Prehistoric shell mounds can be useful for the quantification of the radiocarbon marine reservoir... more Prehistoric shell mounds can be useful for the quantification of the radiocarbon marine reservoir effect (MRE) and, at the same time, knowledge about the MRE allows for the establishment of robust chronologies for these sites. This creates a loop in which the archaeological setting has a dual role: it is part of both the method and the application. Therefore, it is paramount to address these sites from both archaeological and environmental perspectives, investigating their origin and diagenesis in order to overcome biases caused by post-depositional alterations. In this study, samples of bone, charcoal and shell from a Late Holocene shell mound in Southern Brazil, the Sambaqui de Cabeçuda, were analyzed following a multidisciplinary approach to disentangle the complex relationships between archaeology and the environment. We performed X-ray diffraction, radiocarbon dating, stable isotopes (δ13C, δ18O, δ15N) and anthracology analyses as well as Bayesian Chronological Models and Isoto...
ABSTRACTIn paleoenvironmental research, several proxies are used to reconstruct climate and veget... more ABSTRACTIn paleoenvironmental research, several proxies are used to reconstruct climate and vegetation. The establishment of a chronological framework allows for the association of different proxies and correlation of events happening in different geographic areas. Cultural deposits, such as the shellmounds found along the coast of Brazil, play an important role in paleoenvironmental interpretations. Here, we have employed anthracological analysis in charcoal fragments from the Amourins shellmound, located at the margins of the Guanabara Bay, Rio de Janeiro. This allowed for the taxonomic identification and selection of short-lived trees and specific parts of plants for accurate radiocarbon dating. We recorded genera and families typical of the Atlantic Forest, restinga forest, open restinga and mangrove. The 14C ages of charred nuts from different occupational layers range from 3807 ± 35 to 3503 ± 70 BP and a sequential chronological model was built, relating the predominance of ma...
Interactions between invader species and the local biota may lead to disequilibria in regional ec... more Interactions between invader species and the local biota may lead to disequilibria in regional ecosystems. For such reason, the cultivation of nonnative species may be prohibited in specific regions, as a means of protecting native species. On the other hand, the question of whether a species is a bioinvader or not may not be straightforward. This is the case of the mollusc Perna perna, presently naturalized and widely distributed along Brazilian coast, from the Bay of Vitória, in the state of Espírito Santo (ES), to the state of Rio Grande do Sul (RS). Following previous works that explored the hypothesis that P. perna invaded the coast of Brazil at the colonial period, attached to slave ships, we discuss zooarchaeological data, radiocarbon dating, and molecular genetics analyses. Out of the 578 archeological shellmounds investigated, 542 (93.8%) had no records of P. perna. From the radiocarbon dating results, it is possible to infer that the presence of the two P. perna specimens ...
ABSTRACTThe Rio Grande Cone is a major fanlike depositional feature in the continental slope of t... more ABSTRACTThe Rio Grande Cone is a major fanlike depositional feature in the continental slope of the Pelotas Basin, Southern Brazil. Two representative sediment cores collected in the Cone area were retrieved using a piston core device. In this work, the organic matter (OM) in the sediments was characterized for a continental vs. marine origin using chemical proxies to help constrain the origin of gas in hydrates. The main contribution of OM was from marine organic carbon based on the stable carbon isotope (δ13C-org) and total organic carbon/total nitrogen ratio (TOC:TN) analyses. In addition, the 14C data showed important information about the origin of the OM and we suggest some factors that could modify the original organic matter and therefore mask the “real” 14C ages: (1) biological activity that could modify the carbon isotopic composition of bulk terrestrial organic matter values, (2) the existence of younger sediments from mass wasting deposits unconformably overlying older s...
