bluuebunny/crossref_metadata_2025 huggingface dataset:
Trend-surface analysis of stratigraphic thickness data from some Namurian rocks east of Stirling, Scotland
Authors: Read W. A. , Merriam D. F.
Published: January 2010

Synopsis

Borehole data for part of the Namurian (E
1
Zone) east of Stirling show that a single thick bed of shale, known as the Black Metals, passes shorewards into a dominantly sandy succession. Trend analysis of these data has revealed features not previously recognised in an earlier study. These features include: (1) a rather abrupt transition between a shelf-like area near Stirling and the differentially subsiding Kincardine Basin to the east, and (2) a tongue of sand that extends south-westwards from Saline and corresponds to one of the axes of maximum subsidence.
Dumbarton Rock
Authors: Whyte F.
Published: January 2010

Synopsis

A study of the attitude of columnar joints in the Dumbarton Rock basalt suggests that the plug is narrowing downwards and could represent an infilled crater.

At a late stage in the volcano’s history, before the emplacement of the plug, subsidence took place along fractures developed around the crater. The narrow strip of pyroclastic rocks and sediments exposed along the north-west shore represents part of this subsided mass.

Chemical analyses of the contact basalt show increasing MgO and H
2
O and decreasing CaO towards the contact. It is thought that the albitised and chloritised contact basalt is due to migration of volatiles towards these contacts.
Nature and origin of Lewisian basic rocks of Gairloch, Ross-shire
Authors: Park R. Graham
Published: January 2010

Synopsis

A series of basic sheets in the Lewisian complex of the Gairloch area was emplaced prior to the main tectonic phase (1400+m.y.) and metamorphosed in epidote-amphibolite facies. Several different modes of origin have previously been proposed for the various members of this suite, but most of the thinner bodies had been assumed to represent metamorphosed Scourie dolerite dykes although there was no evidence that they were of igneous origin.

The suite is divided into eight types based mainly on macroscopic differences in texture and on the presence or absence of metasediment interlayers, but it is concluded that the marked textural variation is due largely to structural and metamorphic differences rather than to original heterogeneity.

Petrographic data are given, and major and trace-element analyses, with modes and catanorms, presented for nineteen representative samples. It is suggested that in certain cases small changes in composition may have occurred through alkali metasomatism.

A comparison of chemical variation trends with the igneous trends of the Karroo dolerites points to an igneous origin for the Gairloch basites which appear to represent tholeiites and olivine-tholeiites. The thicker bodies are either sills or lavas and the thinner bodies dykes or sills.
On the possible occurrence of Dalradian rocks in the Southern Uplands of Scotland
Authors: Shiells K. A. G. , Dearman W. R.
Published: January 2010

Synopsis

A structural profile has been constructed across the eastern end of the Southern Uplands. Three areas of distinct structural style are recognised. Two of these areas illustrate structures which can be identified with the end-Silurian orogeny; the third area, comprising the Coldingham nappe, shows evidence of two periods of orogenic deformation, one of which pre-dates the end-Silurian orogeny. The stratigraphical implications of this early deformation are considered, bearing in mind the importance of the position of the Southern Upland region between the Highlands to the north and the remainder of the Caledonide fold-belt to the south.
An ice-wedge and associated phenomena in the Lower Limestone Series of Fife
Authors: McManus John
Published: January 2010

Synopsis

A previously unrecorded ice-wedge structure in the carbonaceous shales above the Charlestown Main Limestone at Cults, Fife, is described. Associated fracturing and distortion of the bedding are ascribed to an origin during Pleistocene periglacial conditions. Intense fracturing of the uppermost 5 metres of the shales suggests that the active layer penetrated to this depth for some time, its base being marked by sub-horizontal breaks.
Hugh Miller’s Reptile Bed and the Mytilus Shales, Middle Jurassic, Isle of Eigg, Scotland
Authors: Hudson J. D.
Published: January 2010

Synopsis

The type locality of the Mytilus Shales, the lowest division of the Great Estuarine Series on the Isle of Eigg, is described. A map of the exposures is presented, and the detailed stratigraphy of the beds, which include a bed rich in reptilian bones discovered by Hugh Miller, is expounded for the first time. The outcrop is disturbed by small faults and intrusions and partially obscured, so that the succession has to be constructed from five partial sections. The invertebrate faunas, mainly of brackish-water mollusca, are listed. The Reptile Bed itself, a sideritic shelly limestone, is described in detail. Recent work by others on the reptiles, mainly plesiosaurs, is referred to. The conditions of deposition of the Mytilus Shales and especially of the Reptile Bed are considered and analogies are drawn with the bays of the Florida Everglades.
The Lewisian geology of the area between Loch Shieldaig and Loch Bràigh Horrisdale, Gairloch, Ross-shire
Authors: Ghaly Tharwat S.
Published: January 2010

Synopsis

The Lewisian rocks between Loch Shieldaig and Loch Bràigh Horrisdale consist mainly of acid gneisses, hornblende schists, metadolerites and pegmatites together with quartzo-felspathic and hornblendic segregation veins, lenses and pods. The structural deformation is shown to have occurred in three phases. The dominant foliation and lineation are the result of deformation during the main phase, the N.W.-S.E. trend of the lithological banding and the present lineation pattern are the result of mid phase deformation, while the open folds, which affect both banding and foliation, are the products of late phase deformation.

