Late Holocene Evolution of the Northeast Intertidal Region of Sepetiba Bay, Rio De Janeiro (Brazil)

Abstract

This work is based on the study of the core T1 collected in the Guaratiba Mangrove, located on the northeastern margin of Sepetiba Bay. Few studies dealing with the application of benthic foraminifera to study sea level changes during the Holocene have been conducted in Sepetiba Bay, State of Rio de Janeiro, Brazil. In order to fill this gap, the core T1 was studied using textural, geochemical (carbonate, total organic carbon, total sulfur and stable isotopes evaluated in Ammonia tepida) and microfaunal (benthic foraminifera) data, unveiling paleoecological relationships of these organisms and the evolutionary scenario of Guaratiba Mangrove. Radiocarbon results indicate an estimated age of about 2400 yrs cal BP for the core base. Textural, geochemical and benthic foraminifera data suggest that the study area changed significantly during the last 2400 yrs cal BP. It experienced coastal waves action and shoreface processes in the period between ≈2.400-1.400 yrs cal BP; then, this phase gave place to a shallow marine environment similar to that found currently in internal and protected areas of Sepetiba Bay, between ≈1.400-350 yrs cal BP. Thenceforth, the study area evolved to the present mangrove environment. Factors related to climatic oscillations and the formation, evolution and events of rupture of Marambaia sand ridge influenced the late Holocene evolution of the northeast intertidal area of Sepetiba Bay.

Holocene Closure of a Barrier Beach in Sepetiba Bay and Its Environmental Impact (Rio De Janeiro, Brazil)

“…High CaCO3 contents were also found in core T1 at Magaratiba coastal plain in the last ≈300 yrs cal BP (upper 150 cm of this core). These values were associated by Pinto et al (2016) with evaporitic series related to the formation of the salt flats (the current apicum and mangrove existing in the area).…”

“…The period between ≈2,400-1,400 yrs cal BP was signed by sedimentological and microfaunal changes both in core T4 (generic low abundance of foraminifera and carbonates content and slight increase of sand fraction) and in core T1 collected in the nearby Guaratiba Coastal Plain (mangrove), according to Pinto et al (2016;Fig. 6).…”

“…The age model of this core was based on radiocarbon data and the results were compared with that obtained in core T1 collected in nearby the Guaratiba Coastal Plain (mangrove), studied by Pinto et al (2016).…”

“…1. Location of the core T4 analyzed in this work, as well core T1 studied by Pinto et al (2016). Modified from Google Earth (datum WGS84).…”

“…Among the studies that used foraminifera assemblages aiming to investigate the paleoenvironments related to sea level changes in Sepetiba Bay (Brazil), there are, for instance, the works of Laut et al (2006), Laut and Rodrigues (2011) and Pinto et al (2016). The studies of Fonseca et al (2007) and Bruno (2013), for example, based on foraminifera and performed on coastal systems of Rio de Janeiro State, in Guanabara Bay and Saquarema Lagoon, respectively, suggested the occurrence of a Holocene sea level maximum at about 5,000 BP.…”