Mineralogy of Miocene Petrified Wood from Central Washington State, USA

Abstract

Silicified wood occurs abundantly in Middle Miocene flows and sedimentary interbeds of the Columbia River Basalt Group (CRBG) in central Washington State, USA. These fossil localities are well-dated based on radiometric ages determined for the host lava. Paleoenvironments include wood transported by lahars (Ginkgo Petrified Forest State Park), fluvial and palludal environments (Saddle Mountain and Yakima Canyon fossil localities), and standing forests engulfed by advancing lava (Yakima Ridge fossil forest). At all of these localities, the mineralogy of fossil wood is diverse, with silica minerals that include opal-A, opal-CT, chalcedony, and macrocrystalline quartz. Some specimens are composed of only a single form of silica; more commonly, specimens contain multiple phases. Opal-A and Opal-CT often coexist. Some woods are mineralized only with chalcedony;however, chalcedony and macrocrystalline quartz are common as minor constituents in opal wood. In these specimens, crystalline silica filling fractures, rot pockets, and cell lumen may occur. These occurrences are evidence that silicification occurred as a sequential process, where changes in the geochemical environment or anatomical structures affected the precipitation of silica. Fossilization typically began with precipitation of amorphous silica within cell walls, leaving cell lumen and conductive vessels open. Diagenetic transformation of opal-A to opal-CT in fossil wood has long been a widely accepted hypothesis; however, in opaline CRBG specimens, the two silica polymorphs usually appear to have formed independently, e.g., woods in which cell walls are mineralized with opal-A but in which lumen contain opal-CT. Similarly, opal-CT has been inferred to sometimes transform to chalcedony; however, in CRBG, these mixed assemblages commonly resulted from multiple mineralization episodes.

Conifer Fossil Woods from the Late Jurassic–Early Cretaceous (Solari/Botucatú Formation) of the Paraje Tres Cerros (Corrientes Province), Northeast Argentina

“…However, as suggested by Suguio &Coimbra (1972), andPires et al (2011), and according to the descriptions and photographs (i.e., Mussa 1974) including the material described herein, all the specimens from the Solari/Botucatú Formation seem to be poorly preserved. This is probably due to one or more common factors during the start of the taphonomic process such as the oxidative process, high temperatures, dissolved-element concentrations, pH, or the places where the woods were buried (ephemeral streams, conglomerate channels, or coarse-grained sand sheets deposits) (Fengel, 1991;Mustoe, 2008Mustoe, , 2015Mustoe & Dillhoff, 2022).…”

A more southerly occurrence of Xenoxylon in North America: X. utahense Xie et Gee sp. nov. from the Upper Jurassic Morrison Formation in Utah, USA, and its paleobiogeographic and paleoclimatic significance

“…If the commonly assumed diagenetic silica maturation involving dissolution-precipitation processes in the cell walls proceeded in the studied specimen, it took place without a significant volumetric change that could otherwise severely damage plant tissue due to crystallization pressure (Liesegang and Gee, 2020). The direct precipitation of ordered silica phases, such as chalcedony, from diluted solutions has been invoked to explain a high degree of wood structural preservation and silica maturity (Liesegang et al, 2021;Mustoe and Dillhoff, 2022). To retain dimensional stability and organic matter distribution, episodes of diagenetic silica dissolution-precipitation in cell walls must proceed at the nano-to microscale, potentially via the formation of nanoscale dissolution channels in the cell wall.…”

“…When silica-rich fluid enters wood, silica monomers are expected to bond to the reactive surface groups of holocellulose on internal and external cell wall surfaces (Leo and Barghoorn, 1976;Liesegang and Gee, 2020). Cell lumina are usually unfilled at this early stage of fossilization (Mustoe and Dillhoff, 2022). Due to their hydrophobic character, the lignin-rich cell wall constituents (e.g., middle lamellae) initially remain largely unaffected (Liesegang and Gee, 2020).…”

“…Two major consequences result from ingress of silica-rich fluid into wood: degradation/transport of organic compounds and subsequent sealing of fluid-accessible pore space with newly-precipitated silica from fluids with variable dissolved silica concentration (e.g., Mustoe and Dillhoff, 2022). The higher the initial organic content, the more pore space is potentially available for fluid access and mass transport upon its degradation.…”

Викопна Деревина Міоцену Розточчя З «колекції Фосилій Рослинних І Тваринних Решток Палеонтологічного Музею Львівського Національного Університету Імені Івана Франка» – Наукового Об’єкта Національного Надбання

“…Силіфікація деревної тканини відбувалася синседиментаційно в мілководних затоках -з лужними водами, що сприяли розчиненню кремнеземуізольованих басейнах Паратетису, в кліматі, схожому на сучасний Середземноморський [5]. Процес мінералізації складний і відбувався стадійно, спочатку заміщенням деревини опалом, тоді халцедоном, і на кінець кварцом, який виповнює тріщини у деревині [7,8].…”