Massive Volcanism May Have Foreshortened the Marinoan Snowball Earth

Abstract

The Cryogenian Period (717–635 Ma) experienced two low‐latitude “snowball Earth” glaciations, the Sturtian and the Marinoan of contrasting 57 and <16 Myr durations, respectively. A lack of reliable age controls on extensional tectonics and associated magmatic rocks during the Marinoan has hampered an understanding of the deglaciation. Furthermore, although deglaciation is generally assumed to have occurred once ongoing magmatism accumulated enough atmospheric CO2, as suggested by cap carbonates, specific geologic evidence linking volcanic events with deglaciation are lacking. Here, we present high‐precision zircon geochronology with chemical abrasion‐isotope‐dilution isotope ratio mass spectrometry that indicates an extensive and thick sequence of rift‐related magmatic rocks in South Qinling, Central China, erupted 2–6 Myr before the termination of the Marinoan. Climate modeling proposes a scenario explaining why the Marinoan was the shorter snowball and how volcanism may have driven the deglaciation.

Zircon U-Pb-Hf Isotopes and Whole-Rock Geochemistry of the “Kulumudi Formation” from the Laofengkou Area (West Junggar): Implications of the Construction of a Juvenile Arc in the Junggar–Balkhash Ocean

“…Zircon U-Pb and Lu-Hf Isotope Analysis 4.1.1. Zircon U-Pb Ages Zircons from the lithic crystal tuff (19TL-82) were mainly euhedral and prismatic with lengths of 50-150 µm and showed obvious oscillatory zoning (Figure 4a), which is typical of tuff origin [65]. Based on REE patterns (Table S2), zircons shown by the solid lines exhibited positive Ce and slightly negative Eu anomalies, which is typical of igneous origin (Figure 5a).…”

Resilience of Snowball Earth to Stochastic Events

“…However, the time required to accumulate sufficient CO 2 to trigger melting (4–30 Myr, Hoffman et al., 1998) is too long to account for the short Marinoan glaciation (Rooney et al., 2015). Suggested alternatives include impact events (Kring, 2003) and massive volcanic eruptions (Lan et al., 2022), which we hereafter refer to as stochastic events due to the nature of their occurrences. However, quantitative estimates of climate after stochastic events remain relatively unexplored.…”