Jaibaras tectonossequence Genesis (Ediacaran - Ordovician) and its inheritance in the sedimentation of Serra Grande sequence (Ordovician - Silurian), northeast edge of Parnaíba Basin

Author(s)

Rodrigo Irineu Cerri

• Document type: Doctoral Thesis
• Press: Rio Claro. 2021-04-12.
• Institution: Universidade Estadual Paulista (Unesp). Instituto de Geociências e Ciências Exatas. Rio Claro
• Defense date: 2021-03-05
• Advisor: Lucas Verissimo Warren; Mario Luis Assine

Abstract

Syneclises or intracratonic basins are long-lived sedimentary basins characterized by complex subsidence and erosion histories, and their origin is currently one of the most prolific topics in the geologic sciences. Historically debated, the controversial premise that these geotectonic units evolve by thermal (or flexural) subsidence after a primeval rift basin is widespread, and to this day remains a controversial issue. However, the complexity of these basins and the reduced knowledge about their geochronological, architectural and provenance evolutions do not allow to satisfactory falsify this hypothesis. Considering this problematic, we proceeded a novel and integrated multi-proxy study, aiming to identify differences (and/or similarities) in the sedimentary signal and source areas of the Jaibaras (rift) and Parnaíba (intracratonic) basins, Ceará State, Brazil. Thus, we performed a detailed analysis integrating geochemistry of trace elements in detrital rutile grains, U-Pb geochronology of detrital zircon, macroscopic provenance and paleocurrents from the sedimentary deposits of the Aprazível Formation (Ediacaran - Cambrian, top of Jaibaras rift Basin) and the Ipu Formation (Ordovician, basal unit of Parnaíba intracratonic Basin). Our provenance analysis results demonstrate that conglomerates of the rift sequence are predominantly composed of volcanic, sedimentary, and metamorphic angular to sub-angular clasts, pointing to a diverse, nearby source area. On the other hand, conglomerates deposits of the initial sag sequence have greater sedimentary maturity, with dominant rounded quartz vein clasts and other subordinated lithologies, indicating provenance from distant source areas. The geochemistry of trace elements performed in detrital reinforce that the source areas of these two units were distinct, revealing an important decrease in the input of granulite facies and metamafic grains in the Parnaíba Basin comparing with the Jaibaras Basin. The maximum depositional age for the Aprazível Formation (ca. 499 ± 5 Ma) indicates Cambrian age for the upper part of the Jaibaras Basin succession, and Early Cambrian age for the Ipu Formation (ca. 528 ± 11 Ma). The fact that the maximum deposition age of the Ipu formation is older than the Aprazível Formation reflects distal sources different from those present in the limits and interior of the Jaibaras Basin. The U-Pb data together with palynological ages of Tianguá Formation suggest that the deposition of Ipu Formation started at the Late Cambrian/Early Ordovician. The provenance analysis based on detrital zircon data also indicate that the orogenic mountains areas related to the Brasiliano Orogeny at the south/southeastern of Borborema Province (e.g., Rio Preto and Riacho do Pontal metamorphic belts), were the most probable primary source areas for the initial deposition of the Parnaíba Basin. Finally, our data emphasizes the key change in source areas from the rift to the sag phase, indicating that there is no continuity between the sedimentation of both basins and strongly suggesting that the Parnaíba Basin probably did not evolved from a precursor rift basin. (AU)

• FAPESP's process: 17/19550-1 - Jaibaras tectonossequence genesis (Ediacarano - Ordoviciano) and its inheritance in the sedimentation of Serra Grande sequence (Ordoviciano - Siluriano), Northeast edge of Parnaíba Basin
• Grantee: Rodrigo Irineu Cerri
• Support Opportunities: Scholarships in Brazil - Doctorate