The presented data forms the basis for the reconstruction of the depositional history of Onepoto maar lake (Northern New Zealand) as a response to regional and global drivers of climatic change, as well as localised events restricted to the lake catchment. The presented data set comprises stacked m-XRF elemental variability trends obtained from lake sediment cores extracted from Onepoto Basin (Northern New Zealand) in 2018 and 2011 using an ITRAX core scanner (Mo-tube). These core segments form the basis on which the newly established 'On18' composite record was developed.