Determining sediment provenance history in a Gondwanan erg: Botucatu formation, Northern Parana Basin, Brazil

G. Bertolini*, J. C. Marques, A. J. Hartley, M. A. S. Basei, J. C. Frantz, P. R. Santos

*Corresponding author for this work

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Abstract

The Lower Cretaceous Botucatu Formation comprises a dry-aeolian system developed in western Gondwana and preserved within the Parana Basin of central South America. Multiproxy provenance analysis (detrital zircon U-Pb dating, heavy mineral, petrographic and granulometric analysis) was undertaken along two 500 km transects of the northern Parana Basin (NW and NE transects). To assess the provenance variation within the aeolian stratigraphy, samples were taken from the base and top of the Botucatu Formation and from sandstones interbedded with volcanics in the overlying Serra Geral Formation. Granulometric analysis shows a mean fine- to very fine-grained sand. The bulk petrography yields an average composition of Q(91)F(6)L(2), and heavy mineral analysis gives a mean of 86% of zircon-tourmaline-rutile, demonstrating the overall polycyclic nature of the sediment. The discrete occurrence of garnet, apatite and epidote indicates local sediment input points, providing indirect evidence for point-sourced fluvial input into an overall dry aeolian system. Detrital zircon U-Pb LA-ICP-MS dating demonstrates a dominant Cambrian to Late Neoproterozoic (520-750 Ma) population with subsidiary Tonian-Stenian (0.9-1.2 Ga) and Orosirian-Rhyacian (1.9-2.3 Ga) contributions. The Botucatu Formation along the northern basin margin displays similar provenance to the southern part of the basin, pointing to a predominance of recycling processes within the basin. Statistical plots illustrate the detrital zircon age variability recording an upward decrease in the age proportion of Permian and Tonian-Stenian populations and an increase in Cambrian-Late Neoproterozoic dates towards the top. Such variability can be related to the recycling of distinct Parana Basin strata. The proportion of Cambrian-Late Neoproterozoic dates increases in the NE, indicating a possible input from the Ribeira Belt granitoids. Similar to major-scale dune-fields, Botucatu erg register variable sand sources there are possibly linked with coexisting depositional systems. In summary, the northern Botucatu erg is mostly fed by local sources reworked from underlying Parana Basin units, with little direct input from basement sources and limited impact of regional wind-pattern variability. (C) 2021 Elsevier B.V. All rights reserved.

Original languageEnglish
Article number105883
Number of pages13
JournalSedimentary Geology
Volume417
Early online date6 Mar 2021
DOIs
Publication statusPublished - 15 May 2021

Keywords

  • Detrital zircon
  • Sedimentary provenance
  • Dune-field sand filling
  • Provenance
  • Heavy minerals
  • Botucatu Formation

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