bluuebunny/crossref_metadata_2025 huggingface dataset:
The mineralogical and chemical methods in investigations of decay of the Devonian black ‘marble’ from Debnik (Southern Poland)
Authors: Marszałek M.
Published: December 2007

Optical microscopy, scanning electron microscopy with energy dispersive spectrometry, X-ray diffraction, infrared (IR) spectroscopy, Rock-Eval pyrolysis and gas chromatography combined with mass spectroscopy were used to examine deterioration of the black limestone from Dębnik near Cracow. Owing to its unique colour and good polishing properties the rock is called the ‘Debnik marble’. The samples were taken from various monuments and natural outcrops exposed to weathering. The material is a compact limestone whose black colour is caused by an admixture of bitumens or pyrite. Its horizontal layers are separated by discontinuities filled with clay minerals. Surface exfoliation is one of the damage signs and results in the formation of irregular or lensoidal fractures. The discontinuities provide an easy access for acid rain that in reaction with calcite produces gypsum.

Crystallization of gypsum leads to alveolar weathering, cracking and chipping of the otherwise compact material. The presence of alveoles or surface exfoliation depends on the orientation of stone blocks. When they are cut along the discontinuities, destruction results in exfoliating and cracking. Perpendicular cutting gives rise to the formation of alveoles. The changes affect the original black colour of the stone surface that alters to grey or even white.
Modelling of the calcareous stone sulphation in polluted atmosphere after exposure in the field
Authors: Lefèvre R.-A. , Ionescu A. , Ausset P. , Chabas A. , Girardet F. , Vince F.
Published: December 2007

Parisian Lutetian and Val-de-Loire Turonian Richemont limestone tablets were exposed, sheltered and unsheltered from rain, for up to 3 years in Paris and Tours, respectively. Sulphur concentrations below the stone surfaces were measured from powders obtained by milling the stone in successive steps of 0.1 mm. In tablets exposed to rain, measured sulphur concentration remains equal to the stone background concentration, implying that the sulphur deposited between rain events is leached by the next event. In contrast, in tablets sheltered from rain, the sulphur concentration in the first layer below the stone surface increases non-linearly with time. Sulphation does not, however, penetrate more than 0.2 mm. A sigmoidal Hill curve provides a good fit with changes in measured sulphur concentration over time within the first layer of each sheltered stone. This model reveals a cumulative phenomenon of sulphation, characterized by a saturation level that obstructs deeper penetration of sulphur within the stone. The model shows the same type of time evolution of sulphation for both stones, but with different coefficients; these coefficients are related to the atmospheric environment of exposure and to the different intrinsic properties of each stone.
Decay of natural stones caused by fire damage
Authors: Sippel J. , Siegesmund S. , Weiss T. , Nitsch K.-H. , Korzen M.
Published: December 2007

Almost every representative ancient building suffered from a fire during its history. Therefore, several limestones, sandstones, a gypsum, granites, tuffs, an orthogneiss and two marbles have been tested to analyse the effect of fire. Thermal expansion measurements up to 1000 °C reveal that every rock shows a specific expansion behaviour. Variations are caused by the single crystal thermal expansion properties of rock-forming minerals and by different damage processes. In silicate rocks, intragranular fracturing is the predominant damage phenomenon. Carbonate rocks show, at low temperatures, a behaviour mainly controlled by the anisotropic expansion of calcite. At higher temperatures, mineral reactions, such as decarbonatization, are directly evidenced by sudden jumps in thermal expansion curves. If water is present, a second stage of deterioration follows fire damage: the huge volume increase due to portlandite formation from decarbonized CaO causes severe scaling at the outermost surface of limestone when exposed to the environment. Small amounts of silicates in carbonate rocks may improve the stability of those rocks due to dicalciumsilicate formation. At high temperatures, an increase in the expansion coefficient may be explained by partial melting for some rock types. Phase changes (e.g. quartz) are monitored by a sudden increase in the expansion coefficient. Investigations on gypsum reveal that dehydration reactions reduce fire temperatures in the vicinity of gypsum rocks significantly. In general, all experiments show that samples are severely damaged after being subjected to fire. Real fire tests show that the penetration depth of heat and the associated damage types vary as a function of lithology. While for granites, cracks in feldspars predominate, the firing of limestone causes a scaling of the outermost layer. The investigations may lead to an improved assessment of natural building stones that have been damaged by fire. Implications can also be drawn for the recent use of facade panels made of natural building stones in case of a future fire.
The effects of wetting and drying, and marine salt crystallization on calcarenite rocks used as building material in historic monuments
Authors: Andriani G. F. , Walsh N.
Published: December 2007

