bluuebunny/crossref_metadata_2025 huggingface dataset:
Caledonian ages for pegmatites from the Glen Urquhart serpentinite-metamorphic complex, Inverness-shire
Authors: Brook M. , Rock N. M. S.
Published: January 2010

Synopsis

A Rb–Sr isochron for biotites from five unfoliated acid pegmatites in the limestones of the Glen Urquhart complex and the surrounding Moine psammitic gneisses has yielded an age of 428 ± 5·Ma (λ
87
Rb = 1·42 × 10
−11
a
−1
), which lies within the range of late Caledonian pegmatite ages reported from elsewhere in the Northern Highlands. It leaves open the possibility that the limestones and kyanite-schists of the complex itself could be Lewisian, Moine, or Dalradian.
Pentameral fossils from the Lower Cambrian Pipe Rock of the North-West Highlands
Authors: Campbell N. A. , Paul C. R. C.
Published: January 2010

Synopsis

Star-shaped pentameral fossils occur commonly on a single bedding surface of the Lower Cambrian Pipe Rock at Allt nan Uamh, south of Inchnadamph. They occur as pure white quartzite fills in a yellow quartzite matrix, but preserve no trace of a body wall. The original shape is believed to have been like a five-lobed ctenophore. Each lobe has a median partition, but no trace of any orifice has been seen. The fossils are interpreted as body fossils. They are not echinoderms despite their consistent pentamery, but we can suggest no other phylum.
On the occurrence of the arctic marine bivalve
Macoma torelli
(Steenstrup) Jensen in the Errol Beds, east Scotland
Authors: Graham D. K.
Published: January 2010

Synopsis

A record, believed to be the first in the British Quaternary, of an occurrence of the arctic bivalve
Macoma torelli
(Steenstrup) Jensen is given, and the environmental significance discussed.
The stratigraphy and structure of the Moine rocks of Eastern Ardgour
Authors: Stoker M. S.
Published: January 2010

Synopsis

The Moine rocks of Eastern Ardgour which mainly belong to the Loch Eil Division are sub-divided into five fault-bounded units, the Cona Glen, Glen Gour, Coire an Iubhair, Inversanda, and An Torran units. Sedimentary structures were used to establish the stratigraphic succession, the lower levels of which may be a transition into Glenfinnan Division rocks. Deformation of the Moine was polyphase and is described in terms of a D
1
–D
4
sequence. The D
1
phase is probably Precambrian in age with D
2
–D
4
structures formed during Caledonian deformation. The Glen Scaddle basic intrusive complex was intruded during the D
1
–D
2
interval.
Geometry of deformation adjacent to the Glencoul thrust at Loch Glencoul, Sutherland
Authors: Maobing Lin
Published: January 2010

Synopsis

The Glencoul thrust at Loch Glencoul is on a ramp zone to which footwall imbricate faults are related. Lewisian rocks in the hanging wall are deformed against this ramp; dykes and the country rock foliation have been rotated into near-parallelism with the thrust plane. The degree of the deformation in the Lewisian gneiss and the dykes increases gradually towards the ramp surface.
The occurrence of possible Late-glacial estuarine deposits at levels above the Carse Clay west of Stirling
Authors: Laxton J. L.
Published: January 2010

Synopsis

Lithological evidence from pits and boreholes, together with limited palaeontological and geomorphological information, indicates the presence of a Late-glacial sea level in excess of 30 m O.D. over a distance of about 17 km west of Stirling. Associated with this former sea-level there is evidence of estuarine deposition in the valley of the River Teith downstream from Doune.

A raised beach feature occurs on the eastern side of the central part of the Menteith Moraine ridge. From this observation, considered with new lithological information on the deposits comprising the ridge and the local occurrence of solid rock near surface, it is suggested that the Menteith Moraine is a composite feature, only part of which is a true moraine associated with the Loch Lomond stadial.
First Jurassic dinosaur footprint from Scotland
Authors: Andrews J. E. , Hudson J. D.
Published: January 2010

Synopsis

A single large cast of a footprint of a dinosaur is reported from the Lealt Shale Formation, Great Estuarine Group, Bathonian, of Trotternish, Skye.
Structural evolution of the Moine thrust belt between Loch More and Glendhu, Sutherland
Authors: Butler Robert W. H.
Published: January 2010

Synopsis

Reinvestigation and new mapping confirm that the area contains a number of large thrust sheets and imbricate slices of Cambrian cover and Lewisian basement but emphasise that they are bounded by an interconnecting network of WNW-directed faults. The network demonstrably propagated, piggy-back fashion, into the foreland since higher structures are cut or bulged up by lower imbricates. These new interpretations require a revision of structural units in the Glendhu area.

The margins of culminations, which resulted from the continual stacking of imbricate slices, are the sites of extensional faulting which locally post-date thrust structures. However, some of the major thrusts in the area have primary extensional geometries in their footwalls and hanging walls since they cut down stratigraphic section towards the foreland. The proposed explanation is that bedding in the foreland Cambrian shelf was dipping gently to the SE, possibly in response to isostatic loading by the emplacement of the
c.
10 km thick Moine thrust sheet. Datum-parallel thrust flats would then cut down stratigraphic section with an extensional sense. Early extensional strains which locally predate imbricate thrusts in those Cambrian quartzites in the immediate footwall to the Moine thrust may reflect a major gravity spreading component in the initial phases of the emplacement of the Moine sheet.

