Navegando por Assunto "Morfoestratigrafia"

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Acesso aberto (Open Access)
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)
Estudo morfoestratigráfico e sedimentológico dos depósitos holocênicos da planície costeira de Maracanã – NE do Pará
(Universidade Federal do Pará, 2007-03-15) CARVALHO, Charles de Almeida; EL-ROBRINI, Maâmar; http://lattes.cnpq.br/5707365981163429
The Maracanã Coastal Plain is located in the northeastern part of the Para State where there are some coastal rias. This place is over tertiary sediments of the Barreiras and Pirabas Formations as well as is over quaternary sediments of the Pos-Barreiras. The Maracana Coastal Plain is influenced by an macrotidal regime (amplitude > 4 m). The Maracana Coastal Plain is characterized by three different geomorphologic domains: (1) Coastal Upland that presents active and inactive cliffs, and platforms of abrasion build in the laterites of Barreiras Formation as well as outcrop of the limestone from Pirabas Formation; (2) Coastal Plain that presents coastal dune fields and palaedunes, beach, mud-tide flat (mangrove), sandy plain, edd-tide delta, beach ridge plain and lakes; (3) Estuarine Plain which presents estuarine funnel, tidal channel and floodflat. In the Maracana Coastal Plain were identified nine morfostratigraphic units: (1) mud-tidal flat, (2) point bar, (3) Sandy plain, (4) dune, (5) paleodune, (6) beach, (7) ebbtide delta, (8) beach ridge plain, and (9) lake. These morfostratigraphic units are associated to three stratigraphic facies: (1) sand facies and point bar mud facies (sandy and muddy) that show alternate layers of greenish gray mud and light gray sand; (2) sea sand facies located over infratide mangrove that it has light olive gray and yellowish gray sands; (3) estuarine mud-sand facies that mean a variable thicking alternate layers with dark gray mud or greenish gray mud. In the Maracana Coastal Plain were characterized three depositional sequences: (1) Basal Transgressive Marine Succession S1, (2) Regressive Marine Succession S2 and (3) Transgressive Marine Succession S3. S1 show mid-large sand in its base (tidal channel) so that following by dark mud with high concentrations of organic matter (sand-silty clay). In these base, the sand is in moderate selection, but to top the sand is fine to middle size and it’s negative asymmetry. Distribution of the mineral clay was homogeneous (kaolinite = 45 %, ilite = 37 % and smectite = 18 %). Heavy minerals show larger concentration in the sandy facies, but the relative amount these minerals increased upward which owing zircon (35 %), staurolite (28 %), epidote (9 %) and cianita (11 %) presences. This sequence of sediments marks an estuarine mud, sea sand and seamud depositions during marine transgressive period. S2 is constituted by thin-very thin, well selected, near asymmetric sand that could be classified as clay-sand sediment. The mineral clay is represented by slight increase of the smectite as well as a decrease of the kaolinite in top sequence. The main heavy mineral located in the point bar are staurolite (44 %), zircon (39 %) and tourmaline (9 %) while there are zircon (39 %) and staurolite (27 %) contents at bottom sequence. This sequence was build during a marine regressive period from coastal upland so that consist the progradational deposits over sequence S1. The sequence S3 corresponds to unit of dunes, barrier-arrow beach, sandy and muddy bars. Coastal dune deposits show some crossing stratification to slow slope and thin layer of mud. Beach deposits show crossing stratus in low angle. Sandy bars presents a full structure with some bioturbation. The contents of sand are well selected and it has quartz as main mineral. The amount of heavy mineral was lower at top layer. Composition and texture of heavy mineral provide a rounding shape of the sediments because it has been transported, reworked and it was suffering a strong abrasion. In the Maracana Coastal Plain, grain size and mineral distribution are homogeneous being not possible to determine a clear edge between stratigraphic sequences either continental contribution or sea sediment source. There are so many morphologic features (cheniers, paleochannel, paleodelta) and some stratigraphic characteristics that suggest an occurrence of sea level oscillations as well as a migration in the shoreline position. The presence of transition environment deposits (tide flat) show some stratigraphic evidence in the study area. The Maracana Coastal Plain and the northeastern coastal area of the Para State (Bragança, Salinopolis and Marapanim) are over actual transgression event (large sandy plain and beach presences).
