bluuebunny/crossref_metadata_2025 huggingface dataset:
Stable isotopes of carbon and sulphur as indicators of environmental change: past and present
Authors: Newton Rob , Bottrell Simon
Published: December 2007

Stable isotopes of carbon (
12
C and
13
C) and sulphur (
32
S and
34
S) are fractionated during some of the transformations between reservoirs in the global carbon and sulphur cycles. The main processes controlling the isotopic composition of Earth surface reservoirs are, for carbon, photosynthesis, respiration and equilibration between oceanic dissolved inorganic carbon and atmospheric CO
2
, and, for sulphur, bacterial sulphate reduction and sulphide reoxidation. Thus the different reservoirs of carbon and sulphur in the global cycles attain characteristic isotopic compositions that can be used as a ‘fingerprint’ for different carbon and sulphur sources and to track changes in the balance of carbon and sulphur stored in different reservoirs. These isotopic signals can be used both to examine contemporary anthropogenic impacts on the cycling of carbon and sulphur and, where isotopic compositions are faithfully preserved in ancient sediments, to examine historical changes in global geochemical cycles through geological time. A number of case studies are discussed to illustrate how isotopic techniques represent one of the most powerful and important tools available in the study of both the causes and affects of ancient and modern global environmental change.
Structural and stratigraphic controls on fold-related fracturing in the Zagros Mountains, Iran: implications for reservoir development
Authors: Stephenson Ben J. , Koopman Anton , Hillgartner Heiko , McQuillan Harry , Bourne Stephen , Noad Jon J. , Rawnsley Keith
Published: December 2007

New observations of fracture corridors > 150 m tall and planes of bedding-parallel slip are integrated with sedimentological descriptions of the Asmari Formation to understand the main controls on the development of fractures in the Zagros Mountains of Iran. In the Kuh-e Pahn, fold-related fracture corridors are axis-parallel (NW-SE) and occur in the crest of the anticline. They form by neutral surface folding, but at a critical dip of the beds (c. 15°), bedding-parallel slip by flexural slip folding is the predominant mechanism. This relationship is substantiated by curvature calculations. Crestal fractures have a large vertical extent in mechanical unit B (> 150 m), primarily due to the lithological homogeneity of massive packstones within the Asmari Formation. Northerly and easterly trending fracture corridors, interpreted from satellite imagery, are spatially unrelated to the detachment folding of the cover series, but represent the distributed effect of deep-seated basement reactivation related to fault movement. These trends define high production zones in the nearby Gachsaran super giant oilfield. Observations from an adjacent eroded box fold, the Kuh-e Mish, with steeper dipping limbs (60°), revealed a contrast in the style of deformation, and we interpret these folds to represent different stages in box fold evolution.
Laboratory measurements of acoustic emissions and wave velocities associated with the formation of fractures in sandstones
Authors: Pettitt W. S. , King M. S.
Published: December 2007

Acoustic emission (AE), ultrasonic velocity and petrophysical property measurements are increasingly being used as tools to investigate mechanical, thermal and hydraulic changes in rock masses around underground excavations and in the exploration of oil and gas. In order to develop these measurements into an effective tool it is necessary to understand how they relate to changes in the fracture and fluid content under controlled laboratory conditions. A polyaxial (true triaxial) test system has been developed to perform high-resolution measurements of AE, ultrasonic velocities and fluid permeability characteristics in a cubic specimen under true-triaxial stress. The polyaxial system also allows the measurement of AEs using an array of small-diameter, high-frequency transducers. The measurements allow the AE source locations and mechanisms to be calculated, thus providing an analysis of the distribution, orientation and type of fracture growth in the specimens. Example results are given from an experiment, showing that AE mechanisms during crack initiation describe a dominant failure mode with a significant tensile component.
Combining diagenesis and mechanics to quantify fracture aperture distributions and fracture pattern permeability
Authors: Olson Jon E. , Laubach Stephen E. , Lander Robert H.
Published: December 2007

Diagenesis and fracture are often linked processes in deformed rock. Empirical observations show that quartz-lined natural fractures are very common in sandstones that have been exposed to temperatures in excess of 90°C. These fractures exhibit crack-seal textures as well as cement bridges propping the fractures open and preserving fracture porosity. These diagenetic effects are examined in the context of detailed fracture characterizations generated by geomechanical modelling. Aperture, length and fracture network geometry are examined in the context of subcritical crack growth and various biaxial loading boundary conditions of varying initial anisotropy. An isotropic initial state results in more polygonal fracture patterns. A small initial anisotropy creates preferential through-going fractures that are later connected by cross-fractures. A larger initial anisotropy results in only one parallel set. The flow connectivity of isotropic and small strain anisotropic patterns appears high based on trace pattern geometry, but when the effects of diagenesis are added, preferentially filling smaller aperture fracture segments, connectivity can be significantly reduced. Finite difference, steady-state flow simulations demonstrate the permeability effects of heterogeneous fracture aperture distributions predicted by the mechanical model and permeability reduction caused by systematic diagenetic fracture sealing.
Understanding the Earth scientist's role in the pre-restoration research of monuments: an overview
Authors: Přikryl R.
Published: December 2007

