Response to urbanization of the avon-heathcote estuary,christchurch, New Zealand

The Avon-Heathcote is a small, microtidal, predominantly intertidal, weather-dominated estuary. It has experienced large alterations to its physical environment as a result of the establishment and growth the adjacent Christchurch City, on what was previously a swampy, dune-bordered coastal plain. During the first 25 years of settlement the volume of the tidal compartment of the estuary decreased from 7.7 × 10⁶ m³ to about 5 × 10⁶ m³. A combination of rapid drain laying in the 1880s and 1890s and the conversion of much of the catchment of the estuary to urban uses altered the sediment yields and runoff characteristics of the area and resulted in a reversal of the early trend. By 1925 the tidal compartment had returned to its original volume, and by 1975 it had reached a volume of 10.93 × 10⁶ m³. The early decrease was accompanied by widespread deposition of a 30–60 cm thick layer of muddy sediment, some of which remains. The estuary inlet underwent major adjustments to accomodate the increasing tidal flow and now appears to be approaching a new, posturban equilibrium.     

Observations of fluxes over heterogeneous surfaces

This study analyzes data collected from repeated aircraft runs 30 m over alternating regions of irrigated and dry nonirrigated surfaces, each region on the order of 10 km across, during the California Ozone Deposition Experiment (CODE). After studying the scale dependence of the flow, the variables and their fluxes are decomposed into means for sublegs defined in terms of irrigated and nonirrigated regions and deviations from such subleg means. Since the repeated runs were flown over the same track, compositing the eight flight legs for each of the two days allows partial isolation of the influences of surface heterogeneity and transient mesoscale motions.A variance analysis is carried out to quantify the relative importance of surface heterogeneity and transient mesoscale motions on the variability of the turbulence fluxes. The momentum and ozone fluxes are more influenced by transient mesoscale motions while fluxes of heat, moisture and carbon dioxide are more influenced by surface heterogeneity. The momentum field is also influenced by a quasi-stationary mesoscale front and larger scale velocity gradients.For the present case, the mesoscale modulation of the turbulent flux is numerically more important than the direct mesoscale flux. This spatial modulation of the turbulent fluxes leads to extra Reynolds terms which act to reduce the area-averaged turbulent momentum flux and enhance the area-averaged turbulent heat flux.     

The anomalous intensities of helium lines in a coronal hole

Observations made at the quiet Sun-centre with the Coronal Diagnostic Spectrometer (CDS) and Solar Ultraviolet Measurements of Emitted Radiation (SUMER) instruments on the Solar and Heliospheric Observatory ( SOHO ) have shown that the intensities of the resonance lines of He  i and He  ii are significantly larger than predicted by emission measure distributions found from other transition region lines. The intensities of the helium lines are observed to be lower in coronal holes than in the quiet Sun. Any theory proposed to account for the behaviour of the helium lines must explain the observations of both the quiet Sun and coronal holes. We use observations made with SOHO to find the physical conditions in a polar coronal hole. The electron pressure is found using the C  iii 1175-Å and N  iii 991.5-Å lines, as the C  iii line at 977.0 Å becomes optically thick in some regions at high latitudes. The mean electron pressure is a factor of ≃2 lower than that at the quiet Sun-centre. The mean coronal electron temperature is     . The helium lines are enhanced with respect to other transition region lines but by factors which are ≃ 30 per cent smaller than at the quiet Sun-centre. The mean ratios of the intensities of the He  i 537.0- and 584.3-Å lines and of the He  i and He  ii 303.8-Å lines vary little with the type of region studied. These ratios are compared with those predicted by models of the transition region, taking into account the radiative transfer in the helium lines. No significant variation is found in the relative abundances of carbon and silicon.     

