bluuebunny/crossref_metadata_2025 huggingface dataset:
Granulite-facies metamorphism in the Anatectic Complex of Toledo, Spain: late Hercynian tectonic evolution by crustal extension
Authors: BARBERO L.
Published: December 2007

The Anatectic Complex of Toledo consists of a heterogeneous suite of high-grade metamorphic rocks, mainly granulitic migmatites of pelitic composition and orthogneisses, and different types of syn-orogenic granitoids with minor associated basic rocks. None of the metamorphic rock types records evidence of the early prograde history, and only the peak and retrograde
P–T
conditions can be estimated. The intrusion of the syn-orogenic granitoids is either slightly before or synchronous with the metamorphic climax. These rock types thus can be used to make
P–T
estimates of the peak and retrograde conditions.

Microtextural analysis of reaction textures in conjunction with a petrogenetic grid, has enabled construction of an incomplete ‘clockwise’
P–T
path that is characterized by an isothermal decompression after or during the metamorphic peak temperatures. The peak estimates from different geo-thermobarometers are 800° ± 50 °C and 4–6 Kbar, the highest temperatures recorded in this part of the Iberian Hercynian Belt. It is proposed that this high-
T
/low-P metamorphism is at least partially related to an extensional process, possibly due to gravitational collapse of previously thickened crust.
Sub-greenschist facies metamorphism from the Variscides of SW Ireland an early syn-extensional peak thermal event
Authors: MEERE P. A.
Published: December 2007

Illite crystallinity studies on metaclastics from the Variscides of SW Ireland range in value from 0.18 to 0.25°Δ2
θ
indicating a metamorphic grade in the upper anchizone-lower epizone (
c.
275–325°C). Chlorite geothermometry yields a similar metamorphic temperature range (280–315°C). Combining these data with known overburden estimates for the area (
c.
5km) implies late Palaeozoic geothermal gradients in excess of 60°Ckm
−1
. Fluid inclusion studies on quartz veins in these metaclastics reveal two vein types characterized by fluid densities of 0.7–0.93 g cm
−3
(Group 1) and 0.9–1.0gcm
−3
(Group 2) respectively. This variation in fluid density is thought to be dominantly controlled by temperature, with Group 1 veins linked to late Palaeozoic extension and high geothermal gradients and Group 2 veins associated with subsequent Variscan deformation and lower temperature conditions.
Terrane boundaries in Ireland inferred from the Irish Magnetotelluric Profile and other geophysical data
Authors: BROWN C. , WHELAN J.P.
Published: December 2007

This paper presents explanations for some important geophysical features associated with terrane boundaries in the Iapetus Suture Zone in Ireland. The acquisition of data along the Irish Magnetotelluric Profile (IMP) provided the basis for a re-assessment of magnetic, gravity and seismic refraction results and further resolved sub-surface structures associated with terrane development during the Caledonian orogeny. The magnetotelluric data located two upper crustal conductors associated with the Fair Head-Clew Bay and Virginia magnetic Lineaments. One of the conductors probably extends along strike to Scotland, and its top surface may be associated with the T-reflector seen on the North East Coast (NEC) deep seismic reflection profile. The other conductor has a southeastern edge directly beneath a major throw in seismic basement, and defines the northern boundary of the Midland Valley Terrane in Ireland. The conductors and magnetic lineaments are probably due to black shales in sedimentary basins which have been thrust under the Avalonian and Laurentian continents during the closure of the Iapetus Ocean. The magnetotelluric data also suggest that the Southern Uplands magnetic lineament represents a crustal break but the Navan-Tipperary magnetic lineament is probably the consequence of a shallow, volcanic block-sedimentary trough structure.
Post-depositional evolution of mudstones l: early days and parental influences
Authors: CURTIS CHARLES D.
Published: December 2007

Ancient mudstones almost invariably record significant modification by very early diagenetic processes in the form of distinctive authigenic mineral assemblages. In the past, these have mostly been described from concretions—striking segregations of sulphides and carbonates self-organized into sub-spherical bodies. Thanks to relatively recent advances in electron microscopy (particularly back-scattered electron imagery) it is now a fairly simple matter to identify and characterize these same assemblages where they more commonly occur—dispersed through the fine-grained matrix of mudstones.

Earliest diagenesis is almost exclusively restricted to microbially-mediated redox reactions. Within recent unconsolidated sediments, these reactions take place in vertical sequences—the 'biogeochemical zones' of Claypool and Kaplan. Causal links can now be identified between early diagenetic mineral assemblages and microbial process zonation patterns. The patterns themselves vary systematically with depositional setting.

One very important aspect of depositional setting is rate of sediment accumulation. This rate control is more influential than previously suggested. It determines which diagenetic minerals will form
and
their amount as a proportion of the final sediment. This dependency permits early diagenesis and sea-level change to be linked through predictable lateral variation of biogeochemical zonation with sediment transport path (or bypass). It also provides clues as to the development of cementstones and horizons with discrete concretions—both of which reflect fluctuations in sediment accumulation rate. Finally, these relationships suggest why some mudstones are more likely than others to cause cementation in sandstones as a consequence of compactional de-watering and solute export.
3.26 Ga black smoker-type mineralization in the Strelley Belt, Pilbara Craton, Western Australia
Authors: VEARNCOMBE S. , BARLEY M. E. , GROVES D. I. , McNAUGHTON N. J. , MIKUCKI E. J. , VEARNCOMBE J. R.
Published: December 2007

