An analysis of the microseismicity distribution within Kenya from temporary recording networks shows the activity to be primarily associated with the Kenya Rift and the Nyanza Trough with increased activity in areas of recent volcanic and geothermal activity. A 100km x 80km earthquake recording network was operated for 3 months (Jan-Mar 1990) in the Lake Baringo region of the Kenya Rift Valley. Twenty-nine stations were deployed over a region including the Elgeyo escarpment, the Kerio Valley, the Tugen Hills and the Baringo basin. Eighty local events of ML< 2.0 were located within 50km of the network. These events are situated within the central part of the rift, showing some association with the main rift faults but mainly clustering beneath Lake Baringo at a depth of ~5km and occurring as swarm activity. 90% of the observed activity occurred at depths shallower than 12km indicating that the brittle/ductile transition zone in this area is between 12-16km, which is similar to that in the Lake Bogoria area. Studies of the focal mechanisms of suitable events indicates a WNW-ESE extension direction across the Baringo basin and the presence of subvertical tensional fractures beneath the lake, which are suggested to be caused by the propagation of basic dykes into the crust. The inversion of local P-wave arrival-time data, for the upper crustal velocity structure beneath the Lake Bogoria and Lake Baringo areas, identified velocity lows associated with geothermal areas, a velocity high beneath the Goituimet basaltic lavas and a 10% velocity contrast across the Bogoria-Emsos-Legisianana fault. A model for the lithospheric structure beneath the Baringo basin is proposed with partial melt in the upper mantle beneath the rift, a dyke intruded lower crust with localised intrusions into the mid-upper crust in areas of geothermal and volcanic activity.

Chitinozoans have been recovered from throughout the Ludlow Series of the type area around Ludlow and adjacent regions. Collections contain 12 genera and 42 species including 11 new species: Calpichitina (Calpichitina) granosa, Eisenackitina toddingensis, Cingulochitina gorstyensis, Belonechitina mortimerensis, Rhabdochitina wakefieldi, Ancyrochitina aymestreyensis, Ancyrochitina gogginensis, Ancyrochitina narcissus, Angochitina milleri, Gotlandochitina dinhamensis, Gotlandochitina swifti. and 21 forms under open nomenclature. Conochitina dominates the late Wenlock and early Gorstian assemblages with Cingulochitina more common in the later Gorstian. The late Gorstian is characterised by species belonging to Belonechitina. Chitinozoan abundance and diversity decreases throughout the late Ludfordian, where Eisenackitina philipi often dominates assemblages. A detailed biostratigraphy has permitted a greater biostratigraphical resolution than was previously possible using chitinozoans. A scheme of 12 informal chitinozoan biozones is established for the type Ludlow Series. Chitinozoans have been used to test oceanic circulation models. Changes in chitinozoan assemblages have identified an event within the Middle Elton Formation (Gorstian Stage) and from the base of the Lower Leintwardine Formation (Ludfordian Stage). As the radiation event in the Gorstian occurs within the lithologically homogeneous Middle Elton Formation, it is concluded that chitinozoan faunas are not facies dependent. The faunal turnover in the Middle Elton Formation and the Lower Leintwardine Formation is believed to be related to changes in global climate and nutrient availability on the shelf. A distinctive chitinozoan assemblage is recorded from the top of the Lower Bringewood Formation and includes C. (Calpichitina) granosa, A. narcissus, Fungochitina pistilliformis and significant numbers of Angochitina elongata. This assemblage is repeated at the base of the Ludfordian. These species are regarded as Lazarus taxa and interpreted as responding to specific environmental conditions on the shelf. Due to the hermetically sealed nature of the chitinozoan vesicle and their chain forming habit, the idea that chitinozoans most likely represent the eggs of a marine metazoan is generally supported.

