Discussion of “A simple method to determine breaker height and depth for different deepwater wave height/length ratios and sea floor slopes”, by J.P. Le Roux [Coastal Engineering 54 (2007) 271–277]

In the recent paper by J.P. Le Roux [Coastal Engineering 54 (2007) 271–277], the author provides a simplified approach to calculating the depth, length, and height of waves at the onset of depth-induced breaking (i.e. at the breaker line). However, the proposed methodology and the comparisons to other methods suffer from a large number of inconsistencies and basic calculation errors. In addition, there are a number of erroneous physical interpretations and many of the conclusions are based on erroneous data. The remaining conclusions are either not new or based on circular logic, such as to render them moot. In the following, we will not attempt to point out all the errors or inconsistencies that we found, instead we focus on major points of contention.     

Macrofaunal density and biomass in the Campeche Canyon, Southwestern Gulf of Mexico

The composition, density and community structure of the benthic macrofauna were investigated in sediments of the Campeche Canyon in the SW Gulf of Mexico. Total macrofaunal density ranged from 9466±2736 ind m⁻² at the continental shelf station to 1550±195 ind m⁻² in the canyon. Density values significantly diminished with distance from the coast and depth; only a few stations in the center of the canyon displayed larger density values (E-37 with 4666±1530 ind m⁻², E-36 with 5791±642 ind m⁻² and E-26 with 6925±2258 ind m⁻²). Densities were positively correlated to organic nitrogen in the sediment (r=0.82) and coarse silt (r=0.43), and negatively with depth (r=−0.74) and distance from the coast (r=−0.68). At all stations, the polychaete worms contributed most to the multi-species community structure. The nematodes and Foraminifera displayed their highest densities in the center of the canyon. The biomass values declined significantly with depth. We conclude that the macrofauna density and biomass changed in response to organic matter contents in the sediment, both with distance from the coast and with depth.     

A predictive numerical model for potential mapping of the gas hydrate stability zone in the Gulf of Cadiz

This paper presents a computational model for mapping the regional 3D distribution in which seafloor gas hydrates would be stable, that is carried out in a Geographical Information System (GIS) environment. The construction of the model is comprised of three primary steps, namely: (1) the construction of surfaces for the various variables based on available 3D data (seafloor temperature, geothermal gradient and depth-pressure); (2) the calculation of the gas function equilibrium functions for the various hydrocarbon compositions reported from hydrate and sediment samples; and (3) the calculation of the thickness of the hydrate stability zone. The solution is based on a transcendental function, which is solved iteratively in a GIS environment.The model has been applied in the northernmost continental slope of the Gulf of Cadiz, an area where an abundant supply for hydrate formation, such as extensive hydrocarbon seeps, diapirs and fault structures, is combined with deep undercurrents and a complex seafloor morphology. In the Gulf of Cadiz, the model depicts the distribution of the base of the gas hydrate stability zone for both biogenic and thermogenic gas compositions, and explains the geometry and distribution of geological structures derived from gas venting in the Tasyo Field (Gulf of Cadiz) and the generation of BSR levels on the upper continental slope.     

Precipitable water vapor (PWV) estimations from the site of the Eastern Anatolia Observatory<Superscript>∗</Superscript> (DAG), a new astronomical observatory in Turkey

We present preliminary statistics on the precipitable water vapor (PWV) content over the Karakaya Hills in Erzurum city, where the largest optical and near-infrared astronomical telescope in Turkey will be operated. Since the observatory will observe in the near-infrared (NIR), it is intended to perform PWV measurements of the atmosphere above the site by using signal delays in Global Positioning System (GPS) communication. The analysis of the GPS data recorded on the summit for almost one year shows that the atmosphere over the site of the observatory, which has an altitude of 3170 m, has favorable conditions for NIR observations. From GPS measurements, we report that the site had an average PWV of 3.2 mm and a median PWV of 2.7 mm between October 6, 2016, and June 15, 2017. We also present the time dependency of the PWV content and the correlations between the amount of PWV and the other meteorological records gathered from radiosonde flights and ground-based measurements.     

