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Taranaki Basin (New Zealand) contains a Late Cretaceous – Cenozoic sedimentary succession up to 9 kilometres thick. Neogene strata are volumetrically a significant part of the basin fill. During the late-Middle Miocene a new sediment source, arising from the onset of uplift and erosion of the Southern Alps mountain belt, supplied the basin with copious sediment, continuing to the Recent. This resulted in the development of a northwestward prograding shelf-slope wedge within the basin. The Moki and Mount Messenger formations accumulated as sandstone strata within mudstone (Manganui Formation) and display obvious sediment conduits (i.e. canyons, channels and gullies) in seismic reflection profiles. Past studies considered that these conduits pass through submarine fans, while in reality fans occur basinward of the mouths of the sediment conduits. This thesis study leverages seismic reflection data and applies seismic stratigraphy and seismic geomorphology, integrated with analysis of wireline logs, core, and outcrops, to better understand the occurrence of sediment conduits and fans within the Moki and Mount Messenger formations. Results show that in southern Taranaki Basin, increased sediment influx resulted in steepening of the continental slope, changing the morphometrics of sediment conduits. Critical analysis of data generated here forced the dismissal of all published fans associated with these sandstone formations. Rather, two new Late Miocene submarine fans have been mapped in deep-water western Taranaki Basin towards the head of the New Caledonia Basin. New paleogeographic maps for the Middle and Late Miocene have been drawn that display the sediment conduits and new fans.

Tectonic plates subducting at trenches having strikes oblique to the absolute subducting plate motion undergo trench-parallel slab motion through the mantle, recently defined as a form of “slab dragging.” We investigate here long-term slab-dragging components of the Tonga-Kermadec subduction system driven by absolute Pacific plate motion. To this end we develop a kinematic restoration of Tonga-Kermadec Trench motion placed in a mantle reference frame and compare it to tomographically imaged slabs in the mantle. Estimating Tonga-Kermadec subduction initiation is challenging because another (New Caledonia) subduction zone existed during the Paleogene between the Australia and Pacific plates. We test partitioning of plate convergence across the Paleogene New Caledonia and Tonga-Kermadec subduction zones against resulting mantle structure and show that most, if not all, Tonga-Kermadec subduction occurred after ca. 30 Ma. Since then, Tonga-Kermadec subduction has accommodated 1,700 to 3,500 km of subduction along the southern and northern ends of the trench, respectively. When placed in a mantle reference frame, the predominantly westward directed subduction evolved while the Tonga-Kermadec Trench underwent ~1,200 km of northward absolute motion. We infer that the entire Tonga-Kermadec slab was laterally transported through the mantle over 1,200 km. Such slab dragging by the Pacific plate may explain observed deep-slab deformation and may also have significant effects on surface tectonics, both resulting from the resistance to slab dragging by the viscous mantle.

We collected palaeomagnetic sample sets from Murihiku Terrane, North Island to constrain its palaeolatitude during the Late Triassic–Jurassic. The majority of the sample host rocks were remagnetised. However, a few samples show a magnetic signal that possibly recorded a primary remanent magnetisation. These samples preliminarily indicate that Murihiku Terrane was located at c. 63°S during the Early Jurassic. The remagnetised samples reveal significant post-remagnetisation tectonic rotation and tilting of the host rocks. We estimated an 83 ± 5 Ma timing of remagnetisation by plotting the palaeolatitude data on the apparent polar wander path of northern Zealandia. Samples from southernmost sites have lower inclination, which we interpret as reflecting eastward post-remagnetisation tilt of this region by 20°. In addition, declination data indicate large-scale post-remagnetisation rotation of Port Waikato and Awakino Gorge areas. This study contributes to the ongoing debate on the age and tectonic origin of oroclines in New Zealand basement.

The Late Eocene - Oligocene Te Kuiti Group crops out extensively in central-western North Island between Port Waikato and Awakino, providing a useful window for examination of a broadly transgressive shelfal to upper bathyal mixed carbonate-siliciclastic basin fill succession. The group accumulated during initiation of Cenozoic glaciations on Antarctica when there may have been associated eustatic changes in sea- level changes, and during the initiation of the Australia-Pacific plate boundary through the New Zealand region, which might also have caused relative changes in sea level in the Waikato Basin. As part of this study Te Kuiti lithostratigraphy in central-western North Island has been reviewed and rationalized. Special emphasis has been given to correlation of the significant stratigraphic discontinuities (erosional unconformities, depositional hiatuses) between units. Combined with a review of the foraminiferal biostratigraphy and new Sr isotope ages for the group, lithologically diverse formations have been able to be correlated across and along the outcrop belt. In the revised stratigraphic scheme, seven formations and 24 members of Kaiatian to Waitakian (Late Oligocene to Early Miocene) age are identified. The Te Kuiti Group is subdivided into two subgroups, a lower Okoko Subgroup, and an upper Castle Craig Subgroup. The Okoko Subgroup is dominated by calcareous siltstone and sandstone members, with limestone members commonly occurring at the base of formations, whereas the Castle Craig Subgroup is almost entirely comprised of limestone in the south and by calcareous siltstone in the northern parts of the basin. Six unconformity-bound sequences (TK1 - TK6) have been identified and mapped within the Te Kuiti Group using sequence stratigraphic principles. For several of these sequences (TK2, TK4, TK5 TK6) detailed facies and sequence analyses have been undertaken based on field characteristics, complemented with laboratory grain size and compositional (carb

