Benthic Foraminifera as Evidence of Paleoenvironmental Changes between 9400 and 8300 cal YBP at the Juréia-Itatins Ecological Station Paleolagoon (SP, Brasil)

• Published in: Journal of coastal research 2014-11, Vol.30 (6), p.1118-1130
• Main Authors: Silva, Juliana Braga, Duleba, Wânia, Sallun, Alethea M, Suguio, Kenitiro
• Format: Article
• Language: English
• Subjects: Ammonia; assemblage structures; Behavior; biodiversity; Brazil; Chemical analysis; Coastal ecology; Coastal environments; Ecological monitoring; Foraminifera; Holocene; Hydrodynamics; Lagoons; Marine ecology; microbenthos; Microorganisms; Phases; Recognition; Relative sea level; RESEARCH PAPERS; River water; Rivers; Salinity; Sea level; Sea water; Seawater; Sediments; Stations; Studies; Tissue oxygenation; Water analysis; Water inflow
• ISSN: 0749-0208; 1551-5036
• DOI: 10.2112/JCOASTRES-D-12-00121.1

Silva, J.B.; Duleba, W.; Sallun, A.M., and Suguio, K., 2014. Benthic foraminifera as evidence of paleoenvironmental changes between 9400 and 8300 cal YBP at the Juréia-Itatins Ecological Station paleolagoon (SP, Brasil). Many aspects of the Santos Transgression (∼21,227–20,448 to ∼5558–4558 cal YBP) remain controversial, especially before approximately 7800 cal YBP, because of the paucity of data for the Brazilian coast. In this context, benthic foraminiferal assemblages from between 9400 and 8385 cal YBP were analyzed from the S03 core collected at the Juréia-Itatins Ecological Station (JIES) with the aim of clarifying the behavior of the relative sea level along the Brazilian coast during this period. Microfaunal, taphonomical, and morphometric analyses of these microorganisms permitted recognition of eight paleoenvironmental conditions within the lagoon then existing at JIES. There were four phases of conspicuous marine contributions (9400–9338, 9072–8894, 8656–8641, and 8594–8500 cal YBP) with a climax at 8656 cal YBP, when the environment became more favorable to the growth, preservation, or both of benthic foraminifera. They were intercalated with two phases of prominent continental contributions (9338–9072 and 8500–8385 cal YBP), when there was an increase in the local hydrodynamic gradient at the S03 core sampling site. Furthermore, between 8806 and 8672 cal YBP and between 8625 and 8594 cal YBP, the benthic foraminifera are absent, most likely because of the lower pH of the mixohaline/limnetic waters present when the continental contribution was highest. These different phases of marine and continental contributions could be explained by the higher or lower inflow of seawater to the paleolagoon of the JIES and by changes of the regional rainfall. Muitos aspectos da Transgressão Santos (∼21.227–20.448 a ∼5558–4558 anos cal AP) são ainda controvertidos, especialmente antes de aproximadamente 7800 anos cal AP, devido à diferença de detalhamento de dados na costa brasileira. Nesse contexto, foram analisadas associações de foraminíferos bentônicos no testemunho S03, coletado na Estação Ecológica Juréia-Itatins (EEJI), entre 9400 e 8385 anos cal AP, para colaborar com o conhecimento acerca do nível relativo do mar na costa brasileira sudeste durante esse período. As análises microfaunísticas, tafonômicas, e morfométricas das testas e associações desses microorganismos permitiram a determinação de oito fases distintas nas condições paleoambientais na lag