Trace fossils in carbonate rocks

Most terrigenous clastic sequences have calcareous equivalents, and trace fossil suites well known from terrigenous clastic sediments have their counterparts in carbonates. Well-studied examples include trace fossils from situations in which carbonate fades predominate: the Bahaman-type shallow-water environment—as represented by European Mesozoic and tropical Pleistocene limestones; and pelagic ooze—as represented by shelf-sea and deep-sea chalks, the latter now available for study as a result of the Deep Sea Drilling Project. In shallow water carbonates, trace fossil associations range from beach-shoal assemblages having Ophiomorpha, to Thalassinoides-Rhizocorallium-Chondrites-dominated intertidal and sub-in deep-sea chalks, a Zoophycos-Teichichnus-Chondrites association dominates. Special problems associated with carbonates are (1) the influence of penecontemporaneous cementation on trace-producing organisms, (2) hardgrounds, and (3) the role of organisms in the diagenesis of sediment: differential cementation, concretion formation, and aggregation into pelletal limestones.