The Jurassic System in SW Japan: review of recent research

The present state of the art in Jurassic oceanicplate stratigraphy in Japan is the result of research over the last two decades. Radiolarian biochronology puts age constraints on the development of fore-arc basin deposits, which cover Permian and Jurassic accretionary complexes of the Outer Zone, facing the Pacific. Special attention is given to the “Torinosu-type” reef-limestone blocks in the Upper Jurassic-Lower Cretaceous fore-arc basin deposits that derived from a shallow-marine continental margin such as the Inner Zone shelf, facing Eurasia. Further progress was achieved in dating and defining sedimentary environments in the Inner Zone Tetori Group. Erosive events during the process of Jurassic accretion are also discussed in relation to the Late Mesozoic geologic and tectonic setting.     

The Triassic-Jurassic boundary in the Middle Eastern Levant: The magmatic event

The Asher Volcanism (207—189 Ma) represents a significant magmatic event, which since recent radiometric data, seem to straddle the Triassic/Jurassic boundary. Extending from the Mediterranean coast, across Galilee to Mount Hermon, the unusually thick volcanic sequence is interstratified with Late Triassic limestone and Early Jurassic shale. The event unfolded during an active phase of continental breakup in Gondwana, with the volcanism contemporaneous with the regional uplift of the Arabian Plate that caused denudation of the Triassic substratum, and sealed by a marked angular unconformity and development of laterites. A deep chasm filled with volcanics runs along an old NW-SE fault system characterizing the Arabian Plate and nearly perpendicular to the NE-SW Palmyrid aulacogen, which relates to an aborted breakaway of the Syrian promontory from mainland Gondwana. The volume of Asher volcanics may also reflect the role of volcanism in the T/J mass-extinction as proposed in 2004.     

The Jurassic System in SW Japan: review of recent research

The present state of the art in Jurassic oceanicplate stratigraphy in Japan is the result of research over the last two decades. Radiolarian biochronology puts age constraints on the development of fore-arc basin deposits, which cover Permian and Jurassic accretionary complexes of the Outer Zone, facing the Pacific. Special attention is given to the “Torinosu-type” reef-limestone blocks in the Upper Jurassic-Lower Cretaceous fore-arc basin deposits that derived from a shallow-marine continental margin such as the Inner Zone shelf, facing Eurasia. Further progress was achieved in dating and defining sedimentary environments in the Inner Zone Tetori Group. Erosive events during the process of Jurassic accretion are also discussed in relation to the Late Mesozoic geologic and tectonic setting.