Deciphering Silicification Pathways of Fossil Forests: Case Studies from the Late Paleozoic of Central Europe

Abstract

The occurrence and formation of silicified wood from five late Paleozoic basins in Central Europe was investigated. Fossil wood from diverse geological settings was studied using field observations, taphonomic determinations as well as mineralogical analyses (polarizing microscopy, cathodoluminescence (CL) microscopy and spectroscopy). The results indicate that silicification is either a monophase or multiphase process under varying physico-chemical conditions. In particular, CL studies revealed complex processes of silica accumulation and crystallization. The CL characteristics of quartz phases in silicified wood can mostly be related to blue (390 and 440 nm), yellow (580 nm), and red (650 nm) emission bands, which may appear in different combinations and varying intensity ratios. Yellow CL is typical for initial silicification, reflecting quick precipitation under oxygen-deficient conditions caused by initial decay of the organic material. Blue CL is predominantly of secondary origin, resulting from replacement of precursor phases by a secondary hydrothermal quartz generation or subsequent silicification of wood. The red CL can be related to a lattice defect (non-bridging oxygen hole center—NBOHC).

Late Palaeozoic red beds elucidate fluvial architectures preserving large woody debris in the seasonal tropics of central Pangaea

“…Given that hematite occurrence is restricted to hydrothermally silicified wood (Fig. C, Trümper et al ., ), final silicification of the Kyffhäuser trunks is suggested here as being connected to this mineralization phase. Diagenetic or hydrothermal overprint of the sediment was additionally recorded by abundant corrosion and hydrothermally altered reaction rims of quartz grains and possibly intergranular dickite (Fig.…”

“…Silicification of the Kyffhäuser trunks started shortly after burial and took place as a two‐phase process (Trümper et al ., ). The petrifaction domains (Fig.…”

“…The petrifaction domains (Fig. D and G) represent the initial phase and display yellow cathodoluminescence resulting from conditions of rapid silica precipitation and oxygen depletion (Götze et al ., ; Trümper et al ., ). The wood surrounding the domains was affected later by silicification leading to advanced decomposition, wood displacement or inclusion by quartz crystals and compaction of the trunks (Figs G, H and H; Weiss, ).…”

“…Diagenetic or hydrothermal overprint of the sediment was additionally recorded by abundant corrosion and hydrothermally altered reaction rims of quartz grains and possibly intergranular dickite (Fig. C and D; Trümper et al ., ).…”

“…According to Trümper et al . (), these areas exhibit blue cathodoluminescence being typical of a hydrothermal origin (Götze et al ., ). Franzke et al .…”