bluuebunny/crossref_metadata_2025 huggingface dataset:
Ice-wedge cast network in eastern Berwickshire
Authors: Greig D. C.
Published: January 2010

Synopsis

A polygonal ground-pattern observed from the air on fluvio-glacial gravels in eastern Berwickshire is interpreted as being due to seasonal cracking and ice-wedging, probably in periglacial conditions.
Asymmetrical folding in the Hawick Rocks of the Galloway area, Southern Uplands
Authors: Stringer P. , Treagus J. E.
Published: January 2010

Synopsis

The asymmetry, scale and regionally uniform distribution of F
1
folds in the Hawick Rocks do not support previous interpretations of the major structure. The F
1–
F
4
phases of folding previously proposed are re-interpreted as two phases. The F
2
folds are developed mainly along a 2–3 km wide strike belt. Variation in the scale and asymmetry of F
1
folding across the Southern Uplands is outlined. The style of F
1
folding in the Hawick Rocks is consistent with deformation accompanying sequential accretion of sediments at a subduction zone.
Facies breaks in the Scottish Passage Group and their possible correlation with the Mississippian—Pennsylvanian hiatus
Authors: Read W. A.
Published: January 2010

Synopsis

The Scottish Passage Group (Namurian E
2
to Westphalian A) contains many minor disconformities, but its thickest and most complete development in the Kincardine Basin east of Stirling reveals only three major depositional breaks or facies changes sufficiently important to be considered as possible correlatives of the Mississippian-Pennsylvanian hiatus of North America. They are here named Horizons 1 to 3.

Even in the area of maximal subsidence, Horizon 1 just above the Castlecary Limestone is marked by deep channelling. Despite the following flood of coarse sandy detritus, widespread marine transgressions continued (Nos. 1 to 2 Marine Bands). Horizon 2, which lies just above No. 2 Marine Band, heralded a regressive period with meandering river environments and only one local marine incursion. Above No. 3 Marine Band Group with its renewed widespread marine transgressions, Horizon 3 marks the onset of another regressive period when marine bands became impersistent, thin and faunally impoverished, e.g. Nos. 5 and 6 Group, overbank ‘fines’ were seldom preserved and braided rivers possibly became dominant.

Horizon 1 is much the best example of a major regression during the Scottish Namurian. Nevertheless biostratigraphical evidence favours Horizon 2 as being more probably equivalent to the Mississippian-Pennsylvanian hiatus.
Highland Border rocks at Loch Lomond and Aberfoyle
Authors: Henderson W. G. , Fortey N. J.
Published: January 2010

Synopsis

Serpentinites, spilites, rudites, arenites and black slates at the Highland Boundary between Loch Lomond and Aberfoyle display a complex history of sedimentation, alteration and tectonism. Fragmental serpentinites, probably of sedimentary origin, occur at Balmaha, Loch Lomond, and at two other localities at the Highland Boundary N and W of Kirriemuir. Cleaved arenites and rudites contain fragments of ultrabasic rock including silicified serpentinite. The serpentinites were not intruded into the Highland Boundary Fault-zone, but had a history of uplift, erosion and displacement prior to major faulting in the Devonian.

Garnetiferous hornblende-schists near Aberfoyle are more highly metamorphosed and deformed than adjacent black slates and nearby Dalradian greywackes. Probably dynamothermal in origin, they resemble hornblende-schist slivers in the soles of allochthonous ophiolitic thrust-sheets.

The diverse Highland Border rock-types probably formed in a restricted ocean basin and were brought into contact with the Dalradian by crustal shortening during the Grampian orogeny.
Early Wenlock acritarchs from the Knockgardner and Straiton Grit Formations of Knockgardner, Ayrshire
Authors: Dorning Ken J.
Published: January 2010

Synopsis

Palynomorphs recovered from three samples of the Silurian at Knock-gardner, Ayrshire, show well preserved acritarchs of a moderate diversity assemblage from the Knockgardner Formation, and a low diversity assemblage from the Straiton Grit Formation. The taxa recorded establish an early Wenlock age for the Knockgardner Formation, where the shelly macrofossil age is inconclusive.
Hydrothermal Sr exchange at the contact of the Dumbarton Rock basalt
Authors: Dickin A. P. , Whyte F.
Published: January 2010

Synopsis

The margin of the Dumbarton Rock basalt was contaminated by sedimentary Sr with a high
87
Sr/
86
Sr ratio. This was probably introduced by hydrothermal fluids in a process of fluid–rock Sr exchange. Fluids followed a preferred path just inside the contact where permeability was increased by cooling joints.
Zr-rich pyroxenes and glauconitic minerals in the Tertiary alkali granite of Ailsa Craig
Authors: Harding R. R.
Published: January 2010

Synopsis

The petrographical setting of pyroxene and mica-group minerals in the Tertiary alkali granite of Ailsa Craig is described. Electron microprobe analyses of pyroxenes ranging from He
87
Ac
13
to He
0
Ac
100
are given and their variable contents of minor elements (Al, Ti and Zr) shown to compare closely with a similar occurrence recently described from a South Greenland nepheline-syenite. Glauconitic minerals occur in patches of interstitial crystallisation in the granite.
The metamorphic environment of the Foyers Granitic Complex
Authors: Tyler I. M. , Ashworth J. R.
Published: January 2010

Synopsis

In rocks assigned to the Central Highland Division north-east of the Foyers Complex, a Cordierite-K feldspar Zone is developed at the highest grades of contact metamorphism. Outside this zone, the muscovite + quartz/sillimanite + K feldspar transition is ill-defined because muscovite tends to have been consumed by a lower-grade garnet-resorbing reaction, in response to reduced pressure. Within the Cordierite-K feldspar Zone garnet was equilibrated with cordierite and biotite at
c.
650–680°C. Cordierite + K feldspar coexistence at these temperatures requires water activities far below the water-saturated condition
a

