bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evolving life of the developing Caledonides
Authors: Holland C. H. , Hughes C. P. 
Published: May 2008

Summary
This review is largely confined to the evolution of life during the late Precambrian to early Devonian period of earth history represented by the developing Caledonides of the British Isles. It begins with reference to Precambrian floras and faunas tantalisingly glimpsed in the Dalradian of Scotland and Ireland and in isolated occurrences in Charnwood Forest and in South Wales. Cambrian life is variously represented in the Durness Limestone, in the younger Dalradian rocks, in the Bray Group and its equivalents, and in the classical sequences of Wales and England. Summary treatment only is possible of the vastly detailed palaeobiological record in the Ordovician and Silurian rocks of the British Isles. There is cross-reference to other contributions in this section of the present volume. The vascular plants and vertebrates are treated separately by other authors.
The early history of vascular plants based on late Silurian and early Devonian floras of the British Isles
Authors: Edwards D. 
Published: May 2008

Summary
Vascular plant assemblages are described from late Silurian (Ludlow and Downtonian), Gedinnian, Siegenian, and Emsian localities in Britain. Various kinds of evidence are used in an attempt to reconstruct the habitats and life histories of early land plants.
The later stages of the Caledonides in the British Isles coincided with one of the most important events in plant evolution—the appearance of vascular plants. As today the majority of such plants are terrestrial, it may be assumed that the macrofloras occurring in late Silurian and Early Devonian sediments of southern Britain and Scotland record episodes early in the colonisation of land surfaces. Plants of quite different affinities but which also possess anatomical modifications indicating tolerance of hostile drying sub-aerial conditions are sometimes present in the floras. These together with microfossils will be omitted from this account.
Early vertebrates and the Caledonian earth movements
Authors: Dineley D. L. , Loeffler E. J. 
Published: May 2008

Summary

Vertebrate remains from Ordovician formations indicate a conservative mode of life in marine environments but which seems to have become more diverse by the invasion of varied
non-marine
aquatic habitats in Siluro-Devonian time. The spread of Old Red Sandstone facies results from Caledonian tectonism and provides the earliest Phanerozoic example of an adaptive radiation of both agnathan and gnathostome vertebrates. Prior to the late stages in the closure of Iapetus the ‘European’ and ‘American’ vertebrate faunal assemblages were distinct. Closure brought an immediate influx of ‘American’ agnatha into the European area, and a rapid increase in numbers of species. Subsequent earth movements and changes in palaeogeography favoured the development of internal basins with accompanying differentiation of vertebrate stocks. Some primitive forms, perhaps relatively isolated geographically, persisted until the Late Devonian by which time non-marine gnathostomes had spread to most of the continents.
New evidence for the age of the Manx Group, Isle of Man
Authors: Molyneux S. G. 
Published: May 2008

Summary
Acritarch assemblages which are sufficiently well preserved to date the rocks in which they occur have been obtained from five formations in the Manx Group of the Isle of Man. The acritarch evidence indicates that the Niarbyl Flags, Glen Dhoo Flags, and Lonan Flags are most probably Tremadoc in age, the last two very late Tremadoc. The Maughold Banded Group is probably Arenig and the Lady Port Banded Group is probably either late Arenig or early Llanvirn. The minimum time interval represented by the Manx Group is late Tremadoc to late Arenig and a correlation of the Manx Group with the Skiddaw Group in NW England and the upper part of the Ribband Group in SE Ireland is proposed. The contemporaneous volcanic rocks in the Manx Group at Peel, here named the Peel Volcanic Formation, are probably upper Arenig in age.
The distribution of trilete spores in Irish Silurian rocks
Authors: Smith David G. 
Published: May 2008

Summary
Trilete spores of land-plant type have been recovered from probable late Llandovery to early Ludlow sediments in several widespread parts of Ireland, and they have proved to be stratigraphically useful in otherwise unfossiliferous outcrops. In many cases, spores have been found in offshore marine sediments of turbidite facies in which they are accompanied by only minor quantities of marine palynomorphs (acritarchs, chitinozoa). Possible explanations for this unexpected association are considered in the light of what is known of Irish Silurian palaeogeography; they include reworking of nearshore shelf assemblages by turbidity currents and contour currents, and transport of land-derived spores by wind and surface-water currents. The possibility that the spore-bearing plants were pelagic is also considered.
Microfossil distribution in the Silurian of Britain and Ireland
Authors: Aldridge R. J. , Dorning K. J. , Hill P. J. , Richardson J. B. , Siveter D. J. 
Published: May 2008

