Post-magmatic sedimentation in the Paraná Basin, Brazil: paleomagnetic constraints on the age of the Cretaceous Caiuá Group

Author(s)

Ernesto, Marcia ; Batezelli, Alessandro ; Saad, Antonio Roberto ; Caminha-Maciel, George ; Oliveira, Paloma G.

• Document type: Journal article
• Source: BOLETIN DE LA SOCIEDAD GEOLOGICA MEXICANA; v. 76, n. 3, p. 13-pg., 2024-01-01.

Abstract

The Caiu & aacute; and Bauru Groups of Cretaceous age, represent the post-volcanic sedimentation in the Paran & aacute; Basin. Under dry conditions, extensive dunes (Draa) were formed with depocenter in the southern area. Later, under more humid conditions, the fluvial-aeolian processes reworked the dunes, forming a landscape with small dunes and river channels. The Caiu & aacute; Group comprises, in ascending stratigraphic order, the Goio Er & ecirc; Formation (margins of Draa), the Rio Paran & aacute; Formation (inner Draa) and the Santo Anast & aacute;cio Formation (Paleosols). Paleomagnetic results from five sections of the Caiu & aacute; Group (Rio Paran & aacute; and Santo Anast & aacute;cio formations) revealed that these rocks carry remanent magnetization due primarily to magnetite and smaller contents of hematite. A paleomagnetic pole at 87.4 degrees S 56.6 degrees E (N=29, A95=6.5 degrees, k=18) for the Caiu & aacute; Group plots close to the poles from the dyke swarms (Ponta Grossa, Florian & oacute;polis and the alkaline dykes from Paraguay) of ages 134-127 Ma, indicating that the sedimentation of the Caiu & aacute; Group was restricted to the Lower Cretaceous. Furthermore, as part of the rocks were magnetized under transitional and reversed fields, the upper age limit is probably 120 Ma, the initiation of the Cretaceous Normal Superchron, and therefore not younger than the Barremian age. (AU)

• FAPESP's process: 20/07997-4 - Dinosaur diversity and associated faunas in the Cretaceous of South America
• Grantee: Max Cardoso Langer
• Support Opportunities: Research Projects - Thematic Grants