H
2
O

= 1. The Hold-away-Lee treatment of biotite + quartz + cordierite + garnet + K feldspar + sillimanite gives
a

H
2
O

≈ 0·15, and a pressure of approximately 3·9 kbar. The unusually low
a

H
2
O

permits cordierite + K feldspar coexistence without melting, which is consistent with the scarcity of contact-migmatitic phenomena other than intrusive veining. Low
a

H
2
O

is attributed to a combination of protracted cooling from the regional metamorphic climax and general rarity of muscovite. In comparison with the Strontian complex, the (drier) metamorphic environment at Foyers supports geochronological arguments that the two complexes are distinct. The difference in
a

H
2
O

may bear on structural differences between the two areas.
The Larne No. 2 Borehole: discovery of a new Permian volcanic centre
Authors: Penn I. E. , Holliday D. W. , Kirby G. A. , Kubala M. , Sobey R. A. , Mitchell W. I. , Harrison R. K. , Beckinsale R. D.
Published: January 2010

Synopsis

The Larne No. 2 Borehole is situated in an area where Mesozoic and Tertiary rocks cover the assumed westerly extension of the Midland Valley of Scotland. It penetrated 2880·36 m of New Red Sandstone sediments and volcanic rocks and is one of the deepest boreholes drilled in Ireland. Beneath thin Quaternary clays, a Triassic succession consisting of saliferous Mercia Mudstone Group (958·3 m), overlying Sherwood Sandstone Group (648·3 m) was encountered. Permian Upper Marls (185·4 m), including a thick (113·1 m) basal halite, and Magnesian Limestone (21·6 m) successively underlie the Triassic rocks and with the latter may be correlated with similar sequences in Northern Ireland, England and the Irish Sea. The Permian succession beneath the Magnesian Limestone resembles that of south-west Scotland and comprises 440·l7 m of sandstone and pebble conglomerate overlying a hitherto unsuspected 616·7 m proven thickness of intermediate to basic volcanic rocks. These altered lavas have yielded K/Ar ages of
c
. 245 ± 13 Ma and the balance of evidence suggests that they are of early Permian age.
The geochemistry of the Strathconon amphibolites, Northern Scotland
Authors: Winchester J. A.
Published: January 2010

Synopsis

The Strathconon ortho-amphibolites were intruded into Glenfinnan and Loch Eil Division metasediments of the Moine Assemblage before the area was deformed in late Precambrian time. A chemical study has indicated that they consist of a single suite of variously fractionated tholeiitic sills and dykes which can be distinguished chemically both from the Y-poor amphibolites of the Morar Nappe and from more Y-rich amphibolites within the Central Ross Nappe spatially associated with the Quoich Line in Inverness-shire. The chemical distinction between amphibolites from the two nappes requires that major transport of the overlying Central Ross Nappe occurred after the intrusion of the basic sills.
A geometrical study of the Arnaboll and Heilam thrust sheets, NW of Ben Arnaboll, Sutherland
Authors: Coward Michael P.
Published: January 2010

Synopsis

The geometries of thrusts in the Arnaboll and Heilam sheets, part of the Moine thust zone of NW Scotland, are described using branch line maps, which are the projections on to a map of the lines where thrusts join, and also cut-off maps, which are the projections of where thrusts cut through the strata. The thrusts are shown to have developed in a WNW propagating piggy-back sequence; structures developed on the lower thrusts cut or fold earlier higher level thrusts. Nowhere do thrusts cut down stratigraphy in the transport direction, and a previous claim that the Arnaboll thrust was out of sequence was based on a mis-correlation of thrusts.
The pyroclastic rocks and rhyolitic lavas of the Eastern Red Hills district, Isle of Skye
Authors: Bell Brian R.
Published: January 2010

Synopsis

Mixed pyroclastic rock accumulations in the Eastern Red Hills district of the Tertiary igneous centre of Skye show a wide range in composition and mode of formation. Prior to this investigation these volcanic products were interpreted as vent infillings. It is shown that this model is unrealistic, as detailed mapping demonstrates that they are bedded, subaerial and subaqueous deposits. Chaotic, polylithic agglomerates, at least 300 m thick, are preserved in a ring-faulted mass in the Kilchrist area and are intercalated with thin acid tuffs, basic tuffs (grading towards coarser material) and ignimbrites. A hyaloclastite horizon is also present within the sequence. It is concluded that these accumulations of pyroclastic rocks do not show close genetic links with the later, spatially-associated granites of the Eastern Red Hills Centre, but may have originated by explosive volcanism triggered off by earlier events in the Skye Centre. Later subaerial and subaqueous processes greatly modified their primary appearance. Intercalated with the pyroclastic rocks are rhyolite lavas which are associated with the subvolcanic granites of the district. These lavas provide evidence of the close connection between surface volcanism and subvolcanic activity in the Skye Centre.
The sedimentology of the Lower Old Red Sandstone near New Aberdour, Grampian Region
Authors: Sweet I. P.
Published: January 2010

