Freetown Peninsula Research Articles

The origin and emplacement of the Freetown Intrusion, Sierra Leone

The Freetown Intrusion in Sierra Leone is a large, layered mafic intrusion. Only a small part of the intrusion appears on land to form the Freetown Peninsula, and the larger part lies beneath the Atlantic Ocean. This is demonstrated by gravity and geomagnetic measurements, which also indicate that intrusion occurred over at least 1–2 Ma. The intrusion was formed at 196–201 Ma and is, therefore, concordant with the Central Atlantic Magmatic Province (CAMP) magmatism. At this time, the region was undergoing crustal extension prior to the later opening of the Central Atlantic Ocean. Initially, the magma intruded the Pan-African 2 suture and used this as a conduit for magma ascent, interdigitating with the highly sheared and metamorphosed rocks of the suture. The regional tensile stress allowed the conduit to open further and permitted the continued ascent of magma with subsequent crystal deposition and formation of the layers. Crystallisation commenced at depth to form a crystal mush. The layering was caused by flow, with variations in the supply of the crystal mush and varying proportions of olivine, pyroxene, and plagioclase. The silicates do not show a progressive change in composition indicative of mineral fractionation in a closed chamber. Locally, the intrusion of a plagioclase-rich crystal mush led to the presence of thick anorthosite layers. The initial layering followed the dip of the suture, and the layering steepened as the conduit opened. Sr–Nd isotopic and geochemical analyses both indicate that there was a significant contribution to the intrusion from Pan-African and older host rocks. These were assimilated into the magma. Variations in this contribution led to the formation of both gabbroic and noritic layers. Fragments of the host rocks were entrained during magma ascent and are now present as xenoliths.

Coupling multivariate analysis and Bayesian isotope mixing model to assess the origin and quality of groundwater in the Freetown Layered Complex, Sierra Leone

The current study combined the water quality index, multivariate statistical techniques, environmental isotopes, and the Bayesian isotope mixing model to determine the extent of groundwater pollution, origin, age, and proportional source contribution to groundwater recharge in the Freetown peninsula. The water quality index analysis depicts that all the groundwaters are excellent and suitable for drinking purposes. The Gibb’s diagram suggests that water-rock interaction and precipitation are the dominant sources impacting the groundwater chemistry while sodium chloride and magnesium bicarbonate are the dominant water types in the Freetown peninsula. This study finds that saltwater and anthropogenic contamination from agriculture and domestic sewage significantly impact the groundwater quality in the study area. Two (2) clusters were delineated; cluster 1 showed the characteristics of groundwater while cluster 2 demonstrated the characteristics of estuary water. A plot of 2H versus 18O showed that the groundwaters in the study area are of meteoric origin. The Bayesian model (SIMMR) output revealed that precipitation (83%) was the dominant source of groundwater recharge in the study area. The tritium analysis revealed that the majority of the groundwaters (83.3%) are young and of recent recharge. This study serves as a baseline to evaluate the percentage sources of salinity in groundwater.

Molecular phylogenetic analysis of spiny eels (Mastacembelidae: Mastacembelus) from the Rokel River basin and adjacent areas of Sierra Leone, West Africa.

Cytochrome b (Cytb) sequences from 23 specimens of Mastacembelus spp. from the Rokel River, Taia/Jong River basins, and Freetown Peninsula were used in this study. These sequences were used to perform a gene-based phylogenetic analysis along with closely allied congeneric species in the Upper Guinea Forest in Africa. The resulting phylogenies inferred from Cytb showed populations of M. liberiensis from the Rokel River basin clustered into an exclusive lineage being sister to the lineage formed by M. greshoffi from the Congo basin. The Freetown Peninsula population of M. liberiensis clustered with sequences previously identified as M. taiaensis from the Taia/Jong River basin, sister to sequences of M. taiaensis from the Rokel River basin. The paired lineages were sister to the lineage formed by sequences from samples of the Taia/Jong River basin. These findings lead to the following conclusions: (1) hidden species diversity of spiny eels exists in either the Rokel River or the Jong River basin; (2) a likely available name for this species from the Freetown Peninsula is M. laticauda distinct from M. liberiensis; (3) given the diversity within M. liberiensis observed in the rivers sampled in Sierra Leone, it seems likely that the remaining rivers of Liberia and Sierra Leone reported having M. liberiensis may also harbor undescribed diversity. It is difficult to elevate some available junior synonyms based solely on a phylogeny inferred from Cytochrome b. We suggest that more samples from the entire range of M. liberiensis are needed and an integrated approach is required.

