521 research outputs found

    Timing of initiation of reverse displacement on the Taranaki Fault, northern Taranaki Basin: Constraints from the on land record (Oligocene Te Kuiti Group)

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    Structures associated with the wedge of basement overthrust into Taranaki Basin along the Taranaki Fault, are regarded as hydrocarbon plays and have been tested by drilling through the tip of the overthrust. The timing of initiation of reverse displace ment on Taranaki Fault is difficult to interpret from available seismic reflection data across it because the evidence has been masked by later movements. The record from the basin, as summarised in King & Thrasher (1996), suggests that the fault evolved from normal to reverse character during the mid-Oligocene. This was inferred from formation of a foredeep parallel to, and west of, Taranaki Fault and a marked increase in its paleo-water depth, as indicated by foraminiferal assemblages of Late Oligocene age. A comprehensive re-assessment of the lithostratigraphy and sequence stratigraphy of the Late Eocene-Oligocene Te Kuiti Group exposed on land east of Taranaki Fault in central-western North Island, between Port Waikato and Awakino, provides new constraints on the early history of Taranaki Fault displacement. New age control has been achieved by a review of existing foraminiferal biostratigraphy combined with determination of Sr isotope ages from macrofossil samples. Six unconformity-bound sequences have been identified and mapped within the Te Kuiti Group. A major subaerial unconformity between sequences TK3 and TK4 combined with a basinward shift in the position of onlap for sequence TK4 indicate a dramatic change in stratigraphic development and basin dynamics during the mid-upper Whaingaroan at c. 29 Ma, corresponding to the change from mild extension (sag basin) to shortening across the Taranaki Fault Zone. We consider sequences TK4 – TK6 to each represent tectonic cycles of subsidence and basin inversion and we attribute the origin of these cycles to periodic locking of the Taranaki Fault décollement in underlying Murihiku basement, the accumulating strain causing uplift in the basin east of the fault zone, followed by free displacement, relaxation in the upper crust and subsidence. A 1st order model is presented of the Late Oligocene to earliest Miocene vertical and horizontal displacement of basement on the Taranaki Fault Zone for a west –east transect through Awakino. It implies that the mid- to Late Oligocene displace¬ment on the fault zone in the vicinity of Awakino was episodic, and that the thrust belt was narrow (c. 15 km). North of Kawhia Harbour there will have been a different displacement history with most of the total displacement occurring during the devel opment of the c. 29 Ma unconformity at the base of Sequence TK4, whereas to the south between Awakino and Kawhia Harbour the majority of the total displacement occurred during the Otaian and at the end of it. The model also shows that the start of reverse/thrust displacement on Taranaki Fault must have involved the development of a completely new fault trace(s), rather than involving a change of sense of movement on the pre-existing normal fault. The Manganui Fault is part of the Taranaki Fault Zone and probably became active at c. 27 Ma during development of the unconformity between sequences TK4 & TK5. The model presented here has been validated against the subsurface Oligocene stratigraphy in Taranaki Basin

    Te Kuiti Group (Late Eocene - Oligocene) lithostratigraphy east of Taranaki Basin in central-western North Island, New Zealand

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    This report presents a lithostratigraphy for the Late Eocene - Oligocene Te Kuiti Group that crops out in central-western North Island, New Zealand, between Port Waikato in the north and Awakino in the south. The Te Kuiti Group is a mixed carbonate-siliciclastic succession and includes extensive limestone development in its upper parts. The group is up to several hundred metres thick, and accumulated unconformably above indurated Triassic and Jurassic sedimentary basement. The Te Kuiti Group accumulated east of Taranaki Fault and contains a record of sequence and unconformity development that helps constrain the tectonic development of eastern Taranaki Basin. In particular, it records the timing of the mid-Oligocene transition from extension to crustal shortening. Most of the report is however concerned with rationalisation of the group’s lithostratigraphy to enable the geological signals within it to be inferred

    Stratigraphic columns and correlations for the Late Eocene - Oligocene Te Kuiti Group, central-western North Island, New Zealand

