Ice sheet extent and early deglacial history of the southwestern sector of the Greenland Ice Sheet

The offshore and coastal geomorphology of southwest Greenland records evidence for the advance and decay of the Greenland Ice Sheet during the Last Glacial Maximum. Regional ice flow patterns in the vicinity of Sisimiut show an enlarged ice sheet that extended southwestwards on to the shelf, with an ice stream centred over Holsteinsborg dyb. High level periglacial terrain composed of blockfield and tors is dated to between 101 and 142 ka using ²⁶Al and ¹⁰Be cosmogenic exposure ages. These limit the maximum surface elevation of the Last Glacial Maximum ice sheet in this part of southwest Greenland to ca 750–810 m asl, and demonstrate that terrain above this level has been ice free since MIS 6. Last Glacial Maximum ice thickness on the coast of ca 700 m implies that the ice sheet reached the mid to outer continental shelf edge to form the Outer Hellefisk moraines. Exposure dates record ice surface thinning from 21.0 to 9.8 ka, with downwasting rates varying from 0.06 to 0.12 m yr⁻¹. This reflects strong surface ablation associated with increased air temperatures running up to the Bølling Interstadial (GIS1e) at ca 14 ka, and later marine calving under high sea levels. The relatively late retreat of the Itilleq ice stream inland of the present coastline is similar to the pattern observed at Jakobshavn Isbræ, located 250 km north in Disko Bugt, which also retreated from the continental shelf after ca 10 ka. We hypothesise that the ice streams of West Greenland persisted on the inner shelf until the early Holocene because of their considerable ice thickness and greater ice discharge compared with the adjacent ice sheet.     

Can industrial pollution cause intersexuality in the amphipod, Echinogammarus marinus?

Following recent studies, in which intersex and/or reproductive abnormalities have been observed in a number of crustaceans in association with pollution, the prevalence of intersexuality in the amphipod, Echinogammarus marinus was monitored at sites receiving industrial discharges for one year in 2002/2003. Based upon reports of intersexuality occurring in amphipods due to feminising microsporidian parasites, the occurrence, and role of microsporidian parasites in causing intersex was investigated through histological examination. Results demonstrate a significantly higher prevalence of intersex organisms was found at sites receiving industrial discharges throughout the year when compared to a reference site, with the phenotype of intersex (intersex male and intersex female) varying in its dominance between impacted sites. Intersex specimens were significantly more likely to be infected with microsporidian parasites at sites receiving discharges than reference sites, however relatively few specimens (normal or intersex) were infected at reference sites suggesting parasitism is not the only cause of intersex. The direct/indirect role of pollution in the observed intersexuality is discussed.     

Potential evaporation in the peace river region of British Columbia

Abstract

Micrometeorological data collected over pasture in the Peace River area of British Columbia during the wet summer of 1977 were used to test the Priestley and Taylor (1972) model for potential evaporation. The model performed very well. RMSE was less than 10% of the mean evaporation rate on a daytime basis using an alpha value of 1.26. Since the model is mainly dependent on net radiation, which is rarely measured in such remote areas, this quantity was also estimated from more readily available meteorological data and used to calculate evaporation. Results were encouraging; calculated values were generally within 20 and 10% of energy balance estimates on daily and 5‐day mean bases.     

Development and testing of a two-dimensional downslope wind model

A two-dimensional numerical model has been formulated, using a terrain-following coordinate system. By introducing an iterative procedure into the direct integration method, almost identical results to the more complicated implicit method were achieved. This allows much higher computing efficiency without compromising accuracy. By using the model, the effects of ground cooling rate, slope angle and limited slope length were determined. In order to test the robustness of the model, a field campaign to collect downslope wind data was conducted. Results from the two-dimensional model simulations agree well with the observed data. It is possible to derive some simple rules for the downslope wind, with ground cooling, slope angle and slope length as the principal inputs. These simple rules will undoubtedly be useful in practical situations when accurate numerical simulations are difficult to make.     

面向地震层析成像数据库的设计方法

本文概述了面向象数据库的特点，及与传统数据库的区别。结合面向地震层析成像数据库的设计，具体描述了定义地震事件对象、、地震震相和地震台站对象，确定属性，操作和类的方法。最后，讨论了用Ｆｏｘｐｒｏ２．５ｆｏｒ Ｗｉｎｄｏｗｓ实现面向地震层析成像数据库的一些特征。     

Digital Geologic Mapping of the Ferron Sandstone, Muddy Creek, Utah, with GPS and Reflectorless Laser Rangefinders

The traditional approach to geologic mapping consists of sketching, taking orientation and thickness measurements with compass and tape, and noting positions of features on topographic maps or photos. These methods are time consuming, often difficult to realize in rough terrain, and poorly constrain lateral variations in sedimentary facies in relatively flat lying strata. We describe a case study that captures the three-dimensional architecture of sandstone bodies and key geological surfaces such as stratigraphic boundaries and faults using digital capture techniques. The Ferron sandstone in Utah is a superbly exposed ancient delta deposit that provides an improtant outcrop analog to fluvio-deltaic subsurface reservoirs. It has been the focus of many traditional outcrop studies, but here we use a methodology (“cybermapping”) based on GPS with offsets from a continuous ranging mode reflectorless laser rangefinder (“laser sketch”) for collection and analysis of basic stratigraphic and structural data in a relatively remote area. We also show hos this data can be analyzed and visualized in three dimensions. The study area was mapped in two days, which included hiking several kilometers into the area. One-the-fly and rapid static post processing of GPS surveying was used for positioning the reflectorness laser rangefinders; 60,000 points were acquired mapping sedimentological and structural features, terrain, and control points. The resultant quantitative 3D model of the geology and terrain allowed robust geometric visualization and analyses. ? 2001 John Wiley & Sons, Inc.     

