Abstract:
Turbidite systems make up a significant component of the stratigraphic record and host some of the worlds most important hydrocarbon reservoirs. Ancient turbidite deposits are exposed worldwide in cliff faces and beaches, as is the case with the Miocene Waitemata Group rocks, which were deposited within the Miocene Waitemata Basin. This thesis presents detailed fieldwork conducted at the type section of the Pakiri Formation north of Auckland, along with hydraulic flume experiments. The aims of this thesis were to re-examine the Pakiri Formation type section in terms of flow processes and environment of deposition, to conduct flume experiments to show how an unconfined basin evolves in terms of sediment deposition and flow characteristics, when using different sediment:water ratios, and to compare and contrast field and experimental methods, and determine their effectiveness when modelling a turbidite system. Detailed mapping and sedimentary logging was undertaken in the field, along with rock sampling and the measurement of paleocurrents. Rock samples were studied microscopically via thin sections, along with XRD analysis to determine the dominant mineralogy. These investigations indicated that the environment of deposition was within a marine intraslope basin between 700-1200m water depth. Following on from the fieldwork, hydraulic flume experiments were conducted in a 2m by 2.42m unconfined flume with a false floor, using varying sediment concentrations and sand:mud ratios to recreate the processes that may have deposited the rocks found in the field area. These experiments demonstrated the controls that concentration has on flow velocity and deposit thickness, as well as how deposits vary with distance from the source, and the importance of having varying sediment sizes within a flow. Upon comparison of these two different methods of turbidite research, it was found that although the flume experiments were not able to model turbidity currents and turbidites to the degree that they are seen in nature, important information can be gained by comparing the two methods, such as the importance of bedding and structure preservation within a deposit, the difficulties of log correlation and the effects that proximity has on a deposit.