Navegando por Assunto "Palinologia"

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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.
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Dinâmica da vegetação da região de Humaitá - AM durante o Pleistoceno tardio e o Holoceno
(Universidade Federal do Pará, 2013-01-30) FRIAES, Yuri Souza; COHEN, Marcelo Cancela Lisboa; http://lattes.cnpq.br/8809787145146228
Vegetation dynamics of Western Amazonia during the past 42000 cal yr BP was studied by pollen, sedimentary facies, 14C dating δ13C and C/N. Two sediment cores were sampled from Humaitá in southern Amazonas state, and Porto Velho, northern Rondônia. These sites, located in western Brazilian Amazonia, are covered by grassland and tropical rainforest vegetation, respectively. The sedimentary deposits are predominantly composed of massive sand, heterolithic mud/sand, and laminated or massive mud representative of sediment accumulation in floodplain, active channel, abandoned channel, and oxbow lake sedimentary environments. In these settings, reducing and low energy subaqueous conditions were developed, locally favoring preservation of a pollen community of herbaceous vegetation and glacial forest represented mainly by Alnus, Drymis, Hedyosmum, Podocarpus, and Weinmannia trees at least between > 42,033 – 43,168 cal yr BP and <34,804 – 35,584 cal yr BP. The herbaceous and arboreal vegetation ecotone persisted from the early to mid-Holocene, whilst the cold pollen assemblage became extinct. In this work, we record 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 of the Last Glacial Maximum. This suggests that this time interval might have seen temperatures lower than previously proposed for this region.
Acesso aberto (Open Access)
dinâmica da vegetação durante o quaternário tardio no limite continental da península bragantina, litoral amazônico
(Universidade Federal do Pará, 2022-11-25) MACIEL, Giordana Leticia Monteiro; ASP NETO, Nils Edvin; http://lattes.cnpq.br/7113886150130994; https://orcid.org/0000-0002-6468-6158; FRANÇA, Marlon Carlos; http://lattes.cnpq.br/8225311897488790; https://orcid.org/0000-0002-3784-7702
The eastern Amazonian region is dominated and shaped by a macrotidal regime, harboring environments such as muddy plains colonized by mangroves, estuaries associated with tidal channels, floodplains, and macrotidal beaches, among others. To understand the vegetation dynamics and carry out the paleoenvironmental reconstitution in an Amazonian floodplain, palynological, sedimentary, and C-14 dating data were integrated based on a subsurface sedimentary profile collected in the region of the Taperaçu’s herbaceous fields, in the Bragança peninsula (PA), on the Amazon coast. The present study identified three fácies associations and four pollen zones that occurred during the Late Pleistocene and Holocene. The first facies association is defined as an alluvial deposit, which presented pelite facies, flaser heterolithic bedding with a coarsening upward sequence. The vegetation was predominantly typical of trees and shrubs, marked by the presence of Rubiaceae, Agavaceae, and Annonaceae families and with low herbaceous vegetation dominated by the Araceae family developed around 41,200- 39,975 cal years BP. The second facies association identified showed typical characteristics of a tidal channel, with a well-delimited erosive surface, which marks a transition in the processes operating over this environment; it comprises gravel, massive sand, and wavy-marked mud facies. Toward the Taperaçu’s tidal channel, herbaceous vegetation was developed, represented by Cyperaceae and Ulmaceae, and the presence of trees and shrubs, such as Arecaceae, Malphighiaceae, and Rubiaceae. During the early and mid-Holocene (6000-5915 cal years BP), at a depth of 6.45 m from the surface, the results revealed the formation of a tidal flat. The main pollen result during this phase was the establishment of mangroves, colonized by Rhizophora and Avicennia, in addition to the presence of herbaceous vegetation, which currently occupies the studied region, marking the late Holocene.
Acesso aberto (Open Access)
A dinâmica da vegetação nas planícies de maré do delta do rio Doce durante o holoceno tardio.