The results of a study of the effect of marine salt crystallization on the physical and mechanical properties of Plio-Pleistocene calcarenites cropping out in southern Italy are presented here. Owing to their workability, aesthetic appeal and availability, the calcarenites have been widely used as building stones in many historic monuments. Samples of medium-grained packstones and fine-grained packstones-wackestones were prepared for the salt crystallization test defined by EN 12370, using sea water instead of a 14% solution of Na
2
SO
4
· 10H
2
O. To determine the effect of imbibition alone on the performance of the calcarenites, the same procedure was followed with distilled water without soluble salts. Microfabric analysis, evaluation of index parameters and grain-size distribution were carried out as well. Particular attention was given to pore-size distribution by mercury intrusion porosimetry (MIP), loss of weight and uniaxial compressive strength determined before and after the tests, and after every five cycles of complete immersion in sea water and distilled water. The results suggest that detailed information on fabric and pore network are indispensable to predicting the weatherability of rocks. Crystallization tests that involve the complete immersion of the samples in a saline solution are not effective for an understanding of the real importance of salt damage on soft and porous calcarenites owing to a significant incidence of imbibition in accelerating deterioration rates and in influencing patterns and intensity of weathering.
Length changes of sandstones caused by salt crystallization
Authors: Ruedrich J. , Seidel M. , Rothert E. , Siegesmund S.
Published: December 2007

Salt crystallization in the pore spaces of building stones can produce significant deterioration. The properties of the salt solution, the salt phases and the climatic conditions, as well as the rock fabric, significantly influence the state of rock weathering. To examine the influences of rock fabric and salt type on salt weathering, detailed investigations were performed on three sandstones. The fabric (mineralogical composition, grain size, etc.) and the petrophysical properties (porosity, pore-size distribution and hygric dilatation) of the sandstones were analysed and correlated with length changes during cyclic salt loading. The salt tests were carried out with two different salt types: (i) sodium sulphate and (ii) sodium chloride. The observed length changes differ for the investigated sandstones. Contractions of the samples, as well as a pronounced residual strain after the applied salt cycles, were observed. Specific deterioration features can be determined for the sandstones independent from the salt types used. However, the decay mechanisms, which lead to a significant deterioration, are different for sodium sulphate and sodium chloride. For sodium sulphate, a strong expansion occurs during the solution uptake cycles. This expansion can be attributed to hydration pressure during the transition from the water-free thenardite to the hydrate phase mirabilite. In contrast, the samples in the sodium chloride test show the main expansion in the drying stage. This can be related to the crystallization pressure caused by the growth of halite.
Complex weathering effects on durability characteristics of building stone
Authors: Warke P. A. , Smith B. J.
Published: December 2007

Durability characteristics of five stone types are assessed and compared using the standardized sodium sulphate salt crystallization test and a modified laboratory weathering simulation in which a combination of salt weathering (Na
2
SO
4
) and freeze-thaw cycles are used. Data indicate significant differences in durability rankings between the two test methods especially in lower-order durability stone types. Both the standard salt crystallization test and the modified durability test identify Leinster Granite and Stanton Moor B Sandstone as the most durable of the five stone types, with the granite performing well under both sets of conditions. Discrepancy between rankings arises in the lower orders, with Portland Limestone, Stanton Moor A Sandstone and especially Dumfries Sandstone responding differently to the two sets of experimental conditions. In the modified durability test the range of permeability values for each stone type produced the same ranking as that indicated by mean percentage weight change values but mean permeability values for each stone type do not appear to be reliable predictors of weathering response. Differences in durability rankings between the two test regimes are attributed in the first instance to the temperature conditions used, with more extreme and unrealistic heating to 103 °C in the standardized test ‘over-weathering’ stone while conditions in the modified test allowed the development of stone-specific decay characteristics. Inclusion of salt weathering and freeze-thaw cycles in the modified test introduced complexity into the decay process that more accurately reflects ‘real-world’ conditions. Data also indicate that relatively minor structural and mineralogical differences between samples of the same stone type can significantly influence weathering behaviour, resulting in distinct rates and patterns of breakdown.
Texture, spatial and orientation dependence of internal strains in marble: a key to understanding the bowing of marble panels?
Authors: Scheffzük Ch. , Siegesmund S. , Nikolayev D. I. , Hoffmann A.
Published: December 2007

A Carrara marble sample was measured using neutron time-of-flight diffraction on its crystallographic preferred orientation (texture), a strain scan through the sample and strain pole figures to explain the effect of deformation of marble plates. Strong compressional residual strain values of up to ɛ = -1.3 × 10
-3
measured with residual strain pole figures in a virgin bulk sample have been found. Obviously, the magnitude of residual strain depends on the sample size. Features of the observed texture pole figures and internal strain pole figures are related to each other by their sample orientations. Texture and residual strain measurements were combined with investigations of thermal expansions under dry and wet conditions in different directions to the main stress direction.
The influence of lithology and pore-size distribution on the durability of acid volcanic tuffs, Hungary
Authors: Török Á. , Forgó L. Z. , Vogt T. , Löbens S. , Siegesmund S. , Weiss T.
Published: December 2007

