Banca de QUALIFICAÇÃO: André Mateus Valentim Alvim

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
STUDENT : André Mateus Valentim Alvim
DATE: 24/04/2024
TIME: 14:00
LOCAL: Sala de Videoconferência do IGD
TITLE:

Characterization of marine incursions (and water paleochemical conditions) using isotopic proxies: a study into the Acre and Araripe basins.

KEY WORDS:

stable isotopes, radiogenic isotopes, paleoenvironmental implications, zircon U-Pb geochronology, sedimentary provenance.

PAGES: 60
BIG AREA: Ciências Exatas e da Terra
AREA: Geociências
SUMMARY:

Brazilian intracontinental basins tend to present stratigraphic intervals of transitional and marine sedimentary deposition, demonstrating moments of seawater incursion into the continent, and intervals of anoxic paleoenvironmental conditions eventually (the latter are more common in marginal basins). The most used methods to investigate these phenomena, in addition to sedimentological and fossil analysis, are multi-element isotopic analyses, as they are useful for identifying possible intervals of marine influence and paleoenvironmental physicochemical parameters during sedimentary deposition. Therefore, the objective of the present work is to demonstrate how geochemical (Hg, TOC, major and trace elements) and isotopic (δ13Corg, δ13Ccarb, δ18Ocarb and 87Sr/86Sr and εNd) proxies in rock and fossil samples from the Romualdo Formation in the Araripe Basin and from the Solimões Formation in the Acre Basin behave in sediments coming from intervals where marine incursions and anoxic events have been pointed out in previous works. Furthermore, it is expected to use these proxies and zircon U-Pb dates in the study of the sedimentary provenance of these geological units. The partial results to be presented in the qualification show data on major and trace elements, TOC, total Hg, δ13Corg, δ13Ccarb and δ18Ocarb in three outcrops of the Romualdo Formation (Araripe Basin), in addition to data on δ13Ccarb and δ18Ocarb, 87Sr/86Sr and εNd in five outcrops of the Solimões Formation (Acre Basin). The isotopic data of the Romualdo Formation indicate that the most basal part of the black shales sequence was deposited in an anoxic environment with some influence from associated volcanic sediments, probably corresponding to paleoenvironments of the anoxic event OEA-1b (Aptian-Albian). Throughout the geological section of the unit, the suboxic redox character becomes predominant. In the Acre Basin, stable isotope data from the Solimões Formation point to fluvio-lacustrine continental sedimentation, as proposed by classic studies. Furthermore, 87Sr/86Sr and εNd data in carbonates and carbonate fossils and absolute dating by the U-Pb method on zircons from sandstones of the Solimões Formation indicate a greater sedimentary contribution from Andean source rocks (Altiplano and central depression) than of cratonic source rocks during sediment deposition.

COMMITTEE MEMBERS:
Externo ao Programa - 1297259 - CARLOS JORGE DE ABREU - nullInterno - 1178074 - GUILHERME DE OLIVEIRA GONCALVES
Interna - 1658822 - LUCIETH CRUZ VIEIRA
Interno - 2339865 - MARTINO GIORGIONI
Presidente - 418662 - ROBERTO VENTURA SANTOS