bluuebunny/crossref_metadata_2025_split huggingface dataset:
A review of Devonian time scales: databases, construction and new data
Authors: Williams E. A. , Friend P. F. , Williams B. P. J. 
Published: April 2008

Abstract

Aspects of the isotopic age and stratigraphical databases underpinning Devonian geological time scales are reviewed to assess differences in recent U-Pb zircon-based schemes and older schemes based on Rb-Sr, K-Ar,
40
Ar-
39
Ar dating of minerals and whole-rock samples. The various methods of time-scale construction are described and, with their databases, 14 calibrations of Devonian time are discussed. Finally, the most recent data are collated and compared against current U-Pb-based time scales.
Coastal-fluvial palaeoenvironments and plant palaeoecology of the Lower Devonian (Emsian), Gaspé Bay, Québec, Canada
Authors: Griffing David H. , Bridge John S. , Hotton Carol L. 
Published: April 2008

Abstract

The Cap-aux-Os Member (of Emsian age) of the Battery Point Formation, Gaspé Bay, Québec, comprises coastal and fluvial deposits containing abundant, well-preserved remains of early land plants (embryophytes). Metres-thick sandstone bodies represent the deposits of the main river channels, including some that were tidally influenced. Thinner sandstone bodies within mudstone successions represent deposits of crevasse splays-levees, lacustrine deltas, tidal channels, flood-tidal deltas and washovers. Mudstone-dominant strata represent backswamps and marshes, lakes, coastal bays and tidal flats. Certain plants (trimerophytes,
Huvenia
and
Sciadophyton
) are particularly common on the moist, upper parts of near-coastal channel bars. They apparently germinated and grew rapidly on freshly exposed muds deposited during floods or exceptionally high tides.
In situ
zosterophylls are most common in backswamp and marshy areas, where they formed extensive, relatively longlived stands. It is uncertain whether these plants were tolerant of brackish water or killed by it. However, absence of acritarchs in these
in situ
plant horizons suggests that they occupied primarily freshwater habitats. Transported
Prototaxites
and
Spongiophyton
, both interpreted as possible fungi, are the main components of fully non-marine channel deposits. It is no coincidence that the best-preserved plants are those that lived in moist, oxygen-poor settings. However, the occurrence of root traces in palaeosols and sparse fossil evidence suggests that embryophytes also occupied drier settings.
Initiation and early development of the Dingle Basin, SW Ireland, in the context of the closure of the Iapetus Ocean
Authors: Boyd J. Douglas , Sloan Roderick J. 
Published: April 2008

Abstract
The Dingle Basin of southwest Ireland lies within 40 km of the present-day trace of the Iapetus Suture. Its late Silurian fill (Dunquin Group and lower Dingle Group) is an important and, in many aspects, unique record of late Caledonian development in the Irish and British sector of the orogen. The upper Wenlock-upper Ludlow Dunquin Group comprises shallow-marine to non-marine siliciclastic and volcanic rocks (acid pyroclastic deposits and predominantly andesitic lavas) deposited on and around a volcanic island(s), whereas the lower, upper Ludlow-Přídolí, part of the overlying Dingle Group comprises sandstones, mudstones and minor conglomerates deposited in lacustrine, lake margin and succeeding fluvival systems. The change from marine Dunquin Group to non-marine Dingle Group (Old Red Sandstone) sedimentation is interpreted to have been tectonically driven. The succession is interpreted in terms of four phases of basin evolution: (1) a phase related to active subduction; (2) a phase related to subduction termination; (3) a post-subduction thermal subsidence phase; (4) a phase of strike-slip fault-controlled subsidence. In the broader, late-Caledonian context, the Dunquin Group volcanic rocks and associated sediments are interpreted as representing localized subduction of a final vestigial portion of Iapetus oceanic crust. The later, inferred, strike-slip influence in the basin is believed to be part of the well-documented regional strike-slip regime affecting this sector of the Caledonides.
A new terrane in the Old Red Sandstone of the Dingle Peninsula, SW Ireland
Authors: Richmond Lorna K. , Williams Brian P. J. 
Published: April 2008

