Late Pleistocene-Holocene fossils from Mirim Lake, Southern Brazil, and their paleoenvironmental significance
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Journal of South American Earth Sciences
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Mirim Lake is located in the southern Brazilian/northeastern Urugayan coastal plain. Fossils of mollusks have
been discovered on its shores since the XIX century, and in recent years, several new remains of invertebrates
and vertebrates have been found in the Brazilian area of the lake that provide insights on the geological evolution
and environmental changes that affected this lake during the late Quaternary. In this first of two papers
describing these new findings we focus on vertebrates, consisting of aquatic and terrestrial taxa. The former
include the first associated fossil remains of one adult and one juvenile balaenid whale known in Brazil, probably
a female and calf of the southern right whale (baleia-franca) Eubalaena australis, besides bull sharks
(Carcharhinus leucas) also recorded for the first time in southern Brazil, rays (Dasyatidae and Myliobatidae) and
teleost fishes. The fossils of terrestrial vertebrates include several extinct mammals, found on the margins and
retrieved from the lake bottom by fishermen at depths of up to 4 m. One molar tooth of Toxodon discovered in
situ in one irrigation channel yielded an electron spin resonance (ESR) age of 68 ± 13 ka, in agreement with an
age of 32.8 ± 5.1 ka obtained in quartz grains extracted from a caliche nodule collected above that fossil and
dated by optically-stimulated luminescence (OSL). Other quartz grains in the same nodule that yielded ages of
16.9 ± 2.5 ka indicate partial dissolution of the caliche by increased rainfall at the beginning of the last glacialinterglacial
transition (Termination I) . The lake was invaded by marine waters and organisms during the
Holocene sea-level highstand of +3 m around 5–6 ka b2k through paleo-connections with the Atlantic Ocean,
becoming a paleo-lagoon. At that time coastal waters were warmer than today, as indicated by the presence of
the tropical shark C. leucas. The ESR and OSL ages indicate chronocorrelation with the Pleistocene fossil-bearing
Santa Vitória Formation that outcrops to the east. The fossil and sedimentary records indicate that the geological
evolution and environmental conditions of the lake were controlled by climate and sea-level oscillations related
to glacial-interglacial cycles.
Como referenciar
LOPES, RENATO P.; PEREIRA, JAMIL C.; DILLENBURG, SERGIO R.; TATUMI, SONIA H.; YEE, MARCIO; FIGUEIREDO, ANA M.G.; KINOSHITA, ANGELA; BAFFA, OSWALDO. Late Pleistocene-Holocene fossils from Mirim Lake, Southern Brazil, and their paleoenvironmental significance: I - Vertebrates. Journal of South American Earth Sciences, v. 100, p. 1-19, 2020. DOI: 10.1016/j.jsames.2020.102566. Disponível em: http://repositorio.ipen.br/handle/123456789/31385. Acesso em: 30 Dec 2025.
Esta referência é gerada automaticamente de acordo com as normas do estilo IPEN/SP (ABNT NBR 6023) e recomenda-se uma verificação final e ajustes caso necessário.