bluuebunny/crossref_metadata_2025 huggingface dataset:
Composition and provenance of the Silurian to Devonian sandstone sequences of the southern Midland Valley
Authors: Phillips E. R. , Barron H. F. , Smith R. A. , Arkley S.
Published: January 2010

Synopsis

A provenance study of rocks from the Silurian inliers and Siluro-Devonian Lanark Group sandstones of the southern Midland Valley has shown that they are petrographically and compositionally similar, and were derived from the same source terrane. The clast content of these rocks indicates that before widespread Lower Devonian calc-alkaline volcanism, this source terrane included volcanic and hypabyssal igneous rocks that appear to have been associated with a wacke sandstone-dominated sedimentary sequence and a granitic igneous suite. The possibility that the source rocks for these sequences are within the Midland Valley Terrane, but now not exposed, is discussed. Minor differences in sandstone composition between the Carmichael, Eastfield and North Esk inliers are interpreted as reflecting either slight differences in the source or deposition within individual sub-basins. Comparable regional variations within the Swanshaw Sandstone Formation suggest that sub-basin architecture continued to influence sediment dispersal patterns during the deposition of the basal Lanark Group. The onset of Lower Devonian calc-alkaline volcanism coincided with a major change in sandstone composition within the Lanark Group and accompanied the replacement of the relatively small Silurian sub-basins by a single larger basin.
Rare earth element and Sr–Nd isotope geochemistry of primary apatite crystals in metabentonites from Dob’s Linn, southern Scotland
Authors: Batchelor Richard A. , Evans Jane
Published: January 2010

Synopsis

New Sr and Nd isotope and rare earth element data obtained from primary apatite microphenocysts indicate that the Dob’s Linn metabentonites originated from a mildly depleted mantle source, probably generated in a continental margin or back-arc basin environment. There is a small but notable reduction in crustal contamination of the source magmas through two graptolite zones (
convolutus
to
sedwickii
) indicated by a shift to higher
ɛ
Nd values. This shift is consistent with a magma chamber being periodically refilled with mantle-derived melts.
The source of granites: inferences from the Lewisian complex
Authors: Castro Antonio
Published: January 2010

Synopsis

The origin of granitic rocks has been the subject of intense debate. It is broadly accepted that granites are generated in the continental crust. However, the composition of the source rocks and the processes controlling melting reactions remain controversial. Fluid-absent melting is a plausible mechanism for granite generation but is not supported by experimental data. Fluid-present melting is favoured by experiments but the presence of a free water phase is very unlikely in the deep crust. Isotopic ratios are also paradoxical because Nd isotopes indicate a crustal (recycled) source but the low
87
Sr/
86
Sr ratios displayed by many granite batholiths require a substantial mantle contribution. Furthermore, mantle–crust hybridization mechanisms are difficult to apply in terms of magma mixing and assimilation according to models of the physical/rheological behaviour of silicic magmas. Here I present a new, source-based, genetic approach for granitic rocks in which all these paradoxes are satisfactorily explained. The model is supported by new constraints from laboratory experiments and observations of field relationships in the Lewisian complex of northern Scotland. The process starts with the invasion of crustal regions by water and K-rich monzodiorite (andesite) magmas derived from hybridized regions of the subduction-modified mantle wedge. These intermediate magmas supply the water and potassium necessary for crustal melting and granite batholith generation.
Correlation of the Early Devonian Rhynie chert beds between three boreholes at Rhynie, Aberdeenshire
Authors: Trewin Nigel H. , Wilson Elizabeth
Published: January 2010

Synopsis

Three sequences of the Early Devonian Rhynie Cherts Unit intersected by cored boreholes at the Rhynie SSSI (Site of Special Scientific Interest) are compared on the basis of both lithology and plant content. It is shown that over the 45–65 m distance covered by the boreholes general correlation can be made of the chert-bearing unit, and also sandstone and shale units. General thicknesses of units are similar in the three boreholes. However, there is no bed-to-bed correlation of the cherts or other lithologies, neither is there a correlation in the sequences of plants recorded. It is considered that the sequence was deposited in the distal regions of sinter deposition on a low-angle outwash apron from a hot spring, where the water table was close to the surface, and water was frequently ponded. Overbank flooding from a northward-flowing river system periodically inundated the outwash apron, depositing sand and mud and interrupting sinter deposition. On the basis of plant occurrence in the chert beds intersected in the boreholes it is estimated that on average 15% of the area was bare ground, 30% covered with plant litter, and 55% with growing plants. Similar environments are seen today on the distal marshy areas of outwash aprons from hot springs in Yellowstone National Park, USA.
A revision of the hexactinellid sponge
Amphispongia oblonga
Salter 1861: not a dasycladacean alga
Authors: Botting Joseph P.
Published: January 2010

Synopsis

A re-examination of the original material, combined with new specimens, has allowed a comprehensive revision of the structure and affinities of the problematic sponge
Amphispongia oblonga
Salter 1861. Details of the hexactine-based spiculation, wall structure, homogeneously expanding growth pattern, and apertural marginalia allow a clear interpretation as a hexactinellid sponge, albeit with several unusual features. It is best regarded as a member of a distinct family within the order Reticulosa, superfamily uncertain.
A re-examination of a Middle Jurassic sauropod limb bone from the Bathonian of the Isle of Skye
Authors: Liston J. J.
Published: January 2010