The 2017 Regent Landslide, Freetown Peninsula, Sierra Leone

At 06:50 on Monday 14 August 2017, a hillslope on the Freetown Peninsula, Sierra Leone, collapsed, sending 300 000 m 3 of debris into the flooded valley below. As this debris mixed with floodwater it became a sediment-laden flood which entered a drainage channel and travelled 6 km to the coastline. The event destroyed nearly 400 buildings, claimed the lives of an estimated 1100 people and affected c. 5000 people. The mechanism was a two-stage rainfall-triggered landslide followed by a channelized debris-laden flood. The processes were similar to the nearby 1945 event in Charlotte, which killed at least 13 people. Geomorphological mapping has identified evidence of hundreds of other large landslides that occurred before modern records, providing an appreciation of the slope processes affecting the Freetown Peninsula. Following the 2017 Regent Landslide, rehabilitation of the affected area involved a risk-reduction strategy that centred on reducing population exposure. These events are a reminder that the steep slopes and valleys across the Freetown Peninsula are highly susceptible to rainfall-triggered landslides which, given the topography, have a high propensity to generate high intensity landslides and debris-laden floods. Future urbanization must consider whole-catchment management, flooding and slope engineering issues to provide lasting landslide risk reduction.

Inclusions in an isoferroplatinum nugget from the Freetown Layered Complex, Sierra Leone

ABSTRACTInclusions of platinum-group minerals (PGM) within alluvial isoferroplatinum nuggets from the Freetown Peninsula, Sierra Leone, are aligned with their shape determined by the structure of their host. The edges of the majority of the inclusions lie at 0°, 45° or 90° to external crystal edges of the nugget which shows that the inclusions are not randomly oriented earlier minerals incorporated within their host. The inclusions are later infills, probably formed at the surface of the nugget during growth and subsequently enclosed by the growing nugget. PGM on the present surface of the nugget represent the last stage of this partnership. A single nugget containing abundant inclusions is described here but similar features are observed in other nuggets from the same area. The inclusions contain laurite (RuS2), irarsite–hollingworthite (IrAsS–RhAsS), Pd–Te–Bi–Sb phases, Ir-alloy, Os-alloy, Pd-bearing Au, an Rh–Te phase, Pd–Au alloy and Pd–Pt–Cu alloy. PGM found on the nugget surface include laurite, irarsite and cuprorhodsite (CuRh2S4). The Pd–Te–Bi–Sb phases may include Sb-rich keithconnite (Pd20S7) and compositions close to the kotulskite–sobolevskite solid-solution series (PdTe–BiTe). Textural evidence suggests that formation of the nuggets began with the isoferroplatinum host and the voids were filled starting intergrowths of laurite and irarsite–hollingworthite with both laurite and irarsite–hollingworthite often showing compositional zonation and each of them replacing the other. Filling of the voids probably continued with Pd-Cu-bearing gold, Sb-rich keithconnite (Pd,Pt)20.06(Te,Sb,Bi)6.94, keithconnite, telluropalladinite Pd9(Te,Bi)4, RhTe and finally Ir-alloy and then Os-alloy. The nuggets are thought to be neoform growths in the organic- and bacterial-rich soils of the tropical rain forest cover of the Freetown intrusion. The mineralogical assemblage in the layered gabbros of the intrusion has been previously shown to differ from the alluvial assemblage in the rivers and these inclusions, not seen in Pt3Fe in the unaltered rocks, add a further item to the catalogue of differences.

Political Economy of Forest Ecology in Sierra Leone: A Focus on the Western Area Peninsular Forest (WAPFoR)

This article addressed historical aspects of the political economy involving sustained forest ecology in Sierra Leone as a whole, with emphasis on the Freetown Peninsula and its surrounding communities. Attention is paid to cultural, social and economic aspects involving forest livelihoods of residents on the Freetown Peninsula and far afield. The term 'Political Economy' is used in this situation to denote the relationship between the economics of people's livelihoods and public policy (in relation to the management of legislative procedures) in ensuring that resources in the forest environment is sustainably managed to cater for the livelihood needs of people in Sierra Leone, while at the same time maintaining a balance in protecting the forest ecosystems. The paper has provided a critical review of the political economy of forest ecology in the country on the basis of scholarly discourses, and its applicability in adapting to the fragile political administrative management Sierra Leone have (and is continuing to) experienced.

