ALBERT

Description / Table of Contents: N. H. Woodcock, D. G. Quirk, W. R. Fitches, and R. P. Barnes: In sight of the suture: the early Palaeozoic geological history of the Isle of Man / Geological Society, London, Special Publications, 160:1-10, doi:10.1144/GSL.SP.1999.160.01.01 --- T. D. Ford, Eva Wilson, and D. J. Burnett: Previous ideas and models of the stratigraphy, structure and mineral deposits of the Manx Group, Isle of Man / Geological Society, London, Special Publications, 160:11-21, doi:10.1144/GSL.SP.1999.160.01.02 --- Manx Group Stratigraphy and Lithofacies --- S. G. Molyneux: A reassessment of Manx Group acritarchs, Isle of Man / Geological Society, London, Special Publications, 160:23-32, doi:10.1144/GSL.SP.1999.160.01.03 --- P. J. Orr and M. P. A. Howe: Macrofauna and ichnofauna of the Manx Group (early Ordovician), Isle of Man / Geological Society, London, Special Publications, 160:33-44, doi:10.1144/GSL.SP.1999.160.01.04 --- N. H. Woodcock, J. H. Morris, D. G. Quirk, R. P. Barnes, D. J. Burnett, W. R. Fitches, P. S. Kennan, and G. M. Power: Revised lithostratigraphy of the Manx Group, Isle of Man / Geological Society, London, Special Publications, 160:45-68, doi:10.1144/GSL.SP.1999.160.01.05 --- D. G. Quirk and D. J. Burnett: Lithofacies of Lower Palaeozoic deep-marine sediments in the Isle of Man: a new map and stratigraphic model of the Manx Group / Geological Society, London, Special Publications, 160:69-88, doi:10.1144/GSL.SP.1999.160.01.06 --- Manx Group Sedimentation --- N. H. Woodcock and R. P. Barnes: An early Ordovician turbidite system on the Gondwana margin: the southeastern Manx Group, Isle of Man / Geological Society, London, Special Publications, 160:89-107, doi:10.1144/GSL.SP.1999.160.01.07 --- P. S. Kennan and J. H. Morris: Manganiferous ironstones in the early Ordovician Manx Group, Isle of Man: a protolith of coticule? / Geological Society, London, Special Publications, 160:109-119, doi:10.1144/GSL.SP.1999.160.01.08 --- N. H. Woodcock and J. H. Morris: Debris flows on the Ordovician margin of Avalonia: Lady Port Formation, Manx Group, Isle of Man / Geological Society, London, Special Publications, 160:121-138, doi:10.1144/GSL.SP.1999.160.01.09 --- R. P. Barnes, G. M. Power, and D. C. Cooper: The definition of sandstone-bearing formations in the Isle of Man and correlation with adjacent areas — evidence from sandstone chemistry / Geological Society, London, Special Publications, 160:139-154, doi:10.1144/GSL.SP.1999.160.01.10 --- Magmatism --- J. D. A. Piper, A. J. Biggin, and S. F. Crowley: Magnetic survey of the Poortown Dolerite, Isle of Man / Geological Society, London, Special Publications, 160:155-163, doi:10.1144/GSL.SP.1999.160.01.11 --- G. M. Power and S. F. Crowley: Petrological and geochemical evidence for the tectonic affinity of the (?)Ordovician Poortown Basic Intrusive Complex, Isle of Man / Geological Society, London, Special Publications, 160:165-175, doi:10.1144/GSL.SP.1999.160.01.12 --- Post-Ordovician Units --- M. P. A. Howe: The Silurian fauna (graptolite and nautiloid) of the Niarbyl Formation, Isle of Man / Geological Society, London, Special Publications, 160:177-187, doi:10.1144/GSL.SP.1999.160.01.13 --- J. H. Morris, N. H. Woodcock, and M. P. A. Howe: The Silurian succession of the Isle of Man: the late Wenlock Niarbyl Formation, Dalby Group / Geological Society, London, Special Publications, 160:189-211, doi:10.1144/GSL.SP.1999.160.01.14 --- J. D. A. Piper and S. F. Crowley: Palaeomagnetism of (Palaeozoic) Peel Sandstones and Langness Conglomerate Formation, Isle of Man: implications for the age and regional diagenesis of Manx red beds / Geological Society, London, Special Publications, 160:213-225, doi:10.1144/GSL.SP.1999.160.01.15 --- Tectonics and Metamorphism --- G. S. Kimbell and D. G. Quirk: Crustal magnetic structure of the Irish Sea region: evidence for a major basement boundary beneath the Isle of Man / Geological Society, London, Special Publications, 160:227-238, doi:10.1144/GSL.SP.1999.160.01.16 --- D. G. Quirk, D. J. Burnett, G. S. Kimbell, C. A. Murphy, and J. S. Varley: Shallow geophysical and geological evidence for a regional-scale fault duplex in the Lower Palaeozoic of the Isle of Man / Geological Society, London, Special Publications, 160:239-257, doi:10.1144/GSL.SP.1999.160.01.17 --- W.R. Fitches, R. P. Barnes, and J. H. Morris: Geological structure and tectonic evolution of the Lower Palaeozoic rocks of the Isle of Man / Geological Society, London, Special Publications, 160:259-287, doi:10.1144/GSL.SP.1999.160.01.18 --- G. M. Power and R. P. Barnes: Relationships between metamorphism and structure on the northern edge of eastern Avalonia in the Manx Group, Isle of Man / Geological Society, London, Special Publications, 160:289-305, doi:10.1144/GSL.SP.1999.160.01.19 --- Regional Comparisons --- R. P. Barnes and P. Stone: Trans-Iapetus contrasts in the geological development of southern Scotland (Laurentia) and the Lakesman Terrane (Avalonia) / Geological Society, London, Special Publications, 160:307-323, doi:10.1144/GSL.SP.1999.160.01.20 --- P. Stone, A. H. Cooper, and J. A. Evans: The Skiddaw Group (English Lake District) reviewed: early Palaeozoic sedimentation and tectonism at the northern margin of Avalonia / Geological Society, London, Special Publications, 160:325-336, doi:10.1144/GSL.SP.1999.160.01.21 --- B. J. McConnell, J. H. Morris, and P. S. Kennan: A comparison of the Ribband Group (southeastern Ireland) to the Manx Group (Isle of Man) and Skiddaw Group (northwestern England) / Geological Society, London, Special Publications, 160:337-343, doi:10.1144/GSL.SP.1999.160.01.22 --- Bibliography --- Eva Wilson: A bibliography of the geology of the Isle of Man / Geological Society, London, Special Publications, 160:345-361, doi:10.1144/GSL.SP.1999.160.01.23