(Universidade Federal do Pará, 2019-08-31) CARVALHO, Victor Rocha; FRANÇA, Marlon Carlos; http://lattes.cnpq.br/8225311897488790
The goal of this work was to study the vegetation dynamics on the tidal plain of the Doce River Delta – southeastern Brazil – under the climate change influence and relative sea-level change during the late Holocene (2350 cal yr BP). Thus, 14C dating, sedimentary features, and pollen date, obtained from two cores denominated URU1 (0.5 m depth) and URU2 (4 m depth), sampled with a peat sampler were used. The cores presented four typical sedimentary facies of tidal plain: i) Flaser heterolithic bedding (Hf); ii) Wavyheterolithic bedding; iii) Lenticular heterolithic bedding (Hl) and iv) Parallel mud (Mp). The pollen analysis of URU1 showed herbs predominance, trees and shrubs in all intervals, besides rising of aquatic vegetation towards surface. The URU2 core showed a mangrove and foraminifera influence close to the bottom and middle depth, possibly due to a higher marine/estuarine influence until 2250 cal yr BP. However, close to the surface of this core, occurred a mangrove and foraminifera decrease, followed by freshwater aquatic vegetation increasing, indicating a decrease in the marine influence. This can be a result of a relatively humid climate since at least 2250 cal y BP, which resulted in higher rainfall and flow of rivers. Furthermore, the palynological data shows anthropic or natural alterations that occurred after 2250 cal yr BP demonstrated decreased coverage of palm trees in the tidal plain, further of a higher presence of Cecropia and Typha angustifolia pollen. Therefore, an increase of freshwater flow and wet climate conditions since at least 2000 cal yr BP, has been decisive for increasing sediment transport by the rivers to the delta plain, resulting in a coastline increase, leading coastal progradation, which resulted in replace process between mangroves and herbaceous vegetation.
Acesso aberto (Open Access)
A dinâmica das florestas alagadas durante o holoceno no litoral de Calçoene, Amapá
(Universidade Federal do Pará, 2008-02-25) GUIMARÃES, José Tasso Felix; COHEN, Marcelo Cancela Lisboa; http://lattes.cnpq.br/8809787145146228
The integration of palynological and spectrophometric data with radiocarbon dating of sediment cores has allowed to propose developing model and vegetation dynamic according to climatic and relative sea-level changes during the Late Holocene in the Calçoene Coastal Plain- Amapá. Thus, this work suggests three periods characterized by marine influence between 2000- 800, 500-300, e 80 years BP - modern, as well as, two fluvial periods between 800-500 years BP and 300-80 years BP. The analysis of current patterns of geobotanical units distribution and palaeovegetation indicate a mangrove (311 Km 2 ) and várzea forest (684 Km 2 ) migration on inundated field (1.021 Km 2 ) positioned in elevated topographically areas of this coastal plain, which may be related to a local relative sea-level rise.
Acesso aberto (Open Access)
A dinâmica dos manguezais subtropicais no litoral norte de Santa Catarina durante o Holoceno tardio.
(Universidade Federal do Pará, 2019-06-28) PINHEIRO, Vanessa da Conceição; FRANÇA, Marlon Carlos; http://lattes.cnpq.br/8225311897488790
The goal of this work is identifying the establishment and expansion of mangroves on the northern coast of Santa Catarina during the Late Holocene. For this work, pollen data, 14C dating, organic geochemical (δ13C, C:N, TN and TOC) and results of sedimentary analyzes were integrated. These data were obtained from the analyses carried out from two sedimentary cores (SF7 and SF8) collected using a Russian sampler in the Babitonga Bay, northern coast of Santa Catarina. The data reveals a typical tidal channel and tidal plain deposits throughout the records. The tidal channel deposit was accumulated between > 1692 cal yr BP to ~ 667 cal yr BP, close to the bottom of the cores. This deposit is formed by fine-to-medium sand with parallel laminated sand (Sp facies), cross lamination (facies Sc), low angle planar lamination (Sb facies) and massive sand (Sm facies). The sedimentary deposit is characterized as a tidal plain around ~ 1223 cal yr BP, constituted by facies flaser heterolithic bedding (Hf), wavy heterolithic bedding (Hw), lenticular heterolithic bedding (H1) and parallel mud (Mp). The pollen content preserved along the tidal channel deposits reveals predominance of trees, shrubs, herbs and palms surroundings of the channel and on topographically higher regions. Only SF8 core was found mangroves pollen while the isotopic data revealed δ13C (-24.4 to -21.47 ‰), C/N ratio (4.77 to 20.81) with a strong contribution of marine organic matter and C3 terrestrial plants. The tidal channel was clogged and allowed the beginning of the deposition of the tidal plain. The deposit of the tidal plain has a large amount of plants fragments and pollen content characterized by predominance of herbs, trees, shrubs, palms and mangroves. The results of δ13C (-22.48 to -21.18 ‰) and C:N ratio (11.49 to 19.89) indicated the contribution of C3 terrestrial plants as well as contribution of marine organic matter. In addition, the mangroves beginning from approximately ~1692 cal yr BP with the genus Laguncularia and Avicennia, still at the edge of the tidal channel. Around ~586 cal yr BP was observed the mangrove development with a Rhizophora genus. The Laguncularia and Avicennia were initially established in sandy substrates and then also occupied in silty sandy soil. In the tidal plain environment, the genus Rhizophora was established in mud substrate. The mangroves of this region settled in the topographically higher regions and later expanded to the lower and closest regions of the Babitonga bay, possibly due to the decrease of the relative sea level recorded during the late Holocene as well as the migration and filling of the tidal channels. The occurrence of Rhizophora pollen close to the surface probably was a result of the temperature rise during the Late Holocene.
