bluuebunny/crossref_metadata_2025 huggingface dataset:
The transgression of the Lower Lias over the northern flank of the London Platform
Authors: Donovan D. T. , Horton A. , Ivimey–Cook H. C.
Published: December 2007

The progressive onlap of the Lower Lias (Lower Jurassic) onto the London Platform is analysed using cores and geophysical logs obtained from numerous boreholes in the south Midlands. The earlier beds of the Lias (including the pre–
planorbis
Beds) were regressive in relation to earlier Rhaetian strata. The Liassic transgression was first across Rhaetian strata, but the Upper Sinemurian overstepped onto the Palaeozoic basement of the Platform. In the Hettangian and early Sinemurian the periods of greatest transgression coincided with the deposition of more argillaceous units, with regressive or stillstand conditions more characteristic of the calcareous units.

The London Platform remained a comparatively stable area of very low relief during this time. It was subject to intermittent relative subsidence so that the transgression extended some 60 km onto its northern flank and resulted in an extension of over 14,000 km
2
in the area of deposition by the end of the Lower Pliensbachian Substage. The thickness of Lower Lias accumulated increases away from the Platform, where concurrent major downwarping in the Severn–Worcester, Cheshire, and Cardigan Bay basins allowed much greater amounts to accumulate.
Melting in the crust and upper mantle beneath the Kenya Rift: evidence from Geomagnetic Deep Sounding experiments
Authors: Banks R. J. , Beamish D.
Published: December 2007

A Geomagnetic Deep Sounding experiment in and around the Kenya Rift Valley has shown that telluric currents are concentrated by 3 regions with high electrical conductivity. Two of the anomalies are related to the rift structure, and the combination of different lines of geophysical evidence strongly suggests that the high conductivity is due to the presence of molten material in the rocks of the lower crust and upper mantle.

The shallower zone where melt is present, is located directly beneath the floor of the rift valley. Its upper surface is no deeper than 20 km; it may be as shallow as 5 km. The electrical conductivity is compatible with an average melt concentration of 5–10%, but could also be explained by discrete magma chambers where the concentration was much higher.

The deeper conductor is located to the E of the rift valley beneath the Aberdare Mountains, and possibly extends beneath Mount Kenya. The Geomagnetic Deep Sounding data suggest a depth of 100 km to the high conductivity body, which appears to correspond to the core (the region with the highest melt concentration) of a zone of more diffuse melting in the mantle, that is responsible for seismic and regional gravity anomalies, and which supports a part of the topographic elevation of the Kenya dome.
Topographic and geologic evolution of fracture zones
Authors: DeLong S. E. , Dewey J. F. , Fox P. J.
Published: December 2007

The age difference of oceanic crust on opposite sides of a fracture zone results in a depth differential and in different subsidence rates on the two sides. There is thus a component of dip-slip motion along the entire length of a fracture zone that decreases away from the central transform segment. The relief across a fracture zone will also change in a simple way due to the √age-dependence of the depth of oceanic crust. This dependence can also be expressed in terms of a (depth)
2
v. distance relationship that may be useful in identifying ambiguous ocean floor features as ancient fracture zones. Application of this procedure to the bathymetry of the well-studied Oceanographer Fracture Zone predicts spreading half-rates (12–13 mm/yr) in good agreement with the rate inferred from magnetic anomaly spacing; the model is not consistently successful, however, in predicting ridge axis positions or length of the transform offset. The relief across a fracture zone is also a factor in the evolution of sedimentary fill in the elongate bathymetric trough typical of many fracture zones. On the basis of the general geometric, structural, and igneous evolution of a fracture zone, events in the ridge–ridge transform segment, we have predicted the stratigraphic and structural relations that might be preserved at positions progressively distant from the spreading ridges. Other major complexities may arise from events such as ridge jumps or changes in rotation poles. The close spacing of fracture zones along some spreading ridges suggests that they could be preserved in ophiolite complexes, and stratigraphic and structural relations similar to those predicted have been observed in ophiolites from Newfoundland, Turkey, Cyprus, and the Apennines.
Oceanic transform structures and the development of Atlantic continental margin sedimentary basins—a review
Authors: Wilson R. C. L. , Williams C. A.
Published: December 2007

Atlantic sedimentary basins are classified into 3 types: (1) tensional rift basins (simple elongate basins and fracture zone end basins), (2) sheared margin basins (fracture zone parallel and fracture ridge dammed basins), and (3) taphrogenic basins. During the early phase of ocean opening, wrench tectonics occur ams offset continential margins, producing splay faulting relative to some transform directions; this influences the formation of fracture zones end and fracture zone parallel basins. Dammed basins develop against fracture zone ridges along large offset sheared margins. In taphrogenic basins of southern S America extant fracture zones follow Palaeozoic lines of weakness across the continent. Basement structures influence the location of some transform directions, particularly in the equatorial Atlantic, and there is some evidence to suggest a link between changes in subsidence rates and the shift in location of poles of opening on sedimentation rates. The asymmetry of basin development on opposing sides of the Atlantic is partially ascribed to the grain of the coastal geology and partly to differential subsidence rates caused by anomalous or asymmetric development of the adjacent ocean floor.
What is to be forecast: outbreak of eruption or possible paroxysm? The example of the Guadeloupe Soufrière
Authors: Tazieff H.
Published: December 2007

