Biostratinomy
The biostratinomy (also biostratonomy ) is the study of the regulation and arrangement of the fossils in the rock. It encompasses all processes on the individual from dying to their final embedding in the sediment.
The doctrine was founded by Johannes Weigelt , who published about it as early as 1919 and included fossils in the copper shale and lignite of the Geiseltal under these aspects.
introduction
Fossils can only arise if bodies, body parts or traces of the organisms are not destroyed. This is often the case with embedding - but not when the organism remains on the surface of the earth. Dead bodies are therefore only preserved in the long term if they are protected from destruction by scavengers and physical forces by being embedded in sediments such as sand , mud or ice .
A distinction must be made as to whether the embedding takes place autochthonously , i.e. on the spot, or allochthonously , after a more or less long post-mortem transport to the fossilization site . Autochthonously stored fossils lie safe in their habitat, about which the analysis of the surrounding rock, its position in the layer sequence, etc. can provide information. This is particularly important because for the correct paleontological classification, in addition to the type of death, the way of decomposition and embedding, the knowledge of the animal's way of life and its relationship to its environment is important.
Conservation conditions for water dwellers or fixed animals are usually more favorable, which leads to a more frequent relative occurrence of such autochthonous fossils.
Allochthonous fossils often show severe distortions, which were caused by forces acting during transport such as currents, gravity, buoyancy from decomposition gases or browsing by scavengers. However, they can be rare indications of inhabitants of habitats with unfavorable sedimentation conditions, such as mountain and altitude locations with strong erosion and rubble formation or primeval forest areas on solid rock. So those fossils in which the carcasses were not embedded in the place where the organism died. For example, there are hardly any fossils in a mountain range , because the mountain range is subject to erosion and usually disappears completely after many millions of years. If you look for the creatures that inhabit mountains, you can sometimes find them in former rivers that transported water from the mountains. These fossils then show a picture of severe devastation of the organism, which was carried over scree slopes and raging torrents down into the lowlands, only to be embedded in river mud there.
Often the transport is constrained by long-standing mechanisms such as B. causes strong river currents or torrents in mountain regions, which over time, many carcasses can accumulate in a narrowly defined area. Such occurrences are known as thanatocoenoses (grave communities). They are of extraordinary scientific value because they house numerous different species from a common time, so they can be viewed like a group photograph . You then get an overview of the species that lived together.
Important biostratinomic considerations
The arrangement of the bones in the rock. The bones are not always preserved in the order in which they stood in relation to one another in the skeleton - compact finds are rarely found. Especially in allochthonous thanatocoenoses, segregation occurs before and during embedding , whereby corpse components can be sorted and relocated according to shape , weight and hardness . Numerous factors play a role in this cargo segregation , among which the transport conditions and the amount of animals eaten on land as well as the different floating ability, the age or the flow conditions of water dwellers are important. Diagenesis then proceeds in different ways with the different parts. Sites that have been uncovered, changed and re-embedded after temporary conservation are particularly confusing. Often found sites are to be found in which certain bones were selectively embedded in a regulated manner: ribs or teeth in large numbers.
One-step selection led to the targeted accumulation of certain shapes and weights - often in a regulated arrangement that allows conclusions to be drawn about the embedding conditions. Mussel and snail shells are aligned by the water flow according to dynamic principles. Then - depending on the axis of rotation - one speaks of tilting or steering the material into the site.
In Alaska, around the turn of the century, mammoth hairs from ice mummies were so common in rivers that they interfered with gold prospecting. Where they accumulate, they could be embedded again and finally fossilize. Often, fossil collectors discover unmanageable collections of bones that have to be evaluated, compared and sorted in a "mammoth work". As with the excavation of prehistoric human settlements, special care must be taken when recovering fossil deposits so that as little information as possible is lost through inattention.
Methods of biostratinomy
The methods of biostratinomy are closely connected to those of fossilization and are widely taken from the related disciplines: biochemistry , biophysics , chemistry , geology , etc. A separate method is causal analysis.
Causal analysis
Causal analysis of the formation of a fossil. Here, all available information about the fossil, the environmental conditions at the time of his death, the type of rock , etc. are evaluated according to plausible criteria and brought into causal relationships. This creates a story of the fossil.
Counting the abundance of fossils
However, numerous or well-preserved evidence in the rock only allows limited conclusions to be drawn about the richness of individuals or species of the organism group concerned . From an abundant population in which many individuals of a species are found, the conclusion cannot be drawn that the species in question was very rich in individuals in its time. Conversely, it can also be that common species are rarely or not at all fossilized.
The likelihood that the inhabitants of different habitats will be stored in fossil form varies with the environmental conditions to which the animal is exposed during its lifetime. This shows a major disadvantage of fossil science, which cannot be compensated for with morphological methods such as the description and comparison of building plans. Rare evidence of a morphological type may indicate relatively large and significant populations - even species that played a central role in later tribal history . (see also Missing Link )
It is also very likely that a large number of species that occurred locally or only existed briefly will never be found because the rock layers required for their detection are hidden in deep geological formations or have already been destroyed by exogenous forces. Some parts of former land or ocean floors are also hidden deep inside the earth, where they are slowly heated and melted, but at least changed lithologically. Fossils that are there are lost forever and there is nothing that can bring them back. Statistical projections, in which numerous plausible considerations have to be included, can only provide information about how big the respective gaps in tradition may be, which we will not close.
Logical inference
Although the fossil photographer is very unfocused, prefers light motifs and neither cares about their meaning nor values the completeness of his photo albums, it is possible to build bridges by drawing conclusions. Proof of this would be possible through inferences based on available information about their ancestors or descendants , which happened to be photographed again. Perhaps there have been entire groups of organisms in the history of the earth, of which we never gain knowledge, because no fossil evidence can be known. However, we can still say that these groups of organisms must have existed because they had ancestors and descendants, i.e. not extinct in the absolute sense .
Individual evidence
- ^ Wagenbreth, History of Geology in Germany, Springer Spectrum 1999, p. 187