Polished slice of a petrified tree from the Late TriassicEpoch (approximately 230 million years ago) found in Arizona. The remains of insects can be detected in an enlarged image.Petrified log in Paleorrota geopark, BrazilPetrified log at the Petrified Forest National ParkPolished petrified woodThe outline of cells visible in a segment of petrified woodPolished slice of petrified woodPetrified logsPetrified Acacia woodPuyango petrified forestPetrified log and WelwitschiaatNamibiaPetrified forest (2014)Chunk of petrified wood near El Kurru (Northern Sudan)
Petrified wood (from the Latin root petro meaning "rock" or "stone"; literally "wood turned into stone") is the name given to a special type of fossilized remains of terrestrial vegetation. Petrifaction is the result of a tree or tree-like plants having transitioned to stone by a mineralization process that often includes permineralization and replacement. [1] The organic materials making up cell walls have been replicated with minerals (mostly a silicate, such as opal, chalcedony, or quartz). In some instances, the original structure of the stem tissue may be partly retained. Unlike other plant fossils, which are typically impressions or compressions, petrified wood is a three-dimensional representation of the original organic material.
The petrifaction process occurs underground, when wood becomes buried in water saturated sedimentorvolcanic ash. The presence of water reduces the availability of oxygen which inhibits aerobic decomposition by bacteria and fungi. Mineral-laden water flowing through the sediments may lead to permineralization, which occurs when minerals precipitate out of solution filling the interiors of cells and other empty spaces. During replacement, the plant's cell walls act as a template for mineralization. [2] There needs to be a balance between the decay of cellulose and lignin and mineral templating for cellular detail to be preserved with fidelity. Most of the organic matter often decomposes, however some of the lignin may remain.[3] Silica in the form of Opal-A, can encrust and permeate wood relatively quickly in hot spring environments.[4] However, petrified wood is most commonly associated with trees that were buried in fine grained sediments of deltas and floodplains or volcanic lahars and ash beds. [5][6]Aforest where such material has petrified becomes known as a petrified forest.
Elements such as manganese, iron, and copper in the water/mud during the petrification process give petrified wood a variety of color ranges. Pure quartzcrystals are colorless, but when contaminants are added to the process the crystals take on a yellow, red, or another tint.
Following is a list of contaminating elements and related color hues:[7][8]
Petrified wood can preserve the original structure of the stem in all its detail, down to the microscopic level. Structures such as tree rings and the various tissues are often observed features.
Petrified wood is a fossil in which the organic remains have been replaced by minerals in the slow process of being replaced with stone. This petrification process generally results in a quartz chalcedony mineralization. Special rare conditions must be met in order for the fallen stem to be transformed into fossil wood or petrified wood. In general, the fallen plants get buried in an environment free of oxygen (anaerobic environment), which preserves the original plant structure and general appearance. The other conditions include a regular access to mineral rich water in contact with the tissues, replacing the organic plant structure with inorganic minerals. The end result is petrified wood, a plant, with its original basic structure in place, replaced by stone.
Egypt – petrified forest in Cairo-Suez road, declared a national protectorate by the ministry of environment, also in the area of New Cairo at the Extension of Nasr City, El Qattamiyya, near El Maadi district, and Al Farafra oasis.[9]
Libya – Great Sand Sea – Hundreds of square miles of petrified trunks, branches and other debris mixed with Stone Age artifacts[citation needed]
Germany – the museum of natural history in Chemnitz has a collection of petrified trees, from the in situ Chemnitz petrified forest, found in the town since 1737.
Greece – Petrified forest of Lesvos, at the western tip of the island of Lesbos, is possibly the largest of the petrified forests, covering an area of over 150 km2 (58 sq mi) and declared a National Monument in 1985. Large, upright trunks complete with root systems can be found, as well as trunks up to 22 m in length.
Canada – in the badlands of southern Alberta; petrified wood is the provincial stone of Alberta. Axel Heiberg IslandinNunavut has a large petrified forest. In and around the North Saskatchewan river, around the Edmonton area. Blanche Brook, in Stephenville, Newfoundland, has 305-million-year-old examples.[19]
^Akahane, Hisatada; Furuno, Takeshi; Miyajima, Hiroshi; Yoshikawa, Toshiyuki; Yamamoto, Shigeru (2004-07-15). "Rapid wood silicification in hot spring water: An explanation of silicification of wood during the Earth's history". Sedimentary Geology. 169 (3–4): 219–228. Bibcode:2004SedG..169..219A. doi:10.1016/j.sedgeo.2004.06.003.