Synopsis

The Lower Old Red Sandstone exposed on the coast near New Aberdour can be divided into a lower sandstone and conglomerate formation and an upper sandy mudstone formation which contains several sandstone lenses in its upper part. The lower formation can be further subdivided into four lithofacies assemblages (Facies 1A to 1D) consisting of, respectively, debris flow conglomerates, stream channel deposits, proximal alluvial fan deposits, and distal fan/sandflat deposits. Facies 2A of Formation 2 consists of a mud flat (playa) facies, containing evidence for pedogenesis (calcretization), and bioturbation, whereas Facies 2B, the sandstone lenses, reflect a return to higher energy, probably alluvial fan, deposition. The sediments were laid down in a small fault-bounded basin. The influence of tectonic activity and fan sedimentary processes are reflected in fining upwards ‘megasequences’ and ‘sequences’ respectively. Periods during which some fan segments and the adjacent playa received little sediment are reflected in the occurrence of numerous calcrete layers in the mudflat/playa facies.
Palaeomagnetic studies of the Orcadian Basin
Authors: Tarling D. H.
Published: January 2010

Synopsis

After removal of recently acquired viscous components, two main groups of remanent directions have been identified in Devonian rocks from the Orcadian Basin. One group, A, has a SSE, fairly shallow, reversely magnetized direction of moderate stability and is found in most rocks when partially demagnetized at 300°C or 30 mT. The other group, B, is of mixed polarity, but mostly showing southerly, horizontal directions that are only isolated close to the noise-level of measurement, usually at temperatures above 550°C. Only a few other unrelated components have been isolated. There is dispute concerning the age of both groups. The age of Group A has been suggested variously as between Devonian and Tertiary. The physical reality of Group B has been disputed, but has been considered to originate in the Devonian. Comparison with ‘accepted’ poles suggest that A is probably Permian and B, if real, of mid-Carboniferous age. Of the remaining directions, only those of the Orkney-Shetland volcanics appear to correspond with a possible Devonian age. An evaluation of the available palaeomagnetic data shows no evidence for major post Devonian motions along the Great Glen Fault, but suggests that the Orcadian Basin moved from about 20°S in the early Devonian, to
c.
15°S in late Devonian times, passing across the equator in early Upper Carboniferous times.
Palaeomagnetism of the Sarclet Sandstone (Orcadian Basin): age perspectives
Authors: Storhaug K. , Storetvedt K. M.
Published: January 2010

Synopsis

Palaeomagnetic results from the Sarclet Sandstone Formation, stratigraphically positioned near the base of the Old Red Sandstone (ORS) sequence of Caithness, suggest the presence of two different axes of magnetization, with Dec. 211, Inc. 33 and Dec. 191, Inc. 6 respectively. The most steeply inclined magnetization is in correspondence with results from Scottish Lower Old Red Sandstone volcanics indicating that the age of the Sarclet Sandstone dates from the topmost Silurian-lowermost Devonian. The abundant clasts of basalts in the underlying Sarclet Conglomerate give further substance to the notion that the Lower Old Red Sandstone volcanics, which have a wide distribution in central and southern regions of Scotland, also occurred in the Caithness/Moray Firth area. It is concluded therefore that the Orcadian Basin developed concurrently with the ORS basins of the Midland Valley and the Scottish Borders. It is inferred that the second magnetization (with shallow inclination) was imposed at around Middle Devonian, but owing to a relatively early silica cementation the Sarclet Sandstone was not susceptible to acquiring the “Permian” magnetization overprint that is strongly developed in the higher stratigraphic units of the Caithness Old Red Sandstone.
Hydrocarbon source rocks, reservoir rocks and migration in the Orcadian Basin
Authors: Parnell John
Published: January 2010

Synopsis

Rock-Eval pyrolysis data shows that the ORS is a viable source rock for hydrocarbons in the Orcadian Basin, and that generally the sequence is not highly mature at present. Solvent-extracted pyrolysis data indicate that migrated hydrocarbons only form a significant proportion of the total organic carbon content where this content is less than 1.5 %.

Hydrocarbons occur widely in mineral veins and fluviatile/aeolian sandstones. Hydrocarbon shows in sandstones are often adjacent to major faults, along which they may have migrated. Much porosity in the sandstone is secondary after calcite dissolution which may have been related to Permian deep weathering. Small volumes of hydrocarbons were generated by a late Permian intrusive igneous suite, but peak generation had probably occurred prior to this event.
The palaeogeography of the Middle Devonian Lower Eday Sandstone, Orkney
Authors: Astin T. R.
Published: January 2010

Synopsis

Sections through the topmost Rousay Group, and the Lower Eday Sandstone and Eday Flagstone Formations of the Eday Group can be correlated throughout eastern Orkney. The amalgamated sandstone unit of the Lower Eday Sandstone varies between 180 and 30 m in thickness. It was deposited in three interacting environments; sandy braided rivers, aeolian dunes and lake beaches.

There were two river systems; a northern, SE-flowing alluvial fan, and a southern, NE-flowing alluvial plain. The rivers prograded eastwards across the lake basin. At times when the lake was full, beach ridges formed on the alluvial surfaces at various heights above the lake floor. Dominantly NNW winds reworked the sands, locally building up a thick dune field on the western part of the alluvial fan. The distribution of the beach ridges constrains the depth range of the Orcadian lake when it was full, showing it rarely exceeded 20 m depth during the Lower Eday Sandstone.