Abstract
We propose the name Northwest Dingle Domain for the enigmatic Old Red Sandstone terrane whose tectono-sedimentary evolution has perplexed generations of geologists. The Domain remained largely misinterpreted, unappraised or simply disregarded, and its fundamental impact on regional basin dynamics was grossly overlooked. The Northwest Dingle Domain is largely structurally constrained between two ENE-trending Caledonian structures: the North Kerry Lineament and the Fohernamanagh Fault. It comprises four unconformity-bounded Groups: the Lower Devonian Smerwick Group; the Middle Devonian Pointagare Group; and the Upper Devonian Carrigduff and Ballyroe Groups. Their fluvial-aeolian, and locally tidal, sedimentation patterns profile Late Caledonian transpression to Mid-Late Devonian extension. The inherent primary structural control on basin location, development, geometry, sedimentary-fill and preservation is manifest in the Northwest Dingle Domain. The Acadian emplacement of the Smerwick Group set the foundations of the Northwest Dingle Domain. The Smerwick Group documents sandy and gravelliferous ephemeral-fluvial and erg-margin aeolian processes on an ancient terminal fan(s). The Pointagare Group is cogenetic with the Caherbla Group of south Dingle. Together they record the renewed influx of coarse-grained sediment in the form of transverse alluvial fans and axial braidplains in response to increased tectonism followed by overstep of an erg complex. The Pointagare-Caherbla basin model highlights the fundamental structural control on basin topography, palaeodrainage patterns, provenance, palaeowind directions and sedimentation style in tectonically-active extensional basins.
Wide-angle seismic control on the development of the Munster Basin, SW Ireland
Authors: Vermeulen N. J. , Shannon P. M. , Masson F. , Landes M. 
Published: April 2008

Abstract

Three wide-angle seismic profiles were acquired from onshore southern Ireland during VARNET-96. These data provide the only subsurface seismic images of a series of predominantly Late Palaeozoic sedimentary basins. The Dingle Basin is a broadly symmetrical rift on the Dingle peninsula, but assumes a half-graben geometry to the east. The southern syn-rift basin margin is defined by the north-dipping Dingle Bay-Galtee Mountains Line. A south-dipping normal fault at Kerry Head marks the northern basin margin in the west, with displacement on this structure decreasing towards the east. The Dingle Basin is separated from the Munster Basin to the south by a basement horst. Seismic data strongly suggest that the Killarney-Mallow Fault Zone, located on the southern margin of this positive feature, is the Munster Basin northern syn-rift marginal fault. The preserved extensional displacement on this detachment decreases from
c.
2.5 km in northern Iveragh, to
c.
1 km at Mallow, suggesting that the fault tips out to the east of Mallow. A tilted fault block, possibly cored by shallow granite, is imaged in the northern Munster Basin. This fault terrace is bounded to the south by the Cork-Kenmare Line. The combined Munster Basin and South Munster Basin succession thickens across the Cork-Kenmare Line to a maximum thickness of 8 km on the Beara peninsula. A tectonic thickness of 6 km of sediment is modelled at the Old Head of Kinsale, increasing to 7 km in the southwest.
Flexural cantilever models of extensional subsidence in the Munster Basin (SW Ireland) and Old Red Sandstone fluvial dispersal systems
Authors: Williams E. A. 
Published: April 2008

