High-resolution Neogene reconstructions of Eurasia-North America Plate motion

• Published in: Geophysical Journal International
• Main Authors: Merkouriev, S., DeMets, C.
• Format: Text
• Language: English
• Published: Oxford University Press 2014
• Subjects: Geodynamics and tectonics; Arctic; Gakkel Ridge; Molloy; Arctic Basin
• Online Access: http://gji.oxfordjournals.org/cgi/content/short/198/1/366; https://doi.org/10.1093/gji/ggu142

We estimate Eurasia-North America Plate motion rotations at ∼1-Myr intervals for the past 20 Myr from more than 11 000 crossings of 21 magnetic reversals from Chron 1n (0.78 Ma) to C6no (19.72 Ma) and flow lines digitized from the Charlie Gibbs, Bight and Molloy fracture zones and transform faults. Adjusted for outward displacement, the 21 best-fitting rotations determined from a simultaneous inversion of the numerous kinematic data reconstruct the reversal crossings with weighted root mean square misfits of only 1–2 km and 0.2–7 km for the transform fault and fracture zone crossings. The new rotations clearly define a ∼1000 km southward shift of the rotation pole and 20 per cent slowdown in seafloor spreading rates between 7 and 6 Ma, preceded by apparently steady plate motion from 19.7 to ∼7 Ma. Data for times since C3An.2 (6.7 Ma) are well fit by a stationary pole of rotation and constant rate of angular opening, consistent with steady motion since 6.7 Ma. The southward shift of the rotation pole at 7–6 Ma implies that Eurasia-North America motion in northeastern Asia changed from slowly convergent before 7 Ma to slowly divergent afterward. Crossings of magnetic reversals C1n through C3An.1 (6.0 Ma) are well fit everywhere in the Arctic basin and south to the Azores triple junction, indicating that the Eurasia and North America plates have not deformed along their mutual boundary since at least 6.0 Ma. However, the new rotations systematically overrotate magnetic lineations older than C3An.1 (6.0 Ma) within 200 km of the Azores triple junction and also overrotate lineations older than C5n along the Gakkel Ridge in the Arctic Basin. Barring misidentifications of the magnetic anomalies in those areas, the pattern and magnitude of the systematic misfits imply that slow (∼1 mm yr−1) distributed or microplate deformation occurred in one or both regions.