Japan Geoscience Union Meeting 2022

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[J] Oral

M (Multidisciplinary and Interdisciplinary) » M-GI General Geosciences, Information Geosciences & Simulations

[M-GI32] Drilling Earth Science

Fri. May 27, 2022 9:00 AM - 10:30 AM 201B (International Conference Hall, Makuhari Messe)

convener:Yumiko Harigane(Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology (AIST)), convener:Osamu Fujiwara(Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology), Yohei Hamada(Japan Agency for Marine-Earth Science and Technology Kochi Institute for Core Sample Research), convener:Junichiro Kuroda(Department of Ocean Floor Geoscience, Atmosphere and Ocean Research Institute, the University of Tokyo), Chairperson:Yumiko Harigane(Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology (AIST)), Junichiro Kuroda(Department of Ocean Floor Geoscience, Atmosphere and Ocean Research Institute, the University of Tokyo), Osamu Fujiwara(Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology), Yohei Hamada(Japan Agency for Marine-Earth Science and Technology Kochi Institute for Core Sample Research)

9:15 AM - 9:30 AM

[MGI32-07] Early Cretaceous syn-rift volcanic sequence on the Naturaliste Plateau, IODP Expedition 369 Site U1513

*Maria Luisa Tejada1, Osamu Ishizuka2, Takashi Miyazaki1, Bogdan Vaglarov1, Qing Chang1 (1.Volcano and Earth Interior Research Center, Institute for Marine Geodynamics, Japan Agency for Marine-Earth Science and Technology, 2.AIST, Geological Survey of Japan)

Keywords:Naturaliste Plateau, IODP Expedition 369, Site U1513, East Gondwana breakup

Drilling on the eastern flank of Naturaliste Plateau, offshore southwest Australia during the International Ocean Discovery Program Expedition 369 recovered a volcanic sequence at Site U1513. Up until this drilling expedition, no direct stratigraphic evidence corroborates the extensive volcanism that accompanied Early Cretaceous rifting between Australia-Antarctica and Greater India during breakup of Eastern Gondwana, which was inferred only from seismic reflection and dredging data. The volcanic sequence consists of several lava flow packages separated by volcaniclastic flow units. Multiple dolerite dikes intruded along steeply dipping faults. Paleomagnetic data obtained from the overlying sedimentary sequence indicate emplacement before chron M10Nn.1n, which could be as young as 130.9 Ma or as old as 134.2 Ma, depending on the time scale used. Age obtained from plagioclase separates from the topmost flow unit overlaps with the younger paleomagnetic age of 130 Ma, suggesting that deposition of the overlying sediments happened soon after. This interpretation agrees with subaerial to shallow water mode of emplacement inferred from petrological and textural evidence. Younger crystallization age of 123 Ma obtained from a dolerite dike and the 124-112 Ma alteration ages determined from the lower flows indicate that magmatism remained active during the Aptian (126.3–113.0Ma). Trace elements vary from light rare earth element (LREE) enriched transitional basalt to LREE-depleted tholeiitic basalt compositions. This is coupled with a change from isotopically more enriched to depleted compositions toward the upper flows, suggesting evolving mantle source. These observations possibly indicate thinning lithosphere from rifting to breakup of East Gondwana and increasing input from asthenospheric source.