J. O. Barongo

Holocene palaeohydrology, groundwater and climate change in the lake basins of the Central Kenya Rift

Abstract The Central Kenya Rift contains small soda lakes such as Nakuru, Elmenteita and Bogoria, freshwater Lake Naivasha, and the partly (spatially) freshwater Lake Baringo. The hydrology of this area is controlled mainly by climate, tectonically controlled morphological and volcanic barriers, faults, and local water-table variations. Much of the area relies on groundwater for human and industrial use, though there are widespread quality issues particularly in relation to fluoride. Despite the huge demand for the resource, little is known about the highly complex groundwater systems; lacking monitoring data, an assessment is developed on the basis of regional geological, hydrogeological and hydrochemical analyses. Significant hydrological changes have taken place in the region over the last 10 000 years as a result of global, regional and local changes, but the impacts on groundwater resources are still largely unknown. The IPCC projects a 10–15% increase of rainfall in the area, but it may not necessarily result in a proportional increase in groundwater recharge. High groundwater recharge periods appear to be anchored on a decadal cycle.

Investigations of electrical properties of weathered layers in the Yala area, western Kenya, using resistivity soundings

Investigation in many parts of the world have indicated that resistivity of saprolite (a chloritization zone at the base of the weathering profile) depends uniquely on the underlying rock type. A study of electrical properties of the weathered layer was undertaken near Yala in the Nyanzian‐Kavirondian greenstone belt in western Kenya. Resistivity soundings were systematically carried out in a 24 × 40 km area. Saprolite formed over basalt had the lowest resistivity (14 Ω•m), followed by andesite (27 Ω•m) and rhyolite (67 Ω•m). Statistically meaningful data sets conclusively show, for the first time, that saprolite resistivity increases with the silica content of parent volcanic rocks. Plutonic and sedimentary rocks had higher average resistivities (granite 135 Ω•m, mudstone 79 Ω•m, grit 213 Ω•m). Thickness of the weathered layer varied between 10 and 40 m, with the largest values observed over grit (sandstone). Compared with other tropical regions, the saprolite layer in western Kenya appears relatively th...

Method for depth estimation on aeromagnetic vertical gradient anomalies

The straight‐slope technique introduced some years ago by Vacquier et al. (1951) is employed to develop simple empirical procedures that can be used to determine depth to the top/center of anomalous sources on measured aeromagnetic vertical gradient profiles. Five geologic bodies/structures in the form of their magnetic/geometric model equivalents, namely, point pole, point dipole, finite dipole, dipping dike, and dipping contact are considered. From analysis of the normalized theoretical curves due to those models it is observed that the horizontal projection of the straight part of the steepest sections of each curve is insensitive to changes in the inclination of the Earth’s magnetic field and also to the dip angle of dipping models. Further analysis of the curves using this observation leads to the conclusion that, when dealing with the interpretation of observed vertical gradient profiles, the length of the horizontal projection on a given profile must be doubled to obtain depth to the point‐pole, po...

Euler’s differential equation and the identification of the magnetic point‐pole and point‐dipole sources

The concept of point‐pole and point‐dipole in interpretation of magnetic data is often employed in the analysis of magnetic anomalies (or their derivatives) caused by geologic bodies whose geometric shapes approach those of (1) narrow prisms of infinite depth extent aligned, more or less, in the direction of the inducing earth’s magnetic field, and (2) spheres, respectively. The two geologic bodies are assumed to be magnetically polarized in the direction of the Earth’s total magnetic field vector (Figure 1). One problem that perhaps is not realized when interpretations are carried out on such anomalies, especially in regions of high magnetic latitudes (45–90 degrees), is that of being unable to differentiate an anomaly due to a point‐pole from that due to a point‐dipole source. The two anomalies look more or less alike at those latitudes (Figure 2). Hood (1971) presented a graphical procedure of determining depth to the top/center of the point pole/dipole in which he assumed prior knowledge of the anomal...

Geophysical investigations for kimberlite pipes in the greenstone belt of western Kenya

Abstract Some of the EM conductors, delineated in the greenstone belt of western Kenya during an airborne Barringer INPUT survey in 1977 and believed to be kimberlite pipe targets, have been geophysically investigated on the ground. Four of those initially investigated are reported in this paper. The results show that three of these are elliptically shaped and oriented in the general strike direction of the local geology. They are associated with a distinct magnetic signature. The magnetic source in each case seems to be deeply seated. The fourth conductor has a more or less circular surface outline. It is associated with a ground vertical magnetic pattern that appears to be of surficial origin and aligned in a north-south direction across the middle of the conductor. No geological outcrops occur on the conductors, except a few at their edges. Diamond drilling was carried out on the four conductors. Although not fully confirmed, drill core results from three of them show what appears to be vaguely defined kimberlitic material.

Earth Science Education in Kenya

Abstract The University of Nairobi is currently the only University in Kenya which offers degree level courses in the earth sciences. The Department was founded in 1961, became part of an autonomous University in 1970, awarded its first degrees in 1972 and awarded its first Geology degrees in 1978. The Department currently offers a four-year B.Sc. course - delivered as part of a course unit system - and an M.Sc. programme in Geology. Students are admitted to the University after eight years of primary and four years of secondary schooling. Graduates find employment either in government departments or in the private sector. The Department currently has 15 academic staff who are involved in a variety of research projects. Currently, there are collaborative links with Universities in Germany, Sweden and South Africa.