The acid gneiss/hornblende schist banded sequence is considered to have been derived from a concordant sequence of sediments and basic masses during main phase metamorphism and felspathisation. Emplacement of basic dykes took place after the mid phase deformation, and the pegmatites were developed by an extension of the felspathisation processes.
Dalradian-?Arenig relations in parts of the Highland Border, Scotland, and their significance in the chronology of the Caledonian orogeny
Authors: Johnson M. R. W. , Harris A. L.
Published: January 2010

Synopsis

Comparisons of structures in the Jasper and Green Rocks (J.G.R.) (?Arenig) and Dalradian exposed in the River North Esk, near Edzell, lead to the following correlations which are presented in conjunction with the possibly equivalent events in the Central Highland regional history.

N
orth
E
sk

Central Highlands Regional History

J. and G. Rocks

Dalradian

Near-isoclinal folds with flow cleavage
Near-isoclinal folds with flow cleavageGrowth of biotite porphyroblasts

F
1
(Tay Nappe, Aberfoyle anticline) Climax of regional metamorphism

Tight folds with axial planar strain-slip cleavage
Tight folds with axial planar strain-slip cleavage

F
3
(Ben Ledi antiform, [‘downbend’], Cowal antiform)

Two sets of corrugations and kink bands
Two sets of open folds and crenulations

F
4
etc.

These correlations are supported by evidence that the ?Arenig in Arran is downward facing.
Variations within a Scottish Lower Carboniferous lava flow
Authors: MacDonald J. G.
Published: January 2010

Synopsis

Systematic vertical gradational variations within a ‘hawaiite’ lava flow of Calciferous Sandstone age are investigated. The variations include an increase in the amount of augite, and in the size and anorthite content of plagioclase microphenocrysts upwards through the flow. There are corresponding variations in the chemical composition, particularly in CaO and systematic variations in the oxidation state. It is concluded that the major variations could not have resulted from post-eruptive processes and hence the flow must have been erupted in a differentiated condition. It is thought that the differentiation is most probably the result of selective fusion rather than crystal fractionation and that this mechanism could also explain the variations in the suite to which the differentiated flow belongs.
The New Red Sandstone of Raasay and Scalpay, Inner Hebrides
Authors: Bruck P. M. , Dedman R. E. , Wilson R. C. L.
Published: January 2010

Synopsis

The New Red Sandstone of Raasay and Scalpay contains a series of polymictic conglomerates, greywackes and cornstones between 250 and 300 ft thick. At Rudha na’ Leac, on Raasay, these lithologies are arranged in four distinctive units, each of which shows fining-upwards and contains a sequence of

(3) a carbonate horizon (cornstone);

(2) fine- to medium-grained greywackes;

(1) conglomerates and/or coarse-grained greywackes.

The coarser sediments decrease in importance in the upper parts of this sequence, but form a large part of the successions at Eyre (southern Raasay) and on Scalpay.

The structure (especially large-scale trough cross-stratification) and content of the coarse sediments, and the similarity between the carbonate horizons described here and those of modern soils suggest deposition in an alluvial fan environment. These rocks are overlain by the Marine Broadford Beds, the base of which is Hettangian in age (
angulata
zone). Their stratigraphic position and lithology is similar to the basal Mesozoic of Sweden in which continental facies continue into the Sinemurian.
Torridonian sediments at Enard Bay, Ross-shire
Authors: Gracie A. J. , Stewart A. D.
Published: January 2010

Synopsis

Two cycles of sedimentation are present in these Precambrian strata. First cycle sediments were lithified and tilted 25–30 degrees to the west before those of the second cycle were deposited.

The first cycle begins with a thin mantle of massive, unsorted gneiss breccia (I) deposited on a hilly, unweathered surface of Lewisian gneiss. Then follow tabular-bedded breccias and red sandstones (IIa) grading upwards and laterally into red mudstone (IIc). A brown mudflow about 32 m thick, containing accretionary lapilli, is intercalated (IIb). These sediments probably margined a sea or lake. Fades IIc is erosively overlain by large-scale planar cross-bedded, medium to coarse-grained red sandstones (III), perhaps of fluvial origin.

Sediments of the second cycle rest on an irregular unconformity cutting both gneiss and first cycle sediments. Tabular-bedded, (locally massive) breccias, containing gneiss, sandstone and breccia clasts (IVa), pass upwards and laterally into red and grey flaggy sandstones and siltstones (IVb). Facies IV originated like facies II. It is erosively overlain by the fluvial trough cross-bedded pebbly red arkoses (V) of the Applecross Formation.

Facies I–IV probably belong to the Geological Survey’s Diabaig Formation. It follows that the ‘Diabaig’ (and the Torridonian) have not the stratigraphic unity implied by the existing nomenclature.
Sedimentology and palaeogeographic significance of certain red limestones and associated beds in the Lias of the Alpine region
Authors: Hallam A.
Published: January 2010

Synopsis

A stratigraphical and petrological description is given of a selected number of red limestones and associated grey limestones and red and grey-green marls, in several classic localities in the Lias of the Alpine region. These include the Ammonitico Rosso of southern Switzerland and northern Italy and the Adnet Limestone and Fleckenmergel, etc. of the Salzburg Province of Austria.