The geometry of thrusts in the Glendhu culmination is illustrated on a balanced cross-section. The hanging wall of the Glencoul thrust, which includes a stack of interthrust Cambrian cover and Lewisian basement termed the Aisinnin imbricates, restores to a width of over 15 km. This can be added to the displacement on the Glencoul and lower thrusts as estimated from the offset of foreland structures, of 25–33 km, to give a total restoration for the footwall of the Moine thrust of at least 40 km.
Disseminated and epigenetic Pb–Zn mineralisation in Ordovician mudstone, Galloway
Authors: Stone P. , Leake R. C.
Published: January 2010

Synopsis

Significant base metal anomalies in drainage and overburden in the Penkiln Burn area, near Newton Stewart, are spatially associated with the outcrop of a sequence of siliceous mudstone, siltstone and chert. Pb is particularly enriched in drainage samples, reaching approximately 1% close to a mineralised gossan zone, mainly in the secondary lead phosphate plumbogummite. Three varieties of mineralisation have been recognised:

Early fine disseminations, chiefly sphalerite and pyrite, in the mudstone and siltstone characterised by Zn levels between 500 and 1000 ppm. Fine stratiform pyrite laminae adjacent to the mineralised horizons and interbedded cherts containing disseminated sphalerite support a probable syngenetic, exhalative origin.

A swarm of dioritic minor intrusions carry disseminated sulphides and have elevated metal contents, most notably Zn (up to 2000 ppm). This mineralisation is considered to have a primary igneous source.

Mineralisation related to veining and alteration involving both the remobilisation of the disseminated sulphides and hydrothermal effects. Thin quartz veinlets containing sphalerite and galena locally elevate base metal levels so that Pb reaches 7000 ppm in places. The veins usually contain some secondary alteration minerals which become dominant at the altered margins of dykes and in fault-bounded gossans where a low temperature mineral assemblage includes plumbogummite and beudantite. In the gossans Pb ranges up to 4.5% but Zn has been preferentially leached.
The systematic geochemical variation between two tectonically separate successions in the southern Monadhliaths, Inverness-shire
Authors: Haselock Paula J.
Published: January 2010

Synopsis

Detailed mapping SE of Fort Augustus has revealed the presence of two distinct successions, lithostratigraphically subdivided into nine formations. The upper Corrieyairack Succession is overlain conformably by the Leven Schists of the Dalradian Supergroup and is in tectonic contact with the lower Glenshirra Succession. Both successions are geochemically distinct from the Lower Dalradian and are considered to be part of the Grampian Division. The two successions are also petrographically and geochemically distinct from each other and these differences are considered to represent variations in the nature of the original sediments. The lower Glenshirra Succession appears to represent a series of arkosic sediments deposited in an oxidising environment whilst the Corrieyairack Succession has affinities closer to greywackes. There are also minor differences in geochemistry between the individual formations, which support the structural and stratigraphic interpretation of the area.
“Eclogite” in the Ballantrae Complex: a garnet-clinopyroxenite segregation in mantle harzburgite?
Authors: Smellie J. L. , Stone P.
Published: January 2010

Synopsis

The well-known occurrence of eclogite within the Ballantrae complex at Knockormal is enigmatic and unique within the paratectonic Caledonides of the British Isles. Although the “outcrop” originally described is demonstrably a large loose block, garnet-pyroxenite uncovered
in situ
in a temporary trench located close by demonstrates the local provenance of such rocks. The pyroxenite contains tschermakitic hornblende, fassaitic clinopyroxene and almandine-rich pyrope, a paragenesis consistent with an origin within the lowermost crust or upper mantle. The mineral chemistry is dissimilar to that of eclogites found in blueschist terrains but compares closely with garnet-pyroxenite found within “Alpine-type” intrusions and as inclusions in kimberlite and alkali-basalt breccia pipes. The lithology is not a true eclogite (
sensu stricto
) but is a garnet (-hornblende)-clinopyroxenite interpreted as a segregation within serpentinised harzburgite, although no field relationships are exposed. The garnet-pyroxenite probably formed by partial melting of a rising lherzolite diapir beneath an Arenig oceanic spreading centre.
The stratigraphy and structure of the Moine rocks of the Loch Eil area, West Inverness-shire
Authors: Strachan R. A.
Published: January 2010

Synopsis

The Moine rocks of the Loch Eil area consist mainly of psammites and quartzites which belong to the Loch Eil division. Sedimentary structures are used to establish a Loch Eil division stratigraphical succession. The Loch Eil division lies in stratigraphical and structural continuity with the underlying pelitic and banded gneisses of the Glenfinnan division. The deformational history of the Moine rocks of the Loch Eil area may be resolved into two phases of recumbent folding (D
1
and D
2
) and three phases of upright folding (D
3
–D
5
). The regional structure is dominated by the interference of D
3
and D
4
fold systems. D
1
, and possibly D
2
also, are considered to be Precambrian in age, whilst D
3
–D
5
are likely to represent the effects of Caledonian reworking.
The petrogenesis of the Tertiary basaltic and intermediate lavas of northeast Ireland
Authors: Lyle P.
Published: January 2010

