Agronomic impact of tephra fallout from the 1995 and 1996 Ruapehu Volcano eruptions, New Zealand

 Eruptions from Ruapehu Volcano on 11 and 14 October 1995 and 17 June 1996 distributed at least 36×10⁶ m³ of sulphur(S)-rich tephra over the central and eastern North Island of New Zealand. The tephras added between 30–1500 kg ha^–1 S to at least 25 000 km² of land in primary production. Smaller but beneficial amounts of selenium (Se) and in some areas potassium and magnesium were also supplied. Addition of S to the soils in the form of sulphate and elemental S resulted in a drop in soil pH and an increase in pasture S contents within seven weeks of the eruptions. The soils affected by the tephra are naturally low in S and Se, but following the eruptions S was not required in fertilizer applications in many areas. The strongest and longest lasting effects of S and Se deposition were in high anion-retention soils particularly Hapludands (moist, moderately weathered soils, derived from volcanic ash). Soluble fluorine concentrations within the tephras were low compared to historic Icelandic and Chilean examples. However, pastoral livestock deaths were apparently caused by fluorosis in addition to starvation when tephra covered feed. The Ruapehu tephra contained very low concentrations of other soluble toxic elements. Received: 17 January 1997 · Accepted: 31 March 1997     

Methane distribution and cycling in Tomales Bay, California

Cycling of methane (CH₄) in Tomales Bay, a 28-km² temperature estuary in northern California with relatively low inputs of organic carbon, was studied over a 1-yr period. Water column CH₄ concentrations showed spatial and temporal variability (range=8–100 nM), and were supersaturated with respect to the atmosphere by a factor of 2–37. Rates of net water column CH₄ production-oxidation were determined by in situ experiments, and were not found to be significantly different from zero. Fluxes across the sediment-water interface, determined by direct measurement using benthic chambers, varied from ?0.1 μmol m^?2 d^?1 to +16 μmol m^?2 d^?1 (positive fluxes into water). Methane concentrations in the two perennial creeks feeding the bay varied annually (140–950 nM); these creeks were a significant CH₄ source to the bay during winter. In addition, mass-balance calculations indicate a significant additional inter CH₄ source, which is hypothesized to result from storm-related runoff from dairy farms adjacent to the bay. Systemwide CH₄ budgets of the 16-km² inner bay indicate benthic production (110 mol d^?1) and atmospheric evasion (110 mol d^?1) dominated during summer, while atmospheric evasion (160 mol d^?1) and runoff from dairy farms (90 mol d^?1) dominated during winter.     

Late Devensian ice sheet characteristics: a palaeohydraulic approach

Glacial meltwater channels are incised into bedrock and diamicton along much of the length of the Mid-Cheshire Ridge. Detailed mapping of one such system near the town of Helsby reveals a dendritic channel network developed in the opposite direction to the regional ice flow during the last (Late Devensian) glaciation. The channels formed subglacially, under atmospheric and not hydrostatic pressure, presumably as the ice sheet downwasted during deglaciation. Morphological and palaeohydraulic evidence suggests that not all of the network was necessarily active contemporaneously. Former water levels in the channels can be estimated due to the presence of bar surfaces, giving a calculated palaeodischarge of at least 111 m³ s⁻¹. The ablation rates required to account for this large discharge are an order of magnitude greater than those obtained from theoretical calculations and those observed in modern glacial environments. This implies that some form of high-magnitude discharge, such as a seasonal flood event, must have taken place in this area during deglaciation. This picture of the Late Devensian ice sheet suggests that during recession the ice sheet was static, crevassed and relatively thin (<50 m). This study also shows that there is no simple relationship between meltwater channel direction and ice dynamics, and that care is required when using the former to make inferences about the latter. Copyright © 1998 John Wiley & Sons, Ltd.     