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)
Efeitos das mudanças climáticas nos limites austral e boreal dos manguezais americanos durante o Holoceno e Antropoceno
(Universidade Federal do Pará, 2021-09-08) RODRIGUES, Érika do Socorro Ferreira; KAM, Biu Liu; COHEN, Marcelo Cancela Lisboa; http://lattes.cnpq.br/8809787145146228
During the Holocene, mangrove distributions were primarily controlled by climate change and sea level fluctuations. In particular, low winter temperatures in the subtropical coastal areas limited these ecosystems to expand beyond 30°N and 28°S in the North and South Hemisphere. Therefore, under the continuous warming trend during the Anthropocene, mangroves are expected to migrate to more temperate regions previously occupied by saltmarshes (e.g., Spartina sp.). The purpose of this Thesis is evaluate the effects of climate changes and SLR fluctuations on the distribution of American mangroves along the Holocene and Anthropocene, based on satellite and drone images, sedimentary facies, diatoms, pollen, geochemistry (LOI, XRF, TOC , TN, TS, C: N, C: S, δ13C and δ15N) as well 210Pb and 14C datings .To achieve the aforementioned objectives, studies were conducted on the tropical coast of southeastern Brazil - south of the Espírito Santo State (20°41'S), the subtropical coastal regions located on the north (26°6'S) and south (28°29’ S) coast of Santa Catarina, and Louisiana littoral (29° 09' N). The results of this research are presented in four scientific papers. The first one (see, chapter II) deals with the effects of global warming on the establishment of mangroves in the Louisiana littoral (29° 09’ N) during the Holocene. The second scientific paper (see, chapter III) shows southward migration of the austral limit mangroves in South America, according to the increase in minimum winter temperatures in the Anthropocene (southern Santa Catarina coast, 28°29' S). The third manuscript (see, chapter IV) assesses the impacts of sea level rise on tropical mangroves in southeastern Brazil (southern Espírito Santo coast, 20°41'S) during the Holocene and Anthropocene, using a multi-proxy approach. The fourth scientific paper (see, chapter V) addresses the establishment of mangroves in the São Francisco do Sul Bay (north Santa Catarina coast , 26° 6'S), in response to global warming in the last 1000 years. The results indicated a marine transgression off the southern coast of Santa Catarina (28°29’ S) and the Louisiana littoral (29°09’ N) during early Holocene. This natural process converted a lake into lagoons colonized by herbs adapted to an estuarine environment. On the Brazilian tropical coast, the middle Holocene high sea-level stand (2-5 m above the current level) was decisive for the establishment of mangroves. This comportment was observed in an estuary located on the south coast of Espírito Santo (20°41'S) where a herbaceous plain was gradually replaced by a lagoon surrounded by mangroves between ~6300 cal yr BP and ~4650 cal yr BP. However, between ~ 4650 cal yr BP and 2700 cal yr BP the lagoon colonized by mangroves on its margins was converted to a tidal flat occupied by herbs, palms and trees/shrubs reflecting the reduction of estuarine influence in the late Holocene, according to with the fall and/or stabilization of the RSL. From the last thousand years there has been a significant decrease in the occurrence of mangrove pollen in the sediments of the tidal flats of southern Espirito Santo (390 cal yr BP (1560 AD) and 77 cal yr BP (1873 AD), probably caused by a RSL fall associated with Little Ice Age (LIA). Paleoclimatic studies have indicated temperature fluctuations during LIA (380 to 50 cal yr BP) and MCA – Medieval Warm Period (950 to 750 cal yr BP) in the late Holocene and consequent change in the Brazil southern vegetation. These climatic events probably influenced the appearance of the mangrove genera succession in the São Francisco do Sul Bay (north Santa Catarina coast, 26°6' S). The effects of the sea level fall and/or stabilization during late Holocene were recorded on the southern coast of Santa Catarina (Laguna, 28° 29 ′ S) through changes in coastal geomorphology. In this same period at the Louisiana coastline (29°09 ′ N), sandy sediments (overwash sediments) were deposited in these estuaries reflecting the gradual migration of these sediments towards land likely a result of storm events. The position of RSL on the southern Brazilian coast (Laguna, 28° 29 ′ S) and north american (Louisiana coast, 29° 09 ′ N) from the middle Holocene were the same presenting suitable physicochemical conditions for mangrove development, as occurred on the coast of Espírito Santo (~6300 cal yr BP) and São Francisco do Sul Bay (~1500 