There are a number of characteristics of these rocks which contrast with those of equivalent age in north-west Europe. Detrital quartz, organic carbon, pyrite, kaolinite, chamosite and siderite are all rare or absent, whereas they are common in the latter region. Chert nodules are, in contrast quite common in the Alpine beds but rare further north. Red limestones and marls are stratigraphically more condensed and more nodular than their grey equivalents; in cases of extreme condensation manganese oxide-coated nodules and corrosion surfaces occur. Stratigraphical evidence favours deposition in quite shallow water. The fauna of the Mediterranean region is the more diverse, but individual abundance, for beds of a given rate of deposition, is greater in north-west Europe, most notably in the case of bivalves.

These facies differences can best be accounted for by interpreting north-west Europe as an area of coastal and inshore waters, whose salinity was lowered slightly by the influx of fresh water from rivers, which brought large quantities of terrigenous detritals, organic matter and iron to the sea. The Mediterranean region was in contrast an area of open but quite shallow sea, of normal marine salinity but deficient in particulate organic matter and hence benthonic fauna. The relevance of this interpretation to other Mesozoic formations is briefly discussed.
Sediments of the Flandrian transgression in south-west Scotland: terminology and criteria for fades distinction
Authors: Jardine W. G.
Published: January 2010

Synopsis

Coastal sediments occurring in central and south-west Scotland at 2 to 10 m above British Ordnance Datum, and hitherto designated the ‘25-ft’ or ‘Post-glacial raised beach’ are shown on theoretical grounds and on the basis of field study in south-west Scotland to comprise at least four distinct fades. Beach, open-bay, estuarine and lagoonal deposits are distinguished, primarily on consideration of shape of the sedimentary body concerned and location of the deposits in relation to the contemporary shore-line, to a lesser degree on consideration of texture, degree of sorting, degree of stratification and organic content. It is suggested that the collective term ‘raised coastal sediments’ rather than ‘raised beach sediments’ be used in reference to this assemblage of deposits.
The sedimentology of sandstone formations within the Upper Old Red Sandstone and lowest Calciferous Sandstone Measures west of Stirling, Scotland
Authors: Read W. A. , Johnson S. R. H.
Published: January 2010

Synopsis

Between Stirling and Fintry the beds between the Lower Old Red Sandstone and the Clyde Plateau Lavas fall naturally into four lithological formations named, from below upwards, the Gargunnock Sandstones, the Cornstone Beds, the Ballagan Beds and the Downie’s Loup Sandstones. All of these formations except the Ballagan Beds consist dominantly of sandstone and are thought to be fluvial deposits. The Ballagan Beds are alternating thin dolomites and mud-stones and are not dealt with in this paper.

The Gargunnock Sandstones rest unconformably upon the Lower Old Red Sandstone. Apart from the basal conglomerates they are uniform, brick-red sandstones with few argillaceous beds and may possibly be the deposits of braided streams which carried detritus from a source area of wind blown sand. The Cornstone Beds and Downie’s Loup Sandstones closely resemble each other despite their being separated by a considerable thickness of Ballagan Beds. Both formations comprise a series of ‘fining-upwards’ cycles, each with a lower sandstone member which is commonly white and an upper siltstone or mudstone member which is commonly red and contains caliche-like cornstones. It is thought that these formations were deposited by meandering streams. Cross-strata dip samples from each formation show that all three were laid down by currents flowing dominantly from the north and west. Statistical tests—chi-squared and Steinmetz’s (1962) method—show that only the sample s from the lower two formations are likely to belong to a single population.
A preliminary study of sandstone sedimentation in the Lower Carboniferous of the Tweed Basin
Authors: Smith T. E.
Published: January 2010

Synopsis

The sedimentology of the sandstones is used, together with the available stratigraphic information, to demonstrate the changes in depositional environment which take place in the Tweed Basin during Lower Carboniferous times.

The characters of the sandstones of the Cementstone Group indicate deposition in a dominantly fluvial environment, the Fell Sandstone is interpreted as a thick widespread shallow marine deposit and the sandstones of the Scremerston Coal Group are mainly of fluvial origin.

An attempt is made to fit these observations into a regional palaeogeographic pattern.
Palaeoecological studies on shell-beds and associated sediments in the Solway Firth
Authors: Wilson John B.
Published: January 2010

Synopsis

The sediments, living fauna, dead shells and valves of the Solway Firth tidal flats at the mouth of the River Nith were sampled along transects. The sediments, which range from inshore silts to fine sands at the mouth of the Nith, are largely derived from the Irish Sea.

The inshore living fauna includes
Cardium edule, Macoma balthica
(the dominant species),
Scrobicularia plana
and
Mya arenaria. Tellina tenuis
is restricted to the fine sands.
Cardium, Macoma, Mya
and
Mytilus edulis
valves are common in the inshore flats.
Cardium
valves are widespread. Shell fragments produced by predation and not by mechanical breakage are common.

The living fauna, shells and valves are reworked and concentrated into channel-floor shell-beds by laterally migrating ebb channels. Surface shell-beds are formed by tidal currents reworking surface sediments. The detailed differences between these two types of shell-bed are used to show that a buried shell-bed formed on a channel floor. The dominant living species suggested by the shell-bed compositions would be
C. edule.
The presence of T.
tenuis
would not be detected.
Landform and structure in Ulster
Authors: George T. Neville
Published: January 2010

Synopsis

The Eocene basalts of Ulster, transgressing all older rocks in a tectonic context ranging from the Highlands across the Midland Valley to the Southern Uplands, were repeatedly deformed and eroded both before and after the deposition of the Oligocene Lough Neagh Clays, without sign of a rift to accommodate them.

