bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synsedimentary tectonics of the Triassic Carbonate Formation of the Oujda Mountains (Eastern Meseta, Morocco): geodynamic implications
Authors: Oujidi M. , Azzouz O. , Elmi S. 
Published: April 2008

Abstract
The Ladinian-Carnian tectonic instability is well recorded within the Carbonate Formation of the Oujda Mountains (Eastern Meseta, Morocco). It was induced by a bidirectional extensional palaeo-state of stress (ENE-WSW and NNW-SSE) resulting in the development of the Oujda Mountains Triassic basins that open towards the Western Tethyan domain. This extensional event correlates with an early episode of Tethyan rifting, which is coeval with the Ladinian-Carnian extensional episode of the Alpine domain. The structural development of these basins was controlled by an extensional reactivation of Hercynian faults, with N70°E and N160°E fault trends predominating over the N35°E and N120°E ones. Therefore, the Ladinian-Carnian palaeo-state of stress of the Oujda Mountains is fundamentally different from that of the Triassic-Liassic basins to the west, in Central Morocco and the Atlas belts, where the N45°E-trending, sinistral fault trend predominates over the N70°E and N90°E fault trends.
Tectonic wedge escape in the southwestern front of the Rif Cordillera (Morocco)
Authors: Chalouan A. , Galindo-Zaldívar J. , Akil M. , Marín C. , Chabli A. , Ruano P. , Bargach K. , Sanz de Galdeano C. , Benmakhlouf M. , Ahmamou M. , Gourari L. 
Published: April 2008

Abstract
The Rif Cordillera is a part of the Alpine orogenic arc in the Western Mediterranean, which was developed by the interaction of the westward motion of the Alboran Domain between the converging Eurasian and African plates. The Prerif Ridges, located along the southwestern front of the Rif, are south-vergent folds that are in places associated with faults affecting Jurassic to Quaternary sedimentary rocks and slope breccias that evidence the deformations that were active over the Neogene-Quaternary period. The different southward or southwestward displacement of each Prerif Ridge is related to the development of frontal and lateral ramps, which may or may not reach the surface. Oblique shortening may be explained by southwestward escape of large tectonic wedges, bounded by large strike-slip faults: the North-Middle Atlas fault which extends northward into the Alboran Sea, the Fez-Tissa-Taïneste fault, the Bou Draa-Sidi Fili fault, the Jebha fault and the Fahies fault. The relative displacement of these tectonic wedges toward the SW may explain the NNE-SSW to ENE-WSW compression observed in the Rif front and in the northern part of its Meseta-Atlas foreland.
Transgressive-regressive facies cycles in late Cretaceous calciturbidites from the Mauretanian Series, Béni Ider thrust sheet, northwestern External Rif, Morocco: application of the ‘facies tract-facies sequence’ concept
Authors: El Kadiri Kh. , El Kadiri K. , Chalouan A. , Bahmad A. , Salhi F. , Liemlahi H. , Hlila R. 
Published: April 2008

Abstract
Late Cretaceous mixed carbonate-siliciclastic, thin-bedded turbidites occur between the two great sandstone packages of the Mauretanian Series (the Tisirène and the Béni Ider sandstone flyschs, of early Cretaceous and late Oligocene-early Burdigalian age, respectively). The application of the facies tract-facies sequence model allows subdivision of the studied calciturbidites into five distinct facies sequences (FS.1–5), which equal five transgressive-regressive facies cycles. These cycles mainly consist of thinning upward calciturbidites, which almost all start with coarse-grained carbonate breccias, and passing upward into a shale-dominated interval. Fe-stained discontinuities, together with sedimentological and ichnological evidence, lead us to assign these two lithological components to a transgressive and a regressive trend, respectively. This result provides new insights into the sequence-stratigraphic interpretation of turbiditic successions.
Regional correlations across the Internides-Externides front (northwestern Rif Belt, Morocco) during the Late Cretaceous-Early Burdigalian times: palaeogeographical and palaeotectonic implications
Authors: El Kadiri Kh. , Hlila R. , Sanz de Galdeano C. , López-Garrido A. C. , Chalouan A. , Serrano F. , Bahmad A. , Guerra-Merchán A. , Liemlahi H. 
Published: April 2008

