Navegando por Assunto "Holoceno"

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Análise faciológica e estratigráfica da planície costeira de Soure (margem leste da ilha de Marajó-PA), no trecho compreendido entre o canal do Cajuúna e o estuário Paracauari
(Instituto Nacional de Pesquisas da Amazônia, 2007-06) FRANÇA, Carmena Ferreira de; SOUZA FILHO, Pedro Walfir Martins e; EL-ROBRINI, Maâmar
Soures's coastal plain, eastern Marajó island (Pará), is formed by muddy and sandy deposits, low gradient areas submitted to tidal and wave processes. The morphological features are tidal flats, estuaries, tidal channels and barrier-beach ridges . The faciological and stratigraphical analysis of six vibra-core with medium deph of four meters and from outcrops allowed a caracterization of depositional environments, temporal sequence and spacial corelation, the elaboration of stratigraphical seccions and column. Were identified five facies associations: (1) tidal flat facies, (2) mangrove facies, (3) tidal channel bar facies, (4) beach facies and (5) dune facies. The sedimentary history of the Soure coastal plain is represented by two stratigraphical successions: (1) progradational succession (tidal flat, mangrove and channel bar facies association) and (2) retrogradational succession (beach and dune facies association). These successions are related to a expansion phase of tidal flats and mangroves with progradation of the coastline (Middle/Late Holocene) and a posterior retrogradation phase with landward migration of the shoreline (Late Holocene). The depositional history of the Soure coastal plain is related to the holocenic evolution model of the northeast coastal plains of Pará.
Acesso aberto (Open Access)
Antropoceno na Amazônia: holoceno em curso ou prelúdio de uma nova época geológica do homem?
(Universidade Federal do Pará, 2021-08-31) PONTE, Franciney Carvalho da; SZLAFSZTEIN, Cláudio Fabian; http://lattes.cnpq.br/1348005678649555; https://orcid.org/0000-0002-2855-2056
The Natural Domains of the Brazilian Amazon present a high biogeographic diversity, favored by the complex geological substratum and equatorial climate, both predominant in the Amazonian landscape, located in the northern portion of Brazil, covering an area equivalent to 40% of the national territory (~3.7 million Km2). Human expansion in the Amazon has produced a series of transformations in its natural resources. In this sense, this work aimed to perform a retrospective on the trajectory of human beings in the Amazonian domains, through the spatialization of anthropogenic evidences and analysis of anthropogenic indicators, likely to be associated with precepts of the Anthropocene, made possible by a geographical perspective. The analysis raised the aspects of both morphoclimatic and phytogeographic domains, highlighting their dominant landscapes and natural systems, through biophysical compartmentalization, working as a substrate in the analysis of the dynamics of socio-spatial events and the materialized evidences of human action in the landscapes, under a broad temporal spectrum - the Holocene. The research was based on a holistic and integrative approach of variables, related to both natural and socio-spatial aspects, from a systemic vision, aimed at sizing and measuring the patterns of use of natural resources, the anthropogenization degree of natural domains and the proposition of anthropogenic landscapes/structures. In this sense, the research revealed that these domains currently present a very significant anthropogenic percentage of approximately 70%, the result of a broad and diverse socio-spatial dynamic, which attributed to the region a marked variability of human macrosystems and semi-natural landscapes embedded in apparently natural ecosystems. However, it was detected that this estimate is probably underestimated, if we consider the evidence, according to a cumulative perspective, reaching a value around 150%, that is, 50% above the total area of the study, which denounces a high anthropogenic pressure in the region. Given the above, and considering the Anthropocene precepts, centered on the anthropogenic conception, it is suggested that the Amazon region contains anthropogenic landscapes, substantially altered, for at least four thousand years AP, when much of its domains were already occupied and significantly used and managed by human groups.
