Invertebrate and vertebrate trace fossils from continental carbonates

Abstract

This chapter presents a review of trace-fossil assemblages from carbonate sediments deposited in continental settings, including carbonate-rich paleosols, lacustrine and eolian carbonates, and examples from travertine and tufas. Carbonate-rich paleosols from the Paleozoic are scarce and trace fossils are mostly only briefly described; Mesozoic examples are more abundant and better studied, although associations of trace fossils cannot now be included in the ichnofacies model because of a lack of recurrence. The Cenozoic shows the largest and best studied cases of trace fossils in carbonate-rich paleosols. Two Seilacherian ichnofacies can be recognized: the Coprinisphaera ichnofacies, which occurs in paleosols, probably with a relatively low carbonate content, and the Celliforma ichnofacies, which occurs in sediments with a higher carbonate content. The latter, developed in either pedogenic or palustrine carbonates, displays a recurrent association of insect trace fossils dominated by bee and wasp ichnofossils, particularly Celliforma ichnospecies and Rebuffoichnus sciuttoi, associated with fresh-water and terrestrial gastropods and hackberry endocarps. Seven cases and three additional possible examples of these assemblages are reviewed in detail. They range in age from Late Cretaceous to Miocene and are known from South and North America, Europe and Africa. These examples are used to further support an incipient Celliforma ichnofacies. The Celliforma ichnofacies would be indicative of a drier climate and lower vegetation coverage than those represented by the Coprinisphaera ichnofacies, particularly for scrubs to woodlands. The examples of trace-fossil assemblages from lacustrine carbonates are more numerous (39 cases cited in this chapter) as well as more varied. These examples can be subdivided into assemblages from carbonate-dominated, mixed carbonate/siliciclastic, and evaporite lacustrine basins. The Mermia ichnofacies is represented by a few cases of subaqueous trace-fossil assemblages. Carbonate microbial/caddisfly mounds constitute a distinctive biogenic structure from carbonate-dominated and wave-agitated littoral lacustrine facies, although no ichnofacies assignment is possible to date. Some cases of intermittently exposed and submerged shallow-lacustrine deposits, where the subaerial exposure was not enough to allow insects to nest, can be ascribed to the Scoyenia ichnofacies. Many trace-fossil assemblages contain tetrapod tracks and invertebrate traces in shallow lacustrine facies that were frequently exposed and submerged. Some of the Mesozoic examples have been attributed to the Brontopodus ichnofacies, whereas the Cenozoic examples (containing shorebird and mammal footprints) have been regarded as representing the “shorebird ichnofacies” or Grallator ichnofacies. A case assignable to the later ichnofacies, from the Triassic Ischichuca Formation (Argentina), is discussed in more detail. In addition, a few examples of trace-fossil assemblages from late Cenozoic carbonate eolianites are summarized. One of these examples was tentatively considered as representative of the Psilonichnus ichnofacies.