Summary
Microfossils are diverse, abundant, and well-preserved in the Silurian shelf sediments of the British Isles, but are scarcer in graptolitic shale and greywacke sequences. Most work has concentrated on the Welsh Borderland where acritarchs, miospores, conodonts, and ostracodes have all proved stratigraphically valuable. Acritarchs, chitinozoa, and scolecodonts are all abundant from middle Llandovery to upper Ludlow strata and ostracodes are common from the upper Llandovery to the Downtonian. Conodont abundance is highest in the Whitcliffian, but diversity and biostratigraphical value are greatest in the upper Llandovery. Ostracodes are of particular correlative use from the middle Ludlow to Downtonian and acritarchs are important from the middle Llandovery to the upper Ludlow. Miospores are very scarce in Llandovery sediments but in Ludlow and Downtonian strata they are abundant and diverse. All groups display some facies dependence, but miospores occur in a range of nearshore shelf, estuarine, and alluvial deposits and, of the marine groups, acritarchs show least environmental control. Arenaceous foraminifera, hydrozoa, and melanosclerites are sporadically abundant.
The environmental significance of some faunal changes in the Upper Ardmillan succession (upper Ordovician), Girvan, Scotland
Authors: Harper D. A. T. 
Published: May 2008

Summary
A series of discrete, distinctive faunules has been established for the Upper Ardmillan succession in the Girvan district. The faunules, collected from a diverse suite of clastic sedimentary rocks in a well defined stratigraphical framework, belong to the Whitehouse Group, the Shalloch Formation, the Drummuck Group, and the High Mains Formation; these rock units range in age from late Caradoc (Onnian) to late Ashgill (Hirnantian). The brachiopod associations identified within each faunule are outlined; few are considered indigenous. The series of faunal changes is fundamental to the assessment of the depositional environment of the sequence.
The changing composition and structure of the brachiopod associations appear to reflect deposition in a predominantly unstable and often turbulent offshore continental slope environment. The faunal and sedimentary evidence supports the existence of a submarine fan throughout at least much of Upper Ardmillan times at Girvan.
Trilobite associations in the British Wenlock
Authors: Thomas A. T. 
Published: May 2008

Summary
Five common trilobite associations occur in the British Wenlock. The associations are characterised by increased abundance of particular genera and their distribution is related to changes in lithofacies and position on the palaeoslope. Comparable associations are widespread in the Silurian of other parts of the world. Similar lithofacies of different ages often contain generically identical trilobite assemblages thus highlighting the dangers of basing correlations upon comparisons made above the specific level.
Caledonian echinoderms of the British Isles
Authors: Paul C. R. C. 
Published: May 2008

Summary
The Lower Palaeozoic echinoderm fauna of the British Isles is meagre in the Cambrian, but much more diverse in the Ordovician and Silurian. A change from blastozoanto crinozoan-dominated faunas is probably a real evolutionary change, but is largely due to the exceedingly rich Ashgill cystoid fauna and the equally varied Wenlock Limestone crinoids. Changes in the echinoderm fauna from the early Ordovician to the Silurian imply that provincialism gave way to cosmopolitanism; a cooler climate became subtropical, despite the Upper Ordovician glaciation; and that crinoids replaced blastozoans because they were more efficient filter-feeders.
Extinction of the graptolites
Authors: Koren’ T. N. , Rickards R. B. 
Published: May 2008

