bluuebunny/crossref_metadata_2025 huggingface dataset:
Irish Dinantian biostratigraphy: practical applications
Authors: Jones G. LL. , Somerville I. D.
Published: April 2008

For the last two decades there have been considerable advances in the dating and correlation of marine Dinantian carbonate sequences in Ireland, as elsewhere in Europe, primarily through the increased precision made possible by the use of microfossils, such as conodonts, foraminifers and miospores, together with macrofossils such as rugose corals. The advance was accelerated by the availability of boreholes up to 2km deep drilled by mineral exploration companies in Ireland who routinely use biostratigraphy. Detailed biostratigraphic biozonations are now established and are used for geological mapping and borehole zonation.

Data are assessed and attempts are made to highlight some of the practical problems encountered in locating Dinantian stage boundaries, recognizing biozones in Ireland, and suggesting correlations with other biozonation schemes in Europe. Although there are many difficulties in recognizing each of the stage boundaries in Ireland, two in particular present major problems — the Courceyan/Chadian and Holkerian/Asbian boundaries. From the work of Conil, Groessens and co-workers in Belgium, conodont and foraminiferal biozonation has been applied to the British and Irish Dinantian stages. Unfortunately, the bases of both the Chadian and Asbian stages rarely contain the zonal taxa. Also, at both stratigraphic levels, there are difficulties in comparing basinal and platform faunas. New biostratigraphic data in Ireland have permitted the recognition of two new intervals within the late Asbian Cf6γ Subzone, referred to informally as Cf6γ1 and Cf6γ2.

Until the Dinantian stages in Britain and Ireland are redefined biostratigraphically in the existing stratotype sections, or new stratotype sections are defined with faunal criteria, it is becoming more expedient and practical to recognize and define biozones in Ireland which can be identified and correlated with other Dinantian sections in continental Europe. This paper presents correlations with Belgian and Russian biostratigraphic schemes.
Fish assemblages in the Tournaisian-Viséan environments of the East European Platform
Authors: Lebedev O. A.
Published: April 2008

New fish material, including microremains from the Tournaisian-Viséan interval of the Moscow Syneclise, Northern Urals and Voronezh Anteclise of the East European Platform, comprises new species of Chondrichthyes:
Lissodus pectinatus
sp. nov., (?)
Diplodoselache antiqua
sp. nov.,
Eunemacanthus krapivnensis
sp. nov. Other fish taxa include
Stethacanthus obtusus
(Trautschold 1874), ‘
Orodus’ tumidus
(Trautschold 1874) and
Taeniolepis trautscholdi
(Chabakov 1927) are revised.

Tournaisian-Viséan deposits on the East European Platform are mostly represented by shallow marine or near-shore hyposaline facies with alternating salinity levels. Four major types of aquatic vertebrate environments are suggested: (1) continental fresh- and brackishwater; (2) lagoonal and estuarine with unstable salinity levels; (3) near-shore intertidal; and (4) off-shore neritic. Osteolepidids and actinopterygians are found in two or even three environmental zones, which suggests that they were eurybiontic and tolerant to changes of salinity, temperatures, hydrodynamics and other parameters of the basin. The most stenobiont forms are:
Diplodoselache, Ageleodus, Pycnoctenion
and dipnoans (1);
Deltodus, Streblodus, Copodus
and
petalodontids
(2);
Lissodus
and actinistians (4). The environmental distribution of the other groups is not as well expressed.
The Early Carboniferous chondrichthyans of the South Urals, Russia
Authors: Ivanov A.
Published: April 2008

Vertebrate remains including chondrichthyans were found in the Devonian/Early Carboniferous carbonate beds on the western and eastern slopes of the South Urals. Some of the Late Devonian forms (species of
Phoebodus
, acanthodians (
Devononchus
), placoderms and onychodontid sarcopterygians) disappear by the middle
Siphonodella praesulcata
conodont Zone. The ichthyoassemblages are considerably replenished by the new chondrichthyan taxa in the
Polygnathus communis carina
and
Gnathodus texanus-Mestognathus beckmanni
conodont Zones. The chondrichthyans were abundant among the vertebrate faunas of deep-water facies. A new species of chondrichthyan
Protacrodus aequalis
from the Late Famennian-early Tournaisian of the south Urals is described.
Volcano instability: a review of contemporary themes
Authors: McGuire W. J.
Published: April 2008

Active volcanoes are revealed to be dynamically evolving structures, the growth and development of which are characteristically punctuated by episodes of instability and subsequent structural failure. Edifice instability typically occurs in response to one or more of a range of agencies, including magma emplacement, the overloading or oversteepening of slopes, and peripheral erosion. Similarly, structural failure of a destabilized volcano may occur in response to a number of triggers of which seismogenic (e.g tectonic or volcanic earthquakes) or magmagenic (e.g. pore-pressure changes due to magma intrusion) are common. Edifice failure and consequent debris avalanche formation appears to occur, on average, at least four times a century, and similar behaviour is now known to have occurred at volcanoes on Mars and Venus. Realization of the potential scale of structural failures and associated eruptive activity has major implications for the development of monitoring and hazard mitigation strategies at susceptible volcanoes, which must now address the possibility of future collapse events which may be ten times greater than that which occurred at Mount St Helens in 1980.
Topographic characterization and monitoring of volcanoes via airborne laser altimetry
Authors: Garvin James B.
Published: April 2008

