Biostratigraphy is the science of dating rocks by using the fossils contained within them. Usually the aim is correlation. That is, demonstrating that a particular horizon in one geological section represents the same period of time as another horizon at some other section. The fossils are useful because sediments of the same age can look completely different because of local variations in the sedimentary environment. For example, one section might have been made up of clays and marls while another has more chalky limestones, but if the fossil species recorded are similar, the two sediments are likely to have been laid down at the same time. FOSSIL is a standard for allowing serial communication for telecommunications programs under DOS. FOSSIL is an acronym for Fido Opus Seadog Standard Interface Layer. ... Sediment is any particulate matter that can be transported by fluid flow and which eventually is deposited as a layer of solid particles on the bed or bottom of a body of water or other liquid. ... The Gay Head cliffs in Marthas Vineyard are made almost entirely of clay. ... Marls are calcium carbonate or lime rich muds or mudstones which contain variable amounts of clays and calcite or aragonite. ... The Needles,situated on the Isle Of Wight, are part of the extensive Southern England Chalk Formation. ... Limey shale overlaid by limestone. ...

Ammonites, graptolites and trilobites are index fossils that are widely used in biostratigraphy. Microfossils such as acritarchs, chitinozoans, conodonts dinoflagellate cysts, pollen, spores and foraminiferans are also frequently used. Different fossils work well for sediments of different ages; trilobites, for example, are particularly useful for sediments of Cambrian age. To work well, the fossils used must be widespread geographically, so that they can occur in many different places. They must also be short lived as a species, so that the period of time during which they could be incorporated in the sediment is relatively narrow. The longer lived the species, the less accurate the correlation, and so fossils that evolve rapidly, such as ammonites, are favoured over forms that evolve much more slowly, like nautiloids. For other uses, see Ammonite (disambiguation). ... Graptolites (Graptolithina) are fossil colonial animals known chiefly from the Upper Cambrian through the Mississippian (Lower Carboniferous). ... Orders Agnostida Nectaspida Redlichiida Corynexochida Lichida Phacopida Subclass: Librostoma Proetida Asaphida Harpetida Ptychopariida For the robot vacuum cleaner, see Electrolux Trilobite. ... Index fossils (or zone fossils) are fossils used to define and identify geologic periods (or faunal stages). ... Micropaleontology, the study of microfossils, is a branch of paleontology. ... Acritarchs are small organic structures found as fossils. ... Chitinozoa (English singular: chitinozoan, plural: chitinozoans) are a group of flask-shaped marine microfossils (50-2000 micrometres) which appear dark or almost opaque when viewed using a light microscope. ... Conodonts are extinct worm-like forms with distinctive conical or multi-denticulate teeth made of apatite (calcium phosphate). ... Classes Dinophyceae Noctiluciphyceae Syndiniophyceae The dinoflagellates are a large group of flagellate protists. ... SEM image of pollen grains from a variety of common plants: sunflower (Helianthus annuus), morning glory (Ipomoea purpurea), prairie hollyhock (Sidalcea malviflora), oriental lily (Lilium auratum), evening primrose (Oenothera fruticosa), and castor bean (Ricinus communis). ... The term spore has several different meanings in biology. ... Orders Allogromiida Carterinida Fusulinida - extinct Globigerinida Involutinida - extinct Lagenida Miliolida Robertinida Rotaliida Silicoloculinida Spirillinida Textulariida incertae sedis    Xenophyophorea    Reticulomyxa The Foraminifera, or forams for short, are a large group of amoeboid protists with reticulating pseudopods, fine strands that branch and merge to form a dynamic net. ... Orders Agnostida Nectaspida Redlichiida Corynexochida Lichida Phacopida Subclass: Librostoma Proetida Asaphida Harpetida Ptychopariida For the robot vacuum cleaner, see Electrolux Trilobite. ... The Cambrian is a major division of the geologic timescale that begins about 542 ± 1. ... Orders Palcephalopoda †Plectronocerida †Ellesmerocerida †Actinocerida †Pseudorthocerida †Endocerida †Tarphycerida †Oncocerida †Discosorida Nautilida Neocephalopoda (in part) †Orthocerida †Ascocerida †Bactritida Nautiloids are a group of marine mollusks in the subclass Nautiloidea, which all possess an external shell, the best-known example being the modern nautiluses. ...

Fossils as a Basis for stratigraphic subdivision

Concept of Stage: It is a major subdivision of strata, each systematically following the other each bearing a unique assemblage of fossils. Therefore, stages can be defined as a group of strata containing the same major fossil assemblages. D'Orbigny, a French palaeontologist, is credited for the invention of this concept. He named these stages after geographic localities with particularly good section of rock that bear the characteristic fossils on which the stages are based.

Concept of Zone: Albert Oppel, in 1856, introduced the concept of zone (also known as biozones or Oppel zone). A zone is a strata characterised by the overlapping range of fossils. They represent the time between the appearance of species chosen at the base of the zone and the appearance of other species chosen at the base of the next succeeding zone. Oppel's zones are named after a particular distinctive fossil species, called an index fossil. Index fossils are one of the species from the assemblage of species that characterise the zone.

Index fossils: To be useful in correlation work, index fossils should be:

- Independent of their environment

- Geographically widespread (Provincialism/isolation of species should be avoided as much as possible)

- Fast evolving

- Abundant (Easy to find in the rock record)

- Easy to preserve (Easier in low-energy, non-oxidized environment)

- Easy to identify (Not too small for instance)

The Zone is the fundamental biostratigraphic unit. Its thickness range from a few to hundred's of metres, and its extant range from local to worldwide. Biostratigraphic units are divided into six principal kinds of biozones:

Taxon range biozone: Represent the known stratigraphic and geographic range of occurrence of a single taxon.

Concurrent range biozone: Include the concurrent, coincident, or overlapping part of the range of two specified taxa.

Interval biozone: The stata between two specific biostratigraphic surfaces. It can be based of lowest or highest occurrences.

Lineage biozone: Strata containing species representing a specific segment of an evolutionary lineage.

Assemblage biozones: Strata that contain a unique association of three or more taxa.

Abundance biozone: Strata in which the abundance of a particular taxon or group of taxa is significantly greater than in the adjacent part of the section.

See also

Lithostratigraphy Lithostratigraphy is the geological science associated with the study of stratum or rock layers. ...