bluuebunny/crossref_metadata_2025 huggingface dataset:
Perspectives for earthquake prediction in the Mediterranean and contribution of geological observations
Authors: Papazachos B. C. , Karakaisis G. F. , Papazachos C. B. , Scordilis E. M.
Published: April 2008

Accelerating seismic strain caused by the generation of intermediate-magnitude preshocks in a broad (critical) region, accompanied by decelerating seismic strain caused by the generation of smaller preshocks in the seismogenic region are systematically observed before strong mainshocks. On the basis of this seismicity pattern a model has been developed that seems promising for intermediate-term earthquake prediction, called the ‘Decelerating in-Accelerating out Seismic Strain Model’. Recent seismological data for the Mediterranean region are used here for backward and forward testing of this model. The selection of the broader Mediterranean region as a test area was motivated not only by the interest of time-dependent seismic hazard assessment in a high-seismicity and highly populated region but also by the fact that the Mediterranean is a natural geophysical and geological laboratory where both complex multi-plate and continuum tectonics are found in a more or less convergent zone. Within this complex geotectonic setting several geological phenomena such as subduction, collision, orogen collapse and back-arc extension take place, leading to the generation of a broad spectrum of mainshocks, reaching M
W
= 8.0 or greater for subduction-related thrust events and a variety of corresponding seismicity levels and neotectonic activity ranging from very low (e.g. large parts of Iberian peninsula) to very high (broader Aegean area). The backward procedure shows that all six strong (M ≥ 6.8) mainshocks that have occurred in the Mediterranean since 1980 had been preceded by preshock sequences that followed this seismicity pattern and satisfy all model constraints. Application of the model for future mainshocks has led to the identification of nine regions (in the Pyrenees, Calabria, NE Adriatic, Albania, Northern Greece, SE Aegean, NW Anatolia, western Anatolia, NE Anatolia) where current intermediate-magnitude seismicity satisfies the constraints of the model and corresponds to strong (M ≥ 6.2) mainshocks. The magnitudes, epicentres and origin times of these probably ensuing mainshocks, as well as their corresponding uncertainties, are estimated, so that it is possible to evaluate the model potential during the next decade (2006–2015). Furthermore, it is shown that geological observations of surface fault traces can contribute to the accurate location of the foci of future strong mainshocks in the Mediterranean and to an estimation of their sizes. For this purpose, globally valid relations between fault parameters based on geological observations (surface fault length,
L
S
, and fault slip,
u
S
) and measures of mainshock size (mainshock magnitude, subsurface fault length,
L
, and fault slip,
u
) are proposed.
An inverse cascade explanation for the power-law frequency-area statistics of earthquakes, landslides and wildfires
Authors: Malamud Bruce D. , Turcotte Donald L.
Published: April 2008

Frequency-magnitude statistics for natural hazards can greatly help in probabilistic hazard assessments. An example is the case of earthquakes, where the generality of a power-law (fractal) frequency-rupture area correlation is a major feature in seismic risk mapping. Other examples of this power-law frequency-size behaviour are landslides and wildfires. In previous studies, authors have made the potential association of the hazard statistics with a simple cellular-automata model that also has robust power-law statistics: earthquakes with slider-block models, landslides with sandpile models, and wildfires with forest-fire models. A potential explanation for the robust power-law behaviour of both the models and natural hazards can be made in terms of an inverse-cascade of metastable regions. A metastable region is the region over which an ‘avalanche’ spreads once triggered. Clusters grow primarily by coalescence. Growth dominates over losses except for the very largest clusters. The cascade of cluster growth is self-similar and the frequency of cluster areas exhibits power-law scaling. We show how the power-law exponent of the frequency-area distribution of clusters is related to the fractal dimension of cluster shapes.
Crustal stress crises and seismic activity in the Italian peninsula investigated by fractal analysis of acoustic emission, soil exhalation and seismic data
Authors: Paparo Gabriele , Gregori Giovanni P. , Poscolieri Maurizio , Marson Iginio , Angelucci Francesco , Glorioso Giorgia
Published: April 2008

