bluuebunny/crossref_metadata_2025_split huggingface dataset:
The kinematic evolution of the Coffee Soil Fault
Authors: Cartwright Joseph 
Published: April 2008

Abstract
This paper addresses the problem of the dating of motion on large, extensional faults, from the seismic expression of the sedimentary sequences deposited during and after the extensional deformation. A general discussion of the interpretational methods and pitfalls involved in a seismically based, kinematic analysis is made by reference to a case study of the Coffee Soil Fault. The Coffee Soil Fault forms the eastern boundary of the Central Graben of the North Sea Rift, and is located in the Danish Sector. From a comparison of the stratigraphy of the hanging wall and footwall blocks, it is suggested that rifting commenced in the Late Permian/Early Triassic. The rifting proceeded in two distinct phases, a non-rotational Triassic phase, resulting in parallel reflection configurations, and a rotational Mid-Late Jurassic phase, resulting in divergent reflection configurations. Basin-floor and fault-scarp relief that resulted from a Late Jurassic acceleration of motion across the fault was infilled in a parallel-onlap configuration by the post-rift Lower Cretaceous sequence. The case study is used to demonstrate that onlap of remnant fault scarps can easily be mistaken for syn-rift deposition, and that this can lead to considerable errors in the timing of the end of rifting.
Extensional structures and their tectonic inversion in the Western Alps
Authors: Coward M. P. , Gillcrist R. , Trudgill B. 
Published: April 2008

Abstract
During Alpine collision the western margin of Tethys was uplifted on large-scale thrust zones, to preserve and give excellent 3D exposures of Mesozoic fault geometries. The faults are particularly well exposed along the margins of the Belledonne and Pelvoux basement massifs, east of Grenoble. Jurassic normal faults were in places reworked and the basins partially inverted during Cretaceous to Miocene compression. They were subsequently locally reworked by an important phase of late Alpine extension.
Both listric and straight (rotational) normal faults occur in Variscan granitic basement and Mesozoic cover. Several orders of synthetic and antithetic faults can be mapped, recording strains which are probably related to bends or kinks in the surfaces of the master faults. The extension directions vary, apparently related to variations in anisotropy of the Variscan basement, in particular to the trends of Variscan mylonites. In some regions there was apparently simultaneous extension on two orthogonal fault orientations. On the northern margin of the Pelvoux Massif, late Alpine extensional faults rework both Variscan fabrics in the basement and Alpine mylonites in the cover, producing a large extensional duplex whose roof is a low-angle fault zone in schistose Lias. The late Alpine extension may be caused by gravitational collapse of the thickened crust, or by regional continental extension as part of the opening of the Gulf of Lyon and the Rhone—Bresse Basins.
Pulses of compressional tectonics occurred in the Middle Cretaceous, latest Cretaceous—Early Palaeogene, Eocene—Oligocene and Miocene. During each pulse the deformation occurred principally on foreland-propagating fold and thrust sequences but there are important break-back thrusts, e.g. along the Frontal Pennine Zone, where the thrusts slice across already-sheared and back-tilted rocks to give apparent extensional cut-off relationships. The Alpine compression reactivated Mesozoic faults in basement and syn-rift sediments, deforming the syn-rift graben fill by tight upright folds and back-thrusts. NW-trending Mesozoic lateral ramps gave the basin margin a tooth-like geometry, which on compression did not fit back into the sockets of the opposite margin, causing material to be squeezed out laterally as well as vertically. Such variations in thrust displacement, a form of continental escape similar to large scale indentation tectonics, were partially responsible for the development of the Alpine arc.
Description of brittle extensional features in chalk on the crest of a salt ridge (NW Germany)
Authors: Koestler Andreas G. , Ehrmann Werner U. 
Published: April 2008