Summary

Graptoloids became extinct in latest Early Devonian (Pragian) times, and dendroids in the late Carboniferous. There is insufficient information for the other six graptolite orders to suggest when they might have become extinct, so that in these cases it is impossible as yet to speculate how extinction occurred. The dendroids survived apparently unchanged from their first appearance in the Mid-Cambrian until the late Carboniferous, whereas the graptoloids enjoyed four major and spectacular evolutionary bursts in a planktonic, largely tropical environment: those of the Arenig/Llanvirn; the
gracilis
Zone; the Llandovery; and the Ludlow. The post-Ludlow strata record three further smaller diversifications, of successively decreasing speciation, one in the Silurian (Přídolí) and two in the Devonian (Lochkov & Pragian), the last marking the extinction of the graptoloids. Between the evolutionary bursts are evolutionary lows in terms of species diversity. After examining these major revolutionary events (for which speculative reasons are given) as preludes to the extinction of the graptoloids, it is concluded that this final act was result of a gradual restriction of the particular ecological niche occupied by the morphologically less varied Devonian monograptids. The nature of this and other planktonic niches is as yet unknown. A general reduction, following the Ordovician, of the planktonic biomass, and the phytoplankton component on which the graptolites probably fed, was probably largely responsible for the extinction of this order of graptolites. Further, the changes in the nature of the sea margins during the Caledonian orogeny, and the rise of the land plants, are speculatively related to both the extinction of the graptoloids and, later, the dendroids. Competition with other active nekton feeders, except possibly the dacrionarids, is considered unlikely.
O. T. Jones and after: A multitude of models
Authors: Holland C. H. , Kelling G. , Walton E. K. 
Published: May 2008

Summary
The geosynclinal synthesis by O. T. Jones can be taken as the first major model for the British and Irish Caledonides. It was followed by a period of consolidation and exploration in which ground was covered (though by no means all of it); biostratigraphy was treated with increasing rigour; there were developments relating to faunal provincialism; new techniques and understanding of sedimentology transformed the palaeogeographical picture; and structural studies increased in sophistication with the recognition of polyphase deformation and strain patterns. Since the advent of the plate-tectonic hypothesis, an evolution of models can be traced as workers have explored the many and increasingly complicated possibilities. No model is entirely satisfactory; some earlier models can now be discarded with some confidence; others deserve further development, but many critical facts remain to be collected.
Slopes, submarine fans, and syn-depositional faults: sedimentology of parts of the Middle and Upper Dalradian in the SW Highlands of Scotland
Authors: Anderton R. 
Published: May 2008

Summary
The depositional palaeogeography of the metasediments between the Jura Quartzite and Craignish Phyllites was dominated by a series of fault-bounded blocks and basins. The position of the basin margins, and hence the faults, is inferred from the location of submarine fan and slope facies and lateral thickness variations. These syn-depositional faults had trends either approximately parallel with, or normal to, the subsequent Caledonoid grain and had throws of up to several kilometres. Such faults may have exerted a major control over sedimentation throughout the Middle and Upper Dalradian. Many of the Dalradian sedimentary bodies therefore have a complex geometry, and persistent stratigraphical horizons may reflect regional climatic and tectonic events, rather than persistent sedimentary facies.
Stratigraphy of the aureole of the Cairnsmore of Fleet pluton, southwest Scotland
Authors: Cook D.R. , Weir J.A. 
Published: May 2008

Summary

This Lower Palaeozoic succession is cut by four major strike faults of which the southeasternmost, the Pibble fault, is correlated with the Ettrick Valley fault. NW of the Pibble fault, Moffat Shales are overlain by greywackes of the Craignell Formation. Upper Birkhill Shales in the northwestern fault segment give way southeastwards to greywackes, extending downwards to the
M. gregarius
Zone. SE of the Pibble fault, greywackes comprise the Knockeans Formation, correlated with the Hawick Rocks and overlying the Craignell Formation. Maturity increases upwards. Within the Craignell Formation a basic source gives way to a dominant, granitic source, and this in turn to a metamorphic source. The Knockeans Formation is strongly silicic and probably recycled. Southward passage from pelagic to flysch facies may indicate a southward source for higher levels of the succession.
Oceanic sediments from the Ordovician of the Southern Uplands
Authors: Leggett J. K. 
Published: May 2008

Summary
Fe-rich mudstones are intimately associated with Ordovician basalts in the Northern Belt of the Southern Uplands of Scotland. Field relations and geochemistry suggest that a significant proportion of the mudstone may be of hydrothermal-exhalative origin, having formed in a manner analogous to metalliferous sediments from modern active ridges. Cherts of Arenig to Llandeilo age overlie the basalts and contain abundant radiolarian remains. Carbonaceous mudstones replace the cherts near the base of the Caradoc. These are devoid of benthos, and herald the first of two euxinic phases (Caradoc and lower Llandovery) during the pelagic mudstone (Moffat Shale) regime. Coincidence with periods of transgression suggests that euxinification may have been induced by oceanographic factors relating to changes in sea level.
The north-western margin of the Iapetus Ocean
Authors: Leggett J. K. , McKerrow W. S. , Morris J. H. , Oliver G. J. H. , Phillips W. E. A. 
Published: May 2008

