The ocean floor is made up of a combination of rock, sand, sediment and organic waste. Each of these is highly complex, made up of ever-increasing types. Sediment is one of these. Containing predominantly lithogenous, biogenous, cosmogenous and hydrogenous matter, the sediment is highly complex, with many different materials and sources. Oceanography examines the sediment of the ocean, determining the components and requirements for all sediments, silts and organisms formed in the sea bed.
Primarily, the term “biogenous” describes the source of the sediment. Translated, the “bio” portion of the name equates to organic matter. When an organism that produces “hard” components dies, these items remain and drop to the bottom of the ocean. Usually from free-floating organisms, components such as bones, teeth and shells are weathered through many means and eventually broken down, where they form a portion of the sediment.
Formed from Silica and Calcium Carbonate (calcite), this material is formed predominantly from diatoms (silica-secreting) and coccolithophores (calcite-secreting). When organisms who secrete silica or calcite accumulate, and proportions of these are high enough, they are classified as types of biogenous ooze: either siliceous ooze or calcareous ooze. This occurs when a specific component, either silica-secreting or calcite-secreting organisms, is greater than 30 percent.
These oozes can then go on to form rock or rock-like substances. Diatomaceous earth is formed when diatom-rich ooze hardens. Alternatively, chalk can be formed when coccolith-rich ooze hardens. These deposits are mostly found as pelagic deposits, and are highly affected by ocean productivity, dissolution with water and dilution with other substances. These rocks can be subducted underneath the floor, undergoing further geological changes, forming metamorphic rock.
Oozes of each type form in different places. Due to the high concentration of calcium carbonate from all organisms in the sea, concentration above 4,500 meters is so high that the production is greater than dissolution. This results in an accumulation at 4,500 meters, resembling “marine snow.” Below this level, the volume of life is lower, resulting in a lower concentration of calcite, meaning dissolution occurs. As the volume of silica-secreting organisms is lower in comparison, the ocean is under-saturated, meaning dissolution can occur anywhere.
Organisms which are measured, although seemingly far away, directly impact on our daily lives. Filters, chalk substances and petroleum are all formed from the breakdown of these deposits. In addition to the substances produced, these oozes in particular can tell a lot about the history of continents and the Earth. By knowing the environmental conditions required for a certain sediment to form, one can tell what conditions were like when each sediment type was produced. This is particularly useful when examining millions-of-years-old deposits!
Biogenous deposits are ever-present forms which provide useful information about the past (and the future) for scientists. Their huge impact on today’s super-commercial society cannot be underestimated, and further understanding of their systems and processes may, in fact, continue to increase the ability to utilize these forms of sediment.