Abstract
At Laegerdorf, northern Germany, several large quarries provide access to study extensional deformation features in three dimensions, in the chalk overburden of a salt diapir. Numerous individual faults and the intervening blocks have been analyzed with respect to detailed fault morphology and geometry of brittle structures within the blocks. The studied fault zones, with displacements in the range of several metres, display geometries which vary within well defined limits. The fault zones are mostly very narrow (some tens of centimetres), but can widen up to a maximum of 7 m. The fractures composing a fault zone have a dominant length below 3 m. A 3D reconstruction of one quarry shows the rhombohedral shape of the fault blocks with a block width of 100 to 150 metres and the long diagonal parallel to the salt-ridge axis. The block-internal deformation is characterized by fractures which seem to be interconnected in a network. The locality of Laegerdorf is comparable with that of the Albuskjell and Ekofisk hydrocarbon reservoirs of the central North Sea in terms both of the structural setting of the deformed chalk on top of a salt diapir and the characteristics of extensional features.
Reliability and application of detrital opaque Fe-Ti oxide minerals in provenance determination
Authors: Basu Abhijit , Molinaroli Emanuela 
Published: April 2008

Abstract
A survey of detrital opaque Fe-Ti oxide minerals in Holocene sands derived exclusively from known source rocks in the Rocky Mountains, USA (semi-arid climate, high relief) and the Appalachian Mountains, USA (humid climate, low relief) shows that, despite obvious differences in weathering rates, the abundance of detrital ilmenite relative to parent rocks is similar in these two regions. Because ilmenite is very common in many crystalline rocks, ilmenite is considered to be a useful Fe-Ti oxide mineral for varietal studies. About 30% to 50% of detrital Fe-Ti oxide minerals are polymineralic grains with intergrowths of two or more phases. Discriminant function analysis indicates that morphological varieties of detrital Fe-Ti oxide minerals in combination with their chemical compositions are useful guides to provenance. An igneous or metamorphic source of 96% of the Holocene samples is correctly identified by this method.
The method is used to determine the relative contribution of igneous and metamorphic source rocks to the sandstones of the part of the Tertiary Renova Formation, which was deposited within a dissected magmatic arc in southwestern Montana, USA. A separate discriminant function is calculated using the chemical compositions of detrital ilmenite and morphological properties of detrital Fe-Ti oxide minerals in Rocky Mountain Holocene sands. Classification of detrital Fe-Ti oxide minerals in Renova sandstones using this function suggests that igneous and metamorphic rocks contributed 77% and 23% respectively to the Renova sandstones in this area.
Reworking of plant microfossils and sedimentary provenance
Authors: Batten D. J. 
Published: April 2008

Abstract
Reworked plant microfossils are commonly recovered from sediments along with palynomorphs regarded as in situ. Their potential for locating the source of terrigenous clastics is perhaps generally underestimated. Recognition of reworking may depend on taxonomic identification or differences in colour and preservation, and sometimes on variations in response to staining and fluorescence microscopy. This is demonstrable in some Mesozoic and Cenozoic sequences in NW Europe, with mixed assemblages suggesting derivation from deposits of more than one age and/or source area and geothermal history. Reworked palynomorphs can also indicate the presence of rocks or sediments in the vicinity of a site of deposition that have now been completely removed by erosion.
Palaeoweathering or diagenesis as the principal modifier of sandstone framework composition? A case study from some Triassic rift-valley redbeds of eastern North America
Authors: Velbel Michael A. , Saad Mounir K. 
Published: April 2008