Acesso aberto (Open Access)
Desenvolvimento da vegetação e morfologia da foz do Amazonas-PA e rio Doce-ES durante o Quaternário tardio
(Universidade Federal do Pará, 2013-11-05) FRANÇA, Marlon Carlos; PESSENDA, Luiz Carlos Ruiz; http://lattes.cnpq.br/0425441943533975; COHEN, Marcelo Cancela Lisboa; http://lattes.cnpq.br/8809787145146228
This work compares the vegetation and morphological changes occurred along the littoral of the Marajó Island, Amazonian littoral, and the coastal plain of the Rio Doce, southeastern Brazil, during the Holocene and late Pleistocene/Holocene, respectively, focused specifically on the response of mangroves to sea-level fluctuations and climate change, which have been identified in several studies along the Brazilian coast. This integrated approach combined radiocarbon dating, description of sedimentary features, pollen data, and organic geochemical indicators (δ13C, δ1₵N and C/N). On coastal plain of the Doce River between ~47,500 and ~29,400 cal yr BP, a deltaic system was developed in response mainly to sea-level fall. The post-glacial sea-level rise caused a marine incursion with invasion of embayed coast and broad valleys, and it favored the evolution of a lagoonal/estuary system with wide tidal mud flats occupied by mangroves between at least ~7400 and ~5100 cal yr BP. Considering the Marajó Island during the early and middle Holocene (~7500 and ~3200 cal yr BP) mangrove area increased over tidal mud flats with accumulation of estuarine/marine organic matter. It was a consequence of the marine incursion caused by post-glacial sea-level rise, further driven by tectonic subsidence. Dry conditions in the Amazon region during this time led to a rise is tidal water salinity and contributed to mangrove expansion. Therefore the effect of relative sea-level (RSL) rise was determinant to the mangrove establishment in the southeastern and northern region. During the late Holocene (~3050 – 1880 cal yr BP) the mangroves in both regions were retracted to a small area, with some areas replaced by freshwater vegetation. This was caused by the increase in river discharge associated to a wet period recorded in the Amazon region, and considering the coastal plain of the Doce River (southeastern Brazil), the mangroves shrank in response to an increase in fluvial sediment input associated to a sea-level fall.
Acesso aberto (Open Access)
A dinâmica dos manguezais durante o Holoceno tardio na foz do rio Ceará-Mirim, Rio Grande do Norte
(Universidade Federal do Pará, 2020-10-15) NUNES, Sérgio Patrick Dias Queiroz; FRANÇA, Marlon Carlos; http://lattes.cnpq.br/8225311897488790; 8225311897488790
This paper aims to debate the impacts of climate change on subtropical mangroves during late Holocene, on the coast of the state of Rio Grande do Norte (RN) and to discuss the environmental conditions for the establishment, expansion, and contraction of mangroves. Based on the samples collected from the cores (NAT 3 AND NAT 5) to study palynological groups, data from the optical space (Landsat), sedimentary facies and multi-proxy analysis (δ13C, δ15N, TOC, TN, C:N ratio), synchronized with three 14C dating ages. The main result of this research was the succession of mangroves, divided into three palynological phrases that suggest the development of three facies associations: (1) tidal channel and (2) vegetated plain - herbs/mangrove (3) herbaceous plain. The first phase between at least ~ 4500 and ~ 2915 cal yr BP was colonized by herbs, palms, and trees and shrubs on the bank of the estuary and by mangroves, of the Laguncularia type, followed by Avicennia and Rhizophora. With dissolved organic carbon, C3 terrestrial plants influence organic matter with δ13C values between -29.7 ‰ and -26.8‰, δ15N with x̅ = 3.8‰ and C:N values around 21.2. The second phase between ~2915 and ~660 cal yr BP characterized by the establishment of the mixed tidal plain dominated by herbaceous vegetation and by the expansion of mangroves represented by Rhizophora pollen between ~2915 cal yr BP and 2814 ± 29 cal yr BP with the increase of plants C3 and dissolved organic matter (COD) in fresh/estuarine water (δ13C x̅ = -26.9 and -29.4‰; δ15N x̅ = 3.86 and C:N around 12.3). The third phase is marked by a mangrove retraction evidenced by the decrease in Laguncularia, followed by Avicennia and Rhizophora, the dissolved organic matter had a greater influence of freshwater/estuary, and terrestrial plants (C3 plants) during the last 699 ± 35 cal yr BP. Near the surface (<15 cm) Rhizophora pollen occurs, indicating the establishment of this genus in recent decades, under modern environmental conditions (δ13C x̅ = -29 and -28.8‰; δ15N x̅ = 2.55 and C:N around 24.5 ). The data obtained in the isotopic and elementary analyzes indicate sedimentary organic matter of terrestrial origin, with the presence of C3 photosynthetic cycle plants, suffering a possible aquatic and estuarine influence, however, in the sedimentary sequences formed by lenticular heterolytic deposits to be correlated with the absence and decrease of mangrove vegetation in both cores. The data from the space-time analysis indicated an expansion of the area of mangroves, so this variation in the dynamics of mangroves can be directly linked to climate changes and the relative sea level at current levels and during the last three decades.