Crustal stress can be monitored by acoustic emissions (AE, ultrasound), which give an indication of whether a physical system is subject to stress, either of tectonic or endogenous origin. AE intensity critically depends on the damping of the signal; however, AE signals are clear indicators of the fatigue state of the crustal structures constituting the AE source. This aspect can be studied by fractal analysis of AE time series; these are, however, not suited for earthquake forecasting, as they only denote a changing state involving large lithospheric volumes. Several case histories from Italy show that an increased high-frequency AE activity (200 kHz) occurs approximately seven to eight months in advance of large earthquakes that affect areas of a few hundred kilometres radius, and an increased low-frequency AE activity (at 25 kHz) is observed several weeks in advance. Low-frequency AE also correlate with soil exhalation (water-well chemistry) and CH
4
, whereas fractal analysis of AE signals recorded close to a ‘future’ epicentral area gives a clear indication of the evolution of the system from about two months before the mainshock. This suggests that systematic monitoring of crustal stress variations may be used for assessing the time evolution of seismic activity.
Crustal stress and seismic activity in the Ionian archipelago as inferred by satellite- and ground-based observations, Kefallinìa, Greece
Authors: Poscolieri Maurizio , Lagios Evangelos , Gregori Giovanni P. , Paparo Gabriele , Sakkas Vassilis A. , Parcharidis Issaak , Marson Iginio , Soukis Konstantinos , Vassilakis Emmanuel , Angelucci Francesco , Vassilopoulou Spyridoula
Published: April 2008

Different observational techniques are compared in order to investigate possible correlations in seismic activity. The study site is the island of Kefallinà (Greece), where measurements available included (1) DInSAR, DGPS, and DEM data, (2) soil exhalation measured by monitoring Radon (Rn) well content, and (3) acoustic emissions (AE) at high and low frequency (point-like records with high temporal resolution). AE records provide: (1) relative time variation of the applied stress intensity and (2) the state of fatigue of stressed rock volumes, the AE source. Our results indicate that the large spatial scale (poor time resolution) may be considered quite satisfactory, whereas fractal analysis of the AE time series displayed some discrepancies when compared to analogous investigations in the Italian Peninsula. Therefore, some refinement is needed in order to reach more precise interpretations of the relevant information available with this kind of data. However, both sets of observations appear in agreement with each other, although more exhaustive investigations would require a suitable array of point-like AE and Rn (or other) measuring sites, as well as longer data series. The latter are particularly helpful for detailed interpretations of the different occurrences within tectonically complex settings where crustal stress crises are marked by various types of geological phenomena.
Nonlinear Science issues in the dynamics of unstable rock slopes: new tools for rock fall risk assessment and early warnings
Authors: Zvelebil Jiří , Paluš Milan , Novotná Dagmar
Published: April 2008

Time series of displacement data from unstable rock slopes contain ‘hidden’ information about the dynamics of slope failure. This information cannot be found when using the current linearly causal paradigm based on analytical methods, but is revealed when numerical and graphical methods from the toolbox of the Nonlinear Sciences are applied. The occurrence of fractal patterns, which suggests a qualitative difference between intrinsic slope movement dynamics of time series from the near-to-equilibrium and the far-from-equilibrium dynamical states of slope failure systems, is an example of such a ‘hidden’, diagnostically important indicator. It helps to identify the stage of immediate danger of rock fall occurrence, just in time to launch an efficient early warning. Phase portrait and correlograms of time series proved to be suitable for earlier revelation of transitions from the near-to-equilibrium to the far-from-equilibrium dynamical states, as well as for helping to distinguish between intrinsic slope movement dynamics and climatically driven reversible deformation activity.
Aptian sedimentation: an example of interaction between tectonics and eustatics in Central Tunisia
Authors: Chaabani Fredj , Razgallah Salwa
Published: April 2008