ABSTRACTConsidering the impact of coastal dynamics on the radiocarbon (14C) marine reservoir effe... more ABSTRACTConsidering the impact of coastal dynamics on the radiocarbon (14C) marine reservoir effect (MRE), upwelling has the potential of enhancing marine influence, usually14C depleted. Freshwater input can contribute either to increased reservoir offsets, when dead carbon from rock weathering is available, but also towards an atmospheric14C signal, when the presence of terrestrial organic matter from catchment prevails. An overview of the MRE studies based on shellmounds on the coast of Rio de Janeiro reveals a pattern of negative local corrections for Saquarema and Rio das Ostras but positive values for Cabo Frio island, suggesting the presence of cold upwelling waters in Cabo Frio at 1.6–1.2 cal kBP. New results for a shellmound on the Ilha Grande island, in the western portion of the Rio de Janeiro coast, revealed a negative value at about 3 ka. We discuss distribution of MRE values and temporal variability in the region and their relation to ocean dynamics, continental input a...
Among other zooarchaeological remains, terrestrial snails’ shells from the Thaumastus and Megalob... more Among other zooarchaeological remains, terrestrial snails’ shells from the Thaumastus and Megalobulimus genera are found in some Brazilian shellmounds, presenting a potential substitute for charcoal in radiocarbon dating analyses, as reliable representatives of the atmospheric carbon isotopic ratio. In this paper, we present statistically similar results of both charcoal and land snails samples from the same archaeological contexts in three settlements on the coast of Rio de Janeiro. The Manitiba I shellmound results range from 4.2 to 3.7 ka cal BP (95.4%), contemporary with the Saquarema shellmound, occupied during the period from 4.3 to 3.6 ka cal BP (95.4%). For the Usiminas shellmound, two groups of samples revealed different periods of time for two occupational layers from 2.3 to 2.1 ka cal BP (95.4%) and from 1.6 and 1.3 ka cal BP (95.4%). A model constraining each group of samples to within a single phase has a general agreement of 97% with only two outliers out of 22 dates, ...
In the present work, we assess the chronology of archaeological sites known as earthen mounds, co... more In the present work, we assess the chronology of archaeological sites known as earthen mounds, commonly found at the Pampas biome, among the lowlands of Brazil, Uruguay, and Argentina. We focused on the Pontal da Barra settlement, which is a testimony of the long-term occupation of indigenous groups in the swamp and wet environment of Patos Lagoon, southern Brazil. A Bayesian chronological model based on the radiocarbon (14C) dating of 17 samples of fish otolith, 5 charcoal fragments, and 2 bones (human and dog) allowed determination of the beginning of the occupation as well as the occupational synchronism of the different mounds. The nature of the samples allows us to study the local14C reservoir effect through the comparison between the group of marine and terrestrial samples, deriving a reservoir offset value of 63±5314C yr for this particular area, indicating a strong freshwater influence in the lagoon system. We estimate the start of human intervention in the landscapes of sou...
Abstract In a previous work, isotopic fractionation in the graphitization reaction for Radiocarbo... more Abstract In a previous work, isotopic fractionation in the graphitization reaction for Radiocarbon Accelerator Mass Spectrometry ( 14 C-AMS) was evaluated for amounts of Zn ranging from 20 to 50 mg. The results have shown that a slightly lower variation in δ 3 C during graphitization was achieved with less Zn. In the present paper, assuming that low amounts of Zn would provide the best results, we go further and test isotopic fractionation for 0, 10 and 20 mg of Zn in the graphitization reaction. The results show that the use of 10 mg of Zn yields similar fractionation to that using 20 mg, while using only TiH 2 and no Zn produces the same scattering for amounts from 30 to 50 mg. The absence of Zn, on the other hand, plays a major role on the reaction yield for the tested conditions, limiting it to 50%.
The regional component (∆R) of the marine reservoir effect (MRE), which is crucial for the accura... more The regional component (∆R) of the marine reservoir effect (MRE), which is crucial for the accurate calibration of radiocarbon ages of marine-influenced samples, was determined for the Cuban northwestern coast. Fifteen different locations were studied by14C dating of pre-bomb known-age marine shells specimens of bivalves and gastropods from the Felipe Poey Museum collection. Accelerator mass spectrometry (AMS)14C measurements were performed at the Radiocarbon Laboratory of the Universidade Federal Fluminense (LAC-UFF) and mean ΔR values were estimated. The distribution of results indicates ∆R values from −46±38 to 140±5214C yr and a possible pattern related to the position along the coast and ocean dynamics. We present both mean values for each region and a general ∆R of 28±1314C yr for the northwestern coast of Cuba.
