• Energy Research

AbstractDuring mid-Cretaceous Oceanic Anoxic Event 2, significant increase of atmospheric carbon dioxide concentrations from the eruption of the large igneous provinces is hypothesized to have induced a humid climate and an elevation in nutrient runoff from continents to the oceans, resulting in oxygen depletion in the ocean. However, hitherto there is limited insight into the driving factors of Oceanic Anoxic Event 2 from the Pacific and Asian continental margins, even though the former and the latter were the largest ocean and landmass at that time. Here, a multiproxy analysis for the Oceanic Anoxic Event 2 interval of the Yezo Group –deposited on northwestern Pacific along the active Asian continental margin– is interpretated to identify seven volcanic pulses, five of which may have elevated humidity, weathering intensity, and vegetational change in the eastern margin of Asia. Moreover, oxygen depletion occurred simultaneously in the northwest Pacific. Given that these environmental changes in the eastern margin of Asia were penecontemporaneous with the global carbon burial intervals during Oceanic Anoxic Event 2, the elevated nutrient supply from the Asian continental margin to the Pacific Ocean may have, in part, contributed to the worldwide depletion of oxygen of the ocean during Oceanic Anoxic Event 2.

1 = present, - = absent, ? questinable occurence

Mid-Cretaceous oceanic anoxic event 2 (OAE2) is one of the largest carbon cycle perturbations during the Cretaceous period and is regarded as the analog of the present-day warming of the Earth due to the abrupt increase in pCO2 and global warming. It has been hypothesized that increased pCO2 from an eruption of large igneous provinces (LIPs) during OAE2 produced global warming and increased nutrient delivery from continents to oceans, causing oxygen depletion in the oceans globally. Although the Pacific Ocean and the Asian continent were the largest ocean and landmass during the mid-Cretaceous, only limited studies have been performed on the OAE2 strata in the sections of the Pacific and Asian continental margin. This dataset provides the results of a multiproxy analysis of the OAE2 strata in northwestern Hokkaido, Japan, consisting of calcareous nannofossil biostratigraphy, carbon isotope and osmium isotope stratigraphy, degree of pyritization (DOP), XRF analysis, clay mineral chemistry and biomarker analysis. Our result identified seven volcanic pulses, five of which may have elevated humidity, weathering intensity, and vegetational change in the eastern margin of Asia. Moreover, oxygen depletion occurred simultaneously in the northwest Pacific. Given that these environmental changes in the eastern margin of Asia were penecontemporaneous with the global carbon burial intervals during Oceanic Anoxic Event 2, the elevated nutrient supply from the Asian continental margin to the Pacific Ocean may have, in part, contributed to the worldwide depletion of oxygen of the ocean during Oceanic Anoxic Event 2.