Early Archaean (3.26 Ga) volcanogenic massive sulphide (VMS) deposits located within the low strain and very-low metamorphic grade Strelley greenstone belt, East Pilbara, Western Australia, contain exceptionally well-preserved sulphide textures which are directly analogous to those formed in black smoker chimneys at present-day submarine hydrothermal vents. The VMS deposits are associated with seafloor alteration zones in and below silicacarbonate laminites, at the top of a pile of tholeiitic to calc-alkaline intermediate and felsic volcanic rocks with trace element abundances indicative of modem subduction-related processes. VMS mineralization comprises Zn-rich sulphide lenses with significant Cu and barite, and variable Pb and Ag, above Cu-rich stringer zones, all of which are similar to Phanerozoic VMS deposits. Sulphide-sulphate mineralization implicates hydrothermal discharge into sulphate-bearing ocean waters.
Miocene NNE-directed extensional unroofing in the Menderes Massif, southwestern Turkey
Authors: HETZEL R. , RING U. , AKAL C. , TROESCH M.
Published: December 2007

Structural investigations in the central part of the Menderes Massif (Ödemiº-Kiraz submas-sif) reveal the presence of a large-scale, low-angle extensional shear zone with a top-to-the-N-NE shear sense. Regional ductile deformation was accompanied by the intrusion of two syntectonic granodiorites that have been dated with the
40
Ar/
39
Ar method. One hornblende isochron age of 19.5 ± 1.4 Ma and two biotite plateau ages of 13.1 ± 0.2 and 12.2 ± 0.4 Ma, respectively, constrain that extension was already active in the early Miocene. Successive tectonic denudation of the Ödemiº-Kiraz submassif resulted in the formation of a N-dipping detachment fault, in which ductile fabrics were severely reworked by cataclasis under decreasing temperature. Syntectonic Neogene sediments, currently exposed along the southern margin of the Gediz Graben, were deposited in the hanging wall of the extensional fault system and were tectonically emplaced onto the cataclasites during progressive exhumation. Minor rotation (< 15°) of the detachment fault to its present gentle dip of
c
. 15° caused southward tilting of the sediments. Ongoing NNE-directed extension created a steep normal fault that truncates the detachment fault and constitutes the southern boundary fault of the Gediz Graben.
Two-stage deformation of the Mont-Louis-Andorra granite pluton (Variscan Pyrenees) inferred from magnetic susceptibility anisotropy
Authors: BOUCHEZ J. L. , GLEIZES G.
Published: December 2007

The Mont-Louis-Andorra granodiorite pluton, Eastern Pyrenees (France, Andorra and Spain) was the subject of a thorough study of its internal structures, principally the measurement of the anisotropy of its magnetic susceptibility and the classification of its microstructures. Regularly spaced sampling (281 sites) allowed the precise mapping of the susceptibility magnitudes, consistent with mapped rock types. The magnetic structures fall into two distinct families which occur in separate parts of the pluton and have different microstructures.
Family I
is observed almost everywhere and has close to horizontal lineations, remarkably constant in NE–SW azimuth. Magmatic to submagmatic microstructures characterize these rocks. In contrast,
family II
is confined within NW–SE-trending corridors, where moderate to steep NW-plunges of the lineations are recorded, and subsolidus microstructures are observed. Magnetic structures of family I are argued to equate with the kinematic framework of the deforming magma during its emplacement. Family II structures represent a late to post-consolidation reworking, and therefore record a second stage of deformation in the pluton. It is concluded that magma emplacement was related to a NE–SW-trending strike-slip and/or thrust fault system, coeval with the SW-verging thrust episode documented in the Pyrenees. The second stage corresponds to dextral shear movements with a thrust component on NW–SE-striking planes. Corridors containing family II structures are shear zones responsible for dissection of the massif into three blocks, the eastern block representing the former base, and the western block the top of the pluton. Restoration of the pluton's shape along these corridors demonstrates the importance of the early Variscan NE-SW kinematic direction. Because the family II structures that form shear zones affecting the pluton have similar orientation and kinematics as the compressive, steep main-phase of deformation ubiquitous in the Pyrenees, the pluton of Mont-Louis–Andorra was probably emplaced before this main-phase of deformation.
Galena lead isotopic variations in a Mesozoic–Cenozoic Andean arc, Antarctic Peninsula
Authors: WILLAN ROBERT C. R. , SWAINBANK IAN G.
Published: December 2007

The Antarctic Peninsula magmatic arc was the site of Andean-type subduction from at least Silurian times to the late Cenozoic. Hydrothermal galenas from eight localities in accretionary complex, arc volcanic sequences and plutonic rocks along a strike length of 1100 km have restricted
206
Pb/
204
Pb,
207
Pb/
204
Pb and
208
Pb/
204
Pb compositions (18.628–18.734, 15.599–15.673 and 38.441–38.689 respectively) plotting on crustal average growth curves. The local geological setting, and comparison with Andean leads, suggest that the major source reservoir was isotopically homogeneous sedimentary rocks forming the late Palaeozoic–Triassic accretionary complex. The lead data suggest that old continental basement is absent at least as far south as 65°S.

