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Abstract Worldwide, silicified woods are found in many geological formations. Significantly, the organic materials of wood are no longer dominant; almost all wood fossils have been mineralized into inorganic silica materials. These unique geological processes must be understood to develop better understanding on organic material fossilization, particularly in the micron scale. Therefore, our aim was to characterize the composition of silicified wood using comprehensive microanalysis. The methods utilized were XRF, ICP-MS, XRD, FTIR, and FE-EPMA. Specimens are from Jasinga, West Java, Indonesia. The results showed that wood silicification was controlled by the infiltration of silica from the host rock into the spaces of the wood structure. In Jasinga, they are controlled by Pliocene tuffaceous sedimentary rocks. The ratio of silica phases revealed a trend in the degree of silicification. Besides silica, the distribution of trace elements also demonstrates the geochemical interaction between the wood fossil and host rock. Wood fossils are affected by the gradual replacement of organic carbon-based materials with silica through silicification. Silica enrichment occurs in the internal of wood, facilitates permineralization and recrystallization. Silica replaces organic material and preserves the wood structures. The microanalytical approach provides comprehensive perspectives on wood petrification, leads to better insights for paleontological studies.

The early and middle Miocene in Turkey was characterised by a warm climate and a diversified and rich vegetation. Many fossil angiosperm genera have been identified from this period. The present study re-examined previously identified genera and identifed new samples of angiosperm wood remains. The studied material included thin sections housed at the Department of Forest Botany, Division of Forest Engineering, Faculty of Forestry, Istanbul University-Cerrahpasa, and also new ones. Twelve new species are described: Liquidambaroxylon efeae Akkemik sp. nov., Eucarpinoxylon kayacikii Akkemik sp. nov., Ostryoxylon gokceadaense Akkemik sp. nov., Quercoxylon yaltirikii Akkemik sp. nov., Cryptocaryoxylon grandoleaceum Akkemik sp. nov., Fraxinoxylon beypazariense Akkemik sp. nov., Prunoidoxylon prunoides Akkemik sp. nov., Populoxylon sebenense Akkemik sp. nov., Salicoxylon galatianum Akkemik sp. nov. Aceroxylon aceroides Akkemik sp. nov., Ulmoxylon kasapligilii Akkemik sp. nov. and Zelkovoxylon crystalliferum Akkemik sp. nov. In addition, four previously described species are documented for the early and middle Miocene: Pistacioxylon ufukii Akkemik and I. Poole, Fagoxylon radiatum Süss, Laurinoxylon litseoides Süss and Platanoxylon catenatum Süss and Müller-Stoll. In addition to the species descriptions, identification keys are given for all the genera recognised in this study, including all currently known fossil species of the respective fossil genera. These keys hold important new information, as they place the fossil species from Turkey in a wider taxonomic and biogeographic context. The results show that in the early and early-middle Miocene of Turkey a rich woody flora existed in well-drained upland or lowland and riparian areas. This flora comprised subtropical taxa along with warm-temperate taxa indicative of seasonality of rainfall as well as transitions to xeric conditions in the early Miocene.

The Fossil Forest of the Aragoncillo Range is one of several paleontological sites of exceptional scientific value in the Sierra de Selas (Province of Guadalajara, central Spain). This shows an accumulation of silicified tree trunks along with well-preserved macro- and microflora of lower Permian age. This ancient forest, dominated by tree ferns and conifers, was destroyed by volcanic eruptions that took place in many continental areas at this time. This site is in the Molina-Alto Tajo UNESCO Global Geopark, but it is highly vulnerable and has suffered continued impact from plundering. The lack of implementation of legislation that guarantees its conservation does not allow interested visitors to enjoy the site and understand the characteristics of life and climate of such a unique ecosystem from this time in Earth history.

Fossil forests are one of the important areas in terms of natural history, paleogeography and paleoclimatology. A new fossil forest was discovered in the area between the Tuzlagedik Tepe and the Sakizocak Tepe, Karatepe, the Alan Tepe, west of the Banaz district of Uşak province. In this area, silicified lateritic formations of Paleogene belonging to 2-60 meters thick are found in silicified tree fossils. The size of silicified tree fossils spread over a wide area reaches up to 1.5 m in length and 70 cm in diameter. The aim of this study is to diagnose these silicified trees, to determine the fossil forest characteristics and to evaluate paleogeography. Transverse, radial and tangent sections were taken from 4 samples which were examined macroscopically. As a result of the analysis it was concluded that silicified trees are Sequoioxylon. The presence of Sequoia trees, which don’t naturally spread in our country today, indicates that there is a marsh forest or riperian vegetation where temperate climatic conditions prevail during the Paleogene.