cal yr BP). However, no mangrove pollen grains were recorded in the sediments of the current austral (Laguna, 28° 29 ′ S) and boreal (Louisiana coast, 29° 09 ′ N) limit of American mangroves during the Holocene. During this time interval, there was a significant contribution of organic matter of estuarine source in tidal flats occupied by Spartina sp. Regarding to global warming and RSL rise during Anthropocene an increase mangrove pollen of Espírito Santo sedimentary cores (20° 40' S) reflected mangrove migration to topographically higher sandy plains previously dominated by herbaceous vegetation. Regarding Laguna mangroves (current southern limit of the American mangroves, 28° 29 ′ S), pollen analyzes, 14C and 210Pb datings indicated that the mangroves were established under estuarine influence between ~1957 and 1986 AD, represented by Laguncularia sp. trees. Spatio-temporal analyzes based on satellite and drone images indicated that mangroves have been expanding in recent decades with the introduction of new mangrove genera. In our study area in São Francisco do Sul Bay (north coast of Santa Catarina, 26°6' S), palynological analyzes and 14C dating revealed that mangroves were established around ~ 1500 cal yr BP represented by Laguncularia sp. followed by Avicennia sp. (~500 cal yr BP) and Rhizophora sp. in the last century. This mangrove succession genera were likely caused by a warming trend in South America during the late Holocene and Rhizophora sp. by warming during the Anthropocene. In relation to the mangroves located on the Louisiana littoral, historical records indicated the presence of small shrubs of Avicennia sp. at the beginning of the 20th century. Currently, remote sensing studies coordinated by Cohen (2021) indicate a latitudinal expansion of Avicennia sp. colonizing areas that were previously occupied by Spartina sp. after two decades of warm winters. Therefore, mangroves migrated from the tropics to temperate zones as winter minimum temperatures increased during the Holocene. The Laguna and Louisiana mangroves (currently South and North American mangroves limit) were only established in the early and mid-21st century, respectively. Such dynamics were likely caused by the natural global warming of the Holocene and intensified during the Anthropocene. This process also caused a RSL rise which resulted in the migration of mangrove from lowlands to new higher tidal flats.
Acesso aberto (Open Access)
Estabelecimento e expansão dos manguezais de Laguna-SC: efeito do aquecimento global ou resultado de processos sedimentares?
(Universidade Federal do Pará, 2018-03-19) SOARES, Jaine Freitas; COHEN, Marcelo Cancela Lisboa; http://lattes.cnpq.br/8809787145146228
The integration of pollen, isotopes (δ13C, δ15N, C/N), sedimentary features, 14C and 210Pb dating from four sediment cores (LAG-3, LAG-4,LAG-5 e LAG-6). Sampled from a sandbar at Santo Antônio Lagoon, Laguna City, Santa Catarina, allowed the paleoenviromental reconstruction of the last 900 years BP. The dates reveal two facies associations along these cores: (A) Sandbar, represented by massive sand (facies Sm), and (B) tidal flat, represented by lenticular heterolithic bedding (Hl) and wavy heterolithic bedding (Hw). The deposits of sand bar was accumulated between >940 e ~431 cal years BP, probably under influence of a stable relative sea level (RSL) or rise of RSL during the last 1000 years. The pollen data preserved along the sandbar phase indicate a predominance of trees, shrubs herbs and some palms originating from vegetation units surrounding the lagoon. The relation δ13C (-24‰ - 15‰) and C/N (6-30) of this facies association reveals a strong contribution of organic matter from marine algae and terrestrial plants C3 and C4. During the accumulation of tidal flat deposits, occurred during the last 60 years, there was the establishment mainly of Spartina with some spaced Laguncularias shurbs. The relation δ13C (-24‰ - 16‰) and C/N (7-22) reveals an origin of sedimentary organic matter similar to the period of sandbar deposits. Based on this data and distribution gradient of Spartina and on mangrove’s trees genus along the Santa Catarina coast, is reasonable to propose that the recent colonization of Laguncularia at region of Laguna has been caused by gradual increase in minimum winter temperatures observed during last 50 years. Whether the climatic trend is the main force driving the expansion of Laguncularia trees to southern Brazil, the surface of the sandybars and tidal flats of the lagoon margin of southern Brazil, now largely occupied by Spartina, will be gradually colonized and/or replaced not only by Laguncularia, but also by Avicennia, followed during the next years, by Rhizophora.
