Other
Scientific paper
May 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008agusmgp44a..03s&link_type=abstract
American Geophysical Union, Spring Meeting 2008, abstract #GP44A-03
Other
1525 Paleomagnetism Applied To Tectonics: Regional, Global, 1532 Reference Fields: Regional, Global, 3037 Oceanic Hotspots And Intraplate Volcanism, 8137 Hotspots, Large Igneous Provinces, And Flood Basalt Volcanism, 9610 Cretaceous
Scientific paper
The hotspot (HS) fixity axiom installed early in the plate tectonics as an attractive toll for geodynamic analyzes. In particular, a mid-Cretaceous discrepancy between fixed Indo-Atlantic hotspot and paleomagnetic reference frames has been interpreted as evidence for true polar wander (TPW). Recent paleomagnetic findings (C.B. Zaffarana, this session) indicate that the Americas rotated (with different angular rates) about the spin axis between 125 and at least 100 Ma. This kinematic-paleogeographic scenario points to failure of the above mentioned TPW hypothesis, suggesting that the mid-Cretaceous HS-paleomagnetic discrepancy is related to motion of the Atlantic hotspots. On the other hand, dated outcrops and seamounts in the >2000 km White Mountains - New England trail define a tight cluster with no clear age progression when observed in African coordinates, suggesting that the sub-lithospheric melting anomaly responsible for the New England chain moved little with respect to Africa between 120 and 80 Ma. However, small circles centered in the feeder of the New England seamounts as seen from Africa misfit the 120-80 Ma trend of the Walvis ridge in the African South Atlantic, arguing for ~1 cm/yr inter-Atlantic HS motion, which in turn represents about 30 % the rate of coeval full spreading in the Central Atlantic. These observations suggest that a scenario where sub-lithospheric melting anomalies move and deform in concert with flow in the surrounding mantle needs to be allowed for assaying tectonic and geodynamic models. In agreement with this, reconstruction of Cretaceous poles from the Americas with respect to the moving-hotspot framework developed by O´Neill et al. (G3 6 (4), 2005) reduced to a half the paleopole-spin axis offset observed in fixed-HS coordinates (R. Somoza and C.B. Zaffarana, EPSL, in revision), with the residual offset being similar than that is found when large datasets of Cenozoic poles are observed in moving-HS coordinates.
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