Thailand contains two notable fossil forest regions. Pleistocene fluvial sediments in the Tak region in the northern highlands contain silicified trunks of large trees. Deposits in the Khorat Plateau in northeast Thailand contain a multitude of wood fossils that span a probable age range of Miocene to Pleistocene. At Ban Tak fossil logs are primarily mineralized with crystalline quartz. Incomplete mineralization is characteristic of the Tak wood, with intercellular spaces commonly remaining open. The resulting permeability allows penetration of moisture, and allows introduction of microbes and the accumulation of clays, iron oxides, soluble salts and other materials that may cause discoloration and deterioration. Hydration swelling of these components results in stress. Excavation of the huge logs means that they occupy topographically low positions prone to flooding during the monsoon season. These factors make the fossils vulnerable to weathering. A variety of methods have been employed in attempts to reduce the damage, including the construction of various styles of shelters to protect the fossil logs from direct precipitation. At Khorat, compositions of individual specimens range from pure quartz and pure opal to mixtures of the two polymorphs. Many specimens are preserved indoors in the Khorat Fossil Museum in Mueang Nakhon Ratchasima District, both as indoor exhibits and as outdoor displays in a garden plaza. The environmental complexities at the Tak and Khorat fossil wood localities challenge conservators, but their creative attempts provide useful lessons for future preservation efforts. Our report describes the geologic setting and our research mineralogy of specimens at both localities, and discusses conservation strategies.

In this study, xeromorphy ratios were calculated for Acer L. (maple) fossil woods in order to infer the precipitation conditions in the Miocene at the sites of the fossils, based on a comparison with the xeromorphy ratios of selected extant Acer species. The four studied petrified wood samples came from three localities of the Galatean Volcanic Province in Turkey: Kozyaka village (Bolu Province, Seben District), İnözü Valley (Ankara Province, Beypazarı District), and Kıraluç precinct between Nuhhoca and Dağşeyhler villages (Ankara Province, Beypazarı District). The calculated xeromorphy ratios ranged from 3 to 18 for the present-day wood and from 13 to 19 for the early Miocene wood. Values over 10 (11–18) represent xeric conditions; the lower values (3–7) indicate mesic conditions in modern Acer woods. The xeromorphy ratios of the Miocene wood indicate xeric conditions; we conclude that the sites of the fossil Acer woods were xeric, very similar to the modern Acer woodlands of central and southern Anatolia.

Late Tertiary fossil woods from the state of Nevada provide an opportunity for observing the mineralization sequences that cause buried wood to become permineralized. Oligocene and Miocene caldera basins contain abundant petrified wood that ranges in composition from incipient silicification to complete permineralization. Examination of specimens from 21 localities reveals that the petrifaction sequence can follow multiple pathways. Fossil wood specimens from a single stratum may have different mineralization; silicification may vary even within a single specimen. Despite these variations, several trends are evident. Features in Nevada specimens suggest that two fundamental processes are involved: early mineralization of cell walls, and later silica deposition in lumina, vessels, and rot pockets from groundwater that permeated these open spaces. The process of open-space filling may be analogous to the genesis of geodes and veins, where multiple episodes of hydrothermal precipitation may produce opal, chalcedony, and quartz as deposits within a single cavity. Silica polymorphs may coexist as primary precipitates, or they may originate from solid-state transformation of a single parent material. Relic lepisphere textures observed in some chalcedony wood specimens are evidence of opal→chalcedony transition. In Nevada, specimens that contain crystalline quartz, this mineral appears to have been formed by direct precipitation in open spaces, not from recrystallization of chalcedony. Opal-A has seldom been reported in fossil wood, but this amorphous material is fairly common in Nevada specimens.

The fragments of petrified wood from the Permian deposits at the territory of Tatarstan were studied. Petrified wood is characterized by silification of the plant tissue with retention of its primary texture. Wood samples were investigated using optical microscopy, carbon isotope analysis, and electron microscopy with microprobe analysis. The mechanisms of substitution of the wood organic matter with soluble and colloidal silica were specified. Details were provided on paleoclimatic conditions for the growth of higher plants during the period of Permian sedimentation.