Acesso aberto (Open Access)
Os efeitos da subida do nível do mar sobre os manguezais do litoral sul da Bahia durante o Holoceno
(Universidade Federal do Pará, 2015-03-25) FONTES, Neuza Araújo; COHEN, Marcelo Cancela Lisboa; http://lattes.cnpq.br/8809787145146228
This work integrates the palinological, sedimentological and geomorphological data with radiocarbon dating, as well as δ13C and C/N from the sedimentary organic matter to identify the impact of changes in sea level and climate during the Holocene in Jucuruçu River’s mangroves, near the city of Prado, South Bahia. A sediment core with 4.5 m depth was sampled from a fluvial valley, 23 km away from the modern coastline. The base of sediment core presents age of 7450 cal yrs BP. The data reveal two important phases characterized by 1) an estuarine system with tidal flats colonized by mangroves. Its sedimentary organic matter is mainly sourced from estuarine algae during the early and middle Holocene; and 2) in the second phase, the mangroves shrank and herbaceous vegetation expanded. The δ13C and C/N values show an increase in contribution of terrestrial C3 plants. These phases identified in this study are in agreement with the relative sea-level (RSL) rise during the early and middle Holocene, and its subsequent fall during the late Holocene. In addition, the influence of weather patterns proposed for Holocene may be identified throughout the studied sediment core. Probably, changes in depositional environment and dominant vegetation at the study site were caused by the combined action of changes in RSL and fluvial discharge. According to the model proposed in this work, during the early and middle Holocene occurred a RSL rise that caused a marine incursion along the studied fluvial valley. The dry period occurred during the early and middle Holocene produced a decrease in the fluvial discharge and contributed to this marine transgression. However, during the late Holocene occurred a RSL fall and a wet period. It favored the marine regression and consequently, the mangroves migrated to tidal flats attached to the edge of lagoons near the modern coastline. The geomorphologic and vegetation evolution is in agreement with the mid-Holocene RSL maximum above present RSL and subsequent fall to the present time. Keywords: climate; Holocene; relative sea-level; South of Bahia; vegetation.
Acesso aberto (Open Access)
Environmental changes in the western Amazônia: morphological framewor, geochemistry, palynology and radiocarbon dating data
(2011-09) HORBE, Adriana Maria Coimbra; BEHLING, Hermann; NOGUEIRA, Afonso César Rodrigues; MAPES, Russell
The sediments from the Coari lake, a “terra firme” lake sculpted into Plio-Pleistocene deposits, and the Acará lake, a flooding-type lake developed on Quaternary sediments in the floodplain of the mid-Solimões river, in the western Amazônia, Brazil, were studied to investigate the environmental condition of their developing. This study includes mineral composition, geochemistry, Pb isotope, palinology, radiocarbon-age and morphological framework of the lakes obtained from SRTM satellite images. The geological and the environmental conditions in the two lakes are highly variable and suggest that their evolution reflect autogenic processes under humid rainforest condition. Although kaolinite, quartz, muscovite, illite, and smectite are the main minerals in both lakes, the geochemistry indicates distinct source, the Acará lake sediments have higher concentrations of Al2O3, Fe2O3, FeO, CaO, K2O, MgO, Na2O, P2O5, Ba, V, Cu, Ni, Zn, Pb, Sr, Li, Y and La and have more radiogenic Pb than the Coari lake sediments. The radiocarbon ages suggest that at 10160 yr BP the Coari lake started to be developed due to avulsion of the Solimões river, and the Acará lake was formed by the meander abandonment of Solimões river retaining its grass dominated shore at ca. 3710 yr BP.
