The anticorrelated velocities of Africa and India in the Late Cretaceous and early Cenozoic

• Published in: Geophysical Journal International
• Main Authors: Cande, Steven C., Patriat, Philippe
• Other Authors: Institut de Physique du Globe de Paris (IPGP), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Institut de Physique du Globe de Paris (IPG Paris)-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2015
• Subjects: Plate motions; Kinematics of crustal and mantle deformation; Indian Ocean; [SDU]Sciences of the Universe [physics]; Antarctic; Indian; Southeast Indian Ridge; Antarc*; Antarctica
• Online Access: https://hal-insu.archives-ouvertes.fr/insu-03580035; https://hal-insu.archives-ouvertes.fr/insu-03580035/document; https://hal-insu.archives-ouvertes.fr/insu-03580035/file/ggu392.pdf; https://doi.org/10.1093/gji/ggu392

International audience We present a revised interpretation of magnetic anomalies and fracture zones on the Southwest Indian Ridge (SWIR; Africa-Antarctica) and the Southeast Indian Ridge (SEIR; Capricorn-Antarctica) and use them to calculate 2-plate finite rotations for anomalies 34 to 20 (84 to 43 Ma). Central Indian Ridge (CIR; Capricorn-Africa) rotations are calculated by summing the SWIR and SEIR rotations. These rotations provide a high-resolution record of changes in the motion of India and Africa at the time of the onset of the Reunion plume head. An analysis of the relative velocities of India, Africa and Antarctica leads to a refinement of previous observations that the speedup of India relative to the mantle was accompanied by a slowdown of Africa. The most rapid slowdown of Africa occurs around Chron 32Ay (71 Ma), the time when India's motion relative to Africa notably starts to accelerate. Using the most recent Geomagnetic Polarity Timescale (GTS12) we show that India's velocity relative to Africa was characterized by an acceleration from roughly 60 to 180 mm yr -1 between 71 and 66 Ma, a short pulse of superfast motion (∼180 mm yr -1 ) between 66 and 63 Ma, an abrupt slowdown to 120 mm yr -1 between 63 and 62 Ma, and then a long period (63 to 47 Ma) of gradual slowing, but still fast motion (∼100 mm yr -1 ), which ends with a rapid slowdown after Chron 21o (47 Ma). Changes in the velocities of Africa and India with respect to the mantle follow a similar pattern. The fastest motion of India relative to the mantle, ∼220 mm yr -1 , occurs during Chron 29R. The SWIR rotations constrain three significant changes in the migration path of the Africa-Antarctic stage poles: following Chron 33y (73 Ma), following Chron 31y (68 Ma), and following Chron 24o (54 Ma). The change in the migration path of the SWIR stage poles following Chron 33y is coincident with the most rapid slowdown in Africa's motion. The change in the migration path after Chron 31y, although coincident with the most rapid acceleration of ...