By Than Htun (Myanmar Geosciences Society)
“Look deep into nature, and then you will understand everything better”
In 1835, Charles Darwin discovered a petrified forest in Auga de la Zorra, Argentina. His discoveries made him question the origin of species. He later recorded his observations in “A Naturalist Voyage (1845)”. Thus, the discovery of fossil forests may have been one of the driving factors for Darwin’s theory of evolution by natural selection. The ancient forest (237-242 million years old) was interpreted to be a subtropical dry seasonal forest and is now known as the “Darwin Forest” (Dr. Telmo Pievant et al., 2009).
Fossil trees help us to have a better understanding of the past vegetation and climate of the region. Well preserved cell structure can allow scientists to identify what kind of trees they were. A single petrified tree is like a page from a giant ancient book telling the story of a petrified forest.
Petrified wood (from the Greek 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. It is the result of a tree or tree-like plants having completely transitioned to stone by the process of permineralization. All the organic materials have been replaced with minerals (mostly a silicate, such as quartz), while retaining the original structure of the stem tissue. Unlike other types of 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 under sediment or volcanic ash and is initially preserved due to a lack of oxygen which inhibits aerobic decomposition. Mineral-laden water flowing through the covering material deposits minerals in the plant’s cells; as the plant’s lignin and cellulose decay, a stone mold forms in its place. The organic matter needs to become petrified before it decomposes completely.
Some people wondering how they can know whether this is petrified wood or just a rock. Petrified wood that we see nowadays was once a living tree. Although the wood was turned into stone, the wood sometimes retains both its external shape, i.e., grain, burrs, knots, branches, and its internal stricture, such as growth rings, vessels, rays, tracheids, which are different in each tree species, as it is gradually petrified.
Paleobotanists identify petrified wood by comparing the anatomical structure of the fossil wood with that of living wood and other fossil wood that has been previously identified. The scientific name given for petrified wood often uses the genus name of plants considered to be its along with the ending “Oxylon” which comes from the Greek word for “wood”.
Does it take over 100,000 or million years?
It can, but it does not always take that long for wood to be completely turned into stone. Under some conditions, rapid natural petrification can occur, such as in Yellowstone National Park, USA, within sedimentary strata around volcanoes. The rates of silica deposition into blocks of wood were between 0.1 and 4.0 mm/year in alkaline springs.
A research experiment was done by Japanese scientists. They placed ten pieces of fresh alder wood into Tateyama Hot Spring (50-52°C and pH 2.95 – 3.0), in central Japan. The pieces of wood were separately removed in different years and the amount of silicification (SiO2) was measured. The results indicated that the wood had been rapidly petrified in 7 to less than 36 years.
There are some examples of the rapid petrification in nature. Do you know that it can do by people too? One experiment on the rapid petrification of wood from silica gel was done in the laboratory in the USA. Only one day was required to crystallize quartz at 300°C and 3kilobars (about 3,000 atm) pressure the same degree of crystallization occurred in 7 days.
Petrified wood is “a key to the past” as it once belong to living trees. Some petrified wood takes us back to a world 400 million years ago. The study of petrified wood gives us very useful information. Let’s see what values petrified wood has.
1. Biological Value: Petrified wood expands and contracts a scientist’s knowledge of botany and paleobotany by providing a better understanding of biology and evolution of plants, plant taxonomy, plant environment and paleoecology.
2. Geological Value: Petrified wood enables us to tell the stratigraphic age of the enclosing sediments and supplies important evidence in support of theories of continental drift.
3. Geographical value: Petrified tells us what the ancient environment, including the paleoclimate, was like. The palaeoflora can help us to predict climate trends in the future.
4. Archaeological Value: Petrified wood from some localities provides important archaeological evidence such as in Myanmar, where the tools from the “Anyathian Culture” (Palaeolithic) were made of petrified wood. In Thailand, Stone Age tools made of petrified wood were also discovered for the first time in Sung Noen District, Nakhon Ratchasima. Archaeologists have given the name “Sung Noen Culture” to the people who made their tools. The study of artefacts has indicated that petrified wood was used as building material, tools and for game balls in ancient American cultures.
5. Tourism: Many countries have set up natural parks, national monuments, or museums to conserve petrified wood, e.g., Lesvos Petrified Forest Geopark, Greece, Petrified Wood National Park, Arizona, USA, and the Petrified Forest Shenzhen Fairy Lake, China, where people can learn to appreciate its true value.
6. Esthetical value: Because of its fascinating colours and shapes, petrified wood has been used for a variety of esthetical purposes, such as for garden decoration and for making ornaments and furniture.
Thai Story of Petrified Wood
In Thailand, some people believe that there is a spirit in large petrified tree trunks, so people set up a sacred shrine covering or near the petrified wood to pray for protection or for whatever they wish. Some believe that touching the petrified wood will make the person have a long life because of antiquity of the petrified wood.
“Once upon a time, a goddess tried to light a fire with numerous logs. But the wood was wet, so she could not succeed. In anger, she called down a curse upon the wood to be turned into stone. Therefore, the wood will never be able to be lighted”. That’s how petrified wood appeared on the earth. “These giant petrifications were spent arrow shafts and spears dispatched by the Thunder God Shinauav and his enemies during a great battle…belief of members of the Paiute tribe. “They were the bones of the great giant monster Yeitso”..belief members of the Navajo tribe.