To reconstruct the sequence evolution and distribution of deposits during the Aptian in the Central Tunisian platform, the present study was mainly based on a sedimentological approach. The palaeogeographical reconstruction shows an inner and an external platform separated by the highs of the Central Tunisian islands. These are characterized by carbonate-dominated deposits evolving towards the north into a pelagic marl-dominated sedimentation. The NW-SE-to east-west-directed faults show an important sedimentary control. In fact, a system of tilted blocks located towards the SW characterizes a large part of the platform. The subsidence evolution during the Aptian was marked by a recovery of extensional tectonics. Finally, some halokinetic vertical movements were responsible for several highs during the latest Barremian. The Central Tunisian platform evolution was controlled by drift of the African platform during the opening of the Atlantic Ocean.
Fluid geochemistry versus tectonic setting: the case study of Morocco
Authors: Tassi F. , Vaselli O. , Moratti G. , Piccardi L. , Minissale A. , Poreda R. , Delgado Huertas A. , Bendkik A. , Chenakeb M. , Tedesco D.
Published: April 2008

This paper presents the results of an extensive chemical and isotopic investigation on natural thermal and cold fluids (spring waters and associated gases) discharging throughout the main geological domains of Morocco. The chemical features of the thermal springs are mainly dependent on rock dissolution involving Triassic evaporite formations, producing either Na-Cl or Ca-SO
4
composition, although mixing with shallower connate high-saline waters in Neogene post-orogenic sedimentary layers cannot be ruled out. Only in the Moroccan Meseta and Anti-Atlas domains have spring discharges probably undergone equilibration as a result of water-rock interaction in granites. Of the chemical and isotopic features of the gas seeps,
3
He/
4
He ratios and δ
13
C-CO
2
values indicate the occurrence of a significant contribution of mantle-derived gas, especially at Oulmès (Moroccan Meseta) and Tinejdad-Erfoud (Anti-Atlas), where associated waters are found to equilibrate at relatively high temperatures (
c.
130 °C). These areas are also characterized by the presence of Pliocene to Quaternary basaltic volcanic rocks. Thermal discharges located along the Rif front and related to the NE-SW-oriented main strike-slip faults are associated with a CH
4
- and/or N
2
-rich gas phase, derived respectively from a crustal or an atmospheric source. Some of them have significant contents of
3
He that could indicate the rising of mantle fluids. Such a striking isotopic signature, which is not related to any recent volcanism visible at surface, is likely to be associated with cooling magma at depth related to transpressive fault systems. Similarly, in the northeastern area, the small, although significant, enrichment of
3
He in the gas discharges seeping out along the Nekor seismic active fault and related to Pliocene-Quaternary basalts also suggests a deep-seated (magmatic) contribution. The distribution of thermal discharges is strongly related to the main active tectonic structures of Morocco. Moreover, this study indicates the presence of deep active tectonic structures in areas until now considered as stable. In particular, the NE-SW-trending Nekor fault may be part of a major system that extends to the Moroccan Meseta and into the Smaala-Oulmès fault system, thus emerging as a deep structure with crustal significance.
Chronology of the Middle-Upper Pliocene succession in the Strongoli area: constraints on the geological evolution of the Crotone Basin (Southern Italy)
Authors: Capraro L. , Consolaro C. , Fornaciari E. , Massari F. , Rio D.
Published: April 2008

The aim of this study is to reconstruct the evolution of the Strongoli area, a critical sector of the Crotone Basin (Calabria, Southern Italy), where a thick Middle-Upper Pliocene marine succession is present. The Strongoli succession shows prominent changes in the sedimentary environment that are partly forced by tectonics. Major tectonostratigraphic events have been recognized that might correlate with spreading pulses in the back-arc Tyrrhenian Sea. In particular, we demonstrate that a dramatic basinal collapse at
c.
2.3 Ma correlates with the so-called ‘Calabrian transgression’
Auctorum
and is close in age to the oceanization of the Marsili Basin.
Active faults and inferred seismic sources in the San Vito lo Capo peninsula, northwestern Sicily, Italy
Authors: Tondi E. , Zampieri D. , Giunta G. , Renda P. , Alessandroni M. , Unti M. , Giorgianni A. , Cello G.
Published: April 2008