To understand the role of the earth scientist in the pre-restoration research of stone monuments, it is necessary to summarize the tasks that he/she can fulfil. Pre-restoration research into building materials is generally conducted to provide information on types of material, their damage and repair. Although the technologist and restorer must manage the practical aspects of repair, the earth scientist can make a significant contribution in terms of material research. First, he or she can answer questions on the nature of the stone(s) used, their provenance (location of the quarry), and their weathering characteristics in terms of the deterioration of physical and mechanical properties and destruction of rock fabric. Second, the earth scientist can research the physical and mechanical properties of new stone proposed for as a replacement for decayed stonework, including recommendations for alternative materials where stone from the original quarry is no longer available.
Characterization of serpentinites to define their appropriate use as dimension stone
Authors: Pereira D. , Yenes M. , Blanco J. A. , Peinado M.
Published: December 2007

Many questions arise when considering the appropriate use of building stones such as serpentinites. The commercial names of these rocks, collectively grouped as ‘Green marbles’, have no correspondence to their actual mineralogy, geochemistry and/or physical characteristics. Serpentinite being the hydrated product of an ultramafic parent rock and not a metamorphic product of limestone as implied by the term ‘marble’. However, the serpentinites most widely used for ornamental purposes come from India (e.g. Rajasthan Green, Emerald Green) and in these the original mineralogy has been almost completely converted into carbonates. By contrast, serpentinites from elsewhere (e.g. Vermont Verde Antique from the USA and Verde Pirineos from Spain) do preserve some of their original mineralogy. The different physical and chemical behaviour of carbonates and serpentine minerals can result in significantly different behaviour of commercial building stones. Thus, carbonates are resistant to weathering but suffer from acidic cleaning agents in interior use; whereas serpentinites, with a high content of talc, used on external faces undergo an increase in volume and a consequent rapid degradation.

Accurate and precise characterization of serpentinites, including information on their mineralogy and geochemistry (including major, trace and volatile elements together with oxygen isotopes), in conjunction with their physical properties, would enable architects to select the appropriate interior or exterior use of these handsome building stones.
Stone properties and weathering induced by salt crystallization of Maltese Globigerina Limestone
Authors: Rothert E. , Eggers T. , Cassar J. , Ruedrich J. , Fitzner B. , Siegesmund S.
Published: December 2007

Most monuments and buildings in the Maltese Islands are constructed of the local Globigerina Limestone. Today, this Globigerina Limestone shows considerable damage in many buildings, particularly through alveolar weathering, which is frequently very intense. Owing to Malta's marine environment, salt crystallization in the stone's pore spaces has been recognized as the main weathering process responsible for the deterioration of the country's monuments. In order to obtain more information on the fabric-dependent weathering processes of Globigerina Limestone, detailed analyses were carried out. Globigerina Limestone samples obtained from stone types with two different known qualities were characterized according to petrographical, geochemical and physical properties. These included porosity, pore radii distribution and tensile strength, as well as water and humidity transport properties. Investigations by means of salt crystallization tests on quarry samples of both stone types reinforced the idea that the extent of salt weathering depends on salt type and concentration and pore-space properties. Visible weathering damage was recorded and evaluated for a representative monument (the Church of Santa Marija Ta' Cwerra in Siggiewi) by means of a monument mapping method, which was carried out twice over a period of 9 years (1995 and 2004). The identified weathering forms were also correlated with a previously developed weathering model for Globigerina Limestone. According to the results of the mapping, salt analyses carried out on samples from the church and salt-loading tests on quarry samples, there exists a significant correlation between visible damage and salt load. The zoning of weathering damage is obviously related to different salt concentrations. The zone with severe weathering damage is characterized by a high concentration of halite. Consequently, salt weathering represents the main damage process for the Globigerina Limestone of Malta.
Controls on permeability: implications for stone weathering
Authors: McKinley J. M. , Warke P. A.
Published: December 2007

In the light of a well-researched relationship between rock properties and susceptibility of stone to weathering, the role of permeability in weathering is examined. A review of weathering studies indicates the varied use and nature of porosity data, but the paucity of permeability studies in weathering trials. Key factors that control porosity and permeability, depositional characteristics and diagenetic processes are discussed and investigated, with a view to discussing the implications for stone weathering. Results from experimental studies on a range of rock types comprising sandstone, limestone and granite are presented. The relevance of permeability measurement is explored in terms of spatial mapping and quantitative assessment of the deterioration of natural building stone. Increased knowledge and appreciation of the inherited characteristics of a rock is demonstrated to provide valuable insight and a greater understanding of how natural stone heterogeneity is accentuated and exploited by weathering and continued exposure to moisture and salts. Mapping the spatial distribution of permeability provides greater insight into the extent of variability in stone deterioration and presents the possibility of monitoring and predicting the hydraulic properties of stone and how these are modified by weathering processes.
Overview of recent knowledge of patinas on stone monuments: the Spanish experience
Authors: Vazquez-Calvo C. , Alvarez de Buergo M. , Fort R.
Published: December 2007

