River flow forecasting through conceptual models part II - The Brosna catchment at Ferbane

An attempt to model the runoff process on the Brosna catchment is described. Different models are compared and it is found possible to account for about 80 per cent of the initial variance of the discharge by very simple models.     

“A sky of brass and burning winds”: documentary evidence of rainfall variability in the Kingdom of Lesotho, Southern Africa, 1824–1900

Forecasting austral summer rainfall in southern Africa is hampered by a lack of long-term instrumental data. This paper extends the historical record for the subcontinent by presenting the first extensive 19th century climate history for Lesotho derived from documentary evidence. The data sources included unpublished English-, French- and Sesotho-language materials archived in Lesotho, South Africa and the UK. These included letters, journals and reports written by missionaries and colonial authorities, which were supplemented by newspapers, diaries, travelogues and other historical sources. Each source was read in chronological order, with any climate information recorded verbatim. Observations were classified into five categories (Very Wet, Relatively Wet, ‘Normal’, Relatively Dry, and Very Dry) based upon the predominant documented climate during each ‘rain-year’ (July to June). The latter portion of the chronology was then compared for accuracy against available instrumental precipitation records from Maseru (1886–1900). The results yield a semi-continuous record of climate information from 1824 to 1900. Data are restricted to lowland areas, but reveal drought episodes in 1833–34, 1841–42, 1845–47, 1848–51, 1858–63, 1865–69, 1876–80, 1882–85 and 1895–99 (the most severe drought years being 1850–51 and 1862–63) and wet periods or floods in 1835–36, 1838–41, 1847–48, 1854–56, 1863–65, 1873–75, 1880–81, 1885–86 and 1890–94. The rainfall chronology is compared with similar records for South Africa, Botswana and Zimbabwe. Linkages to possible forcing mechanisms, including ENSO teleconnections and historical coral-derived southwest Indian Ocean sea surface temperature variations are also explored.     

Visible and near-infra-red transmission and reflectance measurements of the Luna 20 soil

Visible and near-infra-red spectra of chemically analyzed grains of glass and minerals from the Luna 20 sample were compared with diffuse reflectance spectra of the bulk soil. As in the spectra of soil samples from other localities on the Moon, pyroxene contributes two broad absorption features near 1 μm and 2 μm. The soil has a high integral reflectance (or albedo) arising from plagioclase, which appears to be the dominant mineral in the lunar highlands. The Luna 20 soil curve is most similar to the reflectance curves of the non-rayed soils at Apollo 16, in agreement with the generally similar mineralogy of these samples. The average pyroxene composition in the Luna 20 soil, as determined from the absorption bands in the diffuse reflectance spectra, and analyses of single crystals, is more calcic than in the lithic fragments. Thus, the soil appears to have a few per cent of admixed material derived from mare basalts. Comparison of the soil spectrum with telescopic curves of nearby areas reveals a close similarity; however, the Luna 20 sample is slightly less mature than expected. Luna 20 may have sampled subsurface material that is fresher than the regional surface soil, or alternatively, the Luna 20 area may contain an admixture of relatively recently exposed material from a ray crater.     

Duricrust development and valley evolution: Process–landform links in the kalahari

Duricrusts are an important landscape component of the Kalahari region of central southern Africa. Their exposures within the dry valleys (mekgacha) of the Kalahari provide some of the most widespread surface outcrops of the terrestrial Jurassic to Holocene Kalahari Group sediments. Exposures have been extensively used in the construction of lithostrati-graphic sequences, on the assumption that valley systems have incised their courses through a pre-existing duricrust sequence. Recent work, however, has identified the role of groundwater erosion processes in valley development, which may have influenced duricrust formation. Studies of duricrusts from boreholes drilled within two mekgacha show that duricrust type is intrinsically related to the presence of a valley. Analyses of calcretes and silcretes in a series of profiles and thin sections from the Letlhakeng area of Botswana also indicate extensive alteration and diagenesis in association with former higher water tables. Sedimentary sequences within duricrust host materials can be identified but there is no evidence for correlation of duricrust cements between exposures. Profile studies from the Auob Valley in Namibia, however, suggest that this valley has incised through a sequence of duricrusts. Caution is advised in future attempts to correlate duricrust types on the basis of valley exposures, with the recommendation that where such exposures are used in a lithostratigraphic context, only duricrust host material characteristics and not cementing materials should be considered.     

Primary anhydrite in Precambrian gneisses from the swakopmund district,South West Africa

Anhydrite occurs as a primary rock-forming mineral in late-Precambrian gneisses from the Rössing area, South West Africa. Studies on critical mineral associations in the area indicate that temperatures during metamorphism approached or exceeded 700° C. Textural relations in the anhydrite-bearing gneisses show that the mineral remained in equilibrium with its associated phases during metamorphism.     