Abstract
New insights into the palaeogeographical evolution of the Rifian Internides and their external surroundings are inferred from six key stratigraphic successions selected across the Internides-Externides front. These successions span a time interval ranging from the late Cretaceous to the early Burdigalian. The main results are: (1) important lost palaeogeographical domains should be located during the late Cretaceous-Eocene between the present-day Ghomarides and the Dorsale Calcaire, on one hand, and between the Predorsalian units and the Flysch Trough as isolated carbonate platforms, on the other hand; (2) during the late Eocene-early Oligocene an extensional tectonic event, well marked in the Dorsale Calcaire, caused the collapse of these platforms and resulted in olistostromes and coarse-grained breccias in both the Predorsalian and the Béni Ider areas; (3) by the beginning of mid-Oligocene, an overturning contractional event in the Ghomarides resulted in the regional onset of the siliciclastic depositional regime throughout these palaeogeographical areas; (4) during the Aquitanian-early Burdigalian, the stepwise return of pelagic deposition in the Ghomarides indicates extensional phases, whereas the homogenization of the same pelagic facies over the Dorsale Calcaire and its external surroundings may indicate that the previously distant palaeogeographical areas were brought nearer (i.e. just before large-scale thrusting).
The Argille Varicolori unit in Lucania (Italy): a record of tectonic offscraping and gravity sliding in the Mesozoic-Tertiary Lagonegro Basin, southern Apennines
Authors: Mattioni L. , Tondi E. , Shiner P. , Renda P. , Vitale S. , Cello G. 
Published: April 2008

Abstract
Detailed geological mapping and new stratigraphic and structural data collected in the Lucania area of the southern Apennines allowed us to assess the deformation history of Il Monte-Corleto Perticara zone, in the High Agri Valley (Lucanian Apennines, southern Italy) where red and green shales (known as Argille Varicolori or Argille scagliose) crop out. Our observations suggest that: (1) ‘chaotic’ facies within the Argille Varicolori may be attributed to a broken formation generated by overthrusting of Apenninic Platform units onto already deformed Lagonegro basin strata; (2) gravity sliding phenomena at the thrust front enhanced the development of debris flow and the emplacement of olistostromes at distances of up to tens of kilometres from the leading edge of the Apenninic Platform thrust; (3) the above processes probably ended in mid-Miocene time, as suggested by observed structural and stratigraphic relationships among accreted terranes and synorogenic deposits. The evolutionary model envisaged here could also be relevant in other active convergent zones, where seismic and drilling data are sparse, and in subaerial fossil margins where broken formations occur.
Pore geometry of Permo-Triassic sandstone from measurements of electrical spectroscopy
Authors: Scott Julian B. T. , Barker R. D. 
Published: April 2008

Abstract
In order to provide an indirect method of estimating the hydraulic properties of sandstone aquifer rocks, electrical spectroscopy measurements were made on Permo-Triassic Sandstone over the frequency range 0.0001–1000 Hz. Samples from several boreholes across Britain are shown to exhibit a phenomenon called electrical relaxation, which we have modelled using a generalized Cole-Cole equation. The Cole-Cole parameters correlate well with other hydrogeologically important parameters determined using mercury injection capillary pressure and nitrogen adsorption techniques. Of greatest importance is that the relaxation time, τ, is strongly related to the dominant pore-throat size from which intergranular permeability may be estimated. A normalized version of the chargeability appears to be related to the surface conductivity and this gives the possibility of estimating the pore surface area to volume ratio, a value that is important in determining both permeability and sorption. The potential uses of electrical spectroscopy in hydrogeology and many other fields, including geology and petroleum petrophysics, are only now becoming apparent, and further advances are certain.
Estimation of vertical diffusivity from seasonal fluctuations in groundwater pressures in deep boreholes near Sellafield, NW England
Authors: Streetly M. J. , Heathcote J. A. , Degnan P. J. 
Published: April 2008