The historic treatment of stonework has often been linked to the artificial application of patinas, mainly for aesthetic and protective reasons. Increasingly, however, researchers have identified a possible combined origin for patinas that has linked natural, biological processes to those associated with an artificial, man-made origin. This suggests that, although coatings may have been initially applied on purpose, they transform over time with the aid of micro-organisms and other chemical interactions. The original mixture applied to create a patina could include lime and/or gypsum, water, natural pigments and organic additives. However, their present-day mineralogy is varied and includes a wide range of minerals from calcium carbonates to calcium sulphates, calcium oxalates, calcium phosphates, silicates (quartz, feldspar, clay minerals) and iron oxides/hydroxides. Patinas have been studied in detail in Greece and Italy, but rarely in Spain. In this paper, existing knowledge on Spanish patinas is co-ordinated and previous and current research summarized. Emphasis is placed on artificial patinas initially applied to protect stone. These both appear to effectively protect the stone substrates on which they were applied and provide an insight into historical techniques of stone conservation. Because of this their preservation should be a strong consideration in restoration projects. Ongoing research focuses on the challenges of reproducing patinas, based on historical references.
From myth to Earth education and science communication
Authors: Lanza Tiziana , Negrete Aquiles
Published: December 2007

There is a longstanding and intimate relationship between myths and the Earth. Myths represent human beings in childhood when a primitive language made of symbols transmitted the wisdom necessary to live in harmony with nature. Today science uses mainly the language of data. Nevertheless, myths and legends are still popular and part of our culture, and the Earth sciences remain confined mostly to the world of scientists. This paper is an attempt, from the perspective of science communication, to provide a theory that uses myths and legends to stimulate the curiosity of the man in the street about the planet we live on. Recent studies have demonstrated that fictional stories can be used to convey science to the general public in an accurate, memorable and enjoyable way. Following these ideas, we believe that myths can be a useful tool for Earth science studies, learning and popularization.
Folklore and earthquakes: Native American oral traditions from Cascadia compared with written traditions from Japan
Authors: Ludwin Ruth S. , Smits Gregory J. , Carver D. , James K. , Jonientz-Trisler C. , McMillan A. D. , Losey R. , Dennis R. , Rasmussen J. , De Los Angeles A. , Buerge D. , Thrush C. P. , Clague J. , Bowechop J. , Wray J.
Published: December 2007

This article examines local myth and folklore related to earthquakes, landslides, and tsunamis in oral traditions from Cascadia (part of the northern Pacific coast of North America) and in written traditions from Japan, particularly in the Edo (present-day Tokyo) region. Local folklore corresponds closely to geological evidence and geological events in at least some cases, and the symbolic language of myth and folklore can be a useful supplement to conventional geological evidence for constructing an accurate historical record of geological activity. At a deep, archetypical level, Japan, Cascadia, and many of the world's cultures appear to share similar themes in their conception of earthquakes. Although folklore from Cascadia is fragmentary, and the written record short, the evolution of Japanese earthquake folklore has been well documented over a long period of history and illustrates the interaction of folklore with dynamic social conditions.
Band-e-Amir Lakes and Dragon Valley (Bamiyan): myths and seismicity in Afghanistan
Authors: Bourrouilh-Le Jan F. G. , Akram B. , Schvoerer M.
Published: December 2007

Located SW of the Hindu Kush range, the Band-e-Amir lakes and other continental bioherms around Bamiyan are famous for their ordering into terraces and their great variety of colours. Numerous legends, the earliest likely dating to the establishment of the Zoroastrian religion, refer to the topography, ecology, and colours of the lakes and seismic activity of the area. The lakes have been formed by the chemical and biologically-induced build-up of semicircular or successive linear travertine dams. The discovery of a highly truncated karstic network located at an elevation of around 4000 m. along the base of Maastrichtian carbonate cliffs surrounding the lakes, may explain the presence of this carbonate sedimentation which has fluctuated with time and was responsible for legendary floods. Localized at the eastern end of the Herat strike-slip fault, the timing and duration of the build-ups and lakes are under the influence of intense seismic activity, partially due to the seismic activity of the nearby Hindu Kush, in relation to the northern drift of the Afghan Gondwanian block towards the Eurasiatic plate. These bioherms and lakes occur in an area of high risk; a zone of floods, freezing temperatures, earthquakes and rock avalanches caused by the high altitude and location in the Himalayan alpine belt. These natural features have affected local populations beginning with the movement into the area of more or less sedentary people, apparently coming from the Bactrian province. Such a fragile biological and sedimentological environment should be maintained by organized governmental assistance, with a primary goal of protecting the local inhabitants, but also preserving this exceptional environment for others to enjoy.
Exploding lakes in myth and reality: an African case study
Authors: Shanklin Eugenia
Published: December 2007

