bluuebunny/crossref_metadata_2025 huggingface dataset:
Improvements in clathrate modelling II: the H
2
O-CO
2
-CH
4
-N
2
-C
2
H
6
fluid system
Authors: Bakker R. J.
Published: September 2007

Clathrate stability conditions have been modelled for the H
2
O-CO
2
-CH
4
-N
2
-C
2
H
6
fluid system based on all available experimental data. Optimum Kihara parameters are estimated for pure CO
2
, CH
4
, N
2
and C
2
H
6
gas hydrates from using the most accurate calculation of other parameters involved in clathrate modelling, like fugacities, gas solubilities in H
2
O and thermodynamic constants. For mixed gas hydrates of CO
2
-CH
4
, CH
4
-N
2
, and CH
4
-C
2
H
6
excess Gibbs free energy functions are introduced to obtain a good fit to experimental data. The excess Gibbs free energy is described according a modified Margules equation, which depends on mole fraction and temperature.
Synthesis of CO
2
hydrate in various CH
3
CO
2
Na/CH
3
CO
2
H pH buffer solutions
Authors: Lu H. , Matsumoto R.
Published: September 2007

CO
2
hydrates were synthesized in CH
3
CO
2
Na/CH
3
CO
2
H buffer solutions with various pH values and different concentrations to investigate whether the change of pH value can influence CO
2
hydrate formation. The results imply that the change in pH value has a minimum influence on the equilibrium condition of CO
2
hydrate. The equilibrium condition of CO
2
hydrate in the various pH buffer solutions is seemingly controlled by the total concentration of the acetic acid and acetate anion, while Na
+
cation plays a minimum role.
Detection of gas hydrates using downhole logs
Authors: Goldberg D. , Saito S.
Published: September 2007

Downhole logs have proven to be critical in quantifying natural gas hydrates found in marine sediments and the seismic signature associated with free gas below. In recent drilling on the Blake Ridge, the Ocean Drilling Program recorded
in situ
velocity and resistivity logs that reveal an increasing amount of hydrate with depth in the pressure-temperature stability window. The associated increase in shear rigidity (decrease in
V
p
/
V
s
ratio) and decrease in acoustic amplitude over this interval is attributed to the cementation of sediment grains by hydrate, which may also explain the prevalent seismic blanking across the Blake Ridge. In future drilling campaigns, the use of ‘logging-while-drilling’ (LWD) sensors placed just above the drill bit will improve the
in situ
estimation of porosity, lateral variability and hydrocarbon reservoir potential of natural gas hydrates.
Tomographic seismic studies of the methane hydrate stability zone in the Cascadia Margin
Authors: Hobro J. W. , Minshull T. A. , Singh S. C.
Published: September 2007

A seismic study in the Cascadia Margin in June 1993 focused upon the bottom simulating reflector (BSR) around Hole 889B of the Ocean Drilling Program. Extensive wide-angle and normal-incidence data were collected during two deployments of five ocean bottom hydrophones (OBHs). We have applied a new two-dimensional travel-time inversion method to data from one line within the survey. Data from four OBHs and normal-incidence arrivals are inverted simultaneously, and a distribution of P-wave velocities above the BSR is obtained. These velocities are found to be slightly higher than those given by vertical seismic profile (VSP) and sonic log data from Hole 889B, with velocities of 1.83–1.95 km s
−1
occurring immediately above the BSR. Estimates of hydrate concentration derived using two different methods range from 2 to 24% of the pore space. The velocity model provides some support for the existence of a correlation between BSR strength and hydrate concentration above the BSR in this region.
Marine gas hydrate inventory: preliminary results of ODP Leg 164 and implications for gas venting and slumping associated with the Blake Ridge gas hydrate field
Authors: Paull C. K. , Borowski W. S. , Rodriguez N. M.
Published: September 2007

Deep ODP holes on the Blake Ridge (sites 994, 995 and 997; Leg 164) show that sediments within the interval ∼200–450 metres below sea floor (mbsf) contain 1–4% gas hydrate based on interstitial geochemistry, pressure core samples, well logs and borehole seismic data. In addition, a considerable methane gas reservoir also exists below the gas hydrate stability zone in the form of free and dissolved methane. Addition of methane from these deep reservoirs to overlying ocean water (and ultimately to the atmosphere) could have profound geological, geochemical and climatic effects. Pervasive flux of methane to the sea floor via diffusion is unlikely because methane is almost completely consumed by reaction with sulphate at the sulphate-methane interface. Further, sulphate and
87
Sr/
86
Sr profiles suggest that upward advection of potential methane-containing fluids is also unlikely. However, point sources for methane advection to the sea floor do occur. Active methane transport along faults occurs at Site 996, and the methane
13
C isotopic signature indicates derivation from the gas hydrate-bearing and free gas zones below.
14
C data from sediments indicate that the frequency of sediment slumping on the Blake Ridge is higher during the sea-level lowstand associated with the last ice age. Whereas there is no direct evidence that methane exchange is associated with slump events, nor that gas hydrates are necessarily related to the increased slumping frequency, the association between slumps and faults suggest that the amounts of gas escape should be greater during sea-level lowstands.
Geochemistry of gas hydrates and associated fluids in the sediments of a passive continental margin. Preliminary results of the ODP Leg 164 on the Blake Outer Ridge
Authors: Thiéry R. , Bakker R. , Monnin C.
Published: September 2007