Basalt basement from the Kerguelen Plateau and the trail of a Dupal plume

The first samples of volcanic basement recovered from the Kerguelen Plateau are Lower Cretaceous transitional tholeiites. Isotope and incompatible element abundance ratios for these rocks are similar to ocean island basalts from the southern hemisphere Dupal anomaly region, and geochemical, geological and geophysical data are consistent with volcanic activity associated with a mantle plume. A reconstruction of plate motions suggests that the Kerguelen Plateau formed above a mantle plume in the interval 118-95 Ma, during the opening of the Indian Ocean between India and Australia-Antarctica. This plume was the source of other plateaus and ridges of the eastern Indian Ocean and possibly the Bunbury Basalt of southwestern Australia, and is now beneath Heard Island.     

Eclogites of the D'Entrecasteaux Islands

Eclogitic rocks of the D'Entrecasteaux Islands, Papua New Guinea, are of three types: true eclogites of omphacite-garnet-rutile; retrogressed or S-stage eclogites in which some omphacite has altered to symplectites of albite and less-jadeitic clinopyroxene (or amphibole); and rocks that are eclogites in all respects except that clinopyroxene is jadeitic diopside (Jd_<20) rather than omphacite. The rocks of the third group equilibrated in eclogite facies P-T conditions and, we conclude, are Na-poor eclogites, rather than granulites; i.e., low Na in the bulk rock is the reason for low jadeite content of clinopyroxene. Bulk rock chemical data confirm low Na and Si. Other prograde phases in the ecologitic rocks are kyanite, quartz, epidote group minerals and phengite and, in the low-Na group, orthopyroxene. Post-eclogite phases are amphibole, epidote group minerals, phengite and albite and, in the Na-poor eclogites, late phlogopite, calcic plagioclase, rare scapolite, and sulfides. The eclogitic rocks occur as lenticular boudins and small concordant tabular bodies within a 2–3 km thick sequence of migmatitic gneisses and, less commonly, in granodiorite. The gneiss sequence is bounded by detachment faults above and by younger granodiorite below, and is folded into broad antiforms. The three types of eclogite equilibrated at temperatures ranging from 530 to 840°C and pressures of 12 to 24 kbar. The metamorphic complex developed during Early Cenozoic subduction and arc-continent collison, and was elevated and exposed during Mid and Late Cenozoic crustal extension. The thermal gradient during subduction averaged 10°C/km and remained low during initial uplift, increasing to 18°C/km subsequently. Uplift averaged about 1 mMa^-1 from 60 to 5 Ma, then about 4 mMa^-1.     

Chemistry and pollution of natural waters in western Kenya

Selected water analyses from the literature and current research in western Kenya are tabulated and the relationships between critical water quality parameters described. The waters are chemically characterised with Na as the dominant cation and bicarbonate as the dominant anion and, while waters of obviously different sources are represented, the available chemical data point to a general classification of bicarbonate-Na-rich waters, even for the saline waters of Lake Magadi. Potassium and chloride are among the less abundandt constituents. The concentration level of nutrients (nitrate, phosphate and sulphate) is mostly lower than maxium permissible drinking water levels, and salinity is not yet a serious problem in water bodies that are exploited for domestic and industrial purposes. Fluoride levels are variable with the higher values occurring in waters in and around the Rift Valley. Limited analytical data for I in waters from the Eldoret, Kiambu and Nairobi areas indicate concentrations well above world average figures. Mean values of some key water quality indicators such as total dissolved solids, total suspended solids and heavy metals are well below the threshold for contaminated water. These values are however exceeded by several factors in saline waters of lakes and in some springs. Significant organic pollution is reflected by mean values of parameters such as biochemical oxygen demand and faecal coliforms. The present quality of most of the water bodies in this part of the country is considered to be adequate at present for domestic and other purposes, though a gradual decrease in quality is evident from the recent upsurge in industrial activities in the subregion.     

Geomedicine in Kenya

Geomedical research in Kenya, as in other developing countries, is still in its infancy, although a significant amount of data already exists in certain aspects of the subject. The biggest advances to date have been with the halogens (F and I) but data interpretation and the identification of meaningful correlations between geochemistry and epidemiology are hampered by the use of non-multidisciplinary approaches.Additional information is needed on the behaviour of certain nutritional and toxic elements in various environmental media (soils, plants, natural waters, etc.), but present analytical facilities are woefully inadequate for the determination of these elements at the very low levels generally required. Nor is there enough trained personnel for these types of analysis.This paper attempts to summarise and synthesise the geomedical information so far available in Kenya and emphasises the potential effectiveness of more holistic, multi-disciplinary, multi-element studies in advancing this emergent field.