Forecasting the outbreak of a volcanic eruption is superfluous, since paroxysms occur not at the start but during the development of eruptions, and very few eruptions prove dangerous for neighbouring populations. It is important to predict whether or not an eruption will culminate in a climax, and if so, of what type, when and where. Only a naturalistic approach, and not a 'modelistic' one, can allow volcanologists with experience of erupting volcanoes to predict the development of an eruption. The 1976 eruption of Soufrière, Guadeloupe, is an example of the total failure of the modelistic approach and the reliability of the naturalistic one.
Tectonics of the Najd Transcurrent Fault System, Saudi Arabia
Authors: Moore John McMahon
Published: December 2007

The Najd Belt is a major transcurrent (strike-slip) fault system of Proterozoic age in the Arabian Shield. The belt is a braided complex of parallel and curved, en echelon faults. Complex arrays of secondary structures including strike-slip, oblique-slip, thrust and normal faults, together with folds and dyke swarms are associated with some major faults, particularly near their terminations. The secondary structures indicate that compressional and extensional/dilational conditions existed synchronously in different parts of the fault zone. The outcrop traces of faults and syn tectonic dykes are used to interpret the configuration of principal compressive stresses during formation of parts of the secondary fracture systems. Second order deformation was a series of separate events in a complex episodic faulting history. Comparison with model studies indicates that master faults extended in length in stages and periodically developed arrays of secondary structures. Propagation of the major faults took place along splay trajectories which inter-connected to form a sub-parallel sheeted and braided zone. Interpretation of the aeromagnetic maps indicates that the Najd Belt is broader at depth than the outcropping fault complex, and that more continuous structures underlie arrays of faults at surface. The fault pattern is mechanically explicable in terms of simple shear between rigid blocks beneath the exposed structures.
Pan African ages of some gneissic rocks in the Saudi Arabian Shield
Authors: Kröner A. , Roobol M. J. , Ramsay C. R. , Jackson N. J.
Published: December 2007

Models for the late Proterozoic to early Palaeozoic evolution of the Arabian Shield require a knowledge of the fundamental basement in the region. In the south-central Arabian Shield there are several areas of gneissic granitoid rocks which could represent such pre-Pan African basement. Whole-rock Rb-Sr isochrons for 2 of these areas are presented. The
Dahul gneisses
comprise an extensive terrain of granitic gneisses, migrnatites, foliated and unfoliated granites, dykes, and pegmatites. 5 gneissic rocks from Lat. 22º11'N, Long. 44º03'E define an isochron indicating an age of 599±43 Ma (586 ±43 Ma) with an initial
87
Sr/
86
Sr ratio of 0.7067 ± 20 and a MSWD of 0.13. Though the isotopic data could be compatible with certain models implying original ages of up to 1150 Ma, the field evidence and other relationships indicate that the age of c. 600 Ma was probably the age of intrusion. The Dahul gneisses therefore represent a major syntectonic batholith of Pan African age (s.s.) and of primitive derivation. The
Juojuq gneisses
are porphyroclastic rocks within the Najd fault zone. 6 gneisses from Lat. 21º03'N, Long. 43º 4 0 'E define an isochron with an age of 782 ± 26 Ma (766±26 Ma), an initial
87
Sr/
86
Sr ratio of 0.70297 ± 12 and a MSWD of 1.99. The bulk compositions, the textures and the isotopic data indicate that the rocks were originally plagioclase-rich granitoid plutonic rocks of primitive derivation. The isotopic data are compatible with original emplacement between c. 780 and 870 Ma ago. This age range is slightly greater than the 760–775 Ma (744–759 Ma) determined for the nearby Halaban lavas. The gneisses might therefore represent pre-Halaban intrusives, emplaced into unidentified crust. Pre-Pan African basement has thus not yet been identified in the Arabian Shield.
Age of the Loch Borrolan complex, Assynt, and late movements along the Moine Thrust Zone
Authors: van Breemen O. , Aftalion M. , Johnson M. R. W.
Published: December 2007

U-Pb analyses of zircons from 4 intrusions of the Loch Borrolan alkaline igneous complex in the Moine Thrust Zone closely define a discordia corresponding to an upper intersection age of 430 ± 4 Ma. No evidence has been found for an inherited radiogenic lead component. Structural relationships show that the error limits on the age bracket a late period of movement along one of the splays of the Moine Thrust. Alkaline igneous activity (documented back to 456 ± 5 Ma) along the western margin of the Caledonian Orogen in Scotland is related to crustal arching, directly and/or indirectly in response to orogenic compression. Synchronous thrusts directed towards the foreland appear to overtake the alkaline centres—thus resulting in their burial, metamorphism, deformation and/or transport. The change from alkaline to the more widespread (late Caledonian) granite magmatism appears to coincide with the end of thrust movement and the beginning of post-orogenic uplift.
The tectonic history of the Banda Arcs, eastern Indonesia: a review
Authors: Norvick M. S.
Published: December 2007

The Banda Sea is underlain by a small marginal oceanic plate, which is believed to have formed during the early Tertiary. Unlike other marginal seas to the N, the spreading of the Banda platelet was restricted by surrounding continental blocks. Its present complexity is a result of late Miocene–early Pliocene collision and obduction of the Banda Sea island arc system over the leading edge of the Australian–Irian continental plate. Transcurrent faulting on the northern limb of the collision zone may have accentuated curvature of the arc. Subduction and volcanicitv ceased after collision in the Timor and Seram sectors, but are still active at the eastern extremity of the arc.
The structural evolution of a Mesozoic continental margin, Othris Mountains, Greece
Authors: Smith A. G. , Woodcock N. H. , Naylor M. A.
Published: December 2007

The detailed structure of a telescoped Mesozoic continental margin sequence in the Othris (=Sub-Pelagonian) zone of eastern central Greece is described. Prior to thrusting in Upper Jurassic/Lower Cretaceous time, the Triassic and Jurassic facies showed an ordered lateral transition from a carbonate platform in the NE, through a submarine fan to a pelagic basin in the SW. The platform is autochthonous and has a continental basement; the pelagic basin probably lay in part on oceanic crust.

