Navegando por Assunto "Geologia do Quaternário"

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Estratigrafia holocênica morfodinâmica atual da planície costeira da Ilha de Algodoal e Marudá
(Universidade Federal do Pará, 1996-11-08) SANTOS, Valdenira Ferreira dos; EL-ROBRINI, Maâmar; http://lattes.cnpq.br/5707365981163429; https://orcid.org/0000-0001-7850-1217
The Coastal Plain of Algodoal and Marudá Island is located on the Bragantina Platform, on the coast of "rias" in the NE of the State of Pará. This plain is limited by the Coastal Plateau, built on Tercio-Quaternary sediments of the Barreiras and Post-Barreiras Formation. Geomorphologically, the Coastal Plain of Ilha de Algodão and Marudá was compartmentalized into 7 morphogenetic units: estuarine channel, beach-dune cords, tidal flat, beach, dunes, salt marshes and "cheniers". This subdivision reveals the existence of a beach-dune string system concomitant with a tidal flat system. The stratigraphic studies allowed the identification of 9 morphostratigraphic units: beach-dune ridges, paleodunes, coastal dunes, beach, supratidal plain, intertidal plain, sandy tidal bar, tidal bar and saline marsh; which in part are related to the morphogenetic units of the plain. 10 stratigraphic facies were also defined: intertidal mud, sand from tidal excavation channels, sand and mud from bars, supratidal plain mud, sand and marine mud, estuarine mud, marine sand, bioturbated silty clay, undifferentiated sediments and sand. mottled. The integration of morphological and stratigraphic data allowed the identification of two stratigraphic sequences: transgressive sequence (S1) with estuarine and beach facing environments and ; regressive sequence (S2) characterized by a beach-dune string system, interdigitated with a tidal flat system. These sequences point to an evolution of this plain within a transgressive-regressive cycle that probably started at the end of the Late Pleistocene. The morphodynamic analysis indicates that the system has been constantly modified in the last 19 years. Waves and tides are the major erosional agents that act in restricted sectors of the coastal plain, while the biggest changes result from coastal accretion to the NE of Algodoal and Marudá Islands. The results of this work show the influence of hydro and aerodynamic parameters (tides, waves, currents, wind and weather), sea level variations and sediment input as preponderant factors in the evolution of the system.
Acesso aberto (Open Access)
Mapeamento Plani-Altimétrico da microrregião do Salgado paraense a partir de procedimentos fotogramétricos
(Universidade Federal do Pará, 1995-03-31) PEREIRA, Silvio Wigwam Mendes; EL-ROBRINI, Maâmar; http://lattes.cnpq.br/5707365981163429; https://orcid.org/0000-0001-7850-1217
The Coastal Microregion of Salgado Pará is characterized by a low topographic gradient controlled by paleopavements (stone layers) and lateritic crusts, having its model developed in Cenozoic units (Pirabas and Barreiras Formations) and Quaternary (Post-Barriers and recent sediments). From a geographic and geomorphological point of view, this area is subdivided into two geosystems: in resistasia of regressive character, with geomorphogenesis associated with anthropic activities of continental domain; and, marginal-mosaic with resistasia and biostasis responsible for the morpho-environmental susceptibility of the coastal domain. The photogrammetric and morphotopographic mapping of the Coastal Microregion of Salgado Paraense allowed the elaboration of eleven topographic maps (systematic and non-systematic) suitable for morpho-environmental studies. An integrated photogrammetric system of a 1st order analog stereo-returner (universal type) - Topocart-D/Zeiss and Orthophot-E/Zeiss differential optical transformer was used to make the maps, aided by other cartographic systems such as interpretoskop-C/Zeiss, aerosktchmaster /Zeiss and ST-4/Wild stereomicrometer. The modeling of the data arranged in four levels of stereotopographic density, showed the photogrammetric capacity of Topocart-D, and the mapping alternatives for the Coastal Microregion of Salgado Paraense. a predominantly transgressive system with localized regressive pulses. These processes are also indicated by the morphodynamic changes of the geofacies, whose morphotopographic correlations allowed the compartmentalization of the Coastal Microregion of Salgado Paraense in the NE, SW and E topographic domains, which encompass the morphological domains of esplanade, coastal plain and estuarine plain. The fluvial-coastal systems of Japerica-Primavera-Quatipuru, Pirabas-Inajá, Arapepó-Urindeua and Maracanã-Caripi characterize the NE, SW and E domains. dissected developed in lateritic crusts, in which concave amphitheaters of springs (catchment basins) and erosive levels are inserted; the coastal plain, which corresponds to the coastal portions directly influenced by the ocean, is characterized by beaches, active and inactive cliffs, active and degraded mangroves, platforms of laterite blocks and mobile and degraded dune cords; and, the estuarine plain is formed by estuaries filled with mud and sand banks, generally degraded dunes, active and inactive cliffs, elliptical to elongated hills, trapezoidal “strained”, saline wetlands with a lot of organic matter, pre-salt, peripheral igapós and penelagos in the form of double-bottomed saucers. In the SW topographic domain: the esplanade shows a flat-shaped relief with a table top and erosive levels, controlled by paleopavements, the relief also being characterized by valleys in the “◡” shape and springs of the dale and thalweg types; the coastal plain exhibits narrow oceanic beaches with curved ends (spits), inter-dune fields, active and inactive cliffs, leterite block platforms, abrasion platforms and oceanic mangroves; and, the estuarine plain encompasses unfilled estuaries and partially filled estuaries. Topographic domain E, encompasses only the esplanade (also controlled by paleopavements) and estuarine plain compartments, and belongs to an independent morphotopographic system, featuring a single interfluvial corridor. The esplanade shows normal short and convex slopes, inserted in multidirectional drainage patterns; and, the estuarine plain is bordered by active and inactive large cliffs. This estuarine plain has numerous underwater and subaerial indents formed by blocks of laterite and kilometric lateral mangroves penetrating into transverse valleys in the E-W direction.