bluuebunny/crossref_metadata_2025 huggingface dataset:
Ichnotaxonomy and ichnostratigraphy of chambered trace fossils in palaeosols attributed to coleopterans, ants and termites
Authors: Genise Jorge F.
Published: April 2008

Most recorded trace fossils in palaeosols are burrows and chambers attributed to bees, ants, termites and coleopterans. Ichnogenera attributed to bees are grouped in the ichnofamily Celliformidae, whereas those attributed to ants, termites and coleopterans are included herein in the new ichnofamilies Pallichnidae, Krausichnidae and Coprinisphaeridae respectively. Shape, type of wall, fillings and associated burrows of chambers are the main morphological ichnotaxobases used for this classification; they are weighed with regard to the behaviour and architecture of the supposed trace-makers. Coprinisphaeridae are spherical, pear-shaped or ovoid structures, having active or passive fillings and constructed walls. The ichnogenera included are:
Fontanai, Coprinisphaera, Eatonichnus, Monesichnus, Teisseirei
and
Rebuffoichnus
, attributed to coleopterans. The similar Pallichnidae show lined or structureless walls, and include
Pallichnus, Fictovichnus
and
Scaphichnium
, also attributed to coleopterans. The Krausichnidae constitutes trace fossils composed of chambers of different shapes interconnected by burrow systems of inconsistent diameter or isolated chambers associated with burrow systems of different diameters. The Krausichnidae include
Attaichnus, Parowanichnus, Krausichnus, Archeoentomichnus, Tacuruichnus, Vondrichnus, Fleaglellius, Termitichnus
and
Syntermesichnus
, attributed to ants and termites. The stratigraphic ranges of insect ichnotaxa in palaeosols are reviewed and compared with the body fossil record of potential tracemakers, revealing that in most cases insect trace and body fossils show similar ranges. As stated by earlier authors, the Cretaceous was a critical period during which the oldest body fossils of dung-beetles, bees, termites and ants are recorded, whereas the trace fossils of these groups are recorded from this period or shortly after, during Cenozoic times.
Motion of the Ontong Java Plateau in the hot-spot frame of reference: 122 Ma-present
Authors: Kroenke L. W. , Wessel P. , Sterling A.
Published: April 2008

A new model of Pacific absolute plate motion between 140 and 0 Ma, generated in the fixed hot-spot frame of reference, has been used to track palaeogeographic positions of the Ontong Java Plateau (OJP) from the time (
c.
122 Ma) and location (
c.
43°S) of its formation to its present location north of the Solomon Islands. The resulting OJP seafloor flow-line suggests that changes in Pacific plate motion, passage over hot spots and Pacific Rim tectonism all have influenced the continuing structural development and deformation of the plateau. Satellite-derived gravity, bathymetry and Rayleigh-wave tomography potentially reveal the structural fabric of the OJP and adjoining Nauru Basin, including the orientation of probable fracture zones, location of possible relict spreading centres and the presence of a thick lithospheric root, as well as possible later hot-spot-related modification of the fabric. The most recent phase of OJP deformation, which began about 6 Ma, accelerated at 2.6 Ma and continues today, has resulted in the uplift of the islands of Malaita and Santa Isabel, and the formation of the Malaita Anticlinorium, with slip along the old fracture zones possibly triggering submarine canyon formation on the NE side of the OJP. This collision-related deformation also is probably responsible for the ongoing uplift and tilting of the islands of Nauru and Banaba NE of the OJP high plateau.
Calcareous nannofossils from ODP Leg 192, Ontong Java Plateau
Authors: Bergen J. A.
Published: April 2008

Middle Miocene-upper lower Aptian calcareous nannofossils were recovered from Sites 1183–1187 drilled by Ocean Drilling Project Leg 192 on the Ontong Java Plateau. Nannofossil biostratigraphy indicates the presence of six unconformities among the five Leg 192 sites. These are: (1) between the lowermost Albian and upper middle Albian; (2) between the upper Albian and middle Coniacian; (3) within the lower Maastrichtian; (4) between the lower upper Maastrichtian and basal Danian; (5) within the upper Palaeocene; and (6) between the Oligocene and Miocene.

Previous drilling before Leg 192 on the Ontong Java Plateau and in the SW Pacific (Legs 30 and 130) indicated two episodes for major emplacement of basement during the earliest Aptian and Turonian. The Leg 192 drilling was not able to confirm either of these episodes, but instead indicated that the emplacement of basement on the Ontong Java Plateau was relatively continuous from the latest early Aptian to latest Aptian. Results from Sites 1184 and 1185 indicate the possibility of another magmatic episode during the middle Eocene (Zone NP16).
Origin and evolution of magmas on the Ontong Java Plateau
Authors: Fitton J. Godfrey , Godard Marguerite
Published: April 2008