Carbonates on platform and fan were abruptly succeeded by siliceous deposits. Soft-sediment slumps in the siliceous sequence show a slope to the SW. Soon after this slumping, the slope reversed: olistostromes formed in front of a NE-sloping thrust pile advancing northeastward. Tectonic mélanges also accompanied thrust emplacement. The activation of the margin may be due to initiation of a NE-dipping subduction zone lying to the SW of the map area. Shortly after emplacement of the thrust stack, it was cross-folded, uplifted, eroded and by mid-Cretaceous time transgressed by shallow water deposits. Cenozoic thrusting in the area is absent, though minor rejuvenation of the NE-trending folds took place. High angle late(?) Cenozoic normal faulting is common.
Late Precambrian and Phanerozoic geology of Sierra Leone
Authors: Culver S. J. , Williams H. R.
Published: December 2007

The post-Archaean geology of Sierra Leone is reviewed and interpreted. Late Precambrian development of fault-controlled sedimentation of glacigenic, fluviatile, and marine deposits with minor volcanics culminated in the Rokelide thermo-tectonic event at 550 Ma, resulting in a mildly metamorphosed NNW-trending synclinorium. Rokelide deposits are overlain in northern Sierra Leone by near-horizontal, shallow water sandstones and glacio-marine rhythmites of late Ordovician age. Subsequent events were associated with sea-floor spreading activity, including development of coast-parallel dykes, a confluent cone-sheet, 2 alkaline complexes and kimberlites, all controlled by lineaments reactivated by the Mesozoic rifting of Africa from North America. Late Mesozoic downwarp of new continental margin produced a sedimentary basin into which marine, estuarine and fluviatile sediments were deposited.
Kyanite isograds of Grampian metamorphism
Authors: Chinner G. A.
Published: December 2007

A ‘Barrovian’ isograd Ky
50
based on the coexistence with kyanite and staurolite of biotite M/FM = 50 forms a SW–NE trending loop extending from Deeside into Perthshire; fault displacement of the southern limb suggests a north-westerly dip with high grade overlying low grade. The recumbent thermal anticline so delineated represents syn-metamorphic thermal disturbance, possibly due to the introduction of warm material with the upward and southward translation of the Tay nappe. In the ‘Moray’ zones, the putative pattern of isograd outcrop based on the argument that the andalusite-kyanite isograd marks the boundary between prograde
hydration
reactions and prograde
dehydration
reactions delineates a thermal trough correlated with the predominantly post-metamorphic Boyndie Syncline.
Structural frame work of the fore-arc basin, NW Sumatra
Authors: Karig D. E. , Lawrence M. B. , Moore G. F. , Curray J. R.
Published: December 2007

The fore-arc basin of the Sunda Arc off Sumatra is a strongly subsiding trough contained between the rising subduction complex and the elevated continental core. Up to 4 km of Miocene–Recent strata on the eastern flank of the basin have transgressed over an unconformity cut across a Palaeogene continental margin that was uplifted and structurally disrupted during the late Oligocene. The large step-like offsets of the palaeo-shelf edge, and probably some of the structural disruption, can be attributed to right-lateral strike-slip faults that splay across the fore-arc basin from the Sumatra Fault Zone. Offsets range up to 100 km+, producing marginal re-entrants that became sites of turbidite-filled basins trapped behind the growing Neogene accretionary prism. The larger re-entrants may be floored with oceanic crust, but the proximity of exposed subduction complex to the palaeo-margin precludes the existence of a continuous band of oceanic crust beneath the fore-arc basin.

The seaward flank of the fore-arc basin has migrated westwards during Neogene subduction, but not so much as the trench, and in a much more complicated fashion. During the early Miocene, the inner trench slope had a juvenile terrace-like morphology. By late mid-Miocene time, the trench slope break was near sea level and formed a shelf edge high. Thrusting and folding related to subduction probably decreased gradually upslope until late-Pliocene, when large flexures and E-directed reverse faults developed, marking an arcward shift in the rear or eastern boundary of the deformation associated with subduction. The episodic development of arcward-directed structures, involving previously stabilized fore-arc basin strata, suggests periods of increased stress levels along the base of the accretionary prism.
Dating mineralization
Authors: Ineson P.R.
Published: December 2007

Report of the Mineral Deposits Studies Group Meeting held at Burlington House, 15 May 1979. The meeting was organized by Dr P. R. Ineson.

The varied applications, advantages and disadvantages of Rb-Sr, K-Ar, U-Pb and Pb-Pb analytical dating techniques were outlined by the speakers.

Beckinsale admitted that in the study of the tin granites of SE Asia, the Rb-Sr technique had not been directly applied to the elucidation of the mineralization. In describing the varied environmental, mineralogical and geochemical characteristics of the ‘I’ and ‘S’ types of granites, he noted that the mineralization was either of the finely disseminated type in greisenized hosts or pegmatite vein occurrences. The SE Asian granites had been involved in basinal structures which had undergone a number of re-heating phases. K-Ar isotopic geochronology on the granites had given excessively young ages. It was advanced, therefore, that Rb-Sr techniques were more applicable to dating the intrusion of the granites, while K-Ar techniques may elucidate re-setting events due to subsequent hydrothermal activity.

