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Amorphous organic matter: microbes as a new clue for palaeoenvironmental reconstructions

Type of publication Peer-reviewed
Publikationsform Original article (peer-reviewed)
Publication date 2011
Author Pacton M. Gorin G. Vasconcelos C.,
Project Using New Geochemical and Nanotechnological Approach to Study Biomineralization in Microbiolites
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Original article (peer-reviewed)

Journal Review of Palaeobotany and Palynology
Volume (Issue) 166
Page(s) 253 - 267
Title of proceedings Review of Palaeobotany and Palynology


The origin of microscopically-amorphous organic matter (AOM) is problematic. It has been extensively studied because it is the dominant kerogen constituent in petroleum source rocks. Although microbes are widespread in natural environments, they are commonly associated only with marine AOM derived from phytoplankton. In this study, we have selected terrestrial and marine samples with various microbial inputs in order to decipher the role of microbes in AOM composition. A specially-tailored laboratory device has been used for determining the effect of oxygen- and light-depleted conditions on recent microbial mats for a duration of three years. This experiment aimed at reproducing conditions existing in nature at the water– sediment interface. This research has permitted the characterization of AOM according to its biological origin. Two different types of AOM have been observed, i.e., gelified and granular types. They are related respectively to microbial reworking of terrestrial fragments and primary microbial populations. Moreover, bacterial bodies constitute the ubiquitous, strongly !uorescent material, whereas extracellular polymeric substances (EPS) surround bacteria and show a weaker !uorescence. Consequently, this study on modern OM has unravelled the amorphization process of specific organic particles leading to AOM classically encountered in fossil sediments. This has considerable implications for palaeoenvironmental reconstructions associated with the origin and preservation of OM.