Paulo César Fonseca Giannini

Relative sea-level changes in the last 5500 years in southern Brazil (Laguna–Imbituba region, Santa Catarina State) based on vermetid 14C ages

Abstract Twenty-six new radiocarbon dates from vermetid shells collected in the southernmost sector of the Brazilian rocky coast presented dates ranging from 5410±80 to 190±65 years B.P., with associated paleosea levels varying from +2.10 m to +0.20 m above present sea level. The overall suggested trend of the relative sea level (RSL), declining until at least 190 years B.P., is somewhat contradictory to a proposed RSL rise in the last 1000 years in southern Brazil. The data also seem to undermine a more widely accepted RSL trend that suggests that at least two negative RSL oscillations occurred between 4100 and 3800 years B.P. and between 3000 and 2700 years B.P. The maximum elevation of the RSL in the Holocene in southern Brazil was possibly lower than that observed in most of the Brazilian eastern coast. Discrepancies between ancient sea levels of similar ages are attributed to coincidental methodological problems, to imprecisions in determining past relative sea levels and to possible changes in the geomorphology and wave climate close to shore during the last 5000 years. A general trend of increasing δ 18 O with a reduction in age in the studied samples may suggest a gradual reduction of water temperature in the region during the same period.

Building Coastal Landscapes: Zooarchaeology and Geoarchaeology of Brazilian Shell Mounds

ABSTRACT Brazilian shell sites are largely considered to have been multifunctional and the location of both sacred and secular activities. This article explores the joint contribution that zooarchaeological and geoarchaeological analysis can bring to understanding the depositional history of shell sites and their functions. This combined approach is applied to the study of two shell mounds that represent important aspects of the diverse array of shell sites found along the southern Brazilian coast. Jabuticabeira II is a monumental shell mound that has shown unquestionable evidence of being used mainly as a cemetery, and Encantada III is a smaller shell deposit whose function is more difficult to define. Research focusing on formation processes at Jabuticabeira II played an important role in developing a better understanding of the mortuary rituals performed at the site. In Encantada III, zooarchaeology and geoarchaeology contribute to a better characterization of its role as a short-term deposit of long-lasting permanence. Both shell sites and their practical and symbolical attributes represent examples of the complex dynamics of the anthropic construction of a landscape.

Geologia e geomorfologia do quaternário costeiro do estado do Rio Grande do Norte

O objetivo deste trabalho e a apresentacao de um mapa geologico-geomorfologico preliminar para o Quaternario costeiro do Estado do Rio Grande do Norte, com destaque para os depositos eolicos. O mapa foi elaborado a partir de fotografias aereas, escala 1:70.000, imagens de satelite (P/B, banda 4), escala 1:100.000, mapas topograficos e trabalhos de campo. Foram feitas datacoes 14C em rochas praiais e depositos de paleomangues e datacoes por termoluminescencia em sedimentos eolicos e marinhos. Nos depositos eolicos foram identificados tres dominios geomorfologicos de dunas inativas e um de dunas ativas. Eles formaram-se no Quaternario a partir de retrabalhamento de areias da propria planicie costeira e de sedimentos da Formacao Barreiras. As idades TL de 36 amostras indicam que os depositos eolicos foram formados durante seis intervalos principais: 390.000 - 326.000, 270.000 - 240.000, 210.000 - 150.000, 63.000. - 24.000, 11.000 - 9.000 e, 6.500 anos - presente. Essas idades sugerem sua deposicao tanto durante estagios glaciais como interglaciais, relacionados a niveis relativos de mar baixos e altos respectivamente. Dois terracos marinhos foram identificados, com idades de 210.000 a 214.000 anos e 110.000 a 120.000 anos. O primeiro ocorre entre Natal e Baia Formosa, onde a costa se orienta na direcao N - S; o segundo encontra-se no trecho da costa entre Sao Bento e Zumbi, com orientacao E - W. Extensos depositos de intermare holocenicos, principalmente de arenitos praiais, estao localizados na costa orientada N - S e apresentam idades entre 7.000 - 6.000 anos AP. e 5.500 - 4.500 anos AP.