Two independent active faults, capable of generating medium-sized earthquakes in the San Vito lo Capo peninsula, northwestern Sicily (Italy) have been identified as a result of detailed field studies. In western Sicily, instrumental seismicity is low; in fact, except for the 1968 Belice earthquake (Ms = 5.4), historical records indicate that this area is relatively quiescent. Most of the seismicity is in the offshore sector of the Sicilian Maghrebian Chain, which is characterized by several medium- to low-magnitude events. The main shock of the 2002 Palermo seismic sequence (Mw = 5.9) represents the largest earthquake felt in the area in recent years. The deformation pattern characterizing the most recent faults mapped in northwestern Sicily includes a grid of high-angle faults consisting of major east-west-striking right-lateral and north-south-striking left-lateral features. This fault grid is related to a regional transcurrent right-lateral shear zone, here named the UEKA shear zone, bounded to the north by the Ustica-Eolie fault and to the south by the Kumeta-Alcantara fault. The UEKA shear zone accommodates the regional strain induced by the current stress field acting in the area, which, as emerges from both structural and seismological data, is characterized by a NW-SE-striking main compression.
Characterization of permeability distributions in six lithofacies from the Helsby and Wilmslow sandstone formations of the Cheshire Basin, UK
Authors: Bloomfield J. P. , Moreau M. F. , Newell A. J.
Published: April 2008

The lithofacies and permeability structure of the Abbey Wood borehole, near Delamere, Cheshire, UK, have been investigated so that permeability distributions can be established for characteristic sandstone lithofacies in the Permo-Triassic sandstone aquifer. The borehole penetrates the Helsby Sandstone and Wilmslow Sandstone formations and six major facies (coarse- and fine-grained fluvial channel fill sandstones, sandy sabkha, sand sheet and dune aeolian sandstones, and a massive sandstone facies) and one minor lithofacies, a mudstone facies, have been identified. The permeability distributions for each lithofacies show subtle systematic differences. The two fluvial sandstone facies and the massive sandstone facies have systematically lower permeabilities than the aeolian sandstones, and within the aeolian sandstones the sand sheet and dune sandstones appear to be systematically more permeable than the sabkha facies. Statistical tests on the permeability distributions of each facies indicate that the distributions are statistically distinct and so support the lithofacies classification.
Towards understanding the Dumfries Basin aquifer, SW Scotland
Authors: Akhurst M. C. , Ball D. F. , Brady L. , Buckley D. K. , Burns J. , Darling W. G. , MacDonald A. M. , McMillan A. A. , Ó Dochartaigh B. É. , Peach D. W. , Robins N. S. , Wealthall G. P.
Published: April 2008

The Dumfries Basin aquifer supports groundwater abstraction for public supply, agriculture and industry. Abstraction is concentrated in the western part of the basin, where falling groundwater levels and deteriorating water quality both reflect the effects of intense pumping. There are two bedrock units: a predominantly breccia-coarse sandstone sequence in the west, interfingering with a predominantly sandstone sequence in the NE and east. The basin is bounded by weakly permeable Lower Palaeozoic rocks, and is largely concealed by variable superficial deposits. Surface water flows onto the basin from the surrounding catchment via the Nith and the Lochar Water and their respective tributaries. Direct rainfall recharge occurs via superficial sands and gravels, especially in the north, and discharge is predominantly to the rivers in the central area rather than the sea. A picture is developing of two main aquifer types within the basin: the high-transmissivity western sector underlain by a fracture-flow system with younger water and active recharge and a high nitrate content, compared with the east where groundwater residence times are longer and the storage capacity is higher.
DC electrical properties of Permo-Triassic sandstone
Authors: Taylor Steve , Barker Ron
Published: April 2008