Abstract
Previous studies to recognize a ‘palaeoweathering’ signature in the framework composition of ancient sandstones have been undertaken in study areas where ancient climates are inferred to have been more humid than the present climate. Unfortunately, in studies in which the ancient climate was more humid than the modern, reduction of modal unstable-grain abundance by ancient weathering cannot be distinguished from unstable-grain destruction by burial diagenesis. Reinterpretation of data from Triassic Chatham Group sandstones of the Deep River basin (North Carolina) and modern sands derived from similar source rocks shed new light on the matter, as the Triassic sediments were generated under more arid conditions than the modern wet climate. If diagenesis were the more important factor, the sandstones would have lower contents of unstable grains. If weathering were more important, the ancient sandstones would have higher contents of unstable grains. Chatham Group sandstones have higher unstable grain contents, indicating that the compositional signature imposed on the sandstones under the Triassic climate has survived without being obliterated by diagenesis. Only ‘long-term average’ palaeoclimatic conditions are preserved in sandstone detrital framework modes, and several specific criteria must be met before these conditions can be inferred from sandstone framework composition. The framework-petrographic signatures of palaeoclimate can be discerned only in unglaciated sequences from mature extensional tectonic settings on continental plates, only in sedimentary basins with mild late-diagenetic histories, and only for those modern-ancient pairs where the modern climate is more humid than the inferred ancient climate.
Redistribution of rare earth elements during diagenesis of turbidite/hemipelagite mudrock sequences of Llandovery age from central Wales
Authors: Milodowski A. E. , Zalasiewicz J. A. 
Published: April 2008

Abstract
Geochemical studies of recently mapped Upper Llandovery turbidites in central Wales indicate localized rare earth element (REE) mobilization and fractionation in mudrock-dominated sequences. Closely associated turbidite sandstones, turbidite mudstones and laminated anoxic hemipelagites have generally similar major elemental compositions but display strongly differentiated REE distributions. Shale-normalized REE distribution patterns show that anoxic hemipelagites are consistently enriched in the light and middle REE, with greatest enrichment occurring for La-Eu. This enrichment reflects a concentration of millimetre-scale zoned REE-rich monazite nodules in the hemipelagites. In contrast, the REE patterns of the associated turbidites mirror those of the anoxic hemipelagite, being relatively depleted in the light and middle REE, with Nd and Sm generally showing greatest differentiation. The relationship between the concentration of nodules and degree of enrichment of REE in anoxic hemipelagite and turbidite unit thickness imply upward migration of REE into the overlying hemipelagite. However, mass balance considerations suggest that the turbidite-hemipelagite couplets were not necessarily closed systems.
Within the turbidites, REE were initially held in unstable volcanogenic minerals and adsorbed on to clay minerals and iron-manganese hydroxides. The REE were liberated into the sediment porewaters during early diagenesis and fractionated in the migrating porewaters as a result of the greater solubility of heavy REE relative to light REE. Expulsion of porewaters from the turbidite sediment during burial carried REE in solution through the intervening hemipelagic layers where REE were precipitated, probably in the presence of organic matter, and possibly initially as the hydrous phosphate rhabdophane which later transformed to monazite. Fractionation of the REE during this process led to preferential enrichment of the light and medium REE within the hemipelagic sediment.
The use of REE as indicators of sediment provenance in the Llandovery turbidite-hemipelagite mudrock sequences of central Wales must be treated with caution since significant REE element migration and fractionation is shown to have occurred during their diagenesis. Similar effects might be expected in other sequences comprising interbedded organic-rich/organic-poor mudrock and detailed petrographic analyses should be undertaken to evaluate the possibility of diagenetic REE fractionation and redistribution in conjunction with the use of REE patterns or Sm-Nd isotopes in provenance studies of these rocks.
Selective alteration of arkose framework in Oligo-Miocene turbidites of the Northern Apennines foreland: impact on sedimentary provenance analysis
Authors: Valloni R. , Lazzari D. , Calzolari M. A. 
Published: April 2008