The Radiocarbon Laboratory of the Universidade Federal Fluminense, in Brazil, has been successful... more The Radiocarbon Laboratory of the Universidade Federal Fluminense, in Brazil, has been successfully applying the zinc reduction method for graphitization of carbon samples since the development of its early protocols in 2009. Successive methodological research aiming to improve and, ultimately, optimize the precision and accuracy of our results indicates that graphitization temperatures as low as 460°C promote erratic 13C isotopic fractionation, but an approximately constant fractionation of about –5‰ is achieved at 520°C. In this work, we present isotope ratio mass spectrometry (IRMS) δ13C results for 14C reference materials graphitized at 550°C with variable amounts of zinc. Based on the results obtained from the addition of 20, 35, and 50 mg of zinc, we conclude that a slightly lower variation in 13C isotope fractionation during graphitization is obtained with less zinc. Moreover, the average isotopic fractionation is not altered by increasing the graphitization temperature from ...
In Brazilian archaeological shellmounds, many species of land snails are found abundantly distrib... more In Brazilian archaeological shellmounds, many species of land snails are found abundantly distributed throughout the occupational layers, forming a contextualized set of samples within the sites and offering a potential alternative to the use of charcoal for radiocarbon dating analyses. In order to confirm the effectiveness of this alternative, one needs to prove that the mollusk shells reflect the atmospheric carbon isotopic concentration in the same way charcoal does. In this study, 18 terrestrial mollusk shells with known collection dates from 1948 to 2004 AD, around the nuclear bombs period, were radiocarbon dated. The obtained dates fit the SH1-2 bomb curve within less than 15 years range, showing that certain species from the Thaumastus and Megalobulimus genera are reliable representatives of the atmospheric carbon isotopic ratio and can, therefore, be used to date archaeological sites in South America.
The Saquarema archaeological site, on the Atlantic coast of the Rio de Janeiro State, is one of m... more The Saquarema archaeological site, on the Atlantic coast of the Rio de Janeiro State, is one of many shellmounds built on the Brazilian coast by hunter-gatherer populations during the Holocene. We used archaeological material from this site with the aim of evaluating the marine reservoir effect (MRE) in the region. Radiocarbon ages of 45 marine and 6 terrestrial samples from this shellmound provided data for assessing the MRE and the influences of freshwater and seasonal coastal marine upwelling in this specific locality. Samples of charcoal, fish otoliths, and mollusk shells were analyzed and the 14C dates were modeled in the OxCal platform to determine the marine reservoir correction. The result obtained is R = 265 ± 70 14C yr and the offset ΔR was found to be –140 ± 66 14C yr. To support the accuracy of this value for correcting conventional 14C marine ages, taxonomic analyses of the samples were performed.
Prehistoric shell mounds can be useful for the quantification of the radiocarbon marine reservoir... more Prehistoric shell mounds can be useful for the quantification of the radiocarbon marine reservoir effect (MRE) and, at the same time, knowledge about the MRE allows for the establishment of robust chronologies for these sites. This creates a loop in which the archaeological setting has a dual role: it is part of both the method and the application. Therefore, it is paramount to address these sites from both archaeological and environmental perspectives, investigating their origin and diagenesis in order to overcome biases caused by post-depositional alterations. In this study, samples of bone, charcoal and shell from a Late Holocene shell mound in Southern Brazil, the Sambaqui de Cabeçuda, were analyzed following a multidisciplinary approach to disentangle the complex relationships between archaeology and the environment. We performed X-ray diffraction, radiocarbon dating, stable isotopes (δ13C, δ18O, δ15N) and anthracology analyses as well as Bayesian Chronological Models and Isoto...