Synopsis

New trace element results are presented for the Tertiary basaltic and intermediate lavas in Antrim, including REE data available for the first time. The Lower Basalts are characteristically light REE enriched relative to chondritic values, the associated intermediate lavas are substantially enriched with marked negative Eu anomalies and the Upper Basalts are light REE depleted. The Lower Basalts probably formed by low degrees (<10%) of partial melting of a spinel lherzolite mantle with high-level fractionation of mainly olivine and plagioclase to produce the associated intermediate lavas. This mantle source may have been depleted by a previous magmatic episode in Permian times. The Upper Basalts probably result from a second stage fusion of the same mantle source with partial melting greater than 10%. They represent a change to magmas resembling Preshal Mhor type with MORB characteristics and are the final stages of an abortive rifting episode recognized elsewhere in the British Tertiary Volcanic Province.
Agalmatolite and the maturity of sandstones of the Appin and Argyll groups and Eriboll Sandstone
Authors: Russell Michael J. , Allison Iain
Published: January 2010

Synopsis

Agalmatolite is a term used to describe a soft waxy rock amenable to carving composed of massive, felted muscovite with very minor quartz and feldspar. The term is derived from
αγαλμα
meaning sculpture or statue. The occurrence of agalmatolite was recognised, during the initial geological survey of the NW Highlands, as resulting from a “peculiar Precambrian weathering of the Lewisian” which occurs beneath the Cambrian unconformity. We have examined the effects of this weathering on the Lewisian gneisses in a zone of alteration extending two to three metres below the Cambrian unconformity on the west side of Loch Eriboll on the north coast of Scotland. The mafic minerals, a large proportion of feldspar and even some quartz have been altered to a green muscovite in what we take to be a palaeosaprolite resulting from alkaline weathering.

We imagine a loose Precambrian quartz-rich soil being river-borne a short distance to the Dalradian basin or reworked to form the Eriboll Sandstones, a supposition strongly supported by the intermittent development of discontinuous layers of green micaceous shale in the Eriboll Sandstone reminiscent in colour and composition of the agalmatolite. The alumina dissolved from the Lewisian is transported as a colloid or in solution in groundwater to the sea where it reacts with dissolved silica and K
+
, Na
+
or Ba
++
to form huge bodies of authigenic or hydrothermal-sedimentary feldspar now preserved in the Fucoid Beds and in the Middle Dalradian.
Scottish Carboniferous amphibian localities
Authors: Smithson T. R.
Published: January 2010

Synopsis

A catalogue of Carboniferous amphibian localities in Scotland is given. The horizon, matrix lithology and amphibian fauna at each site is recorded, together with a list of the repositories in which the material is housed. The Scottish Carboniferous amphibian fauna is divisible into two discrete assemblages: a Coal Measures assemblage, comprising taxa found elsewhere in the British Coal Measures; and a pre-Coal Measures assemblage restricted to the Midland Valley. The Carboniferous flora and fish fauna appear to partition in a similar way. The boundary between these two assemblages is represented by the Passage Group.
Inter-tidal and sub-tidal organic deposits and sea level changes in the Uists, Outer Hebrides
Authors: Ritchie W.
Published: January 2010

Synopsis

Inter- and sub-tidal organic deposits are widely distributed along the Atlantic coast of the Uists. Two sites, at Pabbay (Sound of Harris) and Borve (Benbecula), include sub-tidal sections and these have been examined in detail. Fifteen other sites are summarised. Radiocarbon dates, pollen and macro remains in the organic layers indicate that sea level was 3 to 5 m lower between 8800 B.P. and 5164 B.P. than at present. The site at Pabbay provides evidence for a time (around 4366 B.P.) of massive sand-blowing onto the coast. Such sand accumulation may be equated with the origin of machair land in this area. All the sites provide evidence of coastal retreat and substantial changes in coastal outline.
Archaean supracrustal rocks from the Lewisian near Stoer, Sutherland
Authors: Cartwright I. , Fitches W. R. , O'Hara M. J. , Barnicoat A. C. , O'Hara S.
Published: January 2010

Synopsis

A previously unreported supracrustal suite, the “Cnoc an t-Sidhean Supracrustals”, together with at least three generations of acid and basic orthogneiss form the Lewisian complex at Stoer. Both supracrustals and orthogneisses underwent Badcallian granulite facies metamorphism and polyphase deformation, including the formation of major Badcallian recumbent folds.
Upper Old Red Sandstone sedimentation in the Buchan oilfield, North Sea
Authors: Richards Philip C.
Published: January 2010

Synopsis

A fining and maturing upwards fluvial sequence of Devonian to Viséan age forms the reservoir section of the Buchan oilfield. An upward transition occurs from mainly bed-transport deposits to bed-transport plus suspension deposits. The lower part of the sequence comprises multi-storey sand bodies deposited in mobile-channel belts and during sheetfloods. The upper part of the sequence is characterised by a greater number of fining-upward cycles, an increase in the amount of fine grained material and an increase in the number of cornstone horizons. It was deposited in a system of channels and associated flood basins, over which waning-flow sheetflood deposition periodically occurred.

The upward change in facies and sedimentation style is interpreted as being due to the combined influences of three processes: a) a rise in sea level that raised river base levels; b) a change in climate and c) a decrease in the sediment supply from the soure area, which was possibly a granitic intrusion to the WNW of the field.
Hydrocarbon source rock potential of the Devonian rocks of the Orcadian Basin
Authors: Marshall J. E. A. , Brown J. F. , Hindmarsh S.
Published: January 2010

