Globigerina ooze is the most common type of calcareous sediment from planktonic origin found at the bottom of the ocean. Foraminifera are single-celled zooplankton organisms, whose tests (shells) comprise a large portion of the calcareous biogenic ooze (globigerina ooze) found in the sea bottom. Many types of organisms contribute to the deposition of sediment in the ocean floor, although globigerina ooze is the most abundant. Their calcium carbonate (CaCO3) shells make up very large deposits in the ocean floor. Some tests are well preserved that have provided a record of the Cambrian period. Globigerina ooze can be classified as containing 30% of CaCO3 and the sediments may range from fine calcareous sand to coarser grains.
Types of organic oozes
The organic constituents of sediment deposits found on the ocean floor are made of the remains of almost every marine organism that possesses a hard skeletal structure. Pelagic oozes often consist of the remains of just one type of marine organism, although the great majority always contain traces of other types of organic oozes, therefore, the sediment is named after the major constituent. Thus, there are coccolith, diatom, foraminifera (globigerina) pteropod and radiolarian oozes, of which foraminifera are the most abundant and large quantities of foraminifera (globigerina ooze) descend to the ocean bottoms every year. Oozes are also classified based on their mineral constituent. For example, there are calcareous oozes or siliceous oozes.
Foraminifera
Foraminifera are single-celled heterotrophic zooplankton found in marine and freshwater habitats. Foraminifera are mostly benthic organisms, although approximately 40 species are planktonic species, whose calcareous shells make up globigerina ooze. Foraminifera feed on diatoms, bacteria and microscopic plankton. They use pseudopodia (false foot) to capture their food and for motility. Some foraminifera live in a mutual relationship with species of algae. Foraminifera have calcium carbonate shells (tests), which have helped scientists produce a high-quality foraminifera fossil record dating back to the Jurassic period.
Pelagic sediments
Pelagic sediments cover approximately 74% of the ocean floor. Calcareous oozes, including those from pteropods and globigerina oozes comprise 48%, being more abundant those of globigerina ooze. Sediment deposits from red clay account for 38% of the total and Siliceous oozes cover approximately 14% of the total area. Calcareous deposits abound in the Atlantic and Indian Oceans, while red clay predominates in the Pacific Ocean. The Pacific Ocean contains a large percentage of all types of pelagic sediments, although siliceous ooze and red clay are more abundant. While radiolarian ooze and red clay are characteristic of depths greater than 4 km (2.5 miles), globigerina ooze are restricted to smaller depths.
Calcite compensation depth
Globigerina ooze is made of calcium calcite. Such sediments are not able to sink below the calcite compensation depth (CCD), which lies at an average depth of 4.5 km (2.8 miles) below sea level. Below the CCD, calcite dissolves in the ocean water. Globigerina ooze is usually found above the CCD. At greater depths, tiny shells of CaCO3 tend to dissolve. The value of CCD is determined by the temperature, pressure and the amount of CO2 in sea water. Below the CCD, the CaCO2 of the planktonic tests is soluble in water due principally to high CO2 concentrations and increased ocean pressures. The CCD in the Pacific Ocean is 4.2-4-5 km (2.6-2.8 miles) deep, while in the Atlantic is 5 km (3 miles) and in the Indian Ocean the CCD is at an intermediate depth between that of the Atlantic and Pacific oceans.
The remains of foraminifera, falling to the bottom of the sea, comprise a large portion of the soft mud, typically found at depths not greater than 5 km (3 miles) known as globigerina ooze. Much of globigerina ooze is composed of minute calcite crystals, which result from the fragmentation of the foraminifera skeletons. Calcareous deposits derived from marina animals are most abundant than those stemming from marine plants. While many drifting marine organisms contribute to the deposition of sediments on the ocean floor, foraminifera organisms are the most important and sediment deposits containing significant amounts of them are known as globigerina oozes.
