Norbert Bonhommet
University of Rennes
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Featured researches published by Norbert Bonhommet.
Geology | 1984
Hervé Perroud; Rob Van der Voo; Norbert Bonhommet
New paleomagnetic data support the contention that Armorica and Gondwana formed a coherent block until Ordovician time. However, by Early Devonian time, Armorica collided with the North American–northern European assembly to form the Old Red Continent, and the collision itself was responsible for the Acadian orogeny, not for the earlier Taconic orogeny as postulated previously. The Carboniferous collision of Gondwana with the Old Red Continent subsequently formed Pangaea and produced the Appalachian-Hercynian orogeny.
Journal of Geophysical Research | 1991
Annick Chauvin; Pierre-Yves Gillot; Norbert Bonhommet
A paleomagnetic study has been undertaken on two late Quaternary volcanic sequences from the Piton de la Fournaise volcano (island of La Reunion) in order to provide absolute paleointensities of the Earths magnetic field from a site in the southern hemisphere. The pattern of secular variation recorded by both sequences clearly indicates that the extrusion rate of the lava flows was not constant with time. A detailed investigation of the magnetic properties of the samples was carried out in parallel with paleointensity experiments which were performed with the Thellier method. Samples with minimum overprint, composed by single-domain or pseudo-single-domain magnetite showing good thermal stability and a narrow blocking temperature spectrum were the most successful during Thelliers experiments. Values of the paleofield strength from 19 to 55 mT have been obtained on 23 flows among the 30 which were sampled. Few variations (7.5–9.9×1022 A m2) are observed in the virtual dipole moments (VDMs) determined on the youngest sequence (5–12 ka). Those values are within the range of fluctuations of the worldwide variations of VDMs for this period. On the other hand, data from the oldest sequence (82–98 ka) are the first paleointensity values obtained in that time period, and the observed VDMs extend from 4.1 to 8.8×1022 A m2. These results suggest that for this time interval, the field did not depart from its average behavior.
Geological Society of America Bulletin | 1977
Norbert Bonhommet; Melvin H. Beeson; G. Brent Dalrymple
Chemical analyses of four lava flows from Lanai, Hawaii confirm petrographic observations that the flows of Lanai are typical Hawaiian tholeiites, somewhat more similar in composition to those of Mauna Loa than to those of Kilauea. K-Ar analyses of six samples indicate that Lanai is 1.25 ± 0.04 m.y. old, which is consistent with the hypothesis that the volcanoes of the Hawaiian Islands become older to the northwest from the active volcanoes of Mauna Loa and Kilauea to Kauai.
Geophysical Research Letters | 1989
Annick Chauvin; Robert A. Duncan; Norbert Bonhommet; Saul Levi
Geophysical Journal International | 1979
Meridee Jones; Rob Van der Voo; Norbert Bonhommet
Journal of Geophysical Research | 1988
Monte Marshall; Annick Chauvin; Norbert Bonhommet
Geophysical Journal International | 1986
H. Perroud; Norbert Bonhommet; J. P. Thebault
Geophysical Journal International | 1984
H. Perroud; Norbert Bonhommet
Geophysical Journal International | 1983
H. Perroud; Norbert Bonhommet; R. Van der Voo
Geophysical Journal International | 1983
Russell Perigo; Rob Van der Voo; Bernard Auvray; Norbert Bonhommet