A proposed origin for fossilized Pennsylvanian plant cuticles by pyrite oxidation (Sydney Coalfield, Nova Scotia, Canada)

Abstract

Fossilized cuticles, though rare in the roof rocks of coal seam in the younger part of the Pennsylvanian Sydney Coalfield, Nova Scotia, represent nearly all of the major plant groups. Selected for investigation, by methods of Fourier transform infrared spectroscopy (FTIR) and elemental analysis, are fossilized cuticles (FCs) and cuticles extracted from compressions by Schulze's process (CCs) of Alethopteris ambigua. These investigations are supplemented by FTIR analysis of FCs and CCs of Cordaites principalis, and a cuticle-fossilized medullosalean(?) axis. The purpose of this study is threefold: (1) to try to determine biochemical discriminators between FCs and CCs of the same species using semi-quantitative FTIR techniques; (2) to assess the effects chemical treatments have, particularly Schulze's process, on functional groups; and most importantly (3) to study the primary origin of FCs. Results are equivocal in respect to (1); (2) after Schulze's treatment aliphatic moieties tend to be reduced relative to oxygenated groups, and some aliphatic chains may be shortened; and (3) a primary chemical model is proposed. The model is based on a variety of geological observations, including stratal distribution, clay and pyrite mineralogies associated with FCs and compressions, and regional geological structure. The model presupposes compression-cuticle fossilization under anoxic conditions for late authigenic deposition of sub-micron-sized pyrite on the compressions. Rock joints subsequently provided conduits for oxygen-enriched ground-water circulation to initiate in situ pyritic oxidation that produced sulfuric acid for macerating compressions, with resultant loss of vitrinite, but with preservation of cuticles as FCs. The timing of the process remains undetermined, though it is assumed to be late to post-diagenetic. Although FCs represent a pathway of organic matter transformation (pomd) distinct from other plant-fossilization processes, global applicability of the chemical models remains to be tested. CCs and FCs are inferred endpoints on a spectrum of pomd which complicates assessing origin of in-between transformations (partially macerated cuticles). FCs index highly acidic levels that existed locally in the roof rocks.•

Fourier transform infrared characterization of the Middle Devonian non‐vascular plant Spongiophyton

“…The high‐wavenumber region ranges from 3000 to 2800 cm −1 (Al = aliphatic C–H stretching). Functional groups of this region are considered as being more influenced by early diagenetic oxidation than the low‐wavenumber region (Berner ; Zodrow and Mastalerz ; Zodrow et al . ).…”

“…) were broader bands of weak intensity. These differences among Spongiophyton species can be attributed to the high degree of oxidation of S. nanum and S. minutissimum or to the presence of additional organic components in the original material (Berner ; Zodrow and Mastalerz ; Zodrow et al . ).…”

“…All these ratios could also be used for comparative purposes, providing valuable information on both diagenetic changes and the chemical composition of the fossil remains (D'Angelo ; Zodrow and Mastalerz , ).…”

“…; Guo and Bustin ; Zodrow et al . , , , , , b ; Zodrow and Mastalerz , , ; Marshall et al . ; Psěnička et al .…”

Sterile Foliage of Fertile Sydneia Manleyi and Synangial Chemistry (Eusporangiate Fern, Late Asturian, Canada): A New Subfamily Sydneideae

“…2), and a detailed view of light-colored areas whose true color is darkish amber, which in turn is correlated to the variable degree of natural maceration/coalification (chemical composition variability; see D 'Angelo et al, 2012;Zodrow and D'Angelo, 2013, fig 2). This is interpreted as typical effects as a result of incipient natural maceration, and is regarded as an early-stage fossilized-cuticle (Zodrow and Mastalerz, 2009); hence the much shorter maceration time for the sterile foliage.…”