High spatial and vertical resolution airborne laser altimetry surveys of selected volcanic landforms have been used to investigate the metre-scale topographic characteristics of such features. Geodetic-quality airborne laser altimeter cross-sections of the Mount St. Helens dacite lava dome were acquired during the interval from 1987 to 1993; such data indicate that mass wasting of the flanks of the dome has outpaced episodic construction over the past seven years. Massive slumping of the south inner crater walls of the Mount St. Helens amphitheatre has been documented. Laser altimeter cross-sections of Mount Rainier have been compared with Mount St. Helens, Mount Adams, and with the Icelandic lava shield Skjaldbreidur in terms of local slope distributions, revealing basic similarities between the flanks of Rainier and St. Helens at length scales less than 5 m. When simple edifice shape parameters such as aspect ratio (
H/D
) are compared against total inferred edifice volume (
V
), Cascades stratovolcanoes such as Rainier and St. Helens fall along the extrapolation of the trend displayed for simple Icelandic lava shields. Cylindrical harmonic expansions involving laser altimeter cross-sections of volcanoes can be used mathematically to model the three-dimensional shapes of such features on the basis of only a few tens of coefficients and hence can be utilized to reduce the apparent extreme topographic complexity of major stratocones to terms that permit quantitative comparison with simpler volcanoes. In the future, geodetic airborne laser altimetry may be suitable as one of the many useful remote sensing methods for monitoring active volcanoes. A summary of the basic techniques associated with airborne laser altimetry in the context of volcanoes is provided.
Aseismic creep on faults and flank instability at Mount Etna volcano, Sicily
Authors: Rasà R. , Azzaro R. , Leonardi O.
Published: April 2008

This paper presents new data on the nature and significance of shallow fault creep in the Etna region. Sixteen sites where creep behaviour is obvious, have been identified, both from analysis of historical records, and from field surveys. Creep rates at each site vary considerably, from 0.5 to 2.3 cm a
−1
, and two extreme types of aseismic slip are recognized; (a) near-continuous, long-period movement along the aseismic segments of faults, and (b) spasmodic, short-lived, pre- and post-seismic movement related to seismically active fault segments. At most creep sites active displacements range from purely extensional to dip-slip. In some cases oblique-slip movements prevail, whereas purely strike-slip movements have been detected at only a single site. The overall creep kinematics indicate that surface creep on faults is a mode of discontinuous strain restricted to the faults displacing a sector of the eastern flank of the volcanic edifice bordered by the Pernicana fault, the NE Rift, the SE Rift and the Trecastagni-Mascalucia fault zone. We suggest that this mobile sector of the sea-facing flank of the volcano, including its uppermost clay-rich basement, is slowly sliding southeast under the control of a main deep-seated detachment surface.
Recent uplift of Ischia, southern Italy
Authors: Buchner Giorgio , Italiano Antonino , Vita-Finzi Claudio
Published: April 2008

Radiocarbon dating of fossil bivalves and corals from Ischia, in southern Italy, shows that parts of the island have undergone some 70m of uplift in the last 8500 years. Historical evidence reportedly suggests that during the last two millennia parts of the north coast were submerged by up to 4m whereas the southern coast underwent as much as 25 m of emergence. The
14
C results, which represent an average uplift rate of about 9 mm a
−1
, supplement studies based on potassium-argon dating of volcanic deposits which indicate that the Monte Epomeo horst at the centre of the island has risen by at least 800 m during the last 33 000 years, and micropalaeontological evidence, which points to some 700 m of emergence in the same time period. Eyewitness accounts suggest that some of the movement was coseismic. Prolonged uplift has created a steep topography prone to slope failure.
Calderas on Mars: characteristics, structure, and associated flank deformation
Authors: Crumpler L. S. , Head James W. , Aubele Jayne C.
Published: April 2008

Calderas and flank structures of martian volcanoes yield insight into general questions of volcano structural evolution and the underlying magma chambers in an environment where erosion is minimal. We have documented, through detailed geological mapping, the structures, associated volcanological features, and the stratigraphical relationships between the flank structures and caldera events during the building of each martian edifice. Two fundamentally different types of calderas are identified on Mars (the Olympus type and the Arsia type) that may represent end member variations in the size and depth of magma chambers.

Many of the flank structures adjacent to caldera rims are consistent with the predicted effects of magma chamber inflation as well as deflation that exert significant influences in the structural development of many volcanoes. Large-scale terracing and steepening of the upper flanks of the larger martian volcanoes may originate from magma chamber inflation and radial thrusting. Thus the endogenous component of volcano growth resulting from accumulated magma chamber growth may be significant.