Synopsis

Potential hydrocarbon source rocks are evaluated from the Devonian Orcadian Basin (plus a small suite from the Hornelen Basin, Norway) for organic matter richness, type and maturation level. Techniques used include total organic carbon determination, pyrolysis, visual kerogen typing, spore colour and vitrinite reflectance. The sequences of SE Shetland, the Walls Sandstone, Fair Isle and the Hornelen Basin only contain small amounts of organic matter and were probably thermally mature before any significant cover was established and any minor hydrocarbons generated were soon lost. The main development of the Orcadian Basin does contain significant Middle Devonian and minor Lower Devonian hydrocarbon source rocks with oil and gas prone materials which are still in the oil window for the majority of the succession. Speculations are made concerning the possibility of hydrocarbons accumulating from this part of the sequence and prospects include reservoirs in the Upper Old Red Sandstone, Eday Beds, John O'Groats Sandstone, and the Lower Old Red Sandstone although deep ‘weathering’ effects are probably detrimental to preservation. Aeolian beds associated with extensive organic rich units may also be significant. Possible sites for hydrocarbon accumulation are the offshore half graben structures beneath the Moray Firth and in the onshore Devonian sequence. The timing of hydrocarbon generation is thought to be early.
The Scottish paratectonic Caledonides
Authors: Bluck B. J.
Published: January 2010

Synopsis

The southern margin of the Laurasian continent has been destructive or strike-slip from at least 576 Ma to
c.
360 Ma. There may have been a pre- or early Arenig obduction of ophiolite onto it, and this ophiolite now provides the base to the Ordovician part of the Highland Border Complex and could have been responsible for regional metamorphism in Dalradian or related rocks. At
c.
480 Ma there was certainly final obduction of the Ballantrae Complex, which formed in an oceanic setting some distance south of its present location. This ophiolite was initially obducted over olistostromes and formed the basement to a later fore-arc basin, the proximal part of which is now exposed at Girvan. The Midland Valley, a Palaeozoic plutonic—volcanic arc, founded on a metamorphic basement, supplied sediments to the fore-arc—accretionary prism on its southern margin. This metamorphic basement is unlikely to have been of local Dalradian type.

Growth of the paratectonic zone involved thrusting and probably strike-slip accretion of possibly 6 terranes. Ophiolites and the accretionary prism of the Southern Uplands were thrust NW onto Midland Valley basement. The whole of the paratectonic zone was initially juxtaposed against the Moine—Dalradian terrane by either strike-slip or thrust movements, but the latest interaction between the Midland Valley and Dalradian terranes involved thrusting. Future investigations into the timing and extent of thrust and strike-slip activity will greatly increase our understanding of continental growth in this region.
Some comments on sedimentary basin development in the Northern North Sea
Authors: Beach Alastair
Published: January 2010

Synopsis

A discussion of some of the problems concerning the structural development of sedimentary basins in the Northern North Sea is made. The Basin and Range Province, often used as an example for the geometry of extensional basins, may not be a good parallel for the Mesozoic North Sea basins, but may be appropriate for the Devonian basins. The Devonian basins originated during the extensional collapse of thickened Caledonian crust to a more normal thickness, a period of crustal restoration. In contrast, Mesozoic basins developed during a period of crustal attenuation, where normal crust was extensively modified to a variably thinned crust. Mesozoic basins cross some of the major Caledonian tectonic elements and may have been built on a Devonian basin architecture. During the Mesozoic, there are significant departures from the subsidence vs. stretching relation predicted by models for extensional basins, and a system of linked tectonics and detachments is invoked. The Northern North Sea forms the northern corner of the NW European block which deformed during the Mesozoic within the boundaries defined by the Tornquist, Biscay and Rockall–Faeroes fault systems. A semi-quantitative displacement vector diagram for the Northern North Sea within this block is presented.
The evolution of the Scottish mineral sub-province
Authors: Russell M. J.
Published: January 2010

Synopsis

The Lewisian rocks, or their equivalents to the northwest, were the ultimate source of most of the elements featuring in economic concentrations of industrial or metalliferous minerals in Scotland northwest of a line running through Loch Tay. Processes of derivation and concentration of these elements were: 1) mechanical weathering, particularly of the potassium-rich Laxfordian, to give the Moinian sub-arkoses and semipelites which were later attacked by convecting waters to release Ba, Pb, Zn and Ag for ore deposition in the Middle Dalradian (e.g. the sedimentary ores of Aberfeldy), 2) alkaline chemical weathering to produce smectite and illite bearing palaeosoils on the Lewisian; weathering which also released groundwaters rich in K, Al and Si for aluminosilicate formation by ‘reverse weathering’ in the seas around the Proterozoic-Phanerozoic boundary (e.g. K-feldspar in the Fucoid beds, Ba-feldspar at Aberfeldy and muscovite in the Dalradian), 3) direct partial melting to contribute molybdenum and minor gold to Caledonian granitoids.

Mantle contributions to the crust, partly revealed by the Sm/Nd studies of O'Nions
et al.
(1983) and Halliday (1984) added Cr, Ni, Cu and Au to the Dalradian during rifting. Ba, Pb, Zn, Ag, Au, Pt, As and Sb were added during subduction and accretion of the Iapetus ocean floor and sediments in the Lower Palaeozoic. Certain associations of these elements were remobilized during the later stages of Caledonian magmatism (e.g. Cu and Au). Leaching of these source rocks also took place during early and late Carboniferous rifting when hydrothermal solutions produced the Pb + Zn veins at Leadhills and the Ag + Co + Cu + BaSO
4
mineralization in the Ochils respectively. Chemical weathering, particularly of the early Carboniferous basaltic pile in the reducing and acidic conditions of the Middle Carboniferous led to the generation of clay band ironstones and bauxitic clays.
Oil exploration and production in Scotland
Authors: Hallett D. , Durant G. P. , Farrow G. E.
Published: January 2010