Abstract

Flexural cantilever (2D) computer modelling of the palinspastically restored Mid-Late Devonian Munster Basin has been used to appraise quantitatively extensional subsidence and Old Red Sandstone (ORS) stratigraphic geometries. One-dimensional decompaction and (Airy isostatic) backstripping were carried out to constrain syn-rift forward models; these specify the Late Palaeozoic rifting history of the region. Forward modelling showed that listric faults and detachments fail to reproduce restored ORS sediment geometries, but instead indicated that multiple planar, upper-crustal faults are necessary to achieve the correct order of syn-rift subsidence across the basin. Modelled (non-unique) sections transverse to the basin bounding fault (Dingle Bay-Galtree Fault Zone) replicated ORS geometries with cumulative extensions of 27 km in the east (stretching factor β = 1.3) and 59 km in the west (β = 1.48), with effective elastic thicknesses of 7 and 8 km, respectively, starting from a 40 km thick post-Acadian crust. Resultant peak heat-flow anomalies predict well the location of known syn-rift volcano-magmatic centres. Modelling indicated that significant offshore faults are required to achieve subsidence in the west Cork region, implying that the basin continues offshore. Observed ORS (<0.85 km thick) sections on the regional footwall, considered to be the result of thermal (post-rift) subsidence, are not accounted for by modelling, whereas
c
. 1 km of post-rift ORS is modelled over 5 Ma in the central-southern regions of the basin. These sections buried the principal rift faults during late Famennian time. The ORS of the Munster Basin is dominated by two large-scale transverse fluvial dispersal systems that were largely insensitive to deflection by any extension faults that propagated in the syn-rift fill. A third major system entered in the SW, demarcated by antithetic extension faults south of the depocentre.
U-Pb zircon geochronology of silicic tuffs and chronostratigraphy of the earliest Old Red Sandstone in the Munster Basin, SW Ireland
Authors: Williams E. A. , Sergeev S. A. , Stössel I. , Ford M. , Higgs K. T. 
Published: April 2008

Abstract

Newly acquired U-Pb magmatic zircon dates from silicic tuffs within the Old Red Sandstone (ORS) magnafacies of the Munster Basin (SW Ireland) are intercalibrated with newly discovered (late Givetian) and reappraised (mid-Frasnian) miospore assemblages to provide the first biostratigraphically constrained numerical ages in the Irish Devonian succession. The weighted mean
207
Pb/
206
Pb isotopic age determined for the Keel Tuff Bed (385.0±2.9 Ma) is indistinguishable from that of the previously investigated Enagh Tuff Bed (384.9±0.7 Ma). In conjunction with very similar rare earth element (REE) signatures, this confirms their correlation, placing a minimum age of 384.9±0.4 Ma on the newly discovered Reenagaveen microflora, which is assigned to the late Givetian TCo Oppel zone. The equivalence of the Keel and Enagh Tuffs constrains a vertebrate fauna containing
Bothriolepis
and the Valentia Island tetrapod ichnofauna to pre-date this event. Isotopic dating of thickly bedded subaerial tuffs from the Lough Guitane Volcanic Complex, a major accumulation of rhyolites and silicic volcaniclastic rocks, reveals ages of 384.5 ± 1.0 Ma (Killeen Volcanic Centre), indistinguishable from the Keel-Enagh Tuff Bed, and 378.5±0.2 Ma from the Horses Glen Volcanic Centre, previously considered to be the oldest of the complex. The Horses Glen Centre post-dates the Moll’s Gap Quarry microflora, the only current biostratigraphical control on the age of the early ORS in the east of the basin depocentre, thus indicating a minimum age for the (mid-Frasnian) IV Oppel zone, the revised biostratigraphic age of this assemblage. These controls on the early ORS (1) suggest that Munster Basin initiation occurred before late Givetian time and (2) give time-averaged (compacted) accumulation rates of
c.
0.17–0.25 and 0.18 mm a
−1
for eastern and western Iveragh, respectively. The minimum basin duration time was
c.
23 Ma to the end of the Devonian period. The implications of these data for the depocentre stratigraphy, volcanic events, proposed ORS cyclicities and the geohistory of the Munster Basin are examined.
Controls on magmatism in the Munster Basin, SW Ireland
Authors: Pracht M. 
Published: April 2008