Active extensional faulting during sedimentation had an important control on the palaeogeography, and on the subsidence pattern. This episode of extension gave rise to much of the present structure of the Orkneys.
Protalus rampart development and the limits of former glaciers in the vicinity of Baosbheinn, Wester Ross
Authors: Ballantyne Colin K.
Published: January 2010

Synopsis

J. B. Sissons’ interpretation of a massive debris accumulation at the NW end of the Baosbheinn ridge in terms of two stages of protalus rampart development is shown to be inconsistent with the field evidence, and palaeoclimatic inferences and rockwall retreat rate calculations based on this interpretation are consequently invalid. Part of the debris accumulation is reinterpreted as two lateral moraine fragments that were deposited at the southern limit of westwards-moving ice from the Loch Maree trough at the maximum of the Wester Ross Readvance, some time before
c.
13,000 B.P. During the Loch Lomond Stadial of
c.
11,000–10,000 B.P. two valley glaciers advanced northwards on either side of Baosbheinn into the area formerly occupied by Wester Ross Readvance ice and truncated the earlier readvance limit, thereby isolating the lateral moraine fragments on the flanks of Baosbheinn. The upper part of the debris accumulation is apparently a giant protalus rampart of Loch Lomond Stadial age, but various characteristics of this feature suggest that unlike other Lateglacial ramparts it was not formed by slow rockfall accumulation. Instead, it probably formed when a massive rockslide or series of rockslides involving failure of
c.
200,000 m
3
of rock over-rode a former snowbed and accumulated as a boulder ridge that partly buried the higher lateral moraine fragment.
The role of the Cruachan Lineament during Dalradian evolution
Authors: Graham Colin M.
Published: January 2010

Synopsis

Geological and geophysical evidence is reviewed for the existence of a trans-Caledonoid (NW–SE) lineament, the Cruachan Lineament, in the Scottish Caledonides, separating a high-density SW Highland block dominated by abundant late Precambrian Dalradian mafic rocks in which the Moine is absent from a low density Moine plus Dalradian Central Highland block poor in mafic rocks. Contrasted metamorphic P-T-time histories are predicted on opposite sides of the lineament.

An alternative model of early Dalradian evolution is proposed in which basaltic volcanism and sedimentation in the SW Scottish Highlands occurred in a quasi-oceanic trans-Caledonoid pull-apart basin bounded along its NE side by a major fault now identified as the Cruachan Lineament. The Dalradian basin(s) may have experienced right-lateral translation relative to the crustal block to the SE along a dextral transcurrent fault zone possibly in the vicinity of the Highland Boundary Fault during late Precambrian time. In this model, the Dalradian terrain may provide no evidence regarding the early history of the NW side of the lapetus Ocean.
Nodular carbonates in the Lower Carboniferous, Cementstone Group of the Tweed Embayment, Berwickshire: evidence for a former sulphate evaporite facies
Authors: Scott W. B.
Published: January 2010

Synopsis

A small number of coarsely crystalline nodular carbonate beds of calcite and dolomite are intercalated within lacustrine sediments in the Lower Carboniferous Cementstone Group of the Tweed area. Textural and mineralogical features indicate that they represent former nodular anhydrite beds which developed in lake marginal sabkhas. The close association of these replaced sulphates with beds of cementstone (finely crystalline dolomites) favours a sabkha model for cementstone dolomitisation in which sulphate precipitation helps to promote the requisite Mg/Ca ratios in the dolomitising brines. Two main stages of diagenesis, each dominated by mineral replacement, appear to have affected the sulphate facies subsequent to its formation: initially the anhydrite was subject to partial gypsification and then, at a later stage of diagenesis, dolomite and calcite replacements of sulphate occurred.
Biotite- and garnet-forming reactions in inverted metamorphic zones in the Balquhidder region of the Scottish Dalradian
Authors: Watkins Keith P.
Published: January 2010

Synopsis

Biotite and garnet zones in the west-central Scottish Dalradian are inverted; higher grade rocks overlying lower grade rocks. Structural and textural information indicates that inversion is not due to overfolding of metamorphic zones. Peak metamorphic conditions were attained in a negative thermal gradient. Biotite forms when phengite becomes sufficiently aluminous, by means of the grade-controlled tschermak substitution, for the chlorite-phengite-biotite three-phase field to enclose the composition of the host rock on an AKF diagram. The reaction is controlled by whole-rock Al-content and metamorphic grade and has the form: chlorite + phengite → muscovite + biotite + quartz + fluid. Garnet may form by any of three continuous reactions, each dependent on rock composition; the dominant reaction (incorporating the biotite-forming reaction) has the form: chlorite(1) + phengite(1) + plagioclase(1) + calcite(1) → chlorite(2) + phengite(2) + plagioclase(2) + calcite(2) + biotite + garnet + fluid. The reactions form garnet principally at the expense of chlorite but involve all phases in the rock. The amount of garnet formed depends critically on whole-rock Mn-content. Trends in rock and mineral compositions across the biotite and garnet zones reveal nothing unusual to illuminate the problem of metamorphic inversion. Although the absence of steps, or changes of gradient, in mineral-chemical trends renders syn- or post-metamorphic thrusting an unlikely solution.
The offshore continuation of the Moine Thrust north of Shetland as deduced from basement isotopic ages
Authors: Ritchie J. D. , Hitchen K. , Mitchell J. G.
Published: January 2010

Synopsis

Caledonian isotopic ages from the southern section of the Scotland–Norway Basement Ridge effectively separated the Archaean–Proterozoic Lewisian Complex and the Lofoten-Vesterålen Complex forming the SW and NE ends of the ridge. The distribution of Caledonian and Lewisian age data to the north and west of Shetland confirm suggestions that the Moine Thrust merges generally within the region of the west margin of the Caledonian mobile belt, as seen on east Greenland. The Moine Thrust between Orkney and Shetland is offset in a dextral sense by
c.
25 km. The Walls Boundary Fault intersects the West Shetland Platform edge to the north of Shetland, with the basement displaying an apparent
c.
15 km sinistral offset.
Submerged rock platforms on the continental shelf west of Sula Sgeir
Authors: Sutherland Donald G.
Published: January 2010