Gorontalo area is part of the arc volcano - plutonic North Sulawesi predominantly volcanic rocks and intrusif rock Eocene to Quaternary. The tectonic position makes the Gorontalo area of natural resource mining prospects both metallic and non metallic minerals. One of them is a non-metal potential of petrified wood. The purpose of this study to analyze the condition of geomorphology, lithology, stratgraphy, and determine the nature of the physical characteristics of petrified wood in order to formulate feasibility as gemstones. The method used qualitative and quantitative results of the field survey which is then compiled the results of the laboratory. Field analysis in the form of geological mapping, sampling and documentation of geological data. The laboratory analysis conducted mineralogical and geochemistry analysis in the form of X-Ray Diffraction (XRD) and X-Ray Fluorescence (XRF). Dissemination of research results, the petrified wood in Tohupo River and Molannihu River. Petrified wood found in fluvial and alluvial sediment in tuffaceous sandstone layer with two types of insitu and transported. Results of laboratory analysis both mineralogy and gochemistry indicates that the mineral constituent of petrified wood are Quartz (SiO2) with good quality so worty as a gemstone because of its aesthetic, translucent and hardness 7 Mohs Scale.

• Chapter 1. PaleoParks: Our paleontological heritage protected and conserved in the field worldwide, by Jere H. Lipps, p. 1-10, 20 figs. • Chapter 2. The Triassic Guanling fossil Group - A key GeoPark from Barren Mountain, Guizhou Province, China, by Xiaofeng Wang, Xiaohong Chen, Chuanshang Wang & Long Cheng, p. 11-28, 30 figs., 2 tables. • Chapter 3. The GeoPark of Haute-Provence, France - Geology and palaeontology protected for sustainable development, by Jean-Simon Pagès, p. 29-34, 11 figs. • Chapter 4. The protection and use of the geological and paleontological heritage in Baja California Sur, Mexico, by Javier Gaitán Morán & Alejandro Álvarez Arellano • Capítulo 4. El resguardo y aprovechamiento del patrimonio geológico y paleontológico en Baja California Sur, México, por Javier Gaitán Morán & Alejandro Álvarez Arellano, p. 35-48, 4 figs. • Chapter 5. Protecting fossil sites in New Zealand, by Bruce W. Hayward, p. 49-64, 10 figs., 6 tables. • Chapter 6. The Salt Range: Pakistan's unique field museum of geology and paleontology, by Shahid Jamil Sameeni, p. 65-73, 28 figs. • Chapter 7. Paleontological parks and museums and prominent fossil sites in Thailand and their importance in the conservation of fossils, by Nareerat Boonchai, Paul J. Grote & Pratueng Jintasakul, p. 75-95, 13 figs. • Chapter 8. Managing fossil resources at the Falls of the Ohio, Indiana and Kentucky, USA: A fossil park in an urban setting, by Alan Goldstein, p. 97-101, 8 figs., 1 table. • Chapter 9. Paleo-piracy endangers Vendian (Ediacaran) fossils in the White Sea - Arkhangelsk region of Russia, by Mikhail A. Fedonkin, Andrey Yu. Ivantsov, Maxim V. Leonov, Jere H. Lipps, Ekaterina A. Serezhnikova, Eugeniy I. Malyutin & Yuriy V. Khan, p. 103-111, 12 figs. • Chapter 10. Copper Canyon track locality (Pliocene) conservation strategies, Death Valley National Park, USA, by Torrey Nyborg, p. 113-119, 4 figs. • Chapter 11. A possible Late Miocene fossil forest PaleoPark in Hungary, by Géza Császár, Miklós Kázmér, Boglárka Erdei & Imre Magyar, p. 121-133, 19 figs.

Petrified wood has traditionally been divided into two categories based on preservation processes: permineralization (where tissues are entombed within a mineral-filled matrix) and replacement (where organic anatomical features have been replicated by inorganic materials). New analytical evidence suggests that for most petrified wood, permineralization and replacement are not independent processes; instead, both processes may occur contemporaneously during diagenesis. Infiltration of mineral-bearing groundwater may initially cause permineralization of cellular tissues, but the wood is undergoing gradual degradation. The degree of anatomical preservation thus depends on the relative rates of mineral precipitation and tissue destruction. Rapid rates of mineralization under relatively mild Eh and pH conditions favor the preservation of organic matter. These conditions appear to be more common for calcium carbonate deposition than for silicification, based on observations of fossil woods from many localities. Because of these preservational complexities, “mineralization” and “mineralized” are more accurate as general descriptive terms than “permineralization” and “permineralized”.