Marine sediments containing gas hydrates have been drilled up to a depth of 750 m below the sea floor (mbsf) at the Blake Outer Ridge during the ODP Leg 164. Gas hydrates are present between 190 and 450 mbsf. Shipboard analyses of gases and interstitial waters are interpreted with the help of thermodynamic models for gas hydrates and aqueous solutions. Two aspects of the influence of gas hydrates on the chemistry of associated fluids are investigated here. The first one is related to the methane/ethane ratio, which exhibits a sudden change of trend at the base of the gas hydrate zone. This phenomenon could be due to gas hydrates, which act as a concentration barrier for ethane. The second aspect concerns the presence of interstitial waters less saline than sea water above and inside the gas hydrate zone. This could result from the upward expulsion of saline waters during the compaction of sediments in the gas hydrate zone.
Extensive deep fluid flux through the sea floor on the Crimean continental margin (Black Sea)
Authors: Ivanov M. K. , Limonov A. F. , Woodside J. M.
Published: September 2007

The ANAXIPROBE/TTR-6 Cruise of the Russian R/V
Gelendzhik
in the summer of 1996 resulted in the discovery of a new area of extensive deep fluid flux through the sea floor on the lower Crimean continental margin, within the Sorokin Trough in the Black Sea. The study area is noted for the widespread development of acoustic anomalies in bottom and sub-bottom sediments indicating the presence of gas. Bottom sampling confirmed a high content of gas in the sediments, the presence of gas hydrates and other features normally associated with gas escape. These features include authigenic carbonates with a light carbon isotope composition and bacterial mats. The geochemical data indicate that the gas has in part a thermogenic origin.
Origin of gas hydrate accumulations on the continental slope of the Crimea from geophysical studies
Authors: Bouriak S. V. , Akhmetjanov A. M.
Published: September 2007

The Sorokin Trough on the south-eastern Crimean margin (northern part of the Black Sea) is known for mud diapirism. Gas hydrates in the sea-bed sediments have previously been recovered from this area in 1988. During the TTR-6 cruise of the R/V
Gelendzhik
in 1996 gas hydrates were observed in five cores containing mud breccia. A comprehensive geophysical survey was carried out, which allowed more insight to be gained into the local distribution of gas hydrates and the linkage of hydrate accumulations to fluid vents. It is therefore suggested that gas hydrates in the study area have most probably been formed from allochthonous gas. Preliminary results from a lithological study of the gas hydrate bearing cores suggested a complex mechanism for the mud volcanoes from which the gas hydrates were sampled, and a complicated history of the gas which was a source for the hydrates.
Detection of gas-charged sediments and gas hydrate horizons along the western continental margin of India
Authors: Veerayya M. , Karisiddaiah S. M. , Vora K. H. , Wagle B. G. , Almeida F.
Published: September 2007

High-resolution seismic reflection and sub-bottom profiling on the continental margin off western India has revealed the presence of characteristic acoustic maskings in the form of wipe-outs, reflector terminations and seep-associated features in the inner shelf. These maskings suggest the presence of gas-charged sediments. Further seaward on the outer shelf-middle slope, pockmarks and prominent plumes in the overlying water column indicate a significant seepage of gas from the slope sediments, and it is the seepage which may demonstrate the existence of source rocks. Seismic profiles also revealed the presence of bottom simulating reflectors (BSRs) in the mid-lower slope-rise regions, presumably suggesting the presence of gas hydrates. The BSRs occur at roughly 300–600 ms (TWTT) beneath the sea floor at water depths between 525 and 2200 m; they occasionally show discontinuities. Distinct blanking zones as well as acoustic voids have also been observed above the BSR. In contrast, chaotic and/or scattered hyperbolic reflectors occur in places below the BSR, which may suggest the presence of gas-charged sediments. Folds, diapiric features and faults present in the slope-rise areas may probably serve as traps and conduits for upward migration of fluids and methane gas from the deep.
Reflection characteristics, depth and geographical distribution of bottom simulating reflectors within the accretionary wedge of Sulawesi
Authors: Neben S. , Hinz K. , Beiersdorf H.
Published: September 2007