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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.
Growth of continental plateaus by channel injection: models designed to address constraints and thermomechanical consistency
Authors: Medvedev S. , Beaumont C.
Published: April 2008

Weak, possibly partially molten, middle crust may exist and deform by channel flow beneath continental plateaus, thereby significantly influencing their dynamics. The role of channel flows in the transition zone between the plateau and the foreland is, however, unclear. We develop successively more complete approximate models for the channel injection (CI) mode in which differential pressure pumps channel material from beneath the plateau into the transitional crust, which thickens it and widens the plateau. The motivation is to improve our understanding of the controls on the growth of continental plateaus and the interactions in the transition zone, and to gain more insight into the results of more complex numerical models. In model CI-1, a channel with constant viscosity and thickness exists in the transitional crust and the pumped material accretes/freezes above and below the channel. Although results compare favourably with the geometry of some natural examples, this model is incomplete because the connection between the transition zone and the plateau is not considered. Model CI-2 includes a decrease in channel viscosity when the channel depth exceeds a critical value,
D
*, a proxy for onset of melt weakening or low viscosities at high temperatures. The model completes the connection to the plateau, but relies on the arbitrary choice of
D
*. Model CI-3 is more physically based, and considers the channel viscosity and thickness to depend on temperature, calculated by an associated thermal model that includes radioactive self-heating, and advection of heat by channel material. This model demonstrates self-consistent plateau widening if the channel viscosity decreases at the critical temperature,
T
*. Acceptable comparisons with the topography of Tibet are achieved with transition zone viscosities that decrease from 10
19
−10
22
Pa s to subplateau values of 10
18
–10
19
Pa s, with
T
* of 700−750°C. Additional analyses and tests are used to determine the range of parameter values for which CI models are both internally consistent and compatible with observations. Additional modes of deformation in the transition zone, viscous thickening (VT) and plastic translation (PT), may also be important.
Ductile extrusion in continental collision zones: ambiguities in the definition of channel flow and its identification in ancient orogens
Authors: Jones R. R. , Holdsworth R. E. , Hand M. , Goscombe B.
Published: April 2008

Field characteristics of crustal extrusion zones include: high-grade metamorphism flanked by lower-grade rocks; broadly coeval flanking shear zones with opposing senses of shear; early ductile fabrics successively overprinted by semi-brittle and brittle structures; and localization of strain to give a more extensive deformation history within the extrusion zone relative to the flanking regions. Crustal extrusion, involving a combination of pure and simple shear, is a regular consequence of bulk orogenic thickening and contraction during continental collision. Extrusion can occur in response to different tectonic settings, and need not necessarily imply a driving force linked to mid-crustal channel flow. In most situations, field criteria alone are unlikely to be sufficient to determine the driving causes of extrusion. This is illustrated with examples from the Nanga Parbat-Haramosh Massif in the Pakistan Himalaya, and the Wing Pond Shear Zone in Newfoundland.
Did the Himalayan Crystallines extrude partially molten from beneath the Tibetan Plateau?
Authors: Harrison T. Mark
Published: April 2008

