Automatic Estimation of the Seafloor Geomorphology of the Santos Basin, Brazil

The bathymetry and acoustic backscatter of Santos Basin, Brazil were mapped using a SeaBeam 2112 (12 kHz, 151 beam) Multibeam Echosounder (MBES) aboard the R/V Falcon Explorer. This MBES data was acquired from January-November, 2000, during a high-resolution multi-channel 3D seismic survey, resulting in 380 parallel lines of 90 km length, spaced 250 m apart. The final survey mapped an area of 5,000 km${}^2$ in water depths of 900--2000 m. These closely spaced multibeam tracks resulted in an average overlap between swaths of 1000%, thereby ensonifying most areas of the seafloor at least ten times. Traditional (hand) processing of a dataset this dense is time-consuming and tedious, and is prone to subjective decisions and operator fatigue. However, the density of the survey makes it ideal for automatic processing methods. Recently, we have developed an algorithm called CUBE that addresses the twin concerns of robustness and reliability that are often raised about automatic processing methods. Based on a very robust multiple hypothesis Bayesian estimator, CUBE processes MBES bathymetry directly into a set of gridded products representing the best estimate of probable depth, and a measure of the uncertainty associated with this estimate. We apply CUBE to the Santos Basin data, illustrating in terms of processing time and human effort the advantages of processing such data automatically. We compare the automatically generated data with a hand-processed set, showing that the results agree to within the estimated experimental uncertainty. We next illustrate the use of CUBE as a data quality measure, indicating areas of concern in the data. Finally, we utilize the bathymetric grid resulting from CUBE to investigate the seafloor morphology, which includes a set of linear depressions parallel and perpendicular to the Shelf break. These linear depressions are the surface expression of fault planes related to subsurface salt walls. In the shallowest part, the detailed bathymetry also shows various pockmarks (350 m wide) possibly associated with fluid expulsion, while in the deeper portion we observe a small number of larger ones (2500 m wide), which are clearly inactive as they are partially filled with recent sediments. Some pockmarks are aligned with fault planes, suggesting a preferential pathway for fluid expulsion. The acquisition geometry for this survey allowed us to analyze the behavior of the backscatter response as a function of grazing angle for any given piece of seafloor, thus eliminating the need to assume a homogeneous seafloor across the swath. Although the backscatter is not calibrated, the variation in response can be used to investigate the effects of gas in shallow sediments of the survey area

Alien Registration- Calder, Edgar B. (Eastport, Washington County)

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A study of the variation in trace element content of hill pastures

1. The normal variation in mineral content of mixed hill pastures has been investigated with particular reference to the trace elements manganese, cobalt, nickel andiron. The variations in the cobalt and nickel contents of mixed pastures have been found to be as great as those of acetic -acid extracts of soil samples taken at the points where the pasture was sampled, and range from approximately 30% to 50%. The variations in manganese and iron contents are somewhat less (20% to 30%), while those in major element and silica- free -ash contents are less than 20%, with the exception of magnesium for which the variation is slightly higher.2. Factors which may contribute to the normal variation in each case, viz. (a) analytical error, (b) soil type and plant association, (c) seasonal effect and (d) personal error in sampling have been examined. The analytical and personal errors have been shewn to be relatively unimportan and there is no significant seasonal effect. The variations have been found to be generally of the same order of magnitude for areas uniform within themselves, but differing in vegetation and soil type.3. The mineral composition of some typical hill pasture species has also been investigated.4. The results for mixed pastures have been examined for possible trace element relationships, and a highly significant positive correlation has been found between cobalt and iron. No correlation has been found between pasture and soil - extractable cobalt, the latter values having been reassessed according to soil characteristics.5. A method has been recommended for the sampling of hill pastures for trace element analysis, and the errors associated with the method have been given. The method has been tested and found satisfactory

On the discovery of tetrapod trackways from Permo-Carboniferous redbeds of Prince Edward Island and their biostratigraphic significance