Petrified wood is called by different names in each region of Thailand, e.g., “Hin Chauk” or “Hin Fa”. Some call it a rock followed by the local name of the tree that the prettified wood looks like. “In old times, people in Thailand selected the glossy petrified wood to hit with steel to spark a fire for smoking and cooking”, said an old farmer from Hin Lek Fire Village, Khu Muang District, Buri Ram Province as matches were hard to find at that time in the countryside. The name of the village “Hin Lek Fire” means “flint”, referring to the petrified wood that was used. “Hin” = rock, “Chauk” is a local name in the northeast for the tree. Terminalia alata, “Fa” is from the word “Rok Fa” the common Thai name for the same tree.
Many Petrified trunks found in Suranaree subdistrict: Muang Nakhon Ratchasima, are opalized wood containing silica (Si O2) and 3-12% water (H2O) by weight. The Moh’s scale hardness is 5.5-6. The opalized wood is glossy in appearance, similar to pearl and glass, and varies in colour, e.g., milky white, orange, red, green, light blue. Although the cell structures in some opalized wood are not well preserved, there are some indications of cellular arrangement. In some specimens, the cell structures are excellently preserved from when they were living trees, which is remarkable, as the fossils date back more than 800,000 years. The petrified wood enables wood anatomists to identify the palaeoflora and reconstruct the palaeoenvironment.
The Petrified Wood in Myanmar
Regarding fossil wood or Enjin Kyauk in Myanmar Miss Ruth Holden, Geological Survey of India, pointed out in her “A fossil wood from Burma” in 1916 as follows:
The extraordinary abundance of fossil wood to be found in Upper Burma has been noticed by all travellers in that region from the time of Crawfurd’s visit in 1827. Some striking is its occurrence that the beds in which it appears were long known as the “Fossil Wood Group.” More recently, however, a certain number of specimens have been found in the underlying Pegu series, so, to make the distinction between the two series clear, the name of the upper one has been changed to Irrawaddian. As regards age, the former is referred to the Oligocene or Miocene; the later to the Pliocene. The manner of preservation has been a subject of more or less controversy, Buckland states that part is calcified and part silicified; Theobald asserts that “none of the fossil wood is mineralized by calcification,” and this observation is confirmed by Oldham. Pascoe, however, says that both types of petrifaction are to be encountered, though the former is the more common. The nature of the wood has always been a mystery. Buckland suggested that it resembles the tamarind, but presented no evidence pointing to such a conclusion. On the other hand, the natives claim to be able to recognize two varieties, one of which they identify as the modern Enjin tree (Hopea suava) and the other as the Thiya (Shorea obtuse). In order to settle the matter, Theobald in 1867 sent some specimens to the British Museum for microscopic examination, but the preservation proved to be unsatisfactory that it was only possible to ascertain that it was exogenous, not coniferous. Even in 1895, Noetling comments on the fact that though quantities have been brought to England, no scientific investigation has hitherto been made. In 1914, however, Mr. F.W. Cuffe, presented to the Sedgwick Museum, Cambridge, a calcified specimen from Gwedindon in the Sagaing District. This was submitted by Dr. Arber to the writer for sectioning, and although the condition of the tissues leaves much to be desired, it is believed that its microscopic structure may be made out with sufficient detail to warrant description.
Dr. H.L. Chhibber, 1934, Geological Survey of India; Head of the Department of Geology and Geography, University College, University of Rangoon described in his ‘The Geology of Burma’ that with the exception perhaps of precious stones like rubies the fossil wood of Burma has attracted the attention of travellers more than any other mineral substance. It was noticed as early as the end of the eighteen century, or early in the nineteenth, by travellers like Symes, Crawford, Yule and Oldham. The Burmese always refer the fossil wood to Ingyin (Pentacme suavis), which grows so commonly in those parts. Both monocotyledonous and dicotyledonous fossil wood have been recorded from the Irrawaddy Series and the former includes palms from close to the Pegu-Irrawaddian boundary. As regards the dicotyledonous wood, which forms the bulk of the material, Miss Ruth Holden has described Dipterocarpoxylon Burmese. The monocotyledonous wood represents the remains of palms which show very clearly the cordiform vascular bundles and their obliquity to the stem axis when about to enter a leaf. Theobald attributed the silicification of the wood to the agency of springs consequent upon volcanic activity. Such a theory has to be rejected not only because of the absence of siliceous sinter and cherty beds but also of the discrepancy in age between the Irrawaddy Series and the main volcanic rocks of Burma, some of which are decidedly younger than the former. Xenoliths of fossil wood are even found associated with the andesite lava of Mount Popa.
In 2017, Nareerat Boonchai from Thailand has been studied some petrified trees near Thanbo village in Mount Popa National Geopark. Fossil discovery in Myanmar has increased and thus should be preserved for research of the world history, natural heritage of public and can be developed to a learning resource and tourism places to generate revenue for the country. However, since pre-war days, the fossil could be destroyed and misused or be commercially used. The consequence is the loss of the natural heritage of the public, which has enormous value.
The Ministry of Natural Resources and Environmental Conservation is the main government organization serving the country in term of research and conserve geological resources including fossils. Therefore, it is necessary to establish specific law of protection, conservation and management the fossil. As a result, the high value of the fossil wood and other vertebrate fossils shall be under protection, conservation and management as national properties for our next generation to come.
1. Khorat Fossil Museum, 2017. Nakhon Ratchsima, Thailand
2. Holden R. 1916. A fossil wood from Burma
3. H.L.Chhibber,1934. The Geology of Burma