biogenous

Biogenous is an adjective used in geology and marine science to describe materials derived from living organisms or their behaviors. Biogenous materials are produced by biological processes and may consist of whole organisms, their skeletal or shell parts, or organic matter preserved after death. This distinguishes biogenous material from lithogenous (terrigenous) material derived from mechanical weathering of rocks and hydrogenous or precipitated minerals formed in situ.

Biogenous sediments are common in the world's oceans and are broadly categorized by the chemical composition of the constituent tests. Calcareous biogenous sediments consist of calcium carbonate from organisms such as foraminifera, coccolithophores, and pteropods. Siliceous biogenous sediments consist of silica from diatoms and radiolarians; the silica tests accumulate as diatomaceous earth or radiolarian ooze. In some contexts, biogenic material contributes to limestone, chalk, or chert when subjected to diagenesis.

Distribution and accumulation depend on productivity, dissolution, and depth. Calcareous ooze forms mainly above the carbonate compensation depth (CCD), where calcium carbonate remains stable; below the CCD, dissolution reduces calcareous sediment accumulation. Siliceous ooze tends to accumulate in regions of high surface productivity, often in nutrient-rich upwelling zones and polar waters, and may persist at greater depths. Over geological time, biogenic sediments can be buried and transformed into sedimentary rocks, with fossil shells preserving clues to past environments.

Biogenic materials are important in studies of the carbon cycle, paleoceanography, and paleoecology. They also have industrial significance, such as diatomaceous earth used as filtration medium and abrasive, and limestone formed from accumulated carbonate shells.