Acesso aberto (Open Access)
Estratigrafia de dunas costeiras de Salinópolis/PA em associação com variações pluviométricas
(Universidade Federal do Pará, 2010-09-24) LEITE, Wladson da Silva; SOUZA FILHO, Pedro Walfir Martins e; http://lattes.cnpq.br/3282736820907252; ASP NETO, Nils Edvin; http://lattes.cnpq.br/7113886150130994
The present study was carried out at Salinópolis covering the Atalaia and Maçarico beaches (PA/North Brazil) to obtain a morpho-stratigraphic overview of the local coastal dunes and their evolution in Late Holocene, considering also climatic oscillations. Ground Penetrating Radar (GPR), auger coring, granulometric analysis and dating were used. The GPR-system SIR-2000 with a 400MHz antenna was used to reveal dune stratigraphy, including sedimentary facies and reactivation surfaces. At key-points of profiles sediment cores were obtained to proper interpretation of radargrams and sediment samples collection for grain size analysis and optical dating. At the Maçarico beach two main foredune crests were identified and dated at 69 and 80 years B.P. revealing a progradation rate of around 6 meters/year. The Atalaia beach presented a transgressive scenario, including retrogradation of the Holocene beach over older sediment layers, which include a feature interpreted as of Pleistocene age, although optical dating indicates an age of only 58 years B.P. due to actual sun light exposition. There, a parabolic dune was investigated and had revealed a migration rate of around 4 meters/year, where the reflectors indicate annual episodes of migration, possibly corresponding to the seasonal cycles of dryer periods and stronger winds. The general stratigraphy of the area seems to be a good tool for further studies on climate for the region, due to its good correlation with seasonal climatic patterns and long term register.
Acesso aberto (Open Access)
A evolução dos manguezais nos litorais Nordeste e Sul brasileiros durante o Holoceno
(Universidade Federal do Pará, 2020-09-30) FREIRE, Neuza Araújo Fontes; COHEN, Marcelo Cancela Lisboa; http://lattes.cnpq.br/8809787145146228
It is possible that climate changes and sea level fluctuations (allogenic processes) are and will cause major changes in mangrove dynamics. However, other driving forces may be significantly affecting this system. Distinguishing allogenic and autogenic influence on mangroves is a challenging question, because mechanisms related to the natural dynamics of depositional environments (autogenic processes) have strong influences on the establishment and degradation of mangroves. Thus, impacts on mangroves caused by autogenic processes may be erroneously attributed to allogenic mechanisms. Therefore, it is imperative to identify the ‘fingerprint’ of global changes in modern mangrove dynamics. This thesis integrates palynological, geochemical, sedimentological data, 14C dating of sedimentary organic matter, geomorphological and vegetation data in order to evaluate the influence of autogenic and allogeneic processes on Brazilian mangroves during the Holocene. Tropical estuaries from Rio Grande do Norte and southern Bahia, and subtropical estuaries in northern and southern Santa Catarina estates with different climatic, geomorphological and oceanographic characteristics were studied. The Relative Sea-Level (RSL) along the Rio Grande do Norte reached modern level and stabilized at about 7,000 cal yr BP, allowing the mangrove establishment at the edges of the Ceará-Mirim River estuary until the nowadays. However, changes in the spatial distribution of mangroves have occurred since then due to channels dynamics in the region (autogenic processes). Considering the mangroves of the Jucuruçu River in southern Bahia, their horizontal and vertical distribution were controlled by the interactions of the changes in the RSL and fluvial discharge. Therefore, the dynamics of these estuarine mangroves during the Holocene was mainly controlled by changes in sea level and precipitation that affected fluvial discharge. These allogeneic mechanisms were the main drivers of the dynamics of these mangroves. However, during the last 600 years, factors intrinsic to the depositional system gained relevance by controlling the establishment and migration of mangroves by deposition and erosion of muddy tidal flats, abandonment and reactivation of channels (autogenic processes). In the case of Santa Catarina mangroves, the RSL rise up to the middle Holocene was decisive for the establishment of tidal flats appropriate for the expansion of saltmarshes. However, mangroves did not tolerate the Holocene low temperatures in the southern littoral of Santa Catarina. The pollen data indicate the establishment of mangroves with Laguncularia around 1,700 cal yr BP, followed by Avicennia and lastly Rhizophora trees, a cold less tolerant genus, around 650 cal yr BP in São Francisco do Sul, north of Santa Catarina. The mangroves of Laguna, south of Santa Catarina, composed of Laguncularia and Avicennia, were established in the current southern limit of the South American mangroves only in the last decades. No evidence was found for the presence of mangroves in Laguna during the Holocene. The establishment of these mangroves in the region probably started during the Anthropocene, as a consequence of the increase in minimum winter temperatures in southern Brazil. Considering changes in precipitation rates over drainage basins that feed mangrove estuaries, as well as trends in RSL rise and temperatures until the end of the 21st century, tropical estuarine mangroves will likely migrate to higher topographically sectors in the interior of the river valleys, where its extension will depend on the volume of river discharge interacting with the RSL rise. Subtropical mangroves are expected to expand to more temperate zones as minimum winter temperatures increase. This process should cause an increase in the diversity of mangrove species, such as the introduction of the Rhizophora genus in the current southern limit of the mangroves, positioned in Laguna-SC. However, in the case of high rates of RSL rise, the relatively new subtropical mangroves are also expected to migrate to topographically higher sectors of the coast.
