Organic Free Radicals in Precambrian and Paleozoic Rocks: Origin and Significance

Abstract

Fourteen Precambrian kerogens including seven isolated from stromatolites were studied by electron spin resonance (ESR). Organic free radicals were detected in only three of these kerogens: those from the Gunflint and Bitter Springs cherts and the Nonesuch shale. All three rocks are known to contain organically preserved microfossils. Comparative studies were conducted on the kerogens of eight fossiliferous Paleozoic rocks and a Jurassic anthracite. Careful measurements were made of g-values, line-widths, line-shapes, and integrated intensities of the observed signals. The kerogen radicals are believed to be polyaromatic structures with unpaired electrons stabilized as π electrons. The marked similarity of the ESR spectral parameters of the free radicals in Precambrian and Paleozoic kerogens and the Jurassic Vrska Cuka anthracite serves to strenghten the view that these radicals are relics of early biochemical processes.