Eight different types of acid tuffs of the Eger Castle (Hungary) and two tuffs from nearby quarries have been studied in detail. Mapping of wall sections reveals that tuffs show weathering forms that are similar to common sedimentary rocks, such as limestones or sandstones. Different lithologies display various weathering features. On pumice-rich tuff ashlars relief due to selective weathering, weathering crusts, multiple flakes and scales occur, while crumbling is common on layered flow tuffs. Conversely, cemented tuff types do not show deep weathering. Pore-size distribution rather than effective porosity controls the weathering susceptibility of tuffs. Frequent larger micropores are the main causes of freeze-thaw-related weathering. Besides clays, newly formed gypsum and calcite are the weathering-related index minerals. Schmidt hammer rebound values mark the weathering process when quarry stones and ashlars of historic walls are compared.
Differences in texture, physical properties and microbiology of weathering crust and host rock: a case study of the porous limestone of Budapest (Hungary)
Authors: Török Á. , Siegesmund S. , Müller C. , Hüpers A. , Hoppert M. , Weiss T.
Published: December 2007

Ashlars of the Parliament building and Citadella fortress made of three porous Miocene limestones, a fine-grained limestone, a medium-grained oolitic limestone and a coarse-grained bioclastic limestone, were studied and compared with quarry blocks of the same lithologies. The commonest weathering forms are white (thin and thick) and black (laminar and framboidal) crusts. To assess the processes of crust formation and detachment, descriptions of lithologies and associated weathering features were combined with micro-drilling, pore-size distribution and ultrasonic pulse velocity tests. Microbiological and textural analyses were also performed. The micro-drilling resistance measurements and ultrasonic pulse velocities clearly document the presence of crusts and the degradation of underlying fine- and medium-grained limestones. A textural change, with calcite recrystallization, is also marked by pore occlusion and reduction of microporosity in the crust zone. Crust detachment is initiated by the opening up of microfissures that develop below the cemented crust zones. Fine-grained limestone appears to be less durable than the coarse-grained variety and more prone to rapid crust formation and detachment. Ashlars from where the crusts were removed have lower micro-drilling resistance compared to quarry stones. Microbiological activity appears to play an insignificant role in crust formation and removal. Indeed, the combined effect of air pollution and related gypsum crystallization and more probably freeze-thaw weathering activity lead to crust detachment with rates strongly controlled by the texture and porosity of the limestone substrate.
A comparative and critical study of X-ray CT and neutron CT as non-destructive material evaluation techniques
Authors: Vlassenbroeck J. , Cnudde V. , Masschaele B. , Dierick M. , van Hoorebeke L. , Jacobs P.
Published: December 2007

X-ray computerized tomography (CT) has traditionally been used as a medical diagnostic tool. This non-destructive technique has developed as an important research tool for a wide variety of scientific subjects. For material research ‘medical’ CT, microCT and, very recently, nano- or submicroCT have been used as non-destructive material evaluation techniques for engineering and geological purposes. The fact that X-ray CT visualizes the internal structure of natural building stones and yields information on porosity values and pore-size distributions is a major advantage for the study of their conservation. The penetration of fluids like water, consolidants or water repellents inside porous materials is important when dealing with conservation and restoration research. Recently, high-speed neutron tomography has been introduced as a visualization technique for fluids inside porous materials. High-speed neutron tomography can be used as a complementary technique to X-ray tomography as elements like hydrogen, which have a weak attenuation for X-rays, are easy to detect using neutrons. In this paper the basic principles of computerized tomography and more specifically X-ray and neutron tomography are discussed. In addition, application possibilities, advantages and limitations of medical CT, X-ray microCT and high-speed thermal neutron CT are outlined.
Rock petrophysics v. performance of protective and consolidation treatments: the case of Mt Arzolo Sandstone
Authors: Carò F. , Di Giulio A.
Published: December 2007

The petrophysical characteristics of a building stone used in the city of Pavia, northern Italy, are analysed in the light of stone conservation through the application of water repellent and consolidant products. The research focuses on the modification of petrophysical properties as a function of the applied products, and on the critical assessment of the performances of fluorinated and siloxane resins as a function of the variable nature of the same lithotype. The studied material is a calcareous sandstone (Mt Arzolo Sandstone), Late Miocene-Early Pliocene in age, extensively employed as a building material during the 11th and 12th centuries. Experimental investigations on samples from historic quarries were performed before and after application of treatments: i.e. petrographical and fabric analyses; ultrasonic measurements; mercury porosimetry; abrasion resistance measurements; contact angle measurements; capillary and low-pressure water absorptions; water vapour permeability; and colour measurements. Two main lithotypes of Mt Arzolo Sandstone were recognized according to their petrophysical features: the open porosity being similar, differences exist concerning their fabric. These differences influence the physical-mechanical properties of the material and consequently the performances of the applied products. In particular, the difficulties in penetration of products when sandstone of smaller pore size is treated can lead to a significant reduction of the overall performances, which is more evident for products containing organic solvent with high molecular weight.
Genesis Chapter 1 and geological time from Hugo Grotius and Marin Mersenne to William Conybeare and Thomas Chalmers (1620–1825)
Authors: Roberts Michael B.
Published: December 2007