ABSTRACTIn paleoenvironmental research, several proxies are used to reconstruct climate and veget... more ABSTRACTIn paleoenvironmental research, several proxies are used to reconstruct climate and vegetation. The establishment of a chronological framework allows for the association of different proxies and correlation of events happening in different geographic areas. Cultural deposits, such as the shellmounds found along the coast of Brazil, play an important role in paleoenvironmental interpretations. Here, we have employed anthracological analysis in charcoal fragments from the Amourins shellmound, located at the margins of the Guanabara Bay, Rio de Janeiro. This allowed for the taxonomic identification and selection of short-lived trees and specific parts of plants for accurate radiocarbon dating. We recorded genera and families typical of the Atlantic Forest, restinga forest, open restinga and mangrove. The 14C ages of charred nuts from different occupational layers range from 3807 ± 35 to 3503 ± 70 BP and a sequential chronological model was built, relating the predominance of ma...
Interactions between invader species and the local biota may lead to disequilibria in regional ec... more Interactions between invader species and the local biota may lead to disequilibria in regional ecosystems. For such reason, the cultivation of nonnative species may be prohibited in specific regions, as a means of protecting native species. On the other hand, the question of whether a species is a bioinvader or not may not be straightforward. This is the case of the mollusc Perna perna, presently naturalized and widely distributed along Brazilian coast, from the Bay of Vitória, in the state of Espírito Santo (ES), to the state of Rio Grande do Sul (RS). Following previous works that explored the hypothesis that P. perna invaded the coast of Brazil at the colonial period, attached to slave ships, we discuss zooarchaeological data, radiocarbon dating, and molecular genetics analyses. Out of the 578 archeological shellmounds investigated, 542 (93.8%) had no records of P. perna. From the radiocarbon dating results, it is possible to infer that the presence of the two P. perna specimens ...
ABSTRACTThe Rio Grande Cone is a major fanlike depositional feature in the continental slope of t... more ABSTRACTThe Rio Grande Cone is a major fanlike depositional feature in the continental slope of the Pelotas Basin, Southern Brazil. Two representative sediment cores collected in the Cone area were retrieved using a piston core device. In this work, the organic matter (OM) in the sediments was characterized for a continental vs. marine origin using chemical proxies to help constrain the origin of gas in hydrates. The main contribution of OM was from marine organic carbon based on the stable carbon isotope (δ13C-org) and total organic carbon/total nitrogen ratio (TOC:TN) analyses. In addition, the 14C data showed important information about the origin of the OM and we suggest some factors that could modify the original organic matter and therefore mask the “real” 14C ages: (1) biological activity that could modify the carbon isotopic composition of bulk terrestrial organic matter values, (2) the existence of younger sediments from mass wasting deposits unconformably overlying older s...
ABSTRACTConsidering the impact of coastal dynamics on the radiocarbon (14C) marine reservoir effe... more ABSTRACTConsidering the impact of coastal dynamics on the radiocarbon (14C) marine reservoir effect (MRE), upwelling has the potential of enhancing marine influence, usually14C depleted. Freshwater input can contribute either to increased reservoir offsets, when dead carbon from rock weathering is available, but also towards an atmospheric14C signal, when the presence of terrestrial organic matter from catchment prevails. An overview of the MRE studies based on shellmounds on the coast of Rio de Janeiro reveals a pattern of negative local corrections for Saquarema and Rio das Ostras but positive values for Cabo Frio island, suggesting the presence of cold upwelling waters in Cabo Frio at 1.6–1.2 cal kBP. New results for a shellmound on the Ilha Grande island, in the western portion of the Rio de Janeiro coast, revealed a negative value at about 3 ka. We discuss distribution of MRE values and temporal variability in the region and their relation to ocean dynamics, continental input a...
Among other zooarchaeological remains, terrestrial snails’ shells from the Thaumastus and Megalob... more Among other zooarchaeological remains, terrestrial snails’ shells from the Thaumastus and Megalobulimus genera are found in some Brazilian shellmounds, presenting a potential substitute for charcoal in radiocarbon dating analyses, as reliable representatives of the atmospheric carbon isotopic ratio. In this paper, we present statistically similar results of both charcoal and land snails samples from the same archaeological contexts in three settlements on the coast of Rio de Janeiro. The Manitiba I shellmound results range from 4.2 to 3.7 ka cal BP (95.4%), contemporary with the Saquarema shellmound, occupied during the period from 4.3 to 3.6 ka cal BP (95.4%). For the Usiminas shellmound, two groups of samples revealed different periods of time for two occupational layers from 2.3 to 2.1 ka cal BP (95.4%) and from 1.6 and 1.3 ka cal BP (95.4%). A model constraining each group of samples to within a single phase has a general agreement of 97% with only two outliers out of 22 dates, ...