Wilson reported various techniques which had been applied in order to date the uranium mineralization in northern Sweden. After outlining the general geological history of the Arjeplog–Arvidsjaur–Sorsele uranium province, he indicated that it was characterized by strong sodium metasomatism, development of skarn deposits and the presence of uranium and urano-titanites in both epigenetic and stratabound occurrences. U-Pb analyses on pure uraninite concentrates and whole-rock Pb-Pb dates had been used. The latter produced the most meaningful results, which were equated with the peak of
Comparison of major sequences of organic-rich mud deposition in the British Jurassic
Authors: Morris K. A.
Published: December 2007

The British Jurassic contains 3 major sequences of organic-rich shales: the Jet Rock Formation (Lower Toarcian), the Lower Oxford Clay (Callovian), and the Kimmeridge Clay (Kimmeridgian). In addition minor sequences are found in the Blue Lias Formation and the Shales-with-Beef Formation (Hettangian-Sinemurian).

The Lower Oxford Clay has the lowest average organic carbon content and was deposited in mildly oxygenated bottom waters. The sediment profile consisted of a thin upper oxidizing layer, with reducing conditions occurring a few cm below the sediment surface.

The Jet Rock Shales were laid down in very poorly oxygenated bottom waters. Here reducing conditions extended up to the sediment surface and this resulted in the preservation of a higher organic carbon content.

The Kimmeridge Clay shows a much wider variation in organic carbon content than the other examples, indicating accumulation in an environment which periodically fluctuated between mildly oxygenated and totally anoxic.
Structure and tectonic evolution of the Armorican Massif
Authors: Roach R. A.
Published: December 2007

Report of a meeting of the Tectonic Studies Group held at Burlington House, 14 March 1979. The meeting was organized by Dr A. J. Barber and Dr P. R. Cobbold.

The papers presented provided a timely review of the major advances during the last decade in understanding the structure and tectonic evolution of the Armorican Massif. Thestablishment of special research groups at the Universities of Rennes, Brest, Caen and Nantes, supported by the CNRS, has been the prime factor in this development. As a result, the geological evolution of this region is probably better understood than that of other Nercynian Massifs in central and western Europe.

The geological evolution of the Armorican Massif can be traced back more than 2000 Ma, beginning with the deposition of a Lower Proterozoic or late Archaean supracrustal sequence which was polyphase deformed, metamorphosed, and intruded by granitic and quartz-dioritic magmas between 2500 Ma and 1900Ma to produce the Pentevrian basement of the northern part of the Massif. Professor CognC portrayed the Pentevrian as a fragment of continental crust originally closely related to the W African Craton, which similarly exhibits magmatism around 2200 Ma to 1900 Ma (Eburnian event).

It was upon this basement and within adjacent oceanic domains that the Upper Proterozoic Brioverian Supergroup was deposited. The closure a portion of this ocean, the segment lying NW of Capdela Hague-Tregor Pentevrian axis and S continental crust represented by the Precambrian southern Britain, was, according to the model proposed by Auvray & Lefort, the result
Deformation and metamorphism in the Caledonide Orogen
Authors: Phillips W. E. A. , Johnson M. R. W.
Published: December 2007

This thematic set of 10 papers concerned with deformation and metamorphism in the Caledonian and Appalachian orogens arose from part of a conference which was held in Dublin in September 1978 as part of IGCP Project 27 (The Caledonide Orogen). The main topic of the conference was '
The Caledonides of the British Isles, reviewed'
and 82 papers from this have been published in a book of this title (Harris, A. L., Holland, C. H. & Leake, B. E. (eds.) 1980. Geol. Soc. Lond.). These papers on deformation and metamorphism complement that book by adding the dimension of the whole orogen to their topic. Authors were asked to summarise critical sectors of the orogen and to emphasise methods of analysis. The Scandinavian sector of the orogen receives most attention because much of the British Isles sector is covered in the companion book. The Appalachian sector will also receive major emphasis in a book entitled
'The Caledonides in the U.S.A.'
which will be published this year (Editor: D. R. Wones, published by: Department of Geological Sciences, 4044 Derring Hall, Virginia Polytjechnique Institute and State University, Blacksburg, Virginia 24061. U.S.A.). The Scandinavian East Greenland sector of the orogen will be covered in a companion book to be published after the symposium entitled
'The Scandinavian and Greenland Caledonides, reviewed'
to be held at Uppsala in the last week of August 1981.

