Invertebrate and vertebrate trace fossils from continental carbonates

GENISE, J., MELCHOR, R., BELLOSI, E. AND VERDE, M.

Carbonates in continental settings. A. M. Alonso-Zarza & L. Tanner (eds.). Developments in Sedimentology, 61. Elsevier.

Elsevier

Lugar: Amsterdam; Año: 2010; p. 319 - 369

A variety of trace-fossils assemblages have been recorded fromcontinental carbonates. In some cases, they correspond to archetypalichnofacies or incipient ichnofacies, and in some instances the cases are toofew to include the associations in the ichnofacies model. The Coprinisphaeraichnofacies, dominated by the eponymous ichnogenus, includes examplesthat occur in paleosols generally containing a lesser amount of carbonatethan the incipient Celliforma ichnofacies. The latter has been formerlyproposed and is here supported by new study cases for calcretes and mostlypalustrine carbonates. This ichnofacies is characterized by Celliformidae,particularly Celliforma, R. sciuttoi, and subordinate beetle trace fossils, as wellas rhizoliths. Also typical of these paleosols is the presence of hackberryendocarps and gastropod shells. The Celliforma ichnofacies, where occurringin terrestrial settings, would be indicative of low plant coverage due to anarid climate typical of desert scrubs and dry woodlands. When present in apalustrine environment, it would reflect the presence of bare soil, preferredby wasps and bees to nest, after periodic waterlogging under subhumidto sub-arid climates. In other cases, in palustrine environments, alternatingsubaqueous and subaerial exposure may involve less time of subaerialexposure than necessary for the development of the well-aerated soilprofiles required for insects to nest. In such cases of short subaerialexposure, the Scoyenia ichnofacies trace-fossil assemblage may develop. Thisichnofacies based on meniscate burrows and vertebrate footprints is presentin low-energy, ramp-margin successions of carbonate-dominated basins andevaporitic lake basins. Finally, the subaqueous trace-fossil assemblages fromlow-energy bench, steep-gradient successions in carbonate-dominatedlacustrine basins are considered as representative of a depleted Mermiaichnofacies. This ichnofacies is characterized by simple horizontal trails andtrackways in permanently subaqueous settings. A single case of carbonateeolianites with trace-fossil assemblages has been assigned to the Psilonichnusichnofacies. There have been some attempts to group vertebrate trace fossilsinto ichnofacies and to integrate them into the invertebrate-based ones.The Brontopodus ichnofacies is characterized by the abundance of widegaugeand narrow-gauge sauropod tracks and associated theropod tracksoccurring in carbonate or evaporitic facies of tidal flats and alkaline2salinelakes. The ‘‘shorebird ichnofacies’’ and the Avipeda ichnocoenosis withinthe Grallator ichnofacies, from carbonate-dominated, wave-influencedsuccessions, mixed carbonate/siliciclastic and evaporitic lacustrine basins,are characterized by shorebird tracks and occur with mammal footprints,rare invertebrate trails, and root traces.