The hypothesis that the Himalayan crystalline core originated by ductile channel flow of partially molten mid-crust from beneath the Tibetan Plateau is critically reviewed. The proposal that widespread shallow anatexis exists beneath southern Tibet today is inconsistent with numerous observations (e.g. ‘bright spots’ restricted to a single rift and evidence that they represent aqueous fluids rather than molten silicate; the seismogenic southern Tibetan Moho;
3
He/
4
He data indicating the presence of mantle heat and mass in the rift valley; the likelihood that any melt present is due to late Neogene calc-alkaline magmatism; the lack of Tertiary migmatites in the crustal section exposed in the uplifted rift flank of the Yangbajain graben; the lack of Gangdese zircon xenocrysts in the Greater Himalayan Crystallines (GHC); and the broadly coherent stratigraphy in the GHC). Evidence advanced in support of this model is equally or better explained as resulting from localized Neogene calc-alkaline magmatism. A recently developed rapid denudation/channel flow model does explain key petrogenetic and thermochronological features of the Himalaya, but is inconsistent with several geological constraints, most notably the small portion of the collision front over which focused erosion has localized exposure of the GHC. It is concluded that no evidence has yet been documented that requires the existence of partially molten crust flowing in a channel from beneath the Tibetan Plateau to form the Himalaya.
Pulsed channel flow in Bhutan
Authors: Hollister L. S. , Grujic D.
Published: April 2008

We summarize our results from Bhutan and interpret the Greater Himalaya Sequence (GHS) of Bhutan, together with a portion of the underlying Lesser Himalaya Sequence, in the context of recently published channel flow models. For the GHS rocks now exposed in Bhutan the depth for beginning of muscovite dehydration melting (approximately 750°C at 11 kbar) and associated weakening of these rocks is constrained by geobarometry to be at about 35–45 km. The location of initial melting was down-dip and over 200 km to the north of Bhutan. Melt was produced and injected into ductilely deforming metamorphic rocks as they were extruded towards the south between the Main Central Thrust (MCT) and the South Tibetan Detachment zones. The lateral flow of low viscosity rocks at these depths occurred under southern Tibet between 22 Ma and 16 Ma. Subsequently, the channel rocks decompressed from 11 to 5 kbar (from 35 km to a depth of 15 km), but maintained high temperatures, between about 16 Ma and 13 Ma. The data from Bhutan are consistent with channel flow models if there were several pulses of channel flow. The first, between 22 and 16 Ma, produced the rock seen in the lower half of the GHS of Bhutan. A second pulse, which is cryptic, is inferred to have led to the uplift and exhumation of the MCT zone. A third, in central Bhutan, is exposed now as the hanging wall of the Kakhtang thrust, an out-of-sequence thrust that was active at 12–10 Ma. The latter two pulses likely broke around a plug at the head of the first pulse that was formed where the melt in the channel had solidified.
The Malashan gneiss dome in south Tibet: comparative study with the Kangmar dome with special reference to kinematics of deformation and origin of associated granites
Authors: Aoya M. , Wallis S. R. , Kawakami T. , Lee J. , Wang Y. , Maeda H.
Published: April 2008

Despite the importance of Tethys Himalayan or North Himalayan gneiss domes for discussing extrusive flow of the underlying Greater Himalayan Sequence, these metamorphic domes in general remain poorly documented. The main exception is the Kangmar dome. The Malashan metamorphic complex, a newly documented North Himalayan gneiss dome, is shown to have strong similarities with the Kangmar dome, suggesting that the North Himalayan gneiss domes have the following features in common: (i) Barrovian-type metamorphism with grade increasing towards a centrally located two-mica granite; (ii) the presence of two dominant ductile deformation stages, D
1
and D
2
, with D
2
showing an increasing strength towards the granite contacts; and (iii) the development of a strong D
2
foliation (gneissosity) in the outermost part of the granite cores. In addition, field and bulk-chemical studies show: (i) D
2
is associated with a dominant top-to-the-north sense of shear (in disagreement with the most recent kinematic studies in Kangmar dome); (ii) the deposition age of associated metasediments is upper Jurassic suggesting that the Malashan dome is located not at the base, but within the middle section of the Tethys Himalaya; and (iii) in contrast to the Kangmar granitic gneiss that is interpreted as Indian basement, three granitic bodies in Malashan all formed as young intrusive bodies during the Himalayan orogeny. These results suggest that the formation mechanism of the North Himalayan gneiss domes needs to be re-evaluated to test the rigidity of the hanging wall assumed in channel flow models.