Tephrochronostratigraphy in marine and terrestrial sediments of New Zealand: Benchmark for Miocene to Quaternary explosive volcanism

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During IODP Expeditions 372 and 375 sediments have been drilled and sampled down to the Cretaceous including intercalated tephra layers from the Miocene to Holocene. The drill sites are located in the Pacific, ~250 km downwind of the Taupo volcanic Zone (TVZ), one of largest and most frequently active silicic centers on earth, and also close to the Coromandel volcanic zone (CVZ) a sparsely investigated Neogene volcanic arc. The tephra inventories of these intermediate distant sites provide the missing link between the proximal (<~100 km) terrestrial and very distal (~1000 km) ODP sites to establish a nearly complete eruptive history from the early Miocene to recent for New Zealand´s explosive volcanism. Within three major goals, proposed in an earlier proposal, compositional, temporal, and genetic differences of its eruption products and associated sediments will be investigate.Since the pandemic situation prevented us from field work in New Zealand to assist the marine work and also compromised our lab work and analytical lab visits, we are delayed and propose here an extension of 6 month, basically to secure the PhD´s work and thesis. During the first 24 months of this proposal this project focused on the volcanic products from highly explosive eruptions from New Zealand during the Neogene and Quaternary in all deep drilling sites off New Zealand. We used geochemical, petrological and volcanological approaches for tephra and sediment characterization to quantitatively and qualitatively decrypt their provenance and the eruption succession and fulfilled therefore goal 1 of the initial proposal. We successfully reconstructed the cyclic history of highly explosive volcanic activity of both arc systems (CVZ and TVZ) over a time span of about at least 13 Myrs (parts of goal 2) and will further address in the extension questions regarding compositional and genetic differences and similarities, as well as recurrence rates and periodicities in both systems, covering for the first time also a Neogene eruption time series. Bulk rock sediment geochemistry, already acquired as parts of goal 3, in conjunction with macroscopic tephras and cryptotephras will enable in the extension the temporal and quantitative characterization of the sediment composition at the incoming plate in relation to the volcaniclastic input and possible slide masses.