In 1550 few questioned the ‘biblical’ age of the earth, but by the mid-nineteenth century no educated person accepted it. The change is considered to have been a period of conflict between Christianity and science over the age of the earth. In fact, the conflict was small because from the Reformation era most considered the bible to be accommodated to its culture and that at the beginning of time God created a Chaos, which was re-constituted in ‘six days’. This was put forward by Grotius and Mersenne. then by the
Theories of the Earth
of Burnet. Whiston and others and then by later writers to allow for geological time. This reached its climax in early nineteenth century Britain with Chalmers. Conybeare and Buckland, thus preventing any major conflict between geology and Genesis. The perceived conflict of these centuries is a matter of retrospective interpretation, which does not do justice to those Christian thinkers, like de Luc, Chalmers and Townsend who accommodated geological time with little conflict, and those like Patrick, Ray and Whiston who opened up the way for this accommodation to geological time in the seventeenth century. The conflict between geology and Genesis is one of retrospective perception rather than historical reality. Only a minority of Christians, as with the anti- or scriptural geologists of the early nineteenth century, considered there to be a conflict.
Writing on the walls: geological context and early American spiritual beliefs
Authors: Hough Susan E.
Published: December 2007

Native American culture in many parts of California is preserved in fragmentary oral and conventional written histories, but also in sometimes dramatic petroglyphs and pictographs throughout the state. The symbolism of these images has been interpreted to reflect the natural environment, in particular issues related to rain. Although there is little doubt that rain was of paramount concern to native tribes, I suggest that geological context also played an important role in shaping early spiritual beliefs in general, and petroglyph sites in particular. From the standpoint of Native American philosophies and spiritual beliefs, geological unrest is not merely a reflection but in some cases an actual embodiment of the spiritual world. To understand the significance of petroglyph sites, they must be considered in the context of overall Native American beliefs. In this context, sites of repeated geological unrest would invariably have evolved great spiritual significance. Petroglyph locations and ages may thus provide independent age controls on ‘prehistoric’ earthquakes in California.
The Bible and geology: destruction of Sodom and Gomorrah
Authors: Trifonov Vladimir G.
Published: December 2007

The biblical story of the destruction of Sodom and Gomorrah is interpeted as a reflection of a real natural disaster. According to the Bible. Sodom and Gomorrah were situated near the southern part of the Dead Sea basin or in the Jordan River valley. The description of their destruction in the Bible can be interpreted only as volcanic eruption. Evidence of middle Holocene volcanism is absent both in the Dead Sea and Jordan River regions, but has been found in the Neogene—Quaternary lava highland in the southern Syria. At two settlements, Khirbet El-Umbashi and Hebariye, dated around the second part of the third millennium
bc
, many animal bones were covered by the basaltic lava. It is possible that, the Bible's story of the destruction of Sodom and Gomorrah combined collective memories about two events. Located in the Dead Sea region, Sodom and Gomorrah were most probably destroyed by a strong earthquake or flood, but the fresh memory about two settlements perishing from a volcanic eruption caused the population to merge these two events.
Myth and catastrophic reality: using myth to identify cosmic impacts and massive Plinian eruptions in Holocene South America
Authors: Masse W. Bruce , Masse Michael J.
Published: December 2007

Major natural catastrophes such as floods, fire, darkness, and ‘sky falling down’ are prominently reflected in traditional South American creation myths, cosmology, religion, and worldview. Cosmogonic myths represent a rich and largely untapped data set concerning the most dramatic natural events and processes experienced by cultural groups during the past several thousand years. Observational details regarding specific catastrophes are encoded in myth storylines, typically cast in terms of supernatural characters and actions. Not only are the myths amenable to scientific analysis, some sets of myths encode multiple catastrophes in meaningful relative chronological order. The present study considers 4259 myths, including 284 ‘universal’ (perceived in the narratives to be worldwide) catastrophe myths, from 20 cultural groups east of the Andes. These myths are examined in light of available geological, palaeoenvironmental, archaeological, and documentary evidence. Our analysis reveals three likely major Plinian volcanic eruptions in Columbia and the Gran Chaco. We also identify a set of traditions that are probably linked to the well-known Campo del Cielo iron meteorite impact in northern Argentina around 4000 years ago, along with a separate set of traditions alluding to a possible airburst in the Brazilian Highlands. These impacts apparantly triggered widespread mass fires. There are hints of cosmic impacts in the mythologies for other locations in South America.
Meteorite records in the ancient Greek and Latin literature: between history and myth
Authors: D'Orazio Massimo
Published: December 2007

A catalogue of citations related to possible meteorites has been assembled by searching the ancient Greek and Latin literature up to the end of the West Roman Empire (
ad
476). The catalogue illustrates the attitude of ancient populations towards the fall of meteorites and extends the record of meteorite falls back in time. The citations are arranged in the catalogue as: i) ‘meteorite falls’, when both the locality and the date of the fall are, at least approximately, indicated; ii) ‘worshipped stones’, when the written and archaeological sources suggest the actual existence of a stone as an object of worship, but the information about the locality and the date of the fall are missing or vague; iii) ‘myths’, when the connexion between an object said to have fallen from the heaven and the fall of a meteorite is weak or obscured by mythological traditions.
Place names describing fossils in oral traditions
Authors: Mayor Adrienne
Published: December 2007

