Neoproterozoic snowball Earth under scrutiny: Evidence from the Fiq glaciation of Oman

The Fiq Member of the Ghadir Manqil Formation, Huqf Supergroup, Oman, is composed of ∼1.5 km of glacial rainout diamictites, mass-flow deposits, turbiditic sandstones, and slope and shelf sandstones and siltstones, overlain by a classic <10-m-thick transgressive cap dolostone. Paleocurrents, facies distribution, and subsurface imagery show that the Fiq Member was deposited in a series of extensional half-grabens and grabens. Facies associations represent proximal glaciomarine, distal glaciomarine, nonglacial sediment gravity flow, and nonglacial shallow-marine siliciclastic depositional environments and processes. The member is divided into seven units that can be correlated across the rift basin. Although the facies mosaic is complex, cycles of relative sea-level change, most likely driven by glacio-eustasy, show that glacial advance and retreat during the glacial epoch was strongly pulsed. Only the final (youngest) diamictite is overlain by a well-developed cap carbonate. It is unlikely that there was any prolonged and substantial shutdown of the hydrologic cycle during deposition of the Fiq Member. On the basis of sedimentological and stratigraphic data, the Neoproterozoic glacials of Arabia were more like the familiar oscillatory glaciations of the Pleistocene than those required by the snowball Earth hypothesis.