EAS Newsletter

From the Department of Earth & Atmospheric Sciences

Recent Ph.D. Graduate Sriharsha Thoram Studies True Polar Wander on IODP Expedition in Southern Atlantic Ocean

Dr. Sriharsha Thoram (Ph.D. ’21) and Dr. William Sager sailed on the drilling vessel D/V JOIDES Resolution for International Ocean Discovery Program Expedition 391, which cored the Walvis Ridge in the southeast Atlantic from December 2021 to February 2022. The project sought a better understanding of the development of this volcanic ridge, which was formed as the African plate drifted over the Tristan-Gough hotspot.

Jarely Mendez
Sriharsha Thoram carries a split core section across the JOIDES Resolution core lab to the magnetometer for measurement of paleomagnetics.

Major scientific goals were to find explanations for a split in geochemical and isotopic signatures among seamount basalts and to investigate the geodynamic anomaly in which the paleolatitude of the hotspot has changed in a way that suggests drift of the spin axis (true polar wander).

While Sager acted as co-chief scientist, Thoram focused on paleomagnetic measurements, which addressed the latter problem. They spent about seven weeks on board the ship as well as a week in quarantine beforehand.

Jarely Mendez
Sager (left) and Thoram (back, middle) pose with the paleomagnetic team on the deck of the JOIDES Resolution. The other scientists are Claire Carvallo (front center), Sorbonne University, Sonia Tikoo-Schantz (front right), Stanford University, and Kevin Gaastra (back right), Rice University.

Thoram was able to use core paleomagnetism to confirm his interpretations of magnetic anomalies within the Valdivia Bank, an oceanic plateau that is part of Walvis Ridge. He will be working with Sager and three other scientists on core paleomagnetic data. The cruise experienced a COVID-19 outbreak that caused a loss of productive time.

“Due to COVID, things rarely went as planned, but therein lies the beauty of it. The situation forced me to think out of the box and adapt to uncertainties, and I was fortunate to share a tremendous sense of camaraderie with fellow scientists,” Thoram said.

Because of lost time, IODP gave the project more drilling time as part of a transit of the ship from Cape Town to Lisbon. Sager sailed again in September and October 2022 onboard the JOIDES Resolution to complete that part of the project.