The 10 papers here provide up to date summaries of the nature and timing of deformation and metamorphism in critical sectors along the
Caledonian regional metamorphism in Norway
Authors: Bryhni I. , Brastad K.
Published: December 2007

The autochthonous basement in Norway shows progressively greater plastic deformation towards the NW, but the in
situ
Caledonian metamorphism has surpassed low
-
grade conditions only in the western part of the country. The nappes, however, represent a telescoped sequence. They provide a broader sample of the total orogenic belt and contain extensive zones of low
-
grade and medium
-
grade rocks of the intermediate pressure series. Lack of adequate information on zones of incipient metamorphism, the true nature of isograd boundaries, and especially the age of many mineral assemblages, make compilation of a metamorphic map of the Norwegian Caledonides very difficult at the present stage.
Incipient metamorphism of Cambro-Silurian clastic rocks from the Jåmtland Supergroup, Central Scandinavian Caledonides, Western Sweden: illite crystallinity and 'vitrinite' reflectance
Authors: Kisch H. J.
Published: December 2007

The degree of incipient metamorphism in the Cambro-Silurian of the Jåmtland Supergroup (Eastern Complex) of the Jämtland Caledonides, from the Caledonian front autochthon westwards through the parautochthon towards the thrust front of the metamorphic main ('Western Complex') nappes, has been studied using: (
a
) determination of the illite crystallinity by X-ray powder diffraction on the K- and Mg-saturated –2 μm fractions; the low-grade limits of the anchizone and the 'opizone' of Kubler correspond to peak widths of c. 0.38° and 0.21°Δ2 (illite 001 diffraction peak) under the experimental conditions used; (
b
) determination of the rank of coaly particles in the clastic rocks by measurement of the 'vitrinite' reflectance using a reflected-light microscope with photomultipliers.

In the Indalsälven segment S of Iat. 63°30' N between Brunflo in the E and Undersåker in the W, and further N to Rönnöfors-Juvuln, 4 zones of illite crystallinity may be distinguished: (A) The Östersund-Krokom zone: mean 'saturated' 10 Å peak widths of ∅0.32°Δ2θ, the highest peak widths occurring in the easternmost part of the zone ('diagenetic' zone of Kubler). (B) The Norderö-Näldsjön zone: mean peak widths between 0.27° and 0.35° Δ2θ middle-anchizone of Kubler. (C) The Mattmar–Alsensjön zone: predominance of peak widths between 0.19° and 0.25° 2θ. (D) The Mörsil–Jårpen zone; predominance of peak widths of 0.21° Δ2θ characteristic of the 'epizone' of Kubler. This zone extends N to Rönnöfors–Juvuln, W of the Offerdal nappe.

'Vitrinite' reflectance values were measured on 35 samples. In illite-crystallinity zone A the predominant mean maximum reflectance ranges from 1.4-2.9% R
max oil
, corresponding to low-volatile bituminous coal to low-rank anthracite. In zones B, C and D the ranges of R
max oil
are similar, from 3.7 to 4.3%, corresponding to high-rank anthracite. Similarly high reflectances (4.2-4.5% R
max oil
) were found in 3 samples from the northern continuation of zone D. The comparative uniformity of the reflectances from zones B–D contrasts with the increase in illite crystallinities, particularly from zone B to C. Anatase was found in demineralization residues from zones A and B (together with rutile); in the residues from zones C and D rutile is the only titanium oxide.

The results are consistent with the hypothesis that the incipient metamorphism in the Jåmtland Supergroup was at least in part caused by the overthrust metamorphic allochthon, particularly the mainly medium- and locally medium to high-grade metamorphic Seve nappe. The association of the onset of the anchizone with semi-anthracitic to low-rank anthracitic coal ranks (c. 2.5–2.8% R
max oil
) is in agreement with the relationships found in several other areas of incipient regional metamorphism.
Timing of thrusting in the southern Appalachians, USA: model for orogeny?
Authors: Hatcher R. D. , Odom A. L.
Published: December 2007

Field and geochronological studies in the southern Appalachians reveal a space-time relationship of thrust and other large faults to their relative positions in the orogen, and their times of formation in relation to thermal-metamorphic peaks. Alleghanian thrusts of the Valley and Ridge-Cumberland Plateau are of the décollement type, resulting from compression of the foreland during the waning stages of mountain building.

At least one pre-metamorphic thrust is known in the Blue Ridge. Other pre-, syn-and late metamorphic thrusts have been recognized in the Blue Ridge, Chauga belt and Inner Piedmont, related to Taconic (450–480 Ma) metamorphism. Several later thrusts in the Blue Ridge and the Gold Hill–Silver Hill fault in the Piedmont have been dated as Devonian. Syn- to post-metamorphic faults in the eastern Piedmont are Hercynian. These were developed during or following the Hercynian metamorphism, which overprints earlier events.

Several large faults, notably the Brevard, record episodic movement histories spanning much of the Palaeozoic. The Brevard Fault had a pre- to syn-metamorphic (Taconic) movement history. Homogenization of Sr isotopes occurred in blastomylonites in the Brevard Fault after regional metamorphism, dated at 356 ± 20Ma. Both these early events involve ductile behaviour. Mylonites near the base of the Blue Ridge thrust sheet developed by 367 ± 20 Ma, yet elsewhere the allochthon locally overrides rocks as young as Carboniferous, indicating later (Alleghanian?) transport of the allochthon. Phyllonites in the Goat Rock–Bartlett Ferry fault zone are dated at
c
. 380±20Ma. One or more later events (Hercynian?) occur in the brittle realm. The Brevard Fault probably served as the root zone for early-to mid-Palaeozoic thrusts in the Blue Ridge. Later brittle deformation caused it to ramp over the rear of the Blue Ridge thrust sheet.

