Geochemical evidence of the 8.2 ka event and other Holocene environmental changes recorded in paleolagoon sediments, southeastern Brazil

Abstract

The paleoclimatic record of Juréia Paleolagoon, coastal southeastern Brazil, includes cyclic and gradual changes with different intensities and frequencies through geological time, and it is controlled by astronomical, geophysical, and geological phenomena. These variations are not due to one single cause, but they result from the interaction of several factors, which act at different temporal and spatial scales. Here, we describe paleoenvironmental evidence regarding climatic and sea level changes from the last 9400 cal yr BP at the Juréia Paleolagoon – one of the main groups of protected South Atlantic ecosystems. Geochemical evidences were used to identify anomalies from multi-proxy analyses of a paleolagoon sediment core. The anomalies of centennial scale were correlated to climate and transgression–regression cycles from the Holocene period. Decadal scale anomalous oscillations in the Quaternary paleolagoon sediments occur between 9400 and 7500 cal yr BP, correlated with long- and short-term natural events, which generated high sedimentation rates, mainly between 8385 and 8375 cal yr BP (10 cm/yr). Our results suggest that a modern-day short-duration North Atlantic climatic event, such as the 8.2 ka event, could affect the environmental equilibrium in South America and intensify the South American Summer Monsoon.

Holocene Environmental Climatic Changes Based on Palynofacies and Organic Geochemical Analyses from an Inland Pond at Altitude in Southern Brazil

“…According to [44], anomalies in the southeastern Brazil show a high degree of correlation with cooler conditions associated with the North Atlantic 8.2 ka event which appears to have affected the environmental equilibrium in South America and intensified the South American summer monsoon. In Brazil, this event had effects of short duration, approximately a few hundred years, and would have increased local precipitation and humidity and sea level rise [44].…”

“…In Brazil, this event had effects of short duration, approximately a few hundred years, and would have increased local precipitation and humidity and sea level rise [44]. The 8.2 ka event is one of the most well-known climate events of global extent [44] [77]- [85].…”

“…In Brazil, this event had effects of short duration, approximately a few hundred years, and would have increased local precipitation and humidity and sea level rise [44]. The 8.2 ka event is one of the most well-known climate events of global extent [44] [77]- [85]. These results suggest (according with [44]) that a modern-day short-duration North Atlantic climatic event, such as the 8.2 ka event (and perhaps other Bond events), could affect the climate dynamics in South America.…”

“…For the Brazilian Holocene, the studies of [35] using speleothems allowed correlations in global scale evidencing strong events of increased precipitation centered at 9.2, 8.2, 7.4, 7.0, 6.6, 5.2, 4.0, 3.2, 2.7, 2.3, 2.2, and 1.9 ka yr BP, which are synchronous with the Bond events [36] [37]. Based on the striking correlation between ice-rafted debris (IRD) records in North Atlantic sediment cores and tropical rainfall, the Bond IRD events have been used to link shifts in the intensity of the Atlantic thermohaline circulation to changes in sea surface temperature (SST) and related precipitation anomalies over areas affected by the monsoons in Oman [38], Asia [39], South America [40]- [42] and Brazil [35] [43] [44]. Unluckily, the absence of any crystalline deposit that could potentially generate speleothems in Rio Grande do Sul State has impeded, until the moment it correlated this kind with the Bond events, the palynological [45] [46] and palynofaciological records [24] that led to inferring cyclical climatic oscillations for the Holocene.…”

Reconstituição paleoambiental de uma área no baixo curso do Rio Ribeira de Iguape com base em bio e geo indicadores

“…Por volta de 3.200 anos cal AP (médias das idades de 145 cm) o ambiente já se comportava como um pântano, há aumento na concentração de Bignoneaceae (Tabebuia), Cluseaceae (Clusia) e novamente Amaranthaceae PESSENDA, et al, 2009;LUZ, 2003;DULEBA, et al, 2005SALLUN et al, 2012;SILVA, 2013) A ciência que estuda os grãos de pólen, esporos de pteridófitas e briófitas, tanto fósseis como atuais, é a Palinologia. A palinologia do Holoceno pode fornecer informações paleoclimáticas e ecológicas muito precisas, pois envolve contribuição e estudos sobre as comunidades vegetais atuais e suas características ecológicas (TRAVERSE, 1988;LUZ, 2003).…”