Synopsis

A limb bone from the Bathonian of the Isle of Skye, previously identified as a possible femur of the sauropod dinosaur
Cetiosaurus,
is reassessed in light of comparisons with other sauropod material, including the lectotype of
Cetiosaurus oxoniensis.
Although the closest match for the Skye bone is found to be a left humerus identified as
Cetiosaurus oxoniensis
by J. Phillips in 1871, the identification of the Skye bone as cetiosaurid is unsafe, given the poor diagnostic power of long bones in most sauropod taxa.
Sedimentology and stratigraphic affinities of Neoproterozoic coarse clastic successions, Glenshirra Group, Inverness-shire, Scotland
Authors: Banks C. J. , Winchester J. A.
Published: January 2010

Synopsis

Records of ancient environments and past basin histories can be preserved in metasedimentary successions, despite their subsequent deformation and metamorphism. In the Central Scottish Highlands SE of Loch Ness, the Garva Bridge Psammite and the Glen Buck Pebbly Psammite Formations (hitherto included within the Glenshirra Subgroup at the base of the Neoproterozoic Grampian Group) represent a continuum of alluvial fan to shallow water sediments, deposited in a SE thinning fan-delta clastic wedge. These sediments, derived from an uplifted granitoid hinterland to the west, contrast with the overlying marine sedimentary rocks of the Corrieyairack Subgroup, which were deposited by sediment gravity flows within a submarine slope setting. The Glen Buck Pebbly Psammite/Garva Bridge Psammite Formations and the Corrieyairack Subgroup represent two genetic stratigraphic sequences divided by a sharp sequence boundary that records a major reorganization in basin architecture. Hence, we propose that the Garva Bridge Psammite and Glen Buck Pebbly Psammite Formations be included within a separate Glenshirra
Group,
genetically unrelated to either the marine deposits of the immediately overlying Grampian Group or the earlier, locally migmatized (Moinian?) basement to the Central Highlands. The Glenshirra Group thus represents the earliest phase of post-Knoydartian extension, predating the main Dalradian basin development.
Groundwater challenges of the Water Framework Directive in Scotland (0–60 in 12 months)
Authors: Clews Jean , Fitzsimons Vincent , Simpson Elaine
Published: January 2010

Synopsis

Groundwater in Scotland has traditionally been undervalued as a resource as it provides only limited public water supply despite being important for many private, industrial and agricultural water supplies and for dependent aquatic and terrestrial ecosystems. The Water Framework Directive (2000/60/EC) (WFD) requires a characterization report to be submitted t o the European Commission in March 2005 describing the characteristics of our groundwater, an analysis of human impact and an assessment of the risk of failing to meet the environmental objectives set out in the directive. This has provided a driver to both rapidly improve the information available and to develop tools to assess the impact of human activity on this resource. Risk assessment methodologies have been developed to be consistent and reproducible and are based on simple science and national datasets. They use the concepts of pressure, pathway susceptibility and receptor sensitivity. Where a body is identified as being ‘at risk’, further characterization work will be required, followed by targeted monitoring. Methodologies, data availability and risk assessments will be refined as the work progresses. It is likely that some bodies identified as being at risk of failing to meet the WFD environmental objectives in the initial screening exercise will be classified as good status as more reliable information becomes available.
Agriculture and diffuse pollution: groundwater nitrate vulnerable zones in Scotland
Authors: Ball D. F. , MacDonald A. M. , Lilly A.
Published: January 2010

Synopsis

Nitrate derived from agricultural activity is a threat to Scotland’s surface water and groundwater environment. The pollution of groundwater by nitrate can impact drinking water in aquifers in addition to the quality of base-flow to many streams and rivers. European legislation (in the form of the Nitrates Directive) requires that waters with a nitrate concentration of greater than 50 mg-NO
3
l
−1
(and those at risk of exceeding this concentration) should be identified and the catchment areas designated as Nitrate Vulnerable Zones (NVZs). Groundwater NVZs for Scotland were developed using a risk-based methodology which combined several Scottish national scale datasets in a GIS. The risk of nitrate leaching was determined from soil, climate and land use data. Digital solid and superficial geology data (at 1:50 000 scale) were interpreted to give an indication of aquifer vulnerability. The final zones were then determined by identifying local surface water catchments associated with areas of greatest nitrate leaching and aquifer vulnerability. The results of the vulnerability/risk analysis were broadly consistent with the available nitrate data for much of Scotland. Groundwater nitrate data were collated from the monitoring network of the Scottish Environment Protection Agency (SEPA), water authority boreholes and private water supplies, with additional new data collected from targeted sites. Within the NVZs, 25% of approximately 1700 samples exceeded 50 mg-NO
3
l
−1
compared to the rest of Scotland, where less than 5% of approximately 700 samples exceeded this concentration. The nitrate vulnerable zones have now been designated by the Scottish Executive and action programmes established to reduce nitrate contamination in these areas.
The Lewisian terrane model: a review
Authors: Park R. G.
Published: January 2010

Synopsis

The Lewisian terrane model of Friend and Kinny divides the Lewisian complex into nine separate terranes believed to have amalgamated during the Palaeoproterozoic. This paper analyses the rationale for the terrane model and suggests criteria to evaluate and refine it. Similarities and differences in Palaeoproterozoic structural, metamorphic and igneous features are used to divide the complex into 14 separate blocks of three types: type A (upper-plate) characterized by retrogressed high-pressure granulite-facies Archaean metamorphic rocks and localized Laxfordian deformation; type B (lower plate) characterized by amphibolite-facies Archaean metamorphic rocks originating at higher crustal levels, intense Laxfordian deformation, and swarms of Laxfordian granites and pegmatites; and third, Palaeoproterozoic complexes comprising oceanic and volcanic arc elements.

