Landscape changes in the Campos region, southernmost Brazil, since the early deglaciation based on a multi-proxy analysis of a peat bog

• Published in: Palaeogeography, palaeoclimatology, palaeoecology palaeoclimatology, palaeoecology, 2023-08, Vol.623, p.111631, Article 111631
• Main Authors: Bocalon, Vitor Luiz Scartazzini, Coimbra, João Carlos, Bauermann, Soraia Girardi, Ritter, Matias do Nascimento, Pivel, Maria Alejandra Gómez, De Oliveira, Marcelo Accioly Teixeira, Primam, Gisele Leite de Lima
• Format: Article
• Language: English
• Subjects: Deglaciation; Holocene; Late Pleistocene; Paleoclimatology; Palynology; Río de La Plata Grasslands
• ISSN: 0031-0182; 1872-616X
• DOI: 10.1016/j.palaeo.2023.111631

The paleoecological evolution of a peat bog in the Campos region, Rio Grande do Sul State, Brazil, was determined based on an integrated study of stratigraphy, palynology, and geochronology. The peat bog is constituted of silty-clay material, with high levels of ash (residue on ignition) and organic matter content that was deposited on a sandy substrate. Palynological analysis show that grassland taxa dominated from the base of the core at the early deglacial (∼17.4 cal kyr B.P.) to the Present. Four pollen zones were identified: CCQ I Zone (3.20 m to 2.50 m), covering the deglaciation (Upper Pleistocene), corresponding to dry climate conditions; CCQ II Zone (2.50 m to 1.60 m, latest deglaciation and Early Holocene), associated with a slightly humid climate; CCQ III Zone (1.60 m to 0.50 m, mid to late Holocene), established under very humid climatic conditions; and CCQ IV Zone (0.50 m to 0.00 m, last ∼500 years), representative of a low-humidity period. The floristic composition of grassland communities observed throughout the drill core is very similar to that found in the region where the municipality of Cacequi is located, in which Poaceae, Asteraceae, Fabaceae, and Rubiaceae were identified as the most abundant families. Consequently, although in the last ∼17.4 cal kyr B.P. the humidity oscillated, the grassland vegetation remained predominant, although not being represented by the same families, as indicated by changes in the floristic composition among the four pollen zones. Palynological and geochronological data, when compared with other sectors of the Río de la Plata Grasslands, show a predominance of dry conditions over the studied interval. From the early deglacial until the Present, climatic fluctuations shaped the diversity of plant communities and affected the particularities of each sector of the Río de la Plata Grasslands, including the Campos region. High ash content was detected along the core, similar to what occurs with other peatlands already studied in Brazil. In the peat bog analyzed, Poaceae is the predominant family, being known as a major producer of biomineralized structures, which would explain the high ash content recorded. •We present a multiproxy study of a peat bog core from the Campos region, Southern Brazil.•Pollen families from the Rio de La Plata Grasslands are described for the first time.•Our results are consistent with drier climatic conditions during the deglaciation.•Results support a regional trend of increased hum