The Tertiary (22 Ma) carbonatite centre at Buru hill is located towards the eastern end of the Nyanza rift, western Kenya. As revealed by geochemistry and petrology of drill core samples, the Buru centre ranges in composition from surficial lateritized pyroclastic ferrocarbonatite to recrystallized ferruginous calciocarbonatite at depth.

Mineralogically the lateritic cover of the Buru carbonatite centre is characterized by goethite, hematite, psilomelane, baryte, fluorite with minor calcite, bastnäsite and significant amounts of monazite. A transitional middle zone consists of ferrocarbonatite grading into ferruginous calciocarbonatite containing siderite, baryte and fluorite, a greater proportion of bastnäsite replacing calcite, but lesser proportions of monazite. The lowermost zone consists of ferruginous calciocarbonatite containing intimate mixtures of siderite and calcite, with parisite and synchysite existing as major replacive components of calcite down to depths of 200 m. Synchysite appears to be the more stable form of lanthanide fluorcarbonate at depths below 150 m.

Oxygen isotope measurements on separated calcite concentrates from three of the Buru drill cores reveal significant deviations from primary igneous carbonatite values suggesting isotopic re-equilibration with meteoric water. Accepting that the African plate may have been stationery during the past 30 Ma, it is possible to use a modern sample of water from the Kenya rift to estimate the equilibration temperature at which Buru carbonatite in western Kenya has recrystallized. Temperatures of ∼60 to 90°C suggest that the hot-spring activity encouraged the formation of replacive lanthanide fluorcarbonate in ferruginous calciocarbonatite. Lanthanide enrichment also occurred closer to the surface within the pyroclastic ferrocarbonatite at temperatures of ∼40 to 60°C corresponding to waning stages of hot-spring activity. Further lanthanide enrichment redistribution and oxide formation occurred at surface supergene temperatures of ∼20 to 30°C forming the lateritized top of the carbonatite.

The wider implications from these carbonatite studies are the recognition that lanthanide enrichment can be preserved in volcanic-subvolcanic centres, and that lanthanide fluorcarbonates can replace calcite in response to circulating hot-spring waters. From a classification point of view, ferrocarbonatites should be seen as products of meteoric hydrothermal systems unrelated to carbonatite magmatic processes

Geological and palaeontological research in the Rhynie area, Aberdeenshire, Scotland, has progressed in several stages. Following early surveys in the nineteenth century, Dr William Mackie mapped the western margin of the basin in 1910–1913, and discovered the plant-bearing chert. Following trenching of the chert in 1913, Kidston & Lang described the plant fossils between 1917 and 1921 and Scourfield, Hirst and Maulik the arthropods in the 1920s. Following a ‘dark age’ of some 30 years, Geoffrey Lyon awakened interest in the late 1950s. Trenching in 1963–1971 provided Lyon and his co-workers with new material, and resulted in finds of new plants and reinterpretations of earlier work. The next phase was initiated by Winfried Remy's discovery of gametophytes in material given to him by Lyon. Since 1980, the Münster school has continued to make exciting discoveries. Aberdeen University involvement began in 1987 with geochemical work confirming a hot spring origin for the chert. Drill cores taken in 1988 and 1997, and further trenching have allowed structural, sedimentological and stratigraphic reappraisals, and resulted in the discovery of a new biota in the Windyfield chert. Long-term collaborative international research continues to advance interpretation of this unique Early Devonian hot spring system, and the remarkably diverse freshwater and terrestrial biota of the cherts.

A new crustacean, Castracollis wilsonae is described from a loose block of the Early Devonian Rhynie chert, found in the vicinity of Rhynie, Aberdeenshire, Scotland. It differs markedly from Lepidocaris rhyniensis, Scourfield 1926, the only other crustacean found in the Rhynie chert.

The material comprises complete individuals up to 8 mm long and fragmentary remains. The head is normally damaged and detached from the body, and damage to the anterior of the trunk suggests the specimens are exuviae. The head appears domed with a labrum, robust mandibles, and long biramous antennae. A few specimens exhibit a probable detached cephalo-thoracicshield. The trunk is multi-segmented, comprising similar ring-like somites. The thorax variably comprises up to 26 segments. The anterior 11 segments possess similar long, phyllopodous appendages, the remainder variably possess 10 to 15 phyllopodous appendages with a disposition of one per somite. The abdomen comprises up to 28 apodous segments. The posterior of the body comprises a telson with two furcal rami.

The crustacean is most probably a calmanostracan branchiopod. It occurs associated with Lepidocaris, charophytes, cyanobacteria and coprolites within a ‘clotted’ chert texture, indicating subaqueous deposition, most probably in a temporary freshwater pool in an area of surficial hydrothermal activity.