A Silicified Carboniferous Lycopsid Forest in the Colorado Rocky Mountains, USA

Abstract

The 1930 discovery of Carboniferous lycopsid fossils in south central Colorado resulted in the naming of a new species of scale tree, Lepidodendron johnsonii (=Lepidophloios johnsonii (Arnold) DiMichele). Cellular structures of L. johnsonii axes and periderm are preserved in silica—an unusual mode of fossil preservation for Pennsylvanian lycopsid plant remains. The early reports on the Trout Creek lycopsid fossils focused on taxonomic and paleobotanical aspects. Our 2019 reinvestigation of the locality produced many new specimens and a wealth of new data from a variety of analytical methods. Optical microscopy, X-ray diffraction, scanning electron microscopy, energy dispersive electron spectroscopy, determination of specific gravity, and Loss on Ignition provide details of mineralization. Cell walls are preserved with very small fine quartz particles, and cell lumina are filled with microcrystalline quartz. Some cell exteriors are encrusted with euhedral quartz crystals. These multiple forms of quartz are evidence that petrifaction involved several episodes of silicification. The dark color of the fossil wood and siliceous matrix appears to be caused by traces of dispersed carbon, but 500 °C Loss on Ignition reveals that the fossil wood preserves only very small amounts of the original organic matter.

Mineralogical and paleobotanical investigations of Oligo-Miocene petrified wood from the southwest of Thrace Basin (NW Turkey)

“…Recent studies about this subject found that silica may be in the form of opal-A, opal-CT (chalcedony-tridymite) and quartz, respectively, during diagenesis in aqueous sediments (Mustoe, 2017;Viney et al, 2019). It is a common belief that silicification occurs in this order in fossilized wood, but in many studies the fossilization of woods may involve multiple phases of mineralization.…”

“…Petrified wood is a fossil formed due to burial of trees by sediments in areas close to volcanic activity and is an important resource for understanding biodiversity and paleogeography. The petrification of wood occurs in the form of replacement of organic parts by inorganic materials in waters affected by volcanism or the permineralization of inorganic material in tissues (Mustoe, 2017;Mustoe and Viney, 2017;Viney et al, 2019). During the silicification process, organic substances in the tissues of the tree are removed and are replaced by silica and/or some other elements (Ca, Cu, Fe etc.).…”