bluuebunny/crossref_metadata_2025_split huggingface dataset:
Lateral diapiric emplacement of Triassic evaporites at the southern margin of the Guadalquivir Basin, Spain
Authors: Berástegui X. , Banks C.J. , Puig C. , Taberner C. , Waltham D. , Fernàndez M. 
Published: September 2007

Abstract
The Guadalquivir Basin is the Neogene foreland basin of the central and western Betic thrust belt in southern Spain. At the boundary between the basin and the outcrops of thrust nappes of Mesozoic limestones of the Prebetic and Subbetic is a broad belt of outcrops of Triassic evaporitic sediments with scattered younger rocks: the so-called ‘Olistostrome’ unit. This is highly deformed, in places chaotic, and its mode of emplacement has been attributed by various authors to olistostromal debris flow, diapirism, or tectonic melange. Studies of outcrop data in conjunction with seismic and well data, integrated using restorable cross-sections lead us to propose the following sequence of emplacement mechanisms. (a) Loading above a Triassic evaporite formation, probably in the Intermediate Units depositional zone, by north vergent thrusting of thick nappes of Mesozoic sediments, causes northward expulsion of evaporitic sediments between a basal thrust and the base of the limestones. (b) Continued thrust loading drives the diapiric body forwards ahead of the thrust belt, into the floor of the deepening Miocene foreland basin. The body includes blocks of Triassic rocks in normal stratigraphic sequence, as well as blocks of younger rocks broken off the leading hanging-wall cutoffs of the nappes. (c) When the diapiric body reaches the sea-floor of the basin, its top becomes subject to modification by sedimentary processes such as dissolution of evaporites leaving a cap rock and debris flow, both submarine and subaerial but rarely, if ever, forming true olistostromes. (d) At the leading edge of the diapir, northward compression of Miocene basin sediments results in thin-skinned thrusting within these sediments, and formation of duplex structures with a north-dipping monoclinal deformation front. Results from analogue and numerical modelling match the main geological features observed in the study area, thus supporting the plausibility of the proposed lateral diapiric emplacement of the chaotic unit.
Eustatic versus tectonic controls on Alpine foreland basin fill: sequence stratigraphy and subsidence analysis in the SE German Molasse
Authors: Zweigel J. , Aigner T. , Luterbacher H. 
Published: September 2007

Abstract

A sequence-stratigraphic and subsidence analysis in the SE German Molasse basin was carried out based on well and seismic data. The sequence-stratigraphic study revealed that the basin fill is composed of five second-order sequences. Sequences 3 and 4 can be subdivided into several third-order sequences. Seismic facies maps illustrate the temporal and spatial evolution of the study area. Comparison of an accommodation curve of the Molasse basin with the eustatic sea-level curve of Haq
et al
. (
Science
, 1987,
235
, 1156–1167) showed, that the sequence stratigraphic subdivision was mainly controlled by eustatic sea-level fluctuations.

Subsidence analysis revealed a major flexural event in the SE German Molasse basin from late Eocene to early Miocene (late Egerian), followed by a possible visco-elastic relaxation of the lithosphere responsible for the formation of an angular unconformity between the two classical transgressive-regressive megacycles of the Molasse stratigraphy (early Miocene, late Egerian-Eggenburgian boundary). A phase of relatively uniform, decreasing subsidence followed until the end of Molasse sedimentation, when an isostatic rebound resulted in the uplift of the basin. The subsidence analysis also revealed, that even though eustacy controlled sequence boundary formations, the interplay between subsidence and sedimentation rates, both governed by tectonics, controlled the transgressive-regressive megacycles. However, the coupling of the two factors depends on the tectonic process.
Major occurrences and reservoir concepts of marine clathrate hydrates: implications of field evidence
Authors: Booth J. S. , Winters W. J. , Dillon W. P. , Clennell M. B. , Rowe M. M. 
Published: September 2007

