Caracterização geológica, geomorfológica e oceanográfica do Sistema Pisa Sal, Galinhos/RN - Nordeste do Brasil, com ênfase à erosão, ao transporte e à sedimentação
The present work has as objective to study the behavior of physical-environmental characteristics of the Pisa Sal system, particularly the bathymetry, the facies characterization and the bottom morphology; the pattern of tidal currents circulation and of the termohalinas properties; the erosion a...
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| Formato: | doctoralThesis |
| Idioma: | por |
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| Endereço do item: | https://repositorio.ufrn.br/jspui/handle/123456789/23767 |
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| Resumo: | The present work has as objective to study the behavior of physical-environmental
characteristics of the Pisa Sal system, particularly the bathymetry, the facies
characterization and the bottom morphology; the pattern of tidal currents circulation and
of the termohalinas properties; the erosion and sedimentation zones, the bulk erosion
and your relationships with the hydrodynamic; the sediments transport, the sediments
age and sedimentation rate. The integrated data set used includes meteorological,
bathymetric, sonographic, oceanographic (currents and termohalinas properties),
topographic and sedimentological data, as well 14C and 210Pb datation. The Pisa Sal
system is part of the Galinhos-Guamaré lagoon-estuarine complex, located in Galinhos,
northern coast of the Rio Grande do Norte state. It is an area under influence of salt
industry, shrimp farming and oil industry. The meteorological data classifies the area
climate as dry, with high temperature, low precipitation and strong and constant winds,
responsible for important environmental alterations in the system. The Pisa Sal system
presents small dimensions (extension of 8,0 km, medium width of 150 m and maximum
depth of -4,23 m), longitudinal profile to regulate, traverse profile in " V " (head) and in "
U " (mouth), horizontal gradient, and different bedforms (e.g. ripples marks, 2D and 3D
sub-aquatic dunes, flat, rocky). The sedimentary facies are represented by siliciclastic
sandy and muddy sediments, with amount variation of biodetritic granule and gravel.
The sediments texture varies from very coarse sand to silt. The tidal currents changes
from weakly asymmetric to symmetrical, with higher speeds during the ebb-spring tide
in the winter period, and directions reflecting the channels orientation. The drainage
artificial channels (CDs) present the same behavior of the Pisa Sal channel, however
with smaller intensity. The thermohaline properties classify the system as a tidal
channel with hyper-saline characteristics, behavior of an inverse estuary (negative
estuary), vertically very mixed, tidal forced, where the turbulent diffusion process is
responsible for the salt transport and by the salinity reduction over the year. The Pisa
Sal channel and CDs erosion are associated to the concave margin of the meandring
channel caused by oceanographical, climatic and anthropic phenomena, which stand
out: tides, tidal currents, rain, superficial drainage, winds, small waves, channels
excavation, infiltration, composition and slope maintenance. The transport of bottom
sediments and suspension is controlled by the speed variation of tidal currents. It is
more efficient during the spring tides and in the ebb cycles, causing sediments exports.
The age of the sediments of the Pisa Sal channel is 1562 ± 22 cal years AP and of the
Volta do Sertão channel is 332-432 ± 25 cal years AP. The calculated sedimentation
rates in these two channels was 0,47 and 0,50 cm/year, respectively. The economical
activities of the salt industry, shrimp farming and oil industry associated to the natural
phenomena (temperature of the air and high evaporation level, low precipitation index,
mesotidal conditions, high speed of the tidal currents and winds) are responsible for the
environmental alterations in the Pisa Sal system. |
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