Abstract
The following paper is intended as a review of the magmatism in the Munster Basin and an initial attempt to link it with the basin’s history. During the initiation, evolution and inversion of the Devono-Carboniferous Munster Basin magmatic activity was widespread, although small in volume. The episodic occurrence and diversity of the magmatism gives insights into the basement involvement and structural controls relating to the basin’s history. The differences in composition, location and structural relationship of the magmatic bodies are used as indicators for the timing of their emplacement and their relationship to the basin’s evolution. On the western Beara Peninsula in SW Ireland alone, more than 160 sheet-like intrusions, a wide variety of tuff bands and a deep-seated pipe-like structure of lamprophyric affinity occur. Other centres of magmatism in the basin are the Lough Guitane area, where rhyolitic lava flows and acidic pyroclastic rocks are associated with contemporaneous basin faults, and the Valentia Harbour area, where doleritic sills are associated with a volcanic breccia. A rhyodacitic tuff can be traced as far as St Finan’s Bay on the western shore of the Iveragh Peninsula. The chemical composition of the extrusive and intrusive magmatic bodies ranges from tholeiitic dolerites (Valentia Harbour) and subalkaline rhyolites (Lough Guitane) in Mid-Devonian time to subalkaline basalts and tuffs (e.g. Beara Peninsula) in Late Devonian time. In Late Carboniferous and possibly Permian time alkali basalts, trachytes and phonolites (e.g. Beara Peninsula) occur. The igneous activity in the Munster Basin is linked to the basin’s history by the interaction between active faults and fractures opening up during various stages of stress imposed on the basin and exploitation of these faults and fractures by rising magma.
Silurian marginal marine sedimentation and the anatomy of the marine-Old Red Sandstone transition in Pembrokeshire, SW Wales
Authors: Hillier Robert D. 
Published: April 2008

Abstract
Deposition of the Silurian (Wenlock) siliciclastic Gray Sandstone Group of southwest Pembrokeshire took place within littoral environments close to the palaeogeographical shelf-margin of the Welsh Basin. Sedimentation described a northerly, basinward progradation across an earlier Late Ordovician? to Aeronian rift basin. Changes in relative sea level (rsl) had profound effects on depositional environments, and five depositional sequences are recognized. During highstands of rsl, the area was influenced by wave-dominated, shallow-marine conditions. During lowstands of rsl, shelf incision and sediment bypass occurred. Associated valley fills vary in nature from high-sinuosity estuarine channels, tidal flats and tidally-influenced, high-sinuosity fluvial channels. The last of these predominate within the youngest sequence, with abundant subaerial emergence indicators heralding the onset of true continental deposition, and the conformable transition into the overlying Old Red Sandstone Red Cliff Formation within the Marloes Peninsula. A renewal of tectonic activity ensued within the Lower Old Red Sandstone, with pebbly low-sinuosity alluvium of the Albion Sands Formation, and fanglomerates of the Lindsway Bay Formation refecting reactivation of earlier rift-margin faults, probably within a transtensional tectonic regime.
Fault-bounded basin fill: fluvial response to tectonic controls in the Skrinkle Sandstones of SW Pembrokeshire, Wales
Authors: Marshall J. D. 
Published: April 2008

Abstract
The Upper Devonian to Lower Carboniferous Skrinkle Sandstones of the Pembroke Peninsula are predominantly continental deposits from the post-Caledonian syn-rift succession at the southern margin of the Late Palaeozoic Welsh Landmass. The Sandstones record deposition in the 30 km × 10 km Tenby-Angle fault block, the southernmost of a series of fault-bounded depositional basins in SW Dyfed. Activity on the bounding faults strongly influenced sedimentation through Lower Palaeozoic time. The Skrinkle Sandstones are conventionally assigned to a phase of relative fault inactivity, passive transgression of the area and southward drainage off the landmass. The Ritec Fault at the northern block boundary defined a temporary shoreline during final submergence. In contrast to this, it is argued that the lower half of the Skrinkle Sandstones represent a separate structural configuration, where SE-directed palaeocurrents and the high textural maturity of two superimposed basin-fill sequences indicate axial basin fill and potential closure to the south. The upper half records an influx of immature clastic deposits as fluvial sediments that disperse to the southwest, indicating relative uplift of either the Ritec or a more northerly fault. This phase records the true transgression, during which a thick barrier-lagoon coastline is preserved against the footwall ramp of the Ritec Fault.
Palaeoecology and plant succession in a borehole through the Rhynie cherts, Lower Old Red Sandstone, Scotland
Authors: Powell Clare L. , Trewin Nigel H. , Edwards Dianne 
Published: April 2008