The Neogene landform, established after the mid-Tertiary movements ceased, was a wave-planed benched plateau, little warped, superimposed on all the Ulster rocks and structures. It may be followed from Antrim westwards into terrain where pre-Mesozoic formations alone occur, and southwards across the large unroofed Eocene intrusive complexes of Down. It everywhere truncates the Tertiary dykes. As the primary element of the landscape it continues into Connaught, Munster, and Leinster.

The river system is marked by superimposition and by ‘subsequent’ adjustment to structure. It complements the plateau, which it has dissected, in its evidence that the Irish landscape is mainly Neogene in origin.
Nepheline normative eclogite from Loch Duich, Ross-shire
Authors: Mercy E. L. P. , O’Hara M. J.
Published: January 2010

Synopsis

A nepheline normative eclogite containing almandine-rich garnet and Na
2
O-rich (5.47 per cent) pyroxene is described. The origin of the Glenelg eclogites is reviewed and an hypothesis of tectonic emplacement from a deeper metamorphic source in the uppermost mantle preferred. It is suggested that the rocks were originally basic magmas or accumulates from such magmas originally crystallised near the crust-mantle boundary.
On the age of the sediments and contemporaneous volcanic rocks of western Shetland
Authors: Flinn Derek , Miller J. A. , Evans A. L. , Pringle I. R.
Published: January 2010

Synopsis

The ages of sandstones and interbanded andesitic and basaltic lavas, rhyolites and tuff are considered. It is argued that because the sandstones are of two different facies, they are unlikely to be of the same age. One facies is of typical Old Red continental type and contains fish of Middle Devonian age. Isotopic age determinations on a series of volcanic rocks associated with these sandstones indicate a recrystallisation at 300 m.y. ago and a possible origin age at 370 m.y. ago. In the case of the second facies of sandstone neither isotopic ages nor geological evidence from associated lavas indicate whether it is older or younger than the first. An isotopic age from a granite which cuts the second facies of sandstone indicates that the sandstone must be older than 330 m.y., whilst ages determined from interbedded lavas indicate a local recrystallisation or alteration at about 230 m.y. ago.
Post-Scourian metadolerites in relation to Laxfordian deformation in Great Bernera, Outer Hebrides
Authors: Watson Janet
Published: January 2010

Synopsis

In Great Bernera, Lewis, many small basic bodies intruded after the formation of the Scourian gneiss complex were deformed and metamorphosed as a result of Laxfordian orogenic activity. These bodies, now represented by meta-dolerites, appear as contorted bands and lenticles whose outcrop-pattern is determined by the effects of two principal phases of folding. An attempt is made to deduce the initial forms of the intrusions and it is suggested that they were emplaced as members of a dyke-swarm trending roughly east and west. The structures produced by Laxfordian deformation of the metadolerites are compared with those exhibited by deformed metadolerites of the same generation in the Loch Laxford region of the Scottish mainland, and it is suggested that the apparent contrast may have a bearing on the orientation of the direction of Laxfordian compression.
The physical and structural features of the Cairnsmore of Fleet granite and its aureole
Authors: Parslow G. R.
Published: January 2010

Synopsis

The Cairnsmore of Fleet granite is emplaced into Lower Palaeozoic sediments the structure of which is not completely known. The granite exhibits a decrease in biotite content towards the centre, and passes into a biotite-muscovite granite. The outer contact is everywhere sharp and the aureole restricted in width except in the N.E. and S.W. Field evidence indicates steep contacts, but gravity results suggest that at depth they are less steep and that the present outcrop is near the roof of a batholith. The foliation (flow and shear) is generally concordant with the contact except in the S. and S.W. and has the form of a dome structure slightly offset to the S.W. relative to the outcrop. There appears to be no relation between the foliation and the joints and veins in the granite.
Structural analysis of complex fold belts in the Lewisian north of Kylesku, Sutherland, Scotland
Authors: Khoury S. G.
Published: January 2010

Synopsis

Complex patterns, of folds with horizontal axes perpendicular to the foliation in gneiss, occur on vertical foliation surfaces. Similar complex patterns, of corresponding folds with vertically disposed axes, occur on horizontal surfaces. The vertical and horizontal surfaces represent cross-sections near to or within the steep limb of N.W.-S.E. monoclinal fold belts which cut rocks of a crystalline basement. Heterogeneous flow appears to have been operative in the formation of the complex folds. Local intensely developed small-scale folding along narrow N.W.-S.E. fold belts possibly resulted from their coincidence with pre-existing N.W.-S.E. master joints in the basement.
The stratigraphy and structure of the Glen Orchy area, Argyllshire, Scotland
Authors: Thomas P. R. , Treagus J. E.
Published: January 2010

Synopsis

The interpretation of Bailey and Macgregor (1912) and Bailey (1922) is revised. The presence of three major, isoclinal and recumbent folds is demonstrated. Their geometry and facing is described by reference to minor structures, sedimentary structures and the overall stratigraphy. The Glen Orchy Antiform, around which the primary structures are folded, possibly developed together with the primary folds. It is not associated with any minor secondary structures. The structure of the Glen Orchy area raises important questions in the interpretation of the overall structure of the Moine and Dalradian.
Torridonian weathering, and its bearing on Torridonian palaeoclimate and source
Authors: Williams George E.
Published: January 2010

