bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Variscan lower continental crust: evidence for crustal delamination from geochemical and petrophysical investigations
Authors: Wittenberg A. , Vellmer C. , Kern H. , Mengel K. 
Published: April 2008

Abstract

Seismic observations along the European Geotraverse (EGT) Central Segment indicate an overall felsic composition of the Variscan crust, including 15 vol. % of mafic lower-crustal (MLC) rocks. As the Variscan continental crust is largely post-Archaean, its bulk composition should be basaltic andesitic rather than felsic (tonalitic), because primitive post-Archaean crust was formed by mantle extracted basaltic andesite magmas. The observed proportions of the Variscan continental crustal layers do not match the requirement of a mafic overall crust. Combining laboratory-derived,
in situ
seismic data (
V
P
) with the refraction seismic data and the evidence from geological and geochemical investigations suggests that large amounts of MLC rocks are missing in the present-day lower crust. A mass balance calculation of the basaltic andesite bulk crust, considering a refined compilation of the Variscan MLC, gives a volume proportion of 37 vol. % for the felsic and 63 vol. % for the mafic components, for primitive crust prior to collision tectonics and orogenic root delamination. If large parts of this MLC have undergone eclogite-facies metamorphism at the orogenic root, large amounts of former basaltic-gabbroic and MLC cumulates could have been subtracted from the crust by its subsequent delamination processes which results in the currently observed proportion of the continental crust of the Variscan Orogen with a predominance of felsic rocks.
Chronostratigraphic framework for the Devonian and Old Red Sandstone
Authors: House Michael R. 
Published: April 2008

Abstract
Boundaries for all the Devonian series and stages have now been proposed by the Subcommission on Devonian Stratigraphy (SDS) of the International Commission on Stratigraphy (ICS) and have been ratified by the International Union of Geological Sciences (IUGS). A summary of these decisions is given. All the defined Global Stratigraphic Section and Points (GSSPs) are in the marine realm, and in pelagic facies. Much work is still needed to correlate the new boundaries into neritic and terrestrial facies.
Kinematics and dynamics of Old Red Sandstone basins
Authors: Friend P. F. , Williams B. P. J. , Ford M. , Williams E. A. 
Published: April 2008

AbstractThe Old Red Sandstone basins of the North Atlantic borderlands provide a record of diverse dynamics in very different settings, related to the Variscan, Caledonian and Ellesmerian orogenies. This paper is a first attempt to review much new information on the basins, including information presented, for the first time, in this book. Five basin groupings are distinguished: (1) Scandinavian basins of, syn- to post-Scandian (Caledonian) age, formed on greatly thickened crust by extension or transtension (Western Norway, East Greenland, Spitsbergen); (2) NE Scotland, Orcadian Basin, mid Caledonian setting, formed by extension; (3) Scotland (Midland Valley) and related Irish basins, north of the Caledonian Iapetus Suture Zone, formed by extension; (4) southern Britain and Ireland, basins south of the Iapetus Suture Zone, related to collision of Eastern Avalonia with Laurentia, and Maritime Canada and the Catskills related to collision of Western Avalonia; these are load-induced flexural basins; (5) Southern margin of Eastern Avalonia, (Munster, South Wales, SW England), of Late Devonian age, extensional basins of various (Early to Late) Devonian ages.
The geometry, flow patterns and sedimentary processes of Devonian rivers and coasts, New York and Pennsylvania, USA
Authors: Bridge John S. 
Published: April 2008

