Detection of diluted marine tertiary tephra by electron spin resonance and magmatic measurements

Abstract

Oligocene sediments from ODP leg 115 (South Indian Ocean), Site 709 and Site 711, have been investigated using electron spin resonance (ESR) and magnetic susceptibility measurements, to detect volcanic tephra layers of supposed Ethiopian traps origin. The results obtained at room temperature, without separating the volcanic material from the bulk sediment, show that the ash-content strongly influences the lineshape and intensity of the ESR signal. As a result, the ESR alone, can be used as a powerful tool for characterizing the diluted ash-content of marine sediments. We have also found a strong similarity between the ESR spectra of the same tephra layers from the two sites.