Synopsis

The late-Precambrian Torridonian sediments of the Cape Wrath district, extreme north-west Scotland, unconformably overlie a planar, weathered Lewisian surface. The weathered profile present beneath the unconformity is regarded as Torridonian in age, and hence must rank with the oldest palaeosols in the world. This planar surface was partly stripped of its mantle of altered rock prior to burial beneath Torridonian alluvial fan deposits. Where developed on biotite-gneiss, the weathered profile has the chemical characteristics of a modern pedalfer. A pedocal-type soil developed on amphibolite. The chemical and mineralogical changes are suggestive of a warm, moderately humid climate, possibly with dry periods or a dry season. A similarly weathered Lewisian terrain could, in principle, have supplied the bulk of the overlying Torridonian sediments.
Aspects of the depositional environment and palaeoecology of crinoidal limestones
Authors: Blyth Cain J. D.
Published: January 2010

Synopsis

The paper summarises the limited literature on crinoid ecology and palaeoecology and attempts to interpret the depositional environment of certain British crinoidal sediments in the light of experimental observations. Three types of crinoidal limestone are recognised: muddy limestones deposited in shallow, sheltered waters; poorly washed limestones formed in deeper, open conditions; and clean-washed limestones which may derive in part from the reworking of one or other of the first two types.
Volcanic breccia and the Lower Old Red Sandstone unconformity, Glen Coe, Argyll
Authors: Hardie W. G.
Published: January 2010

Synopsis

According to existing accounts Lower Old Red Sandstone volcanic rocks, together with basal pockets of sediments, rest unconformably upon the quartzitic Moinian and Dalradian inside the north-eastern part of the cauldron-subsidence. Remapping of the ground has shown that although an unconformity is almost certainly present in the north, this does not apply to the southern part, where exposed contacts are vertical and strongly transgressive to the sheet-dip of the volcanic rocks. Here the junction is believed to mark the north-eastern margin of a linear vent, the south-western margin of which is covered by volcanic rocks.

Most of the rocks previously regarded as sedimentary are now known to be volcanic. They consist of dykes of quartzitic explosion-breccia (formed underground) together with larger amounts of extruded explosion-breccia (vent-breccia) occupying the postulated linear vent, as well as a minor volcanic neck. The little undoubted sediment that exists is not
in situ,
but is present as inclusions, up to 100 ft across, in the volcanic rocks.
The Upper Old Red Sandstone-Carboniferous junction at Burnmouth, Berwickshire
Authors: Smith T. E.
Published: January 2010

Synopsis

A conformable junction between the Upper Old Red Sandstone and Lower Carboniferous rocks (Cementstone Group) exposed at Burnmouth in Berwickshire is described. The stratigraphic and palaeogeographic significance of the junction is discussed.
Some rare sedimentary structures in the Silurian rocks of Kirkcudbrightshire
Authors: Walton E. K.
Published: January 2010

Synopsis

A channel structure, linguiform mounds, ridged flame structures, a bellerophontid roll-mark and rilled tool-marks are described from Kirkcudbrightshire.
Cryptovents and allied structures in Carboniferous strata between Port Seton and Aberlady, East Lothian
Authors: Howells M. F.
Published: January 2010

Synopsis

Cryptovolcanic and allied structures cut strata of Passage Group, Upper Limestone Group, and Lower Limestone Group age on the coast between Port Seton and Aberlady. Two structures in Gosford Bay and one on Port Seton beach are oval in form; others at Kilspindie and Port Seton reef are linear in character. One of the structures at Gosford Bay, together with those at Port Seton reef and Kilspindie are breccias with tuff matrices containing basaltic glass. No brecciation or tuff occurs in the structures on Port Seton beach and the other Gosford Bay occurrence; for these a volcanic genesis is inferred by association and by comparison with records elsewhere; they are assumed to occur at a stratigraphic level above the upper limit of tuff penetration.

These structures provide the first evidence of volcanic acitivity younger than the Calciferous Sandstone Measures to the east of the Pentland Fault on the south side of the Firth of Forth.
The coastal features of the Island of Rhum in the Inner Hebrides
Authors: McCann S. B. , Richards Anthony
Published: January 2010

Synopsis

The coast of Rhum is essentially one of cliffs and steep rock and debris slopes of great height, which are in part fossil forms undergoing modification due to present marine erosion at base. The presence, especially along the south-west facing coast of the island which is developed in Tertiary igneous rocks, of elevated marine platforms and raised beach deposits makes it possible to define at least five phases of marine activity which have contributed to the evolution of the coastline. A high-level marine rock platform, probably composite in origin, represents the first recognisable phase of marine erosion and may be correlated with the ‘pre-glacial’ shoreline of the Western Isles defined by W. B. Wright (1911).
Variation in glacial deposition in a sub-glacial environment: an example from Midlothian
Authors: Kirby R. P.
Published: January 2010

Synopsis

A drift section located on the coastal plain of Midlothian shows basal till overlain by an alternating succession of sand and till, the lower layers of sediment grading vertically into each other. Till fabric analyses from four different layers of till show close agreement in orientation direction, dip and strength. It is concluded that the section illustrates a single depositional unit with glacio-fluvial and glacial processes alternating in a sub-glacial environment.
Metamorphic history of Dalradian rocks in Glens Clova, Esk and Lethnot, Angus, Scotland
Authors: Harte B. , Johnson M. R. W.
Published: January 2010