AbstractThe Middle-Upper Devonian strata of New York and Pennsylvania were deposited in a foreland basin adjacent to the Acadian fold-thrust belt. Fluvial (Catskill) strata in the east thin to the west into marine (Chemung) strata. The overall sequence is marine regressive, but there numerous superimposed marine transgressions. The Catskill river channels changed character with distance from the palaeoshoreline. Sinuous, single-channel rivers (widths tens of metres, maximum bankfull depths 4–5 m, sinuosity 1.1–1.3, mean bankfull flow velocity 0.4–0.7 m s−1) occurred near the coast. With increasing distance from the coast, rivers increased in slope, became wider (up to hundreds of metres) and deeper (up to 15 m), coarser grained, and possibly braided. This suggests that rivers were distributive near the coast. Furthermore, muddy floodplain areas were more extensive near the coast than up-valley, such that the proportion of channel deposits increased up-valley. Coastal areas comprised tide-influenced channels and mouth bars, wave-influenced sandy shoals and washovers, sandy and muddy tidal flats, and muddy interdistributary bays and lakes. Major marine transgressions are thus represented in wholly fluvial successions by a decrease in the proportion of channel sandstone bodies, and a decrease in channel size and grain size. Marine transgressions in near-coastal successions are represented in places by an increase in sandstone proportion associated with progradation of coastal sands over muddy backswamps and interdistributary areas. Small-scale marine transgressions and regressions in coastal deposits (i.e. metres-thick parasequences) are probably associated with switching of coastal channels or delta lobes. There is no evidence for the preservation of incised valleys, nor for any changes in coastal channel patterns associated with these parasequences: therefore, major regional sea-level changes were not responsible. However, large-scale (tens to hundreds of metres) transgressive-regressive sequences were due partly to eustatic sea-level change (e.g. in mid-Givetian time) but also due to changes in the balance between sediment supply and subsidence associated with tectonic uplift of the hinterland and peripheral bulge. Such uplift may have induced some kind of climate change. However, climate changes in the depositional basin are not supported by sedimentological evidence. Further understanding of the origin of these strata will require higher precision in the biostratigraphic correlation of marine and non-marine strata (using miospores), and quantitative interpretation of depositional environments from other regions.
Taking the roof off a suture zone: basin setting and provenance of conglomerates in the ORS Dingle Basin of SW Ireland
Authors: Todd Simon P. 
Published: April 2008

Abstract

The Late Silurian to Mid-Devonian Dingle Basin occupies a central position within the Iapetus Suture Zone of SW Ireland. The basin is believed to have formed from late Silurian times onwards as a product of sinistral transpression along several major faults within this suture zone. Conglomeratic sediments were deposited by moderately large gravelly fans shed into the basin from the NW (Glashabeg Formation) and the SE (Trabeg Conglomerate Formation). The systems fed into a large apparently through-going sandy, axial river (Slea Head Formation) that flowed towards the NE. The lateral, basin-margin systems were sourced from two disparate source terranes. To the NW lay a basic volcanic hinterland with some intermediate volcanic rocks and limestones, mudstones, sandstones and chert. During the Early Devonian time the SE drainage basin was underlain by sandstones, quartzites, phyllites and limestones probably intruded by a granite. Some of these lithologies can be found in outcrop in the pre-Dingle Group of the peninsula. Others need to be correlated with rocks of the oceanic terranes in the northern part of the suture zone. The southerly derived clasts have corollaries in the rocks of the Avalonian Leinster Terrane south of the suture. Following partial inversion of the Dingle Basin, the southerly hinterland was apparently further unroofed during mid-Devonian time, when the Inch Conglomerate Formation was deposited by alluvial fans shed northwards from a source area formed along the Dingle Bay Lineament. The Inch conglomerates are characterized by distinctive clasts of schist, gneiss, mylonite, tourmalinite and granite. The general picture of the Early Devonian deformation, intrusion by granite and unroofing of terranes currently partially exposed in central and southern Ireland within the Iapetus Suture Zone is largely consistent with clast lithotypes. However, some exploratory isotopic data indicate at least two possible vagaries in the interpretation. First, model ND
T
DM
ages of Trabeg sedimentary clasts yield several results older than typical southern Iapetean or Avalonian crustal material. This suggests a complex history of sedimentary mixing of material across the developing Iapetus Ocean. Second, two of three Rb-Sr muscovite-whole-rock dates of Inch metamorphic clasts indicate Silurian ages. These data similar to Rb-Sr dates derived from the Carnsore and Saltees granites in the Rosslare Terrane, perhaps extending the geographical spread of this Silurian deformation.
Progress in reconstructing vegetation on the Old Red Sandstone Continent: two
Emphanisporites
producers from the Lochkovian sequence of the Welsh Borderland
Authors: Edwards Dianne , Richardson John B. 
Published: April 2008