In the night of 21 August, 1986. Lake Nyos, a crater lake in the Cameroon Grassfields of West Central Africa, ‘exploded’ and sent out a cloud of carbon dioxide that killed more than 1800 people. Ultimately the causes of the explosion were scientifically determined to have been limnological. They were part of a process, much like the opening of a champagne bottle, in which carbon dioxide that has collected at the bottom rises quickly to the top and, following the ‘pop’ of the cork, sends out a liquid mixture of wine and carbon dioxide. Carbon dioxide at the bottom of small Lake Nyos (roughly the size and shape of New York's Chrysler Building; 319m in height) was disturbed by an unknown force that caused it to ‘pop’ out as a deadly cloud about 700 m long, deep and wide. Stories about ‘misbehaving’ or exploding lakes had circulated in the region for many years before the 1986 explosion, and continue to circulate. This article summarizes eighty years of myth collection carried out by ethnographers, historians, administrators and missionaries who visited prior to the 1986 explosion. It also adds information about myth transformations and new folklore explanations for the Nyos explosion over 13 years following the explosion, and contributes to the discussion of implications for disaster relief in any large-scale catastrophe.
Cosmogenic mega-tsunami in the Australia region: are they supported by Aboriginal and Maori legends?
Authors: Bryant E. , Walsh G. , Abbott D.
Published: December 2007

Mega-tsunami have affected much of the coastline of Australia over the past millennium. Such catastrophic waves have left an imprint consisting predominently of bedrock sculpturing of the rocky coastline and deposition of marine sediments to elevations reaching 130 m above sea level. One of the largest of these events occurred in eastern Australia in the fifteenth century. This event may be related to the Mahuika impact crater found at 48.3 S, 166.4 E on the continental shelf 250 km south of New Zealand. A comet at least 500 m in diameter formed the crater. Maori and Aboriginal legends allude to significant cosmogenic events in the region, while Aboriginal legends about tsunami are common along the eastern Australian coast. Evidence for legends that could describe the impact of a cosmogenic tsunami also exists in NW Australia. Here geological evidence of a single mega-tsunami as recent as in the seventeenth century covers 1500 km of coastline. We term this event Wandjina after the artwork related to the legends. More attention should be given to oral traditions in searching globally for other sites of significant mega-tsunami.
A model for simulating the dispersal tracks of sand grains in coastal areas: ‘SandTrack’
Authors: Soulsby R. L. , Mead C. T. , Wild B. R.
Published: December 2007

A new model is described that simulates the paths taken by a large number of identified (‘tagged’) sand grains in coastal areas in response to waves and currents. A number of practical applications require such a Lagrangian approach, as distinct from the more traditional Eulerian calculations of the transport rates of bulk quantities of identical, non-tagged, grains. Such applications might include studies on the dispersal of dredged spoil, or on the release of contaminated particulate material.

The particle-tracking algorithm determining the movement of tagged grains takes account of the following processes:

burial and re-emergence

initiation of motion and entrainment by combined waves and currents

bedload transport

suspended transport

turbulent diffusion.

A novel method of simulating these processes has been devised, by formulating functions to parameterize each of them, and then specifying a grain speed as the product of the functions. The particle-tracking algorithm is implemented within HR Wallingford's SEDPLUME-RW model, originally devised to track the dispersal of muddy sediments. This in turn is driven by currents and waves computed by the hydrodynamic model TELEMAC. A validation exercise simulating dispersal of radioactive sand tracer measured in the 1960s in Morecambe Bay is described.
The use of particle tracking in sediment transport studies: a review
Authors: Black Kevin S. , Athey Sam , Wilson Peter , Evans Darren
Published: December 2007

New European environmental legislation such as the Shellfish and Habitats Directives, together with the more recent Water Framework Directive, are driving new and fresh approaches to sediment management. Regional authorities, environment protection agencies and consultants are increasingly being required to adopt a holistic, system-wide appreciation of sediment flux in aquatic systems. Increasingly, and necessarily, there is a need to describe sediment (and contaminant) transport pathways on dynamically variable and spatially distributed scales rather than at single point localities. ‘Particle tracking’, or as it is also known ‘particle’ or ‘sediment tracing’, providing certain assumptions are satisfied, offers a practical methodology for the assessment of transport pathways of a variety of sediments across wider temporal and spatial scales, and is available for silts, sands, granules, pebbles and cobbles. Although not a new technique, particle tracking has experienced a resurgence of interest and application by geologists, hydrologists and oceanographers principally as a result of the arrival of new, innovative manufacturing and measurement technologies. These have overcome previous limitations presented by the method, and have also provided a foundation for silt tracking that previously did not exist. The purpose of this paper is to provide an overview of the particle tracking methodology in the modern context, with a bias towards the practicalities of conducting a tracking experiment. We present a detailed summary of the factors and considerations involved in conducting tracking studies, including an assessment of tolerance limits on synthetic tracers and the importance of appropriate sampling strategies. In addition, we highlight the principal technical limitations of the method. We summarise the historical background regarding the use of the particle tracking method outlining the dominance of studies on sand transport and the paucity of silt tracking studies, and draw attention to some of the potential areas of application of this innovative approach.
Mesoscale changes in present-day nearshore surface sediments and bedforms off the north coast of Ireland
Authors: McDowell J. Lyn , Knight Jasper , Quinn Rory
Published: December 2007