Galenas from a large (13 × 2 km) epithermal vein system on Hurd Peninsula fall in three populations: a main isotopically homogenous array (18.643, 15.647 and 38.503, 2σ = 0.020, 0.020 and 0.050,
n =
33) interpreted as a large hydrothermal system that extracted homogenous leads from early Triassic turbidites. Two smaller sub-populations, with more radiogenic
206
Pb/
204
Pb, are associated with mid- to late Cretaceous intrusive rocks, and may represent either local contributions of magmatic lead or younger hydrothermal episodes. In western Graham Land, two localities associated with mantle-derived mafic intrusions of Cenozoic age have low
207
Pb/
204
Pb and
208
Pb/
204
Pb ratios indicating addition of some mantle-type lead.
Caledonian transpressional terrane accretion along the Laurentian margin in Co. Mayo, Ireland
Authors: HARRIS D. H. M.
Published: December 2007

The Highland Border–Fair Head–Clew Bay–Baie Verte–Brompton Suture (Clew Bay Suture) on Achill Island, western Ireland is an E–W-trending zone of vertical, ductile dextral transpression bounding the southern edge of the Dalradian terrane. The Achill Dalradian, a sequence of coarse-grained psammite overlain by conglomerate, quartzite, schist and limestone, disposed in recumbent curvilinear folds, represents Laurentian continental margin deposits which were translated westward during deformation, parallel to the suture trace. Studies of fabric development and albite porphyroblast growth indicate that E–W dextral transpression and west-directed recumbent folding were synchronous, and are interpreted as separate expressions of the same NW-directed terrane impingement event. This process of terrane-docking was marked by a
c
.4kbar phase of decompression

Within the suture, four separate terrane-slivers are recognized. The presence of pyrope-garnet and crossite-amphibole within two imply the Clew Bay Zone experienced sufficient displacement to exhume rocks from deep lithospheric-levels. In addition, the extensive retrogression and destruction suffered by these remnant high pressure mineral assemblages during the albite-generating transpressional phase, implies that ductile deformation was enhanced by the introduction of fluid into and along the suture zone during impingement.
Drainage development and sediment supply within rifts, examples from the Sperchios basin, central Greece
Authors: ELIET P. P. , GAWTHORPE R. L.
Published: December 2007

Drainage systems juxtaposed with modern depositional environments within the Sperchios rift allow detailed analysis of the relationships between drainage catchments. sediment supply and alluvial fan/fan delta geometries. Prominent footwall escarpments within the rift are created by E–W-trending normal faults, and variations in the topography of these escarpments are related to fault segmentation and bedrock lithology. Drainage catchments within the rift are classified on the basis of morphology, area, bedrock lithology and relationship to fault geometries. Five drainage domains can be identified within the Sperchios rift: (i) footwall, (ii) hanging wall, (iii) transfer zone, (iv) axial and (v) karst domains. Bedrock lithology has a major control on the size of catchments in all drainage domains. In addition, topographic lows associated with transfer zones along the border fault are sites of major drainage catchments and act as conduits for sediment supply to the rift. Variations in drainage catchments, the resultant sediment supply and accommodation development along the rift produce a range of stratigraphic architectures. Along fault segments, low sediment supply and high subsidence rates lead to aggradational sequence sets, whereas progradational sequence sets develop at transfer zones where rates of sedimentation are high and the rate of subsidence is low.
Incoming editorial
Authors: Fairchild Ian J.
Published: December 2007

It is a pleasure to record my thanks to Mike Le Bas for his leadership of the editorial team over the last 13 years. Many initiatives and responses have been made over that time, as you can read in his outgoing editorial. These changes and the careful attention paid to editorial standards have maintained the
Journal's
fortunes in the face of increasing competition from a variety of specialist and generalist journals. Further changes will occur in the years to come and it is part of my function to ensure that the editorial board review all new approaches that may benefit the
Journal.
The input of you, the reader, will be welcome.

Mike undertook the Herculean task of checking in detail the final versions of all the papers published in the
Journal.
I will instead rely on a combination of the professional skills of Angharad Hills as Staff Editor and the individual scientific editors. In order to assign both credit and responsibility, the names of the latter now appear at the end of the articles with which they have dealt. The buck stops with me in cases of difficulty.

In the interests of all the subscribers of the
Journal
we aim to maximize the quality of the science that we publish. We also want science that is of broad interest to earth scientists. This includes articles in which a variety of different types of data, or data from different specialisms is synthesized. Typically these are applied to a region, but their
Outgoing editorial
Authors: Le Bas M.J.
Published: December 2007

A review of how the
Journal
fared over the last decade or so is appropriate as I hand over the reins to Ian Fairchild, the incoming Chief Editor. He is well qualified and I wish him well in this task.

Ten years ago, the Journal altered its format from crown quarto (180 mm × 250 mm) to demy quarto (210 mm × 276 mm), a move which improved display of diagrams and tables, and provided better use of print space on paper that was, and still is, becoming increasingly expensive. The change fortunately provoked only minor irritation about space on library shelves. The format had changed before. Before 1963 it had been octavo (140 mm × 215 mm) right back to volume 1 in 1845. Following the major revival of the
Journal
in 1970 under Bill Bishop and the Scottish Academic Press, and the increase from quarterly to six issues per annum, the move to demy quarto format in 1986 was undoubtedly right. The format change was greatly assisted by the late Keith Bowker, of Blackwell Scientific Publications who were our publishers at that time and with whom we had very happy working relations.

