3ERL - Papers/ Artigos Científicos
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- Allochthonous salt, structure and stratigraphy of the north-eastern Gulf of Mexico. Part I: StratigraphyPublication . Wu, Shengyu; Vail, Peter R.; Cramez, CarlosMajor sequences boundaries associated with eustatic sea level changes are correlated to the general stratigraphy of the north-eastern Gulf of Mexico.
- Allochthonous salt, structure and stratigraphy of the north-eastern Gulf of Mexico. Part II: StructurePublication . Wu, Shengyu; Bally, Albert W.; Cramez, CarlosThe Kinematic evolution of allochthonous salt in the north-eastern Gulf of Mexico proceeds in three stages. (1) Since the Middle Jurassic deposition, the Louann Salt was loaded by sediments causing episodic basinwartd movement of the salt, ultimately leading to large concentrations of salt masses in a slope environment by the end of the Lower Cretaceous. (2) A regime of starved sedimentation during Late Cretaceous and Early Oligocene is responsible for the stabilization of these early salt accumulations. (3) With renewed rapid accumulation of sediments, during the Neogene and pliocene, extensive allochthonous salt tongues and shetts formed by gravity spreading within the younger sediments of the slope. Autochthonous salt,allochthonous salt and detached allochthonous salt are typical stages of evolution. Major down to the basin growth faults separate allochthonous salt sheets from their original feeder stocks. Extension along down to the basin master growth faults in compensated mainly by salt withdrawal and partly by basinward shortening.
- Optical Morphology of Hydrocarbons and Oil Progenitors in Sedimentary Rocks- Relations with Geochemical ParametersPublication . Alpern, B.; Lemos de Sousa, M. J.; Pinheiro, H. J.The objective of the present research...
- Raft tectonics in the Kwanza Basin, AngolaPublication . Duval, Bernard; Cramez, Carlos; Jackson, M. P. A.Raft tectonics (tectonique en radeaux) allows the extreme thin-skinned extension of overburden over a dêcollement of thin salt or other evaporites.
- Detection and evaluation of hydrocarbons in source rocks by fluorescence microscopyPublication . Alpern, B.; Lemos de Sousa, M. J.; Pinheiro, H. J.; Zhu, X.In pursing the detection of hydrocarbons in sedimentary rocks by conventional petrological methods, an attempt has been made to correlate standard fluorescence parameters with the quality and quantity of hydrocarbons present in crushed rocks embedded in epoxy resin. The capacity of the embedding resin, commonly used in the preparation of petrographic samples, to extract and physically fix hydrocarbons is recognized. This phenomenon permits one to measure monochromatic fluorescence parameters, I and
- A methodology for parameter estimation in seaweed productivity modellingPublication . Duarte, Pedro; Ferreira, JoãoThis paper presents a combined approach for parameter estimation in models of primary production. The focus is on gross primary production and nutrient assimilation by seaweeds. A database of productivity determinations, biomass and mortality measurements and nutrient uptake rates obtained over one year for Gelidium sesquipedale in the Atlantic Ocean off Portugal has been used. Annual productivity was estimated by harvesting methods, and empirical relationships using mortality/ wave energy and respiration rates have been derived to correct for losses and to convert the estimates to gross production. In situ determinations of productivity have been combined with data on the light climate (radiation periods, intensity, mean turbidity) to give daily and annual productivity estimates. The theoretical nutrient uptake calculated using a 'Redfield ratio' approach and determinations of in situ N and P consumption by the algae during incubation periods have also been compared. The results of the biomass difference and incubation approaches are discussed in order to assess the utility of coefficients determined in situ for parameter estimation in seaweed production models.
- Interlaboratory comparisons of petrography of liquefaction residues from three Argonne Premium coalsPublication . Hower, J. C.; Anderson, K. B.; Mackay, G.; Pinheiro, H. J.; Flores, Deolinda; Lemos de Sousa, M. J.Three Argonne Premium coal samples, the Beulah-Zap lignite (North Dakota), the high volatile A bituminous Stockton (West Virginia), and the low volatile Pocahontas No. 3 (Virginia), were ground to three initial sizes: -20 mesh, -100 mesh, and "micronized". The samples were each subjected to liquefaction at 673 K for 30 min at a 2:1 tetralin :coal ratio and in an H 2 atmosphere at 13.79 MPa (~ 2000 psi). Polished pellets of the unconverted residues were circulated to three laboratories for a study designed to determine, albeit on a limited scale, the interlaboratory consistency in constituent identification and the problem areas in maceral/neo-maceral/mineral recognition. Within broad categories, the agreement for the Beulah-Zap and Pocahontas No. 3 residues is good. The high volatile A bituminous Stockton coal was the most plastic and most altered, resulting in a residue lending itself to more subjective interpretations. The biggest discrepancy between the laboratories is in the distinction of granular residue and mineral matter and in the transitions between "partially reacted macerals" and "vitroplast" and between "vitroplast" and "granular residue". The initial size of the feed coal appears to influence the recognition of material in the residue.