Synopsis

The oil industry in Scotland spans a period of 136 years from James Young's patent on extracting oil from cannel coal, to the attainment of oil production from the North Sea of 2.6 million barrels per day. Subsequent to the First World War a campaign of onshore oil exploration began in Scotland, which is still in progress today. Operations in offshore Scottish waters have now been in progress for almost 20 years, and activity in 1984 was at a record level. The development of this industry has been subject to constraints in three main areas: technology, economics and legislation. The interaction of these three elements is examined in relation to both onshore and offshore exploration.
A late-Devensian pollen site in Cowal, south-west Scotland
Authors: Tipping Richard
Published: January 2010

Synopsis

A thick sequence of clays and gyttja sediments from a valley in the north-west of the Cowal Peninsula is shown on palynological grounds to be of Late-Devensian (Loch Lomond Stadial) and early Flandrian age. The Stadial depositional environment is considered by comparison with varved glacial sediments in other regions to be glaciolacustrine in origin. Correlation of the basal part of this sequence with a prominent terminal moraine of probable Loch Lomond Stadial age leads to the proposal that Stadial glacial activity in the Cowal Peninsula was considerably greater than is at present recognized.
Provenance and setting of some Ordovician and Silurian conglomerates in Northern Ireland
Authors: Simon J. B.
Published: January 2010

Synopsis

The marine Caradoc–Llandovery deposits of the Pomeroy and Lisbellaw inliers in counties Tyrone and Fermanagh, which accumulated in a basin that deepened southwards towards the Longford–Down accretionary prism, contain rare conglomerates of predominantly vein quartz, quartzite and undeformed igneous clasts. These rocks have a similar setting and dispersal to the Llanvirn–Wenlock deposits of the Girvan area of Scotland, and in Ireland it is likely that coarse grained debris was also derived from pre-Dalradian metamorphic basement and an island arc complex to the north. It is possible, though not certain, that this source area is represented by Ordovician igneous rocks and metasediments of the Tyrone Igneous Complex.
An explanation for lycopod configuration, ‘Fossil Grove’ Victoria Park, Glasgow
Authors: Gastaldo Robert A.
Published: January 2010

Synopsis

The ‘Fossil Grove’, Glasgow, is the only site of
in situ
Carboniferousaged plants that have been curated for future generations to study. A model is proposed based upon sedimentological and preservational aspects that explains the debated origin of the distorted configuration of the tree bases. Uniform distortion of the stumps in a NE–SW direction is believed to have resulted from the influx of the moulding sand at high velocity into a partially decayed stand of trees. This is evidenced by the southwestward paleocurrent direction deduced from ripple marks and transported plant detritus in the uppermost horizons of the sand body. Subsequent casting by continued influx of sand preserved the stand in its ‘streamlined’ configuration. Regional tectonism is not considered responsible for the slightly elongated condition of the preserved ‘Fossil Grove’ as proposed by previous authors.
Fossil
Lithothamnium
(calcareous algae) rhodoliths from Late Quaternary raised coastal sediments, Irvine, Ayrshire
Authors: Boyd W. E.
Published: January 2010

Synopsis

Fossil
Lithothamnium
(calcareous algae) rhodoliths occurring in early Flandrian raised coastal deposits near Irvine, Ayrshire, are described, and their growth characteristics are analysed. The analysis indicates that much of the
Lithothamnium
was derived, probably from several nearby localities within the early Flandrian bay. Comparison of the
Lithothamnium
-bearing and associated sediments with sedimentary facies models developed from the study of modern
Lithothamnium
by Bosence (
Geol. J.,
15
, 91–111; 1980) provides discussion regarding the palaeoenvironmental conditions at this locality during early Flandrian times.
K–Ar systematics in Tertiary dolerites from West Connacht, Ireland
Authors: Mitchell John G. , Mohr Paul
Published: January 2010

Synopsis

Thirty-four new K–Ar ages from West Connacht Paleocene dolerites reveal a systematic pattern of argon loss across the province. Four possible causes for this pattern are examined: thermal overprinting, nature of countryrock, depth of emplacement, and degree of microfracturing. Although some clear relationships emerge, no single cause can explain all the observed apparent ages. Nevertheless, the value of conventional K–Ar dating, as a supplement to
40
Ar/
39
Ar dating, is emphasised as a means to obtaining regional geological insight into igneous provinces.
Tectonostratigraphy of the Southern Belt of the Southern Uplands
Authors: Kemp Alan E. S.
Published: January 2010

Synopsis

A revised stratigraphy is proposed for the Southern Belt of the Southern Uplands. The Southern Belt (Riccarton Group) comprises all rocks of Wenlock age and is divided into two formations — the Ross Formation and the Raeberry Castle Formation which can be recognised throughout the Southern Uplands. The Ross Formation of
Cyrtograptus centrifugus
to lower
Monograptus riccartonensis
Zone age comprises mainly classical turbidites and is everywhere tectonically fragmented/highly imbricated. The Raeberry Castle Formation of upper
M. riccartonensis
to
C. lundgreni
Zone age comprises diverse turbidite facies associations including channelised conglomerates containing limestone boulders and in the Kirkcudbright area comprises three fault-bounded, but internally coherent, units. The high quality of new biostratigraphic data obtained permits correlation of turbidite sequences across major strike faults between separate tectonic units for the first time in the Southern Uplands. The principal tectonic units identified probably correspond to packets of trench sediment which were sequentially accreted to the northwest margin of Iapetus during subduction during the mid-Silurian.
Loch Lomond Advance glaciers in Assynt, Sutherland, and their palaeoclimatic implications
Authors: Lawson T. J.
Published: January 2010

