Condiciones áridas durante el Holoceno Temprano en el sudoeste de la provincia de Buenos Aires (Argentina): vertebrados y tafonomía

Abstract

Fishes, amphibians, birds, marsupials, armadillos, and rodents are described from a Holocene site located at Camping Americano, near Monte Hermoso (38° 57' 47" S 61° 22' 48" W, Buenos Aires province, Argentina). The fossil bearing sediments are referred to the Lower Holocene on the basis of a radiocarbon AMS date of 8.9 yr BP. The assemblage is largely dominated by the caviomorph rodent Cienomys, with low frequencies of sigmodontines (Eligmodontia, Reithrodon), marmosines (Lestodelphys), edentates and other vertebrates. Severallines of evidence suggest a multiple taphonomical orígín, including owl pellets, water transport and in situ burial. This interpretation plus the presence of some faunistic elements of xeric environments [as the marmosine Lestodelphys halli (Thomas)] and a low specific richness of sigmodotine rodents indicate that the assemblage were deposited under dryer clima tic conditions than the present ones. Additionally, the global faunistic evidence, such as the high frequency of the octodontid Ctenomys or the bone concentrations of the fish Corydoras, suggests an interdune paleoenvironment with small fresh-water bodies, similar to the general landscape dominating nowadays the sandy "Southern barrier" of southwest Buenos Aires Province. According to the present intertidal location of the studied deposits, the absolute chronology and the inferred paleoenvironment, the former position of the coast line is discussed.