Work

Beyond the ergs: alluvial signature at the margins of the cretaceous Botucatu–Twyfelfontein paleoerg (SW Gondwana) and insights from U–Pb zircon geochronology

Year: 2026

Type: article

Abstract: The sedimentary record of large paleoergs is typically dominated by extensive dune fields deposits, but their margins often preserve evidence of alluvial systems that played an important role in sediment supply. Here, the provenance of such marginal alluvial deposits in the Botucatu (Brazil) and Twyfelfontein (Namibia) formations, remnants of a vast Cretaceous desert developed in southwestern Gondwana, is determined through integrated heavy mineral analysis and U-Pb detrital zircon geochronology. Different provenance signatures between these units can be traced: (i) the Botucatu Formation is characterized by dominant Neoproterozoic-Cambrian zircon crystals sourced from the Brasília Orogen, while (ii) the Twyfelfontein Formation contains Neoproterozoic-Cambrian zircon peaks along with Permian-Triassic age populations associated with the Karoo Basin. These findings redefine our understanding of the Botucatu-Twyfelfontein paleoerg as a system in which alluvial networks, activated during episodic rainfall, supplied sediment to dune fields, followed by subsequent eolian transport. This paper presents a model for sediment routing from marginal alluvial systems in the Botucatu–Twyfelfontein paleoerg system and potentially analogous settings for the mega-ergs of Gondwana during the final aridification phase. It demonstrates that these alluvial systems were fed by different basement sources for the Botucatu and Twyfelfontein formations (the Brasília Orogen and Choiyoi Magmatic Belt in South America; the Damara Orogen and Karoo Basin, with additional volcanic ash input, in Africa). Heavy mineral indices and zircon morphologies reveal contrasting degrees of sediment reworking and maturity between the two units and reinforce the scenario of distinct alluvial systems fed by opposite basin margins.

Source: Journal of South American Earth Sciences

DOI: 10.1016/j.jsames.2026.106251

Authors: Leandro Gustavo da Silva Albino, Rodrigo Irineu Cerri, Lucas Verissimo Warren, Paulo César Fonseca Giannini, Luciano Alessandretti, Gabriel Bertolini

Institutions: Universidade Estadual Paulista (Unesp), Universidade de São Paulo, Universidade Federal de Uberlândia, University of British Columbia

Language: English

Topic: Geological and Geochemical Analysis

Subfield: Geophysics

Field: Earth and Planetary Sciences

Domain: Physical Sciences

Open Access status: hybrid

Estimated APC paid: $2,940

Funders: Fundação de Amparo à Pesquisa do Estado de São Paulo, Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, Conselho Nacional de Desenvolvimento Científico e Tecnológico, Agência Nacional do Petróleo, Gás Natural e Biocombustíveis