The Early Cretaceous Ontong Java Plateau (OJP) represents by far the largest igneous event on Earth in the last 200 Ma and yet, despite its size, the OJP’s basaltic crust appears to be remarkably homogeneous in composition. The most abundant rock type is a uniform low-K tholeiite, represented by the Kwaimbaita Formation on Malaita and found at all but one of the Deep Sea Drilling Project (DSDP) and Ocean Drilling Program (ODP) drill sites on the plateau and in the adjacent basins. This is capped by a thin and geographically restricted veneer of a slightly more incompatible-element-rich tholeiite (the Singgalo Formation on Malaita and the upper flow unit at ODP Site 807), distinguished from Kwaimbaita-type basalt by small but significant differences in Sr-, Nd- and Pb-isotope ratios. A third magma type is represented by high-Mg (Kroenke-type) basalt found in thick (> 100 m) successions of lava flows at two drill sites (ODP Sites 1185 and 1187) 146 km apart on the eastern flank of the plateau. The high-Mg basalt is isotopically indistinguishable from Kwaimbaita-type basalt and may therefore represent the parental magma for the bulk of the OJP. Low-pressure fractional crystallization of olivine followed by olivine+augite+plagioclase can explain the compositional range from high-Mg Kroenke-type to Kwaimbaita-type basalt. The Singgalo-type basalt probably represents slightly smaller-degree, late-stage melting of an isotopically distinct component in the mantle source. Primary magma compositions, calculated by incremental addition of equilibrium olivine to aphyric Kroenke-type basalt glass, contain between 15.6% (in equilibrium with Fo
90
) and 20.4% (Fo
92
) MgO. Incompatible-element abundances in the primary OJP magma can be modelled by around 30% melting of a peridotitic primitive-mantle source from which about 1% by mass of average continental crust had previously been extracted. This large degree of melting implies decompression of very hot (potential temperature >1500°C) mantle beneath very thin lithosphere. The initiation of an exceptionally large and hot plume head close to a mid-ocean ridge provides the best explanation for the size, homogeneity and composition of the OJP, but is difficult to reconcile with the submarine eruption of virtually all of the basalt so far sampled.
Large igneous province magma petrogenesis from source to surface: platinum-group element evidence from Ontong Java Plateau basalts recovered during ODP Legs 130 and 192
Authors: Chazey William J. , Neal Clive R.
Published: April 2008

A total of 16 Ontong Java Plateau (OJP) basalt samples from Ocean Drilling Program Legs 192 and 130 were analysed for major, trace and platinum-group elements (PGEs; Ir, Ru, Rh, Pt and Pd). Major- and trace-element compositions determined by our study confirm Leg 192 shipboard analyses that indicated a new group of more primitive or ‘Kroenke-type’ basalts, with higher MgO, Ni and Cr, and lower incompatible-element, abundances than the more common Kwaimbaita-type basalts. The PGE abundances quantified here extend the range of the continuum of compositions found in previously analysed OJP basalts and are similar to those present in some komatiites. The PGEs, therefore, cannot be used to differentiate definitively between OJP basalts groups. The two samples analysed from Leg 130 (one from Site 803 and one from Site 807) are akin to the Kwaimbaita-type basalts.

Low-temperature alteration has not affected Pd abundances in the Leg 192 basalts as it has in the Solomon Island and the Leg 130 samples. Elemental abundances and ratios along with petrography reveal that the OJP basalts have not experienced sulphide saturation. Positive correlations of Ir and Ru with Cr and Ni attest to the lithophile behaviour of the PGEs and lend more credence to studies suggesting compatibility of these elements in oxide and silicate phases, such as Cr-spinel and olivine. Estimates of sulphur abundance in the mantle, degree of partial melting and pressure of melt initiation were used in conjunction with the model of Mavrogenes & O’Neill to calculate a minimum initial excess temperature of +185–+235°C (1465–1515°C at 3.5–4.0 GPa) above ambient mantle for the OJP source. This is in broad agreement with a fossil geotherm preserved in megacrysts and peridotite xenoliths found in pipe-like intrusives of alnöite that outcrop on the island of Malaita, Solomon Islands. Using the PGEs as a guide, the OJP basalts were modelled using a three-source component melt mix: a 10% garnet peridotite melt of primitive mantle composition, which then passed through the garnet-spinel transition and melted a further 20%, a 30% partial melt of fertile upper mantle and 0–1% of outer core material. The core component was included only in the plume source, and the ratio of plume source to upper mantle source was 19: 1. It is evident from this study that the PGE contents of at least some of the OJP basalts are too high to be generated by primitive mantle sources alone. A PGE-enriched component is required and we suggest that this is outer core material. While a sulphide-rich mantle component could also increase the PGE abundances (assuming that the sulphide is exhausted during partial melting), the sulphur-undersaturated nature of these basalts argues against this. Variations in the amount of outer core in the source (from 0 to 1 wt%) and degree of fractional crystallization can account for the entire range in PGE abundances of OJP basalts.
Accretionary-lapilli-bearing pyroclastic rocks at ODP Leg 192 Site 1184: a record of subaerial phreatomagmatic eruptions on the Ontong Java Plateau
Authors: Thordarson Thor
Published: April 2008

Detailed analysis of lithologies and lithofacies associations within the 337.7 m thick basement volcaniclastic succession, recovered during Ocean Drilling Program (ODP) Leg 192 at Site 1184 on the Ontong Java Plateau, shows that in bulk it is made up of pyroclastic deposits of phreatomagmatic origin. The succession is essentially made up of two lithologies: lapilli tuff (59% of the total recovered core length) and tuff (34%), consisting almost entirely of juvenile clasts (>97%) and containing significant amounts of matrix-supported accretionary and/or armoured lapilli clasts. The evidence indicates that the succession was formed by at least six (and perhaps as many as 10) major phreatomagmatic eruptions that were subaerial and associated with the main phase of volcanism on the Ontong Java Plateau.
Phreatomagmatic eruptions on the Ontong Java Plateau: an Aptian
40
Ar/
39
Ar age for volcaniclastic rocks at ODP Site 1184
Authors: Chambers Lynne M. , Pringle Malcolm S. , Fitton J. Godfrey
Published: April 2008

