Late Aptian paleoclimate reconstruction of the Brazilian equatorial margin: inferences from palynology

This study conducted high-resolution paleoclimatic analyses based on the identification of palynological groups of late Aptian age (biozone Sergipea veriverrucata) in the Bragança and Codó formations within the Bragança–Viseu, São Luís, and Parnaíba basins. The analysis comprised 40 palynological sa...

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Bibliographic Details
Published in:	Climate of the past Vol. 19; no. 8; pp. 1715 - 1742
Main Authors:	Cardoso da Silva Giannerini, Michelle, de Araujo Carvalho, Marcelo, Cunha Lana, Cecília, Santiago, Gustavo, de Paula Sá, Natália, da Cunha Correia, Gabriel
Format:	Journal Article
Language:	English
Published:	Katlenburg-Lindau Copernicus GmbH 25-08-2023 Copernicus Publications
Subjects:	Affinity Analysis Angiosperms Aquatic plants Aridity Basins Bioclimatology Biometeorology Bryophytes Climate Convergence zones Ferns Flora Gymnosperms Humidity Humidity trends Hydrophytes Indicator organisms Indicator species Intertropical convergence zone Lithology Paleoclimate Palynology Parameter identification Plants Species diversity Statistical analysis Statistical methods Stratigraphy Trends Xerophytes Brazil Rio de Janeiro Brazil
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Summary:	This study conducted high-resolution paleoclimatic analyses based on the identification of palynological groups of late Aptian age (biozone Sergipea veriverrucata) in the Bragança and Codó formations within the Bragança–Viseu, São Luís, and Parnaíba basins. The analysis comprised 40 palynological samples, with 200 palynomorphs per slide counted when possible. Bioclimatic analysis was mainly supported by the identification of botanical affinities, and ecological and climatic parameters such as the wet/arid trend (Fs/X), Shannon–Wiener diversity, and indicator species analysis (IndVal) were used. Statistical analyses such as principal component and cluster analyses were employed to support the paleoclimatic interpretations. The study recognized 69 genera distributed among the main groups of living plants, including bryophytes, ferns, lycophytes, gymnosperms, and angiosperms. It was possible to attribute botanical affinity in 94.2 % of the taxa, and nine genera occurred in all sections studied: Afropollis, Araucariacites, Callialasporites, Cicatricosisporites, Classopollis, Cyathidites, Deltoidospora, Equisetosporites, and Verrucosisporites, with Classopollis being the most abundant. The stratigraphic distribution of the bioclimatic groups (hydrophytes, hygrophytes, lowland tropical flora, upland flora, and xerophytes) allowed for the identification of climatic phases: pre-evaporitic, evaporitic, and post-evaporitic. In the pre-evaporitic phase, the most significant abundances were between the hygrophytes and upland flora, indicating a certain level of humidity. Xerophytes were the most abundant in all phases, with a conspicuous increase in the evaporitic phase, reflecting an increase in aridity. In the post-evaporitic phase, there was a significant increase in the upland flora with the return of wetter conditions. This study confirmed an increasing humidity trend in the analyzed sections, probably owing to the influence of the Intertropical Convergence Zone that was already operating during the late Aptian.
ISSN:	1814-9332 1814-9324 1814-9332
DOI:	10.5194/cp-19-1715-2023