Observations of a Radio-Quiet Solar Preflare

The preflare phase of the flare SOL2011-08-09T03:52 is unique in its long duration, in that it was covered by the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) and the Nobeyama Radioheliograph, and because it showed three well-developed soft X-ray (SXR) peaks. No hard X-rays (HXR) are observed in the preflare phase. Here we report that no associated radio emission at 17 GHz was found either, despite the higher sensitivity of the radio instrument. The ratio between the SXR peaks and the upper limit of the radio peaks is higher by more than one order of magnitude than the ratio in regular flares. The result suggests that the ratio between acceleration and heating in the preflare phase was different than in regular flares. Acceleration to relativistic energies, if any, occurred with lower efficiency.     

The impact of extreme turbidity events on the nursery function of a temperate European estuary with regulated freshwater inflow

Estuaries are used as nursery grounds by numerous marine species despite being usually subject to strong anthropogenic disturbances. Abundances of marine recruits (fish and crustacean decapods) and their main prey (mysids) were monitored by monthly sampling, from June 1997 to February 2009, in the lower reaches of the Guadalquivir estuary (SW Spain). During that period, unusually high and persistent turbidity events (HPTEs) were observed twice. Both HPTEs started with strong and sudden freshwater discharges after relatively long periods of very low freshwater inflow. Data from this time-series were used to test the hypothesis that HPTEs may negatively impact the nursery function of estuaries either by decreasing prey availability or by decreasing survival/arrival of marine recruits. During HPTEs, the commonest mysid (Mesopodopsis slabberi), a key species in the estuarine food web, showed a significant decrease in abundance. Likewise, some marine recruits that prey on M. slabberi and whose peaks of abundance within the estuary occur in summer–autumn (Engraulis encrasicolus and Pomadasys incisus) were less abundant during HPTEs. It is also suggested that HPTEs might have triggered a shift in the distribution of the most euryhaline prey (Neomysis integer) and predator (Dicentrarchus punctatus and Crangon crangon) species, towards more saline waters. This could have contributed to an increase in the inter-specific competition (for food/habitat) within the estuarine nursery area. The results discussed in this study call attention to the need to reduce as much as possible the anthropogenic pressures that may stimulate the occurrence of high and persistent turbidity events (HPTEs) in order to preserve the nursery function of temperate estuaries.     

Zur geodynamischen Entwicklung des Iran,ein Beispiel intrakratonischer struktureller Vorgänge

Zusammenfassung Die einzelnen tektonischen Einheiten des Iran werden in ihrer faziellen und strukturellen Entwicklungsgeschichte dargestellt. Fazies und Paläogeographie sprechen dafür, daß vom Infrakambrium bis in die Trias der gesamte Raum zwischen dem Persischen Golf und dem Elburs-Gebirge eine einheitliche Entwicklung genommen hat. Eine zusammenhängende Plattformsedimentation in Schelffazies kennzeichnet dieses Gebiet während des gesamten Zeitraums. Es ist ein Teil Gondwanas. Paläomagnetische Befunde stützen diese Aussage. Ozeanische Kruste und damit Hinweise auf die Tethys als eine strukturelle Einheit fehlen während dieser Zeit in diesem Gebiet. Lediglich als Faunenprovinz in Flachmeerfazies ist sie wirksam. Das offene Meer lag vom Infrakambrium bis zur oberen Trias im Norden. In der Trias tritt mit einer Heraushebung, die mit tiefgreifender Lateritisierung verbunden ist, und einer anschließenden Transgression ein grundlegender Wechsel des geodynamischen Regimes ein. Von jetzt an erfolgen die Ingressionen in den Iran von Süden. Eine engräumige fazielle Differenzierung setzt ein. Kontinental beeinflußte Sedimente im Jura zeigen, daß im Iran ein Hochgebiet entstanden ist. Gleichzeitig tretenwahrscheinlich in Anlehnung an langlebige Geosuturen — Ophiolith-Radiolarit-Zonen auf, die als das Ergebnis intrakratonischer Zerbrechung gedeutet werden. Die Ingressionen gehen wahrscheinlich von Tiefseerinnen aus, in denen auch die Ophiolithe konzentriert sind. Der Aufstieg des ophiolithischen Materials an die Oberfläche erfolgte entlang von Linien, an denen sich flach geneigte Unterschiebungen von Kruste unter Kruste ereigneten. Dabei kam es zu erheblichen Krustenverkürzungen. Möglicherweise fällt der Umbruch des tektonischen Regimes in der Obertrias mit der Plattenkollision Arabia-Iran/ Eurasia zusammen. Die Grenze zwischen Arabia-Iran und Eurasia liegt aber nicht im Gebiet des Persischen Golfes und der Zagros-Ketten, sondern muß nördlich des Elburs-Gebirges gesucht werden.

