Climatically induced changes in late Quaternary bathyal ostracod assemblages of the Camamu Basin, Brazil

The ostracod genus Bradleya Hornibrook is an important taxon of Cenozoic assemblages, occurring practically in all oceanic regions. The wide distribution both in shallow and deep waters turns Bradleya interesting for studies involving phylogeny and paleoceanography. The present work aims at the study of fossil and recent species in South America and adjacent regions, based on bibliographic review and the restudy of samples from the Brazilian continental margin, the Navidad Formation (lower Miocene) and El Peral Beds (meso-upper Miocene), both cropping out in the Central Chile. The chronostratigraphic, (paleo)bathymetric and (paleo)zoogeographic distribution of the species is reviewed and updated. The bridge composition was studied in all species recorded and revealed to be important taxonomic character. The taxa identified were gathered into three morphological groups: two proposed previously (i.e., the dictyongroup and the arata-group) and a new one in the present work (i.e., the normani-group).The dictyon-group and the arata-group gather deep-sea species, while the normanigroup is predominantly neritic, including most of the species of Brazilian margin. Bradleya victorjaraisp. nov. is proposed for the Miocene of Chile, and Bradleya ybate (Bergue et al.) is reassigned to Rigracythere gen. nov. Questionable or misidentified species ascribed to Bradleya are briefly discussed.

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Paleoenvironmental significance of Benthic Foraminifera and Ostracoda from the late Quaternary of the Ceará Basin, Brazilian Equatorial Margin

Noucoucouk

Silva

Melo

et al. 2023

Braz. J. Geol.

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Benthic foraminifera, ostracods and pteropods are reliable paleoenvironmental indicators in Quaternary deposits. However, in the Ceará Basin, on the Brazilian Equatorial Margin, these microfossils are poorly studied. This paper investigates environmental changes during the Pleistocene-Holocene transition in the Icaraí subbasin based on micropaleontological analysis of the core ANP 1011. Seventy-four taxa of benthic foraminifera, represented predominantly by Globocassidulina, Uvigerina, Pyrgo and Melonis, have been identified. The ostracod assemblages are composed mainly by the families Macrocyprididae, Cytheruridae, Trachyleberididae, Pontocyprididae and Krithidae, of which the genus Krithe was the most abundant. The composition of the ostracod assemblages identified in this study area differs somewhat from other regions of the Brazilian Margin. The assemblages of foraminifera and ostracod characterize a typical bathyal paleoenvironment. The occurrence of pteropods and dominance of epifaunal foraminifera taxa, mainly Pyrgo sp. and Miliolinella sp. in the lower portion of the core (Pleistocene), indicates higher phytodetritus input and oxygen concentration. A conspicuous environmental change was observed in the upper portion of the core, which corresponds to the Holocene, where the increase of infaunal foraminifera (e.g., Uvigerina, Globocassidulina and Melonis) suggests reduction in the organic matter input and, probably, increased bacterial density and depletion in dissolved oxygen in the sediment.

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Climatically induced changes in late Quaternary bathyal ostracod assemblages of the Camamu Basin, Brazil

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References 46 publications

Holocene deep-sea ostracods of the São Paulo Ridge, São Paulo Plateau, and Rio Grande Rise, southwestern Atlantic Ocean

Holocene deep-sea ostracods of the São Paulo Ridge, São Paulo Plateau, and Rio Grande Rise, southwestern Atlantic Ocean

The genus Bradleya Hornibrook, 1952 (Crustacea: Ostracoda) in South America and adjacent oceanic areas, with description of a new bradleyine genus

Paleoenvironmental significance of Benthic Foraminifera and Ostracoda from the late Quaternary of the Ceará Basin, Brazilian Equatorial Margin

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