The discovery of a thick (337.7 m drilled) succession of volcaniclastic sediments at Ocean Drilling Program (ODP) Site 1184, on the eastern salient of the Ontong Java Plateau (OJP), shows that at least part of the plateau formed at or near sea level. All the other parts of the OJP that have been drilled or are exposed on land are composed of basaltic lava flows erupted in a deep-marine environment. The composition of the volcaniclastic rocks at Site 1184 is essentially indistinguishable from that of basaltic lava flows recovered from the other drill sites on the OJP, suggesting that the eastern salient formed during the same magmatic event (at approximately 120 Ma) that formed the main part of the plateau. A steep (−54°) magnetic inclination preserved in the volcaniclastic succession is consistent with an Early Cretaceous age, but rare nannofossils recovered from the volcaniclastic rocks suggest a much younger Eocene age. In order to resolve this paradox, we attempted to date the succession by the
40
Ar/
39
Ar technique, even though the rocks are highly altered. Two samples of feldspathic material separated from basaltic clasts give
minimum
age estimates of
c.
74 Ma. The basaltic clasts have compositions similar to that of their host rocks and are therefore probably cognate. A weighted average of the results of total fusion experiments on four or five small euhedral plagioclase crystals separated from the matrix of the volcaniclastic rocks at each of four levels in the lower part of the succession gave a value of 123.5 ± 1.8 Ma, and this probably represents a reasonable estimate of the age of eruption. Although not very precise, the
40
Ar/
39
Ar results are the best that presently can be obtained from such altered rocks. They rule out an Eocene age for the volcaniclastic succession at Site 1184, and we suggest that the Eocene nannofossils were introduced through contamination, probably along fractures.
Compositional variability in lavas from the Ontong Java Plateau: results from basalt clasts within the volcaniclastic succession at Ocean Drilling Program Site 1184
Authors: Shafer John T. , Neal Clive R. , Castillo Paterno R.
Published: April 2008

Tholeiitic basalts have been recovered from drill sites in different locations on the Ontong Java Plateau (OJP) and are remarkably homogeneous across this large igneous province. The most abundant basalt type is represented by the Kwaimbaita Formation on Malaita in the Solomon Islands, where it is capped by the isotopically distinct and slightly more incompatible-element-enriched basalt of the Singgalo Formation. Ocean Drilling Program (ODP) Leg 192 drilled five sites on the OJP, four of which penetrated basement lava successions. All basalt recovered during Leg 192 is chemically and isotopically indistinguishable from Kwaimbaita-type lavas.

Site 1184 of ODP Leg 192 is situated on the eastern salient of the OJP, and is unique because the recovered volcaniclastic succession contains the first conclusive evidence for emergence of part of the OJP above sea level. Within this succession are clasts of basaltic material. We report the major element-, trace-element and isotopic compositions of 14 moderately to highly altered basalt clasts. On the basis of incompatible-element concentrations, specifically high field strength elements (HFSE) and rare earth elements (REE), four groups of clasts are defined. Group 1 clasts are similar to basalt from the Kwaimbaita Formation. Group 2 clasts show variable composition, but the heavy rare earth element (HREE) concentrations are similar to those of basalts from the Kwaimbaita Formation. Group 3 clasts have compositions similar to the high-MgO Kroenke-type basalt recovered during ODP Leg 192. Group 4 clasts are more evolved than the Kwaimbaita or Singgalo lavas, and contain deep negative Eu and Sr anomalies on primitive-mantle (PM)-normalized diagrams, as well as high concentrations of Nb, Ta and Th. Group 4 clasts also show a large fractionation of Nb from La and have (Nb/La)
PM
ratios of approximately 2. Sr-, Nd- and Pb-isotope ratios were measured on five clasts covering all four groups. Although the Sr- and Pb-isotope ratios exhibit some variability, which we attribute to alteration, the Nd-isotope ratios are within the field defined for Kwaimbaita-type lavas.

We conclude that most of the compositional variability displayed by these clasts is a result of alteration and that Ta appears to be the most immobile incompatible trace element. All of the clasts were derived from the mantle source that produced the Kwaimbaita-type and Kroenke-type basalts. Our data emphasize the widespread nature of Kwaimbaita-type basalt and show that the source region was active under both the eastern salient and the high plateau of the OJP.
Age and depth evidence for pre-exhumation joints in granite plutons: fracturing during the early cooling stage of felsic rock
Authors: Bankwitz P. , Bankwitz E. , Thomas R. , Wemmer K. , Kämpf H.
Published: April 2008

This chapter documents the fracture process associated with the early cooling stage of felsic magma. Characteristics of pre-exhumation joints include their spatial distribution in granite bodies, their fracture surface morphology, and geological and petrological evidence for the depth of fracture initiation. These characteristics allow inferences about the depth and the time of joint origin in the South Bohemian Pluton. The intrusion levels of currently exposed granites of the pluton were 7.4 km in the northern part and 14.3 km in the southern part.