Geochemical studies in the Indian Pass and Picacho Peak Bureau of Land Management Wilderness study areas, imperial county, Southern California

The U.S. Geological Survey has conducted geochemical studies in the Indian Pass (CDCA-355), 124 km², and Picacho Peak (CDCA-355A), 23 km², Wilderness Study Areas (WSA's) as part of a program to evaluate the mineral resource potential of designated areas in the California Desert Conservation Area. These two WSA's are of particular interest because they lie within a region which has intermittently produced significant quantities of Au since the mid-1800's, and is currently the site of much exploration activity for additional Au resources. Within a 15-km radius of the WSA's, there is one actively producing gold mine, a major deposit which began production in 1986, and one recently announced discovery. In the reconnaissance geochemical surveys of the two WSA's - 177 μm (-80 mesh) stream sediments, heavy-mineral concentrates from stream sediments, and rocks were prepared and analyzed.Four areas of possible exploration interest were identified within the WSA's. The first area is characterized by anomalous W and Bi in nonmagnetic heavy-mineral concentrates, and is underlain primarily by the Mesozoic Orocopia Schist which has been intruded by monzogranite of Oligocene age. Alteration and mineralization appear to be localized near the intrusive contact. The mineralized rock at the surface contains secondary Cu and Fe minerals where the monzogranite intrudes the metabasite horizons of the Orocopia Schist and scheelite where the monzogranite intrudes marble within the Orocopia Schist.The second area is characterized by anomalous As, Sb, Ba, B, and Sr in nonmagnetic heavy-mineral concentrates and by anomalous As in - 177 μm stream sediments. Geologically, this area is underlain by metasedimentary and metavolcanic rocks of Jurassic(?) age; a biotite monzogranite of Jurassic(?) age; and Tertiary volcanic and hypabyssal rocks composed of flows, domes, and tuffs of intermediate to silicic composition. All these rock types are cut by a set of north-south-striking normal faults. The anomalies in the heavy-mineral concentrates are believed to be related to silica-clay alteration observed in the vicinity of some of these faults.     

Extragalactic integral field spectroscopy on the Gemini telescopes

We have been undertaking a programme on the Gemini 8‐m telescopes to demonstrate the power of integral field spectroscopy, using the optical GMOS spectrograph, and the new CIRPASS instrument in the near‐infrared. Here we present some preliminary results from 3D spectroscopy of extra‐galactic objects, mapping the emission lines in a 3CR radio galaxy and in a gravitationally lensed arc, exploring dark matter sub‐structure through observations of an Einstein Cross gravitational lens, and the star formation time‐scales of young massive clusters in the starburst galaxy NGC 1140. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Evaluation of Geochemical Reference Standards by X-Ray Fluorescence Analysis

Twenty five elements in twenty six geochemical reference standards analyzed by X-ray fluorescence spectrometry yield major and trace element concentrations close to consensus values. Ninety percent of our analyses agree with consensus values for standards to within pm 0.5 to 1.5 relative percent for major elements and pm 3 to 5 relative percent or pm 1-3 ppm, whichever is higher, for trace elements. Consistent divergences from consensus values of trace elements are noted.     

The relationship between anomalies of interannual net radiation and 37 GHz polarization difference over North Africa

We show evidence that interannual variations in the net radiation balance at the top-of-atmosphere over North Africa may be linked to variations at the land surface within the Sahelian zone. By utilizing concurrent monthly time series of earth radiation budget and passive microwave measurements obtained from the Nimbus 7 satellite over a five year period from 1979 to 1983, we have examined the spatial distribution of the amplitude of interannual variability of the net radiation at the top of the atmosphere. A strong association is found between the radiation budget anomalies derived from ERB-WFOV measurements and the anomalies of 37 GHz polarized brightness temperature difference derived from SMMR measurements. Previous research has shown that the interannual anomalies in the top-of-atmosphere net radiation balance in the Sahelian zone mostly arise from changes taking place at the surface, not from variations in cloudiness which brings variable rainfall throughout the African Sahel. Since microwave polarization difference is related in part to vegetation cover, we suggest that the main control of the modulation of North Africa's radiation balance may be year to year fluctuations of vegetation cover within the Sahelian zone, likely stemming from fluctuations in the rainfall. This relationship is relevant to the problem of radiation control and feedback on global climate through processes taking place within the biosphere of a semi-arid zone.     

