Apparent and True Polar Wander and the Geometry of the Geomagnetic Field in the Last 200 Million Years

We have constructed new synthetic Apparent Polar Wander Paths for the African, Antarctic, Australian, European, Greenland, Indian, and North and South American plates over the last 200 Ma. A total number of 242 independent data has been retained, with a good distribution of site longitudes. Updated kinematic models allowed us to relate the paleomagnetic data of all plates over the entire period of interest and to construct a master synthetic APWP, using the data of all plates transferred onto a single one and averaging them within 10 and 20 Ma sliding windows. Average poles are only moderately far-sided, consistent with a persistent quadrupole moment on the order of 3% of the dipole over the last 200 Ma). The overall shape of the Eurasian and North American APWPs between 150 and 50 Ma confirms the existence of a loop, though somewhat smaller and more complex than previously recognized. The timing of the so-called Cretaceous standstill appears to be slightly later than previously thought: 60-120 Ma rather than 70-130 Ma, and a cusp occurs near 140 Ma. Paleomagnetic and hotspot APW are then compared, and a new determination of true polar wander is derived. Under the (debatable but reasonable) hypothesis of fixed Atlantic and Indian hotspots, we confirm earlier findings that TPW appears episodic, with periods of (quasi-) standstill (Jurassic, Late Cretaceous/Tertiary) alternating with periods of faster TPW (in the Cretaceous and most convincingly in the last 10, or even 3 Ma). The typical duration of these periods is on the order of a few tens of millions of years with wander rates during fast tracks on the order of 30 to 50 km/Ma. A total TPW of some 30^o is suggested for the last 200 Ma. We find no convincing evidence for episodes of superfast TPW. We use our master synthetic APWP to predict the latitude evolution of test points in North America, South Africa and India, and compare those with estimates derived in the hotspot and TPW reference frames. We show that the three are mutually consistent. Comparison over the last 130 Ma of TPW deduced from hotspot tracks and paleomagnetic data in the Indo-Atlantic hemisphere with an independent (and methodologically distinct) determination for the Pacific plate supports the idea that, to first order, TPW is a truly global feature of Earth dynamics. Comparison with numerical modelling estimates of TPW shows that all current models still fail to some extent to account for the observed values of TPW velocity, and for the succession of standstills and tracks which is observed.