Within the northern Mrákotín Granite (Boršov) early NNE joints propagated while the granite was at a temperature near the solidus, and, in part, magma was still being injected, post-dated by thin granite dykes along NNE joints. Evidence for the pre-exhumation initiation of these joints comes from the geochronological dating of these late-granite dykes (1–2 cm thick) at 324.9 Ma in age, which were creating their own rupture in the rock. The timing of the pluton emplacement at 330–324 Ma and the cooling ages of 328–320 Ma have been given by previous studies. From fluid inclusions within the late-granite dykes that occupy joint surfaces, the trapping depth of the analysed inclusions was calculated to be 7.4 km. Near the solidus H
2
O separates during the crystallization of anhydrous phases. The associated increasing H
2
O pressure can initiate the first cracks and can generate a small portion of new granitic melt, which forces the cyclic fracture propagation together with mobile, low-viscosity ‘residual melt’ input into the fracture.

The determination of the intrusion level and time at which the dykes began cooling provide evidence for the joint initiation at a depth of 7.4 km, which was connected with the level and process of final emplacement and early cooling of the Mrákotín Granite long before the main exhumation. At the earliest, the erosion of the upper rock pile, 7.4 km in thickness, started significantly after generation of the early joint sets. The NNE-trending joints are persistent in orientation throughout the South Bohemian Pluton, but the joint-surface morphology varies in all subplutons and occupies all sections of the stress intensity v. crack-propagation velocity curve (Wiederhorn-Bahat curve).
Using differential geometry to characterize and analyse the morphology of joints
Authors: Pollard D. D. , Bergbauer S. , Mynatt I.
Published: April 2008

Concepts of differential geometry are reviewed, and it is demonstrated through examples that the main joint surface, rib marks and hackle of a joint may be described using parametric representations such that the first and second fundamental forms fully characterize these surfaces. Other useful quantities are the unit normal vector, the principal normal curvatures, and the Gaussian and the mean curvature. Sufficiently close to any point on a surface the shape is planar, parabolic, elliptical or hyperbolic. The surface of a joint in chert and another in siltstone were scanned and the resulting data analysed. Although the main joint surface of the chert sample is approximately planar, it is composed of low-amplitude undulations with elliptical and hyperbolic forms. The unit normal vector does not vary by more than about 3.4° over this surface, which is consistent with the threshold angle for the initiation of hackle based on laboratory experiments. An individual hackle is found to be approximately helicoidal in shape, but only in the breakdown zone. Rib marks on the siltstone sample have distinct and similar morphologies, with a concave base and convex peak. Field and laboratory campaigns designed to test hypothese about the geometry of joints should use the principles and tools of differential geometry.
Palaeostress orientation inferred from surface morphology of joints on the southern margin of the Bristol Channel Basin, UK
Authors: Belayneh Mandefro
Published: April 2008

A field study of the orientation of surface features on joint planes has been carried out on the north Somerset coast along the southern margin of the Bristol Channel Basin (BCB), with the aim of inferring the palaeostress orientations. Surface features are very delicate structures on joint surfaces and when preserved give important clues regarding the direction of propagation of a joint and the interaction between the remote and local stresses.

In this chapter surface features (i.e. plumose structures and twist-hackle fringes) observed on joints in Liassic limestone beds interbedded with shales from the BCB are described and their implications regarding the evolution of the stress field operating during their formation considered. The results are then compared with the generally accepted model for the region of an anticlockwise rotation of the stress field. The incompatibility between N-S-directed remote compression and continually changing local stress caused by the local structures (folds and faults), inhomogeneities and the anisotropy created by rapidly alternating limestone and shale beds resulted in the master joints breaking down into en echelon cracks (twist-hackle fringes). Joints in thicker limestone beds show well-developed plumose structures and twist-hackle fringes, whereas in thinner beds the fringe zones extend from the top to the bottom of the bed. It is found that regardless of the orientation of the parent joint in which the twist-hackle fringes are contained, they generally strike E-W and show both right- and left-stepping arrangements.
The orientation distribution of single joint sets
Authors: Engelder Terry , Delteil Jean
Published: April 2008

Poles from line samples of systematic joint sets scatter about a mean pole because joints are neither perfectly planar nor parallel, and because measurement instruments are imprecise. Definition of a single joint set can be based solely on its orientation distribution and this distribution is assessed using two statistical parameters: square root of the circular variance (approximately equal to the standard deviation σ for two-dimensional (2D) data) and cone of confidence (α
95
for 3D data). The distribution for joints generated in the absence of tectonic deformation is well clustered with σ = 1.7° and α
95
= 0.48° based on a bootstrap sample of 50. Jointing associated with various fold styles show less clustering: the kink of a fault-bend fold (σ = 6.1° and α
95
= 1.7°), basement-cored anticline (σ = 3.5° and α
95
= 1.5°), regional joint set transected by a basement-cored anticline (σ = 5.2° and α
95
= 1.8°) and a buttress anticline (σ = 4.3° and α
95
= 1.7°). Jointing associated with local faulting tends to show even less clustering: a Cretaceous marl (σ = 8.3° and α
95
= 2.4°) and a glauconitic sandstone (σ = 8.6° and α
95
= 2.2°). The latter sample was drawn from two overlapping joint sets, indicating that distribution data greater than α
95
= 2.2° may signal overlapping joint sets.
Stress-controlled localization of deformation and fluid flow in fractured rocks
Authors: Sanderson David J. , Zhang Xing
Published: April 2008

The discrete-element method (UDEC — Universal Distinct Element Code) was used to numerically model the deformation and fluid flow in fracture networks under a range of loading conditions. A series of simulated fracture networks were generated to evaluate the effects of a range of geometrical parameters, such as fracture density, fracture length and anisotropy.