Abstract
In 1998, as part of the process to assess the suitability of a site near Sellafield, Cumbria, for a deep geological repository for solid intermediate level and some solid low-level radioactive waste, United Kingdom Nirex Limited (Nirex) commissioned a study into the seasonal fluctuations in groundwater pressure observed in many of the monitoring boreholes in the area. Many of the monitoring zones in the deep boreholes at Sellafield show some response in groundwater pressure to annual variations in recharge. These seasonal fluctuations were quantified in terms of amplitude and lag over two full recharge cycles (1994–1996). The extremely detailed monitoring array installed by Nirex at the potential repository zone gives a unique opportunity to observe in detail the attenuation of the recharge signal, as it is propagated vertically downwards through the Sherwood Sandstone Group and into the underlying basement rocks. Use of an analytical approach to model the data provides constraints on values of the vertical diffusivity of the strata. The values of hydraulic formation parameters derived by this methodology are broadly consistent with results from borehole testing, though somewhat higher. This may in part be due to the large scale associated with the cyclic recharge signal. The attenuation of the seasonal fluctuations in three dimensions (3D) throughout the study area provides information at a scale suitable for use in constraining regional flow models.
Structural controls on groundwater flow in the Permo-Triassic sandstones of NW England
Authors: Seymour K. J. , Ingram J. A. , Gebbett S. J. 
Published: April 2008

Abstract
There is increasing evidence that groundwater flow in many parts of the major Permo-Triassic sandstone aquifers of NW England is influenced strongly by predominantly N-S-trending faults. These structural controls on groundwater flow may only become apparent when the aquifers are subject to abstraction stress. A series of case examples are presented, from the Fylde Sandstone aquifer north of Preston, and from the sandstone aquifers of the Lower Mersey Basin, Manchester and Wirral areas. In these studies the ‘compartmentalization’ of the aquifers by faults has been recognized in field investigations and also in numerical modelling studies related to groundwater resources development on both local and aquifer-wide scales.
Controls on dense non-aqueous-phase liquid transport in Permo-Triassic sandstones, UK
Authors: Gooddy D. C. , Bloomfield J. P. 
Published: April 2008

Abstract

The Permo-Triassic sandstones are geographically and lithologically diverse, and exhibit large variations in porosity (ф), pore-throat size, gas permeability (
k
) and mineral phases. These parameters influence considerably the flow and transport of contaminants. The aquifer is susceptible to contamination by a range of pollutants from both contemporary and historic sources as it outcrops in a number of large industrial towns. One such class of pollutants are chlorinated hydrocarbons, which have been used extensively for years in dry-cleaning and metal degreasing. The physical, chemical and biological properties of these dense non-aqueous-phase liquids (DNAPLs) make them a particular cause of groundwater contamination. Standard physical property measurements, along with a weak nitric acid extraction to determine dominant minerals, were carried out on consolidated sandstones. A laboratory method was developed to produce pressure-saturation curves for a DNAPL-water-sandstone system. Entry pressures were found to be lower than predicted from theoretical considerations, which could be explained in part by the relative amounts of calcite and dolomite present in the pore space. Calculations on relative permeability show that at roughly 60% DNAPL saturation no water flow occurs. Understanding the controls on DNAPL transport can greatly assist the need for appropriate remedial action.
The capillary characteristic model of petroleum hydrocarbon saturation in the Permo-Triassic sandstone and its implications for remediation
Authors: Privett K. D. 
Published: April 2008

Abstract

Up to 9 × 10
6
l of light non-aqueous-phase liquid (LNAPL) is present in a 400 m-wide zone in the Permo-Triassic sandstone 30 m below a working industrial site. Remediation by skimmer wells failed to meet the expectations of the regulatory authorities. A detailed study has concluded that this form of remediation is not possible in this formation.