There is a space-time transgression of thrusting in the southern Appalachians, beginning with early pre-, syn- and late metamorphic (Taconic) thrusting in the metamorphic core. Devonian (Acadian) thrusting and high angle faulting also affected the metamorphic core. Later (Hercynian–Alleghanian) faults are restricted to the flanks of the orogen. This space-time relationship of faulting to thermal peaks and position in the orogen should be observable in other well-exposed orogenic belts and other portions of the Appalachian–Caledonide system.
Ferromanganese deposits in cores from the Kane and Atlantis fracture areas: possible relationships with hydrothermalism
Authors: Bonté P. , Lalou C. , Latouche C.
Published: December 2007

Cores from the eastern part of the area bounded by the Kane and Atlantis fracture zones, in the NE Atlantic Ocean, have been studied for their mineralogical, biostratigraphical and radio-chronological characteristics. Two of them contain a systematic association of pure palygorskite layers with ferro-manganese oxide concretions, alternating with normal carbonaceous sedimentation. Another contains manganese nodules having a nucleus of palygorskite. The possible origins of the palygorskite are discussed, and it is concluded that it is of hydrothermal origin. The close association of the palygorskite with the Fe-Mn concretions suggests a hydrothermal origin for these too. The episodic character of the deposits shows that hydrothermal activity occurred during relatively short periods, and that the last episode probably took place less than 100,000 years ago.
Geochemical studies on the leaching of metalliferous sediments from the East Pacific
Authors: Wakefield S. J.
Published: December 2007

A critical investigation has shown that the results obtained by selective chemical leaching techniques are very dependent upon the experimental conditions that are employed. Using a weak acetate leach, meaningful results have been obtained in the examination of deep sea metalliferous sediments.
A resurgent taphrogenic lineament of Precambrian origin in eastern Africa
Authors: McConnell R. B.
Published: December 2007

The East African Rift System is now generally regarded as a prime example of an early stage of continental separation. The alternative thesis, that it marks a Precambrian lineament affecting the whole of the lithosphere, has not been disproved and justifies further investigation. Recently published geological and geophysical observations support the alternative hypothesis of a resurgent Precambrian taphrogenic lineament extending 5000 km from the Afar triangle to the Orange River in South Africa.
The pneumoconioses due to mineral dusts
Authors: Wagner J. C.
Published: December 2007

The physiological and pathological changes associated with occupational exposure to mineral dusts (pneumoconioses) are briefly outlined. The minerals can be in the form of fumes, particulates, or fibres. Excessive exposure to mineral dusts results in scarring of the lung tissue and disturbance of the exchange of gases, leading to respiratory failure; in addition, this makes the lungs more sensitive to infections. The different patterns of scarring as a result of exposure to quartz, coal dust, or asbestos are described. Exposure to asbestos dust is associated with an excess of carcinoma of the lung and tumours of the pleura. There is epidemiological evidence from South Africa and Britain establishing that the pleural tumours (mesotheliomas) occur mainly in those exposed to crocidolite asbestos. In spite of numerous investigations the only factor implicated in the development of these tumours is fibre size. Current studies are concerned with the effects of other fibrous dusts of similar dimensions.
Geomedicine in Norway
Authors: Låg J.
Published: December 2007

The scope of geomedicine is briefly discussed. An interest in geomedical problems has existed in Norway since the last century, involving goitre in dry inland regions (
I
deficiency), and osteomalaci in cattle (P deficiency). Geographical variations in precipitation chemistry (including Mg, Na, Cl, Br, I and Se) are summarized. Deficiencies can be remedied by changes in fertilization and foddering. Areas with strong naturally poisoned soils and plants occur (involving Pb, Cu, Ni, Zn and Cd). Cases of industrial pollution are known at Odda (Zn, Pb, Cd, Hg, Cu, As, Se and F), Røros (Cu), Kongsberg (Hg), Evje (Ni), Modum (As), and aluminium factories (F).

Regional geochemical maps based on systematic sampling of forest soils are being produced (Oppland, Buskerud, Nord-Trøndelag), plus stream sediment geochemical prospecting maps which will also be valuable in geomedicine. A large project on the effects of acid precipitation is nearly completed. Norwegian research councils and a cancer organisation have started geomedical projects (e.g. analysis of human blood serum; the relationship between soil conditions and the chemical composition of small-grain and other plant foods). Cooperation between the Scandinavian countries in geomedicine has already begun. World-wide contacts between scientists are desirable in such a multi-disciplinary subject.
The health impact of geochemical alterations associated with coal resource development in midwestern U.S.A.
Authors: Kagey B. T. , Wixson B. G. , Gale N. L.
Published: December 2007

It is projected that over the next 5 years surface coal mining in the United States will increase drastically. Because coal is a dirty fuel, mining and other geochemical changes in the environment may lead to increased health hazards. An epidemiologic study of possible risk factors associated with these geochemical alterations is presented. Mortality data and water quality data are analyzed and presented in the form of computer generated maps. A predictive model for use by the Environmental Protection Agency pertaining to the identification and control of pollutants is discussed.
18
O/
16
O evidence for non-cogenetic magmas associated in a 300 Ma old concentric pluton at Ploumanac'h (Brittany, France)
Authors: Albarede F. , Dupuis C. , Taylor H. P.
Published: December 2007

