Invertebrate and vertebrate trace fossils from continental carbonates

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

Carbonates in continental settings. Elsevier. Dev. in Sedimentology 61

Elsevier

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

A variety of trace-fossils assemblages have been recorded from continental carbonates. In some cases, they correspond to archetypal ichnofacies or incipient ichnofacies, and in some instances the cases are too few to include the associations in the ichnofacies model. The Coprinisphaera ichnofacies, dominated by the eponymous ichnogenus, includes examples that occur in paleosols generally containing a lesser amount of carbonate than the incipient Celliforma ichnofacies. The latter has been formerly proposed and is here supported by new study cases for calcretes and mostly palustrine carbonates. This ichnofacies is characterized by Celliformidae, particularly Celliforma, R. sciuttoi, and subordinate beetle trace fossils, as well as rhizoliths. Also typical of these paleosols is the presence of hackberry endocarps and gastropod shells. The Celliforma ichnofacies, where occurring in terrestrial settings, would be indicative of low plant coverage due to an arid climate typical of desert scrubs and dry woodlands. When present in a palustrine environment, it would reflect the presence of bare soil, preferred by wasps and bees to nest, after periodic waterlogging under subhumid to sub-arid climates. In other cases, in palustrine environments, alternating subaqueous and subaerial exposure may involve less time of subaerial exposure than necessary for the development of the well-aerated soil profiles required for insects to nest. In such cases of short subaerial exposure, the Scoyenia ichnofacies trace-fossil assemblage may develop. This ichnofacies based on meniscate burrows and vertebrate footprints is present in low-energy, ramp-margin successions of carbonate-dominated basins and evaporitic lake basins. Finally, the subaqueous trace-fossil assemblages from low-energy bench, steep-gradient successions in carbonate-dominated lacustrine basins are considered as representative of a depleted Mermia ichnofacies. This ichnofacies is characterized by simple horizontal trails and trackways in permanently subaqueous settings. A single case of carbonate eolianites with trace-fossil assemblages has been assigned to the Psilonichnus ichnofacies. There have been some attempts to group vertebrate trace fossils into ichnofacies and to integrate them into the invertebrate-based ones. The Brontopodus ichnofacies is characterized by the abundance of widegauge and narrow-gauge sauropod tracks and associated theropod tracks occurring in carbonate or evaporitic facies of tidal flats and alkaline2saline lakes. The shorebird ichnofacies and the Avipeda ichnocoenosis within the Grallator ichnofacies, from carbonate-dominated, wave-influenced successions, mixed carbonate/siliciclastic and evaporitic lacustrine basins, are characterized by shorebird tracks and occur with mammal footprints, rare invertebrate trails, and root traces.