Abstract

A cored borehole through the Early Devonian Rhynie cherts at Rhynie, Aberdeenshire, NE Scotland, has revealed 53 chert beds in 35.41 m of core. The cherts originated as sinters deposited by hot-spring activity. Chert comprises 4.20 m of the cored succession, with the thickest bed, representing a single silicification event, being 0.31 m thick and the thickest composite chert (comprising six beds) 0.76 m thick. Average chert bed thickness is 80 mm. Forty-five plant-bearing chert beds are interbedded with sandstones, mudstones and shales. The sediments were deposited on an alluvial plain with local lakes, the area being periodically affected by hot-spring activity. Plants initially colonized both subaerial sand and sinter surfaces.
Rhynia gwynne-vaughanii
and
Horneophyton lignieri
commonly form the basal parts of the profiles with subsequent colonization by other genera.
Rhynia
is commonly found in life position above originally sandy substrates, and
Horneophyton
above sinter surfaces. The composition of the Rhynie vegetation is compared with coeval assemblages and, on the basis of current knowledge, it is concluded that there is no unequivocal evidence that the plants were adapted to life in the stressed environments in the immediate vicinity of hot springs.
Devonian (Givetian) miospores from the Walls Group, Shetland
Authors: Marshall J. E. A. 
Published: April 2008

Abstract
Miospores demonstrate that the Walls Group of West Shetland is of early and possibly in part late Givetian age (Late Mid-Devonian age). This is both substantially younger in age and of a shorter duration than previously estimated. The correlative rocks of the Walls Group are those of southeast Shetland, Fair Isle, the Eday Group of Orkney and the John O’Groats Sandstone Group of Caithness. The two formations of the Walls Group are, at least in part, time equivalent rather than a stacked sequence. The total thickness of sediment is likely to be much less than the generally cited 12 km, given the short time duration represented by the single miospore assemblage identified throughout the succession. The low diversity of the miospore assemblage and its fluctuating dominant species is interpreted as reflecting a local vegetation source in a low preservation environment. The age and thermal maturity contrast between the Walls Group and the sedimentary successions to the west (Melby, Papa Stour and Foula) provide further constraints on the movement history along the St Magnus Bay Fault system.
Fossils from the Celsius Bjerg Group, Late Devonian sequence, East Greenland; significance and sedimentological distribution
Authors: Clack J. A. , Neininger S. L. 
Published: April 2008

AbstractRecent collections of fossils from the Upper Devonian sequence of East Greenland have increased our understanding of the origin and evolution of limbed vertebrates (tetrapods). An expedition in 1998 collected additional material to study the faunal and sedmentological context of the vertebrates from the Celsius Bjerg Group. Specimens collected include new, articulated material of ichthyostegids, a skull of the lungfishJarvikiaand the first record of acanthodian spines and scales. Invertebrates were found in these formations for the first time. Vertebrates occur most often in flood-scours, transported from elsewhere and usually disarticulated. Occasionally, more complete specimens occur, which may have been either desiccated before transport or come from more local environments.
Climatic oscillations versus environmental changes in the interpretation of Tertiary plant assemblages
Authors: Kvaček Zlatko 
Published: April 2008

Abstract
Zonal plant communities are the best climatic indicators because they thrive under specific climatic conditions. However, palaeoclimatic estimates based on mere comparisons of local fossil plant assemblages, even if assessed by multivariate methods, may be misleading, if the taphonomical bias is neglected. The fossil record expresses only limited parts of the vegetation of a given period. The example of the Lower Miocene section at Bílina, North Bohemian Basin, shows how quickly the composition of the plant megafossil record changes as a result of different environmental factors and sedimentary settings. These changes can imitate climatic oscillation because swamp, fluvial and upland facies represented within this site have different vegetation-palaeoclimatic aspects. On the other hand, if one compares two assemblages originating from the same sedimentary and environmental setting (preferably mesophytic conditions), the resulting palaeoclimatic changes can be estimated more safely. Two local assemblages from the Oligocene volcanic area of the České středohoří Mts in North Bohemia are of mesophytic character. Both are embedded in diatomites deposited in crater-maar lakes. The assemblage of Suletice (20–29 Ma), with prevailing thermophilous elements, indicates more warm-temperate conditions, whereas the assemblage of Bechlejovice (27 Ma), composed mostly of deciduous broad-leaved trees and shrubs, corresponds to a temperate climate. Thus, together, these two floral assemblages suggest that a climatic oscillation occurred within Late Oligocene time in Central Europe.