Synopsis

Two major submerged erosion platforms have been identified on the north-western Scottish continental shelf to the west of Sula Sgeir. The lower, at
c.
−155 m, is up to 6 km broad but can only be traced for
c.
15 km laterally. The upper platform, at
c.
−125 m, varies between 0.8 and 3 km in width and has been traced for over 50 km in a NNE–SSW direction. The platforms are attributed to marine erosion during periods of low sea level, each platform perhaps being subjected to erosion on more than one occasion. The −155 m platform is apparently the older and was formed prior to extensive glacial erosion of the shelf. It is assigned a Late Tertiary or Early Pleistocene age. The −125 m platform post-dates glaciation of the middle shelf but in major part pre-dates the Late Devensian glacial maximum. It is assigned a Middle to Late Pleistocene age. The island of Sula Sgeir and the neighbouring sea stacks were formed when sea level was
c.
−40 m relative to that of the present.
Probable early Wenlock acritarchs from the Linkim Beds of the Southern Uplands
Authors: Molyneux S. G.
Published: January 2010

Synopsis

Thirty five samples from the Linkim Beds and the Coldingham Beds, which crop out on the Berwickshire coast north-west of Eyemouth, have been prepared for microfossils. One sample from the Linkim Beds has yielded a probable early Wenlock (mid-Silurian) acritarch assemblage, including
Tylotopalla caelamenicutis
Loeblich,
Tylotopalla wenlockia
Dorning,
Helosphaeridium
cf.
malvemense
Dorning and
Multiplicisphaeridium
sp. A. The remaining samples yielded fragments of probable organic origin, accompanied in two samples by possible sphaeromorph acritarchs which are not diagnostic of age. Recent interpretations suggest that no great stratigraphical break exists between the Linkim Beds and the Coldingham Beds, and therefore the Coldingham Beds may also be of mid-Silurian age.

The acritarchs from the Linkim Beds are sparse and the assemblage is of low diversity, comparable with assemblages from both inshore and basinal environments but contrasting with a more diverse early Wenlock assemblage from the Midland Valley, considered to indicate fully marine but relatively shallow conditions; palaeogeographical considerations suggest that the Linkim Beds were deposited in a deeper-water, basinal environment. The colour of the Linkim acritarchs indicates high-thermal maturation, palaeotemperatures attained being between 90° and 200°C, and probably towards the higher end of that range.
The Main Rock Platform (Main Lateglacial Shoreline) in Ardnamurchan and Moidart, western Scotland
Authors: Dawson Alastair G.
Published: January 2010

Synopsis

The Main Rock Platform is recognised in Ardnamurchan and Moidart, western Scotland. This shoreline (the Main Lateglacial Shoreline) has a maximum altitude of circa 7 m O.D. in eastern Loch Ailort and passes below present sea-level in western Ardnamurchan. The shoreline is glacio-isostatically tilted and declines in altitude with a regional gradient of 0.18 m/km in the direction W5°N–E5°S. However, the Main Rock Platform is absent from considerable stretches of coastline. This isolated pattern of development of the Main Rock Platform is in marked contrast with that of the SW Highlands where the platform is almost continuously developed. It is argued that the restricted distribution of platform fragments yet their often considerable widths indicate a selectivity in the processes of cold climate shore erosion that took place during the Loch Lomond Stadial. The distribution of the Main Rock Platform also implies that Loch Ailort and Loch Moidart were not occupied by glacier ice during the Stadial.
Rockall Trough—Cretaceous or Late Palaeozoic?
Authors: Smythe David K.
Published: January 2010

Synopsis

The Rockall Trough is the most southerly and widest part of the pre-Tertiary ‘proto North Atlantic’ rift zone running from the Porcupine Bank region west of Ireland to the Vøring Plateau off central Norway. Although the northerly part of this rift is intra-continental, the southern part is quasi-oceanic in origin, but of uncertain age. The many arguments for Cretaceous sea floor spreading are evaluated in turn; the few apparently valid ones remaining are shown to relate not directly to the Rockall Trough, but to a newly-identified spreading phase of approximately mid-Cretaceous age which partially opened up the Hatton-Rockall Basin. The opening of the Rockall Trough predates this. Stratigraphic evidence suggests that the proto North Atlantic is pre-Cretaceous, and probably even pre-Jurassic, in age. The rival arguments for late Palaeozoic (late Carboniferous—early Permian) sea floor spreading are all consistent with an important phase of rifting at that time, but they provide no direct evidence for opening. No detailed arguments have yet been proposed for Jurassic, Triassic, or late Permian sea floor spreading. New modelling of the magnetic anomaly over Rosemary Bank by MV Wood supports a Triassic or earlier age, but the pre-Upper Cretaceous sedimentary infill of 2–3 km in the Trough seems to be rather thin for such an early age. However, by combining the pre-Cretaceous stratigraphic Constraint on the age of opening with the assumption that the major rifting episode was an immediate precursor of spreading, a tentative conclusion is that the Rockall Trough was initiated as a rift, and then opened by a quasi- sea floor spreading mechanism, during the late Carboniferous to early Permian.
Fold basins in Late–Devensian glacimarine sediments at Shieldhall, Glasgow
Authors: McMillan A. A. , Browne M. A. E.
Published: January 2010