Acesso aberto (Open Access)
Geomorfologia, mudanças na fonte de matéria orgânica e vegetação em planícies de maré próximas a foz do rio Amazonas durante o Holoceno
(Universidade Federal do Pará, 2011-11-11) GUIMARÃES, José Tasso Felix; COHEN, Marcelo Cancela Lisboa; http://lattes.cnpq.br/8809787145146228; 8809787145146228
Geomorphological data, sedimentary facies, pollen, spores, carbon and nitrogen isotopes records, C/N ratio and radiocarbon dates allowed the identification and discussion about the relationship between the main morphological process, climatic signals and its influence on vegetation patterns of tidal flats near the mouth of the Amazon River during the last 5500 cal yr B.P. Therefore, data from the margin of Amazon River (Macapa site) indicate marine influence related to mangrove presence over a tidal mud flat between 5560 - 5470 cal yr BP and 5290 - 5150 cal yr BP. Afterward, the mangrove area shrank following the return of more humid conditions and increase of Amazon River discharge. A common reworking process of the tidal flat through the lateral migration of a meandering creek occurred in the study site, with later development of transitional vegetation under freshwater influence. Following the natural vegetation succession under stable climate and hydrological conditions, the expansion of varzea forests occurred since 600 - 560 cal yr BP until the present. Furthermore, regarding the tidal flats located west of the mouth of Amazon River (Amapa site), these stable conditions also allowed the mangrove maintenance over mudflats with deposition of marine organic matter during at least the last 2350 - 2300 cal yr BP. Processing and interpretation methods in optical and synthetic aperture radar (SAR) images, data of water salinity, maximum height of flood, historical rain series and sedimentary facies were used in the analysis of the morphological and geobotanical units, and its short-term changes to understand the main processes acting on the tidal flats downdrift of the Amazon River mouth (Calcoene site) during the last 30 years. Thus, the study area was subdivided in two main compartments: coastal plain and plateau. The coastal plateau presents a flat to gently undulated surface shaped by erosive process. Avulsion of alluvial channel and birdfoot feature possibly related to six deltaic lobes were also identified in this compartment. The vegetation is represented by varzea (flooded freshwater forests) and savannah. The coastal plain has an average length of 10 km, and it presents the tidal-fluvial channel, paleochannels, lakes, varzea, inundated field (herbaceous field), mangrove, chenier ridges, elongated tidal mud bars, tidal mud and mixed flat (non-vegetated). The sedimentary facies indicate tide and wave-dominated environments. The presence of lakes and lake belts, coexistence of herbaceous field and mangrove in the coastal plain may be related to silting and abandonment of tidal channels. The temporal analysis of these features indicates the savannah contraction, expansion of varzea and mangrove areas and formation of extensive mud tidal flats during drier period under the influence of El Nino. The wetter period under the influence of La Nina probably allowed the increase of varzea and lakes over the savannah areas, and the expansion of mangrove. Therefore, the decrease of rainfall index during El Nino may have reduced the Calcoene River inflow and favored an increase of tidal propagation, transport and deposition of mud along the tidal-fluvial channel and its secondary channels with subsequent development of mangrove and stabilization of muddy substrate near the coastline in La Nina. Considering a longer time scale during the mid and late Holocene, the analysis of morphology, sedimentary facies, palynological, carbon and nitrogen isotopes, C/N and radiocarbon data from tidal flats in the Calcoene site, indicates that vegetation development during the mid and late Holocene occurred influenced by the interaction relative sea-level and tidal channel dynamic. The data indicate a mud-rich tidal flat that presents alternations between supra and intertidal environments. The proximal portion of the tidal flat is related to the transitional sector between the costal plateau and plain and represents the final filling stage of the concave-up feature formed by the abandoned channel that contributed to water accumulation under very low energy flows, fern and other terrestrial vegetation establishment surrounding the formed lake since 5280 - 5160 cal yr BP. During the last 2840 - 2750 cal yr BP, the source of mud ceased and autochthonous organic material became prevalent as well as the increase in contribution of terrestrial organic matter (C3 plants), mainly represented by varzea vegetation. Herbaceous field already colonized the tidal flat at least during the last 3170 - 2970 cal yr BP. However, part of distal portion of the tidal flat related to the herbaceous field was covered by chenier ridges between 3170-2970 and 220-140 cal yr BP. The mangrove establishment, characterized by estuarine organic matter, Rhizophora and Avicennia pollen, occurred after 1350-1290 cal yr B.P and 220-140 cal yr B.P. on G3 and G2 site, respectively. This stacking pattern of sediments indicating a retrogradation, with distal facies over proximal facies, and gradual transition of herbaceous to mangrove sediment (e.g. G3 site) suggesting that the creation of accommodation space may be produced during an increase of wave action, tidal inundation frequency and evolution of secondary channels in the study site as a result of progressive relative sea-level rise. The integration of all these data suggests that the morphological process, vegetation patterns and sources of organic matter from tidal flats of Calcoene, Amapa and Macapa sites was influenced and conditioned by the interaction between relative sea-level, climatic and hydrological changes, and tidal channel dynamic during the Holocene.