Many of the deepest calderas are associated with evidence for voluminous eruptions elsewhere on the flanks and along through-going fissures and appear to result largely from evacuation and deflation of magma chambers without extensive precursor inflation. Draining of the magma chamber in these cases may be aided by the lateral propagation of magma in the form of shallow dykes up to several hundred kilometres in length and the associated formation of linear fissures. Nested caldera sequences, related flank pits, large-scale slumping, terracing, and sector structure are frequently arranged in linear patterns and are part of through-going eruptive lines or fissures several hundred kilometres in length that characterize several martian shield volcanoes. Fissures this long are interpreted to be dykes propagated outward from shallow magma chambers that have followed a minimum regional stress orientation. Comparison of the observed shape and orientation of caldera structures with orientation and style of flank deformation, and with the predictions from theory, indicate that regional stresses have probably been an important influence on the caldera and flank structures of martian volcanoes. The minimum regional stress orientation may be controlled largely by regional slopes associated with the Tharsis region and Elysium regions, and, in the case of Tyrrhena Patera, pre-existing radial fractures associated with the Hellas basin.
Crustal and mantle reflectors from Palaeoproterozoic orogens and their relation to arc-continent collisions
Authors: Snyder D. B. , Lucas S. B. , McBride J. H.
Published: April 2008

Two prominent geological features characterize the Palaeoproterozoic orogenic belts of Laurentia and Baltica: (1) Archaean cratons form the stable footwall during early stages of convergence and throughout crustal collision; and (2) juvenile, predominantly arc-derived crust was accreted to Archaean cratons through arc-continent collision. Seismic reflection profiling over the Svecofennian (Baltic Shield), Lewisian (British & Irish Isles) and Trans-Hudson (Canadian Shield) segments of an arguably once continuous orogenic belt has provided geometries of reflectors throughout both Palaeoproterozoic and Archaean crustal blocks as well as laterally coherent mantle reflectors. Two BABEL deep seismic reflection profiles within the Baltic Shield revealed structures along an irregularly shaped boundary between the juvenile 2.0–1.8 Ga Svecofennian domain and an Archaean craton (Karelia Province). An important result of the survey is the approximately 100 km horizontal offset between the inferred mantle suture, or palaeo-subduction boundary, and the geochemically-mapped crustal suture between juvenile Proterozoic crust and the Archaean craton. On the other side of the Atlantic, LITHOPROBE reflection profiles across the Trans-Hudson Orogen in central Canada reveal that 1.92–1.83 Ga juvenile arc and oceanic terranes of the Reindeer Zone form an allochthonous carapace about an Archaean basement block. Unexpectedly, the juvenile allochthons dip beneath the bounding Superior and Hearne cratons, defining a crustal-scale culmination in the core of the Orogen. The British and Irish Isles form an important bridge between the Palaeoproterozoic orogens of Laurentia and those of Baltica. Twenty deep reflection profiles on the continental shelf north and west of Scotland have traced a mantle reflector for over 800 km along its reconstructed strike, which is at a high angle to younger structures. This feature dips away from the reconstructed cratonic nucleus of Laurentia and may trace the Palaeoproterozoic (1.7–1.9 Ga) suture between the Archaean Lewisian block and accreted juvenile crust represented by the
c.
1.8 Ga Rhinns complex. A common theme that emerges from the integration of all these geological and seismic results is the role played by the Archaean lithosphere during arc-continent collision. In all cases studied, juvenile 1.9–1.8 Ga lithosphere was delaminated and its crustal flakes overrode the Archaean margins. This consistency reflects the relative strength and durability of Archaean crust/lithosphere, and suggests that large parts of the lithosphere underlying detached and flaked Palaeoproterozoic juvenile terranes, such as the Svecofennian or Reindeer Zone terranes, may be Archaean in age but modified during Proterozoic tectonism.
Rare earth and isotopic (Nd, O) heterogeneity of the Archaean mantle, Baltic Shield
Authors: Vrevsky A. , Krimsky R. , Svetov S.
Published: April 2008

Investigations of major and trace element geochemistry, whole-rock Sm-Nd and O isotopic composition of Archaean komatiites from the Baltic Shield show clear evidence of mantle source heterogeneity.

The komatiites were generated by 50–60% partial melting of the mantle at P
c.
35 kb, without garnet in the residue. Three different geochemical types of mantle source can be defined on the basis of HREE concentration: Type I, II and III sources yield komatiites with HREE abundances between 0.5–2, 2–3 and 3.5–5 Chondritic levels respectively. These types of mantle source can be correlated with three U-Pb zircon age groups of greenstone belts and their Nd and O isotopic composition.
Age and geodynamic aspects of the oldest rocks in the Precambrian Belomorian Belt of the Baltic (Fennoscandian) Shield
Authors: Bibikova E. V. , Skiöld T. , Bogdanova S. V.
Published: April 2008

