Calcretes of Olduvai Gorge and the Ndolanya Beds of northern Tanzania

Pedogenic calcretes are closely associated with Pliocene to Holocene wind-worked deposits of volcanic ash in the Olduvai and Ndolanya Beds of northern Tanzania. The typical profile with calcrete consists of an unconsolidated sediment layer, an underlying laminar calcrete, and a lowermost massive calcrete. The laminar calcrete is a relatively pure limestone, whereas massive calcrete is aeolian tuff cemented and replaced by calcite. An Olduvai calcrete profile can develop to a mature stage in only a few thousand years. Carbonatite ash was the dominant source for most of the calcite in the calcretes. Replacement was a major process in formation of the massive calcretes, and oolitic textures have resulted from micrite replacing pelletoid clay coatings around sand grains. Phillipsite and possible other zeolites were extensively replaced in the massive calcretes. Replacement of clay by micrite in the Olduvai calcretes is accompanied by dissolution or leaching of phengitic illite and the formation of clay approaching the composition of halloysite or kaolinite. In the upper calcrete of the Ndolanya Beds, montmorillonite was altered to a kaolinite-type mineral and to dioctahedral chlorite. Authigenic dolomite, zeolite, and dawsonite in the Olduvai calcretes probably received at least some of their components from replaced materials.     

Micro-zircon: origin and evolution during metamorphism

The size and distribution of zircon within a garnet-mica-schist from the Scottish Highlands were assessed using scanning electron microscopy. The study reveals that abundant 0.2–3.0 μm sized zircon is preferentially concentrated within garnet and biotite porphyroblasts. The micro-zircon has grown during regional metamorphism and represents >90% of the total number of zircon in the schist. It is texturally distinct from a few larger detrital zircon grains in the schist that commonly preserve evidence of dissolution, and more rarely, small metamorphic outgrowths. The sequential incorporation of zircon in porphyroblasts allows prograde changes in the morphology of the zircon population to be identified. Zircon is reactive and soluble, and responds to medium-grade metamorphism in a series of dissolution and crystallization events, linked to possible changes in fluid composition. Deformation also has a significant influence on the distribution of zircon, allowing inclusions previously trapped within biotite to react. About 8 × 10⁶ micro-zircon occur as inclusions within a typical individual 5-mm garnet porphyroblast and their presence must be considered prior to trace-element or isotopic analysis of such metamorphic phases.     

The Recreational Value of In-Stream Flows

The decision in 1988 by the Rangitikei-Wanganui Catchment Board to allocate flows away from use for electricity generation into recreation use brought into focus the conflict between market and non-market valuation of river uses. The travel cost method (TCM) of non-market valuation is used to estimate the in-stream recreation values of the Upper Wanganui and Whakapapa rivers.     

Normal fault zone evolution and fault scarp degradation in the Aegean region

Abstract The initial stages of rift-basin evolution are periods of great landform change. Fault scarps are newly created axes of erosion which, along with footwall uplands, act as sediment sources for subsiding hanging wall basins. Scarps formed during neotectonic normal faulting of Mesozoic carbonates in mainland Greece and western Turkey display a varied pattern of degradation related to the history of fault development and variations in fault zone architecture. Alternating zone-parallel compact breccia sheets and incohesive breccia belts, of contrasting resistance to erosion, underlie scarps. Meso-scale slip-plane phenomena, such as corrugations, gutters, comb fractures, and pluck holes, together with geomorphological features, such as subsurface solution pipes, and vegetation result in initial variations in the denudability of erosionally resistant compact breccia sheets. Migration with time of slip-plane activity within a fault zone into its hanging wall (i.e. intrafault-zone hanging wall collapse) adds to the structural heterogeneity of fault scarp footwalls. Quaternary talus, whether offset across a fault, banked unconformably against a slip plane, or faulted against a reactivated slip plane, has a dampening effect on degradation. The complexities of fault zone architecture combined with a history of hanging wall collapse lead, in the Aegean region, to non-uniform degradation and scarps which are commonly stepped and occasionally cavitated.     