Acesso aberto (Open Access)
Estudo sistemático de gastrópodes neógenos, com ênfase ao gênero Tryonia (STIMPSON, 1865), Formação Solimões, Estado do Amazonas
(Universidade Federal do Pará, 2011-02-01) GUIMARÃES, Lívia Isadora de Almeida; RAMOS, Maria Inês Feijó; http://lattes.cnpq.br/4546620118003936
The Solimões Formation is a geologic unit composed of neogene deposits, situated in brazilian Western Amazonia. These deposits are correlated with Pebas (Peru and Colombia), Curaray (Ecuador) and Urumaco Formations (Venezuela), forming the Pebas system. The lithology of Solimões Formation is mainly composed of clay and sand. Regarding to the palaeoecology of the unit, the majority of previous papers point to a freshwater (fluviolacustrine) or brackish water environment. The Formation is also known for being richly fossiliferous, consisting of palinonology, vertebrate and invertebrate material, especially ostracods and mollusks. The studies about mollusks in this area are few, especially those one regarding to gastropods, which are remote. Therefore, this paper intents to contribute to the taxonomic study of gastropods from 1 AS 34-AM (on the Jutaí riverbank) borehole, as well as Morada Nova and Aquidabã outcrops (on the Juruá riverbank), in the Amazonas state, besides helping in the palaeoenvironmental and biostratigraphic interpretations of the study unit. The gastropod analyses of the outcrop samples allowed the register of ?Pachychilidae family and Onobops (Cochliopidae) genus in Aquidabã, as well as Planorbidae and Hemisinus kochi (Thiaridae) in Morada Nova. The 1 AS 34-AM showed a great abundance and diversity of gastropods. Two families were identified in this borehole: Thiaridae and Cochliopidae. The Cochliopidae is the most diverse and abundant in the samples, represented at least by two genus: Dyris and Tryonia, being the last one the subject of the present study. The systematic study of Tryonia genus allowed the identification of Tryonia scalarioides scalarioides species, beyond three other species which stayed in opened nomenclature. The presence of Tryonia genus in the studied samples infers an environment with a low salinity and a low energetic flow. The presence of T. s. scalarioides between the 121.09 and 130.85 m of depth from the 1 AS 34-AM borehole allowed a correlation between this interval and MZ8-12 biozones, defined in previous papers as Middle – Late Miocene. The register of Hemisinus kochi in Morada Nova at MN2 and MN5 levels suggests a correlation with MZ8 biozone, Middle Miocene. Given this, it is possible that 1 AS 34-AM borehole and Morada Nova outcrop were, at least in part, contemporary. However, a specific taxonomic identification of other gastropod groups from the study area is necessary for a more precise result.
Acesso aberto (Open Access)
A Evolução da paisagem de transição savana-floresta em Roraima durante o Holoceno tardio: base mineralógica, geoquímica e palinológica
(Universidade Federal do Pará, 2011-01-10) MENESES, Maria Ecilene Nunes da Silva; COSTA, Marcondes Lima da; http://lattes.cnpq.br/1639498384851302; https://orcid.org/0000-0002-0134-0432
The Amazonia includes several vegetation physiognomies, besides the large and well-known tropical forest. The savannas, for instance, are present in several areas as discontinuous patches or covering extensive areas as it is the case of the savannas found in the north and northeast portions of the Roraima state. These savannas belong to the so-called Rio Branco-Rupununi Complex considered the largest continuous block of that vegetation type in the Brazilian Amazonian which in the state of Roraima covers about 41.000 km2 of a total of 53.000 km2 being limited to the south and west by tropical forests. In order to understand the vegetational dynamic and the evolution of the whole landscape in face of the possible climatic changes occurred along the geological time, the present study was carried out. The chosen area for this work represents a zone of transition between savannas and forests in the western portion of the savanna block, where four topossequences (FC, FH, TIA and RU) representative of the relief, vegetation and pedological cover patterns were selected for sampling. Then, samples of the regolith cover were collected starting at the base of the topossequences (veredas) until their top parts following the visible texture and color variations of the materials. Additionally, other two veredas (AM and MB) were also cored. These regoliths samples were submitted to analyses such as granulometrical by wet sieving; mineralogical by XRD and chemical (major and trace elements) by ICP-MS and XRF methods. The sediments of the veredas were still dated by radiocarbon method using the AMS (Accelerator Mass Spectrometry) technique, and also submitted to palynological analyses including the counting of charred particles. The regoliths of the studied area vary of sandy to silty sand textures being composed by quartz and kaolinite, and in minor amounts by muscovite, sillimanite, goethite, microcline and albite. The high values of SiO2 confirm the quartzose character of these regoliths, while the values of Al2O3, more expressive in the saprolite and in the sediments from veredas reflect the higher participation of the kaolinite, which is the single clay mineral identified in these samples. The mineralogical and chemical compositions of these materials indicate provenience of metamorphic rocks and laterites that faced with warm and wet climatic conditions have been suffered strong chemical weathering and leaching. The formation and wide development of vereda of Mauritia