Deformation and fluid flow do not change progressively with increasing stress. Instability occurs at a critical stress and is charzacterized by the localization of deformation and fluid flow usually within intensively deformed zones that develop by shearing and opening along some of the fractures. The critical stress state may be described in terms of a driving stress ratio,
R
= (fluid pressure — mean stress)/1/2 (differential stress). Instability occurs where the
R
ratio exceeds some critical value,
R
C
, in the range – 1 to −2.

At the critical stress state, the vertical flow rates are characterized by a large increase in both their overal magnitude and degree of localization. This localization of deformation and fluid flow develops just prior to the critical stress state and may be characterized by means of multifractals. The stress-induced criticality and localization displayed by the models is an important phenomenon, which may help in the understanding of deformation-enhanced fluid flow in fractured rock masses.
Forensic applications of Raman spectroscopy to the non-destructive analysis of biomaterials and their degradation
Authors: Edwards Howell G. M.
Published: April 2008

An initial survey of the advantages and disadvantages of Raman spectroscopic techniques for application to forensic crime scene analysis in a geoscience context is followed by some illustrative examples that demonstrate the potential information which can be forthcoming from Raman spectral data and molecular characterization. A range of specimens is reported, including Egyptian human mummies, ice-mummified bodies, resins and ivories; all of these can be related through a geoscience context and the potential for forensic application is indicated.
Forensic geology of bone mineral: geochemical tracers for post-mortem movement of bone remains
Authors: Trueman Clive N.
Published: April 2008

The trace element chemistry of bone is rapidly altered post-mortem, and the post-mortem chemistry of bone mineral has been used successfully to discriminate between fossil bones removed from stratigraphically and spatially separate excavations. These techniques can be used to identify and protect scientifically or culturally sensitive artefacts. Measurable changes in the trace element composition of bone may occur within a few years of death. These changes show considerable potential for use in forensic investigations, particularly where post-mortem movement or scattering of bone remains has occurred. Early post-mortem alteration is complex, governed by a number of environmental variables, and measuring subtle changes in bone chemistry presents considerable analytical challenges. More work is needed in this area.
The use of plant hydrocarbon signatures in characterizing soil organic matter
Authors: Dawson Lorna A. , Towers Willie , Mayes Robert W. , Craig Julie , Väisänen R. Katariina , Waterhouse E. Clare
Published: April 2008

Resistant compounds associated with vegetation have potential for understanding and uniquely describing soil. Although much of the forensic identification of soils has focused on the mineral component, this study illustrates how the origin of the organic component can be a useful tool in soil identification. The epicuticular wax of most plants containts mixtures of hydrocarbons (mainly
n
-alkanes) and plant species differences are persistent. Evidence from three separate studies is compiled to show the validity of this approach. In the first example, on upland grassland vegetation, the
n
-alkane pattern of the soil at one site reflected that of the overlying grass, whereas at another site, it reflected that of the previous vegetation, heather. In the second study,
n
-alkane analysis data indicated the presence of heather in a buried horizon, matching independent evidence from pollen identification. The third study was one covering the whole of Scotland, using an unbiased grid-sampling strategy. Results show that the patterns in the soil
n
-alkane profiles reflected the overlying vegetation. Where this was not the case, the profiles matched previously grown vegetation. Such biomarker information, derived from plant wax signatures, coupled with soil spatial information, has potential in the unique identification of soils.
The use of diatom analysis in forensic geoscience
Authors: Cameron N. G.
Published: April 2008

Diatoms are unicellular, siliceous algae that are common in most aquatic environments. Their species composition is strongly related to water quality and aquatic habitats and, because of their silica skeletons, diatom valves can be well preserved and provide a record of past and present environmental conditions. Diatom remains are often diverse and can be identified with high taxonomic precision. These factors allow diatoms to be used in a range of applications in forensic geoscience. These include: the matching of environmental samples with items that have been in contact with water, the investigation of cases of drowning, and the identification of traces of diatomaceous materials used in the manufacture of materials or liquids. Recent developments include an assessment of the potential to use the succession of colonizing, attached diatom species in the determination of time of death. Advances in analytical quality control and the use of multivariate statistical techniques will improve the analysis, presentation and interpretation of diatom data in forensic investigations.
Geological storage of carbon dioxide
Authors: Baines Shelagh J. , Worden Richard H.
Published: April 2008