The mineralogy, geochemistry and genesis of the alluvial platinum-group minerals of the Freetown Layered Complex, Sierra Leone

ABSTRACTHeavy mineral concentrates from rivers and river terraces near York, Freetown Peninsula, Sierra Leone have been examined for their platinum-group mineral (PGM) content. The alluvial PGM are 0.1 to 1.5 mm in size and include Cu-bearing isoferroplatinum (Pt3Fe) and disordered Pt3–xFe (x≤ 0.38), tulameenite (Pt2FeCu), hongshiite (PtCu), cooperite–vysotskite (PtS–PdS), laurite (RuS2), erlichmanite (OsS2), Os-Ir alloy, Os-Ru alloy and native copper.Are the alluvial nuggets primary or a neoformation? Comparison of the PGM mineralogy of fresh rocks, weathered rocks and the saprolite, with the alluvial suite shows strongly contrasting features highlighted by the mineral assemblage. Cooperite in the fresh rocks is rare in the alluvium whilst Pt-Fe alloys become more abundant. Oxidized PGM are a feature only of the weathering process and disordering of the Pt-Fe alloys develops during weathering. Palladium is much less abundant in the alluvial suite than in the primary minerals whereas Cu, present as Cu-sulfides in the fresh rocks, occurs in the alluvium as a minor component of the Pt-Fe alloys and as hongshiite alteration to the Pt-Fe alloys. The size difference is striking; the primary mineralogy is micrometre-sized whereas the alluvial PGM are three orders of magnitude larger. Delicate PGM with alteration textures are seen only in the weathered rocks whilst delicate dendritic PGM are reported only from the alluvial suite. An organic coating to the alluvial PGM may be indicative of an organic or bacterial involvement. Some alluvial PGM occur in a drainage basin devoid of outcrops of PGE-bearing horizons.Together these contrasting features of the primary and placer PGM support the proposal that the Freetown nuggets developed as a result of breakdown of the primary PGM during weathering, movement of the PGE in solution, and growth of new PGM in placers with a different mineral assemblage, mineralogy and mineral chemistry.

Using a Logistic Regression Model to Analyze Alley Farming Adoption Factors in Sierra Leone

Slash-and-burn shifting cultivation is the conventional farming practice in Sierra Leone, where communal land tenure is by far the most common form of land use. Alley farming, the alternative agricultural system, has been introduced as a technical option to increase yield, reduce or eliminate fallow and conserve soil water. This study uses a logistic regression model to determine the factors influencing the adoption of alley farming in Sierra Leone. Data for the study were collected from a total of 160 farmers in 16 farming communities across 4 ecotones in the Freetown Peninsula through a survey, interactive discussion and personal observation. It is found that although most of these communities are aware of alley farming, female farmers are less likely than males to adopt this farming technology. Also membership of farmers’ associations and access to extension services positively influences adoption of alley farming, but limited land availability hinders adoption in the region. Most of the farmers practicing or trying out alley farming prefer this farming system over slash-and-burn shifting cultivation. High demand for fuelwood, short or no fallow periods and replenishment of soil fertility are among the attributes driving farmers to switch to alley farming. Despite its merits, alley farming is not perceived as a complete substitute for slash-and-burn shifting cultivation in the study area. For wider adoption, there is the need to develop demonstration farms to show the feasibility of incorporating farmer-specific biophysical, hydro-climatic and socio-economic conditions into alley farming system in the region.

Multiple genetic lineages challenge the monospecific status of the West African endemic frog family Odontobatrachidae.

