr₂O₃), suggesting they may be websteritic in origin rather than eclogitic. Comparison of AT-56 garnet compositions with published data available for other Attawapiskat kimberlites suggests websteritic mantle has also been sampled by kimberlite bodies elsewhere in the Attawapiskat cluster and it may be an important diamond reservoir in this area.     

Aerobic landfill test cells and their implications for sustainable waste disposal

Municipal Solid Waste (MSW) landfills world-wide are experiencing the consequences of conventional landfilling techniques, whereby anaerobic conditions are created within the landfill waste. Under anaerobic conditions, slow stabilization of the waste mass occurs, producing methane, (an explosive, 'greenhouse' gas) and toxic leachate over long periods of time. As a potential solution, it was demonstrated that the aerobic degradation of MSW within a landfill can significantly increase the rate of waste decomposition and settlement, decrease the production of methane gas, reduce the level of toxic organics in the leachate and decrease quantities of landfill leachate that need treatment. This paper summarizes the successful results of two separate aerobic landfill projects located in Georgia (USA) and discusses the potential economic and environmental impacts to world-wide solid waste management.     

Distinctive microbial structures and the pre-phanerozoic fossil record

The live and sedimentary components of the flat laminated microbial mat at Laguna Figueroa have been studied since the late sixties. This paper reports the observation and isolation of a variety of micro-organisms, both prokaryotes and eukaryotes. The microbes were taken from the flat laminated mats submerged under at least one meter of water due to the spring rains of 1979 and 1980. Both in situ and enrichment culture observations were made using light and electron microscopic techniques. New strains of the following microbes are reported here: Bacillus megaterium, Bacillus licheniformis, Arthrobacter simplex and Paratetramitus jugosus. Several pseudomonads were isolated, some of which form distinctive subsurface colonial structures. Regular distinctive colony morphologies and desiccation resistant cysts were often observed, several types of which grow to characteristically large sizes and resemble objects found in the pre-Phanerozoic fossil record.Some colonies of manganese oxidizing bacilli and other bacteria are reminiscent of microfossils of the 2 Ga-old Gunflint Iron formation such as Metallogenium, Eosphaera tyleri, Eoastrion and Huronispora. Some manganese oxidizing bacteria form colonial structures that might be mistaken for individual organisms in the tens to hundreds of microns size range. The diversity of microbial structures, including those with preservation potential, must be kept in mind when interpreting the microfossil record.     

THE RANSOM METEORITES

A number of stony meteorite specimens, presumably from a single fall, have been recovered from an area about 5–6 miles north of Ransom, Kansas. This paper presents a map of discovery locations, so far as known. Megascopic appearance, external and internal, of a typical (?) specimen is described. The Ransom meteorite has already been classified as an olivine-bronzite chondrite — chemical group H of Van Schmus and Wood. Features observed in thin section are characteristic of petrologic type 4     

Gravel bedforms in the West Solent, Southern England

Data is presented on distinctive gravel bedforms which occur in the tidal marine environment of the west Solent in Southern England. Discrete zones of gravel waves of different sizes and flat bed gravel occur in similar depths and hydrodynamic conditions. In the absence of comparable field data the conclusions are related to flume data: a purely physical explanation is not obvious and requires more detailed hydrodynamic data. It is considered that other factors such as availability of mobile sediment and biological accretion may be important influences.     

An experimental investigation of blocking by partial barriers in a rotating baroclinic annulus

We present a series of experimental investigations in which a differentially-heated annulus was used to investigate the effects of topography on rotating, stratified flows with similarities to the Earth’s atmospheric or oceanic circulation. In particular, we compare and investigate blocking effects via partial mechanical barriers to previous experiments by the authors utilising azimuthally-periodic topography. The mechanical obstacle used was an isolated ridge, forming a partial barrier, employed to study the difference between partially blocked and fully unblocked flow. The topography was found to lead to the formation of bottom-trapped waves, as well as impacting the circulation at a level much higher than the top of the ridge. This produced a unique flow structure when the drifting flow and the topography interacted in the form of an “interference” regime at low Taylor number, but forming an erratic “irregular” regime at higher Taylor number. The results also showed evidence of resonant wave-triads, similar to those noted with periodic wavenumber-3 topography by Marshall and Read (Geophys. Astrophys. Fluid Dyn., 2015, 109), though the component wavenumbers of the wave-triads and their impact on the flow were found to depend on the topography in question. With periodic topography, wave-triads were found to occur between both the baroclinic and barotropic components of the zonal wavenumber-3 mode and the wavenumber-6 baroclinic component, whereas with the partial barrier two nonlinear resonant wave-triads were noted, each sharing a common wavenumber-1 mode.