Three years later, the good financial fortunes of the Geological Society enabled it to set up the Geological Society Publishing House. Premises in Bath were found, staff appointed, and so the Society became its own publisher; and that has flourished. The whole procedure of handling submissions, editing them and seeing them through the proofing stages became
Inversion tectonics of the Variscan foreland of the British Isles
Authors: CORFIELD S. M. , GAWTHORPE R. L. , GAGE M. , FRASER A. J. , BESLY B. M.
Published: December 2007

Late Westphalian inversion structures on the Variscan foreland display wide variations in orientation that are the product of the underlying basement grain. The orientation of the major basement lineaments in relation to the direction of maximum shortening also determined the severity of deformation of the inverted basins. NE–SW-trending faults were oriented roughly perpendicular to the NW–SE to NNW–SSE direction of maximum shortening determined from thrust transport directions in the Variscan orogen to the south. As a consequence, NE–SW-trending basins in the Variscan foreland have been strongly inverted, the Silesian post-rift fill has commonly been expelled from the basins and the syn-rift sediments have been deformed by chevron folds (Dublin and Bowland Basins). In contrast, the N–S- and NW–SE-trending faults were oriented more obliquely to the direction of maximum shortening and, as a consequence, display a significant component of oblique slip. This oblique slip component is manifested as en-echelon periclines and flower structures. In general, the N–S- and NW–SE-trending basins were less strongly inverted and the Silesian post-rift fill has been retained.
Precise U–Pb zircon dating of a post-D2 meta-dolerite: constraints for rapid tectonic development of the southern Adelaide Fold Belt during the Cambrian
Authors: CHEN Y. D. , LIU S. F.
Published: December 2007

Numerous MORB-like mafic dykes, plugs and sills intruded the Kanmantoo Group and older meta-sediments of the southern Adelaide Fold Belt from pre-D1 to post-D2 during the Delamerian orogeny. A post-D2 meta-dolerite yields a precise U–Pb zircon age of 510 ± 2 Ma. This age, combined with a published SHRIMP zircon age of 526 ± 4 Ma, reveals a rapid tectonic evolution of the fold belt during the Cambrian: events including the thick Kanmantoo Group's deposition, major mafic magmatism, low-P/high-
T
regional metamorphism and multiple deformations all took place from about 526 to 510 Ma. This rapid evolution supports the suggestion that the heat source for the metamorphism originated from continental extension associated with mantle upwelling and mafic magmatism.
Dating the transition of smectite to illite in Palaeozoic mudrocks using the Rb–Sr whole-rock technique
Authors: EVANS J. A.
Published: December 2007

The interpretation of mudrock Rb–Sr whole-rock regression ages using stratigraphically well-constrained samples from the Ordovician and Silurian of central Wales is re-examined. Two new Rb–Sr whole-rock regressions are presented along with K–Ar and Rb–Sr data from the <2 μm illite fraction of samples from these and published whole-rock suites. Eight K–Ar ages from the <2μm fractions give ages which show a normal distribution, with a mean and quadratically combined 2σ error indicating a Devonian age of 399 ± 3 Ma. Rb–Sr whole-rock ages are less consistent, giving 431 ± 10, 428 ± 14, 414 ± 6 and 403 ± 15 Ma. Rb–Sr data from the illite fractions do not generate a linear array. The Rb–Sr whole-rock isochron ages are interpreted as dating the time of passage of the rock through the smectite–illite transition because the radiometric ages correspond well to the estimated time of this reaction. Other explanations of the ages, such as the possibility that they were generated by mixing, or that they date sediment provenance ages, peak metamorphism, or cleavage, are rejected on geological grounds.
Significance of a hiatus in down-temperature fabric development within syn-tectonic quartz diorite complexes, Channel Islands, UK
Authors: TRIBE IAN R. , D'LEMOS RICHARD S.
Published: December 2007

Detailed fabric development histories have been deduced for Neoproterozoic foliated quartz diorite complexes of the Channel Islands, UK. The plutons were emplaced during regional (D2) deformation. Magmatic fabrics, formed at low crystal contents (pre-rheologically critical melt percent) are only locally preserved due to overprinting by solid-state deformation which occurred at moderate temperatures (400–550°C). This is demonstrated by brittle microcracking of plagioclase and amphibole with only local ductile bending and dynamic recrystallization; marginal recrystallization and myrmekite development on alkali-feldspar; ductile deformation of quartz to form types 2–3 ribbons; quartz recrystallization by sub-grain rotation associated with
a
-slip but not
c
-slip: biotite recrystallization within micro-shears; and variable amphibole recrystallization. The deformation histories display a distinct division between magmatic state and moderate temperature solid-state deformation features with little evidence for intervening high temperature solid-state fabrics. This contrasts with criteria widely considered diagnostic of syn-tectonic plutons which envisage development of a continuum of magmatic through high temperature solid-state deformation fabrics. However, we consider the plutons syn-tectonic and attribute the hiatus to contrasting strain and pluton cooling rates, length and nature of deformation events and host rock ambient temperatures. Intermediate magmas, emplaced at moderate to shallow levels in the crust may be more prone to develop such apparently punctuated deformation histories than SiO
2
,-richer granitoids.
Indications of glaciation at the base of the Proterozoic Stoer Group (Torridonian), NW Scotland
Authors: DAVISON STEPHEN , HAMBREY MICHAEL J.
Published: December 2007

