Experimental silicification of wood

点击翻译按钮获取中文摘要

An interesting and important process for palaeobotany is the fossilization by silicification. Here, organic structures of plant tissue are replaced by silica, occasionally to such fine detail that physiological processes can still be recognized. The factors driving SiO2 to enter plant tissue and be precipitated as opal are not well known, and it is unclear how long it takes to permineralize trees that measure meters in diameter by silica. We report here on reconnaissance experiments to silicify wood under natural conditions, using volcanic glass as a silica source. Our experiments suggest that the early stages of silicification, i.e. the filling of voids in the wood structure by opal, are driven by a gradient in pH, which is established between the wood and its lithic substrate in which the wood is buried. In this application, experiments are proposed to (1) identify factors governing silicification of wood, (2) determine the compositions of liquids exchanged between wood and the lithic substrate, and (3) approximate how long it takes to silicify wood logs as massive as those of the petrified forests of Arizona or Lesvos.