Presentation on theme: "Foraminifera Marcelle BouDagher-Fadel. What are Foraminifera: with characteristic net-like pseudopodia called reticulopodia organic or shell-like, agglutinated."— Presentation transcript:
Foraminifera Marcelle BouDagher-Fadel
What are Foraminifera: with characteristic net-like pseudopodia called reticulopodia organic or shell-like, agglutinated or secreted outer protective layer, called a test single-celled organisms (protists) Such organisms are classified in the Superkingdom of Protists or Protista with a complex cell (Eukaryotes), and genetic material within a cell nucleus. Cytoplasm is extruded as pseudopods through the aperture and any perforations in the test
Foraminifera are placed in the Cercozoa. Cercozoans are amoebae with filose pseudopodia, often living within hard test
Most foraminifera grow an elaborate, solid calcite skeleton made of a series of chambers. The complexity of their shell structures and their evolution in time the basis of their geological usefulness as fossils. Most foraminiferal tests are sand-sized (>61 mm in diameter)
Both living and fossil foraminifera inhabited the oceans. They are extremely abundant in most marine sediments in many different environments, from live in marine to brackish habitats near shore to the deep sea, and from near surface to the ocean floor Some foraminifera live in oligotrophic reef associated with algae.
Composition of fossil foraminifera tests varies from calcareous secreted from calcium carbonate. agglutinated (organic compounds, sand grains and other particles cemented together, or crystalline calcite)
The test is commonly divided into chambers which are added during growth The size of the test is associated with amount of the cytoplasm. Feeding adds to the bulk of the cytoplasm, therefore, the test has to enlarge. Foraminifera have developed several strategies for test enlargement during ontogeny contained growth unilocular test The test is thought to reduce biological, physical and chemical stress continuous growth Bilocular test simple septate growth multilocular complex septate growth Complex multiocular test These growth patterns result in a very diverse variety of test morphologies
the simplest forms are open tubes or hollow spheres Both living and fossil foraminifera come in a variety of shapes and sizes Spirillina Planispiral, evolute, undivided tube Lagena Undivided chamber reticulation
a: aperture; ad: adapertural depression; li: lip; tp: toothplate with its serrated margin. Loxostomina. A-B: Globoturborotalites Carpenteria cancellation perture terminal Secondary aperture Main aperture aperture
What are fossil foraminifera? Fossils can be microscopic or a few centimeters long They have inhabited the oceans for more than 500 million years and found fossilised in most type of sedimentary rocks. Most foraminifers construct tests (shells) covering the cell body. Fossil foraminifera are the remains of their tests (shells). Fully grown individuals range in size from about 100 micrometers to almost 20 centimeters long.
because there can be thousands of specimens in a small sediment sample. relatively small size of tests (shells) makes foraminifera For, biostratigraphic, palaeo/environmental, palaeoceanographical and palaeoclimatological reconstruction or petroleum exploration applications much more useful than larger fossils
The study of the sequence of sedimentary rock strata is the main source for scientific knowledge about the Earths history, including biostratigraphy, paleogeography, paleoclimatology and the history of life
Orders of foraminifera (underlined include larger foraminifera (see BouDagher-Fadel, 2008). In red includes planktonic foraminifera) ALLOGROMIDA: organic wall, usually 1 chamber; Cambrian-Recent ASTRORHIZIDA: agglutinated, organic cement, usually 1 chamber or branching tube; Cambrian- Recent LITUOLIDA: agglutinated, organic cement, many chambers, usually planispiral spiral; Cambrian- Recent TROCHAMMINIDA: agglutinated; organic cement, many chambers, usually trochospiral; Cambrian- TEXTULARIIDA: agglutinated, low Mg-calcite cement; Cambrian-Recent FUSULINIDA: microgranular calcite; many complex chambers; Silurian-Permian MILIOLIDA: high Mg calcite, imperforate, many chambers (porcellaneous, no pores); miliolid chamber arrangment; Carboniferous-Recent CARTERINIDA: low Mg calcite, hyaline, pores or no pores; spicules, plani- or trochospiral; Tertiary- Recent (?) SPIRILLINIDA: low Mg calcite; hyaline; single crystal; spiral; Jurassic-Recent LAGENIDA: low Mg calcite, hyaline; pores, 1 or many chambers, uniserial or planispiral; monolamellar; Carboniferous-Recent BULIMINIDA: low Mg calcite; hyaline; pores; many chambers; bilamellar; toothplate; Triassic?-Recent ROTALIIDA: low Mg calcite; hyaline; pores; many chambers; bilamellar; trocho- or planispiral, annular, irregular; Triassic-Recent GLOBIGERINIDA: low Mg calcite (aragonite in few extinct forms); pores; many chambers; bilamellar; radial crystals (PLANKTON); Jurassic-Recent INVOLUTINIDA: aragonite; 2 chambers - 2nd tube ROBERTINIDA: aragonite; pores; many chambers; trochospiral; Triassic-Recent SILICOLOCULINIDA:opaline silica, no pores; chamber arrangements as in miliolids; Miocene-Recent Genetic evidence suggests strongly that Allogromida (naked) and Astrorhizida (agglutinated) are one order.
Life strategy Float in the surface of the open ocean and sea water column Wide distribution Rapid evolution + short stratigraphic range = excellent index fossil Benthic foraminifera Live attached or free At all depth marine, brackish and freshwater habitats sea-floor Small Larger Planktonic foraminifera
Benthic foraminifera are bottom dwelling forms that can be either sessile or vagile. Benthic foraminifera Vagile (mobile) foraminifera are free to move along the sea floor and/or in its substrate Cassidulina Sessile foraminifera are permanently attached or fixed (not free-moving) Ammobacculites Miniacina
Benthic foraminifera Small benthic foraminiferaLarger benthic foraminifera include two major groups of foraminifera occur abundantly in the shelf regions of most tropical and subtropical shallow marine, especially in carbonate-rich, environments live, attached or free, at all depths, in most marine environments, as well as in brackish, marginal marine environment with low alkanity. with complicated internal structures with simple internal structures
Benthic foraminifera are an important component of the deep-sea biomass in the present oceans, adapted to its cold, dark, and extremely oligotrophic environments. Larger benthic foraminifera are important shallow marine rock builders Faunas are highly diverse, and many species have a cosmopolitan distribution. In addition to their interest as indicator species living in the largest habitat on earth, their tests have been used extensively in isotope and trace element analysis aimed at reconstruction of past environments.
Larger Foraminifera with test sizes from 2mm up to 13cm are characteristic organisms inhabiting shallow water subtropical and tropical environments today.
Two main factors acting as single gradients regulate the distribution of larger foraminifera within coral reef complexes. Larger foraminifera prefer clear, nutrition depleted water as can be found in the surroundings of coral reefs. All house symbiotic microalgae and are thus restricted to the photic zone (-130m), getting independence from food resources outside the cell. House symbiotic algae
Allogromia has a proteinaceous test with a single chamber. The oldest fossil foraminifera, from the Cambrian, are simple agglutinated tubes. Cambrian
Fusulina rice-grain shaped tests and evolved into numerous widespread species during the Permian but large forms went extinct at the end of that period when a worldwide mass extinction also eliminated most other reef dwelling organisms.
BouDagher-Fadel, M.K., Evolution and Geological Significance of Larger Benthic Foraminifera, Developments in Palaeontology and Stratigraphy, 21, Elsevier, Amsterdam, pp 544.Evolution and Geological Significance of Larger Benthic Foraminifera Haynes, J.R., Foraminifera. MacMillan, London, pp 433.