05 May 2023
 | 05 May 2023
Status: this preprint is currently under review for the journal CP.

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

Michelle Cardoso da Silva Giannerini, Marcelo de Araujo Carvalho, Cecília Cunha Lana, Gustavo Santiago, Natália de Paula Sá, and Gabriel da Cunha Correia

Abstract. This study conducted high-resolution paleoclimatic analyses based on the identification of palynological groups from the 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 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, evaporites, and post-evaporites. 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 already operated during the late Aptian.

Michelle Cardoso da Silva Giannerini et al.

Status: open (until 30 Jun 2023)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on cp-2023-22', Mercedes di Pasquo, 27 May 2023 reply
    • AC1: 'Reply on RC1', Marcelo Carvalho, 31 May 2023 reply

Michelle Cardoso da Silva Giannerini et al.

Michelle Cardoso da Silva Giannerini et al.


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Short summary
This study analyzed ancient climate patterns using plant fossils called palynomorphs. We identified 69 different palynomorphs from different plant groups (e.g., ferns, gymnosperms, angiosperms), and used statistical methods to support our findings. We found a trend towards increased humidity, likely influenced by a weather phenomenon called the Intertropical Convergence Zone.