bluuebunny/crossref_metadata_2025_split huggingface dataset:
Shallow gas and gas hydrates in the Anaximander Mountains region, eastern Mediterranean Sea
Authors: Woodside J. M. , Ivanov M. K. , Limonov A. F. 
Published: September 2007

Abstract
Gas hydrates have been sampled from a mud volcano in the eastern Mediterranean for the first time, during a recent expedition to study the nature and origin of the Anaximander Mountains offshore from southwest Turkey. Seven mud volcanoes were sampled as part of a successful strategy to obtain rocks which had been brought up from the deeper parts of the mountains themselves. The mud volcanoes seem to be associated with cross-cutting strike-slip faults defining individual blocks in this mountain complex, and may permit overpressured fluids from thrusts in this compression zone to be expelled at the surface. There is ample evidence in many parts of the area studied for the widespread presence of gas in the sediments, such as pockmarks, acoustic turbidity and acoustic wipeouts in sub-bottom profiles, gas in sediment samples, and mud volcanoes with carbonate crusts and benthic communities typical of those found elsewhere near gas seeps and fluid vents (e.g. vestimentifera worms, bivalves). It is postulated that the high mobility of some of the sediments is promoted by excess fluids possibly released in part from gas hydrates in the Plio-Pleistocene sediments. A good example of the sediment deformation is shown by a large area of moving sediments.
Possible hydrate mounds within large sea-floor craters in the Barents Sea
Authors: Long D. , Lammers S. , Linke P. 
Published: September 2007

Abstract
Interpretation of several surveys across a ‘crater field’ in the Barents Sea provide further evidence that the craters (large depressions, 300–500 m diameter, 10–30 m deep) are related to gas escape after deglaciation some 15 000 years BP. The disposition of the craters suggests that the flow of gas was controlled by fractures within the Triassic siltstone bedrock. Topographic highs within several craters, comprising angular blocks of rock locally rising above the level of surrounding crater walls, are interpreted as hydrate mounds indicating that gas flow continued after the formation of the craters. This may be the first reported occurrence of hydrate mounds in lithified sediments. Assuming the gas was methane and seabed temperature was similar to that at present then the hydrate mounds were formed at a time when the sea-bed was between 280 and 340 metres below sea level (mbsl)(i.e. 10–80 m lower than at present). Geochemical studies provide evidence that gas hydrates in the sub-bottom adjacent to the crater field are presently decomposing in accordance with seasonal temperature variations.
Gas hydrates along the northeastern Atlantic margin: possible hydrate-bound margin instabilities and possible release of methane
Authors: Mienert J. , Posewang J. , Baumann M. 
Published: September 2007

Abstract
The presence of gas hydrates and free gas in oceanic sediments along the northeastern European Margin is documented in high-frequency near-vertical and wide-angle seismic reflection data. Shallow-water and deep-water gas hydrate instabilities can cause free gas to escape from oceanic sediments. Particularly, methane from shallow-water gas hydrate destabilization may then get transferred from the sediments into the water column, and eventually into the atmosphere. Deep-water gas hydrates are coincident with areas and depths of slope failures in continental margin sediments. Comparisons between seismicity and the potential hydrate distributions suggest a correlation between hydrate instability and margin instabilities along the north-eastern Atlantic Margin.
Evidence for faulting related to dissociation of gas hydrate and release of methane off the southeastern United States
Authors: Dillon W. P. , Danforth W. W. , Hutchinson D. R. , Drury R. M. , Taylor M. H. , Booth J. S. 
Published: September 2007