Abstract

Small coalified fossils (mesofossils) have yielded new insights into vegetation of the Old Red Sandstone Continent in early Devonian times. Particularly useful are those containing spores that can be placed in dispersed spore taxa, although patinate and emphanoid spores have not hitherto been found
in situ. Emphanisporites
cf.
micrornatus
Richardson & Lister is described in a bifurcating cylindrical sporangium preserved as a cuticular sheath. A terminal dehiscence feature is compared with that in
Horneophyton
. The sporangium is encased in amorphous detritus with some tubular fragments. Similar associations occur on other sporangia, e.g.
Tortilicaulis
and axes at this North Brown Clee Hill locality, and they are interpreted as remains of a microbial or fungal film. Fragmentary cuticles, interpreted as isolated sporangial valves, bear an undescribed species of
Emphanisporites
with fine interdigitating proximal muri and laevigate distal surfaces referred to
Emphanisporites
sp. A Richardson & Lister. Analysis of dispersed spore assemblages from the locality and others in the Welsh Borderland indicate that the two emphanoid taxa were not common components of the spore ‘rain’. This evidence, coupled with the dearth of mesofossils of the producers, suggests that the plants grew at the upper reaches of the drainage basin of the river that deposited the sediment, although the paucity of sporangia may also be attributed to their low fossilization potential.
Depositional setting of the Lower Old Red Sandstone at Pantymaes Quarry, central South Wales: new perspectives on the significance and occurrence of ‘Senni Beds’ facies
Authors: Owen Geraint , Hawley Duncan 
Published: April 2008

Abstract
The 200 m long face of Pantymaes Quarry, central South Wales, exposes part of the upper (Dittonian) Red Marl Group (Lower Old Red Sandstone). A lower Sandstone Facies Association (up to 15 m thick) comprises interbedded grey-green micaceous sandstones, pebbly intraformational conglomerates, and grey siltstones. Major bounding surfaces define stacked channel complexes, representing the deposits of braided river systems. An erosively overlying Mudstone Facies Association (up to 15 m thick) comprises tabular-bedded, bioturbated and calcretized red siltstones and fine sandstones representing overbank deposits, possibly from a meandering system. The change in fluvial style is interpreted as a local response to pulses of oblique-slip movement on nearby fault systems. The period of fault activity resulted in the braided Sandstone Facies Association, the Mudstone Facies Association recording a gradual return to a meandering system. Individual pulses of activity produced the stacked channels within the Sandstone Facies Association. The Sandstone Facies Association is similar in character to the overlying Senni Beds, suggesting that ‘Senni Beds’ may describe a recurring, possibly tectonically controlled, braided channel facies in the Lower Old Red Sandstone.
Old Red Sandstone basins and alluvial systems of Midland Scotland
Authors: Bluck B. J. 
Published: April 2008

Abstract
Old Red Sandstone rocks of the Midland Valley of Scotland record the amalgamation history of blocks widely separated from each other in Ordovician times. As a response to the lateral juxtaposition of the Midland Valley against the Highland block, the Midland Valley, weakened during its long history of igneous activity, was subjected to transtension and transpression, which opened and closed basins resulting in much recycling of sediment and the renewed development of intermittent and sometimes prolific volcanic activity. The Old Red Sandstone comprises two cycles of basin fill: the older (the Lower Old Red Sandstone) is separated by a major unconformity from the younger (the Upper Old Red Sandstone). Each cycle begins with conglomeratic sedimentation in pull-apart basins then fines and petrographically matures upward. The cycles, initiated by faulting, record the decline in tectonic influence and the concomitant reduction in source relief. The sediment source to the Old Red Sandstone is enigmatic. The Dalradian basement to the north and Southern Uplands to the south were, in many places, extensively eroded by Late Silurian-Early Devonian times. The thickest sequence of coarse sediment in the UK, if not in Europe, therefore has no obvious nearby uplift to provide both the sediment and the persistent, substantial slopes required to deliver sediment of that calibre to the basin. To the northeast, the Greenland-Baltica collision had created a major Silurian-Carboniferous (Scandian) uplift. Major river systems draining this mountain belt entered the Lower and Upper Old Red Sandstone basins at a late stage in their development when relief was lowered sufficiently to allow access to them.
Age and provenance of limestone clasts in Lower Old Red Sandstone conglomerates: implications for the geological history of the Midland Valley Terrane
Authors: Armstrong Howard A. , Owen Alan W. 
Published: April 2008