Several reflection seismic profiles across the subduction zone north of Sulawesi show strong bottom simulating reflectors (BSRs) below the lower and upper slopes of the accretionary wedge. The geographical distribution, depth and the reflection characteristics of the BSRs have been described in detail. Along one reflection seismic profile the depth of BSR was correlated with heat flow data. These correlations indicate that at locations, where the heat flow is high and the BSR interrupted, active venting of methane may occur at the sea floor. The occurrence of BSRs is limited to the central part of the North Sulawesi subduction zone (between 121°30′E and 123°30′E). In the westernmost part of the surveyed area only short BSR segments are found, which may be a result of slope instability and slumping of sediments. On the easternmost profile, no bottom simulating reflectors are found at all.
The geothermal field of the North Sulawesi accretionary wedge and a model on BSR migration in unstable depositional environments
Authors: Delisle G. , Beiersdorf H. , Neben S. , Steinmann D.
Published: September 2007

The distribution of heat flow in the North Sulawesi accretionary wedge was derived from the depths of a bottom simulating reflector (BSR) and nine
in situ
heat flow measurements. The values obtained by both types of measurements agree reasonably well and suggest high heat flow of the order of 70–100 mW m
−2
near the deformation front and a systematic decrease to 30 mW m
−2
landwards. In addition, we have tested on the basis of one numerical model the likelihood of the BSR being in a position of complete thermal equilibrium with the surrounding rocks. The model describes the rate by which a BSR layer re-equilibrates after a thermal disturbance at the sea floor (sediment slumping). The result suggests that the BSR does not regain complete thermal equilibrium after slumping in the course of several 10
5
years.
Cometary capture and the nature of the impactors
Authors: Bailey M. E. , Emel’yanenko V. V.
Published: September 2007

The inclination-averaged capture probability from nearly parabolic orbits to Halley-type orbits with periods
P
< 200 years and
q
< 1.5 AU is 0.0128 for an isotropic long-period source flux with perihelion distances
q
< 4 AU. The observed near-parabolic flux brighter than visual absolute magnitude
H
10
= 7 is approximately 0.2 comets AU
−1
a
−1
, and the dynamical lifetime of the captured Halley-type comets is on the order of 0.3 Ma. The predicted steady-state number of such comets is thus about 3000, many times more than the number of observed Halley-type comets. Provided that long-period comets do not totally disintegrate during the capture process (e.g. into streams of small bodies such as cometary meteoroids and dust), this indicates that there should be a large population of undiscovered Halley-type ‘asteroids’ in the inner Solar System. The predicted number of dark Halley-type objects is sufficient to produce a terrestrial cratering rate comparable with that from observed near-Earth asteroids, and hence could explain the reported Galactic signal seen in the geological and biological records. The assessment of the terrestrial impact hazard should consider the possibility that a significant number of dark Halley-type objects may exist.
The mass distribution of crater-producing bodies
Authors: Hughes David W.
Published: September 2007

The physical phenomena governing planetary cratering can be represented by three equations. The first, the cratering rate equation, originates from the observation of areas of the Earth’s land-mass that have been exposed to an extraterrestrial flux for a known time, and the detection, counting and measurement of the resultant craters. The second, the energy-diameter equation, is much more uncertain. It relates the kinetic energy of an impacting body to the diameter of the crater that it produces. The third, the mass distribution equation, is also somewhat uncertain. This describes the way in which the flux of incident bodies varies as a function of their masses. This paper investigates the interrelationship between these three equations and comments on the comet/asteroid ratio among the extraterrestrial bodies responsible for producing the 19 <
D
< 45 km craters on Earth.
Calculating flux from meteorite decay rates: a discussion of problems encountered in deciphering a 10
5
–10
6
year integrated meteorite flux at Allan Hills and a new approach to pairing
Authors: Bland P. A. , Conway A. , Smith T. B. , Berry F. J. , Swabey S. E. J. , Pillinger C. T.
Published: September 2007

Meteorite accumulation sites offer the prospect of observing changes in flux over time; however, two main problems must be overcome: calculating a decay constant for samples in an area, and providing accurate pairing data, such that the number of true meteorites (not fragments) can be ascertained. We have used a comparison of meteorite terrestrial age and weathering data to constrain decay constants for hot desert meteorite populations. Meteorites resident in these sites typically have terrestrial ages <50 ka. Our estimates of the flux of meteorites to the Earth are within a factor of 2–3 of independent estimates made by the Meteorite Observation and Recovery Project network, and suggest no change in the flux over the last 50 ka. A similar approach applied to meteorites from Allan Hills, Antarctica, finds much lower levels of weathering, although terrestrial ages for these samples are much longer. We also observe a correlation between terrestrial age and degree of weathering in the Allan Hills meteorites, suggesting a weathering rate 2–3 orders of magnitude slower than values typical of hot desert sites. Given that blue ice regions are subject to some horizontal flow, we propose a model in which the observed oxidation-terrestrial age distribution is largely a result of ice movement, rather than weathering. Comparing oxidation and terrestrial age data in the Antarctic and hot desert accumulations, we estimate a lifetime for the Allan Hills population of 200–300 ka. Given the distance to the nearest ice divide (200 km), this suggests an average horizontal flow rate of 1 m a
−1
. This approach may allow an estimate of the catchment area for these samples to be made. In addition, we suggest an alternative method for pairing samples which makes use of automated image processing and data analysis of reflected light photomicrographs to acquire a ‘textural fingerprint’ of a sample, and a genetic algorithm to compare the numerous data variables.
14
C terrestrial ages of meteorites from Victoria Land, Antarctica, and the infall rates of meteorites
Authors: Jull A. J. T. , Cloudt S. , Cielaszyk E.
Published: September 2007

