Holocene climate changes, sea-level oscillations and humans impact in northeastern BrazilDoctoral thesis
Date of Examination:2022-07-21
Date of issue:2022-12-05
Advisor:Prof. Dr. Hermann Behling
Referee:Prof. Dr. Erwin Bergmeier
Referee:Prof. Dr. Daniela Sauer
Referee:Prof. Dr. Dirk Hölscher
Persistent Address: http://resolver.sub.uni-goettingen.de/purl?ediss-11858/14385
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Name:PhD thesis-Caio FINAL.pdf
EnglishDuring the Holocene, the environment in northeastern Brazil has changed mainly due to climate dynamics, human activities, and in the coastal area, sea-level oscillations. However, little is known about the environmental history of this region due to a lack of palaeoenvironmental studies. To improve the understanding of these impacts, a multi-proxy analyses have been conducted and discussed in this thesis focused on the long-term changes. In the eastern part of northeastern Brazil, a palaeoenvironmental study has been developed in a mire at the Catimbau National Park, State of Pernambuco, to reconstruct the climate changes and the human impact during the last 2800 cal yr BP. The study site is located in the semi-arid Caatinga dry forest, and the results distinguished three distinct environmental periods. From 2800 to 2150 cal yr BP, the vegetational composition had a predominance of Cecropia, indicating a dry condition in a strong disturbed environment. The indicators suggested a presence of humans in the region since the beginning of the record, which became more intense in the followed period from 2150 to 450 cal yr BP. In this interval occurred an increase of arboreal vegetation indicating wetter conditions. Conditions which were favorable for the local community expansion and, as consequence, their stronger influence on the environment. The evidence of humans was corroborated with the presence of pollen grains of Phaseolus (beans) and Orbignya palm (babaçu). After 450 cal yr BP, the analysis showed a return of drier conditions associated with more open vegetation, and a decline of the local population. The northern part of northeastern Brazil, two studies were carried out in the Maranhão State coastal zone to understand the climate change, sea-level oscillations, and the human impact. The study areas are located more than 120 km far from the current coast. However, the records showed a presence of mangrove coastal ecosystem since around 8000 cal yr BP, suggesting the transgression of the Atlantic Ocean during the early to mid-Holocene. The palynological, mineralogical and chemical parameters indicated a highstand of the sea-level between 5500 and 5020 cal yr BP. The mangrove displacement had also been influenced by the climate changes, which showed a tendency for the drier condition from around 8000 until 5000 cal yr BP. After 5000 cal yr BP, the sea-level dropped, the freshwater supply increased, and the arboreal vegetation, typical from Amazon rainforest, expanded due to wetter conditions. Those conditions were responsible for the abandonment of the mangroves from the study area. Since around 2500 cal yr BP, the records suggested the presence of Amerindians in the study areas. Both sites were the first palaeoenvironmental reconstruction of archaeological sites in the region to understand their impact on the landscape. Unique anthropological evidence suggested that the Amerindians were living upon the rivers and the lakes in stilt-house settlements, making those evidence the only ones found from the pre-colonial period in South America.
Keywords: Holocene, Vegetation dynamics, Climate changes, Sea-level oscillations, Human impacts, Northeastern Brazil, Paleoclimate, Fire history, Palynology.