Eocene-Oligocene Benthic Foraminifera Stable Isotope Stratigraphy and Paleoceanography of ODP Site 757 and 756, Ninetyeast Ridge, Southern Indian Ocean

• Main Author: Holmström, Max
• Format: Bachelor Thesis
• Language: English
• Published: Stockholms universitet, Institutionen för geologiska vetenskaper 2014
• Subjects: Indian; Antarc*; Antarctica
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-107074

The EOT is marked by a two-step shift in the δ18O record of benthic foraminifera. The transition was rapid (500 000 years) and occurred roughly 34 million years ago. It marks an important step in Earth’s climate history where semi-permanent ice-sheets developed over Antarctica and is considered the initiation of the modern glaciated climate that the Earth experience today. Ninetyeast Ridge is a hot spot trail in the Indian Ocean that was formed by the Keguelen/ Ninetyeast hotspot and was one of the drilling targets of ODP leg 121 and among other sites 757 and 756 were drilled. To gain a better understanding of the paleoceanography and better constrain the timing of the EOT in the Indian Ocean, benthic foraminifera stable isotopes in Cibicidoides havanensis was analysed at site 757B and Cibicidoides mundulus at site 756C and was then age calibrated using an age model. The results indicate that the significant two-step shift that characterizes the EOT is present at Site 757B. However the results also indicate that it is not sufficient to use an age model that assumes a constant sedimentation rate since it changed drastically at this site at the E-O boundary. Finally the results indicates that there may have been several water masses operating simultaneously in the Indian Ocean at the EOT, the water masses discussed as most likely in this thesis is AAIW and TISW.