The results of
14
C measurements of 95 meteorites from the Allan Hills region in Antarctica are reported, and terrestrial residence ages calculated. This includes meteorites from the different icefields at Allan Hills and the adjacent Elephant Moraine meteorite stranding area. We determined that terrestrial ages of these Antarctic meteorites can range from recent falls to >40 ka, which is the practical limit for these
14
C measurements. The terrestrial age determinations on meteorites from these sites can vary dramatically; the differences between the ages observed from these sites and some of the factors influencing them are discussed. Weathering products found on these meteorites show
14
C ages younger than the terrestrial age of the meteorites studied. Calculation of infall rates based on meteorites recovered and their age distributions suggests a minimum infall rate of 40–60 meteorites (>10 g) per 10
6
km
2
per year, in reasonable agreement with the infall rates estimated by Halliday’s group based on meteoroid fluxes.
The flux of meteorites to Antarctica
Authors: Zolensky Michael
Published: September 2007

It is premature to report firm conclusions regarding the past meteorite flux rate from the Antarctic record, as variables related to ice flow, meteorite catchment area, weathering and removal rate are not well constrained. The relative population of meteorite types appears to be broadly compatible with the modern fall population, although there are minor differences. In particular, there are populations of small unusual irons, carbonaceous chondrites and lunar samples not found among the modern falls. In addition, slight compositional differences between modern and old (Antarctic) H chondrites may signal a time-dependent change in the flux to Earth of more common meteorites.
Identification of meteoritic components in impactites
Authors: Koeberl Christian
Published: September 2007

The verification of an extraterrestrial component in impact-derived melt rocks or breccias can be of diagnostic value to provide confirming evidence for an impact origin of a geological structure. Geochemical methods are used to determine the presence of the minor traces of such a component. This is because even under ideal conditions, meteoritic fragments are preserved only at very young and small craters, but are destroyed in larger and older structures as a result of erosion and/or vaporization. The absence of meteorite fragments can, therefore, not be used as evidence against an impact origin of a crater structure. The determination of such an extraterrestrial component can be done by studying the concentrations and interlement ratios of siderophile elements, especially the platinum group elements, which are several orders of magnitude more abundant in meteorites than in terrestrial upper-crustal rocks. More recently, the Re-Os isotopic system has been used for identifying the presence of a meteoritic component in a number of impact melt rocks and breccias. This method avoids the ambiguities that may affect the usage of elemental abundances and ratios; for example, if the target rocks have high abundances of siderophile elements, or if the siderophile element concentrations in the impactites are very low. The presence of a meteoritic component has been established for about 41 impact structures (out of about 150 known on Earth), which reflects also the detail in which these structures were studied. In some of the smaller of these craters, fragments of the meteorite (the ‘projectile’) are preserved, but in most others, only a minor extraterrestrial component (mostly <1 wt %) is mixed in with impact melt rocks or breccias. The identification of the projectile type (i.e. meteorite type) is not straightforward, as vapour fractionation during the impact, as well as post-impact fractionation in the melt or hydrothermal mobilization, may lead to changes in the interlement ratios.
Preliminary results from a passive seismic array over the Chicxulub impact structure in Mexico
Authors: Maguire P. K. H. , Mackenzie G. D. , Denton P. , Trejo A. , Kind R. ,   Members
Published: September 2007

A passive, 20-element, short-period (1 Hz) and broadband seismic array was deployed over the Chicxulub impact structure for
c.
100 days in early 1996. The principal objective was to study the shear-wave anisotropy associated with the structure; in particular, to determine the presence (or absence) of radial symmetry which will allow comment on the time variance of that anisotropy. A total of 15 teleseismic, 75 regional, and 100 local events were recorded. Preliminary results from studies of the surface-wave dispersion of the local events, and a receiver function analysis of a single teleseismic event are reported here. Thirty local events have been located, a number of which originated from quarries within the array. Analysis of seismo grams from three of these events demonstrates a bimodal distribution; those whose ray-paths cross the outer part of the impact structure show a strong inverse dispersion, whereas those with ray-paths crossing the centre do not. The pattern may be produced by the sedimentary depositional environment, with deeper water sedimentation in the outer part of the post-impact crater basin and shallower water sedimentation over the upraised peak-ring block at the centre. Receiver functions derived for an event originating in Peru are dominated by an efficient mode conversion, simply modelled as a P-S multiple from the base Tertiary boundary. This shows a strong correlation with distance from the centre of the impact structure and implies it has an S-wave radial symmetry. The multiple also has a variable delay probably related to the depth of the conversion boundary. Unfortunately, the Moho conversion occurs at almost exactly the same time as this surface layer sediment multiple, restricting any modelling of Moho topography and its influence on the receiver functions.
Charles Lyell and the Geological Society
Authors: Thackray John C.
Published: September 2007