Abstract
Questions concerning clathrate hydrate as an energy resource, as a factor in modifying global climate and as a triggering mechanism for mass movements invite consideration of what factors promote hydrate concentration, and what the quintessential hydrate-rich sediment may be. Gas hydrate field data, although limited, provide a starting point for identifying the environments and processes that lead to more massive concentrations. Gas hydrate zones are up to 30 m thick and the vertical range of occurrence at a site may exceed 200 m. Zones typically occur more than 100 m above the phase boundary. Thicker zones are overwhelmingly associated with structural features and tectonism, and often contain sand. It is unclear whether an apparent association between zone thickness and porosity represents a cause-and-effect relationship. The primary control on the thickness of a potential gas hydrate reservoir is the geological setting. Deep water and low geothermal gradients foster thick gas hydrate stability zones (GHSZs). The presence of faults, fractures, etc., can favour migration of gas-rich fluids. Geological processes, such as eustacy or subsidence, may alter the thickness of the GHSZ or affect hydrate concentration. Tectonic forces may promote injection of gas into the GHSZ. More porous and permeable sediment, as host sediment properties, increase storage capacity and fluid conductivity, and thus also enhance reservoir potential.
Seismic tomography study of a bottom simulating reflector off the South Shetland Islands (Antarctica)
Authors: Tinivella U. , Lodolo E. , Camerlenghi A. , Boehm G. 
Published: September 2007

Abstract
Reflection tomography techniques have been applied to two multi-channel seismic profiles, acquired across the accretionary prism of the South Sheltand margin, in order to reconstruct the velocity field associated with gas hydrate and free gas layers in the sedimentary sequence. Data show the presence of a strong bottom simulating reflector (BSR), running along the slope in water depths ranging from 1000 to 4600 m, locally underlain by a weak normal polarity reflector about 80 ms deeper in the section. The analysis indicates a velocity trend from the sea floor to the BSR generally consistent with that of normally compacted marine sediments, with an abrupt decrement between the BSR and the underlying reflector, indicating the presence of free gas in the sediment pore spaces. The calculated thickness of this gas-bearing layer is approximately 50 m. Local increments of tomographic velocity above the BSR can be related either to gas hydrate abundances in normally compacted slope basin sediments or to overcompaction in accreted sediments, as imaged by the pre-stack depth migrated sections. We conclude that clathrates and free gas distribution on the South Shetland continental slope are strongly controlled by the structural setting of the accretionary prism, where faults act as conduits for migration of natural gas towards the surface. A brief description of the adopted tomography method is also presented.
Extraterrestrial impacts on earth: the evidence and the consequences
Authors: Grieve Richard A. F. 
Published: September 2007

AbstractThe terrestrial record of impact events is incomplete and evolving. There are inherent biases in ages, distribution and sizes of known impact events that result from the high levels of endogenic activity on the Earth. Nevertheless, an estimated terrestrial cratering rate of (5.6 ± 2.8) × 10−15km−2a−1for impact structures with diameters >20 km and younger than 120 Ma can be calculated and is compatible with astronomical observations. The most obvious evidence of impact is the occurrence of 156 impact structures known as of the end of 1996. Few impact structures, however, are sufficiently pristine to provide great detail concerning their original morphology. Some basic morphometric parameters, however, can be estimated. Confirmation of an impact origin for particularly terrestrial structures comes generally from the recognition of diagnostic shock metamorphic effects in the target rocks. Some 16 impact events are currently recognized in the stratigraphic column but it would appear that many others await discovery. The best documented and only global example of such events is at the Cretaceous-Tertiary (K-T) boundary. Although a number of killing mechanisms have been proposed for the attendant mass extinction, the nature of the target, in this case containing sulphates, may be the reason for the devastating effect of this event on the biosphere. In early Earth history, the high impact flux was probably a significant factor in the modification of the atmosphere, biosphere and hydrosphere and the collision of a Mars-sized object with the proto-Earth may have been responsible for the formation of the Earth’s Moon. Prompted by the association of the K-T event with a global mass extinction, it has been proposed that other mass extinctions and geological phenomena in the Phanerozoic are impact related, possibly through periodic cometary showers. At this time, there is little or no evidence for this association, although model calculations and the terrestrial cratering rate suggest that impact cannot be ignored as a forcing function for transient changes in the Earth’s atmosphere and climate. Although unequivocal evidence linking impact to climatic changes remains to be discovered, it is a statistical certainty that if human civilization exists for time-scales of hundreds of thousands of years it will be severely affected or possibly destroyed by an impact event. Given the stochastic nature of impact events, however, this could happen sooner rather than later.
Localized shock- and friction-induced melting in response to hypervelocity impact
Authors: Spray John G. 
Published: September 2007