Abstract

Conodont-bearing limestone clasts in Lower Old Red Sandstone conglomerates in the Lanark and Strathmore basins and the Pentland Hills Inlier, Midland Valley, Scotland, indicate a source in a cryptic arc terrane with a mid-Ordovician (
P. serra-P. anserinus
Biozone) limestone cover. Simpson coefficients of similarity indicate that the faunas from the limestone clasts are closer to conodont faunas from the Holy Cross Mountains, Poland, and the Wrae Limestone in the Northern Belt of the Southern Uplands, than to those in coeval strata from the Laurentian margin including Girvan. Conodont colour alteration index values indicate separate thermal histories for the limestone clasts and coeval strata in the Girvan Inlier. The cryptic arc was located to north of the Northern Belt of the Southern Uplands during Ashgill time and to south of the Midland Valley in Late Silurian-Early Devonian time and clearly had a complex tectonic history.
Calcrete morphology and karst development in the Upper Old Red Sandstone at Milton Ness, Scotland
Authors: Balin Donna F. 
Published: April 2008

Abstract
The Upper Old Red Sandstone at Milton Ness, Scotland, is notable for its excellent preservation of calcrete textures, which are comparable with some of the best Quaternary examples. It is also significant for the implications that can be drawn from the association between karst and calcrete, with this example interpreted to have formed entirely within a semi-arid environment. Karst cavities were developed in a mature hardpan calcrete, generated in sandy fluvial sediments with associated aeolian deposits. Subsequent to karst cavity generation, clasts derived from the subaerially exposed hardpan were locally transported and deposited as a laterally traceable bed connecting the tops of all the cavities. Both this bed and the karst infills were subsequently recalcretized in the final phase of the profile’s evolution. Although calcrete-karst associations often are interpreted as the alternation between semi-arid and humid climates, respectively, this example is interpreted to be a result of water accumulating on the nearly impervious hardpan surface under fairly constant semiarid conditions, evidenced by the recalcretization of both the karst infill and the calcrete-derived breccia (‘boulder calcrete’). Additional substrate modification also has taken place by plant roots; the remarkable development of rhizoliths in these Old Red Sandstone sediments should emphasize the need to consider plant influence on other non-marine rocks of post-Silurian age.
Early syndepositional tectonics of East Greenland’s Old Red Sandstone basin
Authors: Hartz Ebbe 
Published: April 2008

AbstractEast Greenland’s Old Red Sandstone basin formed in the interior of a megacontinent created by the Caledonian collision of Baltica and Laurentia. The basin has been regarded as a typical late- to post-orogenic extensional basin, formed in a collapsing orogen. Cross-cutting faults that have extended the basin substrata have been explained as Riedel and anti-Riedel shears that formed during basin initiation, but no detailed structural analysis has been presented. Analysis of geometrical relationships between faults and folds, and their relative timing with respect to the syn-tectonic deposits suggest a new model for basin evolution. In eastern Greenland, orogenic collapse was initiated at least as early asc.425 Ma. Thus, the preserved Devonian basins formed afterc.70 Ma of large-magnitude crustal extension. Thick successions of Mid-Devonian Old Red Sandstone were deposited in troughs controlled by orogen-parallel extension and east-west folding. Later north-south-trending extensional structures cut the basal deposits, as episodes of folding continued until Permian time. Folding continued forc.175 Ma after the Caledonian continent-continent collision and it is thus unrealistic to suggest that internal Caledonian forces caused these ‘late Caledonian spasms’. However, the collapsed orogen may have been thermally weakened, and the region was thus probably vulnerable to external forces resulting from the continuing orogenies along the rim of the megacontinent.
Deformation of the Old Red Sandstone of NW Spitsbergen; links to the Ellesmerian and Caledonian orogenies
Authors: McCann Andrew J. 
Published: April 2008