The Stoer Group of NW Scotland has long been regarded as the product of ephemeral flood events. The resulting facies have been interpreted as fanglomerates, braided river deposits and lake sediments. New observations of the Lewisian basement palaeotopography and basal Stoer Group facies at Enard Bay, Clachtoll and Achiltibuie suggest that earliest Torridonian time was characterized by glaciation. Lewisian basement displays
rochr rnoutonnée-like
forms and evidence of subglacial fracturing, possibly by water under high pressure. Breccias associated with rough, craggy basement are interpreted as fractured bedrock formed subglacially on the downglacier sides of the
roches moutonnées.
Diamictites draping the basement are regarded as basal tillite. Stratified diamictites and laminated mudstone-sandstone-breccia-conglomerate units contain outsized clasts, displaying drop-stone structures, and are therefore inferred to be ice-rafted deposits. Associated microbial carbonates are inferred to be analogous to contemporary Antarctic lake deposits. Limited palaeo-iceflow indicators suggest a source of the ice mass to the N or NE.
Late Flandrian coastal change and tidal palaeochannel development at Hills Flats, Severn Estuary (SW Britain)
Authors: ALLEN J. R. L. , FULFORD M. G.
Published: December 2007

An eclectic range of stratigraphical. sedimentological, geochemical, archaeological and historical evidence relating to a tidal palaeochannel exposed at a deep erosional level in the modern intertidal zone on the Avon–Gloucestershire border demonstrates that tidal wetlands reclaimed during the Roman period ranged much further seaward than the modern coastline. Vigorous late medieval-early modern erosion, linked to the cool, disturbed conditions of the Little Ice Age, forced the coastline by the mid-seventeenth century to a location inland of its present line. A possible medieval landing place was destroyed and it was necessary to set back the flood defences. As the result of renewed mudflat-marsh growth, the coast at Hills Flats has built outward during modern times, but in three distinct stages and by no means as far seaward as its likely Roman position.
The Flamborough Tertiary outlier, UK southern North Sea
Authors: STEWART S. A. , BAILEY H. W.
Published: December 2007

A previously unrecorded outlier of Tertiary sediments is described from blocks 42/29 and 47/4b on the northeast corner of the East Midlands Shelf, southern North Sea, UK. Biostratigraphy in well 47/4b-6 indicates the presence of lateral time equivalents of the Horda, Balder-Sele and Lista Formations, the only occurrence of Tertiary sediments on the East Midlands Shelf. The outlier is 50 km from the Humberside coast, 30 km west of the nearest Tertiary sediments. The Tertiary strata subcrop thin Recent deposits over an area of 104 km
2
, and reach a maximum thickness of 700 m. Erosive truncation of these sediments shows that they are remnants of a more extensive Palaeogene cover on the East Midlands Shelf and they constrain the timing of inversion on the Dowsing Fault Zone and growth of the Sole Pit High. The outlier is compartmentalized in terms of structural style into an unfaulted westerly portion which is oval in outline, and an adjoining northwest-southeast trending graben. The contrasting geometries of these compartments reflect salt-controlled synclinal folding and thin-skinned extensional faulting detaching on Triassic salt respectively. Both mechanisms are effects of basinwards sliding of the Sole Pit High Mesozoic section upon Permian salt, triggered by Tertiary inversion on the Dowsing Fault Zone. Unconformities associated with the outlier indicate an initial, intra-Campanian phase of inversion, followed by two later episodes which may correlate with late Maastrichtian and intra-Miocene events recorded further south and east. The Palaeogene sediments within the outlier represent part of the eroded cover of the East Midlands Shelf predicted to have been present by sonic log-based studies of apparent exhumation.
The Lower Palaeozoic of Oman and its context in the evolution of a Gondwanan continental margin
Authors: MILLSON J. A. , MERCADIER C. G. L. , LIVERA S. E. , PETERS J. M.
Published: December 2007

The Lower Palaeozoic Haima Group of the Sultanate of Oman comprises a sequence dominated by siliciclastic rocks up to several kilometres thick and broadly divisible into two groups. The sequence is known in outline from subsurface exploration, but recent field work on outcrops in the isolated Huqf area in east-central Oman has allowed a more detailed environmental interpretation of the succession. At the base coarse continental deposits of the Lower Haima Group rest unconformably on Precambrian–Lower Cambrian Huqf Group sediments (mainly carbonates and evaporites). The overlying Upper Haima Group comprises from base to top the aeolian dominated Amin Formation, the non-marine (coastal plain) to shallow marine (intertidal–subtidal) sediments of the Andam Formation, the non-marine to marginally marine Ghudun Formation, and the complex cyclical deep to shallow water deposits of the Safiq Formation.

Correlation of the Haima Group of Oman with the Lower Palaeozoic of the Arabian Peninsula, North Africa and Iran allows the evolution of the Gondwanan margin to be modelled. A widespread Lower Cambrian sequence of coarse alluvium, resting on peneplained Upper Precambrian–Infracambrian Huqf Group strata, represents the final stage of uplift and basin fill associated with the Late Proterozoic suturing of Arabia and adjacent plates which resulted in the formation of the Gondwanan continent. The overlying thick sequence of continental (fluvial and aeolian) sediments was deposited in a series of stable intracratonic basins across the Gondwanan landmass.

