Rapid absolute plate motion changes inferred from high-resolution relative spreading reconstructions: A case study focusing on the South America plate and its Atlantic/Pacific neighbors

Abstract

The reconstruction of past plate motions relative to a deemed–to–be–fixed hotspot reference frame relies on the sparse occurrence of intraplate volcanism. Consequently, this absolute reference frame often features a temporal resolution that exceeds the rapid kinematic changes observed in plate–to–plate spreading reconstructions, changes recently shown to occur within less than 5 Ma. In this work we put forward an alternative method based on the study of high–resolution relative plate motion data sets. By studying time periods featuring a relatively high probability of plate motion change across multiple spreading ridges, we are able to identify and quantify (likely) changes in absolute plate motion. Specifically, we implement such approach and provide well–defined estimates for the absolute plate motion changes of South America and neighboring plates Nubia, Antarctica, Somalia, North America and Pacific. We find that kinematic changes for all these plates occur between 9 and 5 Ma. For South America, we identify a change also between 14 and 10 Ma. Lastly, we estimate the torque–variations required upon these plates to generate the inferred kinematic changes, which we find to be between ∼5⋅1023 and ∼20⋅1024 N ⋅ m.