The boundaries between the type A and type B blocks, where seen, are major shear zones believed to represent a deformed and disrupted collisional suture between two large continental plates, the central Greenland craton (CGC) to the NE and the North Atlantic craton (NAC) to the SW. The following sequence of events is proposed. The Palaeoproterozoic complexes were accreted to the upper plate (NAC) at
c.
1.9 Ga. This was followed by collision with the CGC at
c.
1.87 Ga, causing the intense early Laxfordian deformation and high-grade metamorphism. At
c.
1.74 Ga a second collision took place with the 1.80 Ga ‘Malin’ volcanic arc to the south, resulting in reactivation and late Laxfordian deformation, producing NW-trending folds, dextral shear zones, granite sheets and pegmatites. These late Laxfordian movements are considered to have resulted in considerable disruption of the early Laxfordian terranes. They include substantial strike-slip movements that may have led to the creation of further displaced terranes, some of which may prove to be exotic.
Paleocene fossil wood from beneath An Sgurr, Isle of Eigg
Authors: Woolnough Lewis , Overnell Julian
Published: January 2010

Synopsis

A fragment of fossilized wood was found near the top of the conglomerate bed beneath An Sgurr, Isle of Eigg. The wood, which is described here, appears to belong to no recorded genus, fossil or modern. It has affinities with several families of flowering plants (angiosperms), notably the Rosaceae. The name
Polyactinoxylon subansgurrensis,
gen. et sp. nov. is proposed. It appears that this species was part of a mixed culture of woody plants, growing in a possibly temperate climate, during the early Paleocene.
Geochronology of a granitoid boulder from the Corsewall Formation (Southern Uplands): implications for the evolution of southern Scotland
Authors: Bluck B. J. , Dempster T. J. , Aftalion M. , Haughton P. D. W. , Rogers G.
Published: January 2010

Synopsis

A U–Pb monazite age of 474 ± 2 Ma has been determined for a weakly foliated granite boulder > 1 m in diameter from the Corsewall conglomerate, SW Scotland. The clast contains xenoliths and partly assimilated xenoliths of regionally metamorphosed rock from which the monazites have been derived. The age constrains the original emplacement of the pluton to between 474 ± 2 and
c.
458 Ma, the age of the deposit in which the boulder is found. This age confirms an earlier Rb–Sr muscovite Ordovician age for boulders of this type and contradicts a pre-existing age of 1265 Ma used to suggest a source in Newfoundland and a post-Caradoc major lateral displacement of the Southern Uplands. The monazite age reaffirms that a basement-arc complex once existed north of the Southern Uplands and was the principal contributor of sediment to Ordovician–Silurian basins of southern Scotland. A source for the metamorphic detritus in the Dalradian block is unlikely, as the boulders would have been transported for > 150 km through zones of actively accreting terranes and marginal basins. The possibility of Archaean crust within this basement complex is further suggested by the Sm–Nd systematics of the granite boulders at Corsewall Point.
Xenolithic insights into the deep geology beneath the Ross of Mull
Authors: Faithfull J. W. , Upton B. G. J.
Published: January 2010

Synopsis

A rich assemblage of xenoliths is present in three small Permian dykes that cut the Ross of Mull granite on the SW coast of Mull, bordering the Sound of Iona. The xenoliths, up to 80 mm in diameter, are abundant, and include a wide range of compositions, including spinel lherzolites, dunites, pyroxenites, meta-basic granulite-facies gneisses, anorthosites, anorthoclasites, quartzo-feldspathic gneisses and psammitic meta-sediments. Granitic xenoliths attributable to the Ross of Mull pluton are strikingly scarce. The inference is that the majority of the xenoliths were entrained from beneath the pluton. The xenoliths represent a wide cross-section of the lithosphere, from below the Moho to relatively high crustal levels. Cataclasis and intense shearing in some of the crustal xenoliths suggests that the dykes intersected one or more of the bounding Caledonian thrusts at mid-crustal depths.
The Green Beds of the SW Highlands: deposition and origin of a basic igneous-rich sedimentary sequence in the Dalradian Supergroup of Scotland
Authors: Pickett E. A. , Hyslop E. K. , Petterson M. G.
Published: January 2010

Synopsis

The Green Beds are distinctive chlorite- and epidote-rich metasedimentary rocks, which collectively represent a series of important lithostratigraphical marker units in the Southern Highland Group of the dominantly late Precambrian Dalradian Supergroup of Scotland. In a recent re-evaluation of the nature and origin of the Green Beds, integrated mapping, sedimentological, petrological and geochemical studies have been carried out. The Green Beds form relatively thin but laterally extensive units within thick sequences of siliciclastic metasedimentary rocks, and were deposited from high-density turbidity currents and debris flows in a deep-sea slope apron or ramp setting. They comprise a physical mixture of basic and siliciclastic material, representing periodic influxes of basic igneous detritus into the ‘background’ siliciclastic sedimentary system. The mineralogy of the Green Beds is largely the result of metamorphism, although rare relict detrital minerals from both granitic and basic sources are preserved. Geochemical studies show that the Green Beds and other Southern Highland Group metasedimentary rocks have a similar trace element signature, indicating a common siliciclastic source area. Two suites of Dalradian lavas, the Tayvallich and Loch Avich pillowlavas, were also analysed. Although it is unlikely that these particular volcanic units were the source of the Green Bed basic material, it is believed that the mafic component of the Green Beds was derived from episodes of near-contemporaneous volcanic activity.
The interpretation and application of regional geochemistry: lessons from the Paratectonic Caledonides
Authors: Stone P. , Breward N. , Merriman R. J. , Barnes R. P.
Published: January 2010