BackgroundCorrect species identification is crucial in different fields of biology, and in conservation. The endemic West African frog family Odontobatrachidae currently contains a single described species, Odontobatrachus natator. From western Guinea to western Côte d'Ivoire it inhabits forests around waterfalls or cascades. Based on more than 130 specimens from 78 localities, covering the entire distribution, we investigated the molecular diversity of these frogs.ResultsOur analyses included mitochondrial and nuclear genes, with a concatenated alignment of 3527 base pairs. We detected high level of genetic differentiation with five distinct lineages or operational taxonomic units (OTUs). These OTUs were also identified by two different species delimitation approaches, Generalized Mixed Yule Coalescent (GMYC) and cluster algorithm. All OTUs occur in parapatry in the Upper Guinean forests. One OTU, assigned to the “true” Odontobatrachus natator, covers the largest distribution, ranging from the border region of western Sierra Leone-Guinea to eastern Liberia. Two OTUs are restricted to western Guinea (Fouta Djallon and foothills), while two others occur in eastern Guinea and the border region of Guinea-Liberia-Côte d'Ivoire. The OTU representing O. natator consists of two divergent subclades: one restricted to the Freetown Peninsula (Sierra Leone) and the other covering all populations further inland. Environmental niche models indicated that the restricted Freetown Peninsula population is separated by unsuitable habitat from remaining populations.ConclusionGeographic isolation of OTUs and molecular differences comparable to species level differentiation in other frog families indicate that O. natator contains cryptic species diversity. Respective distribution patterns most probably resulted from repeated changes of forest cover (contraction and expansion) over evolutionary timescales. The survival within forest refugia that have persisted through multiple drier periods and subsequent dispersal during wetter times may best explain the observed geographic distributions of OTUs. According to the IUCN Red List range criteria each OTU should be classified as “Endangered.” If the Freetown Peninsula “natator” population is recognized as a distinct species it would warrant recognition as “Critically Endangered.” The identification of cryptic lineages highlights the urgent need to protect these frogs, all of which are endemic to small areas within the Upper Guinean biodiversity hotspot.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-015-0346-9) contains supplementary material, which is available to authorized users.

Deforestation: constructing problems and solutions on Sierra Leone's Freetown Peninsula

This article examines the issue of deforestation on Sierra Leone's Freetown Peninsula, specifically analysing the gap that exists between the rhetoric surrounding the problem of deforestation and the subsequent policies and projects that are implemented to address it. It is argued in this paper that this gap can be better understood by examining how different actors involved in policy and projects interact over the issue of deforestation. Such an examination reveals how these actors produce discourses of blame towards poorer, politically weaker groups, which ultimately results in deforestation 'solutions' that intervene into their lives. These prescriptions of blame and subsequent solutions for deforestation are negotiated through a combination of local realities, which includes the occurrence of deforestation, and global influences such as development discourses and interventions. The analysis here reflects a political ecology framework that also draws from post-structuralist insights and reveals how underlying discourses, actions and actors across a broad political, social and economic spectrum ultimately play a role in influencing the causes, perceptions and solutions relating to deforestation.Keywords: Deforestation, Political Ecology, Freetown, Discourses, Development, Sierra Leone, Africa

Osmium Isotope Heterogeneity in Os-Ir-Ru Inclusions within Platinum-Iron Alloy Placer Grains from the Freetown Layered Complex; Sierra Leone

The measurement of osmium isotope ratios has been used in previous studies to evaluate the origin and mode of formation of platinum-group element mineralisation. In particular, where platinum-group mineral (PGM) grains occur as placer deposits in areas of the Cordilleran mountain chains of the USA and Canada, in Kalimantan, and in Sierra Leone, osmium isotopes have provided useful insights into their possible origins. (Bowles et al., submitted., Lyon et al., 1997; Hattori and Cabri, 1992) In the present work, the genesis of PGM grains in placers associated with the Freetown igneous complex, Sierra Leone, is being investigated. The Freetown intrusion is a roughly circular body approximately 30 km in diameter. It consists of five main cycles (zones) of troctolite, olivine-gabbro, norite, gabbro and anorthosite, four of which are exposed on the Freetown Peninsula and the fifth seen only in a borehole. Approximately one third of the intrusion is exposed on land with the four outcropping zones forming four arcuate ranges of hills on the Freetown Peninsula. The PGM grains are found in soils, and in sediments in, or near, the rivers and streams draining the area. The grains are mostly 1-2 mm in diameter, with larger grains known to occur. The grains have been reported as exhibiting both euhedral and dendritic growth habits. (Bowles, 1995). The main platinum-group minerals found in this locality occur as: (1) pyritohedra of erlichmanite (OsS2) and (2) platinum-iron alloy grains (Pt3Fe) with inclusions of Os-Ir-Ru alloy, erlichmanite (OsS2), laurite (RuS2), tulameenite (CuFePt2) and cuprorhodsite (CuRh2S4). The previously reported osmium isotope ratios measured on the Os-lr-Ru phases within Pt3Fe grains from Sierra Leone are within the range 0.15 0.25, when converted to equivalent 187Os/188Os ratios (Hattori, et al., 1991). This variation was determined between inclusions from separate grains, not between inclusions within a single grain, and has been variously interpreted as resulting from magrnatic, metasomatic or supergene processes. The present study also concentrates on the Os-IrRu alloys within Pt3Fe grains, the emphasis being on collection of data from Pt3Fe grains containing more than one Os-Ir-Ru inclusion to establish whether or not there is any detectable variation of the 187Os/188Os ratios within and between individual inclusions.

