MICROFOSSILS FORAMINIFERS Technique

Foraminifers are protists that are similar to amoeboid organisms in cell structure. Foraminifers differ in having granular rhizopodia and elongate filopodia that emerge from the cell body. Foraminifers are covered with an organic test that varies from a simple single chamber with an aperture, to a complex, multichambered, perforate, calcitic wall, to an agglomeration of mineral grains embedded in the organic test. Foraminifers are divided into two primary groups based on their mode of life, planktic (marine floaters), and benthic (sea floor dwellers). Benthic foraminiferal morphologies are diverse, from simple single-chambered to multi-chambered, complex forms composed of calcite or mineral grains. The benthic foraminifers utilize rhizopodia extended through single or multiple apertures and test perforations for gathering prey and locomotion. Benthic foraminifers display a variety of life cycles that include sexual and asexual phases and produce megalospheric and microspheric generations. The length of an individual's life can range from a few weeks to up to 5 years. Since an individual's morality is dependent on when it reproduces, there are many factors controlling its life span. Application to Earth Science Research Benthic foraminifers occupy a wide range of marine habitats and occur at all latitudes, so they are useful as environmental indicators. Particular species and assemblages can be used to identify paleoenvironments ranging from brackish estuaries to the deep sea. Application of modern benthic foraminiferal distribution data to deep-sea core data has been utilized to identify paleoceanographic changes in intermediate and deep-water circulation. Using water depth ranges of benthic foraminifers as paleobathymetric indicators help determine past sea level changes in coastal regions. Changes in benthic foraminiferal assemblages and test morphologies are becoming increasingly useful for assessing environmental quality (changes in water salinity, temperature, dissolved oxygen, nutrient input, heavy metals and other toxic materials) in coastal regions, and reconstructing historical changes in near shore ecosystems. Geochemical analyses of benthic foraminiferal tests provide information on water salinity and temperature. Benthic foraminifers can be used as biostratigraphic indicators. Although not as useful as planktonic foraminifers due to their usual long ranges, benthic foraminifers provide regional utility for biostratigraphic zonation (e.g., Gulf of Mexico, New Zealand). Larger benthic foraminifers are very useful biostratigraphically in Late Paleozoic and Early Mesozoic stratigraphy. Links South Florida Ecosystem Program South Florida Ecosystems: Changes Through Time Hydrogeology of the Surficial Aquifer System in Southwest Florida Ecosystem History of Biscayne Bay and the Southeast Florida Coast Ecosystem History of Florida Bay and the Southwest Florida Coast Related Internet Resources Introduction to the Foraminifera (Museum of Paleontology, University of California at Berkeley)

| Capabilities | | Paleontological Analysis  |

URL http://geology.cr.usgs.gov/capabilities/paleoanal/microfos/foram/tech.html