Synopsis

The paper describes fold basins (non-diastrophic centroclinal folds) at least 80 metres long, 50 metres wide and 10 metres deep developed in a Late–Devensian glacimarine sequence consisting of sea-bed clays and silts with underlying submarine glacial outwash sands. The bedding of the sediments dips centroclinally at angles generally ranging from 15° to 45°. Locally near basin margins, dips in excess of 70° are recorded. Two modes of origin for the basins are discussed. Firstly, they may represent the sites of kettle holes formed when ice, buried in the sands for a long period during which the clays were deposited, finally melted. Secondly, they may have formed during broad scale deformation which resulted from extensive loading of rapidly deposited clays into underlying mobile sands. Basin formation involving the development of kettle holes is favoured. Water from the melting ice and interstitial pore water, trapped initially in the sands by the overlying thick seal of cohesive deposits, escaped upwards during downwarping of the basins. This may have caused diapiric movement of the sands and resulted in local oversteepening of basin margins.
Further evidence for a single polarity and a common source for the quartz-porphyry intrusions of the Arran area
Authors: Mussett A. E. , Dagley P. , Skelhorn R. R.
Published: January 2010

Synopsis

New evidence supports the proposition that all the Tertiary quartz-porphyry intrusions of Arran and Bute, which have a geographic span of 35 km, are normally magnetised. This is the only known correlation between magnetic polarity and petrography in the British Tertiary Igneous Province. It is most easily explained by a single magma source supplying all the quartz-porphyry bodies. The bodies were probably intruded during a single normal magnetic interval lasting about 1/2 Ma, about 58 Ma ago.

This significant correlation between petrography and polarity could help to erect the Tertiary igneous succession of Arran by use of the quartz-porphyry intrusions as a ‘marker horizon’.
Minicaris brandi
Schram 1979, a syncarid crustacean from the Namurian (Carboniferous).
Authors: Clark Neil D. L.
Published: January 2010

Synopsis

Further discoveries of
Minicaris brandi,
from the Namurian shales near Glasgow, provide an opportunity to understand more clearly the affinities of this syncarid crustacean. New morphological features, such as the transverse grooves and the lateral ridges on the thoracic somites, and the annulate and setose pleopods, suggests affinities with the Squillitidae. A reconstruction of
M. brandi
incorporating these new features is proposed.
The age of the Norwick hornblendic schists of Unst and Fetlar and the obduction of the Shetland ophiolite
Authors: Flinn Derek , Miller J. A. , Roddom D.
Published: January 2010

Synopsis

The Norwick hornblendic schists occur as tectonic slices in schuppen-zone-like
mélanges
below the serpentinized ultramafic–basic nappes forming the Shetland ophiolite. The Norwick hornblendic schists, like the hornblendic schists in other ophiolitc complexes, are of ocean-floor basaltic composition and locally show a rapid change in grade from greenschists via green-hornblende-schist to brown-hornblende-schist with salite and garnet. Hornblende-schists of this type are generally considered to have been formed by dynamothermal metamorphism of sea floor over-ridden by obducting hot mantle at the onset of obduction. However, in Shetland the highest grade hornblende-schist occurs in contact with overlying serpentinite and separated from it by a wide zone of low-grade cataclasis. The sample of high-grade Norwick hornblende-schist which was dated for this paper has suffered a thermal, not a dynamothermal, metamorphism and was metamorphosed at about 10 kbars. Furthermore the obducted mantle shows evidence of having been serpentinized before the obduction and so was incapable of causing the metamorphism. Hornblende separated from the sample of high-grade schist gave a step-heating
40
Ar/
36
Ar versus
39
Ar/
36
Ar isochron age of 498 ± 2 Ma and a total fusion age of 495 ± 1 4 Ma. Ages obtained from the high-grade facies of hornblende-schists from other ophiolites are generally considered to date the onset of obduction. For the Shetland ophiolite the date obtained is earlier than equivalent dates obtained for the Newfoundland and northern Quebec ophiolites but about the same as dates obtained from the southern Quebec and Ballantrae ophiolites, all of which belong to the Caledonian–Northern Appalachian orogenic belt. The Norwick hornblendic schists show a different relationship t o the ophiolite to that shown by hornblende-schists elsewhere.
Older Granites in the South-eastern Scottish Highlands
Authors: Robertson S.
Published: January 2010

Synopsis

Sillimanite grade metamorphism and pervasive migmatisation of upper Argyll Group and Southern Highland Group Dalradian metasediments in the South-east Highlands overlapped a major episode of recumbent folding, D3. Granites were emplaced before and after D3. Tectonic, metamorphic and magmatic events related to D3 were particularly complex in this region.
Palaeomagnetic conglomerate tests on basal Stoer Group sediments, NW Scotland
Authors: Piper J. D. A. , Poppleton T. J.
Published: January 2010

Synopsis

To delimit the age of magnetisation of the Lewisian metamorphic complex, palaeomagnetic conglomerate tests have been undertaken on basal Stoer Group breccias and conglomerates from the Stoer Peninsula and Enard Bay. At each location detailed thermal demagnetisation of Lewisian gneiss and amphibolite boulders isolates discrete remanence vectors which are accordant within-clasts and dispersed between-clasts. This demonstrates that the bulk of the remanence in the Lewisian Complex predates all Torridonian sedimentation. The only sign of a Torridonian burial remanence is identified in a few clasts from the basal breccias. These possess a discrete magnetite-held overprint, residing mostly in less than 10 per cent. of the total remanence, with a direction corresponding to the remanence in the sandstone matrix. Higher conglomerates show random magnetisations with the exception of some alien porphyry pebbles which have a Mesozoic overprint residing in both magnetite and hematite. The Stoer Group sediments were deposited in low palaeolatitudes of
c.
11°. The Lewisian Complex appears to possess post-Laxfordian remanence uncontaminated by later thermal and tectonic events.
Trilobites from Kilbucho and Wallace’s Cast and the location of the Northern Belt of the Southern Uplands during the late Ordovician
Authors: Owen A. W. , Clarkson E. N. K.
Published: January 2010