The Belomorian Belt in the White Sea region was until recently considered the oldest core of the Baltic Shield but is now recognized to be essentially Late Archaean. This study reports U-Pb zircon ages and whole-rock Nd-isotopic results for aluminous metasedimentary gneisses and tonalitic-trondhjemitic-granodioritic intrusions. Metamorphic zircons from the aluminous gneisses date the earliest high-grade metamorphism to about 2.86 Ga. This was a low- to moderate-pressure granulite-facies event. Multigrain fractions of detrital zircons from these gneisses preserve little memory of protolith ages, but the whole-rock Sm-Nd DM-model ages are below 3.0 Ga which excludes dominantly Early to Middle Archaean detritus sources and indicates a short crustal prehistory. For the tonalitic-trondhjemitic intrusive rocks, U-Pb zircon and Sm-Nd model ages define two generations formed
c.
2.8 and 2.74–2.72 Ga ago. The oldest events in the Belomorian Belt can thus be correlated with Late Archaean developments in the adjoining Karelian Province further southwest in the Baltic Shield, but occurred at an active continental margin. This supports a Late Archaean accretional/collisional relationship between these two crustal segments.
Burwell domain of the Palaeoproterozoic Torngat Orogen, northeastern Canada: tilted cross-section of a magmatic are caught between a rock and a hard place
Authors: Van Kranendonk Martin J. , Wardle Richard J.
Published: April 2008

The northern segment of the Palaeoproterozoic Torngat Orogen is unique relative to the southern segment in that it is underlain by a 1910–1885 Ma suite of diorite-tonalite-granite rocks (DTG suite) emplaced into the margin of the Archaean Nain Province. Field and geochemical data indicate that it represents a subduction-generated Andean-type magmatic arc. Slivers of MORB-type, tholeiitic amphibolites and metasedimentary rocks within the DTG suite are interpreted as remnants of a backarc basin. Arc rocks are preserved in a tilted section from homogeneous, foliated tonalites at mid-amphibolite facies in the east, through gneissic tonalites, to massive orthopyroxene-bearing granitoid rocks of the Killinek charnockitic suite in the west. This assemblage is separated from the Archaean Rae Province, with which Nain Province collided, by a wide belt of turbiditic sedimentary rocks, now at granulite facies, known as the Tasiuyak gneiss. A younger suite (
c.
1865 Ma) of mafic tonalites and megacrystic metagranites within the Nain arc suite represents either syn-collisional plutons or late additions to the continental magmatic arc.

The southern segment of the orogen differs from the northern segment because it preserves no evidence of the DTG suite on Nain Province margin, but instead contains a widespread suite of calc-alkaline plutons across the Tasiuyak gneiss/Rae Province margin, dated as 1880 Ma. We develop two testable models to account for these along-strike variations and the presence of arc magmas on both sides of the suture. In
Model A
, a flip in subduction polarity from east-dipping at 1910–1885 Ma to west-dipping at
c.
1885 Ma is invoked, in which the
c.
1865 Ma suite of plutons in the northern segment are interpreted to represent syn-collisional magmas generated during accretion of the Burwell arc onto Nain Province. In
Model B
, the younger plutons in the northern segment may be interpreted as a late phase of the arc built on Nain Province, which we suggest may have been accomplished during a phase of double subduction immediately prior to collisional orogeny.

The Nain-Rae collision at
c.
1870–1860 Ma formed a doubly vergent thrust wedge, burying part of the arc in Burwell domain to depths of 35 km. During subsequent sinistral shear deformation at 1845–1822 Ma, Nain Province was buried obliquely beneath the still hot arc to depths of 40 km. At 1798–1780 Ma, crustal-scale disharmonic folding of the northern segment resulted in the simultaneous exhumation of the deeply-buried granulites of the arc and of the northwestern margin of the Nain Province across the Komaktorvik shear zone (KSZ). The KSZ was the site of significant translation between the Burwell domain and unreworked portions of the Nain Province, but it does not represent a fundamental plate boundary.
Accretion, rifting, rotation and collision in the North Atlantic supercontinent, 1700-950 Ma
Authors: Starmer Ian C.
Published: April 2008

Events in the North Atlantic region, from
c.
1700 to 950 Ma, are unified in a model compatible with palaeomagnetic results and Neoproterozoic supercontinent reconstructions. Following Labradorian-Gothian accretion, largely between 1700 and 1550 Ma, post-collisional effects continued until
c.
1500 Ma. Continental extension from
c.
1500 Ma onwards, related to ocean opening, developed granite-rhyolite provinces: the Central Metasedimentary Belt (Grenville Province) started to form at
c.
1425 Ma, with arcs outboard at
c.
1350–1300 Ma. Baltica started to separate from Laurentia and rotate at
c.
1240 Ma, causing crustal delamination of its leading edge, in South Norway. Here, subduction-related gabbroids intruded at
c.
1230–1225 Ma, as rotation proceeded. The Elzevirian Orogeny occurred at
c.
1190 Ma in the Southwest Grenville Province, marking the start of convergence of Baltica, in which backarc extension was accompanied by granites and bimodal volcanics. Collision at
c.
1080 Ma caused the Ottawan Orogeny which thrust accreted terranes northwestwards and closed the Mid-Continental Rift. In southern Baltica, complex deformation occurred. Post-collisional convergence and sinistral slip of Baltica against Laurentia (possibly related to convergence of Amazonia) caused thrusting, sinistral strike-slip faulting, folding and granitic intrusion until
c.
950 Ma. Post-tectonic granites intruded until
c.
900 Ma.
The relationship between 1.88 Ga old magmatism and the Baltic-Bothnian shear zone in northern Sweden
Authors: Wikström A. , Skiöld T. , Öhlander B.
Published: April 2008

