Investigation of a Modern Incipient Stromatolite from Obsidian Pool Prime, Yellowstone National Park: Implications for Early Lithification in the Formation of Light-Dark Stromatolite Laminae
Abstract
Stromatolites have been defined multiple ways, but the presence of lamination is common to all definitions. Despite this commonality, the origin of the lamination in many ancient stromatolites remains vague. Lamination styles vary, but sub-mm light-dark couplets are common in many ancient stromatolites. Here, we investigate an actively forming incipient stromatolite from Obsidian Pool Prime (OPP), a hot spring in Yellowstone National Park, to better understand the formation of light-dark couplets similar to many ancient stromatolites in texture and structure. In the OPP stromatolites, a dense network of layer-parallel bundles of cyanobacterial filaments (a dark layer) is followed by an open network of layer-perpendicular or random filaments (a light layer) that reflect a diurnal cycle in the leading edge of the microbial mat that coats the stromatolite's surface. Silica crust encases the cyanobacterial filaments maintaining the integrity of the lamination. Bubbles formed via oxygenic photosynthesis are commonly trapped within the light layers, indicating that lithification occurs rapidly before the bubbles can collapse. The filamentous, non-heterocystous stromatoite-building cyanobacterium from OPP is most closely related to a stromatolite-building cyanobacterium from a hot spring in Japan. Once built, "tenants" from multiple microbial phyla move into the structure, mixing and mingling to produce a complicated integrated biogeochemical signal that may be difficult to untangle in ancient examples. While the cyanobacterial response to the diurnal cycle has been previously implicated in the formation of light-dark couplets, the OPP example highlights the importance of early lithification in maintaining the fabric. Thus, the presence of light-dark couplets and bubble structures may indicate very early lithification and therefore a certain degree of mineral saturation in the ancient ocean or other aquatic system, and that bubble structures, if present, may be evidence for oxygenic photosynthesis. Other lamination hypotheses suggest that lithification is driven by sulfate reduction within a stratified microbial mat—a possibility in some stromatolites, but the lithification engine must move deeper in the mat where the formation of fine light-dark couplets becomes more problematic.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFM.B24B..06C
- Keywords:
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- 0414 Biogeochemical cycles;
- processes;
- and modeling;
- BIOGEOSCIENCESDE: 0419 Biomineralization;
- BIOGEOSCIENCESDE: 0424 Biosignatures and proxies;
- BIOGEOSCIENCESDE: 0444 Evolutionary geobiology;
- BIOGEOSCIENCES