Acesso aberto (Open Access)
Impacto do último máximo glacial pleistocênico na vegetação de Humaitá, Amazonas
(Universidade Federal do Pará, 2016-09-27) LIMA JÚNIOR, Walmir de Jesus Sousa; COHEN, Marcelo Cancela Lisboa; http://lattes.cnpq.br/8809787145146228
The amount of pollen data recovered from the sedimentary record of western Amazonia is still far from adequate to fully approach climate changes in this region over the Last Glacial period. In the present work, vegetation dynamics of western Amazonia during the past 42000 cal yr BP is analyzed in the context of previous and new pollen data. Two sediment cores were sampled from fluvial terraces of the Madeira River, a major southern Amazonian tributary. The study sites are covered by tropical rainforest vegetation. The sedimentary deposits consist mostly of massive sand, heterolithic bedded sand/mud as well as either laminated or massive mud. These deposits were formed under reducing and low energy conditions in an abandoned fluvial channel/lake environment. Such depositional setting favored the preservation of a pollen community suggestive of arboreous taxa common to the modern Amazonian rainforest mixed with herbaceous vegetation. Pollen analysis also recorded a significant proportion of cold-adapted Andean tree species, represented by Alnus (0-20%), Hedyosmum (1-15%), Podocarpus (0-5%), Illex (1-11%) and Weinmannia (0-1%) at least between > 42,000 cal yr BP and 10,300 cal yr BP. During the Holocene, only pollen representative of herbs and modern Amazon vegetation persisted. This new pollen record confirm previous multiple proxies analyzes of two sediment cores sampled also from Humaitá region, where a significant plant population, at present restricted to Andean areas located at altitudes higher than 2000 - 3000 m, in areas of the Amazonia lowland toward the onset, and probably, during the Last Glacial Maximum.
Acesso aberto (Open Access)
A influência marinha nas águas do lago Arari (ilha de Marajó-Pa) durante o Holoceno com base em indicadores biológicos e isotópicos.
(Universidade Federal do Pará, 2011-03-14) SMITH, Clarisse Beltrão; COHEN, Marcelo Cancela Lisboa; http://lattes.cnpq.br/8809787145146228; 8809787145146228
This work aimed the paleoenvironmental reconstruct of the drainage basin area of the Lake Arari (Marajó Island-PA) during the last 7.250 yr B.P. There was performed the characterization of environment study, determining the current physico-chemical data of lake water and their botanical composition (phytoplankton and macrophytes). From the nine sediment cores sampled from the Lake Arari, herbaceous plain, and on the east coast of the Marajó Island, were analyzed the grains size, sedimentary structures, pollen, isotopic (_15N and _ 13C) and elemental (C/Nmolar) content that allowed the lito, bio and chemostratigraphy correlation between the sampling sites. The ages of events were determined by radiocarbon. The integrated analysis of these data allowed the identification of three phases: Phase 1, from 7.328-7.168 and 2.306-2.234 cal. yr B.P., the sediments are classified as clayey silt and sandy silt, showing predominantly lenticular and wavy structures with mangrove pollen and values of C/N molar ratio and _ 13C _ 15N compatible with a lagoonal depositional environment. In Phase 2, from 2.306-2.234 to ~500 cal. yr B.P., occurs a decrease in the energy flow, the sedimentary deposits present parallel lamination structure or massive deposits. Although the pollen data indicate the absence of mangroves in this phase, the isotope and elemental values continue to indicate preferential contribution of aquatic marine organic matter. In phase 3, from ~500 cal. yr B.P. to modern, is established the lake system, because the sediment deposition reflects relatively low energy flow and marine influence becomes progressively smaller with larger contribution of freshwater algae. Besides, occurs a slight increase in organic matter derived from terrestrial plants due to the expansion of the herbaceous plain, which it colonizes the Arari Lake's drainage. Currently the mangrove forests are restricted to east littoral area of the Marajó Island. According to the model proposed in this work, the decrease in marine influence, with consequences for the hydrodynamics, organic matter and vegetation of the study area, was produced by the interaction between the sea-level rise and river water discharge.
