Diopside and Magnetite Exsolutions in Olivine from Lower Cr# Dunite in the Dongbo Ophiolite, Southern Tibet

<正>Diopside and magnetite exsolutions occur as oriented intergrowths within olivine of the lower Cr~#dunite in the Dongbo ophiolite,Tibet.The fresh lower Cr~#dunite has a mineral assemblage of olivine,spinel and diopside.The Fo content of its olivine is 90–92,which is lower than that of the higher Cr~#dunite lenses(Fo92-Fo94)without     

Flow speed and calving rate of Kongsbreen glacier, Svalbard, using SPOT images

Kongsbreen, a tide-water glacier located in Kongsfjorden, is the most active calving glacier in Svalbard. Three SPOT images are used to determine its flow speed and calving rate. The position of fourteen reference points was determined on the coast or mountain sides, and the changes in position of 144 characteristic features on the glacier surface were calculated. The obtained speed profiles arc consistent with the findings from previous works from 1962-64 and 1983-86. When comparing the obtained longitudinal profile to the data from 1962–64. it is found that the flow velocity at a given distance from the front has been nearly constant.
The results from the SPOT images analysis are completed by using existing topographic works. The present study shows that SPOT images (panchromatic as well as multichannel), recorded with a periodicity of one year, can be used to determine precisely the annual flow speed and calving rate of active glaciers such as Kongsbreen. Images recorded with a periodicity of two, three or four weeks can allow identical determination on tide-water glaciers during a surging active phase.     

ESTIMATING RATES OF DENUDATION USING COSMOGENIC ISOTOPE ABUNDANCES IN SEDIMENT

We propose, as a testable hypothesis, a basin-scale approach for interpreting the abundance of in situ produced cosmogenic isotopes, an approach which considers explicitly both the isotope and sediment flux through a drainage basin. Unlike most existing models, which are appropriate for evaluating in situproduced cosmogenic isotope abundance at discrete points on Earth's surface, our model is designed for interpreting isotope abundance in sediment. Because sediment is a mixture of materials, in favourable cases derived from throughout a drainage basin, we suggest that measured isotope abundances may reflect spatially averaged rates of erosion. We investigate the assumptions and behaviour of our model and conclude that it could provide geomorphologists with a relatively simple means by which to constrain the rate of landscape evolution if a basin is in isotopic steady state and if sampled sediments are well mixed.     

Unusual intraclastic limestones in Lower Triassic carbonates and their bearing on the aftermath of the end-Permian mass extinction

Flat pebble conglomerates were a common carbonate facies in Cambrian to Early Ordovician open marine settings, but they become extremely rare in these environments after this time. However, the Early Triassic witnessed an anachronistic reappearance of flat pebbles, together with other intraclast types, in a range of carbonate depositional settings. In south China, flat pebble conglomerates are encountered in storm-dominated, platform carbonates to deep basinal settings, while prefossilized bivalve intraclasts and flat pebbles are common in mid-ramp facies of northern Italy. The emplacement mechanisms of the intraclast-bearing beds appear to have been diverse and to have included basinal turbidity flows and storm-generated hyperconcentrated flows: true storm beds, deposited under combined flow conditions, are rare. The cause of the widespread early lithification implied by the Early Triassic intraclasts appears to have been twofold: suppression of bioturbation, allowing the preservation of thin beds, and rapid submarine lithification. Both features appear to be a response to the widespread development of benthic dysoxia/anoxia during and following the end-Permian mass extinction. This event appears to have temporarily recreated the conditions that pertained in Cambro-Ordovician shelf seas. Flat pebble conglomerates may, therefore, constitute a proxy indicator of stressed environmental conditions associated with global anoxic/dysoxic events.     

From Sustainable Development Objectives to Indicators of Progress

Local communities are adopting sustainable development goals as outlined in Agenda 21. The pressure-state-response model proposed by the OECD and adopted in Australia is extended with environmental sustainability and environmental health indicators to emphasise interaction between the bio-physical and socio-economic sub-systems. Indicators are selected with the participation of local residents to monitor sensitive local environmental concerns, to motivate change and to provide benchmarks for comparison with other areas. Partnerships are proposed to use established programmes to provide much of the data required.     

Positional uncertainty in manually digitized map data

Digital map coordinates represent the locations of real world entities. As such, differences can exist between the ‘tru’ and digital database coordinates of those entities. This paper reports on a statistical characterization of positional error in manually-digitized and map-registered point data, the relative contribution of point type and operator to digitization error, and the effects of map media type on the positional uncertainty associated with registration.