Interações entre evolução sedimentar e ocupação humana pré-histórica na costa centro-sul de Santa Catarina, Brasil

Since the beginning of the human occupation in the south-central coast of Santa Catarina State, in Brazil, the articulation between natural and anthropic processes modeled a strongly domesticated landscape, shaped by the massive construction of shell mounds of monumental dimensions and millenarian permanence. In the coastal plain between Passagem da Barra (Laguna District) and Figueirinha Lake (Jaguaruna District), 76 sambaquis were mapped, 48 of which have been dated. Systematic site surveys and radiocarbon datings allowed identifying patterns of spatial distribution in sambaquis according to the sedimentary context at the time of construction, stratigraphy and age. Based on these criteria, the following groups were recognized: five geological-geomorphological contexts of location; three stratigraphic patterns; and four phases of sambaqui occupation in the area, based on site number and type of constructive pattern. The model for sedimentary evolution and time-space distribution of sambaquis shows that sites were built in already emerged areas and that inland sites, away from the lagoons, may have not be preserved or they are not exposed due to the continuous sedimentary filling that characterized this region after the maximum Holocene transgression. The crossing of data, here proposed, shows the importance of integral approaches between archaeology and geosciences for the study of landscape evolution.

Araçatuba Formation: palustrine deposits from the initial sedimentation phase of the Bauru Basin

A Bacia Bauru (Cretaceo Superior), acumulou uma sequencia sedimentar continental essencialmente arenosa. Numa fase inicial desertica, o seu substrato basaltico foi soterrado por extensa e monotona cobertura de areias eolicas com intercalacoes subordinadas de depositos de loesse. O relevo original do substrato favoreceu a formacao de uma drenagem regional endorreica, sob clima semi-arido, propiciando assim condicoes de formacao do Paleopantanal Aracatuba. Os depositos paludiais (Formacao Aracatuba) constituem estratos tabulares de siltitos e arenitos de cor cinza claro esverdeado tipica, eventualmente cimentados por carbonato de calcio. Moldes e pseudomorfos de cristais de gipsita e dolomita foram identificados na unidade. Aparentemente, estao associados com gretas de ressecacao, marcas de raizes e intervalos com laminacao tipo climbing ripple, que indicam ambiente de aguas salinas rasas e relativamente calmas, submetidas a fases de exposicao subaerea e ressecacao. Nos limites da area de ocorrencia da Formacao Aracatuba, as unidades arenosas podem exibir feicoes sigmoides e estratificacao contorcida, comuns em depositos deltaicos marginais. A Formacao Aracatuba e contornada e posteriormente encoberta por depositos eolicos da Formacao Vale do Rio do Peixe.

Shell mounds as environmental proxies on the southern coast of Brazil

Despite the multiple constraints of using shell mounds for building relative-sea-level (RSL) curves, one of the premises behind this use is still valid in modern archaeological research. This refers to the sites being continuously built near bodies of water rich in fish species and mollusk beds. Studies that combine the evolution of settlement patterns with the geological evolution of coastal areas in Brazil reach analogous results: the distribution of shell mounds in time and space follows the landscape transformations induced by RSL variations through the Holocene. Although shell mounds are not precise indicators of RSL, they provide evidences of the paleo-geographical changes during the Holocene, of which RSL is one of the many control variables. By collecting and transporting mollusks to the shell mounds, humans inevitably carry sediments from the substrate where mollusks live, for example, the beaches and lagoons near the sites. In this work, the geoarchaeological study of three shell mounds located in the southern coast of Santa Catarina State, combined with mollusk taxa identification, show the direct association of shell mound content with the changing landscape. The predominance of Ostrea sp. versus Anomalocardia brasiliana, the presence of colluvial versus lagoonal sediments, and the occurrence of echinoid spines versus muddy aggregates with diatoms, gastropods, and glauconitic clay characterize the distinction between sites built before and after the maximum Holocene transgression, respectively. This attests the potential of geoarchaeological analyses in shell mounds as a complementary proxy for paleo-environmental reconstructions.