New geochemical data and U-Pb ages for Proterozoic mafic and felsic dykes and their granitic host rocks in the Bläsberget Massif, proximal to the Baltic-Bothnian shear zone, indicate that these rocks are part of a terrane distinct from Svecofennian terranes in Central and Southern Sweden. The dykes comprise a NNE-trending swarm which can be traced over a strike length of about 20 km. Most of the mafic dykes are internally deformed and have systematic internal structures showing a sinistral horizontal component and an eastern-side-up sense of movement. This sinistral shearing is also observed within the nearby Baltic-Bothnian shear zone.

The mafic dykes have a uniformly basaltic composition. High content of elements such as Ti and Zr illustrate the typical ‘within-plate’ character. The felsic dykes are chemically homogeneous and have a SiO
2
content of about 77 wt%. High content of Y, Yb and Nb confirms the ‘within-plate’ character of the dyke swarm.

Zircons extracted from one of the felsic dykes indicate a U-Pb age of
c.
1.88 Ga. Approximately the same age has been obtained from the host rock granite and from a nearby occurrence of a similar late-orogenic granite. Since the dykes cross-cut most deformation and migmatite structures and most likely represent the waning stages of orogenic deformation in the area, it is evident that the timing of the orogenic events in the area is different and older than the Svecofennian development in central and southern Sweden.

A genetic relationship is suggested between the magmatism and the development of the Baltic-Bothnian shear zone.
Mesoproterozoic anorogenic magmatism in southern Norway
Authors: Menuge J. F. , Brewer T. S.
Published: April 2008

The 1500 Ma Rjukan Group of the Telemark Supracrustal Suite, south Norway, consists of a metamorphosed sequence of acid volcanic rocks (Tuddal Formation) overlain by a comparable thickness of metabasalts (Vemork Formation). Both acid and basic volcanic rocks have within-plate chemical compositions. The acid rocks have initial ε
Nd
values of 1.0 to 4.5, similar to the isotopic signature of some components of the Telemark gneiss complex, which is the probable basement to the Telemark Supracrustal Series. The metabasalts have initial ε
Nd
values of 3.0 to 4.3, indicating a depleted mantle source region. A mantle plume origin for the Rjukan Group is unlikely given the absence of high temperature igneous rocks such as picrites. Magma genesis by lithospheric extension following orogeny is therefore proposed, with the Tuddal Formation acid magmas derived by anatexis of arc-generated crustal rocks 1500–2000 Ma old, whilst the Vemork Formation basaltic magmas were derived by decompression mantle melting. The Rjukan Group is correlated with the granite-rhyolite province of the US midcontinent, implying large-scale continental rifting. The substantial volume of basic volcanic rocks suggests greater or more prolonged extension in south Norway than in North America.
Thermotectonic evolution of the Eastern Segment of southwestern Sweden: tectonic constraints from U-Pb geochronology
Authors: Connelly J. N. , Berglund J. , Larson S. Å.
Published: April 2008

The Eastern Segment forms a complex crustal terrane that occupies the southeastern part of the Southwest Scandinavian Domain adjacent to the less deformed 1.65–1.85 Ga Transscandinavian Igneous Belt (TIB). New U-Pb data from the Eastern Segment indicate that orthogneisses and granitoid rocks have protolith ages equivalent to the later magmatic phases of the TIB and that the earliest thermotectonic episodes in the Eastern Segment occurred between 1.70 and 1.61 Ga during the Gothian Orogeny. The comparable ages for Eastern Segment gneisses and TIB rocks represent permissive evidence for the hypothesis that the orthogneiss protoliths intruded into the western margin of Fennoscandia and are not exotic with respect to the pre-Gothian craton.

The eastern limit of Gothian deformation is thus interpreted to be an intracratonic deformation front that coincides with the later Sveconorwegian deformation front along the Protogine Zone south of Lake Vänern. The post-Gothian anorogenic period was interrupted, in at least the eastern part of the Eastern Segment, by a thermal and magmatic event at 1.47 Ga that generated granitic dykes and (re)crystallized titanite. Sveconorwegian U-Pb ages and field observations are compatible with a thrusting and exhumation of western supracrustal terranes over the Eastern Segment during the Sveconorwegian Orogeny, followed by isostatic unroofing and cooling of the lower deck at 950–930 Ma. Available, albeit limited, Sveconorwegian titanite ages in the Eastern Segment young from east to west, ranging from 950 to 930 Ma, and are substantially younger than those dated in the western terranes of SSD.
The provenance of pre-Scandian continental flakes within the Caledonide Orogen of south-central Norway
Authors: Emmett Trevor F.
Published: April 2008