Acesso aberto (Open Access)
Influências das flutuações do nível do mar e mudanças climáticas na dinâmica dos manguezais do litoral Sul de Santa Catarina durante o Holoceno.
(Universidade Federal do Pará, 2019-06-10) ROCHA, Denise Oliveira Souza; COHEN, Marcelo Cancela Lisboa; http://lattes.cnpq.br/8809787145146228
The objective of this work was to identify the main factors controlling the mangrove dynamics in the southern limit of this ecosystem in the South American continent, in the Laguna - Santa Catarina region. This study was based on the integration of sedimentary facies, isotopes (δ13C and δ15N), elementary organic matter (C/N), and pollen data with 14C dates obtained from core RP4 (S 28°29'18.41 " and W 48°50'47.01) with 2 meters depth sampled from a tidal flat near the Santo Antônio Lagoon, 8 km away from the present coastline, west of the town of Laguna. Three facies associations were identified: facies Herbaceous Floodplain, Fluvial channel and tidal flat with Spartina. The Herbaceous Floodplain is characterized by massive mud with benthic tubes, fragments of shells and roots. The facies association of Fluvial Channel presents sand with crossed stratification and massive. The top of the studied core presents the facies association Tidal Flat with Spartina represented by mud silt with roots fragments. The integration of these data suggests an increase in the relative sea-level during the Holocene, when the low river courses were flooded and it favored the formation of lagoon systems that are well represented along the Santa Catarina littoral, especially in the study area. A gradual Holocene marine transgression would have favored the mangrove expansion on tidal flat flats. Considering the physicochemical and hydrodynamic, probably the sedimentary environment was favorable for the establishment and expansion of mangroves over the last centuries, when occurs a strong contribution of organic matter sourced from estuary in the study site and development of tidal flats. The absence of mangrove pollen grains along the studied core (<9000 years AP) indicates, besides the low relative sea-level stand, another factor must have prevented mangrove establishment in the study area. The presence of Laguncularia and Avicennia shrubs/trees nowadays in the study area and the absence of mangrove pollen grains in the studied stratigraphic profile indicates that these genus were established only during the last decades. Probably, the temperatures during the Holocene winters on the modern austral limit of the South American mangroves prevented the mangrove establishment during that period the sediments of the core RP4 were accumulated. Probably, the increase in minimum winter temperatures during the last decades has allowed the expansion of the southern limit of the southern American mangroves into temperate zones.