Synopsis

A resumé of structural data showing several periods of deformation is given for the areas considered, followed by an account of the textural evidence for the periods of mineral development in the psammitic-pelitic rocks. The evidence suggests the synchronous growth of garnet, staurolite and kyanite, essentially between the second and third periods of folding. This metamorphic episode was followed by a period of ‘general matrix coarsening’, probably representing an ‘annealing’ process subsequent to the third deformation. Sillimanite (together with some muscovite) is considered to have grown after these events. The results are compared with those of other investigations in the Dalradian. Temperature variation with time during a regional metamorphic ‘event’ is suggested to approximate to a smooth curve with a single ‘peak’ of higher temperature.
A gibbsitic soil derived from the weathering of an ultrabasic rock on the island of Rhum
Authors: Wilson M. J.
Published: January 2010

Synopsis

The mineralogy of a soil derived from the weathering of an ultrabasic rock near the summit area of Askival on the Island of Rhum was investigated by optical, X-ray diffraction and differential thermal techniques. The fine sand fraction is dominated by olivine and anorthitic plagioclase felspar whilst the clay fraction contains gibbsite and chlorite. General weathering reactions in the soil are discussed and the origin of the gibbsite is considered in detail.
Alkaline basic igneous rocks in the Orkneys
Authors: Kellock E.
Published: January 2010

Synopsis

A group of alkaline basic igneous rocks in the eastern part of the Orkney Islands is described as seen in the field and petrographically. The rocks differ from the andesitic and calc-alkaline Old Red Sandstone igneous rocks of Shetland and the Scottish mainland. They show marked similarity to the Carboniferous teschenites and basanites of the Midland Valley of Scotland, but the Middle Old Red Sandstone age assigned to them in previous accounts is upheld.
Evidence for the age of deposition of the Torridonian sediments of north-west Scotland
Authors: Moorbath S.
Published: January 2010

Synopsis

Rb-Sr whole-rock measurements are reported for shales and siltstones from the Torridonian sediments of north-west Scotland. Excellent isochrons are obtained whose slope is interpreted as being proportional to the time of diagenesis of the sediments, closely following deposition and compaction. The Lower Torridonian of Stoer, below the recently discovered stratigraphical unconformity, gives an isochron age of 935±24 m.y. The Upper Torridonian Applecross Formation near Gairloch, above the unconformity, gives an isochron age of 761±17 m.y. The latter isochron, when combined with several points from the Cailleach Head Formation, near the top of the Torridonian succession, yields a composite value of 751±24 m.y.

From these age data it appears that the unconformity between the rapidly deposited Lower and Upper Torridonian sediments may reflect a time interval of about 170 m.y. This is in general accord with the very different palaeomagnetic pole positions which have been reported for the Lower and Upper Torridonian.
The relationships of the Leny Limestone to the Dalradian
Authors: Harris A. L.
Published: January 2010

Synopsis

The Lower Cambrian Leny Limestone shows evidence of a structural history similar to that recorded in undoubted Dalradian rocks. This similarity confirms the view that the Leny Limestone forms part of the Dalradian and that the first folding of the latter into the Tay Nappe occurred at the Highland Border during or after the Lower Cambrian.
The Sandy’s Creek Beds (Devonian) of Farland Head, Ayrshire
Authors: Downie C. , Lister T. R.
Published: January 2010

Synopsis

The rocks of controversial age occurring at Sandy’s Creek near Farland Head, Ayrshire, consist of red lithic sandstones and grey quartz siltstones. The latter contain miospores indicating terrestrial deposition in the Lower Devonian.

These distinctive rocks are named the Sandy’s Creek Beds. They are older than the adjacent Portencross Beds also of Lower Old Red Sandstone age. Resemblances between these rocks and parts of the Lower Old Red Sandstone in Arran are indicated.

The structure is explained by the presence of a shear belt of Armorican age.
The Precambrian gneiss complex of Ness, Lewis, in relation to the effects of Laxfordian regeneration
Authors: Watson Janet
Published: January 2010

Synopsis

The Lewisian gneisses of Ness, at the northern tip of the Outer Hebrides, contain abundant metasedimentary relics including calc-gneisses, quartzites, pelites and semi-pelites. These rocks were partially migmatised during the earliest recognisable metamorphic episode and subsequently developed a characteristic flaggy structure and fine-grained texture during two later episodes of deformation associated with incomplete recrystallisation. An irregular belt of anorthosite, at least five kilometres in length, was probably emplaced before migmatisation. It is inferred, from the age-relationships of Late Laxfordian pegmatites and of metadolerites comparable with the post-Scourian basic suite of the Outer Hebrides, that the early migmatisation was Scourian and that the two later tectonic episodes were Laxfordian. The style of Laxfordian regeneration contrasts with that of the ‘grey gneisses’ in adjacent parts of Lewis and it is suggested that this difference depended partly on the operation of temperatures and pressures rather lower than those of most other regions and partly on the inherited effects of lithological and structural contrasts established in Scourian times.
Communication in Geology
Authors: Craig G. Y.
Published: January 2010