A significant portion of the Caledonian nappe pile of south-central Norway is composed of tectonic flakes of continental crust older than the arkosic sediments of the Upper Precambrian-Lower Cambrian Hedmark and Valdres Groups. Models deriving these flakes from a suture zone S and SE of the Western Gneiss Region have found less favour than those deriving them from a root zone lying off the present-day coast line to the NW. Recent models propose that the largest flake, the Jotun-Valdres Nappe Complex, is a microcontinental suspect terrane structurally bounded above and below by ophiolitic sutures. The pre-Caledonian geological evolution of the Jotun-Valdres Nappe Complex and the Bergen Arcs is shown to be comparable to that of adjacent parts of the autochthonous Fennoscandian Shield, and to a putative root zone along strike from the Lofoten-Vesterålen Province. It is concluded that the Jotun-Valdres Nappe Complex and, by implication, related units in the Bergen Arcs and elsewhere, are not ‘suspect’ and are portions of the Mid to Late Proterozoic Baltoscandian crust, detached and thrust into position during the
c.
390 Ma Scandian (= late-Caledonian) orogenic event.
Stream sediment, soil and forage chemistry as indicators of cattle mineral status in northeast Zimbabwe
Authors: Fordyce F. M. , Masara D. , Appleton J. D.
Published: April 2008

Results of previous studies investigating the use of soil and forage chemistry as indicators of cattle mineral status have been somewhat equivocal, possibly due to the limited range of trace element concentrations in the areas investigated. This paper describes an investigation of the relationship between trace element concentrations in stream sediments, soils, forage (grass and leaves) and cattle blood (serum) in northeast Zimbabwe in order to identify which, if any, of the sample media provide a reliable guide to cattle mineral status. Soil, forage and cattle serum were collected from an area characterized by a wide range of Zn in stream sediments. The area was subdivided into three regions of relatively low, medium and high Zn concentration on the basis of stream sediment data and variations in the chemistry of cattle serum, forage, soil and stream sediment samples were examined. Significant correlations exist between element concentrations in stream sediments, soils and forage but there are no significant correlations with cattle serum. Although this lack of direct correlation may, in part, be due to a range of biological factors, it is suggested that high concentrations of Fe in soil and forage inhibit (i) the availability of P to plants and (ii) the absorption of Cu and Zn in cattle. This may have wide ranging implications due to the predominance of ferrallitic soils in many countries in tropical regions.
The environmental geochemistry of aluminium in tropical terrains and its implications to health
Authors: Smith B. , Breward N. , Crawford M. B. , Galimaka D. , Mushiri S. M. , Reeder S.
Published: April 2008

The link between environmental exposure to aluminium, mammalian toxicity and agricultural productivity has focused attention on the relationship between the environmental geochemistry of Al and its potential toxicity. Recent work has questioned the accuracy of previously reported baseline levels of aluminium in tropical well waters. In this work we investigate the validity of these observations and their influence on criteria for the determination of water quality.

Data are presented for two contrasting study areas in Uganda in which
c.
50 water samples were collected from a variety of water sources and subsequently analysed to identify concentrations of dissolved Al and of ligands that potentially control its environmental mobility and toxicty. Determinands included: pH, temperature, redox potential, conductivity, alkalinity, major and trace cations and anions and TOC.

Determination of Al by ICP-AES before and after sonication confirmed that sonication of samples filtered to 0.40 μm during sampling resulted in increased Al concentrations in solution. This effect is considered to be consistent with the aggregation of a non-labile colloidal Al on the addition of acid and confirms observations made by other researchers in Malawi. However, on-site analysis of samples using pyrocatechol violet indicated negligible free or labile Al present in the sampled waters and suggests that the majority of Al undetected by routine ICP-AES analysis is present in a non-labile form of relatively low potential toxicity.
Sources and pathways of arsenic in the geochemical environment: health implications
Authors: Thornton Iain
Published: April 2008

Arsenic is ubiquitous in the environment, being present in small amounts in all rock, soil, dust, water and air. It is associated with many types of mineral deposits and in particular those containing sulphide minerals. The most common arsenic mineral is arsenopyrite, FeAsS
2
. Elevated concentrations are sometimes found in fine grained argillaceous sediments and phosphorites. Some marine sediments may contain as much as 3000 mg kg
−1
. Arsenic is co-precipitated with iron hydroxides and sulphides in some sedimentary rocks, and is precipitated as ferric arsenate in soil horizons rich in iron.

This paper reviews current knowledge on the natural geochemical sources of arsenic in several countries where high concentrations in soils, dusts, surface and groundwaters may present a hazard to human health. The chemistry and behaviour of arsenic within the weathering zone are discussed in relation to pathways leading to human exposure.
Mobility of arsenic in groundwater in the Obuasi gold-mining area of Ghana: some implications for human health
Authors: Smedley P. L. , Edmunds W. M. , Pelig-Ba K. B.
Published: April 2008

Arsenic in drinking water from streams, shallow wells and boreholes in the Obuasi gold-mining area of Ghana range between < 2 and 175 μgl
−1
. The main sources are mine pollution and natural oxidation of sulphide minerals, predominantly arsenopyrite (FeAsS). Streamwaters have been most affected by mining activity and contain some of the highest As concentrations observed. They are also of poor bacteriological quality. Some of the streams have a high As(III) content (As(III)/As
total
> 0.5), probably as a result of methylation and reduction reactions mediated by bacteria and algae. Concentrations of As in groundwaters reach up to 64 μgl
−1
, being highest in deeper (40–70 m) and more reducing (220–250 mV) waters. The As is thought to build up as a result of the longer residence times undergone by groundwaters in the deeper parts of the aquifer. The proportion of As present as As(III) is also higher in the deeper groundwaters. Deep mine exploration boreholes (70–100 m) have relatively low As contents of 5–17 μgl
−1
, possibly due to As sorption onto precipitating ferric oxyhydroxides or to localized low As concentrations of sulphide minerals.

