Biostratigraphy
The biostratigraphy and - graphy (from Greek βίοςbios = life; stratigraphy layers = customer ) is a sub-discipline of stratigraphy in geology. It deals with the structure and the relative chronological determination of rock units with the help of fossils.
- 2.1 Phylo - zone
- 2.2 Range Zone
- 2.3 Biohorizont
- 3.1 Marine Invertebrates
- 3.2 vertebrates
- 3.3 microfossils
- 3.4 Pollen and spores
History
After Nicolaus Steno had already recognized in the 17th century that the spatial arrangement of rock layers over each other actually corresponds to a temporal sequence of rock formation in succession (see: Stratigraphic principle), and Georges de Cuvier spread the knowledge in the late 18th century, that it is in course of the Earth has come repeatedly to the extinction of biological species, William Smith used the principle of fossil succession around 1800 very successful in its geological mapping of England. Around 1810 coined Leopold von Buch for the particularly suitable for this purpose, the term fossil index fossil.
By 1830, Charles Lyell annexed the Tertiary in southern France, Gérard Paul Deshayes - the rock strata in the Paris basin and Heinrich Georg Bronn the Italian tertiary means of fossils. In the subdivision of the former primary system in 1838 lithologically quite different types by comparing under - and overlying fossil content, spatially widely separated layers of rock have been interpreted as a time- equivalent deposits. The 1852 was introduced as of Alcide d' Orbigny Étage precursor of the zone concept still known as the Biozone biostratigraphic basic unit of structure by means of fossils. In addition to the fossil groups originally used to structure ( Ortho chronology ) were gradually more by working stratigraphers paleontological fossil groups (Para chronology ) harnessed. In the modern biostratigraphy ( evolutionary lines ) are sought since the second half of the 20th century by a series outlines virtually completely trackable, phylogenetic lines. A new development is the use of all leveled Picked Up, a taxon assignable fossil individuals by computer- assisted methods.
The principle of fossil succession
Among fossil sequence is defined as the occurrence of fossils in a very specific, unchanging and recognizable vertical arrangement within a rock sequence. In connection with animal and plant remains one speaks also of faunas or Flore result.
The principle of fossil succession (also called " Leitfossilprinzip " called ) states that a certain fossils Community shall be replaced over time in a given area from another socialization. Once a fossil once disappears from a rock sequence, it returns to the sequence never go back. This principle distinguishes the biostratigraphy of the lithostratigraphy, because, unlike fossils, certain rocks can occur during the rock sequence over and over again in almost identical form. It offers sustained not only the correlation of certain layers of rock over long distances, even if their original depositional relationships were disrupted and displaced by subsequent tectonic events, but also the relative dating of the layers to one another and predicting which layers are to be expected at what point in the subsurface..
Long before the publication of Charles Darwin's theory of evolution thus laid the observation of fossil succession in the rocks the thought suggests that the evolution of organisms, not is cyclical, like the cycle of rocks, but progresses in a directed, basically irreversible process, because each section of Earth's history can be defined by a unique, never before seen before and never recurring socialization of fossil organisms.
Procedures and concepts
Basic unit of biostratigraphy is the biozone. The term zone was introduced by Albert Oppel as a refinement and conceptual clarification of Étage of Alcide Dessalines d' Orbigny. The Biozone referred to as a chronological unit based on the life of a biological species as a stratigraphic term period and the newly formed rocks within this period. In the past, higher taxonomic units for the breakdown of their phylogenetic length of life were used according to type. Thus, based on the length of life of a class period was referred to as a step.
The modern biostratigraphy rarely used higher taxonomic categories than those of the biological kind, the equivalent to that international recommendations hold no biostratigraphic categories above the zone stock. Recently, therefore - unlike the traditional use - even those based on genera or families units be designated as zones.
It contains a number of strictly separate concepts application of a single taxon or combination of several taxa are defined by considering the timing of Artwerdung and extinction (or the appearance or disappearance in the rock sequence ). A differentiated, concrete unity is becoming at least from the name of the taxon is founded (or founded taxa ) and the term " zone " or " Biozone " together. Thus, the G. kugleri zone designated in the border area Paleogene / Neogene the kugleri justified by the foraminiferal species Globorotalia ( ranges ) zone.
Phylo - zone
The phylogeny zone covers the period of existence of a defined type within an evolutionary development series. It begins with the appearance of the eponymous species and ends with the appearance of successor taxon. Such a structure requires a precise knowledge of the development series. Important to the understanding of such a development series, knowledge, why the individual elements can be observed in this density at all and what are the internal and / or external " drives" the steady shape change. By means of this concept is possible the stable differentiation of zones of extremely short duration. An example of this is the division of the Late Devonian through platform conodonts of the genus Palmatolepis.
Range Zone
A coverage zone represents the portion of the time - stratigraphic and geographic occurrence of one or more taxa. Here we distinguish between:
- Taxon - range zone
- Overlap zone
- Interval Zone
- Socialization zone
- Frequency zone
The concept of the taxon - range zone corresponds largely to that of the Leitfossils.
Biohorizont
A Biohorizont is a biostratigraphically established area in a body of rock. Each point on the surface represents the time of a perceptible change or paleontological events ( environmental event). Frequently there is a close relationship between sedimentologischem and palaeontological findings.
Fossil groups
The fossils, which serve as stratigraphic markers are called index fossils. Good index fossils are as frequent, faziesunabhängige, good fossil preservation enabled and temporally short-lived taxa.
Marine Invertebrates
Classic biostratigraphy is operated with marine invertebrates. Marine sediments are much more common than terrestrial sediments in the rock tradition and many marine organisms have hard parts that have a high potential for fossil preservation. Important Makroleitfossilien Palaeozoic brachiopods and are goniatites, in Mesozoic ammonites and shells.
Vertebrates
Vertebrates in the fossil record are much rarer than invertebrates and therefore more likely not typical index fossils. Wirbeltierbiostratigraphie is mainly applied to terrestrial sediments. So therapsids are the most important index fossils in the Permian of the Karoo Basin. Rodent teeth are the most important index fossils in terrestrial sediments of the Cenozoic (see also → ELMMZ Neogene ).
Microfossils
The advantage of Mikrobiostratigraphie is that microfossils usually occur much more frequently and in larger quantities in sediments. In addition, some groups also occur in terrestrial sediments. Important index fossils in the Lower Paleozoic acritarchs are, in younger Paleozoic conodonts in the Mesozoic foraminifera and coccoliths. In terrestrial sediments are especially ostracods of importance.
Pollen and spores
Pollen and spores of terrestrial plants, so-called palynomorphs, also meet the requirements of good index fossils and are therefore suitable for biostratigraphy. They are widely drifted by the wind and therefore are also found in marine sediments.