The Bruneau Woodpile site has long been popular among fossil collectors; however, the deposit has received scant attention from scientists. Our research reveals that the fossilized wood was deposited ca. 6.85 Ma, within the Chalk Hills Formation, and was mineralized with carbonate-fluorapatite. The diverse assemblage of conifers and hardwoods is representative of the warm temperate forests that flourished in southwest Idaho, USA during the late Miocene. Limb and trunk fragments preserved in a single thin sandstone bed appear to represent woody debris that was transported by streams. One possible explanation is that wood, pumice, and sandy volcaniclastic sediment arrived separately as a result of ordinary stream action, and later were combined into a single assemblage during a subsequent high-energy sedimentation event. We favor an alternate hypothesis: a catastrophic event (e.g., a windstorm) damaged trees on slopes bordering the ancient lake. Branches and small trunk fragments were carried by wind and rain into local streams and ponds where they became waterlogged. After a delay that allowed pumice and wood to become saturated, storm water transported these materials, along with finer volcaniclastic sediment, into a lake. The resulting density current produced a fining-upward sedimentary cycle where wood was preserved in the lowest, coarsest stratum.

An extensive fossil forest discovered in 2010 on private property in central Colorado, USA, has not previously been described in scientific literature. Horizontal partial logs originated as fluvially transported driftwood. A preliminary study of petrified wood specimens reveals evidence of a complex mineralization sequence that involved multiple episodes of mineral deposition, combined with diagenetic transformation of silica minerals. Specimens from two logs have opalized cell walls. However, minerals filling the cell interiors of these specimens vary. Vessel lumina are filled with chalcedony or crystalline quartz; tracheid lumina may contain opal or chalcedony. Specimens from 5 other logs contain quartz/chalcedony, but relict textures suggest cell walls were originally mineralized with opal that was later converted to microcrystalline silica. Pyrite, calcite, and iron oxides were observed as minor constituents in some specimens, providing additional evidence that fossilization occurred in multiple stages, with temporal and spatial variations in physical and chemical conditions causing episodic precipitation of various minerals within the buried wood. Trace element analyses suggest that Fe is the main source of fossil wood color.

Fossil forests have world-wide distribution, commonly preserving mineralized wood that displays vivid hues and complex color patterns. However, the origin of petrified color has received little scientific attention. Color of silicified wood may be influenced by the presence of relict organic matter, but the most significant contribution comes from trace metals. This study reports quantitative analysis of trace metals in 35 silicified wood samples, determined using LA-ICP-MS spectrometry. The most important of these metals is Fe, which can produce a rainbow of hues depending on its abundance and oxidation state. Cr is the dominant colorant for bright green fossil wood from Arizona, USA and Zimbabwe, Africa. Complex color patterns result from the progressive nature of the fossilization process, which causes wood to have varying degrees of permeability during successive episodes of permineralization. These processes include simple diffusion, chromatographic separation, infiltration of groundwater along fractures and void spaces, and oxidation/reduction.

The 1895 discovery of a petrified tree near Clover Creek in south-central Idaho, USA, attracted worldwide attention and resulted in the naming of a new species of ancient oak, Quercinium pliocaenicum Schuster. For more than a century, the discovery has largely been forgotten, even though specimens reside in reputable museums. Reinvestigation of the locality in 2014/2015 resulted in newly-collected specimens and a wealth of new data. Optical microscopy confirms the cellular anatomy used for the original taxonomic study. X-ray diffraction, scanning electron microscopy, energy-dispersive electron spectroscopy, Raman spectroscopy and cathodoluminescence microscopy reveal details of the mineralization, showing the presence of opal-CT as the primary component, with chalcedony as a lesser constituent. This mineralogy suggests petrifaction occurred in at least two stages, beginning with opalization of cellular tissue, leaving open vessels that became filled with chalcedony during a later mineralization episode. Clover Creek oak represents relict flora growing in a wetter climate before the uplift of the Cascade Range created a rain shadow that caused profound desertification of the inland Pacific Northwest.