bluuebunny/crossref_metadata_2025_split huggingface dataset:
DC electrical properties of Permo-Triassic sandstone
Authors: Taylor Steve , Barker Ron 
Published: April 2008

Abstract
The DC electrical properties of fully and partially saturated, poorly cemented Permo-Triassic sandstone samples have been measured in the laboratory and the results analysed using three popular models. The results of this work, undertaken on samples from the Wildmoor Formation, indicate that the Permo-Triassic sandstone of the UK is a typical shaly sandstone, which cannot be satisfactorily modelled using the simple conventional relationships proposed by Archie for application in the oil industry to non-shaly formations. Application of the more sophisticated models of Waxman-Smits and Hanai-Bruggeman more faithfully model the electrical response of the sandstone. In addition, the derived parameter estimates are better able to characterize the electrical properties of the rock and correlate better with other independently determined hydraulic properties. Application of these models in groundwater investigations will therefore lead to better and more useful estimates of hydraulic parameters. More importantly, this knowledge will allow more accurate quantitative interpretation of electrical monitoring of the vadose zone.
Flow and transport in the unsaturated Sherwood Sandstone: characterization using cross-borehole geophysical methods
Authors: Winship Peter , Binley Andrew , Gomez Diego 
Published: April 2008

Abstract

Cross-borehole radar and resistivity measurements have been used to characterize changes in moisture content and solute concentration due to controlled injection of 1200 1 of a saline tracer in the unsaturated zone of the Sherwood Sandstone at a field site in Yorkshire, UK. Borehole radar transmission profiles show the vertical migration of the wetting front during the tracer test. Three-dimensional cross-borehole electrical resistivity tomography was deployed to monitor changes over time in resistivity, caused by the increase in moisture content and pore-water salinity due to the tracer. The results show clearly the development of the tracer plume as it migrates towards the water table at a depth of 10 m. The tomographic results reveal the impact of a hydraulically impeding layer between a depth of 8 and 9 m. Geophysical and geological logs acquired at the site support this conceptualization. By combining the resistivity tomograms with cross-borehole radar tomograms, changes in pore-water concentration over time have been estimated. Changes in moisture content inferred from the geophysical results were compared with those produced by a three-dimensional unsaturated flow model. Using a sandstone effective hydraulic conductivity of 0.4 m day
−1
in the model produced moisture profiles over time that were comparable with those inferred from the geophysical data during the early stages of the tracer test. Differences between modelled and field results were attributed to the impact of hydraulically impeding layers of finer sediments within the profile.
The arsenic concentration in groundwater from the Abbey Arms Wood observation borehole, Delamere, Cheshire, UK
Authors: Kinniburgh David G. , Newell Andrew J. , Davies Jeff , Smedley Pauline L. , Milodowski Anthoni E. , Ingram John A. , Merrin Philip D. 
Published: April 2008

Abstract

A 150 m observation borehole was drilled in Abbey Arms Wood, Delamere, Cheshire, UK in order to explore the local hydrogeological conditions and to understand better the source of the high concentrations of arsenic in some of the local groundwaters. The borehole was located on an outcrop of the Helsby Sandstone Formation (part of the Sherwood Sandstone Group) and was cored into the underlying Wilmslow Sandstone Formation. The aquifers in the area are unconfined and give rise to low-Fe groundwaters with As concentrations in the 10–50 µg l
−1
range. The chemical composition of the sediments is quite uniform down to 150 m. The total arsenic content is in the range from 5 to 15 mg kg
−1
and averaged 8 mg kg
−1
(
n
= 60). There is no trend in sediment As concentration with depth, but pore water centrifuged from the core steadily increased in As concentration with depth. The As concentration ranges from 8 µg l
−1
at 10 m (unsaturated zone) to 30 µg l
−1
at 150 m. The source of the dissolved As remains unclear but the lack of evidence for discrete high-As minerals or zones of mineralization suggests that it is probably derived by desorption from rock-forming minerals in the sandstones, e.g. iron oxides. This may be in response to slightly higher pH (up to 8.0 at depth). If this trend applies throughout the area, restricting the screened interval for abstraction boreholes to the uppermost parts of the saturated zone may reduce As concentrations, but is likely to reduce yields and may also risk encountering groundwaters with high nitrate concentrations.
Major-oxide compositional discrimination in Cenozoic volcanites of Hungary
Authors: Ó.Kovács L. , Kovács G. P. , Martín-Fernández J. A. , Barceló-Vidal C. 
Published: April 2008