Synopsis

Many geological papers are too long and are poorly written. The production of geological information seems to be doubling every ten to fifteen years and has far outstripped its consumption. To improve the situation refereeing must be firmer and papers shorter and clearer. In the near future Editorial Boards will have to decide whether a paper should be retained in typescript form, or what parts should be published in a journal, photographed on microfilm-card or stored in a data bank. The decision on the best way in which the information should be presented may be based on an estimate of the number of serious readers and the financial costs involved. Some of the money at present spent on geological research should be devoted to ensuring that the results are more effectively communicated.
Torridonian alluvium and quicksands
Authors: Selley R. C.
Published: January 2010

Synopsis

This paper provides new data on Torridonian alluvium on Raasay, confirming its braided origin and refining its environmental interpretation. Fining-upwards cycles appear to be absent. This may be an important criterion in distinguishing deposits of braided rivers from those due to meandering rivers. A quantitative study reveals a close correlation between grain size and sedimentary structures. With decreasing grain size, the sedimentary structures are broadly arranged in the following order: trough cross-bedding, planar cross-bedding, flat bedding, massive bedding, micro-cross-lamination, lamination.

Two types of siltstone sequences are distinguished. The more common type lies between two erosional surfaces and is attributed to deposition in abandoned channels. Its thickness suggests that streams seldom attained a depth of more than one metre in this environment. The second type is attributable to overbank deposition, having an erosional top and a transitional base.

Finally, the origin of the ubiquitous Torridonian quicksand structures is considered in the light of experimental work. Previous writers have put forward three possible triggering mechanisms for these bedding disturbances, viz.: springs, earthquakes and current turbulence. Simulation of all three processes produced quicksands in the laboratory but the weight of evidence suggests current turbulence to be the most probable triggering mechanism.
Zircon U-Pb ages from the Galway granite and the Dalradian, Connemara, Ireland
Authors: Pidgeon R. T.
Published: January 2010

Synopsis

The zircon U-Pb age of 510±10 m.y. of the Cashel-Lough Wheelaun basic intrusion establishes a point early in the time span of the Dalradian metamorphism in Connemara; the intrusion is post F
1
and late M
1
but pre-F
2
. This is also a maximum age for the base of the Lower Llanvirn and can be linked with Rb-Sr results if the 5.0 × 10
10
y Rb
87
half-life is used. The metasedimentary zircon results are compatible with an isotopic disturbance(s) between 400 and 510 m.y. and suggest that a large proportion of the source rocks were older than 1200 m.y. The U-Pb isotopic relationships of the metasedimentary zircons have similar features to those of cogenetic zircon suites.
The ultrabasic/basic igneous rocks of the Huntly region
Authors: Weedon D. S.
Published: January 2010

Synopsis

Detailed examination of the ultrabasic/basic igneous rocks at the southern end of the Huntly mass has indicated that an unbroken layered sequence from the picrite and troctolite, through olivine-gabbro into norite does not exist.

A major break occurs between the more ultrabasic rock types and the ‘norites’, shown by contrasting olivine and plagioclase compositions, measured and normative, and the sharp breaks in various cation ratios of the major elements. This is emphasised by the distribution of various trace elements, which also give some indication of the possibility of a further break within the layered sequence itself.

In the light of this evidence, the Huntly mass should no longer be considered as part of a large ‘Bushveld type’ layered sheet and this may justify a re-appraisal of the other basic igneous masses of NE. Scotland which may well have been emplaced at differing structural levels and at different times.
The Morven-Cabrach basic intrusion
Authors: Allan W. C.
Published: January 2010

Synopsis

The rocks of the southern half of the Morven-Cabrach mass consist mainly of norites, with two northerly dipping layers of ore- and olivine-rich ferrogabbro. In the north there is a progression of rocks from hypersthene-gabbro through quartz-biotite-norite to xenolithic quartz-mica-diorite. All the rocks are relatively iron-rich, and no highly magnesian types are found. Mineral compositions are remarkably constant, and chemical variation is slight. The mass has been intruded in its present position and is a (relatively) narrow, steep-sided, dyke-like body.

A tentative hypothesis, based largely on the dimensions of the mass and the high temperatures of the country rocks, is put forward for the lack of cryptic variation. The relationships between the Morven-Cabrach mass and the postulated north-east basic sheet are considered, and a feeder-pipe role is suggested for Morven-Cabrach.
The role of partial fusion in the genesis of certain cordierite-bearing rocks
Authors: Gribble C. D.
Published: January 2010

Synopsis

Cordierite-bearing xenolithic rocks, including quartz-cordierite-norites, which occur in association with basic igneous rocks in many parts of north-east Scotland, represent Dalradian country rocks which have undergone partial melting at the time of intrusion of the basic magma.
The geochronology of the basic igneous complexes
Authors: Pankhurst R. J.
Published: January 2010

Synopsis

Rb-Sr whole-rock isochrons for the Upper Zone of the Insch mass and aureole schists of the Haddo House mass indicate crystallisation of the basic sheet of NE. Scotland at 486± 17 m.y. ago (t½ = 4.85 × 10
10
y. for Rb
87
). It is argued that intrusion occurred into hot country rocks during, or very soon after, the migmatite overprint phase of the climax of regional metamorphism (M
3
) in the Dalradian Series, so that this is also dated at about 486± 17 m.y. Small bodies of gneissose rocks in the Arnage mass give a whole-rock isochron age of 479± 12 m.y. and are interpreted as intrusions slightly younger than the Newer Gabbros. Post-metamorphic granites at Insch and Haddo House are dated at 459± 8 m.y.