Abstract

The distribution of shock veins, friction melts and cataclastic rocks in complex impact craters reflects the response of target lithologies to varying rates of strain. Within the Sudbury impact structure, thin (<2 mm), anastomosing veins, which can define shatter cone surfaces, permeate the target rocks in a
c.
15 km wide zone around the Sudbury igneous complex (SIC). A similar relationship exists within the Vredefort impact structure, with the additional association of the high-pressure SiO
2
polymorphs coesite and stishovite. These S- (shock-dominant) type pseudotachylytes are comparable with shock veins developed in meteorites. Both are considered to form primarily by shock compression-decompression during the contact and compression stage of the collision process. Larger, thicker (up to 1 km wide) friction melt bodies constitute pseudotachylytes formed by the extreme comminution of fault walls during rebound and gravitational collapse of the transient cavity. They also appear to define the concentric fault systems of multi-ring impact basins. These E- (endogenic-) type pseudotachylytes form during the modification stage of the cratering process and post-date S-type pseudotachylytes. At Sudbury, they occur up to 80 km beyond the SIC. E-type pseudotachylytes are formed by the same mechanism as pseudotachylytes in non-impact-related fault systems: frictional melting of fault walls during seismogenic slip. Those in impact structures can be large because the extreme displacements (several kilometres) facilitated by superfaults generate massive volumes of friction melt.
Lyell and the dilemma of Quaternary glaciation
Authors: Boylan Patrick J. 
Published: September 2007

Abstract
The glacial theory as proposed by Louis Agassiz in 1837 was introduced to the British Isles in the autumn of 1840 by Agassiz and his Oxford mentor, William Buckland. Charles Lyell was quickly converted in the course of a short period of intensive fieldwork with Buckland in and around Forfarshire, Scotland, centred on the Lyell family’s estate at Kinnordy. Agassiz, Buckland and Lyell presented substantial interrelated papers demonstrating that there had been a recent land-based glaciation of large areas of Scotland, Ireland and northern England — at three successive fortnightly meetings of the Geological Society of London, of which Buckland was then President, in November and December 1840. However, the response of the leading figures of British geology was overwhelmingly hostile. Within six months Lyell had withdrawn his paper and it had become clear that the Council of the Society was unwilling to published the papers, even though they were by three of the Society’s most distinguished figures. Lyell reverted to his earlier interpretation of attributing deposits such as tills, gravels and sands and the transport of erratics to a very recent deep submergence with floating icebergs, maintaining this essentially ‘catastrophist’ interpretation through to his death a quarter of a century later.
Catastrophism and uniformitarianism: logical roots and current relevance in geology
Authors: Baker Victor R. 
Published: September 2007

AbstractCatastrophism in the Earth sciences is rooted in the view that Earth signifies its causative processes via landforms, structures and rock. Processes of types, rates and magnitudes not presently in evidence may well be signified this way. Uniformitarianism, in contrast, is a regulative stipulation motivated by the presumed necessity that science achieves logical validity in what can be said (hypothesized) about the Earth. Regulative principles, including simplicity, actualism and gradualism, are imposeda priorito insure valid inductive reasoning. This distinction lies at the heart of the catastrophist versus uniformitarian debates in the early nineteenth century and it continues to influence portions of the current scientific program. Uniformitarianism, as introduced by Charles Lyell in 1830, is specifically tied to an early nineteenth century view of inductive inference. Catastrophism involves a completely different form of inference in which hypotheses are generated retroductively. This latter form of logical inference remains relevant to modern science, while the outmoded notions of induction that warranted the doctrine of uniformitarianism were long ago shown to be overly restrictive in scientific practice. The latter should be relegated solely to historical interest in the progress of ideas.
Extrusions of Hormuz salt in Iran
Authors: Talbot Christopher J. 
Published: September 2007

