100-8 Tava: U-Pb Dating of Cryogenian Snowball Earth Meltwater Events in Colorado

Session: Snowballs, Unconformities, BIFs and Beyond: Navigating the Neoproterozoic Rock and Climate Records Using Geochronology

Presenting Author:

Liam Courtney-Davies

Authors:

Courtney-Davies, Liam¹, Flowers, Rebecca Marie², Siddoway, Christine³, Tasistro-Hart, Adrian⁴, Macdonald, Francis A.⁵

(1) Department of Geological Sciences, The University of Colorado Boulder, Boulder, Colorado, USA; Department of Earth and Environmental Sciences, San Diego State University, San Diego, California, USA, (2) Department of Geological Sciences, University of Colorado Boulder, Boulder, Colorado, USA, (3) Department of Geology, Colorado College, Colorado Spgs, Colorado, USA, (4) Department of Earth and Planetary Sciences, The University of California, Berkeley, Berkeley, California, USA, (5) Department of Earth and Planetary Science, UC Berkeley, Berkeley, California, USA,

Abstract:

Terrestrial records of the Cryogenian (720-635 Ma) ice sheets are rare, and until recently were unknown from low paleolatitudes within interior continental settings.  Here, we document a terrestrial Sturtian glacial record in the Colorado Front Range referred to as ‘Tava’, after the ancestral Ute name for Pikes Peak where many outcrops are found. Tava is composed of meter scale sandstone/quartzite dikes (injectites) and ridges hundreds of meters in length, which preserve features characteristic of fluidization and deformation in a subglacial environment. We use in-situ hematite U-Pb geochronology to date injectite formation via veinlet age bracketing, providing constraints on glacial meltwater events associated with rifting and deglaciation (~690-660 Ma). The chemically weathered crystalline rock associated with the Tava dikes lacks evidence of mechanical abrasion and glacial scouring, suggesting that erosion at the adjacent Great Unconformity predates the Sturtian glaciation.

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

doi: 10.1130/abs/2025AM-6643

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