Folk explanations of notable geological features, including fossils, are found around the world. Observations of fossil exposures (bones, footprints, etc.) led to place names for rivers, mountains, valleys, mounds, caves, springs, tracks, and other geological and palaeontological sites. Some names describe prehistoric remains and/or refer to traditional interpretations of fossils. This paper presents case studies of fossil-related place names in ancient and modern Europe and China, and Native American examples in Canada, the United States, and Mexico. Evidence for the earliest known fossil-related place names comes from ancient Greco-Roman and Chinese literature. The earliest documented fossil-related place name in the New World was preserved in a written text by the Spanish in the sixteenth century. In many instances, fossil geonames are purely descriptive; in others, however, the mythology about a specific fossil locality survives along with the name: in still other cases the geomythology is suggested by recorded traditions about similar palaeontological phenomena. The antiquity and continuity of some fossil-related place names shows that people had observed and speculated about mineralized traces of extinct life forms long before modern scientific investigations. Traditional place names can reveal heretofore unknown geomyths as well as new geologically-important sites.
Shepherds' crowns, fairy loaves and thunderstones: the mythology of fossil echinoids in England
Authors: McNamara Kenneth J.
Published: December 2007

The presence of fossil echinoids in archaeological sites in southern England that range from the Palaeolithic through the Neolithic, Bronze and Iron Ages, Romano-British to Anglo-Saxon indicates that humans have long had a propensity for collecting these fossils. The palaeo-ethnological significance of fossil echinoids can be determined from a number of criteria. The fossils may occur with the dead, either in burials or cremations, or be associated with past activities of the living. These include presence on a flint worked as a tool; artificial alteration of the fossil; association with human habitation; or occurrence outside the area of natural geological occurrence. Their archaeological association provides an indication that these fossils have been collected by people for hundreds of thousands of years and, at times, attained a high degree of spiritual significance. Moreover, recent folklore associated with them, particularly their folk names, such as shepherd's crowns, fairy loaves and thunderstones, provides a further insight into the myths that were associated with them. These indicate the use of fossil echinoids in both ‘Celtic’ and Norse mythologies where they played a role in resurrection myths. The occurrence of fossil echinoids in a medieval church is indicative of retention of ‘pagan’ belief systems in a Christian context.
Obsidian: sacred glass from the California sky
Authors: Fox Hodgson Susan
Published: December 2007

For at least 13 000 years, California Indians mined and worked obsidian, trading the precious volcanic glass near and far, including obsidian and its uses in their everyday lives and beliefs. The cultural importance of obsidian is emphasized by the fact that a number of tribal groups created myths specifically about obsidian. Not only do the myths illustrate tribal religious beliefs, they help to trace geological and archaeological histories, as well. That obsidian still plays economic, artistic, and religious roles in the lives of today's Californians offers testimony to its qualities the Indians discovered long ago.
Erratic blocks: from protector beings to geosites to be protected
Authors: Motta Luigi , Motta Michele
Published: December 2007

Erratic blocks are the main geosites in Turin's suburban area. Today, they are a symbol of the ‘landscape to be saved’ even for those who are barely aware of their geological importance. This is because the blocks are the subject of myths (based on their geomorphological characters), such as: interpretation of weathering as altars or runic writing: attribution of strange shapes, noises, lairs, to petrified supernatural beings: interpretation of isolated blocks as dwellings of protector beings; use of the blocks for boulders: supposed reports of UFOs and ‘disappeared civilizations’. In ancient times, erratic blocks were at the centre of religious practices. However, most myths are in fact recent. The Barbarian invasions and the fight against Paganism destroyed the ancient myths. The creation of new myths proves that erratic blocks are able to attract mankind's attention in every epoch. When the geologist proposes blocks as protected geosites, he must show the connection between geomorphology and myths, maintaining the suggestive impact of the myths. Myths, including recent and altered ones, can work together with scientific explanation to make it easier for the public to understand the true importance of erratic blocks. By exploiting the power and appeal of myth, the community will more easily accept the need to preserve scientifically valuable geosites.
The contribution of the ‘Sibilla Appenninica’ legend to karst knowledge in the Sibillini Mountains (Central Apennines, Italy)
Authors: Aringoli D. , Gentili B. , Pambianchi G. , Piscitelli A. M.
Published: December 2007

Geological studies of the Sibillini Mountains carried out mainly during the last century, provided evidence of a hypogeal karst characterized by a small number of caves of limited extent. The only one mentioned by numerous ancient authors is the ‘Grotta della Sibilla’, on account of its legendary references. This cave is the keeper of one of the most fascinating secrets of the Apennines, having been both a place of mountain cult as far back as pre-historical times and the home of the fortune-telling prophetess ‘Sibilla’. Historical sources tell of the presence of someone mysterious at the site from the time of the Romans but amongst the historical descriptions, the testimony of Antoine de la Sale is most notable: he visited the cave in 1420 and described it as a good-sized cavity within the bowels of the mountain. Nothing about this setting is mentioned in the geological literature or in topographic descriptions, made for the first time at the beginning of the 1940s, when a regular but small cave was revealed. Today rockfall deposits completely obstruct the entrance.

