Relative Sea Level Variations and Climatic Evolutuion in Southeastern and Southern Brazil During the Late Holocene

Abstract

Analysis of organic sediments from a swamp forest on the coastal plain of São Paulo State (southeastern Brazil) has been carried out. Diatom and pollen contents from the same samples were analysed. This study allowed reconstruction of the regional paleoenvironment during the Late Holocene. From at least 4400 to 3250 yr BP the site was a lagoon surrounded by a relatively open forest. At ca. 3250 yr BP, after the retreat of the sea, a swamp forest occupied the area. This swamp forest remains until the present day. It was locally altered during a short period between ca. 1400 and 775 yr BP when, due to a rise in groundwater, a fresh water lake or marsh was formed. The climate was similar to the present during the whole Late Holocene, except for three slightly more humid episodes: 3250-2600, around 2000, and 1400-775 yr BP. No human impact on the vegetation was recorded during the Late Holocene. Our results show that sea level was higher than the present zero level from 4400 to 3250 yr BP, contradicting a widely accepted relative sea level trend that suggests that at least two important negative sea level oscillations occurred during the Holocene (4100-3800 and 3000-2700 yr BP). Conversely, these results tend to confirm more recent studies that propose a continuously declining relative sea level trend. Comparison of our data with those from 24 sites situated in southeastern, southern and central Brazil show that the more humid episodes recorded at Cananéia-Iguape might be correlated with El Niño like events. Trends in climatic evolution during the Late Holocene are opposite at north and south of 20ºS latitude.

The last 25,000 years in the Eastern Plateau of Southern Brazil according to Alpes de São Francisco record

“…Then, it would be interesting to re-evaluate the results that infer warm and dry climates during this phase in South Brazil. In a similar way, Ybert et al (2001) suggest a reinterpretation of the results of Morro da Igreja and Serra do Rio do Rastro, showing that the expansion of the Atlantic rain forest about 10,000 yr BP was related to temperature and moisture increase. More information of new records at additional sites, including pollen concentration diagrams, is necessary to clarify this question.…”

“…The higher moisture after 5000 yr BP is seen also in other registers from South Brazil (20°S or higher), which had been interpreted to suggest El Niño type events resulting in higher precipitation and more stable moisture conditions (Martin et al, 1991;Ybert et al, 2001). About 5000 and 4000 yr BP maximum marine transgression occurred over the adjacent Coastal Plain of Rio Grande do Sul highlands (Kowsmann et al, 1977;Villwock and Tomazelli, 1998), affecting the coastal vegetation (Lorscheitter, 2003).…”

Morphology of the Itapeva to Tramandai transgressive dunefield barrier system and mid‐ to late Holocene sea level change

“…Angulo et al (1996Angulo et al ( , 1999 indicate that sea level reached a maximum height of +2·0 m in South Brazil (Santa Catarina State) only 100 km to the north of RS, while Angulo and Lessa (1997) suggest that the maximum height was +3·5 m around 5·2 ka BP in the States of Sao Paulo and Parana to the north of RS. Ybert et al (2001) state that during the period c. 4400 to 3250 years BP sea level remained at least 2 m higher than at present. Angulo et al (1996Angulo et al ( , 2006, Angulo and Lessa (1997) and Ybert et al (2001) all indicate that sea level then fell relatively smoothly to the present level.…”

“…In general, the curves indicate a sea level rising (transgressing) above the present level until around 5·1 ka BP Angulo et al, 2006), possibly remaining high until c. 3·25 ka BP (Ybert et al, 2001), then falling (Angulo et al, 2006).…”

Morphological and temporal variations of transgressive dunefields of the northern and mid-littoral Rio Grande do Sul coast, Southern Brazil

“…B) Trend lines for the yearly total drift potential for Imbé (Martinho, 2008(Martinho, ). 1998Behling et al, 1999;Ybert et al, 2001;Bauermann et al, 2003). This coincidence of soil formation and wet climate indicates that the climate might be controlling dunefield evolution on the RS coast since 5000 yr BP .…”