Late Aptian paleoclimate reconstruction of the Brazilian equatorial margin: inferences from palynology
<p>This study conducted high-resolution paleoclimatic analyses based on the identification of palynological groups of late Aptian age (biozone <i>Sergipea veriverrucata</i>) in the Bragança and Codó formations within the Bragança–Viseu, São Luís, and Parnaíba basins. The analysis c...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2023-08-01
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| Series: | Climate of the Past |
| Online Access: | https://cp.copernicus.org/articles/19/1715/2023/cp-19-1715-2023.pdf |
| Summary: | <p>This study conducted high-resolution paleoclimatic analyses based on the
identification of palynological groups of late Aptian age (biozone
<i>Sergipea veriverrucata</i>) 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<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M1" display="inline" overflow="scroll" dspmath="mathml"><mo>/</mo></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="8pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="1b4178c77ca0d4bfee6c9ddd864f3a43"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cp-19-1715-2023-ie00001.svg" width="8pt" height="14pt" src="cp-19-1715-2023-ie00001.png"/></svg:svg></span></span>arid trend (<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M2" display="inline" overflow="scroll" dspmath="mathml"><mrow><mi mathvariant="normal">Fs</mi><mo>/</mo><mi>X</mi></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="28pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="6909d8a49d2a03ac83f4c19520329837"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cp-19-1715-2023-ie00002.svg" width="28pt" height="14pt" src="cp-19-1715-2023-ie00002.png"/></svg:svg></span></span>), 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: <i>Afropollis</i>, <i>Araucariacites</i>, <i>Callialasporites</i>, <i>Cicatricosisporites</i>, <i>Classopollis</i>, <i>Cyathidites</i>, <i>Deltoidospora</i>, <i>Equisetosporites</i>, and <i>Verrucosisporites</i>, with <i>Classopollis</i> 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.</p> |
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| ISSN: | 1814-9324 1814-9332 |