In the present work, we assess the chronology of archaeological sites known as earthen mounds, co... more In the present work, we assess the chronology of archaeological sites known as earthen mounds, commonly found at the Pampas biome, among the lowlands of Brazil, Uruguay, and Argentina. We focused on the Pontal da Barra settlement, which is a testimony of the long-term occupation of indigenous groups in the swamp and wet environment of Patos Lagoon, southern Brazil. A Bayesian chronological model based on the radiocarbon (14C) dating of 17 samples of fish otolith, 5 charcoal fragments, and 2 bones (human and dog) allowed determination of the beginning of the occupation as well as the occupational synchronism of the different mounds. The nature of the samples allows us to study the local14C reservoir effect through the comparison between the group of marine and terrestrial samples, deriving a reservoir offset value of 63±5314C yr for this particular area, indicating a strong freshwater influence in the lagoon system. We estimate the start of human intervention in the landscapes of sou...
Abstract In a previous work, isotopic fractionation in the graphitization reaction for Radiocarbo... more Abstract In a previous work, isotopic fractionation in the graphitization reaction for Radiocarbon Accelerator Mass Spectrometry ( 14 C-AMS) was evaluated for amounts of Zn ranging from 20 to 50 mg. The results have shown that a slightly lower variation in δ 3 C during graphitization was achieved with less Zn. In the present paper, assuming that low amounts of Zn would provide the best results, we go further and test isotopic fractionation for 0, 10 and 20 mg of Zn in the graphitization reaction. The results show that the use of 10 mg of Zn yields similar fractionation to that using 20 mg, while using only TiH 2 and no Zn produces the same scattering for amounts from 30 to 50 mg. The absence of Zn, on the other hand, plays a major role on the reaction yield for the tested conditions, limiting it to 50%.
The regional component (∆R) of the marine reservoir effect (MRE), which is crucial for the accura... more The regional component (∆R) of the marine reservoir effect (MRE), which is crucial for the accurate calibration of radiocarbon ages of marine-influenced samples, was determined for the Cuban northwestern coast. Fifteen different locations were studied by14C dating of pre-bomb known-age marine shells specimens of bivalves and gastropods from the Felipe Poey Museum collection. Accelerator mass spectrometry (AMS)14C measurements were performed at the Radiocarbon Laboratory of the Universidade Federal Fluminense (LAC-UFF) and mean ΔR values were estimated. The distribution of results indicates ∆R values from −46±38 to 140±5214C yr and a possible pattern related to the position along the coast and ocean dynamics. We present both mean values for each region and a general ∆R of 28±1314C yr for the northwestern coast of Cuba.
The Radiocarbon Laboratory of the Universidade Federal Fluminense, in Brazil, has been successful... more The Radiocarbon Laboratory of the Universidade Federal Fluminense, in Brazil, has been successfully applying the zinc reduction method for graphitization of carbon samples since the development of its early protocols in 2009. Successive methodological research aiming to improve and, ultimately, optimize the precision and accuracy of our results indicates that graphitization temperatures as low as 460°C promote erratic 13C isotopic fractionation, but an approximately constant fractionation of about –5‰ is achieved at 520°C. In this work, we present isotope ratio mass spectrometry (IRMS) δ13C results for 14C reference materials graphitized at 550°C with variable amounts of zinc. Based on the results obtained from the addition of 20, 35, and 50 mg of zinc, we conclude that a slightly lower variation in 13C isotope fractionation during graphitization is obtained with less zinc. Moreover, the average isotopic fractionation is not altered by increasing the graphitization temperature from ...