Hawke's Bay province lies within an extensive forearc basin in eastern North Island, New Zealand, that developed during the Late Miocene to present. An area of about 5 700 kmsup2; in central Hawke's Bay has been geologically mapped at 1:50 000 scale as part of an analysis of the Late Miocene-Early Pleistocene basin fill. A substantially revised lithostratigraphic nomenclature is proposed for the Neogene succession, particularly for the latest Miocene-Early Pleistocene part (Mangaheia Group). The Tolaga Group is extended into central Hawke's Bay from the north, and incorporates the Early Miocene-Early Pliocene succession. It is proposed that the Hawke's Bay, Petane, Napier, and Poporangi Groups be abolished, and incorporated into a geographically expanded Mangaheia Group. The Petane Group is demoted to Petane Formation. Most formations within the group are now redefined as members, with the exceptions of the Esk Mudstone and Kaiwaka Formations, which are retained as separate formations. An age model has been developed for the basin fill, chiefly using molluscan biostratigraphy. The Tongaporutuan-Kapitean boundary occurs in the Waitere Formation, and the Kapitean-Opoitian boundary occurs within the Mokonui Sandstone. The Opoitian-Waipipian boundary probably occurs in the Titiokura Formation, and the Waipipian-Mangapanian boundary in the Te Waka and Pohue Formations. The Mangapanian-Nukumaruan boundary has been identified at many localities, and occurs in several stratigraphic units, including the Papakiri Member (Matahorua Formation) and Sentry Box Formation. Geochemical analysis of glass shards in the Hikuroa Pumice Member (Petane Formation) suggests a correlation to tephra in the ODP 1124 record, and an inferred age of c. 2.15 Ma is suggested for this unit. The Plio-Pleistocene boundary is located in the Waipatiki Limestone Member (Petane Formation), and the top of the Olduvai paleomagnetic subchron occurs in the overlying Devils Elbow Mudstone Member. The geologica

Using high-resolution suites of core samples, including 940 samples from Deep Sea Drilling Project (DSDP) Site 593 in southern Tasman Sea off western New Zealand, and 353 samples from Ocean Drilling Program Site 1123 in the Southwest Pacific Ocean off eastern New Zealand, this study documents for the late Miocene interval (about 11.6 to 5.2 million years ago) the nature and abundance of planktic foraminifers in these uncomplicated and virtually uninterrupted oceanic sequences. The discovery and documentation of bolboforms at both sites - an enigmatic group of marine calcareous protophytes new to New Zealand - has enabled a highly-refined and integrated planktic foraminiferal and bolboform zonation to be established with 69 well-defined biostratigraphic events - highest and lowest occurrences, acme zones, and coiling zones - that are potentially useful for the correlation and subdivision of the late Miocene in New Zealand. It has also enabled these bioevents to be correlated with the excellent paleomagnetic record at ODP Site 1123 (Wilson et al. in prep.) and age calibrated directly or indirectly with the geomagnetic polarity time scale GPTS-95 (Cande & Kent 1995). This represents a major advance in New Zealand late Miocene biostratigraphy and biochronology and it is the first time a robust late Miocene chronology has been developed entirely from local data. The study also links the major microfossil bioevents established in the offshore records at Sites 593 and 1123 back into selected onland New Zealand sections (730 samples), where the late Miocene is rather poorly resolved, thereby improving our ability to date, correlate, and interpret the paleoceanographic significance of late Miocene events more widely. Reassessment of faunal criteria used for the operational recognition and correlation of the late Miocene Tongaporutuan Stage in onland New Zealand, shows that the current defining faunal criterion for the base of the stage, the lowest occurrence of benthic foram

