The Permineralization Is one of the most common types of fossils. This occurs when the pores of plant materials, bones and shells are impregnated by mineral matter from the soil, lakes or ocean. In some cases, wood fibers and cellulose dissolve and some minerals replace them.
Sometimes the mineral substance of the fossils dissolves completely and some other minerals replace them. The common minerals that form this type of fossils are calcite, iron and silica.
Horseshoe crab fossil.
Since the pores of organic tissues are filled with minerals, or organic matter is replaced with minerals, fossils are composed in the original form of the tissue or organism, but their composition will be different and will be heavier (Fossils Window to the past , SF).
Permineralized Fossils and Characteristics
Permineralized fossils, such as petrified wood, are often some of the most beautiful fossils. They are often filled with multicolored crystals.
Different colors can be traced to specific types of mineral impurities (red = iron, green = copper, yellow = sulfur, etc.).
Most fossilized dinosaur bones and wood are permineralized. Permineralized fossils are created when hollows and cavities in bone and wood, such as cells, are filled with minerals.
The most common mineral in permineralization is silica (SiO2) or quartz. Often, the original cell structure (pattern) is preserved. In the case of petrified wood, it is often possible to identify the genus of the tree.
The various colors observed, especially in petrified wood, are due to traces of other elements such as iron (Fe) and copper (Cu) (U.S. department of interior, S.F).
Figure 1: fossils of dinosaurs and wood.
In many cases, permineralization only preserves the mineral tissue in the body, such as bones, teeth and shells. In other cases, it fills a vacuum left in the sediment by an organism that has since decomposed.
This commonly occurs with fossilized leaves. In very rare cases, some or all of the soft tissues are preserved, allowing people to get an idea of a body that may have millions of years to learn more about how it worked (Conjecture Corporation, S.F.).
Fossils
When you think of a fossil, surely the first thing that comes to mind is a dinosaur bone or a petrified shell that can be found in the forest, but a fossil is much more.
Fossils are remains (complete or partial) of living beings that have lived in the past (thousands, millions of years) or traces of their activity that are generally conserved in sedimentary rocks (ROVIRA, 2016).
The term"fossil"is used for any trace of past life. Fossils are not only the remains of organisms, such as teeth, bones, shells and leaves (body fossils), but also the results of their activity, such as burrows and fossils and organic compounds that produce biochemical (chemical fossils) processes.
Occasionally, structures produced inorganic can be confused with traces of life, such as dendrites. These are called pseudofossils (The Virtual, S.F.).
When it comes to the formation of fossils, permineralization is the most common process for the preservation of the ancient plant and animal material. Common is a relative term when used with respect to fossils.
Although there are millions of fossils that have been discovered and millions more waiting to be discovered, fossilization is a rare occurrence. (Fossil Formation The Work of Ages, S.F.).
Permineralization process
In general, groundwater does not contain molecules of pure water. It is"hard", to a certain extent, which means that it contains some minerals.
The degree of hardness may vary. The different carboniferous minerals are found in the soil, and water dissolves them to saturation, at which time the water does not contain any additional mineral matter.
This process is reinforced by acidification of water. For example, rainwater when it is pure in the beginning collects carbon dioxide from the air and becomes a weak carbonic acid.
Organic matter in the soil, and other decomposing materials will also make the groundwater more acidic. This acidic water dissolves more minerals.
Organic tissues such as wood, bone and shell contain pores and spaces. The mineralized water fills the pores of the organic tissues and moves through the cellular spaces.
During this process the saturated water evaporates, and the excess of minerals is deposited in the cells and tissues. This process creates many layers of mineral deposits creating a hard fossil record.
Permineralized fossils are formed when mineral rich solutions penetrate porous tissue, such as bone or wood. The minerals are precipitated from the solution and fill the pores and voids. Some of the original organic material remains, but is now embedded in a mineral matrix.
Bone and wood tissues act as excellent frameworks to preserve cell structure. Silicates, iron oxides, metal sulphides, native elements, carbonates and sulfates may be involved in permineralization.
Permineralization is one of the most faithful modes of fossil preservation. In fact, scientists have tried to replicate the process in the laboratory, but no artificial permineralization equals the best natural preservation by cryptocrystalline silica or calcium carbonate (Viney, 2008).
Importance
Since the permineralizations of organisms are three-dimensional fossils with organic matter replaced by minerals, what we are mainly told are the internal structures of organisms.
Figure 3:"Leonardo"the"dinosaur mummy"found in Montana USA With more than 90% of its soft tissue preserved through a permineralization process.
The mineralization process itself helps to prevent compaction of the tissue, which could distort dryyoxil in the actual proportions of size of the various organs.
Permineralizations are also not"limited"to hard parts of the body (such as bones or shells), but can also be found by preserving the soft parts of the body.
This could be very important for researchers who want to look at what life was like in the past in relation to what it is now in the present. One example are the fragile reproductive structures of many plants (Discovery Communications, Inc., S.F.).
References
- Conjecture Corporation. (S.F.). What is Permineralization? Retrieved from wisegeek.org: wisegeek.org.
- Discovery Communications, Inc. (S.F.). Secrets of the Dinosaur Mummy. Retrieved from press.discovery.com: press.discovery.com.
- Fossil Formation The Work of Ages. (S.F.). Retrieved from fossils-facts-and-finds: fossils-facts-and-finds.com.
- Fossils Window to the past. (S.F.). Retrieved from ucmp.berkeley.edu: ucmp.berkeley.edu.
- ROVIRA, M. Q. (2016, January 25). KNOWING FOSSILS AND THEIR AGE. Retrieved from allyouneedisbiology: allyouneedisbiology.wordpress.com.
- The Virtual. (S.F.). Fossilization - How Fossils Form. Retrieved from fossilmuseum: fossilmuseum.net.
- S. department of interior. (S.F). Activity 3: Permineralization. Retrieved from nps.gov: nps.gov.
- Viney, M. (2008). Permineralization. Retrieved from petrifiedwoodmuseum.org: petrifiedwoodmuseum.org.