Abstract
Upper Oligocene-Middle Miocene turbidites of the Macigno and Cervarola Formations fill post-collisional elongate basins of the Northern Apennines foreland; they crop out axially for distances up to 300 km and reach a total thickness of 4000 m. Sandstones are arkosic with quartzose grains averaging 50% and fine-grained lithic clasts from 5 to 25%; K-feldspar and plagioclase abundances are similar, and rock fragments are dominated by igneous and metamorphic types. The Macigno sandstones reach a much higher diagenetic grade than the younger Cervarola sandstones. The latter (mature stage of diagenesis), have a clay mineral assemblage with ordered I/S interlayers and illite crystallinity (I.K.) averaging from 8.0 to 10.1, while in the Lower Unit of the Macigno Formation clay crystallinity averages 3.8 (Kübler’s epizone). The evolution of diagenetic processes is unusual because of the abundance of unstable grains. Physical compaction is the main cause of pore reduction. Post-depositional mineralogical changes are relevant in both formations; ignoring authigenic overgrowths and late calcite replacements, they commonly affect 10–20% of the framework grains.
Several mineralogical-textural changes influence provenance determinations, including: dissolution processes, which almost totally eliminate unstable species, such as amphibole and pyroxene, originally dominating the heavy mineral population; replacement processes, mainly represented by albite after plagioclase, and by clay or mica materials after unstable grains; intense deformation plus replacement of ductile or brittle grains with the authigenesis of chlorite, white mica and pseudomatrix.
Sourcelands for the Carboniferous Pennine river system: constraints from sedimentary evidence and U-Pb geochronology using zircon and monazite
Authors: Cliff R. A. , Drewery S. E. , Leeder M. R. 
Published: April 2008

Abstract
Petrographic and U-Pb isotopic data are presented for Carboniferous sandstones from the Pennine basin ranging from Chadian to Westphalian B in age. Variations in the petrography of these samples, particularly the greater abundance of feldspar in Namurian sandstones reported qualitatively by previous authors, are confirmed by modal analyses. The influx of coarse feldspathic sandstones into the Pennine and Southern North Sea basins in the early Namurian is attributed to a marked increase of sediment yields and discharge due to increased precipitation in the hinterlands. The same detrital heavy mineral species occur throughout the Carboniferous. Zircons are petrographically variable both in colour and degree of rounding. Two major sub-populations are recognized; pink-purple grains and colourless-brown grains. U-Pb isotopic analyses of multi-grain fractions of zircon from five of the samples show very similar age patterns; the sixth sample, a Yoredale sandstone appears to be distinct.

Single grain analyses of zircons were used to investigate one sample of late Namurian (Rough Rock) sandstone in detail. Concordant or slightly discordant results demonstrate the presence of: rounded brown grains > 3.5 Ga, rounded purple grains 2.8–3.2 Ga, euhedral purple grains ≥2.9 Ga and clear euhedral grains
c
. 0.41–0.43 Ga.

Monazites are shown to be very suitable for single grain analysis, yielding concordant results more often than zircon. Most of the monazite in the Rough Rock and a Westphalian sandstone are Caledonian (0.41–0.43 Ga) but two individual grains have ages of 0.947 and 2.70 Ga.
The isotopic results appear to exclude large areas of the North Atlantic region as potential sourcelands and no presently exposed rocks provide a close match with the inferred sourceland geology; rocks now under the northern North sea and/or between Scotland and Greenland are possible, as yet untested, sources.
Isotopic characteristics of Ordovician greywacke provenance in the Southern Uplands of Scotland
Authors: Evans Jane A. , Stone Philip , Floyd James D. 
Published: April 2008

Abstract

Interbedded Ordovician greywackes in the Southern Uplands are of markedly different composition. An integration of Sm-Nd isotope data, petrography of detrital clasts, and palaeocurrent flow analyses allows the likely provenance character and distribution to be deduced. The Portpatrick and Galdenoch formations contain detritus from volcanic provenances: andesite dominates the composition of Caradoc-Ashgill greywacke from the Portpatrick Formation which have εNd
445
(time of deposition) between −2.3 and −2.9, the Llandeilo-Caradoc Galdenoch Formation is richer in hornblende and has a slightly lower range of εNd
445
between −3.4 and −4.4. These values contrast with the more isotopically depleted signature of the Llandeilo-Caradoc Kirkcolm Formation greywackes which contain mainly quartz and feldspar clasts and have εNd
445
as low as −11.2. The source of the volcanic rocks, deduced from palaeocurrent analysis, lay on side of the depositional basin (south in terms of modern geography) and the isotopic composition of the volcanic rocks is consistent with a calc-alkaline arc or back-arc assemblage, founded on continental crust. A Proterozoic terrane, represented by detritus from the Kirkcolm Formation, lay on the opposite side of the depositional basin. Dalradian metamorphic rocks currently exposed to the north of the Southern Uplands display a less radiogenic signature than Kirkcolm Formation greywackes and seem unlikely to have acted as their source. This may support interpretations of the Southern Upland Fault as a locus of major sinistral strike-slip movement.
Sedimentary petrology and the archaeologist: the study of ancient ceramics
Authors: Gerrard Christopher M. 
Published: April 2008