AbstractAn irregular, faulted, collapse depression about 38 × 18 km in extent is located on the crest of the Blake Ridge offshore from the south-eastern United States. Faults disrupt the sea floor and terminate or sole out about 40–500 m below the sea floor at the base of the gas hydrate stable zone, which is identified from the location of the bottom simulating reflection (BSR). Normal faults are common but reverse faults and folds also are widespread. Folds commonly convert upward into faults. Sediment diapirs and deposits of sediments that were erupted onto the sea floor are also present. Sea-floor depressions at faults may represent locations of liquid/gas vents. The collapse was probably caused by overpressures and by the decoupling of the overlying sediments by gassy muds that existed just beneath the zone of gas hydrate stability.
Natural gas hydrates: searching for the long-term climatic and slope-stability records
Authors: Haq B. U. 
Published: September 2007

Abstract
The recent revival of interest in gas hydrates has grown from the awareness that they may play significant roles in several global and regional processes, including global carbon recycling, rapid climate change through emission of methane from marine sediments into the atmosphere, and as a cause for massive transport of sediments and structural changes on the continental slope. Their estimated large volumes are also considered to be a potential resource for future exploitation. Here the long-term record of gas hydrate behaviour is examined in terms of climatic, oceanographic, stratigraphic and slope-stability changes of the past. Various intriguing hypotheses recently offered to explain the observed record also highlight the numerous unknowns and our relative ignorance about these widespread features of the continental margins. The paper identifies some of these gaps and poses several relevant questions that will need to be answered before we can appreciate their full potential and cause-effect relationship of hydrate dissociation with climate change and slope stability.
What does the ice-core record imply concerning the maximum climatic impact of possible gas hydrate release at Termination 1A?
Authors: Thorpe R. B. , Pyle J. A. , Nisbet E.G. 
Published: September 2007

Abstract

The rapid climate changes at the terminations marking the end of the last glaciation are poorly understood. CH
4
hydrate decomposition has been suggested as a possible trigger of deglaciation. This would imply that there was a large pulse of atmospheric CH
4
contemporaneous with Termination 1A. This implication is tested here in a two-stage process using an adapted version of the Cambridge 2-D model. Firstly, the ice-core record was used to place an upper limit on the magnitude of possible CH
4
release at Termination 1A. Secondly, the climatic impact of this realistic maximum (RM) pulse was estimated and compared with the actual climate change occurring at deglaciation. It was found that the maximum pulse that could readily be squared with the ice-core record was around 4000 Tg. Its climatic impact was modelled for a range of scenarios covering climate sensitivities from 1.5 to 5.2°C, and involving possible changes in atmospheric CO
2
and latitudinal heat transport. The direct radiative effects of this pulse were too small to account for the deglaciation alone, but, for certain combinations of CH
4
, CO
2
, and heat transport changes, coupled with high climate sensitivity, it was possible to simulate changes of the same magnitude as those observed.
Ice-core record of atmospheric methane changes: relevance to climatic changes and possible gas hydrate sources
Authors: Raynaud D. , Chappellaz J. , Blünier T. 
Published: September 2007

Abstract

The Antarctic and Greenland ice contains an almost direct record of past atmospheric CH
4
. The record over the last 200 years reveals a spectacular 150% increase of the CH
4
atmospheric mixing ratio since pre-industrial times. At the scale of a glacial-interglacial cycle the record shows a remarkable correlation with climatic changes, with high (low) CH
4
levels during warm (cold) periods. A striking feature of the glacial-interglacial CH
4
record is the presence of large and abrupt (at the scale of a century or less) changes during the last glaciation and glacial-interglacial transition. The classical interpretation for the origin of CH
4
changes prior to the industrial era involves mainly the wetland source. In the context of gas hydrates the question is to know whether the past ice-core record contains fingerprints of catastrophic hydrate release (CHR). We currently conclude that the available record shows no evidence for CHR but additional ice-core analyses are necessary to reach a more definitive conclusion.
Galactic periodicity and the geological record
Authors: Napier W. M. 
Published: September 2007

