Etude préliminaire du remplissage sédimentaire de l’Igue du Gral et implications pour l’accumulation des restes fauniques

Bone caves such as sinkholes constitute remarkable sources of information for researchers interested in the paleoecology of fossil faunas. Moreover, these accumulations contain assemblages not or little affected by human intervention and can, therefore, serve as a source of comparison and contrast with contemporaneous assemblages from archaeological sites. In both cases, understanding the geomorphological context and the sedimentary dynamics remains fundamental when proposing interpretations on the formation of the assemblages. Here we present a preliminary study of the sedimentary filling of the Igue du Gral sinkhole (Sauliac-sur-Célé, Lot, France). The filling contains among other a sequence rich of vertebrate remains from the Upper Pleistocene, the Lateglacial and the Holocene. Stratigraphic, sedimentological and micromorphological analysis of the sinkhole sedimentary filling allows us to identify four main units. Unit 4 corresponds to a filling phase probably before the last interglacial and is currently observed in a secondary room of the cavity (East diverticulum). The other units correspond to the Upper Pleistocene-Holocene filling phase and are observed in the main room of the cavity. It is shown that units 3 and 2, which contain most of the paleontological assemblage currently studied, have accumulated by solifluction. We suggest that these assemblages correspond to thanatocenoses, first accumulated in a talus fan located directly above a chimney giving access to the cavity and then re-deposited by solifluction in the main room. Beyond the paleontological interest of this site, extending the studies of the sedimentary fillings will allow improving knowledge on frost action in sinkhole systems.