Abstract
Ceramics are essentially modified sediments. This paper describes the objectives of the scientific study of ceramics and the range of appropriate methodologies which have been developed in recent years with special reference to ceramic petrology. The paper is illustrated by a number of examples taken from the author’s own work on prehistoric and medieval ceramics from Britain and Spain which demonstrate how the techniques of sedimentology have been modified to provide greater insight into ancient technologies and patterns of social and economic data.
Petrological and geochemical determination of provenance in the southern Welsh Basin
Authors: McCann T. 
Published: April 2008

Abstract
The provenance of Llandeilo to upper Llandovery sediments from the Welsh Basin has been investigated by petrographic and geochemical methods. Sandstone-dominated formations were deposited from high-concentration turbidity currents. Petrographic data suggest derivation from a non-collisional recycled or cratonic setting. This is broadly confirmed by analysis of microconglomerate lithic fragments and the major element geochemistry. Mudstone-dominated formations were deposited from dilute turbidity currents and as hemipelagic sediments. The mudstone geochemistry indicates a tectonic setting transitional between an active continental margin and a passive margin. This study demonstrates that neither set of analytical methods are individually adequate for provenance reconstruction and it is advisable to use a variety of techniques for greater confidence in interpretation.
Sandstones of arc and ophiolite provenance in backarc basin, Halmahera, eastern Indonesia
Authors: Nichols Gary , Kusnama  , Hall Robert 
Published: April 2008

Abstract
Analyses of sedimentary rocks from a late Neogene backarc basin on the island of Halmahera in eastern Indonesia show that the detrital mineral assemblages in the sandstones have distinctive characteristics. Quartz is extremely rare in the entire sequence of up to 4 km of basin sediments, clearly indicating that there has been no input from continental sources throughout the basin history. Sediments derived from two distinct provenance areas are recognized: sandstones dominated by volcanic rocks occur in the western half of the basin and in the eastern part there are black sands composed largely of ultrabasic debris interbedded with carbonate mudstones. These sandstone petrographies reflect the nature of the terrains which have bordered the Halmahera Basin throughout its history and other small basins formed in an ‘oceanic’ setting may show similar characteristics. Temporal changes in the volcaniclastic components are attributed to stages in the evolution of the adjacent volcanic arc and do not reflect the degree of dissection of an arc massif.
Nature and record of igneous activity in the Tonga arc, SW Pacific, deduced from the phase chemistry of derived detrital grains
Authors: Cawood Peter A. 
Published: April 2008

Abstract

Sedimentary rocks in dredge samples from the Tonga arc, SW Pacific, are simple two-component admixtures of volcanogenic detritus and bioclastic material. The volcanic detritus consists largely of lithic and plagioclase grains, but also includes, in decreasing order of abundance, significant minor amounts of clinopyroxene, orthopyroxene and pigeonite. In addition, amphibole, olivine and opaque oxide minerals are accessory phases and trace amounts of monocrystalline quartz occur in a few samples. Plagioclase grains have high An and low Or contents and fall largely in the bytownite field. Pyroxene grains show progressive Fe enrichment and low Ti contents. Volcanic glasses also show Fe enrichment and have low K
2
O contents. These features indicate derivation of the volcanic detritus from a low-K tholeiite source. The uniform compositional range and Oligocene to Holocene age range of the detritus is consistent with their derivation from the adjacent Tongan arc, and indicate that Pliocene rifting of the arc and associated back-arc basin formation did not affect the composition and affinities of the magma source.