Synopsis

The Southern Uplands (southern Scotland) and Lake District (northern England) terranes contain thick and extensive sequences of macroscopically homogeneous, Lower Palaeozoic wacke-type sandstone. There is a close spatial relationship between the outcrop of biostratigraphically defined rock units and distinctive patterns of element distribution in stream sediments derived from those units, with the stream sediment patterns indicating cryptic compositional variations that are not otherwise apparent. Analysis of the stream sediment composition relative to whole-rock values shows that it is not a direct surrogate for the underlying bedrock. Instead, elevation and depletion trends for any given element are controlled by the nature of its mineral host(s) and provide a previously unappreciated means of assessing the detrital mineralogy, and hence provenance of the bedrock sandstones. Stream sediment composition also provides a valuable alternative means of evaluating possible correlation between different stratigraphical sandstone units. Further, since the fine-grained matrix to the wacke sandstones makes a major contribution to the stream sediment, an assessment of the latter allows variations in matrix composition to be taken into account. Examples are given from the Silurian turbidite sequences of the central and southern Southern Uplands (Gala, Hawick and Riccarton groups; the affinity of the Ross Formation with the Hawick Group is demonstrated) and the southern Lake District (Windermere Supergroup).
Pristine fjord landsystem revealed on the sea bed in the Summer Isles region, NW Scotland
Authors: Stoker Martyn , Bradwell Tom , Wilson Christian , Harper Chris , Smith Dave , Brett Colin
Published: January 2010

Synopsis

We present new multibeam bathymetry and boomer seismic profiles from 200 km
2
of sea floor around the Summer Isles in NW Scotland. The data reveal an undisturbed marine landscape comprising overdeepened basins, grooves, moraines, pockmarks and slide scars. Collectively these features represent a Late Devensian fjord landsystem. In more detail, the basins and grooves represent focused subglacial erosion during successive ice-sheet cycles. A suite of moraines charts the retreat of a marine-terminating ice sheet at the end of the last glaciation (
c.
15–18 000
bp
). Pockmarks attest to the release of shallow gas from organic-rich proglacial sediments. Finally, slumps and slide scars demonstrate slope evolution following the retreat of the fjord glaciers. This slope instability, both onshore and offshore, continues to the present day. Ongoing work aims to unravel the detailed sequence of events in the Summer Isles region at the end of the last glaciation, with particular emphasis on the glaciology of The Minch palaeo-ice stream.
Lough Neagh: the site of a Cenozoic pull-apart basin
Authors: Quinn Martyn F.
Published: January 2010

Synopsis

The Lough Neagh Basin in Northern Ireland is the site of a Cenozoic depocentre defined by gravity measurements and a thick succession of Paleocene basaltic lavas and Upper Oligocene clays. Much of the Cenozoic outcrop is concealed by Lough Neagh, but the rhombic outline of the lough provides some indication of the underlying structural control of the depocentre. Several authors have inferred that a Cenozoic pull-apart basin lies within the Lough Neagh area and suggest it is one of a number of transtensional basins, including the Bovey and Petrockstow basins in SW England, associated with NW to NNW-trending strike-slip fault zones. Solid geology maps and gravity data show that the structure of the Lough Neagh Basin is dominated by a segmented, orthogonal pattern of offset NNW and NE-trending faults. It is proposed that pull-apart basin formation took place in the Mid-Paleocene by dextral movement on these offset faults. The potential link between strike-slip tectonics and Cenozoic volcanism in the north of Ireland is briefly considered.
Exceptional preservation of sedimentary structures in metamorphic rocks: an example from the upper Grampian Group, Creag Stalcair, Perthshire
Authors: Banks Christopher J.
Published: January 2010

Synopsis

Despite polyphase deformation and metamorphism, metasedimentary successions can provide records of ancient depositional systems and sedimentary basins. In low strain sections, primary sedimentary fabrics may be preserved, permitting sedimentological and facies studies. At Creag Stalcair, an inverted succession of low-amphibolite-facies psammites belonging to the Grampian Group (Gaick Psammite Formation) display numerous sedimentary structures reflecting deposition in a sandy, tidally influenced environment. These exposures provide a unique insight into the palaeo-environments of the Gaick Psammite that is generally devoid of primary sedimentary fabrics elsewhere.
Maskelyne’s 1774 Schiehallion experiment revisited
Authors: Smallwood John R.
Published: January 2010

