Interpretações paleoecológicas e tafonômicas de mamíferos quaternários em depósitos de tanques do Centro-Norte da Bahia, Brasil

Abstract

At the Brazilian Intertropical Region (BIR) the characteristic fauna was composed predominantly of megamammals and large mammals that lived until around nine thousand years before present (B.P.). Recent studies have increasingly demonstrated that the BIR would not be a totally homogeneous zone, presenting distinct niches and that the Pleistocene fauna would not be geochronologically restricted to the Late Pleistocene, but that it was also present during the Middle Pleistocene and reached the Holocene, a period in which they place the extinction of megafauna, according to the most accepted hypotheses. In this work we sought to understand the paleoenvironmental dynamics that occurred in fossiliferous outcrops of the tank type, located in the municipality of Jaguarari - Lajedo II site and in the municipality of Campo Formoso in the Toca do Novilho and Baixão sites, located in the Territory of Identity Piemonte Norte do Itapicuru in the Central - North portion of Bahia, in Caatinga domain. For this purpose, Pleistocene mammal fossils were collected for isotopic analysis ( 13C) in order to infer about the diet of these animals, determine the trophic niche of the species and identify the degree of overlap and competition for resources. Taphonomic signatures were identified and evaluated in the studied fossiliferous accumulations in order to perform a comparative study on a regional scale in the Center-North of Bahia, in order to explain the variations in signatures between tank deposits and thus understand the depositional history of the studied tanks. The fauna in Jaguarari was represented by seven taxa, three megamammals and four large mammals. Five taxa were grazers, one a ramoneer and one a predator, five generalists and two dietary specialists. At Toca do Novilho, 10 taxa were identified, four megamammals and six large mammals. Seven taxa were grazers; two ramblers and one predator, seven generalists and three dietary specialists. In Baixão 12 taxa were recorded, three megamammals; eight large mammals and one medium-sized mammal. Six taxa were grazers; two ramblers; one folivore; one omnivore and two predators, seven generalists and five dietary specialists. Regarding the taphonomic aspects, Lajedo II presents itself as an internally complex accumulation with a minimum temporal mixing rate estimated at ± 20 years. Toca do Novilho presents itself as an internally complex accumulation with a minimum temporal mixing rate estimated at ± 5 years. In these two tanks, hydraulic transport was the main taphonomic process in the deposit, producing a peripheral assemblage with a possible spatial mixing. Baixão presents itself as an internally simple accumulation with a minimum temporal mixing rate estimated at ± 8 years, with hydraulic transport as the main taphonomic process in the deposit, producing a peripheral assemblage with a possible synchronous accumulation. From the data obtained, it is suggested that Jaguarari and Campo Formoso present heterogeneous regions regarding vegetation and climate with differentiation of niches along their extension. The three deposits studied present similarities in terms of taphonomic aspects, when compared to other Quaternary tanks in Brazil.