Synopsis

Evidence for the limits of seven glaciers that formed in the Assynt area during the Loch Lomond Stadial is presented. Palaeoclimatic inferences based on reconstructions of these former glaciers support the view that the principle snow-bearing winds came from the south, and that glacial accumulation was aided by snow blown onto glacier surfaces by south-westerly and possibly north-westerly winds. One former glacier near Stronchrubie occupies an anomalously low position with an unfavourable aspect. A large potential snow-collecting area to the south and west, from which snow may have been redistributed by such winds, is suggested as the reason for the existence of this glacier.
The seismic expression of a low angle detachment (sole fault) from the Beryl Embayment, central Viking Graben
Authors: Swallow John L.
Published: January 2010

Synopsis

The interpretation of commercial multichannel seismic reflection data shows that the Beryl Embayment is bounded by a major listric fault (Beryl Embayment Fault) which passes into a gently dipping detachment zone (sole fault) beneath the Bruce oil-field structure. Therefore, the existence of a low-angle detachment, within the northern North Sea, is confirmed by ‘direct’ observation and not simply predicted by the construction of balanced cross-sections. Post-Triassic extension within the northern part of the Beryl
Embayment
is approximately 25%.
Alluvial fans and an outwash fan in upper Glen Roy, Lochaber
Authors: Peacock J. D.
Published: January 2010

Synopsis

Mapping in upper Glen Roy suggests that, contrary to recent opinion, the Turret outwash fan and a few of the alluvial fans are largely subaerial in origin. It is proposed that the outwash fan was formed at a late stage in the retreat of ice from the Late Devensian maximum. The alluvial fans seem to have been laid down chiefly in the interval between deglaciation and the flooding of upper Glen Roy by the lakes associated with the Parallel Roads.
Shoreface storm deposits in the Rannoch Formation (Middle Jurassic), North West Hutton oilfield
Authors: Richards Philip C. , Brown Stewart
Published: January 2010

Synopsis

The Rannoch Formation of the NW Hutton oilfield is interpreted as a marine offshore to shoreface, storm-wave influenced deposit.

Four facies are recognised in drill cores: 1) heterolithic beds; 2) laminated and hummocky cross stratified (HCS) micacaeous sandstone; 3) indistinctly laminated micaceous sandstone; and 4) structureless sandstone. Facies 1 is interpreted as an offshore to shoreface transition deposit with thin storm-emplaced sandstone beds. The remaining facies represent the products of shoreface deposition under storm conditions of varying severity. Associated bioturbated sandstones represent periods of fair weather reworking.

The Rannoch Formation in the NW Hutton area is typical of the formation elsewhere in the UK northern North Sea and is therefore interpreted as a widespread, storm-dominated, offshore to shoreface regressive sequence.
Stratabound mineralisation in Dalradian rocks near Tyndrum, Perthshire
Authors: Fortey N. J. , Smith C. G.
Published: January 2010

Synopsis

Two horizons of low-grade stratabound sulphide mineralisation occur east of Tyndrum in the Ben Challum Quartzite, a newly recognised formation in the Argyll Group (Middle Dalradian). The lower horizon exceeds 9 km along strike and averages 1250 ppm Zn and 340 ppm Cu over an 80 m intersection. The upper extends for 4 km and locally contains up to 3.6% Zn over 1 m. Both comprise stratiform pyrite with minor pyrrhotite, sphalerite and chalcopyrite, in quartzite with possible meta-chert and subordinate schists, and contain manganese-enriched garnet. Sphalerite and galena in the upper horizon are associated with microcrystalline quartz and siliceous breccia interpreted as relict hydrothermal rocks. The Ben Challum Quartzite is in part highly albitic and includes bands of hornblende-schist with tholeiitic composition, some of which probably formed as basic tuff or volcanic sediment. The basal part of the overlying Ben Lui Schist includes sediment carrying talc, magnesite, chromite and Ni-sulphides which probably derived from altered ultramafic rocks. The Zn–Cu–Pb mineralisation is considered to be of the sedimentary-exhalative type, deposition occurring during a regime of fault-bounded subsidence prior to the turbiditic sedimentation of the Ben Lui Schist.
On the origin and stability of remanence and the magnetic fabric of the Torridonian Red Beds, NW Scotland
Authors: Torsvik T. H. , Sturt B. A.
Published: January 2010

Synopsis

Primary (compactional) magnetic fabrics and multicomponent remanences are recognized in the Stoer and Torridon Groups. Low temperature (LT) blocking remanences are randomized around 400–600°C and relate to a post-Torridonian magnetic overprint, possibly of early Mesozoic age. In the Stoer Group (and some Stoer boulders in the basal Torridon Group) LT remanences are partly or fully carried by magnetite (titanomagnetite). High temperature (HT) remanences are characterized by discrete unblocking above 600°C, having a specular haematite remanence carrier. Results of a conglomerate test of some Stoer boulders provides a positive stability test for HT remanences in the Torridon Group, and a convergence of evidence suggests that remanence acquisition of both the Stoer and Torridon Groups was facilitated by both detrital and early diagenetic processes. A fold test of the Stoer boulders (inclination data) indicates that the boulders have preserved a primary HT remanence. Secondary fabric is readily observed in the boulders, hence, HT remanences most likely reside in different grain- or mineral fractions than the bulk susceptibility.