Synopsis

Nevil Maskelyne’s 1774 experiment on the Scottish mountain Schiehallion set out to derive the mean density of the Earth, from astronomical observations of the deflection of the vertical and calculation of the mountain’s relative gravitational attraction. Using Maskelyne’s results and lithological survey results, John Playfair estimated mean Earth specific gravity to be 4.56–4.87, while Charles Hutton argued in 1821 that the Earth was ‘very near five times the density of water; but not higher’. Hutton challenged future workers to identify any areas in which his analysis could be improved. The geometry of the 1774 experiment has therefore been recomputed within a digital elevation model extending 120 km from the mountain. Three contributions to the deflection of the vertical have been included: topography, and local and regional subsurface density variations. Local subsurface densities have been modelled using geological maps, cross-sections and laboratory measurements. Regional subsurface effects have been included from analysis of the Bouguer gravity anomaly. The outcome of the new modelling is to credit Maskelyne for his accurate astronomical observations, as together with the new density structure model, they yield a mean Earth density of 5480 ± 250 kgm
−3
, in agreement with the modern value of 5515 kg m
−3
.
Petalocrinus
(Echinodermata, Crinoidea) from the Llandovery (Lower Silurian; Rhudannian) of the Girvan district, SW Scotland
Authors: Fearnhead Fiona E. , Harper David A. T.
Published: January 2010

Synopsis

The discovery of distinctive arms of the cladid crinoid
Petalocrinus
sp. cf.
P. visbycensis
Bather at Rough Neuk Quarry, near Girvan, Ayrshire, extends the geographical range of this genus and also represents the earliest
Petalocrinus
in the British Isles; indeed, they are among the earliest specimens of this genus known. The only previous record of this genus from the British Isles was from the Woolhope Inlier, of Herefordshire, in the
Petalocrinus
Limestone (Telychian). The oldest articulated crinoids from the Silurian of Scotland are from the Mulloch Hill Sandstone Formation (upper Rhuddanian) of Rough Neuk Quarry. New
Petalocrinus
and other discoveries from this formation provide fresh insight into the Scottish Llandovery crinoids. Poor preservation affects the fossil record of Llandovery crinoids, influencing our views of fauna distribution and diversity.
Silica-undersaturated trachytic rocks of central Scotland
Authors: Upton B. G. J. , Stephenson D. , Ellam R. M.
Published: January 2010

Synopsis

The paper presents a review of silica-undersaturated salic intrusions (nepheline-normative trachytes and phonolites) from the Carboniferous–Permian magmatic province in central Scotland. New whole-rock major and trace element analyses, together with Sr and Nd isotopic data, are presented for six intrusions (Bass Rock, North Berwick Law, Traprain Law, Hairy Craig, Fintry and Loudoun Hill) and two syenite autoliths within the Loudoun Hill intrusion.

On the basis of the conventional total alkalis versus silica diagram, all six intrusions are trachytes except for Traprain Law, which is a phonolite. Traprain Law is the most highly evolved and the most undersaturated in silica. The Loudoun autoliths are the most basic (Mg numbers of 21.8–27.3) and are inferred to be fragments of cumulates entrained at shallow crustal depths. Whilst all eight samples have approximately constant initial ɛNd (+4.3–+1.99), initial
87
Sr/
86
Sr data are more variable (0.725929–0.709817). Although four of the samples have isotopic characteristics on, or close to, the Sr–Nd mantle array, those from Fintry, Bass Rock, Loudoun Hill and North Berwick Law lie at higher
87
Sr/
86
Sr
i
values, probably as a result of secondary alteration. From their petrographic and geochemical affinity, the six intrusions are considered to have had similar petrogenesis as late-stage residues from mildly silica-deficient basalt magmas, produced in deep crustal chambers and subsequently intruded with minimal crustal interaction.
Contact metamorphism and partial melting of Dalradian pelites and semipelites in the southern sector of the Etive aureole
Authors: Droop Giles T. R. , Moazzen Mohssen
Published: January 2010

Synopsis

Contact-metamorphic mineral assemblages are described from Dalradian non-graphitic pelites and semipelites in the southern sector of the Etive thermal aureole, adjacent to the Quarry Diorite ring intrusion. Six metamorphic zones were mapped on the basis of incoming index minerals: I, Biotite; II, Cordierite; III, Andalusite+K-feldspar; IV, Corundum; V, Spinel; VI, Sillimanite. Garnet and orthopyroxene occur locally in high-grade quartz-bearing assemblages. Rocks of the Biotite and Cordierite zones retain their regional-metamorphic textures to a large extent, particularly S
2
crenulation cleavage. Above the Andalusite+K-feldspar isograd the rocks are hornfelses, but relict features of S
2
persist. Rocks of the upper Spinel and Sillimanite zones are agmatic/stromatic migmatites which preserve evidence of local partial melting in the form of S
2
-parallel leucosomes and thin fracture-filling vein leucosomes. All leucosomes are K-feldspar-rich. Vein leucosomes consist mainly of leucogranite with a metaluminous composition and, in the Sillimanite Zone, locally contain crystals of peritectic orthopyroxene and/or cordierite.

The compositions of coexisting minerals, determined by EPMA, were used to constrain metamorphic reactions and, with equilibrium thermodynamic calculations, to refine estimates of the P-T conditions of metamorphism. Isograd reactions can generally be modelled satisfactorily in the CNKFMASH system as an isobaric sequence at P=2.2 kbar. An exception is the spinel isograd which occurs at anomalously low T due to the partitioning of Zn into spinel. Estimated isograd temperatures for the And+Kfs, Crn, Spl, melt and Sil isograds are 610°C, 630°C, 660°C, 680°C and 705°C, respectively. Calculated dehydration equilibria yield low values of water activity in the Sillimanite Zone, confirming that partial melting in the innermost aureole occurred under fluid-absent conditions. Leucosome textures and structures suggest that the siliceous microlithons of the former S
2
differentiated crenulation cleavage were the likely sites of melting and provided channels for the movement of melt into brittle fractures to form the vein leucosomes.
The Glenelg-Attadale Inlier, NW Scotland, with emphasis on the Precambrian high-pressure metamorphic history and subsequent retrogression: an introduction and review
Authors: Storey Craig
Published: January 2010

