Dynamic glaciation during a Neoproterozoic “Snowball Earth” event

The Neoproterozoic Wilsonbreen Formation in the Svalbard archipelago records some of the best exposed and best preserved examples of Neoproterozoic glaciation in the North Atlantic region. The Formation has been interpreted in terms of a Snowball Earth Model which postulates complete or near freezing of the Earth’s surface. Under these conditions, a distinctive advance-melt back cycle would be expected. More recently, new observations of current glacial environments and the development of new techniques have enhanced our understanding of glacial sedimentation. Therefore, excellent opportunities exist for these deposits to be re-examined and snowball earth hypothesis tested.

Lithofacies of the Wilsonbreen Formation can be grouped into distinct glacial-depositional environments (glacioaqueous and subglacial) as well as non-glacial (terrestrial, lacustrine and fluvial). Palaeo-iceflow, deduced through clast fabric analysis and the novel application of anisotropy of magnetic susceptibility (AMS) indicate that transport was dominantly N-S to NW-SE oriented during both subglacial and glaciomarine deposition. This suggests deposition in a roughly N-S orientated basin with glacier flow dominantly to the N or NW.

Our observations and results reveal a complex interchange of depositional environments ranging from non-glacial to subglacial. This architecture shares many characteristics with ice marginal locations in the modern day Polar Regions which show similar variability related to Holocene climatic fluctuations. This style of deposition could provide some challenges if a classic ‘Snowball Earth’ model was envisaged as, in contrast to a single advance-meltback cycle, the Wilsonbreen Formation is composed of a series of oscillations between different depositional regimes in different environments. This evidence suggest that whilst the ‘Snowball Earth’ hypothesis provides insight into how extreme climate perturbations can occur, a simple advance-melt back cycle cannot explain the variability and dynamism exhibited in the Neoproterozoic glacial deposits of Svalbard and instead a more complex story is evident.