Observations of silicified stromatolites from the late Cambrian-early Ordovician of Adairsville, Georgia

This study describes and analyzes silicified stromatolite samples collected near Adairsville, Georgia, from Cambrian–Ordovician system rocks likely belonging to the Copper Ridge Dolomite of the Knox Group. Using the classification system outlined by Grey and Awramik (2020), the stromatolites were systematically described at the macro-, meso-, and microscales. The samples display two primary mesostructural morphologies—branched-bifurcate and layered-linked columnar forms—with non-couplet lamination, smooth to wavy laminae, moderate to high synoptic relief, and alternating microlaminae textures. Unlike previous studies of stromatolites from nearby Murray County, Georgia the stromatolites samples from Adairsville, Georgia preserve well-defined mesoscale and microscale lamination visible in thin section under plane polarized light (PPL), suggesting better early silicification and reduced diagenetic overprinting. Dolomite rhombs, chalcedony veins, and voids document a complex multi-phase diagenetic history involving early dolomitization and subsequent silica replacement. Although no clearly recognizable microfossils were found, the preserved laminar fabrics, curious brown spherical features in some samples, and consistent microbialite structures support a biological origin linked to microbial mat growth in a shallow subtidal to intertidal environment. This study contributes to a broader effort to document stromatolite-bearing formations in northwest Georgia and highlights the need for further petrographic, Scanning Electron Microscopy with Energy Dispersive X-Ray Spectroscopy, and fluid inclusion studies to better constrain the diagenetic pathways and microbial signatures preserved within the Knox Group of northwest, Georgia.