Relationship between rainfall, altitude and distance from the sea in the Freetown Peninsula, Sierra Leone

Abstract Statistical analysis of mean monthly rainfall measured by 31 gauges in the Freetown Peninsula shows clear differences between those facing the south-westerly monsoon and those in the peninsular rain-shadow. Whilst catches between ocean-facing and rain-shadow gauges were very similar in the drier months of December to May, catches by ocean-facing gauges were considerably greater in the wetter months of June to October, and their catches varied less spatially. Rainfall in the monsoon months increased with altitude, but the relationships between monthly rainfall and altitude were more marked for rain-shadow gauges than for ocean-facing gauges. Rainfall in the monsoon months also tended to decrease with distance from the sea, and whilst the decreases were similar in magnitude for both rain-shadow and ocean-facing gauges, the decreases per km distance were less variable in the rain-shadow than where gauges faced the ocean. Two gauges, one in rain-shadow and one ocean-facing, were found to catch less t...

Jentink's duiker in Sierra Leone: evidence from the Freetown Peninsula

Jentink's duiker, Africa's rarest duiker, was reported to be common in Sierra Leone at the turn of the century, but subsequent investigations failed to find evidence of the animal's presence. In 1988, as part of a faunal survey organized by the Conservation Society of Sierra Leone, the authors discovered that the duiker definitely occurred there and that some had been recently killed. Although this finding extends the known range of the species, the duiker is rare and remains poorly known. There were recommendations to protect the forests of the Freetown Peninsula even before the presence of the duiker was confirmed and these are now reinforced.

An offshore geophysical survey of the Freetown igneous complex, Sierra Leone

Gravity, magnetic and bathymetric surveys have been carried out to determine the offshore extent of the basic igneous intrusion exposed on the Freetown Peninsula, Sierra Leone. Although the westward continuation of the complex is not expressed bathymetrically, positive free-air anomalies show that it is an elongated feature, some 150 km in length, with a NW-SE trend. Gravity modelling indicates that the intrusion has a maximum width of about 50 km and reaches depths exceeding 17 km southwest of Freetown, where free-air values exceeding 150 mGal have been observed. The thickness of the body decreases towards the north as the top dips under the sediments of the outer continental shelf. To the west of the complex, a WNW-ESE gravity low on the outer shelf reflects a basement depression which is filled with almost 6 km of sediments. Large magnetic anomalies, with a total range of more than 1000 nT, are recorded over the Freetown intrusion. The dominant feature of the magnetic field is an area of negative anomalies within the complex, flanked by positive anomalies west of Freetown. Two-dimensional magnetic models show that the main part of the complex is normally magnetised but large positive magnetic anomalies also indicate the presence of reversely magnetised zones within the intrusion. The linearity and trend of the complex are consistent with an igneous origin which is closely related to Atlantic rifting and early movements along the Guinée Fracture Zone.