AbstractThis work illustrates that Lyell’s approach to inferring geological processes from field observations can be improved by using field measurements of their rates to scale dynamic models. A controversy in the 1970s about whether crystalline rock salt can flow over the surface echoed an earlier controversy resolved with Lyell’s help about whether ice could flow and carry exotic blocks. This work argues that the external shapes, internal fabrics and structures and rates of flow of current salt extrusions in the Zagros Mountains are keys not only to understanding past and future extrusion of salt, but also to the extrusion of metamorphic cores of orogens.Salt is shown to extrude first in hemispherical domes, which later spread to the shapes of viscous fountains until they are isolated from their source. They then rapidly assume the shapes of viscous droplets, which they maintain until they degrade to heaps of residual soils. Salt emerges as a linear viscous Bingham fluid, and strain rate hardens downslope to a power-law fluid (n= 3) beneath a thickening carapace of brittle dilated salt.The velocities of salt constrained in emergent diapirs by measurements of extruding salt sheets in Iran are remarkably rapid compared with rates estimated for buried equivalents elsewhere in or under which it is planned to store nuclear waste or to extract hydrocarbons.
The Pharmacokinetics of The Biliary Excretion of Ciprofloxacin
Authors: Ball C. S. , Manson J. Mck. , Reid Fiona , Tweedle D. E. F. 
Published: September 2007

The pharmacokinetics of ciprofloxacin excretion have been studied in 54 patients undergoing biliary and
pancreatic operations with and without obstruction of the common bile duct. High concentrations were
achieved in common duct bile within 20 minutes of intravenous injection and persisted for over 3 hours
after 100 mg and for over 8 hours after 200 mg. The concentration of ciprofloxacin in the bile of functioning
gall bladders was much greater than that in the common duct bile. Remarkably, it was identified in
therapeutic concentrations in the bile of obstructed ducts. This and the rapid fall from initially high venous
concentrations probably reflect diffusion from the circulation as a result of the exceptional tissue
penetration. A unique feature of this study was the finding of clinically significant concentrations in the
bile of obstructed ducts.Two patients developed wound infection and no side effects were observed. The broad spectrum
antibiotic ciprofloxacin has potential as a useful agent for prophylaxis in biliary surgery maintaining biliary
and venous concentrations in excess of the MIC90 for most biliary pathogens for more than 8 hours.
Percutaneous Management of Pyogenic Liver Abscesses
Authors: Helenon O. , Krachte M. , Mathieu D. , Vasile N. , Rotman N. , Fagniez P. –L. 
Published: September 2007

Twenty‐four pyogenic liver abscesses have been treated during a six‐year period percutaneously.
Percutaneous management included percutaneous drainage and fine needle aspiration under ultrasound
or CT scan guidance. Percutaneous management was successful in 92% of cases, and no further treatment
was required in 91% of these.One patient died, giving a mortality rate of 4.1%. There were no complications related to this method.
The authors conclude that percutaneous management of pyogenic liver abscesses should be attempted in
all cases, since results compare favourably with surgical procedures.
Early and Late Results FollowingCholedochoduodenostomy andCholedochojejunostomy
Authors: Blankensteijn J. D. , Terpstra O. T. 
Published: September 2007