Abstract
In the present study multivariate statistical methods emerging from log-ratio methodology are applied to an extensive major element dataset of Cenozoic volcanic rocks of Hungary. For an easy comparison, several conventional data plots are also given. The revealed compositional geometry shows a good agreement with geological models based on geoscientific methods which do not fulfil a definite statistical approach. Subcompositional patterns within the two major groups (alkaline basalts and calc-alkaline rocks), and their good separation, known from earlier interpretations of stratigraphical, petrographical, geochemical and other data, are statistically confirmed. The linear compositional patterns disclosed here for these two rock series provide additional details helping to describe quantitatively and, hence, elucidate the nature of petrogenetic processes that affected the Cenozoic volcanites in Hungary.
Discriminating geodynamical regimes of tin ore formation using trace element composition of cassiterite: the
Sikhote’Alin
case (Far Eastern Russia)
Authors: Gorelikova N. , Tolosana-Delgado R. , Pawlowsky-Glahn V. , Khanchuk A. , Gonevchuk V. 
Published: April 2008

Abstract

A possible interpretation of the
Sikhote’Alin
accretion system (Asian margin of the Pacific Ocean) assumes that this region underwent an alternation of subduction and transform tectogenesis (here called the
tectogenetic switch
hypothesis). This palaeotectonic model fits well with the observed complexity of ore districts and deposits of the region. In this contribution, several statistical analyses are applied to a compositional dataset of trace elements in cassiterite obtained from this area. The goal is to assess the reliability of the tectogenetic switch hypothesis, based solely on cassiterite compositional information. First, biplots are used to get an insight into the variability of the data. Secondly, cluster analysis is applied to detect the existence of natural groups of samples, without using the existing geological information. Finally, discriminant analysis uncovers the main differences in the composition of cassiterite from the different groups obtained. Results highlight the contrast between areas formed under different tectogenetic environments, being subduction-related cassiterite richer in siderophile elements (In, Fe, Sc, W, Cr) and transform-related cassiterite richer in lithophile elements (Mn, Zr). Further natural groups discriminate cassiterite samples depending on their V/Be ratio, which might be related to the age of the deposit. These results suggest that sources of ore magmas and fluids within the region might have a mixed or varied mantle-crust origin and support the tectogenetic switch assumption.
Compositional data analysis with ‘R’ and the package ‘compositions’
Authors: Van Der Boogaart K. G. , Tolosana-Delgado R. 
Published: April 2008

Abstract
This paper is a hands-on introduction and shows how to perform basic tasks in the analysis of compositional data following Aitchison’s philosophy, within the statistical package ‘R’ and using a contributed package (called ‘compositions’), which is devoted specially to compositional data analysis. The studied tasks are: descriptive statistics and plots (ternary diagrams, boxplots), principal component analysis (using biplots), cluster analysis with Aitchison distance, analysis of variance (ANOVA) of a dependent composition, some transformations and operations between compositions in the simplex.
Permian tetrapod ichnofacies
Authors: Hunt Adrian P. , Lucas Spencer G. 
Published: April 2008

Abstract

Three fundamental terms in ichnology are:

(1)
assemblage, which is equivalent to an assemblage of body fossils;

(2)
ichnocoenosis, which is a trace fossil assemblage produced by a biological community that can be characterized by morphological criteria;

(3)
ichnofacies, which refers to recurrent ichnocoenoses that represent a significant portion of Phanerozoic time.

There are five archetypal vertebrate ichnofacies for non-marine environments (
Chelichnus, Grallator, Carichnium, Batrachichnus, Characichichnos
) of which four are present in the Permian:

(1)

Chelichnus
ichnofacies —
Chelichnus
ichnocoenosis;

(2)

Batrachichnus
ichnofacies —
Batrachichnus
ichnocoenosis;

(3)

Brontopodus
ichnofacies —
Pachypes
ichnocoenosis;

(4)

Characichichnos
ichnofacies —
Serpentichnus
ichnocoenosis. The
Chelichnus
and
Characichichnos
ichnofacies occur throughout the Permian, the
Batrachichnus
ichnofacies is restricted to the Early Permian and the
Brontopodus
to the Middle to Late Permian. The
Batrachichnus
ichnocoenosis can be divided into the
Ichniotherium
sub-ichnocoenosis,
Amphisauropus
sub-ichnocoenosis and the
Dimetropus
subichnocoenosis, which represent a spectrum of non-marine environments from alluvial fan to tidal flat.
Amphibian biostratigraphy of the European Permo-Carboniferous
Authors: Werneburg Ralf , Schneider Joerg W. 
Published: April 2008

Abstract
A revised amphibian zonation for the European Pennsylvanian and Cisuralian (Upper Carboniferous to Lower Permian) with nine amphibian zones is presented. The index fossils belong to species-chronoclines with two or three closely related species. The time resolution of these amphibian zones is about 1.5–3.0 Ma. Biostratigraphical correlations with amphibian zones are applicable to 16 basins in the Czech Republic, Poland, France, Italy and Germany. The biostratigraphical potential of other tetrapods is discussed.
New techniques in sediment core analysis: an introduction
Authors: Rothwell R. Guy , Rack Frank R. 
Published: April 2008