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The individual tectonic units of Iran are represented with respect to the history of the development of their facies and structure. Facies and paleogeography indicate that the entire area between the Persian Gulf and the Elburz Mountains had a uniform development until the Triassic. During the whole period a coherent platform sedimentation remained characteristic of this area, which is part of Gondwana. Paleomagnetic data support this statement. Oceanic crust and thus any indications of the Tethys as a structural unit are absent in this area for that period of time. Its existence is only demonstrated in faunal provinces in shallow-marine facies. From the Infra-Cambrian to the Late Triassic the northern part of the area was open sea. During the Triassic, uplifting processes combined with deep lateritization and subsequent transgression initiated a basic change in the geodynamic regime. From this time on the ingressions into Iran proceeded from the south. At this time differentiation of facies began within small areas. Continental influences in the Jurassic sediments show that an elevated area was formed in Iran. At the same time ophiolite-radiolarite zones occurred, probably along long-lived geosutures. These zones are interpreted to be the result of processes breaking up the craton. Probably, the ingressions started from deep-sea furrows where ophiolite concentrations are found. The ascension of the ophiolitic material to the surface occurred along lines where gently dipping subduction of crust under crust took place. During this process it came to considerable crustal shortening. It is possible that the change in the tectonic regime during the Late Triassic coincided with the collision of the Arabia-Iran and Eurasia plates. The boundary between the Arabia-Iran and Eurasia plates is, however, not to be found in the area of the Persian Gulf and the Zagros mountain ranges, but is assumed to be north of the Elburz Mountains.

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Résumé Chacune des unités tectoniques de l'Iran font l'objet d'un exposé concernant leur développement du point de vue de leur facies et de leur structure. Le facies et la paléogéographie indiquent que, de l'Infracambrien au Trias, tout le territoire compris entre le Golf persique et la chaîne de l'Elbours a eu un développement unitaire. Une sedimentation de plateforme cohérente, à facies de shell, caractérise cette région pendant toute cette période. C'est une partie du Gondwana. Des données paléomagnétiques appuient cette affirmation. Toute croûte océanique et, de ce fait toute indice d'une Téthys en temps qu'unité structurale, sont absent dans cette région à ce moment. Une mer ouverte s'y étend au nord de l'Infracambrien jusqu'au Trias supérieur. Au Trias, un soulèvement, auquel est liée une forte latéritisation, et la trangression qui lui est liée, entraînent un changement radical du régime géodynamique. A partir de ce moment, des ingressions se produisent en Iran à partir du sud introduisant des différences de facies. Des sédiments montrant une influence continentale montrent qu'au Jurassique un fort soulèvement s'est produit en Iran. En même temps, vraisemblablement suivant une géosuture depuis longtemps active, apparurent des zones ophiolothiques à radiolarites, qui indiquent une rupture intracratonique. Les ingressions émanent vraisemblablement d'un sillon océanique profond dans lequel sont également concentrées les ophiolithes. La montée du matériau ophiolithique à la surface s'en suivit le long de lignes suivant lesquelles se sont produits dessous-charriages intracrustaux, d'où sont résultés de notables racourcissements de la crôute. Il est possible que cette rupture du régime tectonique coïncide, au Trias supérieur, avec la collision des plaques de l'Arabie Iran et de l'Ewrasie. La limite entre l'Arabie-Iran et l'Eurasie ne se trouve donc pas dans la région du Golfe persique et des chaînes du Zagros, mais doit être recherchée au nord de la Chaîne de l'Elbours.

