Expedition 391 Scientific Prospectus: Walvis Ridge Hotspot: drilling Walvis Ridge, Southeast Atlantic Ocean, to test models of ridge-hotspot interaction, isotopic zonation, and the hotspot reference frame

Abstract

Portions of this work may have been published in whole or in part in other IODP documents or publications.This IODP Scientific Prospectus is based on precruise JOIDES Resolution Facility advisory panel discussions and scientific input from the designated Co-Chief Scientists on behalf of the drilling proponents. During the course of the cruise, actual site operations may indicate to the Co-Chief Scientists, the Expedition Project Manager/ Staff Scientist, and the Operations Superintendent that it would be scientifically or operationally advantageous to amend the plan detailed in this prospectus. It should be understood that any substantial changes to the science deliverables outlined in the plan presented here are contingent upon the approval of the IODP JRSO Director and/or JOIDES Resolution Facility Board.

Expedition 397T Scientific Prospectus: Transit and Return to Walvis Ridge Hotspot

“…Similar sediments were cored at Site U1578. Organic geochemistry safety monitoring during Expedition 391 found hydrocarbons to be at the atmospheric background level at all drilled sites, including at Site U1578 (Sager et al, 2022), which represents a depositional setting similar to those of the nearby GT and TT sites. The methane concentration obtained from Hole U1578A, measured at a frequency of one sample per 9.6 m of sediment core, ranged 0-1.13 μL/L.…”

“…The scientific rationale for Expedition 397T coring is the same as for Expedition 391. Please see the Expedition 391 Scientific Prospectus and Preliminary Report (Sager et al, 2020(Sager et al, , 2022 for detailed background information.…”

“…Having a large number of independent samples of the magnetic field inclination (i.e., measurements that are not close in time) is key to determining paleolatitude with small uncertainty estimates. Coring at Site U1578 produced an excellent section that spans >1 My in duration (Sager et al, 2022), but until paleomagnetic studies are completed, we will not know how well the paleomagnetic field was measured. Proposed Sites GT-6A and TT-3A are expected to provide basaltic lavas similar in age to Site U1578, so new paleomagnetic data from those sites can be used to better determine the latest Cretaceous-earliest Cenozoic paleolatitude.…”

“…During IODP Expedition 391 (Walvis Ridge Hotspot), the Tristan-Gough-Walvis Ridge (TGW) hotspot track was cored in December 2021-February 2022 (Sager et al, 2022). Its overarching objective was to recover basaltic rock from TGW edifices to understand the evolution of Walvis Ridge and related guyots.…”

Expedition 397T Preliminary Report: Return to Walvis Ridge Hotspot

“…The scientific background for Walvis Ridge hotspot drilling is given at length in the Expedition 391 Preliminary Report (Sager et al, 2022), so only an outline is given here. Walvis Ridge is a long, quasilinear ridge and seamount chain that stretches from the African margin to the active volcanoes of Tristan da Cunha and Gough Island (Figure F3).…”