Late Pleistocene-Holocene fossils from Mirim Lake, southern Brazil, and their paleoenvironmental significance: II - Mollusks

Autor(es):Mostrar menos -

Lopes, Renato Pereira ^[1] ; Pereira, Jamil Correa ^[2] ; Caron, Felipe ^[3] ; Ritter, Matias Do Nascimento ^[3] ; De Souza, Marcio Silva ^[4] ; Dillenburg, Sergio Rebello ^[1] ; Barboza, Eduardo Guimaraes ^[1] ; Tatumi, Sonia Hatsue ^[5] ; Yee, Marcio ^[5] ; Kinoshita, Angela ^[6] ; Baffa, Oswaldo ^[7]

Afiliação do(s) autor(es)

^[1] Univ Fed Rio Grande do Sul, Inst Geociencias, Ave Bento Goncalves, 9500, Caixa Postal, 15001, BR-91501970 Porto Alegre, RS - Brazil

^[2] Museu Coronel Tancredo Fernandes de Melo, Rua Barao do Rio Branco 467, BR-96230000 Santa Vitoria Do Palmar, RS - Brazil

^[3] Univ Fed Rio Grande do Sul, Ctr Estudos Costeiros Limnol & Marinhos, Av Tramandai 976, BR-95625000 Imbe, RS - Brazil

^[4] Univ Fed Rio Grande, Av Italia, Km 08, BR-96201900 Rio Grande, RS - Brazil

^[5] Univ Fed Sao Paulo, Campus Baixada Santista, BR-11070100 Sao Paulo, SP - Brazil

^[6] Western Sao Paulo Univ UNOESTE, PGMADRE Rodovia Raposo Tavares, Km 572, BR-19067175 Presidente Prudente, SP - Brazil

^[7] Univ Sao Paulo FFCLRP USP, Fac Filosofia Ciencias & Letras Ribeirao Preto, Dept Fis, Ave Bandeirantes 3900, BR-14040901 Ribeirao Preto, SP - Brazil

• Tipo de documento: Artigo Científico
• Fonte: Journal of South American Earth Sciences; v. 112, n. 1 DEC 2021.
• Citações Web of Science: 0

Resumo

The fossil molluscan assemblages found on the shores of Mirim Lake, in southern Brazil and Uruguay, provide information about the environmental changes and geological evolution of that water body. The storm-generated shell deposits at Latinos Spit on the Brazilian shore are dominated by the estuarine bivalve Erodona mactroides, represented mostly by juveniles, and the gastropod Heleobia australis. Species previously unrecorded in this site include the marine gastropods Cylichnella bidentata, Buccinanops cochlidium and Pachycymbiola brasiliana, and the bivalves Tagelus plebeius, Ostrea puelchana, Crassostrea cf. praia, Mactra isabelleana, Anomalocardia flexuosa and Cyrtopleura costata. The two latter currently inhabit tropical areas to the north of Rio Grande do Sul, and their presence in Mirim Lake indicates average coastal water temperatures about 2-3 degrees C warmer than today. This condition promoted the precipitation of calcium carbonate from dissolved shells, thus cementing together sand and shells in the form of coquinas. The stratigraphic succession, OSL ages obtained in quartz sand from one coquina, radiocarbon dated shells, and delta C-13 and delta O-18 of five E. mactroides and five marine species indicate that Mirim Lake became a brackish lagoon around 7.6 ka ago, in response to the postglacial marine transgression (PMT), followed by fully marine conditions during the sea-level highstand of 6-5 ka BP. Marine influence was reduced after similar to 4 ka BP as the result of sea-level fall and the closure of the connection with the ocean, related to the evolution of the sandy barrier that originated the modern shoreline. The environmental changes recorded in Mirim Lake help understand how coastal lagoons and their associated ecosystems respond to sea-level oscillations, which may be relevant to address future responses of these water bodies to the ongoing climate change. (AU)

• Processo FAPESP: 07/06720-4 - Avanços em dosimetria, datação arqueológica e caracterização de biomateriais por ressonância de spin eletrônico
• Beneficiário: Oswaldo Baffa Filho
• Modalidade de apoio: Auxílio à Pesquisa - Regular
• Processo FAPESP: 13/07699-0 - Centro de Pesquisa, Inovação e Difusão em Neuromatemática - NeuroMat
• Beneficiário: Oswaldo Baffa Filho
• Modalidade de apoio: Auxílio à Pesquisa - Centros de Pesquisa, Inovação e Difusão - CEPIDs