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Origin of nodular chert in the carbonate rocks of the Kaladgi group (younger precambrian), Karnataka,India

Lensoid, irregular nodules and laminations of chert appear along the bedding planes and laminations of the Vidyanagar Dolomite Member of the Kaladgi Group, Karnataka, India. The field relations of the chert nodules with the host dolomite and evidence on polished hand-specimens clearly demonstrate that the cherts are secondary after dolomite. This contention finds extensive support from thin-sections which reveal floating relict dolomite fragments on a microcrystalline quartz mat, dolomite rhombs in various stages of progressive replacement, polycrystalline quartz rhombs apparently after dolomite. Chertification has also resulted in an aggrading neomorphic recrystallization of dolomicrite into dolomicrospar which rims the dislodged floating fragments of dolomite.Scanning electron microscopic studies revealed three distinct types of surfaces of chert; the polyhedral surface characteristic of microcrystalline quartz, the spongy surface characteristic of chalcedonic quartz (documented in thin-sections as semi-radiating to radiating aggregates of elongated crystals growing on the rhombic surfaces of dolomite, and the intermediate type showing both. The microcrystalline quartz seems to have originated through multinucleation at equally spaced centres on the dolomite mat, whereas the chalcedonic quartz originated by slow but direct and unhindered precipitation into cavities and residual pore-spaces, following dolomitisation. The silica invasion seems to have been accomplished by alkaline interstitial waters charged with silica.The occurrence and relation of chert-nodules with the host dolomite not only helps in unravelling their own origin, but also aids in drawing the dolomitisation curtain and in turn the post-dolomitisation diagenetic modifications of the host carbonates. It may be added, however, that the Kaladgi Carbonates have undergone mineralogical/textural modifications during diagenesis with superimposition of changes affected later, i.e. during tectonism which folded and cross-folded these sediments.     

Klüfte und Talrichtungen im Turon des südöstlichen Münsterlandes

Zusammenfassung Am Südostrand des Münsterländer Kreidebeckens fließen alle größeren Wasserläufe im Bereich der Turonkalke nach NNE oder NE, obwohl das allgemeine Gelände- und Schichtengefälle nach NNW gerichtet ist. Die Ursachen für diese Abweichung sind im Mechanismus der Felserosion zu suchen, der im wesentlichen durch die Eigentümlichkeiten der Karstgerinne und durch die Gesteinszerklüftung bestimmt wird. Bei den Detailuntersuchungen geben sich komplexe Beziehungen zwischen Fließrichtung und Kluftrichtungen zu erkennen.Besonders bedeutend für die Entstehung der NNE gerichteten Täler sind die 170°- und 30°-streichenden Klüfte.

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On the south-east border of the Cretaceous basin of Munster, Westfalia, the current directions of streams in the area of Turon-limestone go to NNE or NE, although the main dipping of land surface as well as bedding planes points towards NNW. This divergence is caused by the mechanism of rock erosion, which is determined by peculiarities of subterranean stream channels and joints in limestone. The investigations show complex relations between flow direction and direction of joints.The 170°- and 30°-striking joints are significant of the origin of the NNE direction of the valleys.

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Résumé Dans le Turonien au bord sud-est du bassin Crétacé de Münster (Westphalie) toutes les rivières coulent en direction nord-nord-est ou nord-est, quoique la surface morphologique générale et les couches soient penchées en direction nord-nord-ouest. Cette divergence est expliquée par le mécanisme de l'érosion qui dépend principalement des fentes et du caractère des ruisseaux karstiques. Pendant ces études on a pu observer des relations complexes entre la direction des courants et la direction des fentes.Les fentes en direction nord-nord-est (30°) et sud-sud-est (170°) ont considérablement influencé l'origine des vallées.

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Herrn Professor Dr.Roland Brinkmann zum 70. Geburtstag gewidmet.