The distribution and spatial patterns of surficial nearshore sediments off the north coast of Ireland were mapped in detail using three repeated (over one year total duration) dual-frequency (100–500 kHz) side-scan sonar surveys which were ground-truthed using a bucket-grab sediment sampler. In the study area (40 km
2
, < 30 m water depth), three acoustic facies were identified (interpreted as sand, gravel, and bedrock). Planar sand with small sand waves dominates most of the study area; bedforms developed on sand and gravel substrates are located around the margins of a bedrock-floored bathymetric trench. Unusual sea-going gravel ‘ribbons’, which morphologically resemble rip current chutes, feed into the trench. Temporal changes in substrate and bedform patterns, mapped from the side-scan sonar data, suggest bedform development and facies boundary migration (by > 100 m distance) over the winter season followed by sediment migration back again during the summer. Generally, substrate and bedform mobility is likely to be related to changes in the relative strengths of waves and tides along this exposed, mesotidal coast. More specifically, tidal asymmetry and the formation of a headland leeside eddy can account for scouring of the trench, trench-flank bedform patterns developed in sand, and the formation of the gravel ribbons.
An application of sediment trend analysis to Carmarthen Bay, Bristol Channel
Authors: Cooper Bill , McLaren Patrick
Published: December 2007

Carmarthen Bay is a large embayment on the northern coast of the Bristol Channel; a location that is exposed directly exposed to both Atlantic waves and a macro-tidal environment. Until recently this embayment was comparatively poorly described in terms of its sediment regime. In particular, limited data were available to identify sediment types and sediment exchanges with the offshore.

The Bristol Channel is an active interest area for marine aggregate extraction, with the majority of licenses falling in Welsh Territorial Waters. To enable the Government View procedure on marine aggregate extraction in this area to develop with a more complete understanding a research project (Bristol Channel Marine Aggregates: Resource and Constraints, also commonly referred to as BCMA) was commissioned. This research project identified Carmarthen Bay as a strategic unit of the overall sediment regime, and defined a programme of primary research in this area to improve understanding of sediment exchanges. A key part of this research has been an application of sediment trend analysis (STA). This paper describes components of the STA technique, the rationale for its application, the survey design, results and subsequent interpretation of the information in the context of determining probable patterns of net sediment transport across Carmarthen Bay.
A mixed ophiuroid—stylophoran assemblage (Echinodermata) from the Middle Ordovician (Llandeilian) of western Brittany, France
Authors: Hunter Aaron W. , Lefebvre Bertrand , Régnault Serge , Roussel Philippe , Claverie Roland
Published: December 2007

In the abandoned slate quarry of Guernanic, Gourin (Morbihan, France), a single horizon (Upper Member of the Schistes de Postolonnec Formation) has yielded an exquisitely preserved Llandeilian (Middle Ordovician) echinoderm assemblage composed of the ophiuroid
Taeniaster armoricanus
sp. nov. and the mitrate
Mitrocystella incipiens
. These two groups of echinoderms represent the first fossils formally described from the Middle Ordovician of the Gourin area. The brittlestar
T. armoricanus
sp. nov. is the third and oldest ophiuroid reported so far in the Palaeozoic of the Armorican Massif. The mitrate
Mitrocystella
is also described for the first time from western Brittany. Taphonomic features of this ophiuroid-stylophoran aggregation suggest that it probably corresponds to the rapid burial of a life assemblage in an otherwise quiet and moderately deep setting (shelf) below, but close to, storm wave base. This echinoderm association represents the oldest evidence for a gregarious mode of life for ophiuroids, as well as the oldest indisputable example of a mixed ophiuroid-stylophoran meadow.
Frasnian carbonate mounds from Belgium:sedimentology and palaeoceanography
Authors: Boulvain Frédéric
Published: December 2007

