Plate tectonics and net lithosphere rotation over the past 150 My

Abstract

We have developed an improved model of global digital palaeo-plate boundaries and plate motion to describe the distribution and history of plates since the Late Jurassic. From this history we computed net lithospheric rotation (NR) through time confirming the so-called westward drift, but only for the past 30 Myr. The NR has significantly smaller magnitudes (0.13°/My, past 5 My) than for some other plate models; it averages to 0.11 ± 0.03°/My for the past 50 My with a small but systematic increase toward the present. The westward drift, seen only for the past 30 My, is attributed to the increased dominance of a steadily growing and accelerating Pacific plate. NR shows peaks with time but only an Early Tertiary peak of 0.33°/My (when the Indian plate was undergoing the largest known acceleration/deceleration) can be interpreted with some confidence. We find a linear decreasing trend in net rotation over the past 150 My, but attribute this trend to increasing reconstruction uncertainties back in time, as subduction consumed more than half of the oceanic crust since the Jurassic. After removing a linear time-trend, we find a NR average of about 0.12°/My for the past 150 My.