Charles Lyell was a loyal and committed Fellow of the Geological Society from 1819 until 1875, serving as Secretary, Foreign Secretary and President. He was principally a theorist, his uniformitarian outlook strongly influenced by the work of James Hutton. The Society on the other hand was devoted to the collection and dissemination of facts; on the whole, theorizing was unwelcome. In line with this tradition the papers Lyell read to the Society are largely factual, and do not add a great deal to the ideas put forward in the
Principles of Geology
. However, his theories were not ignored by the Society, being noticed in the annual presidential address and, more importantly, in the unscripted and largely spontaneous discussions that took place after many of the papers read at the Society’s evening meetings.
Charles Lyell in New York State
Authors: Friedman Gerald M.
Published: September 2007

In 1842 Amos Eaton (1776–1842), founder of the Rensselaer School in Troy, New York (later Rensselaer Polytechnic Institute), had become the most influential American geologist. The period between 1818 and 1836 is known as the ‘Eatonian era’. In 1841, Lyell visited Eaton at Rensselaer. He states ‘at Troy I visited Professor Eaton … The mind of this pioneer in American geology was still in full activity, and his zeal unabated; but a few months after my visit he died.’ In company with Eaton’s former student James Hall (1811–1898), Lyell journeyed to Niagara Falls. After describing sediments and geological features near Niagara Falls, Lyell returned to his uniformitarian concepts and used the Niagara Falls as a point of departure to reiterate his message of the enormity of geological time but continuity of geological processes. Lyell was most impressed with the Helderberg Mountains. The ‘Helderberg war’, however, distracted him. According to a history, ‘Sir Charles Lyell, … geologizing on the Helderbergs that day, found the farmers “in a ferment.” Sir Charles took time from his study of fossils embedded in the rocks of the Helderbergs to criticize (New York) Governor Seward.’ In Troy Lyell reported on landslides in which people were killed. Much of Lyell’s account relates to non-geological descriptions.
Charles Lyell and the evidences of the antiquity of man
Authors: Cohen Claudine
Published: September 2007

This paper examines the importance of Lyell’s book,
The Geological Evidences of the Antiquity of Man
(1863), in Lyell’s work and career, as well as its contribution to the founding of two scientific disciplines, Prehistoric Archaeology and Palaeoanthropology. It first focuses on Lyell’s two ‘conversions’ (to the idea of the antiquity of man and to Darwin’s theory of transmutation of species) both of which he acknowledged in his book; it turns then to a study of the nature of the ‘evidences’ that Lyell advances. These evidences were of several kinds — archaeological, palaeontological, anthropological, and, most importantly, geological; at the time, the best way to prove the existence of fossil Man was to demonstrate geologically the contemporaneity of man-made objects and extinct animals.

This paper insists in particular on Lyell’s relationship to French science of the time, and examines the circumstances and modalities of a collaboration which was essential to the international acceptance of the antiquity of man. The fact that Lyell was a major scientific authority, whose expertise could validate the authenticity of evidence, allowed him to play a central role in the founding of a new field of knowledge.
Lyell’s
Principles of Geology
: foundations of sedimentology
Authors: Leeder M. R.
Published: September 2007

This chapter examines the extensive arguments Lyell brought to bear on the interpretation of sedimentary rocks through the operation of ‘present causes’ in the first Edition of
Principles of Geology
(1830–1833). A case is made
inter alia
for Lyell, rather than Sorby, being the true originator of sedimentology and basin analysis, amongst much else of course. Lyell had a special interest in Earth surface processes, and the effects of tectonics and climate on them, because he saw that the evidence is firmly written in the sedimentary products of observable events. His own explanations for the sedimentary and geomorphic processes of erosion and deposition were acutely sensible: he analysed (in today’s parlance) river avulsions, controls on delta morphology, oceanic brine pools, cross stratification, confluence bars, boundary layers, hydraulic geometry, debris flows, sediment budgets, alluvial basin architecture, and clinoforms. Much of Sorby’s work in some of these areas must have been inspired by his reading of the
Principles
. Lyell was occasionally too much guided by theory, as in the famous sophistry of his 1830 analysis (in the first edition) of the sedimentary and geomorphological evidence for Holocene Fenno-Scandinavian uplift. His willingness in subsequent editions of
Principles
to abandon such firmly held views in the light of empirical and personally collected field evidence to the contrary presages his momentous decision to throw his weight behind Darwin’s natural selection theories some 30 years later. Lyell was not so rigidly an anti-catastrophist and inductionist as is commonly made out. His writings make very clear his ability to state bold theories. For example, his discussions of climatic change and his concept of the ‘great year’ were outstandingly incisive, holistic and original. They include the role of land-sea interactions, ocean currents and precessional orbital cycles. He even considered the probability that continents and oceans changed position, albeit by vertical movements. The motive for all this came from observations he and others had made on the distribution of Cenozoic molluscs and the need for some general global cooling to explain these. He included in his actualism all manner of extreme (but not ‘catastrophic’) events, for example earthquakes and volcanic eruptions. He was also willing to consider (but then rejected) the possibility of catastrophes, most obviously in his discussion in the seventh edition of
Principles
(1846) of the possible ‘lake-burst’ of Lake Superior into the headwaters of the Mississippi. One feels he would have welcomed probability theory and the development of magnitude/frequency analysis, and that he would have laughed at any modern description of himself as the ‘father of uniformitarianism’.
The Cenozoic Era: Lyellian (chrono)stratigraphy and nomenclatural reform at the millennium
Authors: Berggren William A.
Published: September 2007

