ESTIMATING VERTICAL SURFACE MOTIONS THROUGH TIME USING PALEOGEOGRAPHIES

The topography of the Earth’s surface is subject to constant change due to tectonic, surface processes and mantle-driven vertical motions. However, determining the individual contributions of different mechanisms for vertical motion change through geological history from the sedimentary record is extremely difficult due to a missing absolute reference base level.

We reverse-engineered data from independent sets of paleogeographic maps using the GPlates software to construct a set of time-dependent, global paleo-shorelines from the Jurassic to present day. We compute the amount of change in the lateral shoreline position between individual timesteps to derive spatio-temporal patterns of relative subsidence and uplift. Using stable cratonic blocks as our geographic base reference, we derive the tilting of these blocks and compute hypsometric curves through the amount of flooding. For our analysis we utilize a global, self-consistent set of dynamic plate polygons, sediment thickness data, and a time-dependent collection of rift basins to discriminate between areas undergoing lithospheric deformation and stable continental regions. A geospatial proximity analysis is performed to determine the spatio-temporal relationship to adjacent plate boundary types.

Based on the amount of change, we identify areas which undergo significant changes and examine these at a higher resolution using additional data (e.g. well data, outcrop, isopach maps) to determine the causes of these changes. We then attempt to quantitatively link our results to a volumetric analysis of subduction history based on global plate kinematic models to improve our understanding of spatio-temporal variations in mantle-driven dynamic topography.