Objective —To evaluate the results and complications of choledochoduodenostomy
and choledochojejunostomy for benign and malignant disease and to review
them in the light of the survival of the underlying disorders.Design —Retrospective analysis of medical records completed by a thorough
inquiry for all patients who were lost to follow‐up.Setting —Referrals for primary and secondary surgery for obstructive biliary disease
to a university hospital from 1974–1987.Patients —After exclusion of patients who underwent a pancreaticoduodenectomy
for cancer (Whipple procedure) 113 patients were included in the study (choledochoduodenostomy =
CD, N = 64 and choledochojejunostomy = CJ, N = 49). A
complete follow‐up was achieved in 105 of 113 patients (93%).Interventions —An inquiry was made at the civil registration office if the patients
were alive or not. The general practitioners of the patients who had died were
contacted about the cause of death and the possible biliary symptoms preceding
death and the patients who were still alive received a questionaire which scrutinized
all possible complications and side effects of the operation.Endpoints —Cholangitis, recurrence of the underlying disease or death of the patient.Measurements and main results —Operative mortality was 4.7% following CD and
12.2% following CJ. Procedure‐related complications were found in 10.9% and
28.6% respectively. Recurrent cholangitis was not seen after CD and in three patients
with a CJ (6.1%). Survival following biliodigestive anastomosis for benign obstruction
was comparable for age and sex matched survival.Conclusions —Although CD for choledocholithiasis has largely been replaced by
endoscopic papillotomy and although the choice between the two procedures in
malignant disease is most frequently dictated by the operative findings, we conclude
that the choledochoduodenostomy is a relative simple operation with a low risk of
cholangitis.
Pylorus‐Preserving Pancreatoduodenectomy. Experience in 20 Patients
Authors: Lerut J. , Luder P. J. , Krähenbiühl L. , Gertsch P. H. , Blumgart L. H. 
Published: September 2007

Twenty patients underwent a pylorus‐preserving pancreatoduodenectomy for benign or malignant
periampullary and pancreatic disease. Eighteen patients had a partial and two patients a total
pancreatectomy. There were 19 elective and 1 emergency operations.Post‐operative mortality was 4% (1/20 patients) and the median follow up was 31 months (range, 15–
75 months), during which period 8 patients with a malignant disease died.Pylorus‐preserving pancreatoduodenectomy did not compromise survival in ampullary cancer.One patient developed a marginal ulcer during the study period and one of twelve patients, examined
by technetium scintigraphy (done more than 3 months after the procedure), had delayed gastric
emptying. Two patients presented with a gastric retention as the first sign of recurrent pancreatic cancer.The result of the operation was judged as excellent in 7 patients, good in 8 and as bad in only 2 of the
17 patients who survived more than 6 months . Body weight was studied in 15 patients surviving more
than one year after operation; five patients had gained weight, two had lost weight and in 8 there was no
difference.Pylorus‐preserving pancreatoduodenectomy seems to be a valuable alternative in the treatment of
patients with benign and selected malignant pancreaticobiliary disease.
The Possible Role of Sphincteroplasty and Surgical Sphincterotomy in the Pathogenesis of Recurrent Common Duct Brown Stones
Authors: Cetta Francesco 
Published: September 2007

The hypothesis has been tested that postcholecystectomy common duct stones of the brown subtype are
a consequence of three factors: bile infection, old age and previous sphincterotomy. It was found that:
(i) 27 of 39 consecutive patients with recurrent common duct stones had brown stones. Nineteen of these
27 patients (70.3%) had previous sphincterotomy or sphincteroplasty: (ii) six of 15 patients with stone
and bile analysis both at the time of cholecystectomy and at the second operation and who had sterile
operative bile and non brown stones at the first operation, formed brown stones after T‐tube drainage
and after the onset of bile infection; (iii) patients with both intra and postoperative negative bile culture
(n = 39 out of 137) had a lower mean age (50.5 years) and less frequently had a sphincterotomy than did
individuals with a negative culture at operation, who subsequently had bile infection (n = 37; mean age
58.5 years; sphincterotomy in 88.8% of cases).In addition, in a follow up study of 105 patients with sphincterotomy and with sphincteroplasty
(including ERCP or i.v. cholangiography in all cases), mean follow‐up interval 6.1 years, 11.3 % of
patients had brown recurrent common duct stones.It is suggested that, since brown recurrent common duct stones are secondary to bile stasis and
infection and the duodenum is going to be colonized by bacteria with increasing age, sphincterotomy
(and subsequent stricture), facilitating bile contamination and bacterial overgrowth, could be one of the
major determinants of brown recurrent common duct stones (RCS) formation. In particular, more than
11% of the patients with a sphincterotomy are going to form in the future RCS of the brown subtype.