In the Mid- and Late Cambrian an overall sea-level rise led to the repeated development of shallow marine shelf carbonates across the margin. The subsequent replacement of this marginal carbonate sequence with a thick marginal to non-marine, sand dominated sequence may reflect the interplay of several events: the drift of Gondwana towards more southerly latitudes, a phase of strong tectonic rejuvenation during the latest Cambrian–Early Ordovician, and/or a eustatic fall in sea-level. Organic-rich marine mudrocks were deposited over much of the Gondwanan platform during a series of marked eustatic sea-level rises during the Mid–Late Ordovician and Early Silurian. In Oman no evidence has yet been found for the significant Late Ordovician glacial event recorded from North Africa and Saudi Arabia.
The influence of sulphur redox reactions and mixing on the chemistry of shallow groundwaters: the Harrogate mineral waters
Authors: BOTTRELL SIMON H. , RAISWELL ROB , LEOSSON MARKUS A.
Published: December 2007

The Harrogate mineral waters exhibit a wide range of mineralization, with the most concentrated reaching half-seawater salinity and containing abundant sulphide. Comparison of new and historical chemical data shows that the major element composition of the main wells has remained essentially constant for over 200 years. The most saline wells have similar chemistry and a number of species (Na
+
. K
+
, Li
+
, Ca
2
, Mg
2+
, S
2+
) behave conservatively with Cl
−
. The more dilute wells have the same characteristic ratios of these species to Cl
−
and thus originate by simple dilution of the brine component. The non-conservative species (mainly HCO
−
3
, and SO
2−
4
) are those which are affected by sulphur redox reactions. Stable isotopes show the waters to be meteoric in origin; this and the chemical characteristics of the brines (
87
Sr/
86
Sr
2+
,Sr
2+
/C1
−
, Li
+
/Cl
−
) point to a meteoric-derived formational brine as the source of the salinity with dilution by local shallow groundwater.

Sulphur isotope data show the sulphate in the dilute waters could be derived by oxidation of pyrite in Carboniferous mudstones by shallow groundwaters. Total sulphur concentrations in the saline waters are similar to the dilute waters and hence bacterial reduction of sulphate in the local shallow groundwater can account for the sulphide in the wells.
The Sr isotopic evolution of the oceans during the 'Cambrian Explosion'
Authors: NICHOLAS C. J.
Published: December 2007

The Late Precambrian and Cambrian were periods of marked global change in the biosphere with the appearance and rapid radiation of skeletalized metazoans. However, the changes in atmosphere and oceanic environments that may have accompanied this evolutionary episode remain largely unresolved. In this contribution carbonate samples from Lower Cambrian sections in eastern Siberia are used to construct a composite Sr isotope curve across the Nemakit-Daldynian–Tommotian boundary (the former Precambrian–Cambrian boundary in Siberia). The results show a significant fall in seawater
87
Sr/
86
Sr ratios across this interval. This decrease is placed in context by the construction of a new seawater Sr curve for the late Neoproterozoic to early Ordovician, compiled from these data and those available in previous publications. The ocean-atmosphere interactions recorded by the marked variation in seawater Sr immediately preceding and during the Cambrian potentially record short-term (15–20 Ma) hydrothermal events punctuating an overall increase in terrestrial weathering rates, although further research is needed to confirm this conclusion.
Synchronous very low-grade metamorphism, contraction and inversion in the central part of the Welsh Lower Palaeozoic Basin
Authors: ROBERTS B. , MERRIMAN R.J. , HIRONS S.R. , FLETCHER C.J.N. , WILSON D.
Published: December 2007

A metamorphic map (white mica crystallinity) based on 663 data points has been generated for the recently published British Geological Survey 1:50 000 geological sheets 178 (Llanilar) and 179 (Rhayader). Epizone, upper anchizone, lower anchizone and sub-anchizone are delineated. Metamorphic cross-sections are drawn and superimposed on structural cross-sections. Assumptions made in order to draw metamorphic cross-sections are: (1) the anchizone spans 100°C; (2) the metamorphic field gradient was 36°Ckm
−1
; (3) metamorphic surfaces were initially generated parallel to the contemporary ground surface.

Restoration of the sections indicates that at the time of metamorphism a contractional phase had begun because reverse movement on earlier extensional faults, development of back-thrusts, footwall short-cuts and limited growth of precursor folds had taken place. Metamorphism continued locally during later stages of the contractional phase as a strain-related phenomenon. Finally, tensional faulting followed the cessation of folding and metamorphism.
Rise, closure and reactivation of the Bicorb–Quesa evaporite diapir, eastern Prebetics, Spain
Authors: ROCA E. , ANADÓN P. , UTRILLA R. , VÁZQUEZ A.
Published: December 2007

The Bicorb–Quesa diapir belongs to a complex system of evaporite diapirs located in the SE Iberian Peninsula. It was emplaced along the axis of a graben system flanked by two syn-diapir growth basins filled by Miocene sediments. The Miocene evolution of the diapir may be divided into three major phases: an initial extensional phase during which the graben system formed and the diapir rose; a second phase during which regional shortening closed the diapir; and a third phase characterized by normal faulting during which diapirism was reactivated, cutting the previously-formed thrusts and folds. This evolutionary trend demonstrates that diapirism was initiated and promoted by regional extension.