The facies architecture, sedimentary dynamics and palaeogeographic evolution were reconstructed for a number of middle-late Frasnian carbonate mounds from the south side of the Dinant Synclinorium (Belgium). Nine facies were recognized in the buildups, each characterized by a specific range of textures and assemblage of organisms: spiculitic wackestone with stromatactis (facies Pm1), which becomes progressively enriched in crinoids and corals (Pm2); grey or pinkish limestone with stromatactis, corals and stromatoporoids (A3–L3, Pm3); grey limestone with corals, peloids and dasycladales (A4–L4, Pm4); grey, microbial limestone (A5–L5, Pm5); grey limestone with dendroid stromatoporoids (A6–L6); grey, laminar fenestral limestone, (A7–L7); and grey, bioturbated limestone (A8–L8). Sedimentological evidence suggests that facies Pm1 and Pm2 correspond to iron bacteria-sponge-dominated communities, developing in a quiet aphotic and hypoxic environment. A3–L3 developed between storm and fair-weather wave base, in an oligophotic environment. Facies A5–L5 developed close to fair-weather wave base. Facies A6–L6 and the fenestral limestone A7–L7 correspond to an environment with slightly restricted water circulation. Facies A8–L8 developed at subtidal depths in a quiet, lagoonal environment. The main differences between the middle and late Frasnian mounds concern facies architecture, and are a consequence of different palaeoceanographic settings. The large flattened middle Frasnian Arche and Lion buildups show limited vertical differentiation, large-scale progradation features, extensive exportation of material towards off-reef environment and development of inner lagoonal facies. They grew offshore from a well-developed carbonate platform with a healthy carbonate factory. Middle Frasnian sea-level fluctuations were relatively mild, and sedimentation was able to keep up with sea-level rise. At the opposite extreme, during the late Frasnian, severe eustatic rises, together with rising oceanic hypoxic conditions, were responsible for frequent collapses of the carbonate factory, drowning of the middle Frasnian carbonate platform, and development of buildups with relatively limited lateral extension, high vertical facies differentiation, low potential for material exportation and high content in microaerophilic iron bacteria.
After the collapse of stromatoporid-coral reefs — the Famennian and Dinantian reefs of Belgium: much more than Waulsortian mounds
Authors: Aretz Markus , Chevaliers Emmanuel
Published: December 2007

Reef development in the Famennian and Carboniferous successions of Belgium is more common than previously thought, and 10 broad time intervals of reef development can be differentiated. Reef formation is due to a variety of reef fabrics. Microbial communities are important for most reef frameworks, and often crucial for formation and stabilization of frameworks. Larger skeletal frameworks are rare. However, the interaction of skeletal bioconstructors and microbial communities is common, and results in successful reef building. However, microbial communities are still the backbone of these reefs.

The majority of reefs are small, and a significant number formed in environments of restricted marine facies. Large reefs developed only in the late Tournaisian and late Visean. Their initiation and formation was controlled by the geometry of the shelf.

Three hierarchical levels, discussed below under the headings paleobiology, local environment, and regional and global environment, controlled reef formation. Important limiting factors were relative water depth, sea-level oscillations, climate, shelf geometry and the needs of the individual bioconstructor.

In general, Belgian reef diversity reflects the global picture, but significant differences can be recognized in the different time slices. In particular, the abundance of middle Visean reefs is a unique feature. The onset of the Variscian orogeny terminated all reef development in Belgium, and reefs younger than late Visean are unknown.
The late Atokan (Moscovian, Pennsylvanian) chaetetid accumulations of Sierra Agua Verde, Sonora (NW Mexico): composition, facies and palaeoenvironmental signals
Authors: Almazán-Vázquezi Emilio , Buitrón-Sánchez Blanca E. , Vachard Daniel , Mendoza-Madera Cynthia , Gómez-Espinosa Catalina
Published: December 2007

The La Joya Formation of the Sierra Agua Verde, Sonora (NW Mexico) is late Atokan in age, equivalent to the early late Moscovian (Podolskian) and fusulinid biozone A3. In this alternance of cherty limestones and thin shaly beds, fusulinellid or anchicodiacean (‘phylloid algae’) wackestones-packstones and crinoidal rudstones-grainstones are the predominant microfacies, but chaetetid boundstones are conspicuous. These chaetetid occurrences of the Sierra Agua Verde are compared with the accumulations of Arizona, Texas, Kansas and Nevada (USA), and the Cantabric Cordillera (Spain). In Sonora, the environments with chaetetids were quiet, and located below wave base. Shallower facies with staffellids and
Komia
generally top the chaetetids. Because of the associated micritic deposits, the chaetetids have inhabited probably a soft or firm substrate. As a result of the disphotic-aphotic reconstructed environments, the possible symbionts of the chaetetids are more probably heterotrophic bacteria than autotrophic algae. The most comparable ecological conditions exist in the Atokan Marble Falls Formation of central Texas (USA). Chaetetids are not mentioned in the southern suspect terranes of Mexico, but were possibly present because these regions were located along the probable migration way to Peru, the southernmost area where Pennsylvanian chaetetids are known.
Coelobiontic communities in neptunian fissures of synsedimentary tectonic origin in Permian reef, southern Urals, Russia
Authors: Vennin Emmanuelle
Published: December 2007