The overall palaeomagnetic data (HT remanences), indicates that the angular unconformity, separating the Stoer and Torridon Groups, represents a considerable period of time. Palaeomagnetic results from the underlying Lewisian basement have traditionally been interpreted in terms of post-orogenic uplift associated with the Laxfordian event (
c.
1800–1400 Ma). Due to an apparent polar fit between Lewisian and Stoer Group data, we address the question as to the significance of post-Laxfordian magnetic overprinting in the Lewisian Complex.
The derivation, biostratigraphy and palaeobiogeographic significance of corals from Silurian deep-sea turbidite facies in the south-west Southern Uplands
Authors: Scrutton Colin T. , McCurry John A.
Published: January 2010

Synopsis

Two new records are described and one previous record reviewed of isolated coral colonies from Llandovery turbidites in the south-west Southern Uplands. Criteria allowing the distinction between modes of origin of such specimens by floatation, bedload transportation and/or reworking are discussed. Two of the specimens, the tabulate corals
Propora exigua
and
P. edwardsi,
are interpreted as derived from contemporaneous shelf environments and transported by floatation and sinking to their points of interment. The third, a rugose coral
Ceriaster
sp., was probably transported in the same way initially, but may have reached its final locus of deposition as part of a turbidite bedload. All three corals are of biostratigraphic or palaeobiogeographic interest.
Propora exigua
is characteristic of the Telychian whilst
P. edwardsi sensu stricto
has only been recorded previously from earlier Llandovery rocks near Girvan. The geographical range of the genus
Ceriaster
was hitherto restricted to Asia.
Upper Ordovician graptolites from the
D. complanatus
Zone of the Moffat and Girvan districts and their significance for correlation
Authors: Williams S. Henry
Published: January 2010

Synopsis

At its type development at Dob's Linn, southern Scotland, the
Dicellograptus complanatus
Zone is represented by two thin black shale bands some 9 m above the base of the Upper Hartfell Shale Formation. Contrary to previous reports, the fauna is moderately diverse with an assemblage including
Dicellograptus complanatus
Lapworth,
D. minor
Toghill,
Climacograptus miserabilis
Elles and Wood,
C. tubuliferus
Lapworth,
Orthograptus socialis
(Lapworth),
Orthoretiolites
?
pulcherrimus
(Keble and Harris) and
Plegmatograptus
? sp. indet. At Girvan the
D. complanatus
Zone is contained within the Mill Formation of the Upper Whitehouse Group and the lower part of the Shalloch Formation. The basal Mill Formation yields a still more diverse low
D. complanatus
Zone fauna, with the addition of
Dicellograptus alector
Carter? (? =
D. gravis
Keble and Harris),
D.
cf.
minor
Toghill,
Orthograptus
cf.
calcaratus
(Lapworth) and
Glyptograptus
? cf.
occidentalis
Ruedemann. The
D. complanatus
Zone correlates with the
D gravis
(Ea4) and
C. uncinatus
(Bol) zones of Australia, and probably with the
C. pygmaeus
and
C. manitoulinensis
zones of north-eastern North America.
A reassessment of the probable Loch Lomond Stade marine molluscan fauna at Garvel Park, Greenock
Authors: Peacock J. D.
Published: January 2010

Synopsis

Examination of the published records and museum specimens of the mollusca from Scott and Steel's (1883) Late-glacial ‘arctic bed’ locality at Garvel Park, Greenock, confirms the cold water aspect of the fauna and suggests that it can be compared with that of shallow water communities in mid- to high-arctic regions today. It also supports the view that oceanic waters on the coast of western Scotland were arctic for at least part of the Loch Lomond interval. Four species are added to the faunal list, of which
Buccinum terraenovae
Beck and
Nicania striata
Leach are new to the Scottish Late-glacial marine fauna.
The metamorphic rocks of the Scaraben area, East Sutherland and Caithness
Authors: Strachan Robin A.
Published: January 2010

Synopsis

The Scaraben area contains a continuous sequence of metasediments which include psammites and semi-pelites, of undoubted Moine affinities, and the Scaraben Quartzite which several workers have assigned to the Dalradian. These metasediments have undergone a common tectono-metamorphic history, involving four phases of deformation (D1–D4) and associated amphibolite-facies metamorphism. Four different phases of granite intrusion have been identified. The Scaraben Quartzite is assigned to the ‘old Moine’ of the Northern Highlands: there is no evidence that it is an outlier of the Dalradian NW of the Great Glen Fault.
The concealed coalfield at Canonbie: an interpretation based on boreholes and seismic surveys
Authors: Picken G. S.
Published: January 2010

Synopsis

A concealed coalfield at Canonbie has long been considered likely. Recent work, in conjunction with provings made in the 1950s, has shown the coalfield to exist and to be larger than most early workers envisaged. The structure of the coal bearing Carboniferous rocks is complicated, but concealed by the relatively undisturbed beds of the unconformably overlying New Red Sandstone. Although the limits to the coalfield have not yet been established, the work to date has shown there to be sufficient coal to consider the possibility of a major mining operation at some time in the future.
Magmatic and metasomatic differentiation in the petrogenesis of Archaean metabasites from Tigharry, North Uist
Authors: Williams Patrick J.
Published: January 2010

