Kyushu University, Kumamoto University, Japan Agency for Marine-Earth Science and Technology, Kobe University, Chiba Institute of Technology, Waseda University started with large-scale volcanic activity in the "rainy era" about 2 million years ago to 3400 million years ago. It was revealed that volcanic activity and long rains may have caused simultaneous changes in the ecosystem such as mass extinction of marine organisms and diversification of dinosaurs on land.
It is known that the Triassic period of the Mesozoic period (about 2 million years ago to 5190 million years ago) had a generally hot and dry climate, of which about 2 of the period called "Carnian". From 130 million years ago to 2 million years ago, there are traces of the "rainy era" in which rainfall increased for about 3400 million years. This climate change, called the "Carnian heavy rainfall event," coincided with the extinction of some organisms and the time of major evolutionary changes, but it was not known what caused the long rains.
In this study, we investigated a rock called a chart observed on the Kiso River bed in Sakahogi Town, Gifu Prefecture, and discovered a low osmium isotope ratio peculiar to the mantle material inside the earth from the chart in the early Carnian period.This is evidence of the large-scale volcanic activity that occurred in the early Carnian and the large supply of osmium derived from it to the ocean.
In addition, dating using conodont fossils and organic carbon isotope strata found that the rainy era had arrived during periods of high volcanic activity.In other words, it was very likely that volcanic activity triggered the Carnian heavy rainfall event.
The large-scale volcanic activity of Carnian revealed in this study led to rapid changes in temperature and anoxicization of the ocean, and the mass extinction that occurred in this era is similar to the mass extinction in other eras. May have been involved in.In addition, since it is thought that the explosive diversification of dinosaurs and the birth of mammals also occurred during the Carnian heavy rainfall event, what kind of environmental changes will be caused by volcanic activity during this period, and the ecology. It is necessary to proceed with research on whether it contributed to system change.
Paper information:[Global and Planetary Change] Marine osmium isotope record during the Carnian “pluvial episode” (Late Triassic) in the pelagic Panthalassa Ocean