Abstract
Marine sediment cores are the fundamental data source for information on seabed character, depositional history and environmental change. They provide raw data for a wide range of research including studies of global climate change, palaeoceanography, slope stability, oil exploration, pollution assessment and control, and sea-floor surveys for laying cables, pipelines and siting of sea-floor structures. During the last three decades, a varied suite of new technologies have been developed to analyse cores, often non-destructively, to produce high-quality, closely spaced, co-located downcore measurements, characterizing sediment physical properties, geochemistry and composition in unprecedented detail. Distributions of a variety of palaeoenvironmentally significant proxies can now be logged at decadal and, in some cases, even annual or subannual scales, allowing detailed insights into the history of climate and associated environmental change. These advances have had a profound effect on many aspects of the Earth Sciences, particularly palaeoceanography. In this paper, we review recent advances in analytical and logging technology, and their application to the analysis of sediment cores. Developments in providing access to core data and associated datasets, and data-mining technology, in order to integrate and interpret new and legacy datasets within the wider context of sea-floor studies, are also discussed. Despite the great advances in this field, however, challenges remain, particularly in the development of standard measurement and calibration methodologies and in the development of data analysis methods. New data visualization tools and techniques need to be developed to optimize the interpretation process and maximize scientific value. Amplified collaboration environments and tools are needed in order to capitalize on our analysis and interpretation capability of large, multi-parameter datasets. Sophisticated, yet simple to use, searchable Internet databases, with universal access and secure long-term funding, and data products resulting in user-defined data-mining query and display, so far pioneered in the USA and Australia, provide robust models for efficient and effective core data stewardship.
Colour logging as a tool in high-resolution palaeoceanography
Authors: Rogerson M. , Weaver P. P. E. , Rohling E. J. , Lourens L. J. , Murray J. W. , Hayes A. 
Published: April 2008

Abstract

Colour and diffuse reflectance records can be used to develop astronomically tuned age models for long sediment cores. Here, we present high-resolution (1 mm) colour records from a sediment core from the western Gulf of Cadiz of SW Spain (D13892), spanning the last deglaciation, in parallel with stable isotope (δ
18
O) and sea surface temperature (SST) proxy data. The age model is based on δ
18
O stratigraphy complemented by five atomic mass spectroscopy (AMS) radiocarbon datings. We find good comparison between the colour record of D13892 and the GISP2 oxygen isotope series (
R
2
= 0.81), which strongly suggests that the sediment colour reflects the state of the climate. As sediment colour variability has previously been found to be diagnostic of changes in mineralogical/chemical composition, we relate the causes of the colour variability in D13892 to changes in the local particle flux, and support these observations with data from core-logging X-ray fluorescence (XRF) analyses. The colour and XRF logger records for D13892 suggest that the last glaciation and Younger Dryas were characterized by an enhanced supply of terrigenous detritus into the western Gulf of Cadiz. Cyclicities with wavelengths of 607 and 1375 years are recognized in the colour records for the Holocene. This cyclicity also relates to variability in detrital supply, with an important eolian component implied by enrichment in hematite during cycle maxima.
Sediment mineralogy based on visible and near-infrared reflectance spectroscopy
Authors: Jarrard Richard D. , Vanden Berg Michael D. 
Published: April 2008

Abstract
Visible and near-infrared spectroscopy (VNIS) can be used to measure reflectance spectra (wavelength 350–2500 nm) for sediment cores and samples. A local ground-truth calibration of spectral features to mineral percentages is calculated by measuring reflectance spectra for a suite of samples of known mineralogy. This approach has been tested on powders, core plugs and split cores, and we conclude that it works well on all three, unless pore water is present. Initial VNIS studies have concentrated on determination of relative proportions of carbonate, opal, smectite and illite in equatorial Pacific sediments. Shipboard VNIS-based determination of these four components was demonstrated on Ocean Drilling Program Leg 199.
Pressure coring, logging and subsampling with the HYACINTH system
Authors: Schultheiss P. J. , Francis T. J. G. , Holland M. , Roberts J. A. , Amann H. , Thjunjoto  , Parkes R. J. , Martin D. , Rothfuss M. , Tyunder F. , Jackson P. D. 
Published: April 2008