flexuosa since about 1550 years BP as showed by the pollen analyses corroborate the humidity increase in the area, which also favored the expansion of forests. In fact, trees of Virola, Alchornea, Melastomataceae and Moraceae among other were frequent suggesting that gallery forests as well as patches of secondary forests indicated by Didymopanax, Cecropia and Attalea occurred in this region in the most of the recorded period. In spite of those humid conditions, there are records of reduction of the forests about 1400-1100 years ( FC), 900-200 years (AM and FC) and between 700 and 300 years (site TIA) in favor of the expansion of the savannas. It is probable that the reduction of forests during those periods has been provoked by the increase in the intensity of fires, inferred by the highest concentration of charred particles in the sediments, prior and during the forest cover decrease. These fires are still common in the area, being more frequent in the neighborhoods of human establishments (indigenous) and cattle farms where they possibly work as a barrier to forest expansion. Although, alternate hydromorphic and hydrological stress conditions also contribute to prevent a forest expansion. The granulometrical, mineralogical and geochemical characteristics of the regolith cover combined to the sediments pollen and ages records allowed to interpret that the studied savanna-forest landscape, which is currently marked by a complex mosaic of grassy and woody savanna crossed by veredas of Mauritia flexuosa, gallery forest corridors and islands of forest covering sandy, quartzose and kaolinitic regoliths agree with the modern warm and wet climate conditions prevailing in this region since the Late Holocene. In compensation, features such as stone lines composed by fragments of quartz and crusts denote erosive events occurred probably in the Late Pleistocene and even in the Medium Holocene when dry to arid climates dominated the region. Then, the regarded landscape has been a stage of intense ecological and geomorphological transformations fomented mainly by the climatic changes imposed to the area, although the prehistoric and the modern man has also contributed, in the sense of delaying the expansion of the forests on the savannas.
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)
Evolução dos pântanos da região central da península de Bragança-PA de acordo com as mudanças do nível relativo do mar durante o holoceno
(Universidade Federal do Pará, 2016-12-07) CAMARGO, Paloma Maria Pinto; CORRÊA, José Augusto Martins; http://lattes.cnpq.br/6527800269860568
This work integrates data from geomorphology, sedimentary features, pollen, diatom, isotopes, mineralogy, chemical analysis and C-14 datings obtained of sediment cores sampled from Bragança Península, Pará littoral. The pollen data indicate that central and topographically higher area of Bragança Peninsula was an area dominated by mangroves, with wide expansion of Avicennia trees, marine diatom, an increased trend of sedimentary organic matter sourced from estuarine algae, and a mineralogical composition mainly formed by pyrite and hematite, typical of mangrove anoxic sediments between > 6300 and 4900 cal yr BP. Between 4900 and 4300 cal yr BP occurrs a without pollen zone, but along this interval takes place marine diatom, an increase of sedimentary organic matter sourced from marine algae and the absence of minerals formed by Fe and S. In the late Holocene (<4300 cal yr BP), the study site was recolonised mainly by herbs with Avicennia trees restricted to border of the herbaceous plain, presence of freshwater diatom remains and a significant increase trend in contribution of sedimentary organic matter of terrestrial origin (C4 plants). Precipitated minerals from enviroments under intense evaporation form the mineralogical composition. In recent decades, there is a mangrove migration to elevated surfaces occupied by herbs (C4 and C3 terrestrial plants), and an increase of sedimentary organic matter sourced from estuarine algae. An upward increase in the Sr concentration occurs along the last 10 cm. These data suggest a mangrove and salt marshes dynamic mainly controlled by the relative sea level changes. Probably, postglacial sea level rise contributed to the establishment and expansion of mangroves in the Bragança Peninsula with great impact on the expansion of Avicennia trees and marine diatoms, an increase of sedimentary organic matter sourced from estuarine algae. This environment favors the mineral precipitation for instance of pyrite. Between 4900 nd 4300 cal yrs BP, the continuous relative sea level rise causes the increase of marine/estuarine diatoms and the contribution of sedimentary organic matter sourced from marine algae. However, it caused the drowning of mangrove and associated vegetation, and consequently its disappearance from the study area, as well as the environmental conditions for sulfides precipitation. After 4300 cal yrs BP, the increase of sedimentary organic matter sourced from C4 terrestrial plants and freshwater diatoms suggest a relative sea level fall. The mineralogical composition suggests an arid environment, such as a sabkha. This process caused the recolonization of herbs (mainly C4 plants) in the topographically highest area of studied peninsula and Avicennia trees surrounding this herbaceous plain. Considering the last decades, the Avicennia trees migration to elevated herbaceous fields, the increase trend of organic matter sourced from estuarine algae and the increase in concentration of Sr during the last 10 cm suggest a modern relative sea level rise.