Urban mental maps and housing estate preferences of council tenants

This paper offers an exploratory examination of the urban mental maps and housing estate preferences of council tenants. The study area is the council housing market of the city of Birmingham. The data are based on an interview survey of transfer applicants on six Birmingham ‘study estates’ which provide contrasts in terms of age and location. The findings generally offer support for J.S. Adams' sectoral mental maps hypothesis, although important differences are disclosed among the familiarity spaces of tenant groups defined on the basis of the study estates. The results are also suggestive of a general sharpening of preferences for council estates located inside the home sector, with tenants expressing a net preference for older suburban housing areas. Conversely, the least popular estates are located in the inner/middle rings of the city and characterized by relatively large concentrations of New Commonwealth immigrants.     

Syngenetic inclusions of yimengite in diamond from Sese kimberlite (Zimbabwe) — evidence for metasomatic conditions of growth

Syngenetic inclusions of yimengite K (Cr, Ti, Mg, Fe, Al)₁₂O₁₉, a potassium member of the magnetoplumbite mineral group, have been recorded in an octahedral macrodiamond from the Sese kimberlite (50 km south of Masvingo, Zimbabwe). One yimengite inclusion carries lamellae of chromite suggesting peridotitic diamond paragenesis. The diamond and inclusions were studied in situ in a plate polished parallel to (011). Cathodoluminescence (CL) imaging has shown blue colour and octahedral zonation of the diamond, lack of cracks and the location of five yimengites in different growth zones. Nitrogen (N) contents (at. ppm) in the diamond determined by Fourier transform infrared spectroscopy (FTIR) steadily decrease from 576 (core) to 146 (rim). N aggregation (%1aB) is correspondingly 40% in the core and 30% in the rim. Hydrogen (H) content is high in the core, moderate in the intermediate and very high in the rim zones. Four yimengites were dated using the laser ⁴⁰Ar/³⁹Ar method. Three inclusions yielded total gas ages that agree with, or are younger than, or within error of, the Sese kimberlite eruption age (538±11 Ma) but may be compromised by gas loss. One inclusion, with the highest tapped interface gas yield, gave a total gas age of 892±21 Ma that is a likely minimum yimengite age. Time–T °C constraints from N aggregation systematics give a range of possible ages from kimberlite eruption date back to Archean and do not resolve the variable results of the ⁴⁰Ar/³⁹Ar dating. Compared with the published chemistry of yimengite from kimberlites, inclusions from the Sese diamond contain higher Al, Mg, and Sr and have lower concentration of Fe³⁺. The chondrite-normalised REE pattern of the yimengite shows enrichment in LREE and depletion in HREE, but LREE/HREE fractionations are lower than for lindsleyite–mathiasite series mantle titanates and rather similar to the REE concentrations in kimberlite and lamproite rocks. It is suggested that Sese yimengite formed in the lithospheric mantle from metasomatism of chrome spinel by a fluid rich in Ti, K, Ba and LREE.     

Isotopic composition of carbon and oxygen in desert fauna: investigations into the effects of diet, physiology, and seasonality

Carbon and oxygen isotope ratios of bone apatite were measured in 14 endothermic and ectothermic vertebrates native to the Chihuahuan Desert and collected in June and July of 1999 and 2000. The δ⁸O values of most reptiles were very high, up to 44‰ (standard mean ocean water (SMOW), some of the highestδ¹⁸ O values ever measured for an animal. The δ¹⁸O values of rodents and birds were lower (32±5‰ vSMOW), and the earless lizard Holbrookia maculata were the lowest of all species analysed (25‰). Omnivorous grasshopper mice (Onychomys torridus) had lower δ¹⁸O values than granivorous rodents. Results from oxygen analysis likely reflect variation in diet and body water flux differences between endotherms and ectotherms. Carbon isotope analysis revealed a dramatic shift in diet from C₃ plants in 1999 to C₄ plants in 2000 in most rodents and birds. Kangaroo rats and reptiles did not change, having a constantδ¹³ C value indicative of a C₃-based diet in both years. This suggests reliance on winter annual plant seed caches for kangaroo rats, but not other rodents. The carbon isotope data can be explained in terms of seasonal differences within and between years in the timing and intensity of the seasonal rainfall events, and the productivity of summer and winter annual plants. This study illustrates that stable isotope analysis is a powerful method for tracking dietary change and feeding behavior in desert vertebrates.