Ichnological analysis: A tool to characterize deep-marine processes and sediments

The deep-marine environment is a complex setting in which numerous processes —settling of pelagic and hemipelagic particles the water column, sediment gravity flows (downslope density currents; turbid flows), bottom currents— determine deposition, hence variety facies including pelagites/hemipelagites, contourites, turbidites hyperpycnites. Characterization differentiation among deep-sea challenge, features may be highlighted to this end: sedimentary structures, geochemical data, micropaleontological information, etc. Ichnological information has become valuable, yet some cases controversial, proxy, being most understudied. This paper gathers existing ichnological regarding frequent —from those analyses are detailed (e.g. pelagites/hemipelagites turbidites), for lacking or imprecise (hyperpycnites contourites). review palaeoenvironmental (i.e., ecological depositional) conditions associated with processes, influence these changes on tracemaker community, properties. A characterization trace fossil assemblages, ichnofabrics ichnofacies presented. Special attention paid variations features, approached through models outcrop/core scale. Similarities differences underlined facilitate differentiation. Pelagic/hemipelagic sediments completely bioturbated, showing biodeformational structures fossils, characterized by composite ichnofabrics. assemblage muddy pelagites hemipelagites mainly assigned Zoophycos ichnofacies, locally distal expression Cruziana ichnofacies. Turbidites colonized mostly from top, determining an uppermost part that entirely spotty layer; below it lies elite layer, deep-tier fossils. Turbidite beds pertain two different groups burrows, either “pre-depositional”, graphogliptids, “post-depositional” traces. deposits Nereites three ichnosubfacies according parts turbiditic systems conditions. There no major content hyperpycnite classical post-depositional turbidite, nor pelagic/hemipelagic sediments, except lower ichnodiversity Trace assemblages hyperpycnites while graphogliptids scarce absent. vary within largely related conditions, depositional setting, type contourite. Ichnodiversity abundance can high, especially mud-silty contourites. contourites similar (the tiering structure probably more pelagic/hemipelagic) upper (contourites continuously bioturbated). No single archetypal would characterize