Sedimentary dykes in the Permian reef complexes of the Russian platform are well preserved and important in providing information about reef growth, the reef biota and, particularly, cavity-dwelling organisms and sediment sources. Two main fissure assemblages are recognized with N80° and N170° (late Asselian-early Sakmarian) and N130°–140° and N60° (Sakmarian-Artinskian) orientations. These contemporaneous orthogonal dyke sets present orientations corresponding to the regional tectonic fabric and a tectonic origin for fracturing associated with the foreland basin development. The largest dykes record eight lithofacies and several stages of fracture opening. Stromatoids and centimetre-thick deposits of peloidal grainstones-packstones (thromboids), which form
in situ
within microbial laminae on the fissure walls, preceded filling by skeletal and terrigenous sediments. The fissures contain a well-preserved biota similar to the Lower Permian cavity-dwelling organisms observed within the reef. The coelobiontic habitat was episodically enlarged by successive synsedimentary fracturing episodes reflecting several phases of encrustation and infill of recurrent lithofacies. The pioneer microbialites grew when nothing else was deposited in the fissures immediately after fracturing. Gastropods and ostracods occur as dense clusters, probably indicating
in situ
growth, or are considered as reworked material from the subsurface. Others organisms, such as crinoids, bryozoans,
Tubiphytes
, conodonts, brachiopods, ammonoids and spiculate sponges, are also found within fractures as reworked shells and skeletons, indicating that they were washed in from the overlying sea floor. The biota in the dykes is mainly represented by the dweller guilds living on the reef surface, whereas members of the binding and frame-building guilds are poorly represented. The dykes formed during reef development and the last stage of argillaceous wackestone sedimentation within the fractures is related to a major flooding event corresponding to upper Artinskian drowning of the Russian platform. Biostratigraphically significant fossils in the dykes date the ages of the host rock and of the fissure formation and filling from late Asselian to upper Artinskian. The Tratau reef thus provides an instructive example of the interaction between carbonate accumulation and tectonic events.
Late Permian limestones and the Permain-Triassic boundary:new biostratigraphic, palaeobiogeographical and geochemical data in Caucasus and eastern Europe
Authors: Théry J. M. , Vachard D. , Dransart E.
Published: December 2007

This paper presents biostratigraphical and palaeogeographical correlations, in a post-Hercynian and pre-Cimmerian tectonic framework, between stratigraphic sections of Late Permian age in two important and remote areas, with some considerations concerning neighbouring countries. It concerns mainly the Nikitin sequence (Kuban, Russia) and the Bükk Mountains (Hungary), and describes the carbonate environments, microfauna diversity, foraminiferal assemblages, calcisponge and brachiopod constructions, and gymnocodiacean accumulations. This study is extended to former Transcaucasia (southern Armenia, Georgia and Adzerbadjan), the Alborz Belt in northern Iran, Italy and the Carnic Alps. It emphasizes a relatively simple biosedimentary evolution, which permits a confident palaeogeographic reconstruction. New geochemical results provided some additional markers, in particular small microspherules consisting of Cr/Ni spinels of cosmic origin. They occur in several sections in a defined position at the Permian-Triassic boundary based on biostratigraphic correlations (conodonts, foraminifers, last Permian reefal phenomena). These geochemical data might be related to a possible meteorite impact, Nevertheless, another global alternative phenomenon occurs. From the Latest Permian to the Earliest Triassic, the carbonate production or biomineralization is preferentially concentrated in the confined, intertidal or lagunal zones, and its evolution is relatively progressive from gymnocodiacean accumulations of the Latest Permian to the microbialites of the Earliest Triassic.
Bottom-current reworked Palaeocene-Eocene deep-water reservoirs of the Campos Basin, Brazil
Authors: Moraes Marco A. S. , Maciel Walter B. , Braga Mario Sérgio S. , Viana Adriano R.
Published: December 2007

Deep-water reservoirs consisting of turbiditic sandstones moderately to heavily reworked by bottom currents are common in canyon- and trough-filling deep-water (bathyal) Palaeocene—Eocene sequences of the Campos Basin, offshore southeastern Brazil. A number of wells with conventional logs, together with cores, provided the database for the study. Seismic data provide additional support, but low resolution and noise hamper detailed analysis. The sandstones presenting better reservoir quality in these sequences are interpreted as being deposited by turbidity currents, as suggested by the dominance of unstratified normally graded sandstones, with grain sizes ranging from fine to coarse sand, and low clay-matrix content. Sandstones interpreted as bottom-current deposits (mid-water contourites) form poor-quality reservoirs, or baffles and barriers. These rocks are commonly moderately to heavily bioturbated, with variable, frequently high, clay-matrix content. Common trace fossils include
Planolites, Palaeophycus
and
Zoophycos
. Locally, these sandstones show faint horizontal stratification and planar cross-stratification. Contourites with thickness ranging from a few decimetres to several metres occur intercalated with turbiditic sandstones. Because they present distinct reservoir qualities, the mapping of the limits between turbidites and contourites is critical for adequate reservoir characterization. Most of this mapping has been performed using well information, constrained by outcrop analogues. The currents responsible for reworking turbiditic sands are interpreted to be deviated geostrophic currents, with velocity enhanced in narrow canyons and troughs.
Slope currents and contourites in an eastern boundary current regime: California Continental Borderland
Authors: Robinson Rebecca S. , Murillo de Nava Janette M. , Gorsline Donn S.
Published: December 2007