The socio-ecology of firewood and charcoal on the Freetown peninsula

Opening ParagraphIn a country which in the last 200 years has undergone continuous and often momentous political, economic and social changes, few things are capable of conveying as strong an impression of stability and changelessness as wood fuel (charcoal and firewood) consumption and production; and nowhere is this more striking than on the Freetown or Western Area (formerly Colony) peninsula. In this region, which has always accounted for the major share of national electricity, kerosene and cooking gas (LPG) consumption, not only is current percentage household firewood consumption only fractionally lower than in the nineteenth century but a much higher proportion of households consume charcoal now than at any time in the last two centuries (Cline-Cole, 1984a). Today firewood and charcoal combined supply a minimum of 80 per cent of total peninsula energy demand for both domestic and non-household uses (Davidson, 1985). Freetown's firewood consumption also represents some 10 per cent of the national total (Atlanta, 1979).

Liberated Africans in Cape Colony in the First Half of the Nineteenth Century

From 1808 Africans aboard slave ships bound for the Americas were seized by the British navy off the West African coast and taken to Freetown, Sierra Leone, where they were adjudged prizes of His Majesty and their human cargoes released. John Peterson and others have provided vivid accounts of what happened to the Liberated Africans on the Freetown peninsula, and how a Creole society evolved there.1 But the fact that Africans were landed at the southern tip of the continent in a similar way has gone almost unnoticed. In recent years scholars have at best made brief reference to those called at the Cape,2 and neither their numbers nor what became of them has received close attention. The five thousand British settlers who arrived at the Cape in 1820 have been studied in great detail. At least as many Prize Negroes were taken into service at the Cape over the four decades after 1808, and they played a not unimportant role in the transition from slave to free labor following the end of British involvement in the trans-Atlantic slave trade.

The distribution of the Simulium damnosum complex in Sierra Leone and its relation to onchocerciasis.

Because of the paucity of literature concerning onchocerciasis and its vectors in Sierra Leone, new information of the geographical distribution of the Simulium damnosum complex is presented in the context of a comprehensive review of what is known generally about S. damnosum s.l. in Sierra Leone, and how the data relate to the transmission of onchocerciasis. Neither biting adults nor breeding sites have been found on the coastal plain and Freetown peninsula, and these area seem to be free from infestation. Throughout the rest of the country S. damnosum s.l. breeds extensively in all the major river systems. The close proximity of the major rivers to one another facilitates inter-river migration, and ensures that most villages are well within the fly's dispersal range. In accordance with this, onchocerciasis is widespread throughout Sierra Leone and vector biting has been recorded away from riverine breeding sites. Seven cytospecies have been recorded in Sierra Leone but of these S. sirbanum and S. damnosum s.str. are rare outside the far north, in the narrow savanna belt. Simulium squamosum and S. yahense are widely distributed, although S. squamosum is somewhat less common than S. yahense which unexpectedly occurs in large rivers of the forest and savanna as well as small forest streams. Simulium sanctipauli has been found in the south-east of the country, where the forest is most dense, whereas S. soubrense occurs farther north. A new species referred to as S. soubrense 'B' is restricted to the south and west of the country. Over most of Sierra Leone onchocerciasis shows a 'forest' epidemiology and is transmitted by 'forest' vector cytospecies. However, data from the narrow savanna belt in the extreme north are sparse.

The nature of the Late Paleozoic glaciation in Gondwana as determined from an analysis of garnets and other heavy minerals: Discussion

