100-3 Stable Sedimentary Dynamics of the Zerrissene Deep-Sea Fan Across the Marinoan Snowball Earth

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

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Abstract:

The Zerrissene deep-sea fan in Namibia is a Cryogenian-Ediacaran turbidite succession that formed between the Congo paleocontinent and an arc terrane to the west. Dropstones in the upper Brak River Formation of the Zerrissene Group evidence glacigenic sedimentation correlated with the Marinoan Snowball Earth, providing a rare deep sea record of Snowball sedimentation. We identify a traceable horizon of the lowest stratigraphic dropstones, which we interpret to record Marinoan onset in the deep water setting. The youngest zircon grain in a preglacial detrital sample 155 m below this horizon yields a concordant CA-ID-TIMS date of ca. 642 Ma, which is consistent with recent work suggesting Marinoan onset ca. 639 Ma. The stratigraphic architecture and sediment provenance of the Brak River Formation persists unmodified by the Marinoan glaciation, changing only at the contact with the overlying Gemsbok River Formation, which marks an influx of carbonate and the disappearance of dropstones. The insensitivity of deep-sea sediment provenance to Snowball Earth glaciation conflicts with the hypothesis of expansive syn-Snowball continental denudation. Instead, the continuity of deep-sea sediment routing is consistent with a stable Snowball ice sheet volumes.

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

doi: 10.1130/abs/2025AM-6384

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