木化石赏析

木化石是最少上亿年的树木被迅速埋葬地下后，木质部分被地下水中的SiO₂（二氧化硅）交换而成的树木化石。它保留了树木的木质结构和纹理。颜色为土黄、淡黄、黄褐、红褐、灰白、灰黑等，抛光面可具玻璃光泽，不透明或微透明，因部分木化石的质地呈现玉石质感，又称硅化木或树化玉。硅化木是上亿年前的树木因种种原因被埋入地下，在地层中，树干周围的化学物质如二氧化硅、硫化铁、碳酸钙等在地下水的作用下进入到树木内部，替换了原来的木质成分，保留了树木的形态，经过石化作用形成的植物化石，因其中所含的二氧化硅成分多，所以，常常称为硅化木或树化玉。

树化石 是地质学所称硅化木中的极品，它诞生于距今2亿多年的中生代时期，因突发的剧烈的地质变化，将树木深埋地下，经过极为苛刻的地址条件形成，是天下稀有亿万年前遗世孤品。木化石集天地之灵气，纳日月之精华。它是集木、石、玉为一体的宝石佳品。

硅化木从古生代石炭纪开始（始于距今3.55亿年）到白垩纪中期（结束于距今1.25亿年）之间均有分布。到21世纪为止最早的木化石是石炭纪早期的裸蕨植物化石，最新的为1.035亿年前白垩纪晚期的硅化木。古代树木因火山喷发或地壳运动等地质作用而被埋入地下，由于处于缺水的干旱环境或与空气隔绝，木质不易腐烂，在漫长的地质作用过程中被含硅钙物质交换替代，替换的过程保留了木质的纤维结构和树干的外形，使树木变成化石。

树木保存为化石的条件极为苛刻，树干要想成为硅化木，先决条件是其树干必须得到迅速掩埋，环境的特殊，与空气隔绝这种迅速掩埋的情况毕竟是极少见的，因此，树木成为化石的几率非常小。

树木被泥沙埋藏后，含丰富硅质成分的地下水溶液一边溶解树木的木质成分，一边将自己携带的硅质成分沉淀于所溶解的孔洞中，发生物质交换替代现象。如果溶解和交替速度相等，且以分子相交换，则可保存树木的微细结构，如年轮及细胞轮廓等。如交替速度小于溶解速度，则主要保存了树木的形态，年轮一般不清楚。

最后，树木的原来成分已荡然无存，全部由含硅钙成分的石质所取代。之后，经过压实、固结、成岩，原来的树木就完全变成了坚硬的石头木化石。

见证亿万年地质变迁由于硅化木的木质纤维结构甚至细胞结构和树干外形、树皮、年轮、虫洞等特征得以保存，因此它不但可以其材质展示富贵和美丽，还可以其化石的年轮、树皮、节瘤、虫洞、肌理等斑斓多姿的特征记录和见证着亿万年的地质变迁和物种衍化，为人们研究古植物及古生物史以及古代地质和气候变化提供了线索，其产地也被世界上很多国家建设成为硅化木国家公园。

Wood fossils are tree fossils formed by exchanging the wood part with SiO ν (silica) in groundwater after the trees of at least hundreds of millions of years are quickly buried underground. It retains the wood structure and texture of trees. The colors are earthy yellow, light yellow, yellowish brown, red brown, gray white, gray black, etc. the polished surface can have glass luster, opaque or slightly transparent. Because the texture of some wood fossils presents jade texture, it is also called silicified wood or tree jade. Silicified wood is a tree hundreds of millions of years ago, which was buried underground for various reasons. In the stratum, chemicals around the trunk, such as silica, iron sulfide and calcium carbonate, enter into the tree under the action of groundwater, replacing the original wood components and retaining the shape of the tree. Plant fossils formed through fossilization contain a lot of silica, so, It is often called silicified wood or Shuhua jade.

Tree fossil It is the best of silicified wood in geology. It was born in the Mesozoic era more than 200 million years ago. Due to sudden and violent geological changes, the trees were deeply buried underground and formed through extremely harsh address conditions. It is a rare and isolated product in the world hundreds of millions of years ago. The wood stone sets the spirit of heaven and earth, the essence of the sun and moon. It is a gem integrating wood, stone and jade.

Silicified wood is distributed from the Paleozoic Carboniferous (starting from 355 million years ago) to the Middle Cretaceous (ending at 125 million years ago). By the 21st century, the earliest wood fossils are naked fern fossils in the Early Carboniferous, and the latest is silicified wood in the late Cretaceous 103.5 million years ago. Ancient trees were buried underground due to geological processes such as volcanic eruption or crustal movement. Because they were in a dry environment with water shortage or isolated from the air, the wood was not perishable. In the long process of geological processes, it was replaced by silicon calcium containing materials. The replacement process retained the fiber structure and trunk shape of the wood, making the trees become fossils.

The conditions for the preservation of trees as fossils are extremely harsh. If the trunk wants to become silicified wood, the prerequisite is that its trunk must be buried quickly. Due to the special environment and isolation from the air, this kind of rapid burial is extremely rare after all. Therefore, the probability of trees becoming fossils is very small.

After the trees are buried by sediment, the groundwater solution rich in siliceous components dissolves the wood components of the trees and precipitates the siliceous components carried by them in the dissolved holes, resulting in material exchange and substitution. If the dissolution and alternation rates are equal and exchanged by molecules, the fine structures of trees, such as annual rings and cell contours, can be preserved. If the alternation speed is less than the dissolution speed, the shape of trees is mainly preserved, and the annual rings are generally unclear.

Finally, the original components of the trees have disappeared and are all replaced by stone containing silicon and calcium. After compaction, consolidation and diagenesis, the original trees completely turned into hard stone and wood fossils.

Witness hundreds of millions of years of geological changes. Because the wood fiber structure, even cell structure, trunk shape, bark, ring, wormhole and other characteristics of silicified wood are preserved, it can not only show its wealth and beauty, but also record and witness hundreds of millions of years of geological changes and species evolution with the colorful characteristics of its fossil ring, bark, nodule, wormhole and texture, It provides clues for people to study the history of ancient plants and paleontology, ancient geology and climate change. Its origin has also been built into silicified wood National Park by many countries in the world.

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