Gravenor (1979) has used chattermark trails found upon the surfaces of detrital garnet grains as palaeoenvironmental indicators of both the degree and multiplicity of glaciation in an area. Such a practice of using this microtexture analysis to authenticate ancient deposits (developed from Folk (1975); Gravenor et al. (1978)) may prove erroneous or, at the least, questionable in the light of scanning electron microscope theory (Margolis and Kennett 1971; Whalley and Krinsley 1974). In addition, some problems recently identified regarding the origin of these chattermark trails (Bull 1977; Rocha-Campos and Krauspenhar 1978) need to be considered. A major aim of Gravenor (1979, p. 1138) was . . to examine the evidence provided by an analysis of heavy minerals, particularly garnets . . . to provide an explanation for certain of the controversial aspects of this (the Gondwana) glaciation. (our parentheses). The evidence cited depended heavily upon the acceptance that chattermark trails are not only mechanically formed but that they are glacially formed. We wish to question the hypothesis of formation of grinding as the sole mechanism of chattermark genesis and in support of these views we shall draw upon recent results that we have obtained from analysis of garnet and quartz grains taken from deposits (Table 1). More detailed presentation of these data and their implications to chattermark formation is presently in preparation (Bull et al. , in preparation). The deposits were taken from beaches on Freetown Peninsula, Sierra Leone, and from Cape Comorin beach and dune complex, Tamilnadu State, southern India. In both instances, fieldwork and literature searches have shown that the deposits sampled are not likely to have been affected either by ancient or more modern modification. Those samples from the Freetown Peninsula have derived from Archaean granitic rocks either from the north-central Sierra Leone or possibly from the south along the West African coastline. Those samples taken from Cape Comorin have also derived from more ancient basement rocks (gneiss, granulite, and charnockite) of the Ghats Mountains to the west. The implications of our findings (Table 1) are that chattermark trails can seemingly be found in the same or higher percentages upon quartz and garnet grains from nonglacial sediments as those identified from sediments by Gravenor. Furthermore, these results are compatible with those of RochaCampos and Krauspenhar (1978) who considered the features to be formed in a subaqueous environment with later chemical etching. The samples taken from both India and Sierra Leone have, at one time or another, been subjected to modification in the beach environment. Whether the textures are mechanically formed in subaqueous environments later to be chemically etched or indeed solely the result of chemical action requires further consideration (Bull et al., in preparation). Nevertheless, it can be shown that chattermark trails are not exclusively formed by modification (whatever glacial modification is: see Whalley and Krinsley (1974)). Most certainly, glaciers do impart chattermark trails upon grains, however, great caution must be exercised in using these textures for environmental reconstruction. By considering that chattermark trails were at

Deforestation, the decline of the horse, and the spread of the tsetse fly and trypanosomiasis (nagana) in nineteenth century Sierra Leone

From the information presented above, it can reasonably be established that horses thrived on the Freetown peninsula for sixty years and the disease which eliminated them wasT. brucei. This disease was prevalent for at least 15 years although it eventually disappeared, probably before 1900. In addition, clearance of the forest, in three overlapping phases, was carried out prior to and during the outbreak.From the ecology of the three species of tsetse fly possibly implicated in the outbreak of the disease in Sierra Leone, it can be deduced that deforestation and the consequent regeneration and cultivation led to favourable conditions for the expansion of at leastG. palpalisandG. longipalpis, and possibly also ofG. morsitans. Taking into account the information currently available on the inter-relationships between tsetse fly and trypanosome species, it can also be suggested thatG. longipalpiswas probably the primary source of the disease but that the disease was sustained, particularly around Freetown itself, byG. palpalisand possibly by other biting flies. ThatG. longipalpisor evenG. morsitansprobably initiated the outbreak makes the eventual disappearance of the disease more understandable since both of these species relied upon regenerated forest and an abundance of game, resources which diminished as agriculture progressed. It is likely that these primary carriers infected horses and cattle moving between the provinces and Freetown, thereby providing the link in spreading the disease to the Colony.It appears therefore that the removal of the forest led to the outbreak of trypanosomiasis in horses. A different and more rational approach to forestry in Sierra Leone would have avoided this altogether. In fact it is fortunate that the consequences of this indiscriminate deforestation were not more serious since all three tsetse flies in question are carriers of the human sleeping sickness,T. gambiense. For some reason, however, this species of trypanosome, whilst common in the interior, is not prevalent in the coastal areas of West Africa, though there was in fact, an epidemic of this disease in the 1930s in the Kaiahun area, associated withG. palpalis.Since the horse is relatively sensitive to tsetse fly and its associated trypanosomes, this animal is a good indicator of the presence of trypanosomiasis. Dr McCoy in his memorandum mentions that horses thrive in the Gambia and at Lagos and that ‘loin disease’ was unknown in these places. He makes no reference, however, to horses in Ghana. The history of the horse in other parts of West Africa may therefore be worth pursuing in this respect.

The water balance of an exceptionally wet catchment area in West Africa

Precipitation, evaporation and runoff data for a small catchment in the exceptionally wet Freetown peninsula region of Sierra Leone, West Africa, are described and analysed. Both long and short term precipitation and runoff rates are shown to be far higher than those normally associated with West Africa, a flood discharge of 23.000 m 3sec −1km −2 being a particularly notable event. The study confirms that this is one of the wettest areas in Africa.