During the two extensional phases, the diapir grew by reactive, active and passive rise. Sedimentation during the reactive stage was characterized by strong basin subsidence, sharp changes in sediment thicknesses, and major coarse-grained sediment input. During the active stage, the coeval basin-fill sequence displays progressive angular unconformities, gravitational deposits and subtle changes in thickness with the sediments unconformably overlying most of the earlier-formed faults. Finally, during the passive stage, the sediments synchronous with diapir formation include abundant components from the extruding rocks, and show gentler changes in thicknesses, a progressive decrease in the input of coarse sediments, and the deposition of mudstones and/or lacustrine carbonates that clearly extend onto the faulted basin margins.
A model to explain the occurrence of platinum- and palladium-rich ophiolite complexes
Authors: PRICHARD H. M. , LORD R. A. , NEARY C. R.
Published: December 2007

During the last ten years significant concentrations of Pt and Pd (more than 1000 ppb Pt + Pd) have been reported from several ophiolite complexes including Shetland, Leka, Al 'Ays, Zambales, Ceruja and Thetford. Similar studies on others, including those in Cyprus and Oman, have failed to reveal equivalent concentrations. Here we compare the characteristics of these ophiolite sequences and propose that Pt- and Pd-rich ophiolites contain thick sulphur-bearing ultramafic crustal units that crystallized from PGE-rich boninitic magmas produced by excess partial melting in a water-rich subduction zone.
Diorite-granite magma mingling and mixing along the axis of the Galway Granite batholith, Ireland
Authors: DESOUKY MOHAMED EL , FEELY MARTIN , MOHR PAUL
Published: December 2007

The late Caledonian Galway Granite batholith is bisected by a WNW-trending magma mingling and mixing zone (the MMZ). This trans-batholithic feature marks the entrainment and ascent of hydrous dioritic magmas in anatectic silicic magmas. Deep in the zone, flowage and hydraulic stress stretched out alternating mafic and hybrid granitoid sheets. At progressively shallower levels, highly elongate and deformed enclaves led up to discrete clouds of ovoid enclaves. Magmatic end-members are identified as quartz diorite and calc-alkaline granite, from which a mixing continuum was produced despite a persistent degree of immiscibility among the various hybrids. A generally west-directed flowage along the MMZ locally induced detachment and upthrusting of ductile blocks of deeper-seated mingled rock. The detailed plan of the MMZ reveals left offsets, supporting field evidence for emplacement in a broad dextral NW-SE shear zone. The Maam and Clifden fault systems provide the partners to model this emplacement within a crustal pull-apart.
Deep-water fault-controlled sedimentation, Arctic Norway and Russia: response to Late Proterozoic rifting and the opening of the Iapetus Ocean
Authors: DRINKWATER N. J. , PICKERING K. T. , SIEDLECKA A.
Published: December 2007

The Late Proterozoic (late Riphean) sections of Varanger Peninsula, northern Norway, and the Rybachi Peninsula, Kola Peninsula. Russia, both show an overall progradational succession from deep-marine to slope environments, with the Varanger sections passing up into shallow-marine and then fluviatile deposits. The oldest exposed parts of both successions are correlated along-strike over a minimum distance of
c.
75 km, and the turbidite systems are interpreted as fragments of the sedimentary infill of the same rift basin, defined here as the Varanger–Rybachi Basin, which fringed the Fennoscandian Shield in Late Proterozoic time. Sediment transport patterns show lateral input and axial deflection to more eastward-flowing currents. Proximal-to-distal and axial-to-lateral changes in the sedimentary facies associations are placed within deep-marine slope and basin-floor turbidite systems. In Arctic Russia. the basin-bounding Rybachi-Sredni Fault Zone probably broke the seafloor to shed breccias along a fault scarp, possibly even as a subaerial fault zone and associated with fan-deltas. In contrast, to the west in northern Norway, the Trollfjord–Komagelv Fault Zone probably acted as a concealed basin-margin fault zone which controlled the location and pattern of deep-water sedimentation, offshore from a major fluvially dominated delta system. The Late Proterozoic development and subsequent infilling of this basin is interpreted as having formed in response to the opening of the Iapetus Ocean. possibly associated with mantle plume activity farther west. The Late Proterozoic Barents Sea Basin may have been analogous to the late Jurassic and Palaeogene northern North Sea, in which sand-prone turbidite systems accumulated predominantly by deep-marine sediment transport
away
from a developing ocean basin (North Atlantic) associated initially with thermally induced lithospheric extension and uplift (late Jurassic), followed by mantle-plume activity centred over Iceland during Paleocene time causing the development of a thermal-sag basin and uplift over the plume.
Late Cretaceous extinction patterns in Antarctica
Authors: CRAME J. A. , LOMAS S. A. , PIRRIE D. , LUTHER A.
Published: December 2007

New correlations of marine clastic sedimentary rocks exposed within the James Ross Basin, Antarctica have shown that the mid-to late Cretaceous succession is in excess of 5 km thick. Plotting the ranges of the principal molluscan macrofossils against the revised stratigaphy indicates that inoceramid bivalves are totally absent, and dimitobelid belemnites extremely rare, throughout an extensive 1400 m thick Maastrichtian succession. These early extinction patterns are interpreted to be due to both a regional shallowing event and a pronounced phase of high-latitude, Campanian–Maastrichtian cooling. Cool polar bottom waters may have been forming by as early as mid- to late Campanian times.
The southern margin of the Rockall Plateau: stratigraphy, Tertiary volcanism and plate tectonic evolution
Authors: BULL JONATHAN M. , MASSON DOUGLAS G.
Published: December 2007