Carbon dioxide is the main compound identified as affecting the stability of the Earth’s climate. A significant reduction in the volume of greenhouse gas emissions to the atmosphere is a key mechanism for mitigating against climate change. Geological storage of CO
2
, or the injection and stabilization of large volumes of CO
2
in the subsurface in saline aquifers, existing hydrocarbon reservoirs or unmineable coal-seams, is one of the more technologically advanced options available. A number of studies have been carried out aimed at understanding the behaviour and long term fate of CO
2
when stored in geological formations.
Carbon dioxide sequestration in the Campine Basin and the adjacent Roer Valley Graben (North Belgium): an inventory
Authors: Laenen B. , Van Tongeren P. , Dreesen R. , Dusar M.
Published: April 2008

The Campine Basin offers a variety of potential CO
2
storage sites. Within the Roer Valley Graben area Triassic Buntsandstein rocks have an estimated CO
2
storage capacity of several hundred million tons. Mesozoic shales and younger sediments provide adequate sealing. Westphalian D sandstones may possess storage opportunities in the southern graben area, and the karstified/dolomitized parts of the Dinantian carbonates in the western sub-basin have an estimated CO
2
storage capacity of 130 × 10
6
tons. In places, the Dinantian reservoirs may be combined with carbonate reservoirs in the underlying Devonian strata. Sealing is provided by Namurian shales and Westphalian coals and shales. Along the western and southern edge of the basin the Dinantian reservoir is sealed by Cretaceous chalks and marls.

Besides aquifers, the available coal qualifies for CO
2
storage. Six Six methane target areas contain a producible enhanced coalbed methane (ECBM), volume of 53–79 × 10
9
m
3
. This provides a minimum CO
2
sequestration potential of 400 × 10
6
tons. ECBM development factors include the sedimentological setting of the coal sequence as well as changes in porosity, permeability and stress conditions induced by former mining activities. The CO
2
storage capacity in abandoned coalmines is limited. Nevertheless, CO
2
storage in the abandoned mines may be an option when it is combined with coalmine methane extraction or ECBM production in neighbouring areas.
Sedimentation, volcanism and subvolcanic intrusions in a late Palaeozoic intramontane trough (the Intra-Sudetic Basin, SW Poland)
Authors: Awdankiewicz Marek
Published: April 2008

The Intra-Sudetic Basin is a Late Palaeozoic intramontane trough, situated in the eastern part of the European Permo-Carboniferous Basin and Range Province. Within the basin, tectonics, sedimentation and volcanic/subvolcanic activity were intimately related. Tectonics controlled the location of the depositional and volcanic centres. Many volcanic centres with subvolcanic intrusions of rhyodacitic, rhyolitic and trachyandesitic composition were located close to the intra-basinal depositional troughs, where thick accumulations of sedimentary rocks partly obstructed the movement of magma to the surface. Differences in the structure and geometry of intrusions at separate subvolcanic complexes reflect the influence of different discontinuities, faults, margins of collapse structures, boundaries of contrasting lithologies in the country rocks and the volcanic structures.
Are laccolith complexes characteristic of transtensional basin systems? Examples from the Permo-Carboniferous of Central Europe
Authors: Breitkreuz Christoph , Mock Alexander
Published: April 2008

By comparing felsic laccolith complexes prominent in the Late Palaeozoic Ilfeld-, Saar-Nahe-, and Saale basins in Germany, a characteristic pattern related to transtensional tectonics is revealed. In contrast to the central magma feeding systems recognized so far for laccolith complexes, individual units of the Late Palaeozoic Central European complexes apparently were fed synchronously by numerous feeder systems arranged laterally in a systematic pattern.

The Ilfeld Basin is a small strike-slip pull-apart basin in the SE of the Hartz Mountains cogenetic with a neighbouring rhomb horst — the Kyffhäuser. The Ilfeld Basin represents a ‘frozen-in’ early stage of laccolith complex evolution, with small isolated intrusions and domes emplaced within a common level at the intersections of intra-basinal Riedel shears. In the Saar-Nahe basin, numerous medium-sized felsic subvolcanic to subaerial complexes emplaced at a common level have been recognized (Donnersberg-type laccolith complex). The magmatic evolution of the Halle Volcanic Complex in the Saale Basin culminated in the more or less synchronous emplacement of voluminous porphyritic laccoliths within different levels of a thick pile of Late Carboniferous sediments (Halle-type laccolith complex). Laccoliths in the Halle area might consist of several laccoliths typical of the Saar-Nahe Basin according to outcrop pattern and host sediment distribution.

The above-mentioned three post-Variscan Central European basins are characterized by a dextral transtensional tectonic regime, leading to a model for laccolith-complex evolution:

1

Initial lithosphere-wide faulting forms pathways for magma ascent.

2

Supracrustal pull-apart leads to the formation of a transtensional basin.

3

Continued transtension gives way to decompressional melting of the mantle lithosphere, especially if fertilized by previous magmatic activity, as in the Variscan orogen. The mantle melts rise into the lower crust to differentiate, mingle or cause anatexis.

4

The melts homogenize and start crystallizing in a mid- to upper-crustal magma chamber tapped during tectonic episodes.

5

The resulting SiO
2
-rich magmas ascend along major transtensional faults into thick sedimentary basin fill.