Abstract

Precisely dated impact craters, major geological disturbances and mass extinction peaks were used to investigate statistically the hypothesis that global terrestrial phenomena are triggered by the Galactic environment through bombardment episodes. Strong temporal correlations were found between events in these datasets, and in aggregate they were found to have a periodicity of
c.
27 ± 1 Ma corresponding to the half-period of the Sun’s vertical oscillations within the Galactic disc. Global disturbances appear to be forced in quasi-periodic fashion through a combination of impacts and prolonged climatic stress, the latter as a result of stratospheric dusting by debris from very large short-period comets.
Meteorite flux on the Nullarbor Region, Australia
Authors: Bevan A. W. R. , Bland P. A. , Jull A. J. T. 
Published: September 2007

Abstract

The Nullarbor Region of Australia is one of the most prolific sites for meteorite recoveries outside of Antarctica. Reported
14
C terrestrial ages for chondritic meteorites from the Nullarbor indicate an age range from present day to
c.
35 ka. There is good evidence to suggest that meteorites are lying on, or close to the surfaces on which they fell and that, physiographically, the region has remained essentially undisturbed for at least the last 30 ka. The Nullarbor can thus provide important data on the flux of meteorites over the period of accumulation. One significant factor influencing flux calculations based on meteorite accumulation sites is the determination of the number of falls represented in the recovered population. In the case of the Nullarbor, a general lack of transportation processes in the region and careful documentation of the distribution of finds allows confident ‘pairing’ of meteorites. For example, strewn fields of showers that have remained undisturbed for thousands of years are easily recognized and mapped today. Mass distribution statistics confirm that there are few undetected pairs in the population of meteorites so far described from the Nullarbor, and there is no evidence of selection of meteorites of a specific terrestrial age. The Nullarbor is the largest accumulation of meteorites nearest to Antarctica with a terrestrial age range (0–35 ka) that overlaps the Antarctic population (0 to >1 Ma). Analysis of the well-documented population of meteorites from the Nullarbor compared with Antarctica suggests that there are many unrecognized paired meteorites in the Antarctic population and the abundance of small meteorites at that site can be accounted for, at least in part, by the presence of large shower falls of common chondrites. The data suggest that there may also be many unrecognized paired meteorites in collections from the Sahara.
Mapping Chicxulub crater structure with gravity and seismic reflection data
Authors: Hildebrand A. R. , Pilkington M. , Ortiz-Aleman C. , Chavez R. E. , Urrutia-Fucugauchi J. , Connors M. , Graniel-Castro E. , Camara-Zi A. , Halpenny J. F. , Niehaus D. 
Published: September 2007

Abstract

Aside from its significance in establishing the impact-mass extinction paradigm, the Chicxulub crater will probably come to exemplify the structure of large complex craters. Much of Chicxulub’s structure may be ‘mapped’ by tying its gravity expression to seismic-reflection profiles revealing an ∼180 km diameter for the now-buried crater. The distribution of karst topography aids in outlining the peripheral crater structure as also revealed by the horizontal gradient of the gravity anomaly. The fracturing inferred to control groundwater flow is apparently related to subsidence of the crater fill. Modelling the crater’s gravity expression based on a schematic structural model reveals that the crater fill is also responsible for the majority of the negative anomaly. The crater’s melt sheet and central structural uplift are the other significant contributors to its gravity expression. The Chicxulub impact released ∼1.2 × 10
31
ergs based on the observed collapsed disruption cavity of ∼86 km diameter reconstructed to an apparent disruption cavity (
D
ad
) of ∼94 km diameter (equivalent to the excavation cavity) and an apparent transient cavity (
D
at
) of ∼80 km diameter. This impact energy, together with the observed ∼2 × 10
11
g global Ir fluence in the Cretaceous-Tertiary (K-T) fireball layer indicates that the impactor was a comet estimated as massing ∼1.8 × 10
18
g of ∼16.5 km diameter assuming a 0.6 gcm
−3
density. Dust-induced darkness and cold, wind, giant waves, thermal pulses from the impact fireball and re-entering ejecta, acid rain, ozone-layer depletion, cooling from stratospheric aerosols, H
2
O greenhouse, CO
2
greenhouse, poisons and mutagens, and oscillatory climate have been proposed as deleterious environmental effects of the Chicxulub impact with durations ranging from a few minutes to a million years. This succession of effects defines a temperature curve that is characteristic of large impacts. Although some patterns may be recognized in the K-T extinctions, and the survivorship rules changed across the boundary, relating specific environmental effects to species’ extinctions is not yet possible. Geochemical records across the boundary support the occurrence a prompt thermal pulse, acid rain and a ∼5000 year-long greenhouse. The period of extinctions seems to extend into the earliest Tertiary.
Geochemistry of carbon in terrestrial impact processes
Authors: Gilmour Iain 
Published: September 2007

