141-6 Spatially Resolved Deconvolution of Texture Formation and Initial Diagenetic Mechanisms in Carbonate Dendrolitic Microbialites

Session: New Advances in Geobiology

Presenting Author:

Victoria Cassady

Authors:

Cassady, Victoria¹, Petryshyn, Victoria², Bernhard, Joan M.³, Celestian, Aaron⁴, Liu, Mengshi⁵, McCormack, Ariel⁶, Perez, Kelsey⁷, Berelson, Will⁸, Bottjer, David J.⁹, Corsetti, Frank¹⁰

Abstract:

Microbialites–macroscopic organosedimentary structures (rocks) formed by interactions between microbial communities and detrital/chemical sediments —represent some of the oldest evidence of life on Earth and remain a target for extraterrestrial investigation. Microbialites are recognizable as macroscopic manifestations of microbial activity because of their textures, consisting of visible remnants of primary mineralogy and cemented channel architecture. Despite the importance of texture, the origin, evolution, and dependence of texture on in situ localization of microbial consortia is unknown. Recently, we characterized texture in incipient CaCO₃ microbialites from Little Hot Creek (LHC), a geothermal system in eastern California, where rapidly-lithifying microbial mats have a dendrolitic (shrub-like) texture strikingly similar to certain ancient microbialites. We used fluorescently labelled embedded coring (FLEC) to preserve internal textures of minerals, microbial biofabrics, and channel architecture in thin section. This allowed for direct comparison to thin sections of ancient microbialite counterparts, addressing a methodological gap between modern and ancient structures. In a new series of experiments, we combined FLEC with incubation in an H¹³CO₃ spike solution and used Raman spectroscopy to map incorporation of ¹³C into newly formed calcium carbonate to show where calcite precipitated in relation to microbial biofabrics. We show how specific microbial consortia-mineral surface relationships create micro-environments favoring authigenic CaCO₃ precipitation, and how meso-scale microbialite form may emerge from these spatial relationships. Lastly, we examine the role of endolithic microboring as a micritizing force and initial diagenetic step in carbonate microbialites immediately following mineral precipitation, and its potential involvement in producing micrite in ancient microbialites.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-9415

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