Vertebrate taphonomy in circum-lake environments: three cases in the Guadix-Baza Basin (Granada, Spain)

This work analyses the origin and taphonomy of three Plio-Pleistocene mammal assemblages from the Guadix-Baza basin (Granada, Spain): Huélago; Huéscar-1; and Cúllar de Baza-1. Similarities and differences in the taphonomic features are evaluated with regard to marginal lacustrine sedimentary processes involved in the accumulation of these mammal assemblages. Selective preservation of skeletal-part and taxa in relation to facies have been explored to determine their suitability for palaeoecological analysis. The mortality in Cúllar de Baza-1 and Huélago-1 corresponds to a catastrophic pattern, but other taphonomic features of the bones indicate that accumulation processes were diachronic as occurred in Huéscar-1. This could be explained by selective-predation and/or seasonal accumulation of bones. Hydraulic sorting and transportation greatly controlled the size and shape of accumulated skeletal elements, and the different preservational circumstances of each environment largely constrained the taxonomic composition of the fossil bone assemblages. Autochthonous fauna only occurs in Huéscar-1 corresponding to subaquatic environments. The absence of carnivores among the identifiable remains from Huélago-1 has no plausible taphonomic or sedimentological explanation. Nevertheless, after taking into account the taphonomic factors, the differences in taxonomic composition between these three mammal assemblages reflect differences in the surrounding habitats. The great diversity of ruminant artiodactyls, in particular browsers, is indicative of wooded or bushy areas in the surroundings of Huélago-1 although not in the immediate area of the lake margin. This diversity coincides with that observed in other Villafranchian localities and represents the greatest diversity of artiodactyls known from the Neogene and Quaternary record of Western Europe. In turn, the high diversity of sub-aquatic forms and a smaller variety of artiodactyl species in Huéscar-1, reflects an open, sparsely forested environment susceptible to seasonal drought. A similar sparse forested environment has been deduced for Cúllar de Baza-1. The climate and environmental conditions in Huéscar-1 and Cúllar de Baza-1 are consistent with a climatic deterioration at the beginning of the Middle Pleistocene (‘Glacial Pleistocene’).