2014 GSA Annual Meeting in Vancouver, British Columbia (19–22 October 2014)

Paper No. 256-4
Presentation Time: 1:45 PM

SEA-LEVEL CHANGE FOLLOWING THE MARINOAN SNOWBALL EARTH DEGLACIATION


CREVELING, Jessica R., Geological and Planetary Sciences, California Institute of Technology, 1200 E. California Blvd, Pasadena, CA 91125 and MITROVICA, Jerry X., Department of Earth and Planetary Sciences, Harvard University, 20 Oxford Street, Cambridge, MA 02138

Marinoan cap carbonates are thought to represent deposition during the glacioeustatic sea-level rise associated with a ‘Snowball Earth’ deglaciation (Hoffman et al., 1998). However, facies associations within some syn-deglacial Marinoan successions suggest that regional regression punctuated these transgressive sequence tracts (Hoffman and Macdonald, 2010; Rose and Maloof, 2013). A number of questions arise from stratigraphic studies that highlight the need to couple sequence stratigraphic observations with numerical models of post-Snowball sea-level change. For instance, what is the plausible range of geographic variability in regional sea-level change driven by the deglaciation? Is this geographic variability a strong function of the duration of the deglaciation? Can a local geological inference of the magnitude of transgression provide a robust estimate of the globally averaged (eustatic) sea-level rise associated with the deglaciation? What circumstances could lead to a pronounced regional regression during glacioeustatic transgression?

In this talk, we explore the spatial and temporal variability of sea-level change during Snowball deglaciation and its aftermath using a gravitationally self-consistent theory that accounts for the deformational, gravitational and rotational perturbations to sea level on a viscoelastic Earth model. We apply the theory to the case of a model Marinoan Snowball deglaciation on a generalized Ediacaran paleogeography with a synthetic continental ice-sheet distribution. We demonstrate that the sea-level change following a rapid (2 kyr), synchronous collapse of Snowball ice cover would exhibit significant geographic variability, including local sea-level records characterized by syn-deglacial sea-level fall or stillstand. Moreover, asynchronous melting and longer-duration deglaciation phases (5 – 200 kyr) introduce further complexity into the predicted timing and geometry of the computed sea-level change, including zones of syn-deglacial regression followed by transgression and the possibility of deposition that is not limited to the deglaciation phase. These results suggest that sea-level change recorded by strata capping Snowball glaciogenic units may reflect a far more complicated trajectory than previously thought.