The young 9Ma Serifos pluton is the latest of a group of Miocene age medium- to high-K calc-alkaline granites, granodiorites and tonalites that were emplaced into the upper crust of the southern Aegean during back-arc extension. Serifos granitoid consists of a granodiorite, minor tonalite and abundant quartz-diorite enclaves. Most of these S. Aegean plutons have characteristics which vary between I-type and S-type, but their petrogenesis has been controversial. Here, different petrogenetic models are assessed using field criteria, major and trace element geochemistry, and Sr-Nd and O isotope systematics. The major element compositions of the Serifos granodiorie-tonalite and other I-type Cyclades granitoids are metaluminous to subaluminous, and have MgO, CaO, and TiO2 contents consistent with liquid compositions produced during amphibolite dehydration- melting experiments. Modelling of crystal fractionation processes using major elements would imply that removal of large amounts of plagioclase+hornblende +/- biotite is necessary to reproduce the Serifos evolved biotite-rich granodiorite from the quartz diorite magma; however, this is not consistent with the trace element variations. Conversely, mixing of the latter type of magma with a partial melt derived from the basement metasedimentary gneiss is consistent with both major- and trace-element trends, and new experimental data on melting of mixed amphibolite-sediment sources. The LILE elements particularly are controlled by the metasedimentary component. The Sr, Nd, and O isotope ratios of the Serifos and other Cyclades I-granitoids strongly indicate a crustal origin. Relationships between Rb/Sr, Sr, Nd, initial 87Sr/86Sr ratios, Nd/O isotope ratios are also consistent with binary mixing: magmas being derived from a mixed amphibolite/greywacke gneiss source available in the Cyclades basement, and with a significant metasedimentary contribution. Mixing of these two components in the source is a very important mechanism for explaining the distinct individual isotopic signatures of Serifos and the other Cyclades granitoids, but at the same time accounts for the continuous mixing trend (in terms of Sr, Nd, initial 87Sr/86Sr, Nd) seen for all I-type and S-type granites in the Cyclades, and indeed for most of the Eastern Mediterranean. The model could therefore be widely applicable. The geochemistry of the quartz diorite enclaves indicates some involvement of primary mantle-derived magma. Granite generation in the Aegean requires augmented thermal gradients, probably associated with lithospheric decompression from the early-Miocene to late-Miocene/Recent; this thermal perturbation may be a result of slab-breakoff. The increasing mantle heat input then accounts for the greater proportions of hornblende- dehydration melts incorporated in the progressively younger I-type granites (Naxos 12.5Ma, Mykonos 11.5Ma, Serifos 9Ma).

Lower Miocene crustal extension on the island of Paros resulted in the generation of two low-lying, north-vergent extensional detachment faults that exhumed deep levels of the ductile, partially molten crust in the footwall, whilst simultaneously accumulating lower Miocene age (Aquitanian-Burdigalian) sedimentary basin deposits in the hangingwall. Continued progressive extension, during the regional D2a event, led to the development of two elongate migmatitic gneiss domes; the NW Paros Dome (NPD), and the Main Paros Dome, (MPD) in the footwall of each detachment fault. Voluminous partial melting of the footwall during the D2b event resulted in the profuse emplacement of hybrid, Hs - type granitoids into the lower plate of the NW Paros extensional detachment fault. It is proposed that a similar, deep-seated D2b pluton / migmatite dome exists beneath the core of the Main Paros Dome, over which the Eastern Paros Detachment Fault was additionally uplifted and warped. The granitoids are derived from the concomitant dehydration melting of a mixed gneiss-amphibolite source during decompression of the lower plate rocks. The hybrid nature of the granitoid suite is reflected in their major- and trace-element variations and isotopic characteristics. Rb/Sr whole rock dating yields an errorchron age of circa. 21 Ma for the granitoid suite, which is correlated to the M2b upper amphibolite facies thermal event in the Aegean. The NW Paros Detachment Fault and associated footwall dome are here described for the first time, and provide valuable insights into the deformational mechanisms of a developing gneiss dome. The Monasteri-Naoussa section of NW Paros is thought to expose the deepest levels of the lower plate on Paros, and essentially provides a "tectonic window" into the ductile mid-lower crust. It is accepted that continental extension in the Aegean was superimposed onto an overthickened crust related to an Eocene HPLT D1 compressional event. It is proposed that D1 tectonic stacking of the Attic-Cycladic litho-tectonic units is related to a process of continuous subduction-accretion, as opposed to pure continental collision. New structural data are presented regarding the mid Miocene NW-SE directed horizontal compression phase on Paros, related to a regional, dextral simple shear event (D3). The D3 compressional event is associated with ubiquitous brittle structures that cross-cut and deform the earlier, higher temperature ductile fabrics related to D2 crustal extension.

Ostracods form a significant component of the Late Ordovician fossil fauna of the Ellis Bay Formation, Anticosti Island, Canada. Sixty-two ostracod species are identified, belonging to 36 genera. These include 14 species described as new, and 13 species described in open nomenclature. The ostracod fauna reveals new and important data bearing on the biostratigraphical, palaeogeographical and palaeoecological significance of the Ellis Bay Formation. The stratigraphic distribution of the ostracods permits the recognition of four successive intervals: (A) the Longiscula subcylindrica Biozone, (B) the Eurychilina erugoface Biozone, (C) the Tetradella anticostiensis Biozone and (D) an Interregnum. Stratigraphical intervals A, B and D can be related to Copeland’s (1973) ostracod biozonation for the Ellis Bay Formation. Biozone C is equivalent to three of Copeland’s (1973) ostracod sub-zones. Presence/absence analysis of the ostracod distribution patterns in the Ellis Bay Formation identifies two palaeoecologically discrete assemblages: an open marine assemblage characterises most of the formation (lithostratigraphical members 1 to 6); whilst a lower diversity assemblage typifies the uppermost Member 7. Biogeographically, the Ellis Bay Formation ostracod fauna is typically North American (Laurentian), but also shares affinities with the Late Ordovician ostracod assemblages of palaeocontinental Baltica and Avalonia.

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