New U-Pb CA-ID TIMS zircon ages implicate the Franklin LIP as the proximal trigger for the Sturtian Snowball Earth event

Abstract

The Franklin igneous event (ca. 718 Ma) emplaced basalts and mafic intrusions across Arctic Laurentia just prior to the onset of the ca. 717–661 Ma Sturtian Snowball Earth event. Given the close association in time between these two events, it has been widely argued that the Franklin event contributed to the initiation of global glaciation. However, a lack of accurate high-precision geochronology has hampered establishing the timeframe of Franklin magmatism and discerning its precise temporal and possible causative relationship to glaciation. Here we present new high-precision U-Pb CA-ID TIMS zircon ages for two dykes and two sills from Baffin Island, Canada, and Avannaata, northwestern Greenland, related to the Franklin event. Combined with field relationships showing that the dykes crosscut the sills, these four dates indicate magmatic activity over 1.10±0.74 Myr at ca. 718 Ma, immediately prior to Sturtian glaciation, which we estimate to have initiated at 717.19 +0.26/−0.33 Ma. Our results are consistent with recent high precision U-Pb CA-ID TIMS age estimates for the Franklin magmatic activity in the central and western parts of the province. Combining our new dates with the other high precision CA-ID-TIMS ages yields a duration for the Franklin event of 2.14±0.75 Myr which is shorter than the previous estimates but somewhat longer than that for typical Phanerozoic large igneous events.