The amount of transtension and the amount of melt rising from the lithospheric mantle have a major influence on the type and size of the laccolith complex to be formed. Additionally, the presence of a mid- to upper crustal magma chamber is a prerequisite for the formation of the Donnerberg and Halle type laccolith complexes.
Emplacement textures in Late Palaeozoic andesite sills of the Flechtingen-Roßlau Block, north of Magdeburg (Germany)
Authors: Awdankiewicz Marek , Breitkreuz Christoph , Ehling Bodo-Carlo
Published: April 2008

During Late Palaeozoic times, andesite magmas intruded a 100-m thick sequence of Late Carboniferous lacustrine to alluvial siliciclastic rocks, sandwiched between folded Namurian sediments at the base and a thick, partly welded rhyolitic ignimbrite sheet at the top, in the Flechtingen area. An intrusive complex, comprising of two main sills up to 200 m thick and over 20 km in lateral extent, was formed (the Flechtingen Sill Complex, or the ‘lower andesites’, previously interpreted as lava flows). In the supposed feeder area the andesitic magmas locally pierced the ignimbrite seal, forming isolated pipes and domes (the ‘upper andesites’). Thickness variations of the sills suggest ponding of the andesite magma within former depositional troughs and syn-emplacement deformation of the host sequence with the formation of swells, basins and fault-bounded grabens at the top of the sills. Locally, thin ‘failed’ sills are present. In places, sill margins show domains of flattened and aligned vesicles and planar, sharp contacts to the host sediments. However, in many outcrops and drill cores the sill margins consist of variable andesite breccias and peperties. These fragmental rocks reflect auto- to quench-clastic brecciation of chilled andesite magma (
in situ
breccias and perlite), variable magma-sediment interactions and later breciation by hydrothermal fluids.
High-level volcanic-granodioritic intrusions from Zelezniak Hill (Kaczawa Mountains, Sudetes, SW Poland)
Authors: Machowiak Katarzyna , Muszyński Andrzej , Armstrong Richard
Published: April 2008

New petrological and geochemical data on high level (
c.
2 km
2
) silicic lava domes and laccoliths from the Kaczawa Mountains, Sudetes, SW Poland, are presented. The system comprises a carapace facies of exposed ignimbrites and spherlulitic rhyolites. Recovered core (drilled to 55 m) includes volcanic rocks ranging in composition from andesite to rhyodacite, and a plutonic facies of microgranite and granodiorite. Country rocks (greenschist-facies metavolcanogenic rocks) are contact metamorphosed to hornfels and cut by kersantite veins and a pipe breccia of diatremic origin. New
206
Pb-
238
U zircon mineral ages from the volcanic and granitic rocks yield ages of 315 to 316 Ma, making the Zelezniak Hill complex the oldest magmatic rocks so far dated in Avalonia.
Sill complex geometry and internal architecture: a 3D seismic perspective
Authors: Thomson Ken
Published: April 2008

Seismic volume visualization techniques demonstrate that saucer-shaped sill complexes consist of a series of radiating principal flow units rising from an inner saucer and fed by principal magma tubes. Such flow units contain smaller scale secondary flow units, each being fed by a secondary magma tube branching from the principal magma tube. This pattern is repeated down to scales of approximately 100 m with successively smaller flow units being fed from magma tubes repeatedly branching from higher order tubes. The data demonstrates that each sill complex is independently fed from a centrally located point source, that sills grow by climbing from the centre outwards and that peripheral dyking from the upper surface is a common feature. These features suggest a laccolith emplacement style involving peripheral fracturing and dyking during inner saucer growth and thickening.
Experimental constraints on the mechanics of dyke emplacement in partially molten olivines
Authors: Vinciguerra S. , Xiao X. , Evans B.
Published: April 2008

We investigated the mechanics of basalt dyke emplacement during laboratory deformation experiments at up to 300 MPa confining pressure and temperatures up to 1200 °C. Experiments have been conducted on two-phase samples of a basalt (MORB) dyke and a matrix of 90% San Carlos Olivine plus 10% MORB. No migration of MORB is observed when samples have been hot isostatically pressed. Conversely, significant diffusion of basalt into the matrix is found when a deviatoric stress is applied. Creep (80–160 MPa) and strain-rate experiments (from 3 × 10
−4
to 5 × 10
−5
s
−1
) induced melt propagation up to 50% of the initial dyke length/width ratio. The kinematics of deformation are essentially plastic and show a strong dependence on the load applied and the dyke geometry. Local pressure drops, due to dilatancy, are suspected to have enhanced melt migration.
Early dolomitization and fluid migration through the Lower Carboniferous carbonate platform in the SE Irish Midlands: implications for reservoir attributes
Authors: Nagy Zs. R. , Gregg J. M. , Shelton K. L. , Becker S. P. , Somerville I. D. , Johnson A. W.
Published: April 2008

Shallow-marine, Lower Carboniferous carbonate sequences of the SE Irish Midlands, close to the Leinster Massif, are intensely dolomitized. Fine-crystalline (<50 μm), planar-s (subhedral) dolomite is associated with evidence for evaporites, typical of arid peritidal sequences. However, stable isotope data suggest a diagenetic overprint. Volumetrically more important medium-crystalline (50–200 μm), planar-s and minor planar-e (euhedral) dolomites were precipitated from slightly modified Lower Carboniferous seawater. These dolomites replace open-marine intraclastic and bioclastic packstones and grainstones.