Abstract

Terrestrial impact craters appear to be unique in the geological environment in that they contain evidence for the presence of all four carbon allotropes: graphite, diamond, C
60
and carbynes. This diversity appears to reflect the wide range of physical and chemical conditions that occur during impact processes including shock-induced alterations and vapour-phase chemistry. Impact-produced diamonds are known from several impact craters around the world, and their ability to survive over immense periods of geological time makes the presence of diamonds an important criterion for the identification of terrestrial impact structures.
Impacts and marine invertebrate extinctions
Authors: MacLeod Norman 
Published: September 2007

AbstractThe Phanerozoic history of life has been interrupted by at least 17 different stage-level episodes of elevated extinction intensity. These range from major turnovers that affected the majority of the Earth’s extant biota (e.g. the Tatarian, Ashgill, and Maastrichtian events) to much smaller and perhaps more geographically localized disruptions. Review of available stage-level stratigraphic evidence suggests that bolide impacts do not exhibit a compelling correspondence to the Phanerozoic record of marine invertebrate extinctions. A much stronger case can be made for the repeated association of extinction events and episodes of long-term eustatic sea-level fall and/or major episodes of continental flood basalt volcanism. Moreover, during the last 250 Ma particularly severe extinction events have occurred during times of simultaneous continental flood basalt eruption and eustatic sea-level fall (e.g. Tatarian, Norian, Maastrichtian). Attempts to employ patterns of extinction selectivity to infer the physical cause of extinction events have foundered on the non-specificity of biological predictions as well as the seemingly unique biotic nature of each event. Although a few high-resolution biostratigraphic analyses have demonstrated that largely progressive patterns of faunal turnovers are consistent with co-extinction models under certain assumptions, this does not constitute a strong confirmation of the co-extinction model as a necessary or sufficient general explanation for Phanerozoic extinction events. In all likelihood, the nature of the fossil record precludes precise identification of extinction causal mechanisms. Nevertheless, comparative studies are able to evaluate the role both large and small extinction events have played in altering the long-term course of Earth’s biological history.
Timing and causes of vertebrate extinction across the Cretaceous-Tertiary boundary
Authors: Milner A. C. 
Published: September 2007

Abstract
A continuous sequence of terrestrial sediments bracketing the Cretaceous-Tertiary (K-T) boundary is known only in the western interior of North America. Documentation of terrestrial faunal diversity, and patterns of survival and extinction, demonstrate that dinosaurs (i.e. non-avian dinosaurs) declined in the Late Maastrichtian and were the only major terrestrial vertebrate group, along with the pterosaurs, that became extinct at or near the K-T boundary. There was a varying degree of turnover but no mass extinction in other vertebrate groups. Both gradualist and catastrophe scenarios have been advocated as the main cause. There is much less evidence in other parts of the world that can be brought to bear on the timing and nature of dinosaur extinction. None the less, there are dinosaur remains from Maastrichtian horizons on every continent and none are recorded from overlying Paleocene strata. This supports the axiom that dinosaurs died out world-wide at the end of the Cretaceous although there is no means of determining whether the extinction pattern in western North America was a local or global phenomenon. The disruption of reproductive patterns in herbivorous dinosaurs by trace element contamination derived from an impact, volcanic activity or both events is one factor which might correlate with their global extinction.
Lyell and the
Principles of Geology
Authors: Rudwick M. J. S. 
Published: September 2007

