Interpreta????es paleoambientais do quatern??rio da bacia de Santos (Brasil) com base em foramin??feros bent??nicos

A distribui????o das associa????es e abund??ncia de esp??cies de foramin??feros bent??nicos est?? condicionada a diversos fatores ecol??gicos, ligados intrinsecamente a aspectos f??sicos e qu??micos dos oceanos. A partir de 68 amostras provenientes de dois testemunhos do talude continental da Bacia de Santos (aproximadamente 2.000 metros de l??mina d?????gua), analisou-se a fauna de foramin??feros bent??nicos, bem como os is??topos est??veis de carbono e oxig??nio das carapa??as. Por meio do estudo sistem??tico da fauna de foramin??feros bent??nicos foram identificados 68.998 esp??cimes pertencentes a 123 esp??cies. A caracteriza????o ecol??gica das esp??cies identificadas, somada ?? an??lise quantitativa de seus padr??es de distribui????o, possibilitou o registro de altera????es no conjunto microfaun??stico, atribu??das aos diferentes eventos clim??ticos. As maiores flutua????es na abund??ncia relativa ao longo dos testemunhos resultam dos padr??es das tr??s principais esp??cies: Pseudoparrella exigua, Alabaminella weddellensis e Cassidulina californica. P. exigua tem maior abund??ncia nos est??gios glaciais, caracterizando esses per??odos como fortemente influenciados por aportes sazonais de fitodetritos, enquanto A. weddellensis domina nos est??gios interglaciais, indicando uma deposi????o mais intensa e cont??nua de material org??nico. J?? C. californica, que teve abund??ncia expressiva tanto em glaciais como em interglaciais, responde a quantidades elevadas de carbono org??nico total nos sedimentos. Embora sejam indicadoras de alta produtividade, essas esp??cies n??o apresentaram uma liga????o estreita com as ??guas ricas em nutrientes que dominam nos per??odos glaciais. Por??m, varia????es na abund??ncia relativa sugerem per??odos com distintas intensidades de fluxo de nutrientes e diferentes origens da mat??ria org??nica depositada no assoalho oce??nico nos ??ltimos 545 mil anos.The distribution of assemblage and species abundance is conditioned to several ecological factors, related to physical and chemical oceanic aspects. Were analyzed 68 samples of two cores collected in continental slope of Santos Basin (~2,000 m water depth) in relation to the benthic foraminiferal fauna, as well as the stable isotopes of carbon and oxygen extracted in shells. Through the systematic study of the benthic foraminiferal fauna were identified 68,998 specimens belonging to 123 species. The ecological characterization of species, in addition to the quantitative analysis of the distribution patterns in the cores, allows the observation of changes in the abundance of certain species, attributed to different climatic events. The largest fluctuations in relative abundance along the cores result from the pattern of three main species: Pseudoparrella exigua, Alabaminella weddellensis e Cassidulina californica. Pseudoparrella exigua is more abundant during glacial stages, characterizing these periods as strongly influenced by seasonal phytodetritus input, while Alabaminella weddellensis dominates in the interglacial stages, indicating a more intense and continuous deposition of organic material. Cassidulina californica, that had significant abundance in both stages, responds to high amount of total organic carbon in sediments. Even being indicative of high productivity, these species did not show a close link with the nutrient-rich waters that dominate the glacial stages. However, variations in relative abundance suggest periods with different intensities of flow of nutrients and different sources of organic matter deposited on the ocean floor in the last 545 kyr