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    This report presents a compilation of stratigraphic columns for geological sections and outcrops of Late Eocene – Oligocene Te Kuiti Group units in central-western parts of North Island, New Zealand, between Port Waikato and Awakino. The columns have been prepared as part of a basin analysis investigation undertaken by the Sedimentary and Petroleum Geology Research Group in the Department of Earth and Ocean Sciences at the University of Waikato, and have been compiled into a common format from recent MSc and PhD theses to make the information more readily available, principally to assist hydrocarbon exploration activities in the region. The columns represent a level of detail underpinning a rationalized lithostratigraphy of the Te Kuiti Group presented in a companion report (Tripathi et al. 2008). This report contains two enclosures, one show in the location of columns in relation to the distribution of the two subgroups (Okoko Subgroup, Castle Craig Subgroup) of the Te Kuiti Group, and the other shows a series of north-south and west-east column correlation panels

    Petrologic evidence for earliest Miocene tectonic mobility on eastern Taranaki Basin margin

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    At Gibsons Beach on the west coast of central North Island, the earliest Miocene (Waitakian) Otorohanga Limestone, the top-most formation in the Te Kuiti Group, is unconformably overlain on an undulating, locally channelised erosion surface by the Early Miocene (Otaian) Papakura Limestone at the base of the Waitemata Group. The basal facies of the Papakura Limestone is a conglomerate composed exclusively of tightly packed pebble- to cobble-sized clasts of skeletal limestone sourced from the underlying Otorohanga Limestone. This petrographic and geochemical study demonstrates that the Otorohanga Limestone was partially lithified during marine and shallow-burial cementation at subsurface depths down to a few tens of metres prior to uplift, erosion and cannibalisation of the limestone clasts into the Papakura Limestone. Strontium isotope dating of fossils from both the Otorohanga and Papakura Limestones at Gibsons Beach yield comparable ages of about 22 Ma, close to the Waitakian/Otaian boundary, indicating very rapid tectonic inversion and erosion of the section occurred in the earliest Miocene. We envisage the clasts of Otorohanga Limestone were sourced from a proximal shoreline position and redeposited westwards by episodic debris flows onto a shallow-shelf accumulating mixed siliciclastic-skeletal carbonate deposits of the Papakura Limestone. Subsequent burial of both limestones by rapidly accumulating Waitemata Group sandstone and flysch instigated precipitation of widespread burial cements from pressure dissolution of carbonate material at subsurface depths from about 100 m to 1.0 km. The vertical tectonic movements registered at Gibsons Beach can be related to the oblique compression associated with the development of the Australian-Pacific plate boundary through New Zealand at about this time and coincide with overthrusting of basement into Taranaki Basin between mid-Waitakian (earliest Miocene) and Altonian (late Early Miocene) times

    Constraints on the evolution of Taranaki Fault from thermochronology and basin analysis: Implications for the Taranaki Fault play

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    Taranaki Fault is the major structure defining the eastern margin of Taranaki Basin and marks the juxtaposition of basement with the Late Cretaceous-Paleogene succession in the basin. Although the timing of the basement over-thrusting on Taranaki Fault and subsequent marine onlap on to the basement block are well constrained as having occurred during the Early Miocene, the age of formation of this major structure, its character, displacement history and associated regional vertical movement during the Late Cretaceous- Recent are otherwise poorly known. Here we have applied (i) apatite fission track thermochronology to Mesozoic basement encountered in exploration holes and in outcrop to constrain the amount and timing of Late Cretaceous-Eocene exhumation of the eastern side of the fault, (ii) basin analysis of the Oligocene and Miocene succession east of the fault to establish the late-Early Miocene - Early Pliocene subsidence history, and (iii), regional porosity-bulk density trends in Neogene mudstone to establish the late uplift and tilting of eastern Taranaki Basin margin, which may have been associated with the main period of charge of the underlying Taranaki Fault play. We make the following conclusions that may be useful in assessing the viability of the Taranaki Fault play. (1) Mid-Cretaceous Taniwha Formation, intersected in Te Ranga-1 was formerly extensive across the western half of the Kawhia Syncline between Port Waikato and Awakino. (2) Taranaki Fault first formed as a normalfault during the Late Cretaceous around 85±10 Ma, and formed the eastern boundary of the Taranaki Rift-Transform basin. (3) Manganui Fault, located onshore north of Awakino, formed as a steeply east dipping reverse fault and accommodated about four km of displacement during the mid-Cretaceous. (4) Uplift and erosion, involving inversion of Early Oligocene deposits, occurred along the Herangi High during the Late Oligocene. This may have been associated with initial reverse movement on Taranaki Fault. (5) During the Early Miocene (Otaian Stage) the Taranaki and Manganui Faults accommodated the westward transport of Murihiku basement into the eastern margin of Taranaki Basin, but the amount of topography generated over the Herangi High can only have been a few hundred metres in elevation. (6) The Altonian (19-16 Ma) marked the start of the collapse of the eastern margin of Taranaki Basin that lead during the Middle Miocene to the eastward retrogradation of the continental margin wedge into the King Country region. During the Late Miocene, from about 11 Ma, a thick shelf-slope continental margin wedge prograded northward into the King Country region and infilled it (Mt Messenger, Urenui, Kiore and Matemateaonga Formations). (7) During the Pliocene and Pleistocene the whole of central New Zealand, including the eastern margin of Taranaki Basin, became involved in long wavelength up-doming with 1-2 km erosion of much of the Neogene succession in the King Country region. This regionally elevated the Taranaki Fault play into which hydrocarbons may have migrated from the Northern Graben region