Synopsis

The polymetamorphic supracrustal sequence at Tigharry, North Uist is associated with amphibolites, garnet–amphibolites, biotite–amphibolites, cummingtonite–garnet amphibolites, actinolitic hornblende–chlorite rocks and dolomite–actinolite–anthophyllite–chlorite rocks. These are a cogenetic group of tholeiitic basic and ultrabasic rocks belonging to the Archaean “banded basic” suite of the Lewisian complex in the Outer Hebrides. Diverse metabasite assemblages and cryptic variations of mineral composition are controlled by strong, predominantly magmatic chemical differentiation and the geochemistry is very similar to that of layered ultramafic/gabbro bodies of the mainland Lewisian complex. Volumetrically less important anthophyllite/gedrite–andesine–kyanite–phlogopite–quartz rocks and hornblende–anthophyllite–garnet–labradorite–staurolite–quartz rocks which have been described previously as metasediments are texturally and compositionally members of the basic/ultrabasic suite. The chemistry of these orthoamphibole-bearing rocks is not purely magmatic and reflects metasomatism (essentially Ca-depletion) of basic material either before or during metamorphism. Chlorite and biotite-rich assemblages including some with large garnets may also be of partially metasomatic derivation. The prograde assemblages of the basic rocks equilibrated during Proterozoic (Laxfordian) metamorphism under P–T conditions of 600–650°C and 6–9 kb. The associated metapelitic rocks contain kyanite and compositionally heterogeneous garnets whose complex zoning and inclusion fabrics may reflect growth during both the Laxfordian and Scourian metamorphic cycles.
A chloritoid-bearing paragenesis in the Macduff Slates of Central Buchan
Authors: Leslie A. G.
Published: January 2010

Synopsis

Chloritoid has been identified in the Macduff Slates immediately to the north of the Insch ‘Younger Basic’ mass, Aberdeenshire, where the mineral forms during the post-F
2
/pre-F
3
episode of Buchan regional metamorphic recrystallisation. Host rock composition is the principal control over the occurrence of the relatively pressure insensitive chloritoid-bearing assemblage (chloritoid–chlorite–phengitic muscovite–quartz–opaques) in a low pressure (P of the order of 3 kb) facies series for these rocks.
Methane-related Mg-calcite cements in recent tidal flat sediments from the Firth of Forth
Authors: Andrews J. E.
Published: January 2010

Synopsis

Recent, intertidal, medium-coarse grained silts from the Firth of Forth have been partially cemented. This cementation is selective, restricted to planar-horizontal crusts and thalassinid burrow fills. Stained thin sections and XRD show that the cement is composed of sub-micron sized, non-ferroan calcite containing 12–14 mole% MgCO
3
. Stable carbon and oxygen isotope analyses of the cements give a mean δ
18
O of 0.57‰ PDB and a mean δ
13
C of −29.8‰ PDB. The δ
18
O value is consistent with precipitation of Mg-calcite from seawater at a temperature around 9.5°C diluted by about 17% with meteoric water. The δ
13
C value is not indicative of normal marine bicarbonate, or derivation from microbial sulphate reduction and is diagnostic of methane oxidation. Methane is inferred to have formed below the sulphate reduction zone by biogenic reactions. Methane migrating upwards in the pore waters was oxidised by anaerobic bacteria near the base of the sulphate reduction zone. An increase in pore water alkalinity accompanied methane oxidation, resulting in the precipitation of CaCO
3
. Preferential cementation of thalassinid burrows suggests that this silt was permeable, acting as a conduit for sulphate-rich pore water to diffuse into the fermentation zone, and a site for bacterial methane oxidation. Projection of the cemented silts above the present tidal flat surface shows that they are now being exhumed, but it is not certain whether cementation is still occurring deeper within the sediment.
Pleistocene ice-proximal glaciomarine sediments in boreholes from the Hebrides Shelf and Wyville-Thomson Ridge, NW UK Continental Shelf
Authors: Stoker M. S.
Published: January 2010

Synopsis

Pleistocene sediments recovered in boreholes from the Hebrides Shelf and Wyville–Thomson Ridge indicate ice-proximal glaciomarine deposition in an outer shelf setting. The sediments are predominantly diamicts and in vertical profile display a general upward-fining trend. The lower part of the succession is characterised by a coarse, crudely stratified-to-massive, clast and matrix-supported diamict assemblage which is interpreted as an amalgamated sequence of debris flows. The upper part consists of finer, massive, matrix-supported diamicts deposited mainly from suspension but with a subsidiary input of ice-rafted material. Thin interbedded lag gravels and sandy sediment gravity flows form a minor component of the succession. This kind of succession is usually associated with a stationary or slowly retreating tidewater ice margin. The morphology of the outer shelf is characterised by a relict glaciated terrain; the sedimentary succession suggests that this is of submarine origin. These data indicate that at some time during the Pleistocene an ice-sheet extended out to the edge of the northern Hebrides Shelf and partly onto the Wyville-Thomson Ridge. The age of this glaciation is unknown but probably pre-dates the last Scottish ice-sheet (Late Devensian/Late Weichselian)
Radiocarbon ages for a glaciomarine bed associated with the maximum of the Loch Lomond Readvance in west Benderloch, Argyll
Authors: Peacock J. D. , Harkness D. D. , Housley R. A. , Little J. A. , Paul M. A.
Published: January 2010

Synopsis

Radiocarbon ages on shells of the high arctic marine mollusc
Portlandia arctica
collected from a glaciomarine bed immediately within the terminal position of the former Loch Lomond Readvance Creran glacier and probably overridden by it suggest that its maximum extent was reached during the second half (10 500–10 000 B.P.) of the Loch Lomond stade period and possibly as late as 10 000 B.P. Arctic marine faunas which flourished in the vicinity of this tidewater glacier and the glacier of similar age which occupied Loch Lomond may likewise date from late in the Loch Lomond stade.