On the basis of the above-mentioned legendary references, geomorphological and geophysical studies started helping to define the real extent of the cave. The planimetric trend of the electromagnetic anomalies surveyed allow us to make hypotheses about the presence of a vast hypogeal system.
Measuring suspended sand concentration using acoustic backscatter: a critical look at the errors and uncertainties
Authors: Vincent Chris E.
Published: December 2007

Suspended sand concentrations in the near-bed layer of the sea can be estimated using acoustic backscatter systems (ABS) and hence, when combined with velocity, sand transport. ABS measurements are now relatively routine and widely regarded as one of the best tools to help to measure sand transport in coastal seas and estuaries. Potentially the ABS can be used to give estimates of both concentration and sediment size with a vertical resolution of 5–10 mm and a temporal resolution of fractions of a second, but in practice there are many practical limitations to what can be achieved in the field. Often these uncertainties are overlooked or ignored because of the difficulty in estimating their magnitude or of making measurements that are any better. The major limitations and sources of errors in the ABS are discussed, including the influence of sediment size and shape. In moderately to well-sorted sandy environments with appropriate calibration, acoustic estimates of mass concentration should be within ± 30% of the true value.
Field measurement and quantification of longshore sediment transport: an unattainable goal?
Authors: Cooper J. A. G. , Pilkey O. H.
Published: December 2007

Longshore sediment transport (LST) is an important component of many coastal systems. This common term is frequently expressed as an annual volume, either net or gross, passing a particular point. In spite of its importance as a factor in coastal morphodynamics it has received relatively little attention as a process. We review the mechanisms of longshore sediment transport and current approaches to its assessment using field measurement and geoindicators. We conclude that approaches to date have never succeeded in quantifying longshore sediment drift rates in an adequate way. This shortcoming is attributed to the spatial and temporal variability of contributing processes coupled with a technical inability to quantify simultaneously longshore sediment transport in all its modes. We also conclude that research involving the measurement of longshore transport can enhance our understanding of the processes of transport and rates of transport under certain conditions. However, the accurate quantification of drift rates as annual volumes is an unattainable goal. We propose that such quantifications be replaced by qualitative values (small, medium, large) or measures of the relative importance of longshore transport in effecting morphological change (e.g. drift-dominated, cross-shore dominated, mixed processes).
Simple analytical results for bedload transport due to tides
Authors: Aldridge John N.
Published: December 2007

Patterns of sediment erosion and deposition arising from tide induced bedload transport are explored using standard bedload formulae and a simple analytic approach. Decomposing the current into a principal
M
2
tidal constituent, an
M
4
first harmonic and a tidal residual, it is straightforward to derive an expression for the contribution each makes to the integrated tidal flux. The resulting expressions are applied to calculate the net change in bed level induced by bedload transport due to a superposition of a Kelvin tidal wave, a harmonic overtide and a residual tide.
Shoreface morphodynamics along the Holland Coast
Authors: Hinton C. L. , Nicholls R. J.
Published: December 2007

The morphodynamic behaviour of the shoreface of the Holland coast has been investigated over the medium- and large-scales (years to decades). This is a wave-dominated, uniform coastline backed by dunes and uninterrupted by tidal inlets. The work takes a data-orientated approach using the ‘long’ profiles in a data set extending over 32 years and covering 81 km of coast. These profiles are spaced every 1 km alongshore and extend to a maximum offshore distance of 3 km (approximately 16 m water depth).

Previous work based upon cross-shore profiles suggests that there is a seaward limit to significant depth change, or activity, on the upper shoreface over the small- and medium-scales (termed ‘depth of closure’). Examination of the data set shows that the middle and lower shoreface is also morphologically active in many instances, with the activity increasing with timescale. Many profiles exhibit closure on the upper shoreface, and then reopen on the middle/lower shoreface, exhibiting morphological activity. This deeper shoreface morphodynamics appears to be related to onshore supply of sand to the active zone. Hence, the analysis shows that the upper, middle and lower shoreface are coupled, as widely assumed, and has widespread significance for understanding long-term coastal evolution.
Seabed sediment transport pathway investigations: review of scientific approach and methodologies
Authors: Velegrakis A. F. , Collins M. B. , Bastos A. C. , Paphitis D. , Brampton A.
Published: December 2007

An understanding of the geomorphological evolution of the coastal and inner continental shelf environments, in response to natural and/or anthropogenic forcings, depends upon a comprehensive knowledge of the prevailing sediment dynamics. In this contribution, selected methods/tools that can be used to study seabed mobility/transport patterns, are described and these all reviewed in relation to their inherent limitations.