Acesso aberto (Open Access)
Paleografia e evolução da paisagem do nordeste do estado do Pará e noroeste do Maranhão: cretáceo ao holoceno
(Universidade Federal do Pará, 2002-02-28) SOARES JUNIOR, Adilson Viana; COSTA, João Batista Sena; http://lattes.cnpq.br/0141806217745286
This research presents some aspects of the tectonics and paeleogeographic evolution of northeastem region of Pará State and northwestem region of Maranhão State in the northem Brazil, based on the integration of structural, tectonic, stratigraphic, sedimentological and paeleontological data. The Marajó basin is elongated in a NW-SE direction and includes a sedimentary sequence deposited ffom Upper Cretaceous to Upper Tertiary. The geometry of the Marajó Basin is characterised by NW-SE normal faults in the northwest-southeast direction and NE-SW and ENE-WSW strike-slip faults, which define the boundaries ofthe Mexiana, Limoeiro, Cametá and Mocajuba sub-basins. The Gurupi Graben System encompasses the Bragança-Viseu, São Luís and Ilha Nova basins, with Cretaceous and Tertiary sedimentary filling. The Bragança-Viseu Basin is formed by two assymmetric grabens - the Caeté depocenter (close to the northem border) and the Piriá depocenter, close to the southem limit - in a NW-SE direction, separated by a transcurrent fault. The São Luís Basin comprises three sub-basins: Maracaçumé, in the northwest, Bacuri, in the northeast, and Bequimão, toward the southeast. The Ilha Nova basin is divided into two halfgrabens separated by a transcurrent fault. The westem half-graben presents antithetic faults in the southem and northem borders, while these faults ocurr only in its northem extreme ofthe eastem halfgraben. The Grajaú Basin is an extensional feature of the Cretaceous, generated by normal fault propagation towards the continent interior, during the opening ofthe Equatorial Atlantic, and by partial reactivation of the Paleozoic structures of the Pamaíba basin. The stratigraphy is composed ofthe Grajaú, Codó and Itapecurú formations, controled by N-S planar normal faults, diping to the west, and linked through NE-SW transcurrent faults. The Gurupá Are strikes NW-SE, correspond to the boundary ofthe Amazon Basin, and defines the shoulder ofthe Marajó basin, closely associated with listric faults. Northem Marajó encompasses the region between the northeastem shoulder of the Marajó Basin and the Pará/Ilha de Santana Platform, and is characterised by neotectonic structures represented by NE-SW transcurrent faults, as those that control the mouth of the Tocantins river towards the northeast. 4 The Tocantins Are is a positive feature that bounds the Marajó and Grajaú basins, and corresponds to a transpressive region. The Gurupi Are is a positive feature that limits the Bragança-Viseu and São Luís basins, running in a NNE-SSW direction, and worked as an area wich accomodated high strain during the Cretaceous. The Ferrer-Urbano Santos Are is an E-W positive feature that limits the São Luís and Grajaú basins formed during the Cretaceous, with an axis of uplifting that migrated southwards through the time. The partial collapse ofthis are evolved to the São Luís Basin. The Tiracambú Hills derived from Grajaú Basin inversion, since the Paleocene, wich resulted in the propagation ofE-W transcurrent dextral systems and was followed by the tectonic calm that originated the mature lateritic profile. The Estrondo Hills is related to N-W normal faults, and is interpreted as derived by reactivation of older struetures during the Cretaceous-Upper Tertiary extensional event, controlling the courses ofthe Araguaia and Tocantins rivers
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Variabilidade espacial e temporal do manguezal em um estuário subtropical, baía da Babitonga, sul do Brasil
(Universidade Federal do Pará, 2022-12-31) TORRES, Angela Esmeralda Cely; FRANÇA, Marlon Carlos; http://lattes.cnpq.br/8225311897488790; https://orcid.org/0000-0002-3784-7702
Mangroves are indicator ecosystems that respond to global changes in tropical and subtropical regions around the world. Climate changes and variations in sea level significantly influenced mangroves during the Holocene along the Brazilian coast. Here we study mangroves established near the southernmost limit of South America (28°S). Our study is based on a core obtained in the region of the Palmital channel – Baía da Babitonga, State of Santa Catarina (SC), Brazil. Sedimentary, pollen, geomorphological and vegetation analyzes allowed the paleoenvironmental reconstitution during the Late Holocene. The three facies associations found indicated a progradational succession where a tidal plain was developed on the estuary margin. During the first phase, from at least 1440 to ±1286 cal years BP, there was a sandy infratidal plain in the study area. Initially, there were no records of mangroves, but Laguncularia pollen grains were identified from ±1390 cal years BP, indicating that in the region surrounding the collection point, conditions became favorable for the development of the mangroves. After ±1286 cal years BP, the tidal flat developed reaching the present coastline, favored by the stabilization of the relative sea level. Avicennia trees were established on the tidal flat from ±1273 cal years BP. Finally, Rhizophora trees have been established during the last few decades. Probably, the mangrove succession found was favored by climatic conditions related to the increase in temperature during the late Holocene that has caused a migration from the southern limit of the mangrove to the south of the subtropical zone. Modern space-time analysis revealed a recent decrease in mangrove area of ±107 ha between 1986 (4115 Ha) and 2021 (4008 ha). The greatest loss is located in the coastal zone close to the city of Joinville (SC), mainly related to urban expansion. A slight expansion of the mangrove upstream of the channels was observed, which may be related to changes in the relative level of the modern sea and the gradual increase in minimum temperatures in southern Brazil.