GP23A-1280
High resolution dating of young magmatic oceanic crust using near-seafloor magnetics
Tuesday, 15 December 2015
Poster Hall (Moscone South)
Jerome Dyment1, Mitsuko Kitazawa1,2, Christophe Hemond3, Hervé Guillou4, Annick Chauvin5, Morgane Ravilly5,6, Chie Honsho7,8 and Cruise GIMNAUT Scientific Party, (1)Institut de Physique du Globe de Paris, Paris, France, (2)Now at Schlumberger Kabushiki Kaisha Center, Fuchinobe, Chuo, Sagamihara, Kanagawa, Japan, (3)Université de Brest, CNRS UBO, Laboratoire Domaines Océaniques, Plouzané, France, (4)Laboratoire des Sciences du Climat et de l’Environnement - IPSL, Gif sur Yvette, France, (5)University of Rennes, Rennes Cedex, France, (6)Now at Creocean, La Rochelle, France, (7)Now at International Research Institute of Disaster Science (IRIDeS), Tohoku University, Sendai, Japan, (8)Atmosphere and Ocean Research Institute, University of Tokyo, Kashiwa, Japan
Abstract:
We compare two independent dating methods on a section of oceanic crust created within the last million year on the Central Indian Ridge axis at 19°10'S, an area affected by the Reunion hotspot. First, near-seafloor magnetic anomalies display characteristic sequences of magnetic intensity variations that we confidently identified by comparison with published paleointensity curves for the Brunhes period and used as a dating tool. This approach is further confirmed by the linear trend relating the NRM (Natural Remanent Magnetization) and paleointensity measured on rock samples along the same section. Second, valid K-Ar and Ar-Ar ages are determined on enriched basalt samples collected by deep-sea submersible. They show an excellent coincidence with the magnetic ages and support the use of high-resolution, near-seafloor marine magnetic anomalies as an efficient tool to date the young magmatic oceanic crust, where radiometric methods are generally unpractical, with unprecedented resolution. The ages obtained on the CIR reveal a 150-200 kyr cyclicity in the magmatic and tectonic processes of seafloor formation, two ridge jumps of 2.5 km and 1.2 km, respectively, and a systematic spreading asymmetry in favor to the Indian flank which may result from the interaction of the CIR with the Reunion hotspot.