Manually-digitized point data were collected by four operators from mylar and paper maps. Point locations for a number of different feature types were sampled from United States Geological Survey (USGS) 1:24 000 scale maps. Linear models were used to estimate the variance components due to among-operator, map media, point type and registration effects. The statistical distribution of signed distance deviations for manually-digitized data was leptokurtic relative to a random normal variate. Unsigned deviations averaged 0-054 mm. Squared distance deviations were not different from a Chi-square random variate. Variance components indicate that among-operator differences in positional uncertainty were large and statistically significant, while differences among point type were small and non-significant. Signed distance deviations associated with a first-order afhne followed a normal distribution. Unsigned distance deviations associated with a first-order affinc transformation averaged 0068mm, and squared distance deviations were distributed as a Chi-square. Differences in transformation accuracy were not related to type of map media.     

ISTANBUL'S BOSTANS: A MILLENNIUM OF MARKET GARDENS*

ABSTRACT. For centuries, a network of market gardens throughout Istanbul provisioned the city with fresh vegetables. These bostans and their gardeners held a respected place in Istanbul life, contributing to the city's food and employment needs. Today, only fragments remain. Massive urban development, intense competition for metropolitan space, modernization, changing institutions and laws, and the global industrialization of food have threatened this tradition with extinction. But in spite of the overwhelming forces behind their demise, some of Istanbul's bostans persist. Efforts to support and promote the gardens, and to draw from the expertise and experience of their gardeners, are emerging. From a historical perspective, this article examines Istanbul's bostans to understand their meaning and contribution to the city's people and landscape.     

CYBERSPACE AND VIRTUAL PLACES

ABSTRACT. Computer networks are often described in terms that imply a virtual space or place: electronic frontier, cyberspace, and information superhighway have been used to indicate computer networks as a whole; cafés, dungeons, and virtual offices are some of the “places” people refer to as being in or on networks. The use of this language, which I collectively call “virtual-place metaphors,” indicates three broad metaphorical themes: virtual architecture, electronic frontier, and cyberspace. The metaphors encourage control, surveillance, and capitalist expansion through computer technologies—and also evasion and resistance through computer technologies.     

RAINFALL AND TEMPERATURE ATTRIBUTES ON THE LESOTHO–DRAKENSBERG ESCARPMENT EDGE, SOUTHERN AFRICA

Located near the southeastern limit of Africa, the Lesotho‐Drakensberg and associated escarpment is the highest range of African mountains south of the massifs in Tanzania. At the escarpment summit and on the adjacent high peaks, the climate is generally interpreted as marginal periglacial yet few data, specifically rainfall and temperature, exist on record at these altitudes. Climatic data from two temporary field stations on the escarpment edge, one of which is the highest rainfall station yet on record in southern Africa, provide contemporary surface‐climate conditions. Mean annual rainfall recorded between 2001 and 2005 averages 767.8 mm at Sani Pass summit (three complete years), and 753.2 mm on Sentinel Peak (two complete years); these values are less than those recorded for the same period in the mountain foothills. Even though rainfall is slightly below long‐term rainfall averages for the area due to a marginally dry spell, the data show that earlier estimates of between 1000 mm and 2000 mm rainfall per annum on the escarpment are too high. A measured mean air temperature of 5.8°C at Sani Pass, however, falls within the range estimated for the escarpment summit. Frost cycles in air and at the soil surface are frequent in winter, but absent in soil for summer, and no long‐duration surface‐soil freeze was measured. Temperatures thus confirm the marginal periglacial nature as postulated for previously, but precipitation data indicate a dryer environment than anticipated. Palaeoenvironmental scenarios, notably arguments for former glaciation based on extrapolations from somewhat exaggerated contemporary precipitation values, thus require re‐consideration.     

ELIMINATING COMPLEX EIGENVECTORS AND EIGENVALUES IN MULTIWAY ANALYSES USING THE DIRECT TRILINEAR DECOMPOSITION METHOD

The direct trilinear decomposition method(DTDM)is an algorithm for performing quantitative curveresolution of three-dimensional data that follow the so-called trilinear model,e.g.chromatography-spectroscopy or emission-excitation fluorescence.Under certain conditions complexeigenvalues and eigenvectors emerge when the generalized eigenproblem is solved in DTDM.Previouspublications never treated those cases.In this paper we show how similarity transformations can be usedto eliminate the imaginary part of the complex eigenvalues and eigenvectors,thereby increasing theusefulness of DTDM in practical applications.The similarity transformation technique was first used byour laboratory to solve the similar problem in the generalized rank annihilation method(GRAM).Because unique elution profiles and spectra can be derived by using data matrices from three or moresamples simultaneously,DTDM with similarity transformations is more efficient than GRAM in the casewhere there are many samples to be investigated.