Initial estimates of the volume of LNAPL in the sandstone had been made by applying the concept of correcting for an ‘exaggerated thickness’ in the wells and multiplying by the porosity. Regulatory requirements were to remove most, preferably all, of the LNAPL. Site observations and measurements from high-quality core samples showed that the fine pores of the rock obey the capillary characteristic model. This was derived some 50 years ago in the oil production industry but has, in the opinion of the author, not been fully appreciated by the contaminated groundwater remediation sector in the UK. The model has been used to make a more reliable estimate of LNAPL volume and to demonstrate to the regulatory authorities the processes involved and how these control the ability to clean the site.
The concept of ‘apparent volume’ is introduced as an overall measure of apparent thickness in the site-wide monitoring borehole network. Apparent volume is shown to be broadly negatively correlated with groundwater-level fluctuations and so the measure of changes in apparent thickness is not a sound basis for regulatory compliance. It was found that LNAPL thickness in wells is less than the thickness of the contaminated zone in the sandstone and, importantly, the degree of saturation is no more than 30%. This leads to a reduction in effective permeability of two orders of magnitude (from the fully saturated condition), which has serious implications for remediation. Most of the LNAPL is immobile and so pumping is ineffective; it does not reduce the volume of aquifer impacted nor does it have any significant effect on reducing the source zone for dissolved-phase generation, the size of any dissolved phase plume or the longevity of such a plume.
Combined isotopic and modelling approach to determing the source of saline groundwaters in the Selby Triassic sandstone aquifer, UK
Authors: Bottrell S. H. , West L. J. , Yoshida K. 
Published: April 2008

Abstract

Groundwater abstraction from the Triassic Sherwood Sandstone aquifer in the Selby area, Yorkshire, UK, has caused decline of the water level in the aquifer and groundwater quality problems such as high chloride and sulphate concentrations. Geochemical and isotopic analysis of groundwaters and groundwater modelling of an approximately 25 × 30 km area around Selby was carried out to understand the groundwater flow conditions and identify the source of saline water. Isotopic compositions (δ
34
S and δ
18
O) of seawater sulphate, Coal Measures brine and Permian evaporite sources do not match that associated with salinity in the Selby wellfield. Rather, the source of saline groundwater in the Selby wellfield matches the isotopic composition of Triassic evaporites in the overlying Mercia Mudstones.

Steady-state groundwater flow modelling demonstrates that that majority of water abstracted from the Selby wellfield is balanced by recharge from the west of Selby at Brayton Barff, and from the Escrick and York moraines to the north. A small proportion of the abstracted water originates from leakage from the River Ouse through the confining layer as a result of drawdown in the Selby area. The development of a cone of drawdown centred on Selby has created a new E-W hydraulic gradient to the east of Selby, allowing water ingress from the east. Capture-zone analysis indicates that the four abstraction boreholes contaminated by saline water collect groundwater from the north to NE (i.e. from the direction of the boundary between the Sherwood Sandstone and the Mercia Mudstone), confirming that the source of salinity is likely to be the Mercia Mudstone evaporites.
Simplicial geometry for compositional data
Authors: Egozcue J. J. , Pawlowsky-Glahn V. 
Published: April 2008