Synopsis

The Glenelg-Attadale Inlier of the NW Highlands of Scotland represents the largest area of exposed basement within the Moine Supergroup and, thus, affords the best opportunity of studying the pre-Moine history and the relationship of the basement to the Moine. The Inlier can be divided into Western and Eastern Units, based on lithological associations, and the boundary is marked by a major ductile shear zone with a dominantly reverse (top-to-the-west) sense of shear. The presence of eclogites and of other eclogite facies rocks within the inlier is the only unequivocal examples of crustal eclogites exposed within the British Isles. Eclogites in the Eastern Unit (P–T
c.
20 kbar and 750–780°C) has been radiometrically dated (Sm–Nd garnet–omphacite–whole rock) to
c.
1082 Ma and their retrogression to amphibolite facies (P–T conditions: minimum 14–16 kbar and
c.
650°C) have been dated (U–Pb zircon) to
c.
995 Ma. This demonstrates that the Eastern Unit underwent tectonic thickening to
c.
70 km during the Grenvillian orogeny and was decompressed into the mid-crust by the end of the Grenvillian orogenic cycle. Rare eclogites in the Western Unit appear to have been formed earlier in the Palaeoproterozoic (
c
. 1700–1750 Ma) and their juxtaposition against the Eastern Unit eclogites may be fortuitous or may reflect a fundamental tectonic manifestation of Wilson Cycle tectonics in orogenic belts. The basal Moine shows a deformed unconformable relationship against the Western Unit. However, the Eastern Unit is entirely enveloped by profound shear zones against the Western Unit and the Moine Supergroup, suggesting that the Eastern Unit is allochthonous. Direct dating of mylonites within the shear zone between the Western and Eastern Units, containing coaxially sheared Moine metasediments, suggests an age of
c.
670 Ma and this may reflect the time at which the units were juxtaposed and the Moine infolded. Final deformation and metamorphism of the Glenelg-Attadale Inlier and the Moine occurred during the Caledonian orogeny, with major folding and extensional shearing operating sometime after
c.
437 Ma, resulting in distinctive fold interference patterns. Terminal thrusting of the Moine and GAI westward over the Laurentian Caledonian foreland occurred at
c.
435–430 Ma.
Conodonts from the Margie Limestone in the Highland Border Complex, River North Esk
Authors: Ethington R. L.
Published: January 2010

Synopsis

Conodonts in a sample collected from the Margie Limestone in an abandoned quarry along the bank of the River North Esk near Edzell include elements of the apparatuses of
Paracordylodus gracilis
Lindström and of a species tentatively reported herein as
Prioniodus
sp. These conodonts are widely distributed globally in Arenigian strata (late Tremadocian and Floian Stages) that were deposited under cold-water conditions. Their presence is not consistent with the earlier report of Caradocian chitinozoans from the Margie Limestone, but they support previous physical comparisons with the Dounans Limestone in the Aberfoyle area.
Discovery of the arthrodire genus
Actinolepis
(class Placodermi) in the Middle Devonian of Scotland
Authors: Newman Michael J. , Trewin Nigel H.
Published: January 2010

Synopsis

A single specimen of the placoderm
Actinolepis
found in the Middle Devonian (Eifelian) Achanarras fish bed of Achanarras Quarry, Caithness, is the first record of the genus in the Devonian of Scotland. The articulated specimen displays an external view of the dorsal armour. Two species of
Actinolepis
are known from the Middle Devonian of the Baltic:
Actinolepis tuberculata
and
Actinolepis magna.
This find strengthens the faunal connection between the Baltic area and northern Scotland in Eifelian and Givetian times, which is supported by other species common to both areas, such as the arthrodire
Millerosteus minor.
Both areas were connected, perhaps at different times, to the same marine area. The most likely connection is to the Rheic Ocean to the south, but another possible connection lies between Laurentia and Baltica to an ocean to the north. Migration of fish into the Old Red Sandstone continent was controlled by long-term climatic cycles. When lake basins overflowed at times of high runoff, fish could migrate to internal continental basins through river systems. During dryer and hotter periods lake basins became isolated and fish evolved in non-marine waters, isolated from marine conditions, possibly explaining the minor differences in fish species from widely separated basins.
New information on the enigmatic Devonian vertebrate
Palaeospondylus gunni
Authors: Newman Michael J. , Den Blaauwen Jan L.
Published: January 2010

Synopsis

The enigmatic vertebrate
Palaeospondylus gunni,
from the Middle Devonian of Scotland, has been described as a larval lungfish (dipnoan), most probably of the genus
Dipterus.
Metamorphosis was said to account for the extreme morphological differences between the two taxa, with distinct size differences between them. However, this is contradicted by a newly discovered specimen of
Dipterus,
the smallest known. This specimen falls within the size range of the largest
P. gunni
specimens, and possesses well-developed tooth plates, a feature lacking in all specimens of
P. gunni.
Juvenile dipnoans of other species are known, which also show that the tooth plates develop in the smallest observable individuals. The occurrence of
P. gunni
in the Sandwick fish bed in Orkney is confirmed, and it is confirmed too that it does not occur at Baligill, Sutherland.
The Cleveland Dyke in southern Scotland
Authors: Dagley P. , Skelhorn R. R. , Mussett A. E. , James S. , Walsh J. N.
Published: January 2010

Synopsis

There have been a number of recent papers on ‘giant dykes’, i.e. dykes exceeding 100 km in length. This paper extends the known length of the Tertiary (Palaeogene) Cleveland Dyke (CD) by about 64 km, giving a total proven length of
c.
260 km. The results of a detailed investigation using ground magnetic surveys have discovered 26 additional exposures in southern Scotland, allowing magnetic, petrographic and geochemical measurements and magnetic modelling to be carried out, resulting in one of the most detailed studies of a ‘giant’ dyke.