The historical and intellectual framework and contemporary influences and sources leading to, and associated with, Charles Lyell’s studies of Tertiary stratigraphy are reviewed. The nomenclatural hierarchy into which some of Lyell’s stratigraphic terms have been subsequently grouped is then analysed.

Lyell’s terms ‘Eocene’, ‘Miocene’, ‘Pliocene’ (1833) and ‘Pleistocene’ (1839) were essentially biostratigraphic/biochronologic in nature. Together with the subsequently defined ‘Oligocene’ (1854) and ‘Paleocene’ (1874), they have gradually aquired a chronostratigraphic connotation over the past 100 years. The term ‘Neogene’ (Hörnes 1853, 1856, 1864), when transferred from its original biostratigraphic/biochronologic (Lyellian) to a chronostratigraphic connotation, includes the stratigraphic record of the Miocene, Pliocene, Pleistocene and Recent (subsequently termed Holocene) epochs (equivalent to the ‘periods’ of Lyell). Thus a Neogene/Quaternary boundary is wholly inappropriate as a standard chronostratigraphic boundary. The ‘Palaeogene’ (Naumann 1866) now comfortably accomodates the stratigraphic record of the Paleocene, Eocene and Oligocene epochs

The terms ‘Palaeogene’ and ‘Neogene’ should be used as period/system subdivisions of the Cenozoic Era. ‘Tertiary’ and ‘Quaternary’ should be abandoned, relicts of a now outmoded, and inappropriate, pre-Lyellian stratigraphy. Retention of the term ‘Quaternary’ for geopolitical purposes (institutional affiliation or scientific/professional identification), as opposed to its retention as part of the standard stratigraphic hagiography, is recommended and would reduce, if not eventually eliminate, continuing but unnecessary, and unscientific, rancorous debate over standard Cenozoic chronostratigraphic terminology.
Lyell’s views on organic progression, evolution and extinction
Authors: Hallam A.
Published: September 2007

Following Cuvier, Lyell was readily prepared to accept a succession of species extinctions in the past but he rejected Cuvier’s ideas on episodes of catastrophic mass extinction. In the
Principles of Geology
he argued against organic progression in the fossil record, believing instead that organic traces had been substantially removed from older rocks by metamorphism and other factors, and that groups such as land mammals should not be expected, except very rarely, in the marine strata of the Palaeozoic and Mesozoic. He did, however, accept that the human species was of modern origin, but emphasized that the most significant feature of humanity emergence was in the moral rather than the physical sphere. Lamarck’s theory of evolution involving species transmutation was vehemently rejected; like Cuvier, Lyell believed in the stability of species. As evidence continued to accumulate in favour of some kind of organic progression in the stratigraphic record, Lyell’s resistance eventually crumbled, but he continued to believe in the extreme imperfection of the fossil record. Like Darwin, he could find no direct evidence from it for evolution. In the 1860s he eventually came to accept some form of evolution, while adhering to the rest of his uniformitarinism, but continued to reject Darwin’s theory of natural selection.
The age of the Earth and the invention of geological time
Authors: Burchfield Joe D.
Published: September 2007

During Charles Lyell’s lifetime the concept of geological time was gradually rendered meaningful through the construction of a heuristic geological timescale, the development of quantitative methods to calculate the duration of that scale, and the acceptance of a quantitatively determinable limit to the age of the Earth. This paper describes a few episodes in the process of ‘inventing’ the concept of geological time, episodes chosen primarily for their relevance to the work of Lyell.
From William Smith to William Whitaker: the development of British hydrogeology in the nineteenth century
Authors: Mather John
Published: September 2007