Synopsis

Fifteen trilobite species are recorded from the Kirkcolm Formation in the Northern Belt of the Southern Uplands at Kilbucho and Wallace’s Cast, some 12 km apart along the regional strike. Both faunas are from mudstones which overlie a fossiliferous conglomerate. All of these sediments may have been deposited following episodes of mass flow from the north and the faunas were displaced from shallower water habitats. Thirteen of the trilobite taxa can be recognised below family level and eight of these are identical to or very closely allied to species in the early to mid-Caradoc at Girvan and at Pomeroy, Co. Tyrone to the north of the Southern Uplands Fault. This strong faunal similarity suggests, contrary to some tectonic models, that there may have been no more than a few hundred kilometres of strike-slip displacement (possibly much less) along the Southern Uplands Fault.
Walking traces of the giant myriapod
Arthropleura
from the Strathclyde Group (Lower Carboniferous) of Fife
Authors: Pearson Paul N.
Published: January 2010

Synopsis

The discovery of the trace fossil
Diplichnites cuithensis,
the locomotory track of the giant myriapod
Arthropleura,
is reported from the Strathclyde Group (Lower Carboniferous) of Fife. Twelve different trackways have been identified on a single bedding plane. Other imprints on the same bed record the thorough disruption of the sediment by the repeated superimposed footfalls of the trailmaker. The sedimentary environment of the sequence is similar to other known examples of
Diplichnites cuithensis
and supports the hypothesis of a terrestrial habit for
Arthropleura.
This occurrence is the earliest yet recorded for such trackways and indicates an extension o f the range of
Arthropleura
to the Lower Carboniferous.
On the age of the Upper Ostrea Member, Staffin Bay Formation (Middle Jurassic) of north-west Skye
Authors: Riding J. B.
Published: January 2010

Synopsis

The precise age, late Bathonian or early Callovian, of the Middle Jurassic Upper Ostrea Member (Staffin Bay Formation) of NW Skye, Inner Hebrides has proved controversial. Twelve samples from the type section at Dunans, Staffin Bay, Skye yielded palynofloras rich in miospores with subordinate proportions of marine microplankton. All the samples produced low diversity dinoflagellate cyst florules which include
Meiourogonyaulax caytonensis, M. planoseptata, Mendicodinium groenlandicum
and
Rhynchodiniopsis cladophora
and thus indicate an early Callovian age. The Upper Ostrea Member represents, therefore, the oldest Callovian strata in Scotland and is coeval with the Fleet Member of England. The Staffin Bay Formation, with marine macrofauna and microplankton, overlies the regressive Skudiburgh Formation (Great Estuarine Group) and this boundary has been deemed to be a genetic sequence boundary. This interpretation is consistent with current assessments of global eustasy.
Glaciotectonic structures on altered dolostones in the Isle of Skye, western Scotland
Authors: Le Coeur C. , Kuzucuoglu C.
Published: January 2010

Synopsis

A river section, located near the Eastern Red Hills of Skye, shows a glaciotcctonic structure resting upon altered dolostones. Alteration of the Cambrian dolostones along a dyke results from hydrothermal processes associated with the Tertiary regional igneous activity. The argillaceous substratum is disturbed and sheared by a moraine deposit related to a local ice advance. Incorporation of clay elements into the moraine sole is explained by powerful and abundant subglacial water pressure.
The sedimentology of the Neoproterozoic Grampian Group and the significance of the Fort William Slide between Spean Bridge and Rubha Cuil-cheanna, Inverness-shire
Authors: Glover B. W.
Published: January 2010

Synopsis

The Neoproterozoic metasedimentary rocks between Spean Bridge and Rubha Cuil-cheanna in the Central Highlands of Scotland form part of the Grampian and Appin Groups of the Caledonides. The oldest strata, the Fort William Formation comprise an outer shelf, storm-dominated, muddy (semi-pelitic) sequence, with minor shallowing events represented by thinner arkosic (psammitic) intercalations. Infrequent dropstone deposits are interpreted as evidence of glacial influences. The transition into the overlying Inverlair Formation records a basin shoaling event which resulted in coastal (?estuarine) sedimentation. Deposition of the overlying Spean Viaduct Quartzite (Appin Group) reflects slower subsidence rates and greater (tidal?) sediment reworking.

The ‘Fort William Slide’, previously interpreted as tectonic in origin, is here regarded as a localised intra-Appin Group unconformity. This cuts out much of the Grampian Group and the Lochaber Subgroup toward s Rubha Cuil-cheanna and represents the culmination of basin shoaling initiated during Grampian Group times. There was no significant tectonic movement along the unconformity due to its unsuitable orientation. Above the unconformity Ballachulish Subgroup strata on-lap towards the south. To the east of the area (e.g. Glen Spean) continuous sedimentation may have occurred throughout Appin Group times.
Evidence for sinistral shear associated with the emplacement of the early Devonian Etive dyke swarm
Authors: Morris G. A. , Hutton D. H. W.
Published: January 2010

Synopsis

Examination of dykes in a
c.
25 km
2
area of the Caledonoid Etive dyke swarm (
c.
400 Ma) reveals from matching contact re-entrants, oblique dyke offshoots, asymmetric dyke terminations, oblique bridges and actual dated fault displacements, that sinistral shear was associated with the dyke emplacement mechanisms. Larger scale en-echelon and stepping patterns confirm that sinistral shear was an important component in the intrusion of the swarm as a whole.
Geochemistry of a Silurian metabentonite and associated apatite from the North Esk Inlier, Pentland Hills
Authors: Batchelor R. A. , Clarkson E. N. K.
Published: January 2010