- A mechanistic model of the effects of light and temperature on algal primary productivityPublication . Duarte, PedroIn this work a model of algal primary productivity combining a mechanistic light function with a temperature Arrhenius function is presented. Data on primary productivity obtained with algae acclimated to different environmental conditions was used to test the model. A simple method for model parameter estimation based on regression analysis is described. The parameter estimates can be improved by a non-linear least-squares method (e.g. the Gauss-Newton method) resulting in a significant fit to the observed data as tested by regression analysis. According to the present model, the initial slope of the productivity/light curves is temperature dependent whilst the optimal light intensity is temperature independent. These model predictions were validated by the obtained experimental results.
- Source rock/dispersed organic matter characterization-TSOP research subcommitee resultsPublication . Teerman, S. C.; Cardott, B. J.; Harding, R. W.; Lemos de Sousa, M. J.; Logan, D. R.; Pinheiro, H. J.; Reinhardt, M.; Thompson-Rizer, C. L.; Woods, R. A.Because sedimentary organic matter consists of a diverse mixture of organic components with different properties, a combination of chemical and petrographic results offers the most complete assessment of source rock properties. The primary purpose of this Society for Organic Petrology (TSOP) subcommittee is to contribute to the standardization of kerogen characterization methods. Specific objectives include: (1) evaluation of the applications of different organic matter (petrographic) classifications and terminology, and (2) integration of petrographic and geochemical results. These objectives were met by completing questionnaires, and petrographic, geochemical and photomicrograph round-robin exercises. Samples that were selected for this study represent different petrographic and geochemical properties, and geologic settings to help identify issues related to the utilization of different classifications and techniques. Petrographic analysis of the organic matter was completed using both a prescribed classification and the individual classification normally used by each participant. Total organic carbon (TOC), Rock-Eval pyrolysis and elemental analysis were also completed for each sample. Significant differences exist in the petrographic results from both the prescribed and individual classifications. Although there is general agreement about the oil- vs gas-prone nature of the samples, comparison of results from individual classifications is difficult due to the variety of nomenclature and methods used to describe an organic matter assemblage. Results from the photomicrograph exercise document that different terminology is being used to describe the same component. Although variation in TOC and Rock-Eval data exists, geochemical results define kerogen type and generative potential. Recommendations from this study include: (1) A uniform organic matter classification must be employed, which eliminates complex terminology and is capable of direct correlation with geochemical parameters. (2) A standardized definition and nomenclature must be used for the unstructured (amorphous) organic matter category. Subdivisions of this generalized amorphous category are needed to define its chemical and environmental properties. (3) Standardized techniques including multimode illumination, types of sample preparations and data reporting will help eliminate variability in the type and amount of organic components reported.
- Fecundity, spore recruitment and size in Gelidium sesquipedale (Gelidiales,Rhodophyta)Publication . Santos, R.; Duarte, PedroGelidium sesquipedale fecundity was quantified by counting tetrasporangial sori and cystocarps per meter squared and by estimating the number of spores contained inside them . These were obtained by regression on a size metric of reproductive structures . Tetrasporangial sori length and cystocarp thickness were the best estimators of spore number. To assess spore recruitment, 12 pottery tiles were fixed to the bottom, and the appearance of small fronds was monitored. No clear seasonal pattern of reproduction was found . Tetraspore production peaked in March 1990 with 10.4 x 106 spores m-2, whereas the carpospore peak was lower, 4.9 x 10 5 spores m-2 in July 1989. Recruitment followed tetraspore peaks . The probability of a G. sesquipedale tetraspore making the transition to a recruit was 4.7 x 10-5. Frond length was significantly related to tetrasporangial sori number, while cystocarp number was only related to frond branching order. Minimum size for reproduction was 6.9 cm for gametophytes and 5.4 cm for tetrasporophytes; very rarely were cystocarpic fronds smaller than 9 cm, while tetrasporic fronds were often longer than 15 cm . Cystocarpic fronds were significantly shorter and had more branches than tetrasporic fronds .