Some of the earliest applications of the principles of geology to the solution of hydrologic problems were made by William Smith, who used his knowledge of strata succession to locate groundwater resources to feed the summit levels of canals and supply individual houses and towns. The industrial revolution led to a huge demand for water resources to supply new towns and cities. Nottingham, Liverpool, Sunderland and parts of London all relied on groundwater. By the middle of the nineteenth century James Clutterbuck had already recognized that groundwater was a finite resource and that if abstraction was more rapid than replenishment by rain, water levels would decline and quality would be affected by saline intrusion. In 1851 Prestwich produced the first British geological map that included groundwater information. Before 1870 the Geological Survey had shown little concern for groundwater, perhaps because its Director, Murchison, had little interest in the economic applications of geology. After his retirement in 1871 there was an explosion of activity. Lucas introduced the term ‘hydrogeology’ in 1874 and produced the first real hydrogeological map in 1877 after leaving the Survey to work as a consultant water engineer. De Rance was for 20 years the secretary of a British Association Committee set up in 1874 to inquire into the underground circulation of water and in 1882 produced a 600 page volume on the water supply of England and Wales. William Whitaker, sometimes described as the ‘father of English hydrogeology’, was a collecter of well records and his work led to the inclusion of page after page of well records in survey publications in the southeast of England and in 1899 to the first water supply memoir —
The Water Supply of Sussex from Underground Sources
. From Smith to Whitaker, knowledge of groundwater grew throughout the nineteenth century, providing the basis for the sophisticated models of today.
The legacy of Charles Lyell: advances in our knowledge of coal and coal-bearing strata
Authors: Scott Andrew C.
Published: September 2007

On his travels in both Britain and North America Sir Charles Lyell paid particular attention to coalfields and their fossils. Understanding the formation of coal and associated rocks was the subject of several publications. In this contribution three aspects of this work are highlighted, all of which are the subject of ongoing modern research. Lyell was interested in modern analogues for the Carboniferous coal swamps and was amongst the first to suggest analogies with the mires of the eastern United States, such as the Dismal Swamps. A brief review of recent research on new modern analogues from Southeast Asia is presented. Lyell observed ‘mineral charcoal’ in some of the coals and noted its anatomical structure. Considerable advances in our understanding of the role of fires in terrestrial ecosystems and their potential as an agent of fossil preservation are addressed. One of Lyell’s most important palaeontological finds was of remains of the earliest reptiles (these proved to be amphibians but Sir William Dawson found reptiles subsequently) preserved in the Upper Carboniferous tree trunks at Joggins, Nova Scotia, Canada. Whilst this occurrence of reptiles is no longer the oldest, the reasons for the remarkable tetrapod occurrences in upright sandstone-filled lycophyte trees at Joggins are currently being investigated and recent progress is presented.
Mount Etna: monitoring in the past, present and future
Authors: Rymer Hazel , Ferrucci Fabrizio , Locke Corinne A.
Published: September 2007

Mount Etna is important to the economy of eastern Sicily, with agriculture and summer and winter tourism providing employment for thousands of people. Although there are no permanent homes within 10 km of the summit, year-round human activities on the upper slopes are proliferating and the risks from even a small eruption are consequently magnified. The earliest form of monitoring at Etna, as for other volcanoes, was direct observation. Modern volcano monitoring at its most effective is a synergy between basic science and hazard assessment. A prerequisite to effective monitoring is an understanding of volcanic structure and history. Sir Charles Lyell was among the first to make systematic observations of Mount Etna and laid the foundation of more modern studies. A huge array of monitoring techniques has been tested on Etna; methods that have proved successful in monitoring and sometimes in predicting eruptions include observations of seismicity, ground deformation and microgravity. These, together with electromagnetic, magnetic, gas geochemistry and various remote sensing techniques have also provided key information on the volcanic plumbing system and the eruption process. Monitoring techniques were formerly based on the most easily measured phenomena; other effects were either not recorded or were treated as noise. Future progress will be enhanced by taking account of these more subtle or complex effects and by the more comprehensive acquisition and real-time analysis of continuous data sets over extended periods. Important monitoring techniques and strategies available both now and in the near future are reviewed here in the context of Etna. The need to develop a reliable scientific platform for routine and inexpensive volcano monitoring throughout the world is highlighted.
Structural modelling of the south Porcupine Basin, offshore Ireland: implications for the timing, magnitude and style of crustal extension
Authors: Baxter K. , Buddin T. , Corcoran D. V. , Smith S.
Published: September 2007

Regional structural synthesis together with 2D forward and reverse flexural isostatic basin modelling techniques have been used to investigate the extensional and subsidence history of the southern part of the Porcupine Basin. Two structural interpretations of seismic line GSP97-19 have been considered: (1) a Mid-Late Jurassic rift basin based upon seismic interpretation of well-defined tilted fault blocks, with subsidence modelling of the thick overlying sediment section predicting high lithosphere stretching factors of up to β = 6; (2) a Mid-Jurassic-Early Cretaceous rift responsible for a thick Barremian-Aptian synrift sequence within the basin centre resulting in reduced maximum lithospheric stretching factors of β = 2.3. The variance in published estimates of crustal thickness beneath the basin cannot distinguish between these scenarios. A comparison between stretching factors and the amount of observable upper-crustal faulting suggests that depth-dependent lithospheric stretching may be a feature of the basin, as in other sedimentary basins along the Atlantic margin, and is directly associated with the onset of Cretaceous plate break-up in the Atlantic.
Direct assessment of groundwater vulnerability from borehole observations
Authors: Worrall F.
Published: September 2007

