A marine sediment concept defining how particles accumulate, are reworked, and change after burial on the seafloor. It governs depositional processes, physical properties, and post-depositional reactions measured through cores and laboratory analyses. It does not uniquely identify sources or processes without supporting stratigraphic, mineralogical, and geochemical evidence. It materially affects habitat, slope stability, and climate records by controlling the properties and composition of seabed deposits. The concept is generally stable, though analytical resolution and property measurement methods improve over time.

Principle

Local geochemical and biological conditions drive in-situ nucleation and growth of new mineral phases; authigenesis reflects reaction pathways controlled by pore-water chemistry, redox state, and available substrates.

Demonstration

Manganese and iron oxyhydroxide coatings and nodules precipitating on abyssal plains, glauconite forming within continental-shelf sands, and pyrite grains forming in reducing organic-rich sediments are examples of authigenic materials.

Misapplication

Describing all fine-grained seabed material as authigenic when the material was delivered from land or reworked elsewhere; equating authigenic minerals with primary detrital grains.

Consequence

Recognition of authigenic sediment reveals past and present pore-water chemistry, redox dynamics, and rates of early diagenesis; it informs interpretations of sedimentary sources and local geochemical cycles.

Reversal

Detrital or allochthonous sediment that originates and is transported from continental sources without significant in-place mineral formation.

Boundary

Applies to minerals and particles formed inside or on the sediment column after deposition; it excludes terrigenous clastic grains deposited intact and biogenic hardparts produced remotely and merely accumulated without chemical alteration.

Semantic Tension

Overlaps with diagenetic mineral formation and secondary mineralization; tension arises when distinguishing authigenic growth from early diagenetic alteration of transported grains.

Synthesis

Authigenic sediment is the suite of minerals and particles that reflect pore-water-driven, in-place chemical and biological processes on or within seafloor deposits, serving as a direct archive of local geochemical conditions distinct from transported detritus.