Marine Os isotopic evidence for multiple volcanic episodes during Cretaceous Oceanic Anoxic Event 1b

Hironao Matsumoto,Saburo Sakai,Rodolfo Coccioni,Nanako O Ogawa,Naohiko Ohkouchi,Fabrizio Frontalini,Junichiro Kuroda

doi:10.1038/s41598-020-69505-x

Abstract

The Aptian–Albian boundary is marked by one of the major oceanic perturbations during the Cretaceous, called Oceanic Anoxic Event (OAE) 1b. Extensive volcanic episodes at the Southern Kerguelen Plateau has been suggested as the trigger of OAE1b, but compelling evidence remains lacking. Here, we reconstructed the temporal variations of marine Os isotopic ratios across the Aptian–Albian boundary in the Tethyan and Pacific pelagic sedimentary records to elucidate the causal links between OAE1b, the biotic turnover, and volcanic episodes. Our new Os isotopic records show two negative spikes that correlate with a period of planktonic foraminiferal turnover across the Aptian–Albian boundary during OAE1b and suggest multiple submarine volcanic events. By comparing our Os isotopic profile with carbon isotopic compositions of carbonate, CaCO3 content, and the relative abundances of agglutinated foraminifera, we conclude that ocean acidification caused by the massive release of CO2 through extensive volcanic episodes could have promoted the major planktonic foraminiferal turnover during OAE1b.

Highlights

The sedimentary rock samples of PLG section were crushed and ground into fine powder in an agate mortar
The dried samples were crushed and ground to a fine powder using an agate mill. These powdered samples were used for stable carbon isotopic analyses, total organic carbon measurements to determine the host phases of Os and Re, and for Re-Os isotopic analyses
For the sedimentary rock samples from the PLG section and PLG core, ages used for the correction were 119 Ma from 0 to 6 m in the section, 117 Ma from 6 to 9 m, 115 Ma from 9 to 12 m, 114 Ma from 12 to 15 m, 113 Ma from 15 to 20 m, 112 Ma from 20 to 23 m, and 111 Ma from 23 to 26 m

Summary

Introduction

The sedimentary rock samples of PLG section were crushed and ground into fine powder in an agate mortar. These powdered samples were used for stable carbon isotopic analyses, total organic carbon measurements to determine the host phases of Os and Re, and for Re-Os isotopic analyses.

Results

Conclusion