Luminescence characteristics of quartz from Brazilian sediments and constraints for OSL dating

This study analyzes the optically stimulated luminescence (OSL) characteristics of quartz grains from fluvial, eolian and shallow marine sands of northeastern and southeastern Brazil, with especial focus on the applicability of the single-aliquot regenerative dose (SAR) dating protocol. All analyzed Brazilian sediments presented relatively high OSL sensitivity and good behavior regarding their luminescence characteristics relevant for radiation dose estimation. However, some samples from the Lencois Maranhenses region in northeastern Brazil showed inadequate OSL sensitivity correction, hampering the implementation of the SAR protocol and their ability to behave as a natural dosimeter. While the shallow marine and eolian samples showed a narrow and reliable dose distribution, the fluvial sample had a wide dose distribution, suggesting incomplete bleaching and natural doses estimates dependent on age models.

Optically stimulated luminescence and isothermal thermoluminescence dating of high sensitivity and well bleached quartz from Brazilian sediments: from Late Holocene to beyond the Quaternary?

The development of optically stimulated luminescence (OSL) dating of sediments has led to considerable advance in the geochronology of the Quaternary. OSL dating is a well established technique to determine sediment burial ages from tens of years to few hundred thousand years. Recent studies have shown that Quaternary sediments of Brazil are dominated by quartz grains with high luminescence sensitivity, allowing the determination of precise and reliable OSL burial ages. In this paper, we show examples of OSL dating of quartz aliquots and single grains from different regions in Brazil, including young coastal-eolian Late Holocene ( 2 Ma) in the low dose rate (0.5 - 1.0 Gy/ka) environments typical for Brazilian sediments.

Radarfacies and sedimentological analysis: Study of sedimentary substrate from an archaeological site (shell mound), southern Brazil

Integrated results of GPR (Ground Penetrating Radar) and sedimentological analysis are presented for the Jabuticabeira II archaeological site (shell mound), Santa Catarina, Brazil. By means of radarfacies identification, this study aims to delimit the archaeological site and differentiate the coastal depositional systems that compose its substrates. For these purposes, available models of the temporal–spatial distribution of depositional systems in the area were used and sedimentological analysis (granulometry, quantification of heavy minerals and clay-mineral characterization) were performed on samples spaced at 0.5-m vertical intervals in auger drills cutting the identified radarfacies. GPR data were obtained along a radial grid, which allowed the rapid mapping of a large area (several hundred square metres). The results allowed to characterize an archaeological layer, the soil and two sedimentary layers (palaeolagoon and aeolian) in the substrates under and around the site. The high porosity and the grain size, cementation and heavy mineral segregation contrasts along wind-controlled laminations are for the reflector sharpness in the aeolian deposits. The archaeological site settlement mostly overlies the palaeolagoon, which was a newly emerged land during the epoch of occupation and is situated on the margins of aeolian deposits that formed in the region after the Holocene maximum flooding. This configuration reinforces the sambaquis occupation model of south-central Santa Catarina during the Holocene, strongly controlled by the proximity to lagoon bodies. The resolution of the data in this study was sufficient to advance our understanding of the regional sedimentary evolution and its relation with sambaqui occupation.

Central Santa Catarina coastal dunefields chronology and their relation to relative sea level and climatic changes

During the past decades, there have been contrarian explanations for the formation and stabilization of coastal dunefields: while many authors believe the dunes formation would be enhanced by falling sea level, others argue that a rising or stable sea level context would be favorable. For Brazilian coastal dunefields, the second hypothesis seems to be more consistent with the luminescence ages found so far; however, most of these data were obtained without using the SAR protocol. Another point of concern is the role of climate change in the aeolian system, which is still not very clear. The aim of this paper is to try to clarify these two questions. To this end, five coastal dunefields were selected in central Santa Catarina coast. The remote sensing and dating results allowed the discrimination and mapping of at least four aeolian generations. Their age distribution in relation to the global curve of relative sea level variation during the Late Pleistocene allows us to suggest that the formation of Aeolian dunefields in the coastal context is supported by stable relative sea level. However, relative sea level is not the only determinant for the formation and preservation of the aeolian coastal dunes. Evidences of climatic control indicate that the initiation of dunefields would be favored by periods of less humidity while their stabilization would occur preferably during the periods of rain intensification, connected to monsoon activity.