The structure of the CD complex in the Southern Uplands of SW Scotland has been influenced by pre-existing structures, in particular faults and granitic intrusions. It is chemically heterogeneous without systematic trend along its length. This heterogeneity, plus segmentation along strike, numerous offsets, in particular one of 5 km along the Water of Ken, en-échelon structure, narrow width at many localities (2.3–0.8 m) with lack of baking of adjacent country rocks, all argue strongly against lateral intrusion from the Mull intrusive complex, as has been proposed. Instead, aeromagnetic surveys and wide-angle seismic and gravity surveys make it probable that the dyke relates to a regional magma reservoir beneath the Southern Uplands.
A comparison between dinosaur footprints from the Middle Jurassic of the Isle of Skye, Scotland, UK, and Shell, Wyoming, USA
Authors: Clark N. D. L. , Brett-Surman M. K.
Published: January 2010

Synopsis

Measurements of Middle Jurassic tridactyl dinosaur tracks from the Bathonian, Lealt Shale, Valtos Sandstone, Duntulm and Kilmaluag formations of the Isle of Skye, UK, are compared to the same measurements taken for dinosaur footprints from the Bajocian, Gypsum Spring and the Bathonian, Sundance Formation of the Bighorn Basin, Wyoming, USA. Principal component analysis of the data suggests that the smaller footprints from the Valtos Sandstone and Kilmaluag formations are indistinguishable from the footprints of the Sundance Formation. The single footprint from the Lealt Shale Formation is similar to the larger footprints from the Valtos Sandstone Formation. The footprints from the Duntulm and Gypsum Springs formations form distinct groupings from all other footprints. Four different groupings of dinosaur footprints can be recognized from the principal component analysis that may represent at least four different types of dinosaur.
p63in Epithelial Survival, Germ Cell Surveillance, and Neoplasia
Authors: Crum Christopher P. , McKeon Frank D.
Published: January 2010

The p53homolog p63has emerged as a gene with an enormously complex function that is distinct from that of p53. It encodes two distinct transcript isoforms that have a dramatic impact on replenishment of cutaneous epithelial stem cells and on ovarian germ cell survival. However, although these two fundamental roles of p63 attest to its powerful place in development, its other functions—specifically the apparent capacity of p63, when induced, to supervise the emergence of new cell populations in the breast, prostate, cervix, and upper reproductive tract—are shared by embryo and adult. These observed functions may only scratch the surface of a repertoire that has been postulated to encompass a range of cellular activities, as evidenced by the fact that p63 proteins have been shown to potentially bind to over 5800 target sites. Whether tumorigenic pathways are also involved, and to what extent, is a subject of both promise and controversy that remains to be resolved.
The Senescence-Associated Secretory Phenotype: The Dark Side of Tumor Suppression
Authors: Coppé Jean-Philippe , Desprez Pierre-Yves , Krtolica Ana , Campisi Judith
Published: January 2010

Cellular senescence is a tumor-suppressive mechanism that permanently arrests cells at risk for malignant transformation. However, accumulating evidence shows that senescent cells can have deleterious effects on the tissue microenvironment. The most significant of these effects is the acquisition of a senescence-associated secretory phenotype (SASP) that turns senescent fibroblasts into proinflammatory cells that have the ability to promote tumor progression.
Mammalian Sirtuins: Biological Insights and Disease Relevance
Authors: Haigis Marcia C. , Sinclair David A.
Published: January 2010

Aging is accompanied by a decline in the healthy function of multiple organ systems, leading to increased incidence and mortality from diseases such as type II diabetes mellitus, neurodegenerative diseases, cancer, and cardiovascular disease. Historically, researchers have focused on investigating individual pathways in isolated organs as a strategy to identify the root cause of a disease, with hopes of designing better drugs. Studies of aging in yeast led to the discovery of a family of conserved enzymes known as the sirtuins, which affect multiple pathways that increase the life span and the overall health of organisms. Since the discovery of the first known mammalian sirtuin, SIRT1, 10 years ago, there have been major advances in our understanding of the enzymology of sirtuins, their regulation, and their ability to broadly improve mammalian physiology and health span. This review summarizes and discusses the advances of the past decade and the challenges that will confront the field in the coming years.
Mitochondrial Energetics and Therapeutics
Authors: Wallace Douglas C. , Fan Weiwei , Procaccio Vincent
Published: January 2010

Mitochondrial dysfunction has been linked to a wide range of degenerative and metabolic diseases, cancer, and aging. All these clinical manifestations arise from the central role of bioenergetics in cell biology. Although genetic therapies are maturing as the rules of bioenergetic genetics are clarified, metabolic therapies have been ineffectual. This failure results from our limited appreciation of the role of bioenergetics as the interface between the environment and the cell. A systems approach, which, ironically, was first successfully applied over 80 years ago with the introduction of the ketogenic diet, is required. Analysis of the many ways that a shift from carbohydrate glycolytic metabolism to fatty acid and ketone oxidative metabolism may modulate metabolism, signal transduction pathways, and the epigenome gives us an appreciation of the ketogenic diet and the potential for bioenergetic therapeutics.
Differential roles of stretch-sensitive pelvic nerve afferents innervating mouse distal colon and rectum
Authors: Feng Bin , Brumovsky Pablo R. , Gebhart Gerald F.
Published: January 2010