In Brazilian archaeological shellmounds, many species of land snails are found abundantly distrib... more In Brazilian archaeological shellmounds, many species of land snails are found abundantly distributed throughout the occupational layers, forming a contextualized set of samples within the sites and offering a potential alternative to the use of charcoal for radiocarbon dating analyses. In order to confirm the effectiveness of this alternative, one needs to prove that the mollusk shells reflect the atmospheric carbon isotopic concentration in the same way charcoal does. In this study, 18 terrestrial mollusk shells with known collection dates from 1948 to 2004 AD, around the nuclear bombs period, were radiocarbon dated. The obtained dates fit the SH1-2 bomb curve within less than 15 years range, showing that certain species from the Thaumastus and Megalobulimus genera are reliable representatives of the atmospheric carbon isotopic ratio and can, therefore, be used to date archaeological sites in South America.
The Saquarema archaeological site, on the Atlantic coast of the Rio de Janeiro State, is one of m... more The Saquarema archaeological site, on the Atlantic coast of the Rio de Janeiro State, is one of many shellmounds built on the Brazilian coast by hunter-gatherer populations during the Holocene. We used archaeological material from this site with the aim of evaluating the marine reservoir effect (MRE) in the region. Radiocarbon ages of 45 marine and 6 terrestrial samples from this shellmound provided data for assessing the MRE and the influences of freshwater and seasonal coastal marine upwelling in this specific locality. Samples of charcoal, fish otoliths, and mollusk shells were analyzed and the 14C dates were modeled in the OxCal platform to determine the marine reservoir correction. The result obtained is R = 265 ± 70 14C yr and the offset ΔR was found to be –140 ± 66 14C yr. To support the accuracy of this value for correcting conventional 14C marine ages, taxonomic analyses of the samples were performed.
Resumo: Os sambaquis do litoral do Espírito Santo foram pouco estudados pelas pesquisas arqueológ... more Resumo: Os sambaquis do litoral do Espírito Santo foram pouco estudados pelas pesquisas arqueológicas realizadas no estado. Apesar de serem conhecidos desde finais do século XIX, foram recorrentemente considerados uma extensão marginal dos desenvolvimentos culturais que aconteciam no Rio de Janeiro. À escassez de informações sobre as características dos sítios, soma-se a ausência de datações 14 C bem referenciadas, as quais impedem o entendimento da profundidade temporal e da evolução da ocupação humana pré-colonial no litoral do estado. Este artigo apresenta as metas e os resultados da retomada das pesquisas arqueológicas nos sambaquis do litoral norte do Espírito Santo, em Linhares. Até o momento, foram escavados dois sambaquis cuja idade recua em quase 2000 anos o registro de presença humana na costa do estado. As novas pesquisas seguem um método padronizado para escavação dos sítios, especialmente desenhado para a primeira caracterização dos sambaquis, o qual envolve a construção de um banco de dados digital e a incorporação de sistemas informatizados para gerenciamento das escavações. As pesquisas revelaram evidências da ocupação humana na região anterior ao máximo transgressivo holocênico (sítio Suruaca 20, datado em c. 6800 cal. AP), momento em que manguezais, restingas e florestas de tabuleiros constituíam o ambiente costeiro. Abstract: The shell mounds (sambaquis) on the coast of Espírito Santo have received little attention in archaeological research. Despite being known to scholars since the end of the nineteenth century, shell mounds were recurrently considered marginal to the cultural developments in the neighboring state of Rio de Janeiro. Scarce information on the contents of the sites and the lack of well-referenced 14 C dating prevented a complete understanding of the time-depth and evolution of pre-colonial settlement on this fragment of the Brazilian coast. This paper introduces the aims and preliminary results of renewed archaeological research on the shell mounds of the northern coast of Espírito Santo, in the municipality of Linhares. Two shell mounds have been excavated thus far, pushing the record of human presence on the coast back by almost 2000 years. The new research follows a standardized method of excavation specially designed for initial characterization of shell mound deposits; this method involves creating a digital database and incorporating computerized methods for excavation management. Signs of human presence were seen along the northern coast before the Holocene maximum transgression (Suruaca site, dated c. 6800 cal. BP), when mangroves, restingas, and the Atlantic rainforest comprised the coastal environment.
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