Abstract
The Late Silurian?-Devonian fluvial deposits of northern Spitsbergen were deposited on basement with Caledonian and earlier metamorphic ages in which two distinct terranes are recognized (Biskayerhalvøya and Krossfjorden). These form part of the central of three major terranes in Svalbard, assembled during the Caledonian Orogeny. The subsequent geological history of the Svalbard area has been strongly influenced by the north-trending structures which were active as transcurrent fault zones at this time. The unconformable base of the Siktefjellet Group, a Late Silurian?-earliest Devonian sequence of coarse conglomerates and breccias, overlain by fluvial sandstones, is preserved only on the Biskayerhalvøya terrane, and the final juxtaposition of the two terranes (during the Haakonian sinistral strike-slip phase) is interpreted to post-date the deposition of these sediments. The Lochkovian Red Bay Group, a sequence of conglomerates, fluvial sandstones and siltstones, was deposited on both terranes. This has been mapped and correlated throughout the basin exposure, allowing the reconstruction of the tectonic history. Sedimentation was influenced by active faulting during deposition of the oldest Wulffberget Formation, but subsequent deposits show little evidence of this. Deposition was interrupted in latest Lochkovian time by renewed sinistral strike-slip faulting, which broke up an area of the basin into rotating fault blocks, across which about 30 km of extension occurred. This was followed by east-west shortening, which uplifted the Red Bay basin and underlying basement, developing large folds, locally with related thrusting. The Monacobreen phase is defined to involve this deformation. The Andr0.000000e+00e Land Group reflects a subsequent renewal of subsidence, and re-establishment of an extensive fluvial basin, occupying an area east of the inverted Red Bay basin. Conglomeratic units that overlie the Red Bay Group are interpreted as the products of the reworking of the uplifted Red Bay basin and its basement. The Latest Devonian-Earliest Carboniferous Svalbardian phase again involved east-west shortening, with limited strike-slip faulting, but it is difficult to discriminate these effects from the Monacobreen phase in the Siktefjellet and Red Bay groups. A review of North Atlantic and Arctic Devonian basins shows that during deposition of the Red Bay and Andrée Land groups, the tectonics of Svalbard was more similar to that of the developing Ellesmerian orogen, than to that of the collapsing Caledonian orogen. A model is proposed that links the repeated extension and shortening seen from Early Devonian time in north Spitsbergen to anticlockwise rotation of the Chukotka-Alaska plate, about an axis near the position of Svalbard during Ellesmerian collision, coupled with minor Caledonian-related strike-slip movement along reactivated fault zones.
Lamination and primary production in fossil lakes: relationship to palaeoclimate in the Carboniferous-Permian transition
Authors: Clausing Andreas , Boy Jürgen A. 
Published: April 2008

Abstract
Comparative studies are made on the development of lamination in Recent, Paleogene and Permian lake sediments. The study concentrates on the relationship between primary production and lamina formation. The main phytoplankton development in lakes is correlated with environmental changes and it is often preserved in the lamination in chronological succession. Seasonal patterns may be especially represented. Morphological identification and classification of laminities is achieved by studies of Recent lake sediments. This leads to possible comparison, even in badly preserved ancient examples. Paleogene lamination can be clearly correlated with the Recent lamination by the relatively tenuous relationships of the phytoplankton. Permian lake sediments, however, are difficult to decipher, as the phytoplankton species are different or absent as a result of taphonomy. Nevertheless, morphological comparisons suggest periodic sedimentation and lamination development that is clearly similar to that in lakes today. As the same physical properties apply, this seasonal sedimentation can also be used as an additional tool for the reconstruction of environmental and climatic changes in the Carboniferous-Permain boundary strata.