Biogenic sedimentary structures

Biogenic sedimentary structures are evidence of organism–substrate interactions preserved in rocks and sediments, including those recorded in estuarine environments. Their study is termed “paleoichnology” (from the Greek palaios ¼ old, ancient and ichnos ¼ a trace, a track), whereas similar studies in modern sediments are referred to as “neoichnology.” Markings that do not reflect the behavior of organisms (e.g., marks made by the shells of dead mollusks passively transported on the seafloor by waves and/or currents) are excluded from the trace fossils. In addition, biogenic sedimentary structures do not include body fossils (direct remains, such as shells, bones, teeth, etc.) or molds of organism bodies.