Description / Table of Contents: Abstract The rocks of the Maru and Anka regions of northwestern Nigeria comprise a polycyclic, migmatite-gneiss, basement sequence with an infolded cover of low grade metasediments. Both basement and cover are intruded by a suite of syn-tectonic to latetectonic granites and granodiorites. Evidence from contrasting lithologies and geochronological data suggest that at least three depositional cycles may be represented in the Anka and Maru Belts of low-grade metasediments. An attempt is made to correlate these three cycles with the Kibaran (c. 1100 m. y.) and Pan-African (c. 550 m. y.) events. Structural similarities between the two belts are explained by continued reactivation of Kibaran basement structures during Pan-African times. Calc-alkaline volcanics of late Pan-African age are restricted to the Anka Belt. Recent work shows that volcanism in the Anka Belt is not all of late-orogenic type: a volcano-sedimentary pile, containing possible crystal tuff units, being intruded by acid-intermediate dykes and sills, and deformed during the Pan-African event. Syenitic plutonism restricted to the Maru Belt is shown to be post-tectonic. The recognition of a significant Kibaran event in the basement of northwestern Nigeria is in accord with workers who record a similar event in other parts of the Nigerian basement and in the Precambrian basements of Mali and the Ahaggar.

Description / Table of Contents: Abstract The Ubendian Orogenic Belt of southern Tanzania continues across the strike into northern Malawi where it is represented by the Misuku Belt. The Misuku Belt has been examined in two areas on the international boundary between northern Malawi and Zambia; the Mafingi Hills area and the western escarpment of the Nyika Plateau. In each area the Misuku Belt has been divided into three distinctive rock units: 1. the Misuku Gneisses which were metamorphosed in the epidote amphibolite to amphibolite facies, 2. the Jembia River Granulites, metamorphosed under conditions near to the triple point between the cordierite-granulite, granulite and amphibolite facies and 3. the post-tectonic Nthonga and Nyika Granites of the Mafingi Hills and Nyika Plateau respectively. Evidence is provided to show that the two metamorphic units are stratigraphic equivalents which were deformed and metamorphosed in different environments and subsequently placed in juxtaposition. The results of radiometric age determination made on the Misuku Belt provide no evidence of the true age of the granites nor of the time of metamorphism. The apparent ages are considered the result of overprinting during a later tectono-thermal event.

Description / Table of Contents: Abstract Recent work on the orogenic belts of Central Africa has revealed that the NE/SW trending Irumide Orogenic Belt probably intersects the older NW/SE trending Ubendian Orogenic Belt in the neighbourhood of the northern Malawi-Zambia international boundary. Two areas on this boundary have been mapped in detail; the Mafingi Hills area and the western escarpment of the Nyika Plateau. It was shown in an earlier paper that the older rocks in each area belong to the Ubendian Orogenic Belt. This paper is concerned with the overlying lowgrade metasediments of the Mafingi Group which are shown to belong to the Irumide Orogenic Belt. The first detailed description of the Mafingi Group is given and its stratigraphic, tectonic and metamorphic evolution is discussed. The Mafingi Group was deposited during a marine transgression across the peneplained roots of the Ubendian Orogenic Belt as a generally thin sequence of shallow-marine sandstones which grade up into argillaceous rocks. A much thicker sequence was deposited in the central part of the Mafingi Hills owing to the existence of the Mafingi basin which subsided at about the same rate as sediment was deposited; this structural depression was controlled by structures in the basement. The Mafingi Group was folded into the major NE/SW Mafingi syncline. This and associated small-scale structures, and also belts of phyllonite in the basement, are regarded as the result of block uplift in the basement. Metamorphism of the sedimentary rocks in the greenschist facies is shown to have taken place paratectonically with this first phase of deformation and to have preceded a second phase of folding on NW/SE axial planes. Radiometric K/Ar determinations on samples from the Mafingi Hills area are used in conjunction with previous geochronological data from northern Malawi to show that the Mafingi Group was involved in deformation and metamorphism for the first time about 1200 m. y. ago. This event is correlated with the Irumide Orogeny of eastern central Zambia. The absence of Irumide structures northeast of the Mafingi Hills leads to the conclusion that tectonic manifestations of the Irumide Orogeny terminated there.