Permineralization
Encyclopedia
Permineralization is a process of fossil
ization in which mineral deposits form internal casts of organisms. Carried by water, these minerals fill the spaces within organic tissue. Because of the nature of the casts, permineralization is particularly useful in studies of the internal structures of organisms, usually of plants.
, is completely filled. The cell walls themselves remain intact surrounding the crystals. Permineralization is different from petrification in that the organic material is only filled with minerals and not completely replaced. Permineralization can occur in several ways:
s are the fossilizations of many different plants and their tissues. They often occur in the presence of seawater or acidic peat. Coal balls are calcareous permineralizations of peat by calcium
and magnesium
carbonates. Almost always spherical in shape and ranging from a few grams to several hundred kilograms in mass, coal balls are formed when water containing carbonate permeates the cells of an organism. This type of fossilization yields information about plant life in the Upper Carboniferous
Period (325 to 280 million years ago).
and iron
. Organisms are pyritized when they are in marine sediments saturated with iron sulfides. Pyrite
is iron sulfide. As organic matter decays it releases sulfide which reacts with dissolved iron in the surrounding waters. Pyrite replaces carbonate shell material due to an undersaturation of carbonate in the surrounding waters. Some plants are also pyritized when they are in a clay terrain, but to a lesser extent than in a marine environment. Some pyritized fossils include marine arthropods and plants.
A permineralized fossil will also reveal much about the environment an organism lived in and the substances found in it since it preserves soft body parts.
This helps researchers investigate the plants, animals, and microbes of different time periods.
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
ization in which mineral deposits form internal casts of organisms. Carried by water, these minerals fill the spaces within organic tissue. Because of the nature of the casts, permineralization is particularly useful in studies of the internal structures of organisms, usually of plants.
Process
Permineralization is a type of fossilization involving deposits of minerals within the cells of organisms. Water from the ground, lakes, or oceans seeps into the pores of organic tissue and forms a crystal cast with deposited minerals. Crystals begin to form in the porous cell walls. This process continues on the inner surface of the walls until the central cavity of the cell, the lumenLumen (anatomy)
A lumen in biology is the inside space of a tubular structure, such as an artery or intestine...
, is completely filled. The cell walls themselves remain intact surrounding the crystals. Permineralization is different from petrification in that the organic material is only filled with minerals and not completely replaced. Permineralization can occur in several ways:
Silicification
In silicification, silicate minerals are released due to the weathering of rocks. The silica makes its way into a body of still water. Eventually, the mineral laden water permeates the pores and cells of some organism, where it becomes a gel. Over time, the gel will dehydrate, forming an opaline crystal structure that is an internal cast of the organism. This accounts for the detail found in permineralizations. Silicification reveals information about what type of environment the organism was likely to live in. Most fossils that have been silicified are bacteria, algae, and other plant life. Silicification is the most common type of permineralization.Carbonate mineralization
Carbonate mineralization involves the formation of coal balls. Coal ballCoal ball
Coal balls, despite their name, are calcium-rich masses of permineralised life forms, generally having a round shape. Coal balls were formed roughly , during the Carboniferous Period...
s are the fossilizations of many different plants and their tissues. They often occur in the presence of seawater or acidic peat. Coal balls are calcareous permineralizations of peat by calcium
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...
and magnesium
Magnesium
Magnesium is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole...
carbonates. Almost always spherical in shape and ranging from a few grams to several hundred kilograms in mass, coal balls are formed when water containing carbonate permeates the cells of an organism. This type of fossilization yields information about plant life in the Upper Carboniferous
Carboniferous
The Carboniferous is a geologic period and system that extends from the end of the Devonian Period, about 359.2 ± 2.5 Mya , to the beginning of the Permian Period, about 299.0 ± 0.8 Mya . The name is derived from the Latin word for coal, carbo. Carboniferous means "coal-bearing"...
Period (325 to 280 million years ago).
Pyritization
This method involves the elements sulfurSulfur
Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...
and iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...
. Organisms are pyritized when they are in marine sediments saturated with iron sulfides. Pyrite
Pyrite
The mineral pyrite, or iron pyrite, is an iron sulfide with the formula FeS2. This mineral's metallic luster and pale-to-normal, brass-yellow hue have earned it the nickname fool's gold because of its resemblance to gold...
is iron sulfide. As organic matter decays it releases sulfide which reacts with dissolved iron in the surrounding waters. Pyrite replaces carbonate shell material due to an undersaturation of carbonate in the surrounding waters. Some plants are also pyritized when they are in a clay terrain, but to a lesser extent than in a marine environment. Some pyritized fossils include marine arthropods and plants.
Scientific implications
Permineralized fossils preserve original cell structure, which can help scientists study an organism at the cellular level. These are three-dimensional fossils, which create permanent molds of internal structures. The mineralization process itself helps prevent tissue compaction, which distorts the actual size of organs.A permineralized fossil will also reveal much about the environment an organism lived in and the substances found in it since it preserves soft body parts.
This helps researchers investigate the plants, animals, and microbes of different time periods.
Examples of permineralization
- Most dinosaur bones are permineralized.
- Petrified woodPetrified woodPetrified wood is the name given to a special type of fossilized remains of terrestrial vegetation. It is the result of a tree having turned completely into stone by the process of permineralization...
: Permineralization is the first step in petrification. In petrification, the cellulose cell walls are completely replaced by minerals. - Some examples of soft-bodied pyritization are Beecher's Trilobite Bed (OrdovicianOrdovicianThe Ordovician is a geologic period and system, the second of six of the Paleozoic Era, and covers the time between 488.3±1.7 to 443.7±1.5 million years ago . It follows the Cambrian Period and is followed by the Silurian Period...
) and the Hunsrück SlateHunsrück SlateThe Hunsrück Slate is a Lower Devonian lithostratigraphic unit, a type of rock strata, in the German regions of the Hunsrück and Taunus. It is a lagerstätte famous for exceptional preservation of a highly diverse fossil fauna assemblage.-Geology:...
(DevonianDevonianThe Devonian is a geologic period and system of the Paleozoic Era spanning from the end of the Silurian Period, about 416.0 ± 2.8 Mya , to the beginning of the Carboniferous Period, about 359.2 ± 2.5 Mya...
)