K-Ar mica ages from the gabbro complex are extremely uniform at 461 ± 5 m.y., whereas Rb-Sr ages on some of the biotites range from 471 ± 22 m.y. to 428 ± 9 m.y. Together, these ages preclude the hypothesis of overprinting by any discrete metamorphic event younger than the main climax. Instead, they are interpreted as indicating rapid post-orogenic uplift in NE. Scotland at about 460 m.y. ago.
The structural and metamorphic state of the Dalradian rocks and their bearing on the age of emplacement of the basic sheet
Authors: Fettes D. J.
Published: January 2010

Synopsis

A third generation cleavage in the Macduff Slates is shown to post-date the Insch basic intrusion. The effects of the third generation movements on the basic sheet are discussed. Evidence based on the distribution of metamorphic porphyroblasts and textures shows that the basic sheet was intruded during the main metamorphic crystallisation of the area.
Gneiss types and their significance in the repeatedly deformed and metamorphosed Lewisian Complex of Western Harris, Outer Hebrides
Authors: Myers J. S.
Published: January 2010

Synopsis

The main gneiss types of Western Harris are described and grouped according to the forms and associations of rock units seen on the scale of an outcrop. Although they were subsequently modified during Laxfordian episodes, they chiefly reflect an earlier history from which few minerals or fold structures survive. Criteria by which the gneiss types can be recognised are described and the significance of the gneisses in relation to the early history of the complex is discussed. Most of the region described consists of quartzo-feldspathic gneisses but some patches of rocks with distinctive mineral assemblages appear to represent metasedimentary remnants; the significance of these is discussed together with that of the Langavat belt of metasediments.
The identity of the Lickar Limestone of north Northumberland and its underlying coals
Authors: Farmer N. , Jones J. M. , Murchison D. G.
Published: January 2010

Synopsis

Four shallow boreholes drilled in the Upper Limestone Group of Northumberland with a motorised hand-held rig indicate that the correlation of the Lickar Limestone of Lickar with the Lickar Limestone of Howick 20 miles to the south is incorrect. There is no stratigraphical, lithological or faunal evidence to support the present correlation, which requires either excessive northward thinning of the strata or the presence of an unconformity for which there is no field or borehole evidence. Correlation of the Lickar Limestone of Lickar with the Cushat (Little) Limestone removes these difficulties. It is proposed to rename the Lickar Limestone of Howick, the Howick Limestone.
An apparent age for a member of the Scourie dyke suite in Lewis, Outer Hebrides
Authors: Lambert R. St J. , Myers J. S. , Watson J.
Published: January 2010

Synopsis

The Cleitichean Beag intrusion of central Lewis, assigned by Dearnley to the suite of pre-Laxfordian minor basic intrusions in the Lewisian of the Outer Hebrides, has yielded whole-rock K–Ar ages giving an average value of 2440±60 m.y. This body has not suffered obvious deformation or metamorphism and lies in an area where effects of Laxfordian regeneration are relatively slight; there is no evidence to suggest that excess argon is present. The date obtained is taken to be close to the original time of intrusion.
Significance of calc-silicate rocks and meta-arkose in the Lewisian complex south-east of Scourie
Authors: Barooah B. C.
Published: January 2010

Synopsis

Lenses of calc-silicate rock and bands of meta-arkose occur among banded pyroxene- and hornblende-granulites south-east of Scourie, Sutherland, Scotland. This rock association, together with the chemical composition of the granulites and their deformational history, suggest that the granulites represent a lava pile intercalated with siliceous and calcareous sediments.
Notes on the age of metamorphism of the Moinian
Authors: Johnson M. R. W. , Shepherd J.
Published: January 2010

Synopsis

A post-Cambrian age for the main metamorphism of the Moinian is supported by recent work in the Carn Chuinneag–Assynt region. The earliest structures in the Moinian ante-date the 530 m.y. old Carn Chuinneag granite and can only be assigned to the
post-Cambrian
orogenesis if a minimum age of 530±10 m.y. is assumed for the Cambro–Ordovician boundary.
The south-east limit of the Moffat Shales in the upper Ettrick Valley region, Selkirkshire
Authors: Toghill P.
Published: January 2010

Synopsis

The south-east limit of the Moffat Shale inliers in the Llandovery greywackes of the Moffat area is shown to be a major NE.-SW. dislocation, the Ettrick Valley Fault. This thrusts the tightly folded Moffat terrain over younger (
turriculatus
and
crispus
Zones) greywackes to the south-east which dip, and young, consistently north-west. Contrary to previous opinion (Walton 1963) there is no evidence, in the Moffat area, for any south-eastward passage of the Birkhill Shales into greywackes. The most south-eastern exposures of the Moffat Shales, and particularly the Birkhill Shales, in the Upper Ettrick Valley, show the same thicknesses and lithologies as at the typical locality of Dobb’s Linn. The structure of the Upper Ettrick Valley is shown to be of an imbricate type caused by the shearing out of inverted limbs of isoclines, thus causing the repetition of Moffat Shales across the strike of greywackes which dip and young consistently north-west. High angle reverse faults in the greywackes SE. of the Ettrick Valley Fault may offset the north-westerly younging and cause the succession to become younger south-east towards the Hawick Rocks.