Abstract

The main features of the Aitchison geometry of the simplex of
D
parts are reviewed. Compositions are positive vectors in which the relevant information is contained in the ratios between their components or parts. They can be represented in the simplex of
D
parts by closing them to a constant sum, e.g. percentages, or parts per million. Perturbation and powering in the simplex of
D
parts are respectively an internal operation, playing the role of a sum, and of an external product by real numbers or scalars. These operations impose the structure of (
D
− 1)-dimensional vector space to the simplex of
D
parts. An inner product, norm and distance, compatible with perturbation and powering, complete the structure of the simplex, a structure known in mathematical terms as a Euclidean space. This general structure allows the representation of compositions by coordinates with respect to a basis of the space, particularly, an orthonormal basis. The interpretation of the so-called balances, coordinates with respect to orthonormal bases associated with groups of parts, is stressed. Subcompositions and balances are interpreted as orthogonal projections. Finally, log-ratio transformations (alr, clr and ilr) are considered in this geometric context.
The magnetic polarity time scale across the Permian-Triassic boundary
Authors: Steiner Maureen B. 
Published: April 2008

Abstract
Early Triassic and Late to Middle Permian magnetostratigraphic investigations are numerous and span the globe. More than 20 magnetostratigraphic sequences have documented all or part of the Early Triassic geomagnetic field polarity, and > 27 have examined the Late and Middle Permian; 13 span the Permian-Triassic boundary. In order to assess the exact polarity sequence in the time period surrounding the Permian-Triassic boundary, the sequences have been compared diagrammatically. Four distinctive intervals of geomagnetic polarity characterize the Early Triassic, and have been named for discussion purposes: Gries N, Diener R-N, Smith N, and Spath N. A polarity pattern for the Mid- and Late Permian is also recognizable. The Mid- and Late Permian are characterized by two normal polarity intervals (Chang N and Capitan N) of greater apparent duration than those of the Early Triassic. Below the Permo-Triassic Gries N, a distinctive short duration reversed-normal-reversed polarity pattern characterizes the uppermost Changhsingian. The oldest normal polarity in the Middle Permian occurred during the Wordian Stage, established by results from three global sequences. Therefore, the geomagnetic field resumed reversing behaviour after the ∼50 Ma-long constant polarity of the Kiaman Reversed Polarity Superchron (‘Illawarra reversals’) during the Mid- to Late Wordian, or ∼267 Ma.
Very significantly, the magnetostratigraphic summary from this work indicates that the Siberian Traps were active in the Late Permian and spanned the Permian-Triassic boundary. This new geomagnetic polarity dating of the massive Siberian flood basalt activity suggests long-term eruption and environmental degradation, therefore making this igneous activity the most likely cause of the end-Permian mass extinctions. Magnetostratigraphy suggests that eruptions probably commenced in the Late Guadalupian; therefore, the eruptions of two large igneous provinces, Emishan and Siberian, were probably partly simultaneous during part of the Mid- to Late Permian. Environmental havoc throughout the late Mid- and Late Permian is easy to imagine, stressing the environment prior to probably more voluminous eruptions at the end of the Guadalupian and Permian. Siberian eruptions continued through the early Early Triassic, and probably contributed to the slow biotic recovery.
Global Permian tetrapod biostratigraphy and biochronology
Authors: Lucas Spencer G. 
Published: April 2008

Abstract
The most extensive Permian tetrapod (amphibian and reptile) fossil records from the western United States (New Mexico-Texas) and South Africa provide the basis for definition of 10 land-vertebrate faunachrons that encompass Permian time. These are (in ascending order): the Coyotean, Seymouran, Mitchellcreekian, Redtankian, Littlecrotonian, Kapteinskraalian, Gamkan, Hoedemakeran, Steilkransian and Platbergian. These faunachrons provide a biochronological framework with which to determine and discuss the age relationships of Permian tetrapod faunas. Their correlation to the marine time scale and its numerical calibrations indicate that the Coyotean is a relatively long time interval of about 20 Ma, whereas most of the other faunachrons are much shorter, about 1–2 Ma long each. The Platbergian may also be relatively long, 14 Ma, although this is not certain. This suggests slow rates of terrestrial tetrapod faunal turnover during most of the Early Permian and late Middle to Late Permian, but more rapid rates of turnover during the latest Early and most of the Middle Permian, especially during the explosive initial diversification of therapsids.