Zircon alteration,formation and preservation in sandstones

Zircon textures, chemistry and microstructures have been characterized in situ within Carboniferous sandstones from the Midland Valley of Scotland using back‐scattered electron and cathodoluminescence images, electron backscatter diffraction techniques and chemical analyses. The study of polished thin sections reveals a variety of zircon types including unmodified detrital zircon, zircon outgrowths and different forms of modified zircon that formed in low‐temperature conditions within the sedimentary rocks. These rocks have only experienced temperatures of <100 °C during burial; however, altered zircon is abundant and characterized by a low mean atomic number, with relatively high contents of non‐formula elements and a nano‐crystalline or microcrystalline structure. It forms by replacement of detrital zircon that subsequently became metamict. Two types of replacement mechanisms are effective in sedimentary environments and involve either dissolution–reprecipitation or solid‐state reaction, but both require fluid access to the radiation‐damaged areas. The former process appears to become the dominant replacement mechanism as temperature increases and produces highly porous, inclusion‐rich zircon. Metamict zircon is extremely reactive in near‐surface conditions and the production of low‐temperature zircon is sensitive to both parent zircon characteristics and environmental conditions. As such, the alteration of zircon has the potential to yield unique information on the diagenetic history of sedimentary rocks. Low‐temperature zircon would be unlikely to survive sedimentary transport or the rock crushing procedures that characterize many investigations of detrital zircon populations and consequently may generate severe biases in studies of this type.     

对人文科学所遭受抨击的回应

长期以来,不少人站在功利角度,对人文科学进行了颇多抨击。本文意欲对此做出有理有据的反击。首先,文章概述了人文科学在政界、民间和实践领域所遭受的非议,并寻找出主要的批评者及其拥护者。其次,作为申辩内容的一部分,本文详细阐述了人文学科的核心优势。这些优势涵盖了哲学和实用科学领域,包括为知识创造提供批判性视角,使生活丰富多彩,培养应对未来不确定性和复杂性的技能,以及增强理性和维持大学机构的收入和信誉度。最后,本文提出人文学者不仅要开展相关学科里非常重要的理论和实证研究,还必须将捍卫和保护人文科学纳入到专业活动中来。     

Atmospheric Effects of the Emerging Mainland Chinese Transportation System at and Beyond the Regional Scale

Local surface travel needs in the Peoples Republic of China (mainlandChina) have traditionally been met largely by nonpolluting bicycles. A majorautomobile manufacturing/importing effort has begun in the country over thelast decade, and planning documents indicate that the Chinese may strive toacquire more than 100 million vehicles early in the next century. By analogywith large automotive fleets already existing in the western world, bothregional and global scale pollution effects are to be expected from theincrease. The present work adopts the latest projections of Chinese automobilemanufacture and performs some quantitative assessments of the extent ofpollution generation.Focus for the investigation is placed upon the oxidant ozone. Emissions of theprecursor species nitrogen oxides and volatile organics are constructed basedon data for the current automotive sector in the eastern portion of the UnitedStates. Ozone production is first estimated from measured values forcontinental/oceanic scale yields relative to precursor oxidation. Theestimates are then corroborated through idealized two dimensional modeling ofthe photochemistry taking place in springtime air flow off the Asian land massand toward the Pacific Ocean. The projected fleet sizes could increase coastaland remote oceanic ozone concentrations by tens of parts per billion (ppb)in the lower troposphere. Influences on the tropospheric aerosol system andon the major greenhouse gas carbon dioxide are treated peripherally. Nitrogenoxides created during the vehicular internal combustion process willcontribute to nitrate pollution levels measured in the open Pacific. Thepotential for soot and fugitive dust increases should be considered as theautomotive infrastructure develops. Since the emerging Chinese automotivetransportation system will represent a substantial addition to the globalfleet and all the carbon in gasoline is eventually oxidized completely, asignificant rise in global carbon dioxide inputs will ensue as well.Some policy issues are treated preliminary. The assumption is made thatalterations to regional oxidant/aerosol systems and to terrestrial climate areconceivable. The likelihood that the Chinese can achieve the latest vehiclefleet goals is discussed, from the points of view of new production, positivepollution feedbacks from a growing automobile industry, and known petroleumreserves. Vehicular fuel and maintenance options lying before the Chinese areoutlines and compared. To provide some perspective on the magnitude of theenvironmental changes associated with an Asian automotive buildup, recentestimates of the effects of future air traffic over the Pacific Rim aredescribed.     

Shaken, Not Stirred

In a remarkable and yet largely unheralded piece off legislation, the New Zealand government has reshaped national provisions for earthquake insurance. Three major sets off issues emerge from the 1993 Earthquake Commission Act and warrant detailed investigation. The A ct will encourage significant changes in patterns of regional development in New Zealand, it heralds a simultaneous globalisation and localisation of earthquake risk through the mechanism of insurance and it gives new regulatory powers to insurers in New Zealand society.