Middle Cenozoic unconformities in the Waihao Valley, South Canterbury Basin, New Zealand

Master's Thesis from the year 2019 in the subject Geography / Earth Science - Geology, Mineralogy, Soil Science, University of Otago, language: English, abstract: This thesis presents descriptions and interpretations of stratigraphic sections in the lower Waihao Valley, southern Canterbury Basin. The aim of this reconnaissance study was to describe and interpret the age, origin and significance of previously identified unconformities in the Eocene ¿ Oligocene sedimentary succession. Four sections were logged and sampled for foraminiferal biostratigraphy. Sedimentary petrological ¿ and petrophysical analysis was carried out to understand the provenance and lithological variations to either confirm or contradict previous local paleoenvironmental interpretations. Provenance analysis shows that the terrigenous influx in the Eocene ¿ Oligocene strata was probably derived from nearby Torlesse Terrane metasedimentary rocks of Permian age and Cretaceous to Eocene Taratu Formation, suggested by the occurrence of abundant polycrystalline quartz grains. The parautochthonous glauconite in the Eocene ¿ Oligocene strata in the lower Waihao Valley indicates a slow sediment deposition rate in a marine shelf environment and confirms previous local paleoenvironmental interpretations of the southern Canterbury Basin. The outcome of this thesis is the lithostratigraphy and chronostratigraphy of the lower Waihao Valley, a confident identification of a new location of the regional Mid ¿ Oligocene Marshall unconformity representing a hiatus of at least 2.5 Ma, and the confirmation of local Eocene ¿Oligocene paleoenvironmental interpretations, which add valuable contributions to the wider southern Canterbury Basin geology.