Synopsis

Geochemical data are presented for an important metabentonite horizon within the Upper Llandovery and early Wenlock succession of the North Esk Inlier of the Pentland Hills. The metabentonite marks a horizon of rapid faunal change, with a rich assemblage below and an impoverished assemblage above. Characterizing the metabentonite and its constituent apatite crystals on the basis of rare earth and other trace elements has allowed two separate outcrops to be correlated locally and the source magma type identified. In addition, these apatite data provide a chemical fingerprint with which to correlate this horizon with similar occurrences elsewhere in northern Europe.
Mineralogy, petrology and microfabric analysis of the Eilrig Shear Zone, Fort Augustus
Authors: Phillips E. R. , Clark G. C. , Smith D. I.
Published: January 2010

Synopsis

Detailed mapping of the area between Loch Lochy and Loch Ness (Scotland), SE of the Great Glen, has identified a 1 to 1.2 km-wide belt of quartz-feldspar-mylonites, garnetiferous phyllonites and relatively undeformed arkosic psammites underlying a sequence of metasediments correlated with the Neoproterozoic Grampian Group. The mylonites and garnet-phyllonites define a previously undescribed major ductile shear zone, here referred to as the Eilrig Shear Zone, which has an approximate strike length of at least 20 km. The shear zone is underlain by a sequence of pebbly arkosic psammites of unknown stratigraphical affinity. Kinematic indicators present within the various mylonitic rocks of the Eilrig Shear Zone yield a consistent NW-directed sense of overthrusting. Initial
P–T
estimates obtained for the garnet-bearing phyllonites indicate that ductile deformation resulting in mylonitization occurred during prograde amphibolite facies metamorphism. It is concluded that the Eilrig Shear Zone represents a major, possibly regional, ductile structure which resulted in the overthrusting of the Grampian Group towards the NW early in the structural history of the area.
Transient and long-term correspondence of erosion level and the tops of granite plutons
Authors: Leake Bernard E. , Cobbing John
Published: January 2010

Synopsis

Granites, used in the sense of granitoids, are characteristically confined to continental crust and the bottoms of granite plutons are rarely exposed. Indeed the roots of a major granite batholith have yet to be unequivocally described as far as we know. In contrast the tops and upper parts of numerous granite plutons have been described as they commonly lie near to the present level of erosion of the continental crust. Some regions have so many exposed tops that it is unlikely to be a chance coincidence of erosion level and granite exposure. Such situations are of two general types (1)
Long Term.
Stabilized crust in which the tops of plutons oscillate about ±3 km of sea-level for hundreds of millions of years e.g. the 400–470 Ma Caledonide plutons of N. Britain and Ireland (2)
Transient.
Unstabilized crust in which relatively young granites form topographically high plutons in which erosion might cut down into some of the plutons within tens of millions of years e.g. the Cretaceous and Tertiary plutons of Peru and the Sierra Nevada, Western USA. At least some of the latter group must eventually pass into the former group possibly by structural lowering e.g. due to crustal extension.

The main control appears to be isostatic stabilization accompanying and following plutonism, combined with the final consolidation of granites in a narrow layer below the prevailing topography because of termination of crystallization by a topographically related water table.
Geophysical investigation of the Blane Valley Pleistocene deposits
Authors: Doody Jonathan J. , Smythe David K. , Watts Doyle R.
Published: January 2010

Synopsis

Shallow geophysical surveys undertaken within the Blane Valley, floored by Loch Lomond Stadial proglacial lake deposits, show that the Pleistocene sequence is significantly thicker than previously suspected. Seismic refraction, resistivity and gravity data demonstrate that the depth to the Upper Old Red Sandstone bedrock varies from 30–100 m, suggesting significant relief on the submerged bedrock surface. The Pleistocene sequence extends to about 80 m below Ordnance Datumn.
New stratigraphical constraints on the Durness Group of NW Scotland
Authors: Nicholas Christopher J.
Published: January 2010

Synopsis

New field observations are combined with strontium isotope and trace element analyses in a stratigraphical investigation of the Durness Group at Balnakeil Bay, NW Scotland. The karst fissures and breccias used by

Palmer
et al.
(1980)

as evidence of a major unconformity between Lower Cambrian (Sailmhor (III) Formation) and overlying Ordovician strata (Sangomore (IV) Formation), are here interpreted as being of Tertiary or Recent age. Similar features are visible at outcrops along the entire coastline in association with modern cemented beach-sand. For the first time in the Palaeozoic, strontium isotope stratigraphy is used to date rocks whose age has remained unresolved by conventional bio- and litho-stratigraphy. All formations at Balnakeil Bay display consistent Lower Ordovician, Middle-Upper Cambrian
87
Sr/
86
Sr ratios when compared with established data for this time interval (

Donnelly
et al
. 1990

;
Keto and Jacobsen 1987
). The
87
Sr/
86
Sr ratios of Lower Toyonian archaeocyaths from Labrador (supported by currently unpublished data for the Tommotian and Atdabanian of Siberia) suggest that Lower Cambrian
87
Sr/
86
Sr seawater ratios were significantly lower than those in the late Middle and Upper Cambrian. The increase in
87
Sr/
86
Sr ratios may correlate with the Toyonian archaeocyath extinctions and mark the beginning of a global regressional event (which reached its maximum during the Late Cambrian). As there is no such excursion present within the Sr isotope curve for Balnakeil Bay, this implies that the upper Eilean Dubh (II) Formation is of Middle Cambrian age or possibly younger.