The first fossil tetrapod footprints that were discovered on Prince Edward Island, and which were previously undescribed, are small reptilian trackways assignable to the ichnogenera Notalacerta andGilmoreichnus. Their closest zoological correlatives are small, Permo-Carboniferous "stem-reptiles" of the families Protorothyrididae and Captorhinidae in the suborder Captorhinomorpha, and pelycosauran reptiles, possibly of the Ophiacodontidae. Reptiles of this type are rare to unrepresented in the skeletal fauna of the province. The biochronology of the track-bearing bed, combined with terrestrial vertebrate, palynological and macrofloral records, suggest that the host Pictou Group redbeds on Prince Edward Island young from late Stephanian (Pennsylvanian) at Malpeque Bay to early Permian in the north. The combined discoveries of tetrapod footprints and trackways from these Permo-Carboniferous redbeds suggests that the record is potentially extensive. Now included in this record is the youngest known occurrence of the ichno-genus Notalacerta. RÉSUMÉ Les premières empreintes de fossiles de tétrapodes découvertes sur l'Île-du-Prince-Édouard, et précédemment non décrites, sont des traces d'un petit reptile qu'on peut rattacher aux ichnogenres Notalacerta et Gilmoreichnus. Leurs parents géologiques les plus proches sont les petits " reptiles-tiges » permocarbonifères des familles des protorothyridides et des captorhinides du sous-ordre des captorhinomorphes, ainsi que les reptiles pélicosauriens, possiblement les ophiacodontides. Les reptiles de ce type sont rares sinon absents au sein de la faune squelettique de la province. La biochronologie des strates renfermant des traces conjuguée aux relevés de vertébrés terrestres et aux relevés palynologiques et macrofloraux laisse supposer que les couches rouges hôtes du groupe de Pictou, sur l'Île-du-Prince-Édouard, remontent à la période du Stéphanien tardif (Pennsylvanien), dans la baie Malpeque, au Permien précoce, dans le nord. Les découvertes combinées d'empreintes et de traces de tétrapodes des couches rouges permocarbonifères semblent indiquer que la quantité d'enregistrements pourrait être vaste. Ces enregistrements comprennent désormais la manifestation la plus récente connue de l'ichnogenre Notalacerta [Traduit par la rédaction.

Estimation of Sounding Uncertainty from Measurements of Water Mass Variability

Analysis techniques are introduced that allow for estimation of potential sounding uncertainty due to water mass variability from reconnaissance campaigns in which oceanographic parameters are measured at a high temporal and spatial resolution. The analysis techniques do not require sounding data, thus analyses can be tailored to match any survey system; this allows for pre-analysis campaigns to optimize survey instrumentation and sound speed profiling rates such that a desired survey specification can be maintained. Additionally, the output of the analysis methods can potentially provide a higher fidelity estimation of sounding uncertainty due to water mass variability than uncertainty models in common use.Se presentan análisis técnicos que permiten una estimación de posibles incertidumbres en los sondeos, debidas a la variabilidad de la masa de agua, procedentes de campañas de reconocimiento en las que los parámetros oceanográficos son medidos con una resolución temporal y espacial elevada. Los análisis técnicos no requieren los datos de sondeos, así pues dichos análisis pueden adaptarse a cualquier sistema hidrográfico. Esto permite campañas de análisis previos para optimizar la instrumentación hidrográfica y los niveles de descripción de la velocidad del sonido, para que pueda mantenerse una especificación hidrográfica deseada. Además, el resultado de los métodos analíticos puede proporcionar potencialmente una estimación de la fidelidad de las incertidumbres en los sondeos, debidas a una variabilidad de la masa de agua mayor que la de los modelos de incertidumbres que se utilizan corrientemente.Des techniques d’analyse sont introduites afin de permettre l’estimation de l’incertitude potentielle des sondes due à la variabilité de la masse d’eau à partir de campagnes de reconnaissance dans lesquelles les paramètres océanographiques sont mesurés avec une haute résolution temporelle et spatiale. Les techniques d’analyse ne nécessitant pas de données de sondes, les analyses peuvent donc être ajustées pour s’adapter à tout système de levés ; ceci permet aux campagnes de pré-analyse d’optimiser l’instrumentation hydrographique ainsi que les niveaux de profilage de la vitesse du son de manière à conserver une spécification de levé souhaitée. En outre, le résultat des méthodes d’analyse peut potentiellement fournir une estimation à plus haute fidélité, en ce qui concerne les incertitudes des sondes du fait de la variabilité de la masse d’eau, que les modèles d’incertitude en usage