The geological, morphological, hydrodynamic and sedimentary information (the environmental framework) necessary to develop a general understanding of the areas investigated are identified. This preliminary information prescribes the investigative tools to be utilized subsequently, i.e. the collection/analysis of data; these can define geomorphological and sedimentological indicators of sediment transport, hydrodynamic/sediment transport field observations and numerical simulations.

The results derived from the various methods can be used then independently or, preferably in combination, to establish conceptual models of seabed sediment dynamics over the investigated area. The coherence between the outputs of the different methods/tools controls the confidence level (high, medium or low) of the models. This approach is illustrated in relation to case studies from the southern UK inner continental shelf.
Fabric transitions from shell accumulations to reefs: an introduction with Palaeozoic examples
Authors: Álvaro J. Javier , Aretz Markus , Boulvain Frédéric , Munnecke Axel , Vachard Daniel , Vennin Emmanuelle
Published: December 2007

One unresolved conceptual problem in some Palaeozoic sedimentary strata is the boundary between the concepts of ‘shell concentration’ and ‘reef’. In fact, numerous bioclastic strata are transitional coquina-reef deposits, because either distinct frame-building skeletons are not commonly preserved in growth position, or skeletal remains are episodically encrusted by ‘stabilizer’ (reef-like) organisms, such as calcareous and problematic algae, encrusting microbes, bryozoans, foraminifers and sponges. The term ‘parabiostrome’, coined by Kershaw, can be used to describe some stratiform bioclastic deposits formed through the growth and destruction, by fair-weather wave and storm wave action, of meadows and carpets bearing frame-building (archaeocyaths, bryozoans, corals, stromatoporoids, etc.) and/or epibenthic, non-frame-building (e.g. pelmatozoan echinoderms, spiculate sponges and many brachiopods) organisms.

This paper documents six Palaeozoic examples of stabilized coquinas leading to (pseudo)reef frameworks. Some of them formed by storm processes (generating reef soles, aborted reefs or being part of mounds) on ramps and shelves and were consolidated by either encrusting organisms or early diagenesic processes, whereas others, bioclastic-dominated shoals in barrier shelves, were episodically stabilized by encrusting organisms, indicating distinct episodes in which shoals ceased their lateral migration.
Lower Cambrian shelled phosphorites from the northern Montagne Noire, France
Authors: Clausen Sébastien , Álvaro J. Javier
Published: December 2007

Shelled phosphorites of Early Cambrian age are common in the Avène-Mendic autochthonous unit (Marcory Formation) and the Melagues nappe (‘
Heraultia
beds’ of the Lastours Formation), northern Montagne Noire (France). Palaeogeographically, the concentration of phosphate took place along the shelf edge between a stable inner platform (southern Montagne Noire) and an unstable slope-to-basin sea floor preserved in the northern Montagne Noire. Petrography, back-scattered SEM (scanning election microscopy) and elemental mapping by EDS (energy dispersive system) show that the phosphorites were generated by repeated alternations of low sedimentation rates and condensation forming hardgrounds,
in situ
early diagenetic phosphogenesis, winnowing and polyphase reworking of previously phosphatized skeletons and hardground-derived clasts. The succession of repeated cycles of sedimentation, phosphate concentration and reworking led to multi event phosphate deposits rich in allochthonous particles. Associated accumulations of exhumed and reworked pyrite clasts reflect final deposition in a mainly dysaerobic substrate.
Anatomy of the Early Cambrian ‘La Sentinella’ reef complex, Serra Scoris, SW Sardinia, Italy
Authors: Gandin Anna , Debrenne FranÇoise , Debrenne Max
Published: December 2007

All bioherms from the Early Cambrian (Botoman) Matoppa Formation of the Nebida Group in SW Sardinia were previously thought to be dominated by
Epiphyton
. However, at ‘La Sentinella’ (Serra Scoris Hill), they are composed of
Girvanella, Razumovskia, Botomaella
and
Renalcis
, with
Epiphyton
and archaeocyaths as accessory components. This association forms two unusual types of crust boundstone, consisting of stacked flat or curved crusts and saucer-like archaeocyaths delimiting shelter cavities. Dendrolitic
Renalcis
archaeocyath-cement boundstone caps the bioherm. Analysis of the La Sentinella reef complex and comparison with similar constructions from Mongolia (Zuune Arts, Salaany Gol), Nevada (Stewart's Mill, Battle Mountain), Mexico (Sonora) and China (Tianheban Formation) suggest that episodic deposition of fine-grained siliciclastic or carbonate sediment followed by periods of non-deposition enabled the calcimicrobial rafts and crusts to colonize the substrate and then provide synoptic relief for the development of a dendrolitic
Renalcis
-cement framework. ‘La Sentinella’ is one of the rare examples of Cambrian reef complex displaying community replacement, from an initial stage of thrombolitic and/or flat-stacked microbial crusts on a muddy substrate to an arched microbial crust system, to a more resistant
Renalcis
-cement boundstone. Such bioherms reflect an open-shelf, shallow-marine environment of increasing energy.
Botoman (Lower Cambrian) turbid- and clear-water reefs and associated environments from the High Atlas, Morocco
Authors: Álvaro J. Javier , Clausen Sébastien
Published: December 2007

