The Japan Trench sediment core analyzed in the latest study was originally collected by scientists aboard the research vessel RV Sonne. Photo by RF Forschungsschiffahrt Bremen/Germany
Jan. 10 (UPI) -- New analysis of a sediment core from the Japan Trench suggests earthquakes play a key role in driving the deep ocean's carbon cycle. The analysis was made possible by a new technique for radio carbon dating deep ocean sediments.
Traditional radio carbon dating methods don't work for sediment layers more than 16,500 feet beneath the surface of the ocean. The intense water pressure dissolves the mineralized compounds essential to the dating technique.
Earthquakes trigger the flow of sediments from coastal shallows to the deep ocean. But to analyze evidence of this phenomenon, researchers had to find a new technique for dating deep ocean sediment layers.
The sediment core from the Japan Trench was collected at a depth of 24,744 feet. It was collected as part of a research initiative organized by the Center for Marine Environmental Sciences at the University of Bremen in Germany.
To study the core, scientists at ETH Zurich in Switzerland used a technique known as the online gas radiocarbon method. The technique quickly and efficiently measures radioactive carbon levels in the many layers of the sediment core.
Scientists at ETH coupled the radiocarbon method with a dating technique called Ramped PyrOx. It was the first time the measurement method has been used to date deep ocean sediment.
To perform the technique, scientists burn the organic matter in the core at different temperatures. The stronger chemical bonds in older organic matter cause it to burn at higher temperatures.
By comparing the different burn rates at various temperatures between two samples, scientists can estimate the age of each sediment layer.
Together, the two dating methods allowed scientists to identify increases in the concentration of older organic matter and carbon at three distinct place in the core. The three groups of sediment layers corresponded with three historical earthquakes in the Japan Trench: the Tohoku earthquake in 2011, an unnamed earthquake in 1454, and the Sanriku earthquake in 869 AD.
The findings -- detailed this week in the journal Nature Communications -- are helping scientists map the flow of carbon and sediment in the deep ocean.
"The identification and dating of tectonically triggered sediment deposits is also important for future forecasts about the likelihood of earthquakes," ETH geologist Michael Strasser said in a news release. "With our new methods, we can predict the recurrence of earthquakes with much more accuracy."