the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
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
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)
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RC1: 'Comment on cp-2023-22', Mercedes di Pasquo, 27 May 2023
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General comments
This is an interesting palynological analysis applied to the Aptian (Cretaceous) paleoclimatic interpretation of northern Brazil, supported by previous taxonomic and botanical affinity studies mainly carried out in Brazil, as well as paleoenvironmental and climatic interpretations of the wells.
It is recommended to improve the writing in English and correct errors, especially those parts marked with color in the attached file. Review spelling mistakes of some author´s names in Appendix 1 (e.g. valid Potonié)
My leading suggestions related to partially reorganizing the information of some parts of the text and making clarifications to improve its understanding. For this, see the details below and the balloons indicated along the text in the attached pdf file.
The manuscript has adequate illustrations and citations.
Summary of main comments
Lines 67…: please clarify the meaning of "relationships ..." in terms of interpreting paleoclimate changes.
Possibly, it can be improved by rewriting this part with the following long sentence and avoiding repetitions
What do you mean by "indicator species"?
Try rewriting the sentence to make clear the purpose of those "selected taxa"
("diagnostic taxa" or "proxy-taxa" or "sensitive climatic taxa")
Line 99 up to the end of item 3: It is not clear whether these phases and the supersequences mentioned herein resulted from this study or previous one/ones, please clarify or cite at the beginning the corresponding refs.
Once again, it is not clear if this part /item is all concerning Milani et al. or if there are things related to the present study
Item 4.2: Is the CENPES the repository of the samples?
Which is the acronym of the collection?
Line 168: please clarify, are these conditions referring to the interpretation given to sample levels of wells? Who has done this part? please, cite references
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AC1: 'Reply on RC1', Marcelo Carvalho, 31 May 2023
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Thanks very much for your comments. We very much appreciate the time and effort the reviewer dedicated to revising our manuscript. We agree with all of the reviewer's feedback and will address them in detail in the revised manuscript. We will briefly address some of the reviewer's comments at this stage.
Lines 67…: please clarify the meaning of "relationships ..." in terms of interpreting paleoclimate changes.
We will rewrite this sentence because it is indeed confusing.
What do you mean by "indicator species"?
In this case, we have already started introducing the approach of the Indicator Species Index (IndVal), used in this study and in other studies.
Line 99 up to the end of item 3: It is not clear whether these phases and the supersequences mentioned herein resulted from this study or previous one/ones, please clarify or cite at the beginning the corresponding refs.
Actually, we based our work on the study by Milani et al. 2007 and Carvalho et al., 2022. Indeed, we are missing the references.
Item 4.2: Is the CENPES the repository of the samples?
"Yes, we will add the information.
Line 168: please clarify, are these conditions referring to the interpretation given to sample levels of wells? Who has done this part? please, cite references
The botanical affinities were obtained from various articles that will be referenced. The bioclimatic groups were based on the work of Carvalho et al., 2022.
Thank you for your feedback. We appreciate your suggestion to improve the writing in English and correct any errors. We will carefully review the spelling mistakes of the author's names in Appendix 1. Your input is valuable, and we will make the necessary revisions.
Citation: https://doi.org/10.5194/cp-2023-22-AC1
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AC1: 'Reply on RC1', Marcelo Carvalho, 31 May 2023
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Michelle Cardoso da Silva Giannerini et al.
Michelle Cardoso da Silva Giannerini et al.
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