Median concentrations of inorganic urinary As from sample populations in two villages, one a rural streamwater-drinking community and the other a suburb of Obuasi using groundwater for potable supply, were 42 μgl
−1
and 18 μgl
−1
respectively. The value for the community drinking groundwater is typical of background concentrations of urinary As. The slightly higher value for the streamwater-drinking community probably reflects different provenance of foodstuffs and higher As concentrations of water sources local to the village. The low value obtained for the inhabitants of the Obuasi suburb, living close to and abstracting groundwater from the area of major mining activity, suggests that groundwater can form a useful potable supply of good inorganic quality provided that deep, long residence time sources are avoided.
Environmental impact of mining and smelting industries in Poland
Authors: Helios Rybicka E.
Published: April 2008

Mining and smelting industries cause tremendous devastation of both terrestrial and aquatic environments on the local and regional scale. Mines and smelters produce large quantities of waste, which must be deposited on land or into aquatic systems. The major effects in terms of contamination by heavy metals are in the pollution of air, soil, river water and groundwater systems. In Poland the most endangered surface water systems are the upper courses of both the Vistula and Odra Rivers, where the increase of contaminants, especially heavy metals and chloride ions, must be regarded as alarming. About 50% of surface water flows do not even meet the standards for quality class III. In 1990 the volume of wastes produced by mining and processing industries was more than 660 million tonnes of spoils and 490 million tonnes of tailings. It is estimated that in the period 1984–2000 about 900 million m
3
of spoils will be dumped in the area of the Upper Silesian Coal Basin alone. Taking into account the volume of sewage which should be treated, the emission of dusts and gases, and the volume of dumped wastes per km
2
, 27 ecologically endangered regions have been distinguished. Almost half of these correspond to mining and smelting districts.
Lacustrine sediment geochemistry as a tool in retrospective environmental impact assessment of mining and urban development in tropical environments: examples from Papua New Guinea
Authors: Nicholson Keith
Published: April 2008

Lake sediments represent an archive on chemical inputs into the environment. Baseline data for natural or background inputs can be obtained by analysis of deep (> 1 m) cores in conjunction with rigorous statistical procedures such as probability plots. Surface sediments illustrate the geographical distribution of the contamination, while shallow cores (< 1 m) permit estimates of sedimentation rate from the onset of contamination discharge. In Papua New Guinea lakes are particularly important as fish stocks which represent a vital source of protein, and any impact which may diminish these stocks is a cause for concern. Two lakes considered are respectively impacted by mining and urban development and show significant enrichments in metals and enhanced sedimentation rates. Surface enrichments in Cu in the mining-impacted lake attain levels of 348% over baseline; while the lake impacted by urban run-off and sewage discharge displays enrichments of 450% for Pb, 500% for Mn and 1100% for P. Sedimentary geochemistry is a potential tool in determining background or ‘natural’ metal inputs into a lacustrine system. Such data can permit environmental impact evaluations and legislative guidelines to be developed retrospective to development. In developing countries where urban and industrial growth has preceded environmental legislation, this technique may be employed to provide baseline data on which future discharge limitations or environmental controls may be built.
Clinical and epidemiological correlates of iodine deficiency disorders
Authors: Stewart A. G. , Pharoah P. O. D.
Published: April 2008

The iodine deficiency disorders, endemic goitre, stillbirths, abortions, congenital abnormalities, endemic cretinism, and impaired mental function, are found worldwide. Known for millenia, they currently put 29% of the world’s population at risk. The most important is cretinism, found in two forms. Neurological cretinism possibly develops due to an insult in early pregnancy, hypothyroid cretinism to an insult late in pregnancy or in early life.

The classical medical causes of environmental iodine deficiency, glaciation and leaching, do not adequately explain the prevalence and distribution of iodine deficiency disorders, nor have the new insights into the environmental chemistry of iodine been assimilated properly with medical knowledge. Joint studies would be of help.

The presence of various factors other than iodine deficiency in the causation of the disorders is recognized. These are often thought to be geologically related. Recent work suggests plate tectonics as the unifying factor, since iodine deficiency disorders are found along many plate collision zones. Concentration of major and trace elements as a result of plate subduction provides a possible source of goitrogens. A systematic search is needed.