Acesso aberto (Open Access)
Morfoestratigrafia da planície costeira do município de São João de Pirabas (Porção NW) – NE do estado do Pará
(Universidade Federal do Pará, 1998-08-07) SILVA JÚNIOR, Osmar Guedes da; EL-ROBRINI, Maâmar; http://lattes.cnpq.br/5707365981163429; https://orcid.org/0000-0001-7850-1217
A porção NW da Planície Costeira do Município de São João de Pirabas (NE do Estado do Pará) é parte integrante da Bacia Pará-Maranhão, que juntamente com as bacias do Marajó e Bragança-Viseu seriam o produto de movimentos extensionais (reativação Sul-Atlântiana) vinculados à separação Brasil-África no início do Jurássico. Nesta planície ocorrem principalmente depósitos terciários e quaternários, cuja distribuição e espessura vem sendo influenciada por movimentos tectônicos atuantes desde o Mioceno. Foram individualizadas duas unidades morfológicas distintas: (i) Planalto Costeiro e (ii) Planície Costeira, definidas com base em dados morfológicos e critérios morfogenéticos (forma e natureza do sedimento, vegetação e processos atuantes). O Planalto Costeiro consiste em um relevo colinoso, suavemente ondulado, sustentado pelos sedimentos do Grupo Barreiras e Pós-Barreiras; e a Planície Costeira é caracterizada por ambientes de manguezais, sistema de terraços, cheniers, paleodunas, interdunas, lagos, dunas costeiras atuais, praias e barras arenosas. Baseado no conceito de unidades morfoestratigráficas e fáceis estratigráficas, os ambientes e depósitos sedimentares quaternários desta planície, foram subdivididos em 08 unidades morfoestratigráficas: (i) manguezal, (ii) cheniers, (iii) barras em pontal, (iv) barras arenosas de canal, (v) paleodunas, (vi) lagos, (vii) dunas costeiras atuais e (viii) praias, e 08 fácies estratigráficas: (i) areia marinha, (ii) areia e lama marinha-estuarina, (iii)) areia e lama de barra em pontal, (iv) areia de canal de maré, (v) areia de cordões praiais, (vi) lama de intermaré, (vii) sedimentos argilo-arenosos e (viii) sedimentos carbonáticos. A análise estratigráfica, permitiu a identificação de um padrão de sedimentação, que pode ser visualizado através de quatro sucessões marinhas: (i) sucessão marinha retrogradacional basal (SB), na qual podem ser identificados sedimentos lamosos de intermaré, areias de antigos cordões praiais, bem como areias de canais de maré; (ii) sucessão marinha retrogradacional (S1), caracterizada por sedimentos predominantemente arenosos de face praial (“shoreface”); (iii) sucessão progradacional (S2) com ambiente de planície de maré e cheniers associados e; (iv) sucessão retrogradacional atual (S3) constituída por cordões duna-praia, barras arenosas longitudinais e de baías, que migram sobre os depósitos de manguezal. Os aspectos evolutivos da Planície Costeira de São João de Pirabas, estão relacionados às oscilações do nível do mar, responsáveis por eventos transgressivos e regressivos, atuantes durante o Holoceno, a partir de 5.100 anos A.P., e que deram origem às sucessões S1, S2 e S3. A sucessão SB teria sua evolução condicionada por eventos transgressivos atribuídos, provavelmente, ao Pleistoceno Terminal.
Acesso aberto (Open Access)
Morfoestratigrafia do noroeste da planície costeira de São João de Pirabas (Nordeste do Pará)
(2001) SILVA JÚNIOR, Osmar Guedes da; EL-ROBRINI, Maâmar
A sedimentary pattern, characterized by four marine successions, is identified at the northwestern portion of São João de Pirabas coastal plain (northeastern of Pará State) using morphostratigraphical analysis. The successions are: (i) basal retrogradational marine succession - SB, (intertidal mangrove muds, old beach ridges sand and tidal channel sand); retrogradational marine succession - S1, (sandy sediments of the shoreface); progradational succession - S2 (tidal flat and chêniers associated) and; actual retrogradational succession - S3 (dune-beach ridges, longitudinal sandy bars and bays, migrate over mangrove deposits). The evolution of this plain is related to sea-level changes associated with neotectonic movements since the Pliocene that gave origin to the SB succession during transgressive period related to Upper Pleistocene (?). The S1, S2, and S3 successions were developed due to transgressive and regressive cycles during last 5.100 years B.P. until today.