The geological evolution of the southwest Rockall Plateau in the area of Edoras Bank has been clarified using seismic reflection, gravity and magnetic data. Four principal reflectors are observed within the Tertiary sedimentary sequence: I, Late Miocene; II, latest Early Miocene; III, Late Eocene; IV, earliest Eocene. A period of pronounced sediment drift accumulation marks the interval I–II. Reflector III, the top of a sediment wedge prograding southward from Edoras Bank, marks a change from terrigenous to pelagic sedimentation that is probably related to subsidence of the Rockall Plateau following the separation of Greenland from Eurasia in the earliest Eocene. Reflector IV marks the top of a wedge-shaped seismically transparent layer that also thins southward away from Edoras Bank. On the basis of its seismic attributes and magnetic signature, this layer is interpreted as a volcanic sheet, formed as part of the North Atlantic Tertiary Volcanic Province during rifting of Greenland from Eurasia. The recognition of voluminous volcanic rocks south of Edoras Bank extends the known area of the Tertiary volcanic province several hundred kilometres to the south. Gravity anomaly modelling and continental reconstructions suggest that the region south of Edoras Bank is underlain by thinned continental crust. A four stage geological evolution for this region is indicated, (i) Initial rifting associated with the separation of Labrador from Greenland in the late Cretaceous is characterized by enhanced crustal thinning and subsidence in the region of a rift triple junction. (ii) Passive subsidence and accumulation of late Cretaceous and earliest Tertiary sediments followed the initiation of seafloor spreading in the Labrador Sea. (iii) Blanketing of the area by Palaeocene volcanic rocks masked pre-existing magnetic lineations, providing an explanation for some of the problems in earlier interpretations based mainly on magnetic data. (iv) Post-volcanic sedimentation, continuing to the present day.
The role of the calcium carbonate-calcium phosphate switch in the mineralization of soft-bodied fossils
Authors: BRIGGS DEREK E. G. , WILBY PHILIP R.
Published: December 2007

Authigenic minerals play an important role in the preservation of most soft-bodied fossils. The greatest detail is preserved in apatite (calcium phosphate) but its precipitation is usually inhibited by the high concentrations of HCO
3
-
in aqueous settings. Nonetheless, investigations of soft-bodied biotas have revealed very early authigenic calcite crystal bundles in close association with phosphatized soft-tissues. This demonstrates that the geochemical controls on soft-tissue mineralization are dynamic and act on a very local scale. Direct comparisons with experimental results permit the conditions of fossilization to be inferred.
Geochemistry and petrogenesis of volcanic clasts in the Permian breccias around Exeter
Authors: AWAD N. T. , MEREFIELD J. R. , SCRIVENER R.C. , STONE M.
Published: December 2007

Geochemical comparisons between volcanic clasts from the late Permian red beds and various granite plutons and granite porphyries ('elvans') from SW England show that the clasts have closest affinity with the poorly megacrystic granite of Dartmoor and the 'elvan-like' Godolphin granite. This affinity with the Dartmoor granite backs up recently published ɛ
Nd
data and age determinations. It is concluded that the clasts represent volcanic material derived from an evolving subsurface granitic magma, thereby conforming with conclusions/ideas of earlier workers for the former presence of a Dartmoor volcano.
A re-evaluation of the stratigraphy and evolution of the Kohistan arc sequence, Pakistan Himalaya: implications for magmatic and tectonic arc-building processes
Authors: TRELOAR PETER J. , PETTERSON MICHAEL G. , JAN M. QASIM , SULLIVAN M. A.
Published: December 2007

New field mapping and structural data, combined with published geochemical data, from the Kohistan arc in the NW Himalaya, enable a re-evaluation of the arc stratigraphy. Key lithological units and their relationships are more clearly defined, permitting the construction of a revised magmatic-tectonic history for the arc. The oldest units are transitional oceanic-type basalts, which form the basement to the subduction related sequence. Arc-type gabbroic sheets and plutons intrude the oceanic basalts: together these form the Kamila Amphibolite Belt. Metasediments and basaltic lavas were deposited, within an extensional basin, onto the Kamila Amphibolite Belt basement. This sequence, exposed across the arc, forms a distinct stratigraphic unit which is formally defined here as the Jaglot Group. Sediment-charged turbidity currents transported material into the basin, whilst submarine eruptions contributed the basaltic component. This period of extension culminated in the eruption of high-Mg boninites of the Chalt Volcanic Group which overlie the rocks of the Jaglot Group. The earliest granitoids of the Kohistan Batholith predate suturing and intrude the Jaglot and Chalt sequences. At
c.
100 Ma Kohistan sutured to Asia. suturing being accompanied by thickening of the arc with the development of major intra-arc shear zones and a penetrative, regionally developed steep cleavage. At
c.
85 Ma intra-arc rifting permitted the emplacement into the arc of the voluminous gabbronorites of the Chilas Complex which clearly intrudes the Kamila Amphibolite Belt to the south and the Jaglot Group to the north. The Chilas Complex has been regarded as part of the pre-suturing, juvenile arc sequence. Field evidence summarized here show this to be not so. Heat advection associated with emplacement of the Complex caused amphibolite facies regional metamorphism, melting of the lower arc and plutonism. Some of the resultant granitoid plutons were unroofed and eroded during a compressional phase at between 80 and 55 Ma, before emplacement of further plutons and extrusion of basaltic through to rhyolitic volcanic rocks at between 55 and 40 Ma. At least three phases of extension and rifting, each separated by short lived phases of compression, charac­terized arc evolution. Much of the magmatism is controlled by extensional tectonics within the overriding plate of the kind commonly associated with a retreating subduction zone.