Abstract

The HYACINTH suite of equipment has been developed to investigate the pressure sensitive behaviour of sedimentary formations up to 250 bar (25 MPa). It does this by collecting pressure-preserved samples from boreholes that can be retrieved, subsampled and analysed in controlled conditions in the laboratory. This paper reviews the development of the system, how it originated from the need to better understand the nature and distribution of gas hydrates beneath the sea bed, and its achievements to date. While gas hydrates continue to be the major scientific and commercial impetus for using, and further developing, this pressure-sampling technology, other important scientific driving forces, including the growing interest in the deep biosphere beneath the sea floor, are playing an important role. We review the downhole tools, the transfer system and the suite of different pressure chambers that are required to make a complete working system. Non-destructive logging of cores contained in pressure chambers, using existing gamma- and X-ray techniques, is discussed, as are future logging techniques that will have sensors embedded within the pressure chambers. Subsamples can now be taken at full pressure and transferred into specialized chambers where intrusive measurements and experiments can be performed (e.g. inoculation chambers for microbiology). The versatile philosophy behind the integrated systems will enable future developments to be made by third parties who want to obtain subsamples at
in situ
pressure from the HYACINTH system. We conclude by reviewing some of the highlights of the HYACINTH operations on ODP Leg 204 where the downhole tools retrieved cores containing gas hydrates (up to 40% by volume) that were subsequently logged on board in the laboratory. These data have already contributed to the scientific understanding of the nature and distribution of gas hydrates beneath the seabed in one area on the Oregon Margin off the USA.
Rapid non-contacting resistivity logging of core
Authors: Jackson P. D. , Lovell M. A. , Roberts J. A. , Schultheiss P. J. , Gunn D. , Flint R. C. , Wood A. , Holmes R. , Frederichs T. 
Published: April 2008

Abstract
We demonstrate a non-contact approach to whole-core and split-core resistivity measurements, imaging a 15 mm-thick, dipping, conductive layer, producing a continuous log of the whole core and enabling the development of a framework to allow representative plugs to be taken, for example. Applications include mapping subtle changes in grain fabric (e.g. grain shape) caused by variable sedimentation rates, for example, as well as the well-known dependencies on porosity and water saturation.
The method operates at relatively low frequencies (i.e. low induction numbers), needing highly sensitive coil pairs to provide resistivity measurements at the desired resolution. A four-coil arrangement of two pairs of transmitter and receiver coils is used to stabilize the measurement. One ‘coil pair’ acts as a control, enabling the effects of local environmental variations, which can be considerable, to be removed from the measurement at source.
Comparing our non-contact approach and independent traditional ‘galvanic’ resistivity measurements indicates that the non-contact measurements are directly proportional to the reciprocal of the sample resistivity (i.e. conductivity). The depth of investigation is discussed in terms of both theory and practical measurements, and the response of the technique to a variety of synthetic ‘structures’ is presented.
We demonstrate the potential of the technique for rapid electrical imaging of core and present a whole-core image of a dipping layer with azimuthal discrimination at a resolution of the order of 10 mm. Consequently, the technique could be used to investigate different depths within the core, in agreement with theoretical predictions.
Logging-while-coring — new technology for the simultaneous recovery of downhole cores and geophysical measurements
Authors: Goldberg D. , Myers G. , Iturrino G. , Grigar K. , Pettigrew T. , Mrozewski S. 
Published: April 2008

Abstract
A newly developed logging-while-coring system was deployed during Ocean Drilling Program legs 204 and 209 off the coast of Oregon and near the Mid-Atlantic Ridge. The system consists of two existing devices modified to be used together — a Schlumberger Resistivity-at-the-Bit* tool, and a Texas A&M University wireline-retrieved core barrel and latching tool. The combination allows for precise core-log depth calibration and core orientation within a single borehole, and without a pipe trip. These tests, conducted in clay-bearing sediments (Leg 204) and in crustal peridotite and gabbroic rocks (Leg 209), mark the first simultaneous use of coring and logging-while-drilling technologies. Sediment cores were recovered with 33% recovery, on average, and as high as 68% to 75 m depth below the sea floor. Core recovery in crustal rocks was only 1–2%, however, penetrating to 21 m depth below sea floor, which is attributed to a problem with the core catcher. High-resolution logs were recorded in the downhole tool memory over the entire drilled intervals at both test sites. It is anticipated that logging-while-coring systems will be utilized more routinely where rig time constraints may otherwise preclude coring in difficult drilling environments.
Core data stewardship: a long-term perspective
Authors: Moore Carla J. , Habermann Ray E. 
Published: April 2008

Abstract
The US National Oceanic and Atmospheric Administration (NOAA) National Geophysical Data Center (NGDC) and collocated World Data Center for Marine Geology and Geophysics, Boulder, CO, USA provides scientific data stewardship for many environmental datasets, including geological information derived from sea-floor samples. The essence of NGDC’s stewardship philosophy is that data management practices must evolve and incorporate new technologies in order to keep data interoperable with complementary data streams and maintain their usefulness in a changing research environment. The Index to Marine and Lacustrine Geological Samples database exemplifies NGDC’s evolutionary and collaborative approach to data management. The most recent version of the Index is a geospatially enabled relational database, providing data discovery and delivery via an interactive map on the Web. Geospatial databases and Internet mapping tools are an integral part of NGDC’s current centre-wide systems architecture.