Undressing the researcher: feminism, embodiment and sexuality at a queer bathhouse event

In this paper we examine how the researcher's body can be used as a tool for data collection in the process of ethnographic fieldwork. We focus in particular on the tensions inherent in undertaking embodied ethnographic research in the sexualized setting of a queer women's bathhouse event in Toronto, Canada. Our discussion addresses three moments within the research process: preparing our bodies to attend the bathhouse; positioning our bodies within the spaces of the bathhouse; and interacting with our bodies during the event. Through this discussion we argue that the body of the researcher is a contested site of knowledge production.     

Modeling degradation of terrace scarps in Grand Teton National Park, USA

The widely used linear diffusion model for hillslope evolution does not accurately predict the degradation of terrace scarps produced by the Late Pinedale West Spalding Bay Channelway (WSBC) near Jenny Lake in Grand Teton National Park, Wyoming USA. These scarps, cut into identical cohesionless quartzite gravel, were formed nearly simultaneously, during the brief period of time the WSBC was active. They are assumed to have had the same initial morphology as scarps currently forming along Snake River that are cut in the same material: a straight midsection sloping at 30° and a horizontal base and crest. The model best able to fit the observed morphology and the change in morphology with scarp height specifies the downslope debris flux is proportional to slope gradient raised to a power of 3.4.     

Delineation of lithostructural domains in northern Orissa (India) from Landsat Thematic Mapper imagery

Image-based reconnaissance geological mapping at 1:100,000 scale using Landsat TM data has delineated a college of Precambrian lithostructural domains within a 50,000-km² region which encompasses the northern portion of the Archaean to Proterozoic granulite-grade Eastern Ghats Tectonic Province and the adjacent Archaean-Mesoproterozoic Singhbhum Craton. The domains identified in the present study display distinctive internal structures on satellite imagery. Most are bounded by clearly recognisable major shear zones and faults on imagery; displacement directions may frequently be ascertained through local reorientation of planar structures adjacent to large strike-slip shear zones and through juxtaposition of domains with different structuring.

The macroscopic/megascopic structural overview provided by the Landsat interpretation, supported by preliminary field investigation, suggests that the N-S shortening (E-W fold/thrust packages with associated NE and NW strike-slip faulting), is the dominant structural style in the northernmost part of the Eastern Ghats Tectonic Province, followed by regional dextral transpression, expressed in the form of major strike-slip faults. The largest of these structures (Kerajang Fault), which may be traced for over 250 km, has demonstrable Paleozoic-Mesozoic dextral motion associated with coal basin formation. A precursor Kerajang shear zone with dextral movement in excess of 100 km of indeterminate age may also have been instrumental in juxtaposing the Singhbhum Nucleus into its present position to the north of the Eastern Ghats Tectonic Province.     

Albedo distribution on Io's surface

A visual albedo distribution model for all hemispheres of Io's surface has been synthesized from available Earth-based and spacecraft image and photometric data. The resulting model indicates some interesting patterns and symmetries on Io's surface: The dark polar caps are shifted off Io's rotational axis and are eliptical rather than circular in shape, with extensions toward the sub-Jupiter and anti-Jupiter points on Io; equatorial bright areas are located approximately on a great circle about Io, the plane of which is tilted approximately 15° toward Io longitude 60°. These and other indicated features may be clues to understanding the endogenic and exogenic processes that have resulted in Io's present observed surface characteristics.     

Dual mechanisms for the formation of fluvial silcretes in the distal reaches of the Okavango Delta fan,Botswana

Silcretes exposed within river-marginal or valley settings have been described in a number of studies, but few models have been suggested for the development of these ‘fluvial’ silcretes. An exception is that proposed by McCarthy and Ellery (Journal of Sedimentary Research, 1995, Vol. A65, pp. 77–90) to describe mechanisms of early stage near-surface silica diagenesis in the Okavango Delta, Botswana. This paper describes the characteristics and possible origins of massive surface and sub-surface silcretes at Samedupe and Boro Junction, beyond the distal margin of the Okavango Delta and further downstream than the sites described by McCarthy and Ellery. Morphological and petrological evidence from surface exposures and three sedimentary cores suggests that other modes of formation may also be applicable. A dual model of formation is proposed: surface silcretes are suggested to have developed by silica accumulation in seasonal pools remaining after the annual Okavango flood, whilst sub-surface horizons appear to have formed under conditions of varying pH associated with fluctuating groundwater levels beneath the channel floor. This model is reviewed in the context of the fluvial silcrete debate. © 1998 John Wiley & Sons, Ltd.