Summary
A review of the stratigraphy, sedimentology, petrography, and structure of the Ordovician and Silurian rocks of the Southern Uplands (Scotland) and the Longford-Down zone (Ireland) identifies many features which are typical of accretionary wedges developed at Mesozoic-Recent subduction zones. The bedding becomes gradually more inverted in the west and northwest parts of the Longford-Down zone. Slumping becomes increasingly important along strike southwestwards from Scotland to Ireland. The roles of transform movement along the continental margin and of back arc spreading are also considered.
Sedimentary environments of the basinal Llandovery of mid-Wales
Authors: Cave R. 
Published: May 2008

Summary

The position of the Ordovician-Silurian junction in the mid-Wales rock sequence remains elusive. There is no evidence of a break in sedimentation between the periods but conditions of deposition changed abruptly about then; presumed Ashgill rocks, mainly argillaceous and disturbed, are overlain by Llandovery strata with even and regular bedding, yielding
Glyptograptus persculptus
(Salter). The former are barren and accumulated rapidly, near the foot of a slope facing west from the ‘shelf’, synchronously with a marine regression and a glaciation in N Africa. The regresson may therefore have been a sympathetic eustatic fall. Of the succeeding strata, those of lower Llandovery age embody much pelagic mud while the middle and upper Llandovery strata record an invasion by turbidite fans. Current indicators in the turbidites reveal westward (‘lateral’) flow below the Aberystwyth Grits (low
turriculatus
Zone), later augmented or replaced by northwards (longitudinal) flow. This change stemmed probably from a tectonic event to the south.

Characteristic turbidite rhythms have been noted, varieties of which are used to define many of the formations. Such formations are probably highly diachronous.
Early history of the southern margin of the Tywi anticline in the Carmarthen area, South Wales
Authors: Cope John C. W. 
Published: May 2008

Summary
The area SW of Carmarthen exposes Precambrian, Cambrian, and Ordovician rocks, unconformably overlain by Old Red Sandstone. Frequent depositional breaks and derived fragments of igneous and metamorphic rocks suggest a nearby land area. Periodic movement along the Llandyfaelog disturbance may have controlled sedimentation locally. Complex Caledonian structures in the area involve Lower Old Red Sandstone and may be due to the presence of basement at shallow depth.
South-east Ireland: Lower Palaeozoic stratigraphy and depositional history
Authors: Brück P. M. , Gardiner P. R. R. , Reeves T. J. , Shannon P. M. , Colthurst J. R. J. , Feely M. , Penney S. R. , Smith D. G. , Vanguestaine M. 
Published: May 2008

Summary
Four lithostratigraphical groups are distinguished in the Lower Palaeozoics of SE Ireland. The sand-dominant Lower-Middle Cambrian Bray Group consists of laterally-derived flysch. The conformably overlying, and perhaps in part time-equivalent, mud-dominant Middle Cambrian-Llandeilo Ribband Group comprises axially-transported flysch with minor volcanics. Due to tilting and subsequent differential erosion of these trough sediments, the overlying mainly Caradoc Duncannon Group rests unconformably on the Ribband Group except in the west where there is a conformable passage. The Duncannon Group is a highly faulted, predominantly volcanic, platform sequence with local basal calcareous beds. In the northwest of the district, the Bray and Duncannon Groups are absent and a continuous period of flysch sedimentation is reflected by the upward passage of lower Ordovician Ribband Group sediments into sand-dominant turbidites of the Kilcullen Group (lower Ordovician to at least Llandovery). In contrast, the Slievenamon inlier in the southwest contains Ribband Group strata of Upper Cambrian age which palynological evidence suggests are separated by a major stratigraphical break from the entirely Silurian Kilcullen Group. In the Comeragh Mountains to the south, the Kilcullen Group is conformably underlain by the Ribband and Duncannon Groups. These features point to large-scale irregularities within the Leinster Basin, the main Lower Palaeozoic palaeogeographical feature of SE Ireland.
Ordovician stratigraphy of the Tramore area, County Waterford, with a revised Ordovician correlation for south-east Ireland
Authors: Carlisle H. 
Published: May 2008