A method is developed for measuring the vulnerability of the catchment of a borehole to groundwater pollution based on observation of contaminant in the borehole and the region. The method uses Bayesian statistics to compare the proportion of pesticide detections in the region with that found in the borehole as a measure of groundwater vulnerability of that borehole catchment. Using data from California the method is demonstrated for multi-annual borehole observations of a set of compounds. The method has distinct advantages over present vulnerability assessment methods. The method calculates a continuous measure of borehole vulnerability rather than an index or score. This measure of borehole vulnerability is based solely on observations and not on expert opinion or the application of models. The use of Bayesian methods means that results can be used within a probabilistic risk assessment and can be updated as more information becomes available or as new regional data are considered. The assumptions and disadvantages of the methodology are discussed, but such methods could form the basis of testing the importance of climatic, soil and geological factors in controlling pollutant movement leading to improved management and protection of groundwater resources.
Assessments of the sensitivity to climate change of flow and natural water quality in four major carbonate aquifers of Europe
Authors: Younger P. L. , Teutsch G. , Custodio E. , Elliot T. , Manzano M. , Sauter M.
Published: September 2007

A numerical modelling approach has been developed to predict the vulnerability of aquifers to future climate change. This approach encompasses changes in recharge regime, dynamics of flow and storage patterns within aquifers, and natural hydrochemical changes. An application of the approach has been made to four hypothetical spring catchments representative of major carbonate aquifers in three European climatic zones. Since prolific carbonate aquifers typically combine a high transmissivity with a low specific yield, they can be expected to be more sensitive than clastic aquifers to changes in recharge patterns. Simulations of the study systems to the middle of the 21
st
century predict different outcomes in the three different climate zones: (1) in the northern maritime zone (UK) recharge (and therefore discharge) is predicted to increase by as much as 21 0n response to anticipated increases in precipitation; (2) in the continental zone (Germany) recharge in winter is predicted to remain approximately the same as at present, but summer recharge will decline dramatically (by as much as 32%), so that a net decrease in aquifer discharge is predicted; and (3) in the Mediterranean zone (Spain) recharge is predicted to decrease by as much as 160f the present-day values. For all three systems, increases in water hardness in response to rising CO
2
are predicted, but are expected to be negligible in water resources terms.
Simulation of the impacts of climate change on groundwater resources in eastern England
Authors: Yusoff I. , Hiscock K. M. , Conway D.
Published: September 2007

This study investigated the impacts of climate change on the Chalk aquifer in west Norfolk. A two-layer transient groundwater flow model of the aquifer system was calibrated and validated for the period 1980–1995 and provided the historic flow record for the climate change simulations. Two future scenarios were selected from the Hadley Centre’s climate change experiments using HadCM2: (1) a medium-high (MH) emissions scenario; and (2) a medium-low (ML) emissions scenario of ‘greenhouse’ gases. Two future periods were considered: 2020–2035 and 2050–2065. Future recharge to the aquifer was estimated by adjusting the historic record of monthly precipitation and potential evapotranspiration by factors calculated from comparing control and future HadCM2-generated values. Impacts of climate change were evaluated by incorporating the monthly estimated recharge inputs within the flow model. The most noticeable and consistent result of the climate change impact simulations is the decrease in recharge expected in autumn for all scenarios (decreases ranging from 17 to 35%) as a consequence of the smaller amount of summer precipitation and increased autumn potential evapotranspiration. For the 2050MH scenario, these conditions lead to a 42 0ncrease in autumn soil moisture deficit and a 26% reduction in recharge. Hence, west Norfolk can expect longer and drier summers that are predicted to have relatively little effect on summer groundwater levels (generally a 1 to 2 0ecrease) but will result in a decrease of up to 14 0n autumn river baseflow volumes.
Mars: a review and synthesis of general environments and geological settings of magma-H
2
O interactions
Authors: Head James W. , Wilson Lionel
Published: September 2007

The advent of a global cryosphere likely occurred very early in the history of Mars, and much of the available water and related volatiles (CO
2
, clathrates, etc.) were sequestered within and below the cryosphere. This means that magmatism (plutonism and volcanism) as a geological process throughout the history of Mars cannot be fully understood without accounting for the interaction of magma and water (and related species) in both solid and liquid form. We review and outline the probable configuration of water and ice deposits in the history of Mars, describe environments and modes of magma-H
2
O interaction, and provide specific examples from the geological record of Mars. Magma and water-ice interactions have been interpreted to have formed: (1) massive pyroclastic deposits; (2) large-scale ground collapse and chaotic terrain; (3) major outflow channels; (4) mega-lahars dwarfing terrestrial examples; (5) sub-ice-sheet eruptions and edifices; (6) pseudocraters; (7) landslides on volcanic edifice flanks; and (8) hydrothermal sites. The global nature of the cryosphere, its longevity, and the diversity of environments means that Mars is an excellent laboratory for the study of magma-H
2
O interactdions and the role of related volatile species.