Length-slow, fibrous quartz partially replaces crinoids and fills dissolution cavities beneath peritidal strata. Associated dolomites are gradually enriched in
18
O downward through the underlying strata, suggesting vertical brine migration. The widespread occurrence of skeletal material replaced by chalcedony in open-marine wackestones and grainstones further to the west, within the Rathdowney Trend, suggests evaporite cementation in the Zn-Pb mineralized area.

Base-metal mineralization in the fractured Waulsortian ‘reservoir’ is associated with chloride-enriched brines (beyond that expected from seawater evaporation alone). The presence of evaporites in the Leinster Massif area suggests a possible source of the excess chloride. The dolomitizing brine may have contributed to the overall chemistry of the Zn-Pb mineralizing fluid and also to the distribution of porosity within the carbonate platform. An Arundian or younger age is suggested for the mineralization, based on the timing of evaporite cement emplacement, and this is compatible with numerical fluid-flow models of brine movement through the carbonate platform.

Dolomitization of Lower Carboniferous carbonate rocks of the Irish Midlands is comparable to diagenetic histories of several important dolomite petroleum reservoirs. This study provides an example that may be applied to petroleum exploration in similar geological settings.
Environmental impact of the nuclear fuel cycle
Authors: Ewing Rodney C.
Published: April 2008

Nuclear power provides approximately 17% of the world’s electricity, which is equivalent to a reduction in carbon emissions of ∼0.5 Gt of C/year. This is a modest contribution to the reduction of global carbon emissions, ∼6.5 Gt C/year. Most analyses suggest that in order to have a significant and timely impact on carbon emissions, carbonfree sources, such as nuclear power, would have to expand total energy production by a factor of three to ten by 2050. A three-fold increase in nuclear power capacity would result in a projected reduction in carbon emissions of 1 to 2 Gt C/year, depending on the type of carbon-based energy source that is displaced. This paper reviews the impact of an expansion of this scale on the generation of nuclear waste and fissile material that might be diverted to the production of nuclear weapons. There are three types of nuclear fuel cycles that might be utilized for the increased production of energy: open, closed, or a symbiotic combination of different reactor types (such as thermal and fast neutron reactors). Within each cycle, the volume and composition of the nuclear waste and fissile material depend on the type of nuclear fuel, the amount of burn-up, the extent of radionuclide separation during reprocessing, and the types of material used to immobilize different radionuclides. This chapter is a discussion of the relation between the different types of fuel cycles and their environmental impact.
Cement stabilization of heavy-metal-containing wastes
Authors: Johnson C. Annette
Published: April 2008

Cement has found wide usage in the stabilization of heavy-metal-containing wastes as cement minerals can substantially reduce heavy metal solubility as a result of precipitation, adsorption to the surfaces and incorporation. The solubility of some heavy metal cations is limited by the precipitation of hydroxides, while that of some oxyanions is limited by the formation of Ca salts. Only ions that are sufficiently soluble in basic media will be incorporated in or sorbed to hydrated cement minerals to a significant degree. Heavy metal cations may sorb quite strongly to calcium silicate hydrate (C-S-H). The cations diffuse into the C-S-H particles where they are probably sorbed to the silicate chains. Pure phases of oxyanion-substituted ettringite (3CaO·Al
2
O
3
·3(CaSO
4
)·32H
2
O, an AFt phase) and monosulphate (3CaO·Al
2
O
3
·CaSO
4
·12H
2
O, an AFm phase) phases and solid solutions with SO
4
2
− and OH
−
have been synthesized. Some thermodynamic data are available for the pure phases. For most elements an approximate range of solubility has recently become known. However, it is not possible to predict solubility from the available data.
Interpretation of charging phenomena based on reservoir fluid (PVT) data
Authors: Thompson Keith F. M.
Published: April 2008

Molar concentration profiles of reservoir fluids reveal accumulation history and alteration. Slope Factors (SF) define rates of exponential decrease in concentration of light
n
-alkanes (C
3
-
n
C
5
) and liquid pseudo-components (P
10+
) with increasing carbon number. Most petroleum fluids are substantially characterized by SF(C
3
-
n
C
5
) and SF(P
10+
), the former invariably being the greater. Specific paired values of SF(C
3
-
n
C
5
) and SF(P
10+
) are process-diagnostic. In oils, maturation, gas injection, evaporative fractionation and migration depletion involving loss of gas, are recognizable. SF data are interpreted in the light of PVT analyses representing oils (principally from western Canada) and gas-condensates (from numerous basins), also asphaltene pyrolysis experiments and equation of state calculations. Covariant increase of SF(C
3
-
n
C
5
) and SF(P
10+
) during maturation is demonstrated, but correlation is frequently destroyed by modification of the light ends by the admixture of allochthonous gas, increasing only SF(C
3
-
n
C
5
). Secondary gas-enrichment is a requisite process for the generation of gas-condensates by evaporative fractionation. Compositional criteria for the recognition of enrichment are provided for the first time, particularly attainment of a value of SF(C
3
-
n
C
5
) exceeding 1.69 (a tentative limit). Available data indicate that the process has occurred in a large proportion of oil accumulations, ranging from 23% of 30 reservoirs in the Jurassic Smackover Formation in Alabama, to 78% of 36 in the northern North Sea.