Late Neogene changes in North America and Antarctica absolute plate motions inferred from the Mid‐Atlantic and Southwest Indian Ridges spreading histories

Abstract

Reconstructions of absolute plate motions underpin our understanding of the plate torque balance, but are challenging due to difficulties in inferring well‐dated rates and directions of plate movements from hot spot tracks. Useful information about plate dynamics can be inferred from rapid absolute plate motion changes, as these are linked only to the torque(s) that changed. Here we infer late Neogene changes in the absolute motions of North America and possibly Antarctica from changes in the easier‐to‐determine relative plate motions recorded along the Arctic, northern Mid‐Atlantic and Southwest Indian Ridges. We show that Eurasia/North America and Nubia/North America motions changed by the same amount between 8 and 5 Ma, as may have Nubia/Antarctica and Somalia/Antarctica plate motions. By considering additional, independent constraints on Somalia/India plate motion, we argue that a scenario in which North America and Antarctica absolute motions changed is the simplest one that explains the observed changes in relative motions. We speculate that these changes are linked to the late Neogene dynamics of the Pacific plate.

The Geological Evolution of the Aden‐Owen‐Carlsberg Triple Junction (NW Indian Ocean) Since the Late Miocene

“…The most commonly invoked driver is a change of the gravitational potential energy gradient related to the growth of the Himalaya‐Tibet (Molnar & Stock, ). Alternatively, Iaffaldano and DeMets () proposed that this kinematic change could correspond to a global plate reorganization event driven by changes in the dynamics of the Pacific plate.…”

Late Miocene Pacific plate kinematic change explained with coupled global models of mantle and lithosphere dynamics

“…Since the latter study does not provide covariance matrices, we assume these to be diagonal and equal to 10% of the angular velocity, squared (in the supplement, we present the case where we assume covariances to be equal to 20% of the angular velocity). Iaffaldano and DeMets [] recently analyzed reconstructions of spreading of the Southwest Indian Ridge and argued for a change in the AN absolute motion between 8 and 5 Ma that is not resolved in the study of Torsvik et al []. The data available to Iaffaldano and DeMets [] did not permit either ruling out or resolving changes in the absolute kinematics of AN between 20 and 15 Ma.…”

“…Iaffaldano and DeMets [] recently analyzed reconstructions of spreading of the Southwest Indian Ridge and argued for a change in the AN absolute motion between 8 and 5 Ma that is not resolved in the study of Torsvik et al []. The data available to Iaffaldano and DeMets [] did not permit either ruling out or resolving changes in the absolute kinematics of AN between 20 and 15 Ma. For this reason, we reconstruct the PA absolute motion back to 15 Ma.…”

“…We combine the results from Torsvik et al [], Iaffaldano and DeMets [], and DeMets and Merkouriev [] as follows. First, we construct a pattern for the AN absolute motion, where the Euler vector (i) is constant between present day and 5 Ma; (ii) varies linearly between 5 and 8 Ma, according to the change estimated by Iaffaldano and DeMets []; and (iii) remains constant and equal to the 8 Ma value from 8 to 15 Ma. Such a temporal pattern can be fully determined once the AN Euler vector for the stage from present day to 5 Ma is known.…”

“…In fact, DeMets and Merkouriev [2016] revisited the PA/AN relative motion reconstruction of Croon et al [2008] to obtain a noise-reduced time series of stage Euler poles and angular velocities. Furthermore, Iaffaldano and DeMets [2016] explored the histories of spreading of the Atlantic and Southwest Indian Ridges to argue that the AN kinematics likely featured a change between 8 and 5 Ma. These new inferences can be used to reassess the PA absolute kinematics.…”