In geology, petrifaction or petrification is the process by which organic material becomes fossilized through the replacement of the original material and filling the original pore space with minerals. The petrified wood represents this process, but all organisms, from bacteria to vertebrates, can become petrified (though harder, more durable materials such as bones, beaks and shells survive better than the softer remnants such as muscle tissue, feathers, or skin). Petrifaction takes place through a combination of two similar processes: permineralization and replacement. These processes make replicas of similar original specimens to microscopic levels.
Video Petrifaction
Proses
Permineralization
One of the processes involved in petrification is permineralization. Fossils created through this process tend to contain large amounts of original material from specimens. This process occurs when groundwater containing dissolved minerals (most commonly quartz, calcite, pyrite, siderite (iron carbonate), and apatite (calcium phosphate)), fills the pores and cavities of specimens, especially bone, skin or wood. The pores of the organism's tissues are filled when these minerals precipitate out of the water. Two common types of permineralization are silicification and pyritisation.
Silicify
Silicification is the process by which organic matter becomes saturated with silica. The common source of silica is volcanic material. Research has shown that in this process, most of the original organic matter is destroyed. Silicification is most common in two environments - both specimens buried in delta sediments and floodplains or organisms that are buried in volcanic ash. Water must be present for silicification occurring because it reduces the amount of oxygen present and thereby reduces organism damage by fungi, maintains the shape of the organism, and allows for the transport and deposition of silica. The process begins when the specimen is absorbed with an aqueous silica solution. The cell wall of the specimen is progressively diluted and the silica is deposited into the empty space. In wood samples, during the process, cellulose and lignin, two wood components, are degraded and replaced with silica. The specimen is transformed into stone (a process called lithification) when water is lost. For silicification to occur, geothermal conditions should include neutral pH to slightly acid and temperature and pressure similar to that of shallow sedimentary environments. Under ideal natural conditions, silicification can occur at levels close to that seen in artificial freezing.
Pyritization
Pyritization is a process similar to silicification, but involves precipitation of iron and sulfur in the pores and cavities of an organism. Pyritization can produce both preserved solid and soft tissue fossils. In marine environments, pyritization occurs when organisms are buried in sediments containing high concentrations of iron sulfide. The organism releases sulphides, which react with dissolved iron in the surrounding water, when they rot. The reaction between iron and sulfide forms pyrite (FeS 2 ). The carbonate shell material of this organism is then replaced by pyrite due to higher pyrite concentrations and lower carbonate concentrations around the water. Pyritization occurs at a lower level in plants in clay environments.
Substitution
Replacement, a second process involved in petrification, occurs when water containing dissolved minerals dissolves the original solid material of an organism, which is subsequently replaced by minerals. This can take very slowly, replicating the microscopic structure of the organism. The slower the process, the better the microscopic structure. Common minerals involved in replacement are calcite, silica, pyrite, and hematite. It is very rare to find organisms preserved by replacement alone (as opposed to in combination with permineralization), but these fossils provide significant significance for paleontologists because these fossils tend to be very detailed.
Maps Petrifaction
Usage
Not only fossils are produced through the petrifaction process used for paleontological studies, but fossils have also been used as decorative and informative pieces. The petrified wood is used in several ways. Fossilized wooden sheets can be made into tabletops, or the slab itself is sometimes displayed in a decorative style. Also, larger pieces of wood have been carved into the sink and basin. Other large pieces can also be made into chairs and benches. Petrified wood and other petrified organisms have also been used in jewelry, sculpture, watchmaking, ashtrays and fruit bowls, and landscape and garden decorations.
Architecture
Petrified wood has also been used in construction. The Petrified Wood Gas Station, located in Lamar, Colorado, was built in 1932 and consists of walls and floors constructed from petrified wood pieces. The structure built by W.G. Brown, has been converted into used office space and car dealerships. Glen Rose, Texas provides more examples of the use of wood fossils in architecture. Beginning in the 1920s, the farmers of Somervell County, Texas began uncovering petrified trees. Local artisans and masons then built more than 65 structures of this petrified wood, 45 of which still stood until June 2009. These structures include gas stations, flower beds, huts, restaurants, fountains, and water gates. Glen Rose, Texas is also noted for Dinosaur Valley State Park and Glen Rose Formation, where traces of dinosaur fossils from the Cretaceous period can be seen. Another example of using petrified wood in construction is the Agate House Pueblo in Petrified Forest National Park in Arizona. Built by the Pueblo ancestor some 990 years ago, the eight-room building was built almost entirely of petrified wood and is believed to have served as a family home or ceremonial center.
Artificial Petrification
Recently, at the Pacific Northwest National Laboratory (PNNL), wood samples have been successfully artificially frozen, unlike what is naturally obtained, infiltrated in acidic solutions, spread internally with titanium and carbon and fired in a high-temperature oven ( about 1400 Ã, Â ° C) in an inert atmosphere to produce a manmade ceramic matrix composite of titanium carbide and silicon carbide still showing the initial structure of wood. Future uses will see this petrified artificial wooden ceramic material eventually replacing a metal-based superalloy (coated with ultrahard ceramics) in the tool industry. Other vegetable materials can be treated in the same process and produce abrasive powder. Scientists have been trying to petrify artificial organisms as early as the 18th century, when Girolamo Segato claims to have a "human remains" that is feared. His method was lost, but most of his "pieces" were on display at the Museum of the Department of Anatomy in Florence, Italy. More recent efforts have been successful and documented, but should be regarded as semi petrification or incomplete petrification or at least some new types of wood composites as a fixed wood material to some extent; the wood constituent (cellulose, lignin, lignan, oleoresin, etc.) has not been replaced by silicates, but has been infiltrated by a specially formulated acid solution of the gel aluminosilicate salt in contact with the wood material and making the silicate matrix in the wood after it has been allowed to react slowly over a period of time certain in solution or heat cured for faster results. Hamilton Hicks of Greenwich, Connecticut, patented a "recipe" for the manufacture of fast-made stones under US patent 4,612,050. The Hicks recipe consists of highly mineralized water and a solution of sodium silicate combined with a dilute acid with a pH of 4.0-5.5. Wood samples are then pierced with this mineral solution through repeated immersion and application of the solution. The wood is treated in this way according to the claim in the patent that is not combustible and obtains a petrified wood feature. Some uses of this product as suggested by Hicks include use by horse breeders who want a fireproof cage made of non-toxic material that will also be resistant to chewing wood by horses.
See also
- Concretion
- Petrification in mythology and fiction
- Petrified well
- Rhynie chert
- Substitution pseudomorph
- Taphonomy
References
Source of the article : Wikipedia
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