Reassessing classic evidence for warm-based Cryogenian ice on the western Laurentian margin: The striated pavement of the Mineral Fork Formation, USA

Determining the extent and nature of ancient glacial deposits is fundamental to understanding Earth's climate in the Cryogenian Period. Although the detailed study of sedimentary facies has allowed significant insights, it typically fails to produce high confidence interpretations for the past position of grounded ice, its thermal regime and flow direction, which are of fundamental importance to any glaciological reconstruction. When correctly identified, Cryogenian subglacially striated surfaces (pavements) unequivocally indicate grounded ice, a warm-based thermal regime and flow direction. However, they are globally rare and open to misinterpretation. Despite a discontinuous belt of Cryogenian strata, stretching thousands of kilometres from Alaska to California, the only purported Cryogenian pavements from the North American continent or the western margin of the Laurentian palaeocontinent occur in the Big Cottonwood Canyon area, Utah. We critically reappraise the only uncontested pavement from this area, presenting a detailed description derived from new high resolution photogrammetry and traditional field observations. These suggest that the purported pavement is unlikely to be a Cryogenian feature, but is instead a recent erosional phenomenon consistent with other structurally controlled features within the surrounding modern landscape. Our reinterpretation questions whether grounded Cryogenian ice reached the Utah - Idaho region and whether the lower reaches of the Mineral Fork Formation record glacially influenced deposition or non-glacial, rift-related sedimentation that transitions upwards into glacial conditions.

Automated summary

This passage discusses the importance of ancient glacial deposits in understanding Earth's climate during the Cryogenian Period, as well as the challenges in determining the past positions of grounded ice, its thermal regime, and flow direction. The study found that Cryogenian subglacially striated surfaces are globally rare but are crucial indicators of the presence of ice and thermal regime.