Desert Ichnofaunas: spatial and temporal perspectives

BUATOIS, LUIS; MANGANO, MARIA GABRIELA; MARSICANO, CLAUDIA; KRAPOVICKAS, VERONICA

Conferencia; International Conference Continental Ichnology; 2017

Although deserts are commonly regarded as having a poor ichnologic record, analysis of tracefossils in space and time may provide valuable insights into secular changes in biotic compositionand colonization patterns. Deserts encompass a wide variety of mosaics of habitats or physicalunits associated reflecting variable patterns of organism activity. Trace-fossil distribution may helpto understand the partitioning of desert settings in a mosaic of landscape units through geologictime. Five main phases of colonization of desert environments through the Phanerozoic arereconstructed. The first phase (Cambrian-Silurian) involved animal incursions into coastal dunefields directly from the sea, although it is unlikely that these animals would have remained for longperiods of time in coastal deserts. The second phase (Devonian) reflects pioneer invasion of eoliandunes by organisms that left their fluvial habitat to enter temporary or permanently into inlanddeserts. The third phase (Carboniferous-Permian) involved the colonization of deserts bytetrapods. The fourth phase (Triassic-Cretaceous) consists of a major exploitation of the infaunalecospace as revealed by the appearance of more varied behavioral patterns in infaunal structures.The fifth phase (Paleogene-Recent) signals reflects the appearance of modern desert communities.The invertebrate ichnofacies for eolian dunes is re-named as the ?Octopodichnus-EntradichnusIchnofacies?, whereas the Chelichnus ichnofacies is retained for vertebrate trace-fossilassemblages in eolian settings. Landscape units, such as eolian sand seas, salt flat and playa lakesystems, ephemeral rivers and alluvial fans, provide local spatial heterogeneity and interact inresponse to regional-scale climate variations in hyper-arid, arid, and semiarid climatic settings.