Institute Geociencias UFF

Niterói, Brazil

Institute Geociencias UFF

Niterói, Brazil
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Antonelli P.L.,University of Alberta | Rutz S.F.,Federal University of Pernambuco | Fonseca K.T.,Institute Geociencias UFF
Nonlinear Analysis: Real World Applications | Year: 2012

A dynamical model of evolution of vascular plants via the Fungal Fusion hypothesis is presented. As in previous work on carbon flux in forest stands, solutions of the VolterraHamilton equations representing production of biomass satisfy Huxley's Allometric Law and are stable curves, but the explicit form of the production cost functional presented here, is simpler. Evolution of the dynamics takes place in stages, via random perturbation of cost produced by genetic drift at the molecular level, natural selection and time-sequencing changes in development. The relationship to the lichen symbiocosm is discussed. Our model presents a new feature, namely, in the final evolutionary stages, physiological production variables are expressed as nonlinear transformations of products of development in earlier epochs. Finally, we point out that, neither the parabolic cone nor the right circular cone method of measurement of carbon production is needed for the mostly young forest stand data gathered by Fonseca in the Mata Atlântica. The cylindrical approximation is sufficient for the most part. Old growth forests, however, will require the more mathematically elaborate techniques. © 2012 Elsevier Ltd. All rights reserved.


Kaji A.O.,State University of Rio de Janeiro | Guerra J.V.,State University of Rio de Janeiro | Fernandes A.M.,State University of Rio de Janeiro | de Oliveira R.F.,State University of Rio de Janeiro | And 2 more authors.
Revista Brasileira de Geofisica | Year: 2011

Vema Channel is an important passageway to the flow of bottom water between the Argentine and the Brazil basins. The channel morphology causes confinement and intensification of bottom currents that affect the ocean floor through sediment resuspension, transport and deposition, consequently playing a fundamental role in the formation of deep ocean deposits. The main goal of this paper is to evaluate the potential for sediment suspension and transport by the local currents through estimates of nearbed shear stresses as well as to assess whether the present dynamic conditions are conducive to the buildup of contouritic deposits in the Vema channel area. The available datasets include (i) current velocity and direction from the World Ocean Circulation Experiment (WOCE) and from moorings deployed by the Woods Hole Oceanographic Institute (WHOI); (ii) hydrographic parameters from the World Ocean Database 2005; and (iii) the description of bottom sediment characteristics and nephelometric profiles available in publications such as research reports and scientific articles. Calculated shear stresses indicate that local currents would be able to erode and transport medium silt with density similar to that of quartz during up to 87% of the deployment duration, a finding that is reinforced by the nephelometric profiles and by suspended particulate matter concentrations documented by filtered water samples. Channel enlargement downstream leads to loss of transport capacity along the channel. These results suggest that a modern drift deposit may still be under construction downstream the channel mouth where a contourite fan has intermittently been built since the late Oligocene. © 2011 Sociedade Brasileira de Geof ́i{dotless}sica.


da Silva R.J.P.,Institute Geociencias UFF | Vendeville B.C.,Lille University of Science and Technology | dos Reis A.T.,State University of Rio de Janeiro | Silva C.G.,Institute Geociencias UFF | And 2 more authors.
Revista Brasileira de Geofisica | Year: 2011

The stratigraphic recurrence of overpressured sedimentary intervals can act as multiple décollement levels over which the gliding of the sedimentary section takes place, as already suggested for the Foz do Amazonas basin. In this work a series of scaled physical experimental models was conceived and simulated in order to replicate possible scenarios involving the two main stages of deformation previously proposed for the basin: an early pre-fan stage of gravity gliding, followed by a late stage of gravity spreading triggered by the development of the wedge-like sedimentary cover associated to the onset of the Amazon Fan since the Late Miocene (̃10.5 Ma). All experiments were simulated with the aid of fluid injection into two weak intervals (silica microspheres layers) that acted as basal décollements leading to the gravitational deformation of overlying fragile layers. The mechanical behavior of these layers varied in time and space, according to the magnitude of pore fluid pressure and the overloading applied. The structural framework and interplay between the week levels, illustrated by the physical models, largely resembles main features of gravity tectonics in the Foz do Amazonas basin, as mapped by 2-D and 3-D seismic analysis, validating the main points proposed by the conceptual models. © 2011 Sociedade Brasileira de Geofísica.


dos Reis A.T.,State University of Rio de Janeiro | Maia R.M.C.,Institute Geociencias UFF | Silva C.G.,Institute Geociencias UFF | Gorini C.,University Pierre and Marie Curie | And 5 more authors.
Revista Brasileira de Geofisica | Year: 2011

The analysis of sparker monochannel seismic lines, coupled with a stratigraphic framework recently proposed for the study area, allowed us to put forward a new glacio-eustatic scenario and to reinterpret the origin of several seafloor features located along the 50,100,110,130 and 150 m isobaths. Our seismic stratigraphic and geomorphological analyses revealed that a wide variety of depositional processes were involved in the formation of these features. Sea-floor features observed near 50 and 100 m water depths, previously interpreted as paleo-coastlines developed at periods of stillstand in the course of the Holocene Transgression, are reinterpreted as the inclined frontal clinoforms of prograding sedimentary prisms deposited during the maximum highstands from, respectively, the Holocene and the Late Pleistocene (marine isotopic substages 5e, 5c and 5a and isotopic stage 3). Also, the escarpments and associated basal flat surfaces located around the 130 and 110 m isobaths, previously interpreted as nearshore systems developed close to the glacial maximum and during stillstands of the last deglaciation, respectively ~15 ky B.P. and ~13 ky B.P., are reinterpreted, together with a scarp found near the 150 m isobaths, as erosional remnants sculpted under forced regressive conditions during the Wisconsin Regression and preserved as a succession of flat surfaces that become gradually deeper and younger towards the shelf break. © 2011 Sociedade Brasileira de Geofísica.

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