The iodine goitrogen ratio could provide the link between environmental iodine and differing intensities of the iodine deficiency disorders found in affected communities.
A review of the geochemical factors linked to podoconiosis
Authors: Harvey R. , Powell J. J. , Thompson R. P. H.
Published: April 2008

Podoconiosis, or non-filarial elephantiasis, was named and characterized by the late Ernest Price (Price 1988, 1990). He described the clinical features of swelling and deformity of the legs associated with enlargement of the draining lymph nodes. Histopathological examination of these nodes showed them to contain bi-refringent particles. He identified the epidemiological association between the local type of soil and the disease, and finally he confirmed this association by microanalysis of the particles in diseased tissue, showing them to be sub-micron aluminosilicate and silica, which are characteristics of the clay fractions of the local soil. It remains unclear what it is within the heterogeneous range of microparticles identified in tissue, and soil factors, that is responsible for the toxicity, and what are the host factors that determine certain individuals to be sensitive to them. Prevention of progression of the disease could be achieved by preventing further uptake of particles by using adequate footwear.
History of hydrocarbon exploration in the Moray Firth
Authors: David M. J.
Published: April 2008

Exploration drilling in the Moray Firth commenced with the spudding of well 12/26-1 on 28 July 1967. From then until April 1994 (study cut off date) some 402 exploration wells and 153 appraisal wells have been drilled, proving up an estimated 5332 × 10
6
BOE entrapped within reservoirs ranging in age from Devonian to Eocene. It is estimated that 3087 × 10
6
BOE of these reserves are contained within the sandstone reservoirs of the Upper Jurassic.

The discovery of oil in the Witch Ground Graben, principally the Piper (1973) and the Claymore field (1974), not only established another new play in Upper Jurassic reservoirs for the United Kingdom Continental Shelf, but breathed life into an area previously ‘downgraded’ in terms of Jurassic prospectivity, and drilled initially for its Tertiary potential.

This paper reviews the history of hydrocarbon exploration in the Moray Firth. The author examines the main events that he feels have influenced exploration activity, the main play types that have been pursued, and the resulting distribution of reserves. Future potential is now believed to lie in the downthrown play at Upper Jurassic level in the Outer Moray Firth.
Genetic stratigraphy and sandstone distribution of the Moray Firth Humber Group (Upper Jurassic)
Authors: Harker S. D. , Rieuf M.
Published: April 2008

Upper Jurassic sandstones are of great economic importance in the Moray Firth, where 22 known fields originally contained almost three billion barrels of oil reserves. Principles of genetic stratigraphy provide the basis for recognition, correlation and mapping of eight Moray Firth Humber Group units. Genetic unit boundaries, which are biostratigraphically constrained, represent marine flooding surfaces or unconformities that resulted principally from tectonic/erosional episodes. Tectonic evolution in the Late Jurassic consisted of pre-rift and syn-rift phases, with accompanying differences in facies associations and sandstone distribution. Pre-rift sandstones comprise regressive pulses within a predominant overall transgressive setting, a coal-bearing deltaic/paralic succession is commonly succeeded by shallow marine deposits. The transgression commenced in the Callovian in the west and shoreline facies migrated eastwards through into the Kimmeridgian (
sensu gallico
), toward the junction with the Central North Sea graben system. Syn-rift sandstones are mostly turbiditic in origin, deposited during episodic Late Cimmerian tectonism, that started in the late Kimmeridgian and continued through into the Early Cretaceous. Only isolated remnants of the shallow marine equivalents to these deep marine systems have been found to data, such as those of Volgian age in the Glamis field on the Fladen Ground Spur.
Contrasting mineralogy of Upper Jurassic sandstones in the Outer Moray Firth, North Sea: implications for the evolution of sediment dispersal patterns
Authors: Hallsworth Claire R. , Morton Andrew C. , Dore Graham
Published: April 2008

Upper Jurassic sandstones in and adjacent to UK North Sea Block 15/21 (Outer Moray Firth) contain heavy mineral assemblages that provide evidence for differences in provenance, sediment dispersal patterns and depositional histories between the Ivanhoe/Rob Roy Terrace, North Halibut Graben, South Halibut Graben and Tartan Ridge. Variations are demonstrated using provenance-sensitive parameters, including apatite/tourmaline ratios, monazite/zircon ratios and garnet compositions. Seven different sandstone types have been identified on this basis. Scott and Piper sandstones (late Oxfordian-early Kimmeridgian) have contrasting mineralogies, indicating that they were derived from different provenances. However, the two sandstone packages lack internal stratigraphic variations, indicating that each is relatively homogeneous in terms of sediment supply. The succeeding Claymore sandstones (late Kimmeridgian-Volgian) display much greater variation, both regionally and stratigraphically. Heavy minerals suggest that the Main Claymore depositional system was more laterally extensive than that of the Upper Claymore, which was more locally developed and coalesced to a smaller degree. The most significant change in provenance took place with the onset of Main Claymore deposition, when the first major recycling of older Upper Jurassic sand took place. This indicates shedding of sediment from the Halibut Horst area, due either to uplift through intrabasinal tectonism or to a fall in sea level. Sediments in the South Halibut Graben contain minerals indicating exposure of granitic skarns on the Halibut Horst at this time. The area was compartmentalised in Upper Claymore times, with different dispersal systems operating north and south of the Halibut Horst, indicating that the horst continued to be an important control on sediment distribution.