An oxygen isotope study has been carried out on rocks and minerals from the 3 units which comprise the concentric Hercynian pluton of Ploumanac'h (Brittany, France). Lack of extensive low-temperature water/rock interactions enabled 3 non-cogenetic pulses of magma to be identified: (1) an early mantle-derived basaltic magma of alkaline affinity (δ
18
O ∼ 6); (2) biotite granites (δ
18
O ∼ 9) which form the bulk of the intrusion; and (3) a ring dyke of late, two mica-cordierite granite (δ
18
O = 12.3) that is clearly of crustal derivation. The δ
18
O data, together with published
87
Sr/
86
Sr results, suggest that the last 2 (granitic) pulses were generated in the continental crust. These results are not compatible with
any
models of closed-system fractional crystallization of a single parent magma-type, although they probably can be fitted into a 'mixing' model involving combined assimilation/fractional crystallization of continental crustal material by basaltic magma. A more likely explanation of the biotite granites is melting of amphibolites or granulites of the lower crust (possibly derived from volcano-detrital parent rocks), with the two-mica granites forming by melting of shallower, more pelitic metasedimentary rocks. The position of the Ploumanac'h pluton in a linear arrangement of related intrusions, together with the clear-cut structural control of its emplacement, are compatible with a model of melting at different levels in the crust and upper mantle, either associated with a mantle plume, or by a pressure release near the tip of a propagating lithospheric crack.
Rb-Sr whole-rock isochron ages of late Precambrian to Cambrian igneous rocks from southern Britain
Authors: Patchett P. J. , Gale N. H. , Goodwin R. , Humm M. J.
Published: December 2007

Rb-Sr age data are reported for late Precambrian to Cambrian igneous and metamorphic rocks from the border region of England and Wales. A felsic intrusion from Stanner Hill defines a good whole-rock isochron of 702 ±8 Ma. Uriconian pyroclastic rocks from the Wrekin area give a whole-rock age of 558± 16 Ma, while the late- or post-Uriconian Ercall granophyre from the same area gives a good whole-rock isochron of 533 ±13 Ma. A biotite cooling age from the nearby pre-volcanic Rushton Schist is consistent with these dates and suggests that the region cooled after the close of Uriconian magmatism at 536 ±8 Ma. All these results relate to widespread igneous/metamorphic activity in latest Precambrian to Lower Cambrian time.

The Ercall granophyre and Rushton schist are directly overlain by Lower Cambrian sediments and 533±13Ma is thus a maximum age for the deposition of these rocks.
Carbon and oxygen isotopic composition of structural carbonate in sedimentary francolite
Authors: McArthur J. M. , Coleman M. L. , Bremner J. M.
Published: December 2007

δ
13
C values for carbonate in francolite clearly distinguishes between authigenic varieties precipitated within anoxic sediments and diagenetic varieties produced by phosphatization of carbonates. δ
18
O values are characteristic of a deposit and, whilst apparently in equilibrium with pore-water in Recent deposits, are probably unreliable as palaeotemperature indicators generally. The isotopic composition of carbonate may therefore be used as a pointer to the mechanism of origin of francolite.
Mineralogy of carbonate fluorapatites
Authors: McClellan Guerry H.
Published: December 2007

The principal phosphate mineral in sedimentary phosphorites is carbonate fluorapatite of the variety francolite. Francolites exhibit several systematic isomorphous substitutions including sodium and magnesium for calcium, carbonate for phosphate, fluorine for oxygen, and hydroxyl for fluorine. These substitutions result in measurable variations of the crystallographic properties including unit-cell parameters and optical indices. Statistical models have been developed to relate compositional and crystallographic variations in the various francolites. Previous work has shown that francolite compositions are metastable with respect to fluorapatite. The effects of weathering, metamorphism and geological time causing systematic changes in francolite compositions are used as examples of these relationships.
Red bed genesis by lateritic weathering of glauconitic sediments
Authors: Parron C. , Nahon D.
Published: December 2007

Studies of some Mesozoic-Cenozoic 'red beds' in France and in W African basins (Senegal and Ivory Coast) show that they are the result of
in situ
lateritic weathering of glauconitic sediments. The alterations took place without destruction of pre-existing sedimentary structures. Glauconitic grains are weathered to ferruginous öoids consisting of Al-goethite, or are weathered to a kaolinite+goethite matrix. Original clay fractions are transformed into kaolinite and ferruginous oxi-hydroxides. Apatite nodules or beds gave rise to crandallite, millisite and variscite
Geochemistry of phosphatic chalks and hardgrounds from the Santonian to early Campanian (Cretaceous) of northern France
Authors: Jarvis Ian
Published: December 2007

Phosphatic chalks occur in erosional troughs cut into soft white chalks of late Coniacian to Santonian age and based by strongly lithified and mineralized hardgrounds. The dominant mineralogy consists of low-Mg calcite, carbonate-fluorapatite, α-quartz, glauconite and iron oxides. Lithification is geochemically discernible ~90 cm below the surface of the basal hardgrounds and results in a calcite-associated enrichment in Fe, Mn and Mg but depletion in Sr. Factor analysis indicates 4 major controls on the element distributions—carbonate-fluorapatite, clay minerals and silica, lithification, and iron minerals. White chalks are geochemically similar to modern coccolith oozes but hardgrounds have been indurated by the addition of a primary low-Mg calcite cement. Glauconitization was generally restricted to replacement of clay minerals during the early stages of hardground development while lithified carbonate remained in contact with seawater. Phosphatization occurred by the replacement of low-Mg calcite during burial of the hardground by an organic rich sediment. Mineralization was intimately related to organic processes.
Phosphatic öoids in the Upper Lias (Lower Jurassic) of central England
Authors: Horton A. , Ivimey-Cook H. C. , Harrison R. K. , Young B. R.
Published: December 2007