Information about colorectal distension (i.e., colorectal dilation by increased intraluminal pressure) is primarily encoded by stretch-sensitive colorectal afferents in the pelvic nerve (PN). Despite anatomic differences between rectum and distal colon, little is known about the functional roles of colonic vs. rectal afferents in the PN pathway or the quantitative nature of mechanosensory encoding. We utilized an in vitro mouse colorectum-PN preparation to investigate pressure-encoding characteristics of colorectal afferents. The colorectum with PN attached was dissected, opened longitudinally, and pinned flat in a Sylgard-lined chamber. Action potentials of afferent fibers evoked by circumferential stretch (servo-controlled force actuator) were recorded from the PN. Stretch-sensitive fibers were categorized into the following four groups: colonic muscular, colonic muscular/mucosal, rectal muscular, and rectal muscular/mucosal. Seventy-nine stretch-sensitive PN afferents evenly distributed into the above four groups were studied. Rectal muscular afferents had significantly greater stretch-responses than the other three groups. Virtually all rectal afferents (98%) had low thresholds for response and encoded stimulus intensity into the noxious range without obvious saturation. Most colonic afferents (72%) also had low thresholds (<14 mmHg), but a significant proportion (28%) had high thresholds (>18 mmHg) for response. These high-threshold colonic afferents were sensitized to stretch by inflammatory soup; response threshold was significantly reduced (from 23 to 12 mmHg), and response magnitude significantly increased. These results suggest that the encoding of mechanosensory information differs between colonic and rectal stretch-sensitive PN afferents. Rectal afferents have a wide response range to stretch, whereas high-threshold colonic afferents likely contribute to visceral nociception.
Central CO2chemoreception and integrated neural mechanisms of cardiovascular and respiratory control
Authors: Guyenet Patrice G. , Stornetta Ruth L. , Abbott Stephen B. G. , Depuy Seth D. , Fortuna Michal G. , Kanbar Roy
Published: January 2010

In this review, we examine why blood pressure (BP) and sympathetic nerve activity (SNA) increase during a rise in central nervous system (CNS) Pco2(central chemoreceptor stimulation). CNS acidification modifies SNA by two classes of mechanisms. The first one depends on the activation of the central respiratory controller (CRG) and causes the much-emphasized respiratory modulation of the SNA. The CRG probably modulates SNA at several brain stem or spinal locations, but the most important site of interaction seems to be the caudal ventrolateral medulla (CVLM), where unidentified components of the CRG periodically gate the baroreflex. CNS Pco2also influences sympathetic tone in a CRG-independent manner, and we propose that this process operates differently according to the level of CNS Pco2. In normocapnia and indeed even below the ventilatory recruitment threshold, CNS Pco2exerts a tonic concentration-dependent excitatory effect on SNA that is plausibly mediated by specialized brain stem chemoreceptors such as the retrotrapezoid nucleus. Abnormally high levels of Pco2cause an aversive interoceptive awareness in awake individuals and trigger arousal from sleep. These alerting responses presumably activate wake-promoting and/or stress-related pathways such as the orexinergic, noradrenergic, and serotonergic neurons. These neuronal groups, which may also be directly activated by brain acidification, have brainwide projections that contribute to the CO2-induced rise in breathing and SNA by facilitating neuronal activity at innumerable CNS locations. In the case of SNA, these sites include the nucleus of the solitary tract, the ventrolateral medulla, and the preganglionic neurons.
Operational point of neural cardiovascular regulation in humans up to 6 months in space
Authors: Verheyden B. , Liu J. , Beckers F. , Aubert A. E.
Published: January 2010

Entering weightlessness affects central circulation in humans by enhancing venous return and cardiac output. We tested whether the operational point of neural cardiovascular regulation in space sets accordingly to adopt a level close to that found in the ground-based horizontal position. Heart rate (HR), finger blood and brachial blood pressure (BP), and respiratory frequency were collected in 11 astronauts from nine space missions. Recordings were made in supine and standing positions at least 10 days before launch and during spaceflight ( days 5– 19, 45– 67, 77– 116, 146– 180). Cross-correlation analyses of HR and systolic BP were used to measure three complementary aspects of cardiac baroreflex modulation: 1) baroreflex sensitivity, 2) number of effective baroreflex estimates, and 3) baroreflex time delay. A fixed breathing protocol was performed to measure respiratory sinus arrhythmia and low-frequency power of systolic BP variability. We found that HR and mean arterial pressure did not differ from preflight supine values for up to 6 mo in space. Respiration frequency tended to decrease during prolonged spaceflight. Concerning neural markers of cardiovascular regulation, we observed in-flight adaptations toward homeostatic conditions similar to those found in the ground-based supine position. Surprisingly, this was not the case for baroreflex time delay distribution, which had somewhat longer latencies in space. Except for this finding, our results confirm that the operational point of neural cardiovascular regulation in space sets to a level close to that of an Earth-based supine position. This adaptation level suggests that circulation is chronically relaxed for at least 6 mo in space.