The Pliocene-Pleistocene Giant Foresets Formation represents the progradation and development of the modem continental margin in northern Taranaki Basin. The dynamic evolution of this formation is fundamentally linked to a Pliocene-Pleistocene increase in sediment flux sourced from South Island, to extensional graben formation in northern Taranaki Basin, to flexural subsidence in Wanganui Basin, and to uplift and erosion in King Country Basin. The development of the Giant Foresets Formation is summarised in this thesis by a series of paleogeographic maps based on the interpretation of wireline data from hydrocarbon exploration holes, industry-acquired seismic reflection data, and the paleoenvironmental interpretation of foraminiferal data derived from well cuttings samples. Outbuilding of the modem continental shelf-slope margin began during the Early Miocene as the regressive phase of a 1ˢᵗ-order megacycle. Four 2ⁿᵈ-order cycles superimposed on this megacycle have been identified in Taranaki, Wanganui and King Country Basins. The evolution of the Giant Foresets Formation is closely linked to the youngest two megacycles: the Mid Miocene-earliest Pliocene Whangamomona Group/megacycle, and the mid Pliocene-Pleistocene Rangitikei Supergroup/megacycle. The Whangamomona Group includes the Otunui, Mount Messenger, Urenui and Kiore Formations. The continental margin associated with the Whangamomona Group had only limited extent in southern and eastern parts of Taranaki Basin. The Rangitikei Supergroup in Wanganui Basin includes the Tangahoe Mudstone and younger Plio-Pleistocene sediments. The Giant Foresets Formation represents the Rangitikei Supergroup in northern Taranaki Basin. Revision of the biostratigraphy of four well sections, and integration with biostratigraphic data from other well sections, has highlighted the development in northern Taranaki Basin of a region-wide unconformity between Miocene (Late Tongaporutuan to Late Kapitean) and Pliocene (Early to mid Opo

Among carbonate sedimentologists, it is now appreciated that shallow-marine carbonates are not restricted to warm-water tropical settings, but can also be produced on modern cool-water shelves outside tropical latitudes. In the last two decades, many publications have not only advanced our knowledge about modern non-tropical carbonates, but have documented ancient skeletal limestones that are fossil analogues of these modern deposits. While the broad environmental and sedimentary characteristics of non-tropical deposits are becoming well established, the nature, timing, and relative importance of the various diagenetic processes affecting their evolution into limestones are yet to be fully appreciated, a topic addressed in the present study. In New Zealand, the Plio-Pleistocene (5-1.5 Ma) Te Aute limestones in southern Hawke’s Bay (eastern North Island) are non-tropical in origin, and formed in shoal areas about the margins of a forearc basin seaway adjacent to the convergent Pacific-Australian Plate boundary. Because of the dynamic tectonic setting, which led to narrowing and shallowing of the host basin over time, the studied carbonates exhibit a variety of sedimentary facies (i.e., from pure coquina to mixed carbonate-siliciclastic) and mineralogical signatures (i.e., calcite- to, more rarely, aragonite-dominated), and have undergone varying degrees of burial before being uplifted to their present position. As such, the Te Aute deposits provide a unique opportunity to: (1) decipher the suite of processes that have altered their texture and composition through time; (2) address the questions of what likely regional and more global parameters, namely tectonics and eustasy, may have driven diagenetic pathways, and how this occurred; and (3) more generally advance fundamental knowledge about models of porosity evolution in non-tropical carbonates. The present study integrates the combined results of detailed field investigations with a variety of analytical technique

The tectonic evolution of the Marlborough region has been studied by application of fission track thermochronology and finite element (FE) methods. The region lying within the Australian-Pacific plate boundary zone is considered to have a transcurrent fault system, known as the Marlborough Faults System (MFS). The MFS is viewed as comprising secondary transforms connecting the Hikurangi subduction margin with the main Alpine Fault oblique-slip boundary. This fault system appears to have developed sequentially towards the southeast during the past 5 million years. Consequently, the subducted Pacific plate has extended beneath the region. The FE modelling results reveal that the accommodation percentage of total displacements in Marlborough is about 85% of the total plate motion. The instantaneous displacements of the Marlborough faults show successively increase to the southeast away from the Wairau Fault. The contour of instantaneous displacements estimated by the FE modelling can be compared to the topography of Marlborough. According to the results of the FE modelling cases, the main conclusions drawn are: (1) A curved fault (the Alpine Fault) resulted from a change in the plate motion vector and is a manifestation of dextral tectonic rotation. (2) The development of the MFS reflects the continuation of tectonic rotations. (3) Three secondary faults (Awatere, Clarence, and Hope) may have developed within a short period of one another. This suggests that the change in plate motion has impacted in Marlborough. (4) Uplift movements of the Spenser Mountains and Kaikoura Ranges still continue. (5) Suggate’s model (1979) of a pre-existing fault offset of the Alpine Fault is not a unique result in the FE modelling. The extremely young fission track ages (<10 Ma) in the vicinity of the Alpine Fault bend and Seaward Kaikoura Range coincide with the recent rapid uplift/erosion in these areas. All the apatite ages are less than the corresponding depositional ages of the samp