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Published March 15, 2015 | public
Journal Article Open

Combined ^(40)Ar/^(39)Ar and (U–Th)/He geochronological constraints on long-term landscape evolution of the Second Paraná Plateau and its ruiniform surface features, Paraná, Brazil


Regional correlation of dated weathered land surfaces provides the necessary constraints to test long-term continental landscape evolution models, but major challenges remain in properly dating these surfaces. The geomorphological province of Second Paraná Plateau, Paraná State, Brazil, is a high elevation (ca. 800 m) land surface characterized by widely distributed deep saprolites and scattered lateritic profiles (e.g., Vila Velha and Serra das Almas). Prolonged exposure to weathering and erosion has promoted the pseudo-karstic and ruiniform features that are characteristic of this landscape. In this study, ^(40)Ar/^(39)Ar laser incremental heating geochronology on 22 grains of supergene Mn oxyhydroxides from lateritic profiles at Vila Velha yielded results ranging from 17.2 ± 0.7 to 9.1 ± 0.7 Ma. (U–Th)/He geochronology on 28 goethite grains from the same profile yielded results ranging from 36.4 ± 3.6 to 1.0 ± 0.1 Ma, with an age cluster lying within the 17.2 ± 0.7 to 7.9 ± 0.8 Ma interval. (U–Th)/He geochronology on 17 goethite grains from the Serra das Almas lateritic profile, located 20 km from Vila Velha, yield results ranging from 35.1 ± 3.5 to 14.1 ± 1.4 Ma. The combined results for the two sites reveal a common weathering history that started ca. 35 Ma, suggesting that the Second Paraná Plateau results from regional fluvial incision and denudation before ~ 35 Ma, followed by a decline in denudation rates and proportionally more intense weathering. Consistent with the laterite profile central ages, weathering was particularly intense during the Miocene (17–8 Ma). Denudation intensified after the Pliocene.

Additional Information

© 2014 Elsevier B.V. Received 17 January 2014. Received in revised form 15 October 2014. Accepted 23 October 2014. Available online 18 December 2014. The authors are grateful for the financial support from CAPES (PhD scholarship 4862-06-6), and logistic and financial support from PETROBRAS/CENPES for the ^(40)Ar/^(39)Ar analyses. We are also thankful for the environmental license granted for research at Vila Velha Park (IAP no. 183/09). We are also grateful to the geologist Mathieu Moriss (Paradigm Softwares Technologies Inc.) for the support on DEM volume calculation with the GOCAD software. The construction of the UQ-AGES facility was partially funded by ARC Large Grant A39531815.

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August 22, 2023
August 22, 2023