Abstract

Lyell’s
Principles of Geology
is still treated more often as an icon to be revered than as the embodiment of a complex scientific argument rooted in its own time and place. This paper describes briefly the origins of Lyell’s project, in the international geological debates of the 1820s and in his own early research; the structure of argument of the first edition (1830–1833), and its relation to its intended readership; and the modification of the work in subsequent editions, and the transformation of its strategy in response to its critical evaluation by other geologists. The fluidity of the
Principles
(and its offshoot the
Elements of Geology
) reflects the ever-changing interaction between Lyell and his fellow geologists, and between them and a much wider public, during one of the most creative periods in the history of geological science. Lyell’s scientific stature is best appreciated if he is placed not on a pedestal but among his peers, in debates at the Geological Society and elsewhere.
Lyell: the man and his times
Authors: Wilson Leonard G. 
Published: September 2007

AbstractBorn in Scotland at the end of the eighteenth century, Charles Lyell spent his early life in Hampshire in the midst of the kind of comfortable rural society described in Jane Austen’s novels. Influenced by his father, who was a keen botanist, the young Lyell collected butterflies and studied natural hisory. As a student at Oxford, he attended the Revd William Buckland’s lectures on geology and continued to pursue geology while studying for the bar at Lincoln’s Inn. In 1824 Lyell wrote his first scientific paper on the freshwater limestones and marls of Scottish lakes, demonstrating their detailed similarity to ancient freshwater formations among the Tertiary strata of the Paris Basin. Throughout his life Lyell remained an active field geologist, travelling throughout Europe from Sicily to Scandinavia. He made repeated geological tours through the Swiss and Austrian Alps and studied intensely the Tertiary strata of France, Belgium and England. He examined the geology of North America from Nova Scotia to the Mississippi Delta, working in the field in all weather. In 1853–1854 he spent several months studying the volcanic geology of Madeira and the Canary Islands and in 1857 and 1858 revisited Sicily to spend arduous weeks studying Mount Etna. In his seventy-fifth year and nearly blind, he travelled to the south of France to examine the caves of Aurignac and the Dordogne.In 1830 in thePrinciples of GeologyLyell challenged the assumption of a cooling Earth and of the greater former intensity of volcanic action and other geological forces. He separated geology from cosmology, pointing out that the crust of the Earth told nothing of its origin. What geology did reveal was an unending cycle of changes such as were still going on. In his metamorphic theory developed in theElements of Geology, Lyell showed how the various classes of igneous and metamorphic rocks were formed in the gradual elevation of mountains. Lyell’s theories brought about a revolution in geology, changing the meaning of geological data. In successive editions of thePrinciplesand theElements, two books of American travel, and theAntiquity of Man, Lyell’s stature as an author and as a scientist grew steadily throughout his lifetime, the sale of his books often exceeding the publisher’s expectations. Liberal in his sympathies, Lyell worked effectively for the reform of English university education and during the American Civil War defended the Union against its British critics.
Lyell’s reception on the continent of Europe: a contribution to an open historiographical problem
Authors: Vaccari Ezio 
Published: September 2007

Abstract

After the publication of the
Principles of Geology
the name of Charles Lyell became well known among European geologists. However, the diffusion of his works and the intensity of the debates on his ideas varied throughout the continent. This paper attempts to analyse some aspects of Lyell’s reception in Continental Europe, emphasizing the role of the translations of fundamental works such as the
Principles of Geology
and the
Elements of Geology
, as well as their influence on the first textbooks of geology published in Europe, especially from the 1840s onwards. Some significant examples of nineteenth-century European reactions to Lyell’s geology, and in particular to his uniformitarian statements, will be pointed out, in order to show the extent of Lyell’s influence.