Summary
The Ordovician succession around Tramore is complicated by contemporaneous and later faulting and by widespread intense volcanicity. Early Ordovician NE-SW faulting divides the rocks of the Ribband Group so that to the east of the area the Tramore Group rests unconformably on the Arenig (?) Tramore Shale Formation and in a basin to the west a sequence of intermediate and basic volcanics and volcaniclastics, here named the Ballynaclogh Volcanic Formation, pass conformably into the Tramore Group. A Llanvirn to lower Llandeilo age is suggested for this formation.
It is proposed that the remaining five formations of the succession, ranging from lower Llandeilo to Longvillian in age, be termed the Tramore Group. The oldest of these, the Tramore Limestone Formation, marks a relatively stable period before the extensive predominantly acidic volcanicity which dominates the remainder of this group. The relatively thick basinal facies of this formation exposed mainly in coastal sections west of Annestown can be divided into two members: the lower, the Dunabrattin Shale Member and the upper, the Dunabrattin Limestone Member. Variations in the rich shelly fauna of this formation are shown to be partly related to facies change. Overlying this is a sequence of subaqueous acidic tuffs, volcaniclastics, and argillaceous rocks for which the name Carrighalia Formation is proposed. The remaining three formations have been named by Williams (1972, fig. 10) but are redefined in the present study.
A brief discussion of the regional correlation of the Tramore Group is included.
Caledonide volcanism in Britain and Ireland
Authors: Stillman C.J. , Francis E.H. 
Published: May 2008

Summary
This paper reviews the state of knowledge of the volcanic activity which accompanied the development of the Caledonide orogen in Britain and Ireland. Unlike the relative abundance of stratigraphical data, geochemical information is scarce in earlier accounts, but in the last decade or so there has been a surge of interest coincident with the introduction of rapid analytical techniques and with the development of methods for distinguishing primary petrographical and chemical characteristics from those of subsequent alteration. Many of the Caledonide volcanic rocks were erupted into or beneath water, interbedded with sediments and then affected by orogenic deformation and metamorphism, yet this has apparently had less effect than might be expected on the gross geochemistry of the volcanic rocks. In the paratectonic Caledonides, submarine weathering and low-grade hydrous metamorphism have been the principal causes of element mobility, and the effects produced are, in many cases, remarkably similar to those which affect present-day eruptives in oceanic environments.
Late Precambrian igneous activity in Southern Britain
Authors: Thorpe R.S. 
Published: May 2008

Summary
Late Precambrian igneous activity was widespread in England, Wales, SE Ireland and the Channel Islands. This activity included calc-alkaline intrusive and volcanic complexes which, although showing important regional differences, have many similar features. Recent U-Pb and Rb-Sr isotopic ages indicate that this activity was broadly contemporaneous at ca 600 ± 50 Ma. The initial Sr isotope ratios of these igneous rocks indicate that they largely represent new additions to the continental crust in an island arc-continental margin setting during a major period of crustal growth in south Britain.
Basic volcanic rocks in the Dalradian of Ireland
Authors: Max M.D. , Long C.B. 
Published: May 2008

Summary
Basic volcanic rocks in the Dalradian Supergroup of Ireland are identified and listed here. They are widespread, though stratigraphically restricted, and provide useful marker horizons locally in Connemara, Achill Island, the Nephin Beg Mountains, the Ox Mountains inlier, and counties Donegal, Tyrone, Londonderry, and Antrim. A major volcanic unit is found in the Argyll Group (Easdale Subgroup) in the west of Ireland, whereas in N Ireland, including Donegal, several units are recorded in or immediately below the Southern Highland Group. Pillow lavas, lavas, agglomerates, hyaloclastites, tuffs and combinations of these occur. Minor striped amphibolites reminiscent of the tuffaceous or lava lithologies of the Lakes Marble Formation (Easdale Subgroup) are present throughout much of the Connemara succession. Incoming of the first substantial thickness of volcanics is associated with a change from stable, shallow-water, continental-shelf deposition to deposition of a deeper water, greywacke facies, associated with rifting and block faulting.