Exposures of the Botoman (Lower Cambrian), Lemdad and Issafen formations on the Lemdad syndine, southern High Atlas, provide an excellent example of the interactions between tectonic events, magmatic activity and carbonate productivity. The major factors that controlled the nucleation of carbonate factories on the Botoman High Atlas platform were: (i) synsedimentary tectonism, as normal faulting resulted in tilting of fault blocks causing irregular topographies and subsequent sharp erosion; (ii) volcanism, because pyroclastic influx smothered carbonate factories except in distal areas of the platform or during quiescent episodes of volcanic activity; and (iii) the influence of successive shoaling parasequences. The Botoman reefs exhibit a wide range of external morphologies, including tabular (biostromes) and domal (bioherms and patches) boundstones, which do not exceed 3.5 m of thickness. Although archaeocyathan-microbial reefs only developed under clearwater conditions, microbial reefs grew also under turbid-water conditions. Domal and digitate stromatoids,
Girvanella
crusts,
Epiphyton
bushes and thromboid-stromatoid intergrowths document the ability of some microbial communities to develop heterotrophic strategies when submitted to a moderate terrigenous input. Turbidity was a major ecological factor that constrained development of filter/suspension-feeder and phototrophic organisms, but not necessarily of benthic non-phototrophic microbial communities.
Late Frasnian phillipsastreid biostromes in Belgium
Authors: Poty Edouard , Chevalier Emmanuel
Published: December 2007

In the Belgian Namur-Dinant Basin the boundary between the Lustin Formation and the Aisemont Formation (in the Lower
rhenana
conodont Biozone) corresponds to a fall followed by a rise in sea level, leading to the first recorded late Frasnian coral crisis. The Aisemont Formation records a transgressive-regressive cycle. Prior to the crisis most of the colonial rugose corals were members of the Family Disphyllidae, but these were largely replaced by corals belonging to the Phillipsastraeidae. Among these
Frechastraea
colonized all environments of the basin and was the main constructor of a biostromal reef in its northern-most proximal area, in the fair-weather wave zone. Corals did not encrust each other and therefore were not firmly attached, but they hug tightly the substrate (a dead coral colony) and rest closely on it to resist to the turbulence of waves. During the Silurian and Devonian, up until the late Frasnian crisis, shallow-water reefs in turbulent water were usually built by encrusting stromatoporoids, whereas rugose corals were restricted to waters of lower energy. Indeed, they were unable to encrust substrates, unlike stromatoporoids and post-Palaeozoic scleractinians, and to live in turbulent habitats. In Belgium argillaceous sedimentation prevented the development of stromatoporoids and provided an opportunity for the corals to colonize empty niches and to construct biostromes in relatively high-energy environments. At the same time
Alveolites
and stromatoporoids were dominant in a mid-proximal environment below the fair-weather wave base, but within the storm wave zone, where they also constructed biostromes.
Estimation of palaeoenvironmental changes: can analysis of distribution of tabulae in tabulates be a tool?
Authors: Zapalski Mikołaj K. , Hubert Benoît , Mistiaen Bruno
Published: December 2007

Growth periodicity (cyclomorphic variation) in corals is expressed by various features, among them changes in the distribution of tabulae. A method potentially useful in analysis of periodical environmental changes is proposed herein. Measurement of spaces between tabulae in tabulate corals and preparation of a histogram converted into a trend curve may show relative periodical fluctuations of the environment. Such an analysis, exemplified here on Givetian
Pachyfavosites
sp. from the Avesnois (northern France), shows that this method may be used as a tool for estimation of environmental changes.
The economic importance of contourites
Authors: Viana A. R. , Almeida W. , Nunes M. C. V. , Bulhões E. M.
Published: December 2007

The importance of contour currents in shaping and building continental margins has long been accepted. Their economic implications and the stratigraphic framework in which they are developed remain largely unknown. Data retrieved from sidescan sonar images, seismic profiles and their attribute maps, as well as sea-floor coring, boreholes and the few known outcrops around the world, suggest that bottom currents can locally develop large deposits of relatively coarse-grained sediments. Accumulation of coarse-grained deposits under the influence of bottom currents requires sediment availability, a geologically persistent strong circulation regime and a favourable physiographic setting both for enhancing the currents and for hosting the sediments. The hydrocarbon exploration of oceanic depositional systems demands a better understanding of the role of bottom currents and their implications for petroleum systems such as reservoir and sealing rocks. Such understanding implies additional alternatives for the definition of exploration targets and prospect risk reduction. Correlating seismic anomalies from 3D mapping with core and well logging data reveals the depositional geometry and sedimentological characteristics of coarse-grained contourites. Fine-grained drifts can locally and regionally develop large and thick accumulations, which have an important seal potential for trapping hydrocarbon.