Biogenic influence on geological dendrites

Ascertain whether dendritic manganese- and iron-oxide mineral patterns in geological settings are entirely abiotic precipitates or whether some are influenced or produced by biological processes, and establish diagnostic criteria and tests that can distinguish between abiotic dendrites and biologically mediated deposits.

Background

Branching structures are widespread in geology, including manganese and iron oxide dendrites that often form on rock surfaces and within fractures. Classical models treat these patterns as abiotic precipitates formed by oxidation and diffusion-limited aggregation.

However, microbes can strongly catalyze Mn and Fe oxidation, and modern and fossil Frutexites-like structures suggest microbial mediation in some dendritic deposits. The review highlights the difficulty of disentangling abiotic from biotic contributions and calls attention to the uncertainty regarding the biogenicity of mineral dendrites.