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)
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)
Model of wetland development of the Amapá coast during the late Holocene
(2010-06) GUIMARÃES, José Tasso Felix; COHEN, Marcelo Cancela Lisboa; FRANÇA, Marlon Carlos; LARA, Rúben José; BEHLING, Hermann
The modern vegetation types, sedimentary sequences, pollen records and radiocarbon dating obtained from three sediment cores from Calçoene Coastal Plain were used to provide a palaeoecological history during the late Holocene of Amapá coastal wetland according to flood regime, sea-level and climatic changes. Based on these records, four phases of vegetation development are presented and they probably reflect the interaction between the flow energy to the sediment accumulation and the brackish/freshwater influence in the vegetation. This work suggests interchanges among time periods characterized by marine and fluvial influence. The longitudinal profile did not reveal the occurrence of mangrove in the sediment deposited around 2100 yr B.P. During the second phase, the mud progressively filled the depressions and tidal channels. The mangrove probably started its development on the channel edge, and the herbaceous field on the elevated sectors. The third phase is characterized by the interruption of mangrove development and the increase of "várzea" vegetation that may be due to the decrease in porewater salinity related to a decrease in marine water influence. The last phase is represented by the mangrove and "várzea" increase. The correlation between current patterns of geobotanical unit distribution and palaeovegetation indicates that mangrove and "várzea" forests are migrating over the herbaceous field on the topographically highest part of the studied coast, which can be related to a relative sea-level rise.
Acesso aberto (Open Access)
Morfologia polínica de espécies de Bonamia thouars, Evolvulus l. e Jacquemontia choisy (Convolvulaceae) ocorrentes numa região de ecótono no município de Caetité, BA, Brasil
(Instituto de Botânica, 2019-07) VASCONCELOS, Liziane Vilela; JUNQUEIRA, Maria Elizangela Ramos; BIANCHINI, Rosangela Simão; SABA, Marileide Dias
The pollen morphology of 17 taxa of Convolvulaceae [Bonamia agrostopolis, Evolvulus (nine species) - Tribe Cresseae), and Jacquemontia (seven species) - Tribe Jacquemontieae)] was described under light microscopy (LM) and scanning electron microscopy (SEM) with the objective of contributing to the palynology and the taxonomy of the group. The pollen material was collected from anthers and/or floral buds of herbarium exsicates, acetolyzed, analyzed quantitative and qualitatively under LM and SEM, described and illustrated. The data presented here on the pollen morphology of the studied Bonamia, Evolvulus and Jacquemontiaspecies, showed that B. agrostopolis has medium, isopolar, microechinate, granulated pollen grains with the 3-colpate apertural type, which is present in the majority of Jacquemontia species studied. On the other hand, Evolvulus species, J. gracillima and J. pentanthos have the same pollen type, characterized by being spheroidal, pantocolpate and microechinate. The other species of Jacquemontia were characterized by the subprolate to prolate-spheroidal shape, and the zonocolpate and microechinate exine in the pollen grains of all species, with granules, perforations, and micro-reticules in some species. We observed a lack of definition of the pollen types that delimit Cresseae and Jacquemontieae since there are palynological affinities between species of the two tribes. The species of Evolvulus form a stenopalynous group; however, the present study presents unpublished palynological descriptions for nine species, contributing to the expansion of pollen data and confirming the eurypalynous character of Convolvulaceae.
Acesso aberto (Open Access)
Mudanças da vegetação na ilha de Marajó durante o Holoceno Superior
(Universidade Federal do Pará, 2009-06-15) RODRIGUES, Thanan Walesza Pequeno; COHEN, Marcelo Cancela Lisboa; http://lattes.cnpq.br/8809787145146228
The vegetation dynamic around the Lake Arari – Marajo Island during the Late Holocene was studied. This research is based on pollen analysis, reflectance data, C/N relationship and AMS radiocarbon date of three sediment cores. The sampling sites are located in Santa Cruz do Arari, 6 meters height. A sediment core (65 cm) was sampled from the bottom of Lake Arari and the others (40 and 30 cm) were taken of herbaceous plain inside the lake drainage area. Probably, the herbaceous plain that dominates the eastern part of the Marajó Island began its development about 3800 cal years AP. Between 3800 and 3000 cal years A.P., the pollens diagram indicated a few mangrove pollens that suggests the final stage of an old expansion of a mangrove area. The C/N and _13C of organic matter accumulated during this period showed a marine influence. The low concentration of pollens between 3000 and 2000 cal years BP, probably due to change in flow energy, hinders the interpretation of the predominant vegetation type, but the C/N and _13C indicates a strong contribution of marine organic matter accumulated in studied sediments. This period of pollen absence may indicate an episode of difficult vegetation development due to, for example, the increase in marine influence. The last 2000 cal years A.P presented polinic content compatible with an herbaceous plain with a contribution trend of continental organic matter. The last 5 centimeters of the pollen diagram presented a predominance of Poaceae and Cyperaceae families which reflect the current predominant vegetation in the study area. The pollen diagram (PH1 and PH2) of the herbaceous plain, which colonizes the drainage basin of Lake Arari, describes a smaller spatial representation of vegetation, since they demonstrate only a constant predominance of Cyperaceae and Poaceae pollen that represents the main families of local sampling. The low depth of these profiles allowed to register the presence of herbs vegetation only from 460 and 590 cal years BP, respectively. Alternation between typical vegetation of freshwater and brackish water probably indicate changes in the porewater salinity that must be related to changes in freshwater discharge of rivers in the region and/or changes in sea level.
