We present geochemical data from tephra layers obtained using an Electron Microprobe Analyser (EMPA) contained within the lacustrine sequence that infilled Onepoto Maar lake, Auckland, New Zealand. The dataset includes compositional analyses of 14 rhyolitic, seven basaltic, and two andesitic tephra layers, sourced from the Taupo Volcanic Zone (TVZ), Taranaki Maunga, and the Auckland Volcanic Field (AVF). These data are critical to support the revised age model developed for the Onepoto lake sediment record. Each microprobed tephra layer is characterised by distinctive major and trace element concentrations that facilitated the identification of the geochemical signatures essential for accurate matching of the tephra with their source volcanic centres, as well as inter-and intra-core matching of the sediment records. The integration of these geochemical signatures with radiocarbon ages from bulk organic matter and pollen concentrates extracted from the Onepoto sediment record enhanced the reliability of the new age-depth model. This geochemical tephra dataset underpins the chronological framework of the Onepoto tephrastratigraphy, thereby contributing to a deeper understanding of the timing of volcanic activity on New Zealand's North Island and its implications for Late Quaternary paleoenvironmental research in the Southwest Pacific.

Description of EMPA Data File for Tephra Layers in Onepoto Maar Lake SequenceThis dataset presents detailed geochemical analysis of tephra layers from the sedimentary sequence of Onepoto Maar Lake, Auckland, New Zealand, conducted using Electron Microprobe Analysis (EMPA). The data includes compositional measurements for major elements (e.g., SiO₂, TiO₂, Al₂O₃) and trace elements (e.g., K₂O, Na₂O, CaO, FeO), recorded for individual glass shards from 23 tephra layers (14 rhyolitic, 7 basaltic, and 2 andesitic), sourced from various volcanic centers, including the Taupo Volcanic Zone (TVZ), Taranaki Maunga, and the Auckland Volcanic Field (AVF).These geochemical signatures are crucial for establishing precise tephrochronology and improving the age-depth model for the Onepoto maar sediment core. The dataset is used in conjunction with radiocarbon dating of organic materials and pollen to refine the chronological framework for the region's Late Quaternary volcanic and paleoenvironmental history.File Structure and Columns: The dataset is organized into a series of rows corresponding to individual EMPA analyses of tephra samples. Each row provides the elemental concentrations for each analysis, with the columns structured as follows:Tephrochronology: The elemental compositions allow for the identification and geochemical fingerprinting of individual tephra layers, supporting accurate correlation and matching with source volcanic events from the Taupo Volcanic Zone (TVZ), Taranaki Maunga, and the Auckland Volcanic Field (AVF).Chronological Model: The data is integral to the development of the revised age model for the Onepoto Maar lake sediment sequence, enhancing the precision of paleoenvironmental reconstructions.Paleoenvironmental Research: This geochemical dataset contributes to a better understanding of volcanic activity and environmental changes in New Zealand's North Island during the Late Quaternary.Methodology:Electron Microprobe Analysis (EMPA): Glass shards from tephra layers were analyzed using EMPA to determine the elemental concentrations. Each analysis provides precise, high-resolution data on the composition of individual shards within each tephra layer.