Sea-level change following the Marinoan Snowball Earth deglaciation

Abstract:

Cap carbonates are broadly thought to represent marine deposition during the glacioeustatic sea-level rise following a ‘Snowball Earth’ deglaciation (Hoffman et al., 1998). However, a few syn-deglacial Marinoan stratigraphic successions suggest that regional regression punctuated the deglacial transgression (Hoffman and Macdonald, 2010; Rose and Maloof, 2013). A number of questions about the sign and magnitude of post-Snowball sea-level change arise from stratigraphic studies of Neoproterozoic glaciations. For instance, can a local geological inference of the magnitude of transgression provide a robust estimate of the eustatic (globally averaged) sea-level rise associated with the deglaciation? If not, what is the range of geographic variability in regional sea-level change driven by deglaciation? Is this variability a strong function of the duration of the deglaciation? What circumstances could lead to a regional regression interrupting a glacioeustatic transgression?

In this talk, we explore the spatial and temporal variability of post-Marinoan Snowball sea-level change using a gravitationally self-consistent theory that accounts for the gravitational, deformational, and rotational perturbations to sea level on a viscoelastic Earth model. We apply the theory to model a Marinoan Snowball deglaciation across a generalized Ediacaran paleogeography with a synthetic ice sheet distribution. We demonstrate that the sea-level change following a synchronous and rapid (2 kyr) collapse of Snowball ice cover would exhibit significant geographic variability, producing local sea-level records characterized by syn-deglacial sea-level rise, fall and stillstand. Both asynchronous melting and longer-duration deglaciation scenarios (5 – 200 kyr) introduce additional complexity into the predicted timing and geometry of the computed post-glacial sea-level change; these complexities include zones of syn-deglacial regression followed by transgression and the possibility of major transgression (and, thus, deposition) that is not limited to the deglaciation phase. These results suggest that sea-level change recorded by strata capping Snowball glaciogenic units could record a far more complicated trajectory than simple transgression.