Acesso aberto (Open Access)
Ostracofauna da Formação Solimões (Atalaia do Norte, Amazonas, Brasil): taxonomia, implicações paleoambientais e bioestratigráficas.
(Universidade Federal do Pará, 2017-09-12) PEREIRA, Ana Paula Linhares; RAMOS, Maria Inês Feijó; http://lattes.cnpq.br/4546620118003936; 4546620118003936
The study of the ostracods from the boreholes 1AS-7D-AM, 1AS-8-AM and 1AS-31- AM, drilled at the locality of Atalaia do Norte, in Amazonas State, Brazil, allowed to recognized 9 genera and 30 species; the eurialyne genera Cyprideis is the most abundant and diverse, with 19 known species and two new species described herein: C. atalaiensis sp. nov. and C. diction sp. nov. Other marine and/or transitional (Paracypris, Perissocytheridea, Rhadinocytherura, Pellucistoma and Skopaeocythere) and non-marine (Cypria, Cytheridella and Penthesilenula) genera have been found, as well as other microfossils (foraminifera, fishs, mollusks and palinomorphs) which have been used for the paleoenvironmental interpretations and biostratigraphy of the Solimões Formation. The integrated stratigraphic analisys of ostracods and palinomorphs in the boreholes 1AS-8-AM and 1AS-7D-AM allowed to date the sequence from Early Miocene to Late Miocene. Through the index fossils, were identified five palinological zones already proposed from the Neogene of western Amazon: Verrutricolporites, Early Miocene; Psiladiporites-Crototricolpites, Late Early Miocene to Early Middle Miocene; Crassoretitriletes, Middle Miocene; Grimsdalea, Late Middle Miocene to Early Late Miocene; and Astaraceae, Late Miocene. The distribution of the Cyprideis species allowed to recognize five zones corresponding to the palynological zones, four of which previously established, although its age limits have been changed in this study: C. aulakos, renamed as C. sulcosigmoidalis, from late Early Miocene to early Middle Miocene, C. caraione, Middle Miocene to early Late Miocene, C. minipunctata, late Late Miocene and C. cyrtoma Late Miocene. Furthermore, is proposed here a new ostracod zone: C. paralela, from Late Miocene. The biostratigraphic analysis, based on palinology and ostracods, as well as other microfossils reveals a sequence which starts at the Early Miocene, with influence of coastal environments attested by the presence of palinomorphs and foraminifera typically from mangrove. At the Middle Miocene, the paleoenvironments are characterized as fluvio-lacustrine with marine influence. Finally, in the Late Miocene although still marked by marine influence, predominate fluvio-lacustrine environment upward to the section.
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Palinologia da Formação Pirabas, nos municípios de Primavera e Salinópolis, nordeste do estado do Pará, Brasil
(Universidade Federal do Pará, 2016-04-30) SILVA, Carla Batista da; GUIMARÃES, José Tasso Felix; http://lattes.cnpq.br/9602707802326509
During the Paleogene - Neogene transition, the Amazon coast (Brazil) presented very low rates of sedimentation and influx of siliciclastic sediments supplied by an ancient river basin, which allowed the formation of extensive and thick carbonate deposit. According to the development of Amazon fan in the upper Miocene, these deposits may have represented the last stage of carbonate sedimentation in transitional environments of the Amazon coast. The integration of facies and pollen analysis of a drill hole from Primavera/PA (FPR-160 core) and reassessment of pollen systematic of Cunha (2013) from an outcrop in Salinopólis/PA, allowed the identification of a lagoon connected to a shallow marine platform formed between the upper Oligocene and lower Miocene. The occurrence of Retibrevitricolporites grandis in FPR-160 core in the basal portion of the core, which is just above the crystalline basement rocks, provided a maximum age restricted to the upper Oligocene for the base of the formation Pirabas. The presence of Retitrescolpites irregularis, Psilatricolporites crassoexinatus and Retibrevitricolporites grandis together with the absence of Zonocostites ramonae and Deltoidospora adriennis may indicate that there was considerable continental influence on the deposits or occurrence of a marine environment with restricted mangrove areas. The occurrence of Mauritiidites franciscoi, P. crassoexinatus, R. irregularis, Malvacipolloides maristellae and Zonocostites ramonae in the outcrop in Salinopólis/PA, suggests lower Miocene age to the top of this unit, interpreted as a lagoon bordered palaeoenvironment by mangrove vegetation.