Geochemical fingerprinting (EMPA) - Tephras contained in the lacustrine sequence of Onepoto Basin (On18 composite core)

Tephrochronology has proven to be a very reliable dating tool in the context of northern New Zealand lakes as a consequence of the numerous volcanic centres present on the North Island that have been repeatedly erupting throughout the late Quaternary and produced widely-distributed tephra with distinctive geochemical compositions. Many of these tephra layers are preserved in the sedimentary archives contained in the Auckland Volcanic Field (AVF) maar lakes. In total 25 rhyolitic tephra (OVC/TVC), 23 andesitic tephra (EgVc/TgVc) and 2 basaltic (AVF) deposits from the new Onepoto lake sediment composite record (On18 core) were identified by EMPA major oxide geochemistry. These data sets (presented in this repository) were used for geochemical correlation to the detailed tephra stratigraphy presented in Shane and Hoverd (2002) as well as refinements by Molloy et al. (2009) and Hopkins et al. (2015). Further tephra layers that were not analysed by EMPA were identified through stratigraphic correlation. Based on the established tephra stratigraphic framework, a new age model could be established for Onepoto lake sediment sequence, using revised ages of 12 rhyolitic, seven basaltic, and two andesitic marker tephra layers combined with bulk carbon and pollen derived radiocarbon ages.