Mid- to Late-Holocene estuarine infilling processes studied by radiocarbon dates, high resolution seismic and biofacies at Vitoria Bay, Espirito Santo, Southeastern Brazil

Abstract

Vitoria Bay is a 20 km long estuary, morphologically narrow, with a microtidal regime and, as other modern estuaries, was formed during the last post-glacial transgression. The estuarine bed morphology is characterised by a main natural channel limited by tidal flats with developed mangroves. Original radiocarbon dates were obtained for the site. Five radiocarbon ages ranging from 1,010 to 7,240 years BP were obtained from two sedimentary cores, which represent a 5 m thick stratigraphic sequence. The results indicate that, until about 4,000 cal. yrs BP, environmental conditions in Vitoria Bay were still of an open bay, with a free and wide connection with marine waters. During the last 4,000 yrs, the bay has experienced a major regression phase, by becoming more restricted in terms of seawater circulation and probably increasing tidal energy. Three main stratigraphic surfaces were recognised, which limit trangressive, trangressive/highstand and regressive facies. The present channel morphology represents a tidal scouring surface or a tidal diastem, which erodes and truncates regressive facies bedding. Foraminiferal biofacies, which change from marine to brackish and mangrove tidal-flat environments, support the seismic stratigraphic interpretation. Absence of mangrove biofacies at one of the two cores is also an indication of modern tidal ravinement.

Quartz grain assessment for reconstructing the coastal palaeoenvironment

“…The dark brown to black sediment color found in these samples (SP2 1 m and SP3 1 and 2 m) was also described by Bastos et al (2010) in boreholes from Vitoria Bay. Those sediments were associated with foraminifera assemblages of a more restricted environment, such as an estuary.…”

“…Similar characteristics in sediment color, texture and the highly variable content of calcium carbonate were found in other boreholes, also from Vitoria Bay, and were interpreted as transgressive environments with a strong connection to the sea by biofacies defined by foraminiferan assemblages (Bastos et al, 2010).…”

The structural heterogeneity of an urbanised mangrove forest area in southeastern Brazil: Influence of environmental factors and anthropogenic stressors

“…The Vitória Bay estuary is characterised by a microtidal regime, classified as semi-diurnal (BASTOS et al, 2010). The currents inside Vitória Bay are the result of tidal effects, the flow of the rivers, bay morphology, water column stratification, waves and winds (VERONEZ JÚNIOR et al, 2009).…”

Sedimentary, Geochemical and Micropaleontological Responses to Sea Level Variations in the Vitoria Estuary, Espírito Santo

“…Quaternary records are characterized by fluvial-marine sands with mangrove areas limited by relief (Machado et al 2016; Figure 1). Research regarding the evolution of coastal Quaternary deposits has been limited to a few studies (Martin et al 1996; Bastos et al 2010; Machado et al 2016). Exceptions are the studies along the north coast of the state, around the mouth of the Doce River (Suguio and Martin 1981; Dominguez et al 1983, 1981; Martin et al 1996, 1993; Hatushika et al 2007; Cohen et al 2014; France et al 2015; Rossetti et al 2015).…”