Traces of explosive eruptions in Cretaceous to Quaternary Indian Ocean sediments.

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During IODP Expeditions sediments with intercalated tephra layers have been drilled and sampled that reach down to the Campanian. The drill sites are located ~800 km west of the volcanic front of the Sunda arc in the Indian Ocean. The objectives of the cruises were to determine the material properties causing the seismogenic slip and to reconstruct and understand changes in Indian monsoon circulation. In this project we aim to establish a marine tephrostratigraphic framework for the entire region by correlating widespread tephra layers between the different sites and if possible, to terrestrial eruptions. Therefore we will combine the tephra records of Expeditions with marine tephra layers from previous ODP drillings from the whole Indian Ocean, and on the Ninetyeast Ridge in particular. Geochemical, petrological and volcanological approaches for tephra and sediment characterization will be used to quantitatively and qualitatively decrypt their provenance and the eruption succession. Additionally, we will perform absolute age dating to improve and confirm the existing age models. Robust age models are needed to study the temporal and spatial changes in eruption processes, magnitudes and frequencies of large volcanic eruptions from the Sunda arc, or so far unknown volcanic sources.This study will help to learn more about the temporal evolution of different volcanic systems and establish long time series of explosive volcanism in this region. Within our record we will identify large, known, but also previously unknown, eruptions, which will enable us to study the respective recurrence rates from Pleistocene volcanic centres of the Sumatran arc and to elaborate on cyclicities in the tephra record. Finally, we will also study the Miocene to Pleistocene sediment record of the Nicobar Fan to detect potential episodes of enhanced volcanism or single events hidden in the background sedimentation. Especially the determination of the amount and character of volcanic matter that is incorporated in the sediments is important to characterize the material and how it acts, when it is subducted at the seismogenic and tsunamogenic Sumatran convergent margin.