GEOCHEMICAL CHARACTERIZATION OF 1.1 GA MICROBIAL MATS IN EARLY DIAGENETIC CHERT OF THE ANGMAAT FORMATION, BYLOT SUPERGROUP NORTHERN BAFFIN ISLAND

Peritidal chert deposits are common in Meso- and Neoproterozoic carbonate strata. These chert deposits commonly preserve primary mineral and organic components, some of which include exceptional microbial morphologies. Exceptional morphological preservation of microorganisms via early diagenetic silicification is used to gain insight into early ecosystems. Here we use exceptional morphological preservation to infer both the timing of silicification and the chemistry of Earth’s early environments. We also explore the extent to which taphonomic processes affect both the morphology and geochemistry of preserved organic matter.

Chert deposits within the ~1.1 Ga Angmaat Formation, Bylot Supergroup, record late Mesoproterozoic carbonate strata deposited within an intertidal to supratidal microbial flat. Early diagenetic silicification records microbial growth and decomposition across a range of environments, which contain discrete filamentous and coccoidal mat types (Knoll et al., 2013). Various taphonomic states of microbial mat fabrics and individual microbes are preserved. Mat taphonomy ranges from mats that are well-preserved and are inferred to have been silicified during active growth of the mat, to samples that show compaction and morphological degradation that are inferred to represent silicification during mat decomposition.

The presence of n-alkanes, hopanes, and steranes in the initial characterization of the organic matter preserved in the chert of the Angmaat Formation suggested that the organic matter was thermally immature and from a hypersaline environment. It also suggests that samples in which the morphology is exquisitely preserved may also have a higher potential for molecular preservation. To rule out contamination as the source of the steranes, a clean sample prep method was established. Here we present the characterization of the geochemistry preserved in organic matter from samples collected during a recent field season using the new sample prep method.