Tairua Estuary - stratigraphy of the upper estuary

Stratigraphy of the upper estuary was investigated by examining seventeen hand auger cores and three vibracores that were used to create a subsurface valley cross-section. Nine major facies were identified in the record. Estuarine facies models were used as a framework for the identification of depositional environments associated with the facies, which documented an overall trend of the upper estuary undergoing a transition from an estuarine environment to a fluvial environment as the estuary infilled. The thesis presents a model outlining the spatial and temporal infilling of the estuary. Purpose: This research was undertaken as part of a Master of Science thesis. Aim was to improve the understanding of the evolutionary stages of the upper Tairua estuary and the role of floods in its history.

Hand auger cores and vibracores taken along three transects in the upper Tairua Estuary, Coromandel Peninsula. Textural analysis of cores, analysis of diatoms and dating using tephra layers. Model of estuary development presented. 17 hand augers collected from upper estuary from Pauanui (Southern), Pauanui (Middle) and Tairua (Northern) profiles. Chapter 4 contains photographs of vibracores as well as diagrammatic representation of results. Schematic diagrams included as figures in Chapter 4, recording hand auger results. Three transects: 1. Running from the Southern hills to Hikuai Settlement Road 2. Hikuai Settlement Road to the Tairua River 3. Tairua River to the base of the steep catchment hills to the North. Core logs included in Appendix 2.

Upper Tairua Estuary

Data was collected in 2005-2006.

17 hand augers collected from upper estuary three profiles. 1 m long gorge auger, diameter of 1.5 inches. Maximum depth 5 m. Analysis largely undertaken in the field. Sediment grain size observed following Udden-Wenthworth grain size classification scheme and further adjusted using results from vibracores. Colour recorded with reference to Munsell soil colour charts. Three vibracores also collected. 6 m long, 2 inch diameter cable. Core sediments were recorded with attention to texture, unity thickness, structure, colour and organic material. Samples taken for grain size analysis relating to upper, middle and lower extent of each sedimentary unit. Analysed by wet sieving. Sediment analysis used GRADISTAT. Topographic elevation data was collected across the three transects using a total station auto level. All transects tied to local datum in which ellipsoid height was converted to a height above MSL. Tephra marker bed identified in one vibracore and one hand auger was dated using mineralogical analysis and the location of the deposit within the stratigraphic profile. Sediment samples were taken from the vibracores for diatom analysis. Identified diatoms and considered salinity tolerance. Frequency of collection: One-off data collection.

Gaps in collection: n/a

Data reported as core photographs and records in Appendix of thesis.

MSc Thesis, University of Auckland

n/a Sensitivity/Confidentiality: None

Study complete