木化石賞析
木化石是最少上億年的樹木被迅速埋葬地下后,木質(zhì)部分被地下水中的SiO?(二氧化硅)交換而成的樹木化石。它保留了樹木的木質(zhì)結(jié)構(gòu)和紋理。顏色為土黃、淡黃、黃褐、紅褐、灰白、灰黑等,拋光面可具玻璃光澤,不透明或微透明,因部分木化石的質(zhì)地呈現(xiàn)玉石質(zhì)感,又稱硅化木或樹化玉。硅化木是上億年前的樹木因種種原因被埋入地下,在地層中,樹干周圍的化學(xué)物質(zhì)如二氧化硅、硫化鐵、碳酸鈣等在地下水的作用下進(jìn)入到樹木內(nèi)部,替換了原來(lái)的木質(zhì)成分,保留了樹木的形態(tài),經(jīng)過(guò)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,常常稱為硅化木或樹化玉。
樹化石 是地質(zhì)學(xué)所稱硅化木中的極品,它誕生于距今2億多年的中生代時(shí)期,因突發(fā)的劇烈的地質(zhì)變化,將樹木深埋地下,經(jīng)過(guò)極為苛刻的地址條件形成,是天下稀有億萬(wàn)年前遺世孤品。木化石集天地之靈氣,納日月之精華。它是集木、石、玉為一體的寶石佳品。
硅化木從古生代石炭紀(jì)開始(始于距今3.55億年)到白堊紀(jì)中期(結(jié)束于距今1.25億年)之間均有分布。到21世紀(jì)為止最早的木化石是石炭紀(jì)早期的裸蕨植物化石,最新的為1.035億年前白堊紀(jì)晚期的硅化木。古代樹木因火山噴發(fā)或地殼運(yùn)動(dòng)等地質(zhì)作用而被埋入地下,由于處于缺水的干旱環(huán)境或與空氣隔絕,木質(zhì)不易腐爛,在漫長(zhǎng)的地質(zhì)作用過(guò)程中被含硅鈣物質(zhì)交換替代,替換的過(guò)程保留了木質(zhì)的纖維結(jié)構(gòu)和樹干的外形,使樹木變成化石。
樹木保存為化石的條件極為苛刻,樹干要想成為硅化木,先決條件是其樹干必須得到迅速掩埋,環(huán)境的特殊,與空氣隔絕這種迅速掩埋的情況畢竟是極少見的,因此,樹木成為化石的幾率非常小。
樹木被泥沙埋藏后,含豐富硅質(zhì)成分的地下水溶液一邊溶解樹木的木質(zhì)成分,一邊將自己攜帶的硅質(zhì)成分沉淀于所溶解的孔洞中,發(fā)生物質(zhì)交換替代現(xiàn)象。如果溶解和交替速度相等,且以分子相交換,則可保存樹木的微細(xì)結(jié)構(gòu),如年輪及細(xì)胞輪廓等。如交替速度小于溶解速度,則主要保存了樹木的形態(tài),年輪一般不清楚。
最后,樹木的原來(lái)成分已蕩然無(wú)存,全部由含硅鈣成分的石質(zhì)所取代。之后,經(jīng)過(guò)壓實(shí)、固結(jié)、成巖,原來(lái)的樹木就完全變成了堅(jiān)硬的石頭木化石。
見證億萬(wàn)年地質(zhì)變遷由于硅化木的木質(zhì)纖維結(jié)構(gòu)甚至細(xì)胞結(jié)構(gòu)和樹干外形、樹皮、年輪、蟲洞等特征得以保存,因此它不但可以其材質(zhì)展示富貴和美麗,還可以其化石的年輪、樹皮、節(jié)瘤、蟲洞、肌理等斑斕多姿的特征記錄和見證著億萬(wàn)年的地質(zhì)變遷和物種衍化,為人們研究古植物及古生物史以及古代地質(zhì)和氣候變化提供了線索,其產(chǎn)地也被世界上很多國(guó)家建設(shè)成為硅化木國(guó)家公園。
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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