Ooliths and pisoliths (öoids) formed of concentrically laminated hydroxy-carbonate-fluorapatite with variable proportions of calcite, siderite and goethite characterize horizons in the Cephalopod Limestones Member of Toarcian age (Upper Lias) in central England. These öoids occur, with framboidal pyrite, in micritic limestone containing reworked sideritic biocalcarenite and grains of phosphorite and micrite. The öoids are mainly spheroids and ellipsoids but some are broken or compactionally distorted. Carbonate-apatite was co-precipitated with ferric hydroxide in a high-energy environment and probably recurrently replaced primary aragonite-öoids. The phosphatic öoids were reworked together with biocalcarenite and redeposited in a lower energy, deeper, offshore environment in which diagenesis occurred under progressively lower pH and Eh conditions.
Petrology of iron- and phosphorus-rich nodules from the E Australian continental shelf
Authors: Marshall J. F. , Cook P. J.
Published: December 2007

Phosphatic-glauconitic-goethitic nodules occur on the continental shelf of eastern Australia in water depths of
c.
200–300 m, and resemble relict phosphatic nodules from other continental margins. However, there is a striking morphological resemblance of late-stage carbonate-fluorapatite crystallites in the E Australian material to those off Chile and Peru, which are known to be Pleistocene–Holocene in age. There have probably been several phases of transportation, erosion, precipitation and cementation, and consequently the inter-relationships between the co-existing collophane, glauconite and goethite are complex.
Economic phosphatic sediments: mode of occurrence and stratigraphical distribution
Authors: Notholt Arthur J. G.
Published: December 2007

Phosphatic sediments are of considerable economic importance because, together with certain igneous rocks, they constitute the only raw material suitable for the manufacture of phosphate fertilizers and some phosphorus-based chemicals. They contributed about 84% of the total world production of 125 million tonnes of phosphate rock in 1978. Nearly all the output is from stratified marine deposits in which phosphate is invariably present as carbonate-fluorapatite (francolite). Pelletal textures are characteristic. Quality factors, other than phosphate content, are extremely important in determining commercial viability of individual deposits. Phosphatic sediments are widely distributed, the most important commercially being the Miocene–Pliocene deposits in Florida and the extensive Upper Cretaceous–Lower Eocene formations which form the Mediterranean Phosphate Province. Also being exploited are marine sediments of Precambrian, Cambrian, Ordovician, Permian and Jurassic age.
Olivine-dolerite intrusionsin the Fastnet Basin
Authors: Caston V. N. D. , Dearnley R. , Harrison R. K. , Rundle C. C. , Styles M. T.
Published: December 2007

Sills of olivine-microgabbro and olivine-dolerite 0.5–180 m thick intrude Lower Liassic (Hettangian–Sinemurian) sediments in the Fastnet Basin, a SW extension of the N Celtic Sea Basin, about Lat. 50°N, Long. 10°W. The evidence of 3 wells and 2300 km of seismic reflection profiles indicates 6 major sills and sill-complexes, and 3 possible igneous centres or plugs. A high-level sill may intrude Lower Cretaceous sediments, and one plug apparently deforms Cretaceous reflectors. K-Ar ages on separated biotites from a thick sill intruding Liassic sediments gave 170 ± 4 Ma (Bajocian). This sill contains 30% olivine (FO
70-73
), 20% clinopyroxene (magnesian salite), 45% plagioclase (An
60-78
), &, with accessory magnetite, ilmenite, edenitic hornblende, Ti-phlogopite, apatite, zircon, spinel (in olivine) and sulphides. Alteration to serpentine minerals, chlorite, sericitic mica and leucoxene is sporadic.

The magmatism in the Fastnet province thus appears to have been active from the mid-Jurassic to the early Tertiary, related initially to the time of initial rifting between the European and American plates, and subsequently to their final separation between Greenland and Rockall and associated Thulean magmatism.
Detrital blue sodic amphibole in Recent sediments, southern coast, Turkey
Authors: Mange-Rajetzky M. A.
Published: December 2007

Detrital blue sodic amphibole, sporadic lawsonite and pumpellyite occur in beach and river sediments between Gazipasa and Manavgat on the southern Turkish coast. This area lies S of the metamorphic Alanya massif, which contributes to the detritus, but blueschists have not previously been recorded in the region. The blue amphiboles have a provincial variation related to differing conditions during their formation. In the eastern region, in the vicinity of Gazipasa and Demirtas, homogeneous glaucophanes, sometimes with remnant Ca-amphiboles, are characteristic. In the western region the grains exhibit a considerable variation of optical and physical properties and are crossitic-glaucophane, crossite and occasionally magnesio-riebeckite. The efficacy of sedimentary mineralogy in reconstructing a hinterland is demonstrated.
Seismic and gravity surveys in the Lake Baringo–Tugen Hills area, Kenya Rift Valley
Authors: Swain C. J. , Khan M. A. , Wilton T. J. , Maguire P. K. H. , Griffiths D. H.
Published: December 2007

By using seismic and detailed geological data from a region of the KenyaRift where a complete Caenozoic rock sequence is exposed, it has been possible to interpret the gravity data and produce density models of a somewhat greater degree of uniqueness than has previously been possible. The configuration of the dense rocks responsible for the ‘axial high’ gravity anomalies is still not well defined but they seem to form a broad (20–35 km) zone within the basement, with strike along the Rift axis, and of limited average vertical extent (4–6 km). Such a model may imply a lopolith type of basic intrusion which would fit in with the small estimate of crustal extension across the Rift at this latitude which has been proposed. However, it is still possible to devise a dyke intrusion interpretation.