Pittari, AdrianWilde, Sarah2026-08-212026-08-212026https://hdl.handle.net/10289/18574This study characterises the Wairēinga (Bridal Veil) Falls lava flow and reconstructs the palaeoenvironmental and volcanic history associated with this lava flow at Te Mata Quarry through integrated field observations and laboratory analyses. Stratigraphic logging, petrographic analysis, grain-size analysis, X-ray fluorescence (XRF), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectroscopy (SEM-EDS), and portable XRF (pXRF) were used to investigate volcanic and sedimentary units exposed throughout the quarry. The sedimentary sequence beneath the lava flow contains glauconite and abundant bioclastic material, indicating deposition in a shallow marine environment associated with the Oligocene Te Kuiti Group. In contrast, buried wood and coal horizons, and hyaloclastite beneath the basalt, which unconformably cross-cuts the Te Kuiti Group, demonstrate that a wet terrestrial valley had developed prior to lava emplacement in the late Pliocene/early Pleistocene. The Wairēinga Falls lava flow was emplaced at approximately 2.57 Ma into this water-influenced palaeovalley. Hyaloclastite preserved along flow margins provides evidence of lava–water interaction, indicating that surface or near-surface water strongly influenced cooling and fragmentation during emplacement. Petrographic and geochemical analyses reveal a compositionally homogeneous basalt consistent with previous studies of the region. However, structural features including variable columnar joint spacing, multidirectional joint orientations, and rosette jointing suggest a complex emplacement history involving multiple flow units and the development of lava tubes, indicating spatial variability in emplacement processes despite a uniform magma composition. The overlying Kauroa Ash sequence, particularly the T5 tephra, provides regional context and supports correlations with volcanic activity in the central North Island, including the Ongatiti Ignimbrite. Together, these findings place the lava flow and its emplacement environment in the Te Mata Quarry within the broader volcanic evolution of the Alexandra Volcanic Group, and improve understanding of lava emplacement processes, in a wet palaeoenvironment.enAll items in Research Commons are provided for private study and research purposes and are protected by copyright with all rights reserved unless otherwise indicated.Thesis