Banca de DEFESA: Wilson Humberto López Abanto

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : Wilson Humberto López Abanto
DATE: 22/08/2022
TIME: 08:30
LOCAL: Sala de videconferência do IGD
TITLE:

SEDIMENTARY PROVENANCE OF THE PONTA GROSSA AND SÃO DOMINGOS (DEVONIAN) FORMATIONS OF THE NW OF THE PARANÁ BASIN (BRAZIL): REGIONAL IMPLICATIONS FOR THE T-R EVENTS OF THE SW OF GONDWANA

KEY WORDS:

 Paraná Basin, Ponta Grossa and São Domingos formations, U-Pb geochronology, Sr-Nd isotopes, Provenance

PAGES: 96
BIG AREA: Ciências Exatas e da Terra
AREA: Geociências
SUMMARY:

The Paraná Basin is a typical intracratonic Basin located on the Brazilian platform. This basin recorded sedimentation from the Ordovician to the Cretaceous. Three major secondorder sea level variations related to tectonics and eustatic have occurred in southwestern Gondwana and are also recognized in the Paraná Basin. The first of these events was transgressive and it is related to the Precordillera orogeny I. In the Paraná Basin, the Furnas Formation is related to the sea level rise, and the shales of the Ponta Grossa Formation represent the maximum flood surface for this first transgression. The second sea level variation was regressive and is related to the Precordillera orogeny II. The sandstones of the Tibagi member of the São Domingos formation were related to the drop in sea level during this second event. The third event was again transgressive and it is related to a global rise in sea level. This event has been related to the shales of the upper part of the São Domingos Formation. As there is a very restricted relationship between stratigraphy and sea level variations for the Paraná Basin during the Devonian, this master's thesis was developed to test these sea level variations with U-Pb dating studies on detrital zircon and Sr-Nd isotope. Five samples from the northern part of the Paraná Basin, including two from the Ponta Grossa Formation, two from the Tibagi member and one from the São Domingos Formation. For our discussion, we take into account: 1) paleocurrent data indicating that the main provenance for the northern part of the Paraná basin was from the ENE-W, and subordinate from the E; and 2) we assume that the current paleogeographic configuration of the basin is a substitute for paleogeography during the Devonian. This allows classifying the probable sources into near, intermediate, and distal: the Goiás magmatic arc (~630 Ma) would represent a near source, the Serra da Mesa, Paranoá Group, and Goiás block (~1770 Ma and 2100 Ma for the Serra da Mesa, and only ~2100 Ma for the Paranoá Group, and ~2420 Ma for the Goiás block) would represent intermediate sources; and the Trairas Group (~1520 and 2604 Ma), the Sunsas belt (~900- 1200 Ma) and the Famatinian magmatism (~435 Ma) could represent distal/very distal sources, respectively. The main difference between the provenance patterns of the three units is an age peak of ~2604 Ma, which is only observed in the upper part of the São Domingos Formation and can probably be related to the Trairas Group. As the upper part of the São Domingos Formation recorded the second transgressive event, this peak is related to a very distal source, such as the Trairas Group, which would represent the basement of the Brasília range to the NE, today ~500 km from the basin. The peak at ~435 Ma that was observed in the Ponta Grossa Formation (4% zircon), Tibagi (3% zircon) and São Domingos Formation (6% zircon), but not in the underlying Furnas Formation, can be explained as direct source of the Famatinian magmatic arc, located ~1100 km away or zircons with these ages derived from the reworking of the Tarija Basin, which is located about 650 km to the West and was possibly linked to the Paraná Basin in the Devonian. Also the 87sr/86Sr(380) ratios and the TDM values show a decrease when there are contributions from younger sources, as is the case of the Ponta Grossa Formation and the upper part of the São Domingos Formation where there is a greater presence of very young sources, sources associated with the Famatinian magmatic arc. viii Thus, distal/very distal sources are observed for the first transgression, represented by the Ponta Grossa Formation, and then recorded again for the second transgression in the upper part of the São Domingos Formation. We can conclude that u-Pb provenance analysis on detrital zircon and Sr - Nd isotopes can be applied to recognize sea level variations in a basin.

BANKING MEMBERS:
Interno - 113.138.381-87 - CARLOS JOSE SOUZA DE ALVARENGA - AMU
Externa à Instituição - EDI MENDES GUIMARAES
Externo à Instituição - MIGUEL ANGELO STIPP BASEI - USP
Presidente - 1897668 - NATALIA HAUSER