Analysis of piston cores from lower slopes of central and outer basins of the California Continental Borderland shows the presence of structures ranging from starved silt ripples and lenses to erosion surfaces and truncated burrows to cross-bedded units that testify to reworking of the sediments by bottom currents. Adjacent basin-floor piston cores do not reveal these structures, but exhibit the usual bioturbated hemipelagic mud and turbidites. Slope sediments generally contain more silt than the adjacent basin-floor clay silts. The slope grain-size distributions are multimodal as a result of mixing of hemipelagic mud and thin (millimetre scale) silt layers as a consequence of the sampling intervals at centimetre scale. Carbonate and organic carbon contents tend to be low during the glacial periods but variations from this pattern occur that are probably related to the shift in the upwelling associated with the California Counter Current between inter-glacial and glacial conditions. The evidence for reworking is most abundant from late in Marine Isotope Stage 5 (MIS 5) to early Stage 4 (MIS 4), and it decreases into the Holocene. No structures are observed in the Holocene sections of the slope cores. The temporal distribution of the reworking structures can be explained either by changes in the degree of bioturbation (bottom-water oxygenation), which would work to erase the structures, or variation in the intensity of lower slope circulation through time. The observed pattern is in rough agreement with documented changes in bottom-water oxygenation conditions for these basins. However, the occurrence of reworking is also dominantly within glacial intervals, where lower sea levels produce stronger circulation within the basins as a result of exposure of banks and resulting restriction of cross-sections of the deeper flow pathways. These observations add to the increasing evidence that sediment transport by bottom currents is not restricted to the intensively studied western boundary current drift deposits. The action of bottom currents on eastern boundary slopes can introduce subtle effects on what are commonly assumed to be continuous records.
Pelagic carbonate ooze reworked by bottom currents during Devonian approach of the continents Gondwana and Laurussia
Authors: Hüneke Heiko
Published: December 2007

Givetian and lower Frasnian carbonates of pelagic carbonate-platform and distal slope-apron settings in the Harz Mountains of Germany (Herzyn Limestone Formation), the eastern Moroccan Central Massif (Ziar-Mrirt Nappe), and the Carnic Alps in Austria-Italy (Valentin and Pal Limestone Formation) show strong evidence for bottom-current activity during deposition. Calcarenites, laminated calcisiltites, and mottled calcisiltites and calcilutites can be distinguished, which are similar to recent calcareous bioclastic contourites. They combine faint structures caused by current action with pervasive bioturbation. Calcarenites are mostly represented by styliolinid grainstones to packstones with rarely preserved parallel lamination and ripple cross-lamination. Laminated calcisiltites are particularly rich in non-carbonate components with a higher density than calcite such as conodonts and phosphatic intraclasts. Relics of coarsening-upward to fining-upward micro-sequences a few centimetres thick are preserved in the Moroccan record. Erosional surfaces, hardgrounds and condensed phosphates are more typical of the Harz Mountains and the Carnic Alps. The bottom-current influenced facies build up strongly condensed and reduced sequences that occur at the same stratigraphic interval in different areas of central Europe and NW Africa. Variations in rate of accumulation, magnitude of erosion and microfacies, which are found across the three regions, are compatible with a contourite interpretation. The widespread current-induced reworking of calcareous sediments and phosphate formation during the Givetian and early Frasnian as well as the associated erosion marked by pronounced hiatuses all signal a major palaeocirculation event. Thermohaline currents were intensified by the acceleration of flows constricted in narrow oceanic passages between the approaching continental plates Laurussia and Gondwana. Areas affected were the southeastern Rhenish Sea shelf, which occupied the distal passive margin of Laurussia, the disintegrated northern continental margin of Gondwana, whose sedimentary record is now preserved in the Moroccan Meseta, and deep marginal plateaux of the Noric Terrane in the western part of the Prototethys. Thus, the occurrence of fossil calcareous contourites confirms a very advanced convergence between Gondwana and Laurussia and the minor terranes between during Middle and Late Devonian times.
Hydrodynamic modelling of bottom currents and sediment transport in the Canyon São Tomé (Brazil)
Authors: Lima José A. M. , Moller Osmar O. , Viana Adriano R. , Piovesan Rafael
Published: December 2007

This study presents the hydrodynamic modelling of ocean currents along the Canyon São Tomé, Campos Basin, Brazil, and their impact on sediment transport. The objective is to develop a tool to simulate the interaction between bottom currents and the submarine physiography, and to depict the relative importance of any individual current forcing mechanism as a sediment-reworking agent. This paper presents the evolution of along-channel currents over a tidal cycle and the simulation of a turbidity current. The resultant sediment transport under the combination of turbidity and oceanic currents is also simulated. This model is a step forward towards the understanding of the geometric and textural modifications imposed by bottom currents upon gravity-driven deposits, which is of great importance for the oil industry.
Pros and cons of a group webpage design project in a freshman anatomy and physiology course
Authors: Crisp Kevin M. , Jensen Murray , Moore Randy
Published: December 2007

To generate motivation and promote the development of written communication skills, students in a freshman-level anatomy and physiology course for nonmajors created group webpages describing historically important diseases. After the groups had been formed, each individual was assigned specific components of the disease (e.g., causes or treatments), which were subsequently combined into a final product. Interviews and questionnaires were used to document students' previous educational experiences regarding, and attitudes toward, the project. Students learned more about website design than about anatomy and physiology, but students preferred the assignment over traditional term papers. Although most students could find relevant information for this project on the internet, they were uncritical in judging the accuracy of the information they found.