Wisconsinan Late-glacial environmental change in Newfoundland: A regional review

The distribution of 75 lake and bog sites, from which pollen stratigraphical evidence relevant to the late Quaternary of Newfoundland has been obtained, is presented. The detailed records of lithology, pollen and diatoms, supplemented by geochemical data, are discussed for three of the sites — Southwest Brook Lake, Woody Hill Brook Pond and Leading Tickles — and interpretations made are based on vegetational history, relative climatic changes and extent of ice cover. Radiocarbon data from 14 sites are summarised. A summary chart of Late-glacial environmental changes, including a qualitative palaeotemperature curve, is provided.     

Aircraft measurements of CO2 exchange over various ecosystems

The National Aeronautical Establishment's Twin Otter Atmospheric Research Aircraft has been equipped with open-path CO₂ analyzers in order to obtain estimates of CO₂ exchange over a corn field, a forest and a lake using the eddy correlation technique. On the 18th of August 1980, mean uptakes obtained over corn and forest were 12 and 8 kg CO₂ ha^-1 hr^-1, respectively. On the 28th of August, mean uptakes obtained over corn, forest and the lake were 36, 14, and 1 kg CO₂ ha^-1 hr^-1, respectively. The data are discussed in the light of general conditions on the two days.     

Oxygen isotope geochemistry of lavas from an oceanic to continental arc transition, Kermadec–Hikurangi margin, SW Pacific

New oxygen isotope data are presented for submarine lavas erupted close to the transition between the oceanic Kermadec island arc and the continental Taupo Volcanic Zone, New Zealand. Volcanic glasses display δ¹⁸O values ranging from +5.65‰ to +5.83‰, clinopyroxenes range from +5.23‰ to +5.78‰ and olivines range from +4.83‰ to +5.47‰. Coexisting glass and phenocrysts in the lavas are in isotopic equilibrium, with one exception. Oxygen isotope ratios of back-arc lavas erupted through oceanic crust are indistinguishable from mid-ocean ridge basalts or lavas erupted in nearby back-arc settings. Although lavas from the arc front display elevated oxygen isotope ratios, the magnitude of ¹⁸O-enrichment is too great to result from recycling of subducted material alone. A single back-arc lava erupted through continental crust is also relatively ¹⁸O-rich suggesting that the most likely origin for the high δ¹⁸O signature is limited amounts of interaction between continental crust and melts derived from a mantle wedge that has been variably fluxed by recycled oxygen. The results of modelling open system behaviour in this volcanic system highlight the need for strong controls on the composition of local contaminants. Application of ‘average' crustal lithologies, as in other volcanic provinces, may lead to erroneous conclusions regarding the involvement of local basement.     

“Fluffy” Type A Ca-, Al-rich inclusions in the Allende meteorite

Allende “fluffy” Type A's (FTA's) are a distinct sub-group of Ca-, Al-rich inclusions whose primary mineral assemblage consists of Al-rich melilite (Åk 0–33), spinel that is commonly very V-rich, perovskite and, frequently, hibonite. Some contain relatively coarse-grained melilite (up to 1.5 mm) that is intensely kink-banded and commonly reversely-zoned, hibonite and V-rich spinel. Others contain much finer-grained and strain-free melilite (?50 μm) and have not been found to contain hibonite or V-rich spinel. Some FTA's contain both coarser- and finer-grained melilite and textural relationships indicate that the latter is replacing the former. FTA's are characterized by extremely irregular shapes and 60–75 volume per cent of fine-grained, secondary alteration products. Many are aggregates of innumerable nodules, each of which is surrounded by a Wark-Lovering-type rim sequence. These nodules are frequently separated from one another by matrix-like clastic rim material. Other FTA's do not have nodular structure. Structural and mineralogical characteristics of their Wark-Lovering rims suggest that FTA's did not achieve their shapes by deformation of a liquid or a hot, plastic solid. In contrast to those in Type B inclusions, formation of reverse zoning in the coarser-grained melilite crystals in FTA's cannot be understood in terms of crystallization from a liquid but are readily explainable by condensation from a solar nebular gas during a period of falling pressure. Further evidence against a liquid origin is the wide range of spinel compositions within individual coarser-grained FTA's. The fact that the reversely-zoned melilite crystals cannot have been produced in any kind of sublimation or distillation process precludes formation of these inclusions as volatilization residues. FTA's are aggregates in some of which are preserved vapor-solid condensate grains that formed at high temperature in the solar nebula.     

西秦岭勉略带陆内构造变形研究

秦岭造山带勉略缝合带是古特提斯洋盆向北俯冲形成的华北与华南最后拼接带。这个主缝合带俯冲-碰撞过程中以由北向南的一系列韧性逆冲推覆构造为特征,形成由前泥盆系、泥盆-石炭系和蛇绿混杂岩等不同构造岩片叠置的复杂构造带,碰撞时代从245Ma一直延续到230Ma左右。最近,作者对勉略缝合带内发育的韧性和脆性左行走滑剪切变形进行了研究,结果表明这些顺造山带的左行韧性走滑剪切变形带的变形时代为223±2Ma,与碰撞后花岗岩所确定的碰撞后构造环境的起始时间(225Ma)一致,显示这些韧性走滑剪切变形带是勉略带陆内变形初期变形产物。亦即华北、扬子大陆碰撞之后很快就转入陆内变形阶段,并且是以顺造山带的侧向走滑位移为主要变形方式。勉略带内顺造山带的脆性左行走滑断层的发育,表明这种顺造山带的侧向位移过程从深部到地壳浅层是一致的。因此,大陆碰撞在直接碰撞之后很快转变为顺造山带的侧向走滑位移为主的陆内变形,这种位移可能表现为两个大陆碰撞后的相对走滑,或是碰撞带中强烈变形部分顺造山带的侧向挤出,从而消减了正向碰撞所造成的地壳缩短和增厚。     

西藏丁青弧前蛇绿岩的地球化学特征

丁青蛇绿岩位于班化湖－丁青－怒江蛇绿岩带的东段，其地幔岩出露规模是该带中最大的。本文报道的丁青蛇绿岩主要由地幔橄榄岩、堆晶岩、辉长岩和斜长花岗岩组成。蛇绿岩剖面上覆硅岩中的放射虫化石是早株罗世和晚三叠世诺利克期的，中侏罗统砂岩和砾岩不整合覆盖在蛇绿岩之上，由此确定丁青蛇绿岩是晚三叠－早侏罗世的，在中株罗世之前侵位，丁青蛇绿岩属于玻安岩系，玻安岩的特点是富Si、Mg和大离子亲石元素（LILE），贫高场强元素（Ti、P、Zr、Y、Yb和Nb）。丁青蛇绿岩的堆晶岩、辉长岩和辉绿岩均具“U”型REE分布，暗示丁青玻安岩是由于亏损的地幔源岩和来自消减带的水和流体两组分的混合形成的。丁青玻安岩的地球化学特征类似西太平洋第三纪玻安岩，而明显不同于MORB的地球化学性质， 表明丁青玻安岩应当形成于洋内岛弧的弧前环境，属于弧前蛇绿岩。     

Mapping mountain areas: learning from Global,European and Norwegian perspectives

Defining the spatial extent of mountain areas has long been a challenge. In the present century, the availability of digital elevation models(DEMs) incorporated into geographic information systems(GIS) has allowed the definition of mountain areas based on topographic and other criteria. This paper presents the various delineations of mountains that have been prepared at three scales – global, regional(Europe), and national – and explores the reasons and processes leading to these delineations, and how they have been used. A detailed case study is then presented for Norway. Overall, two types of approaches to mapping mountains have been taken: first, considering mountains per se, based on elevation and/or topography; second, considering them among other categories, e.g., landforms or biogeographical, environmental or landscape zones. All attempts to map mountain areas derive essentially from the objectives of those commissioning and/or undertaking the work; a unitary definition remains unlikely.