    Lithofacies, paleoenvironments and elements of sequence architecture, Late Oligocene - earliest Miocene Castle Craig Subgroup (Te Kuiti Group), Waikato-King Country Basin, New Zealand

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    This report presents a comprehensive facies and sequence stratigraphic analysis of the Late Oligocene Castle Craig Subgroup (Orahiri Formation and Otorohanga Limestone) within the Late Eocene – Earliest Miocene Te Kuiti Group in the Waikato-King Country Basin in central-western North Island, New Zealand. Detailed field investigations have identified 12 lithofacies within the Castle Craig Subgroup, which have been grouped into three lithofacies associations named limestone, mixed carbonate-siliciclastic sandstone, and siliciclastic sandstone after the dominant lithologies. In areas south of Aotea Harbour the subgroup comprises a wide variety of limestone types with variable siliciclastic content, dominated by coarse skeletal rudstone/grainstone, with aggregate stratigraphic thicknesses of up to 100 m. These sediments accumulated at shelf depths in a moderate to highenergy tidal seaway. Around Raglan Harbour and in areas to the north, the subgroup comprises predominantly planktic foraminiferal-rich packstone to wackestone and calcareous siltstone/marl that accumulated mainly in slope/upper bathyal settings

    Lithofacies, paleoenvironments and sequence stratigraphy of the Late Oligocene Aotea Formation (Te Kuiti Group), central-western North Island, New Zealand

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    This report presents a comprehensive facies and sequence stratigraphic analysis of the Late Oligocene Aotea Formation within the Late Eocene – Earliest Miocene Te Kuiti Group in the Waikato-King Country Basin in central-western North Island, New Zealand. The Aotea Formation is a mixed carbonate-siliciclastic succession with four facies associations: limestone (Waimai Limestone Member), calcareous sandstone (Hauturu Sandstone Member, Kihi Sandstone Member), calcareous siltstone (Patikirau Siltstone Member) and chemogenic facies (upper parts of Kihi Sandstone Member, Patikirau Siltstone Member and Waimai Limestone Member). Theses facies are established from field descriptions supplemented by laboratory textural and petrographic data and are inferred to have accumulated in different sectors of a shelf environment. The Aotea Formation comprises one sequence for which key surfaces and systems tracts are described and interpreted. The lower sequence boundary is a wave-planed surface. It, together with the subsequent onlap deposits represent a marked basinward shift in the position of coastal onlap arising from basin inversion focussed along the western margin of the basin, followed by marked subsidence in the northern part of the basin

    Facies analysis and sequence stratigraphy of Early Oligocene Glen Massey Formation (Te Kuiti Group), Waikato - King Country Basin, New Zealand

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    This report presents a comprehensive facies and sequence stratigraphic analysis of the Early Oligocene Glen Massey Formation, one of eight formations within the Late Eocene to earliest Miocene Te Kuiti Group in the Waikato-King Country Basin in central-western North Island, New Zealand. The Glen Massey Formation is a mixed carbonate-siliciclastic succession with three main facies associations: limestone (Elgood Limestone Member), calcareous siltstone (Dunphail Siltstone Member) and calcareous sandstone (Ahirau Sandstone Member). These facies, established from field descriptions supplemented by laboratory textural and petrographic data, accumulated in a continental shelf setting above coal measure and marginal marine units in basal Te Kuiti Group or above the Mesozoic basement rocks along the eastern margin of Taranaki Basin. The formation comprises one sequence for which key surfaces are identified and described and used to establish the extent of systems tracts, representing different parts of a relative sea-level cycle. A model sequence shows the distribution of facies within systems tracts in a cross-shelf profile

    Biostratigraphy, Sr isotope chronology and chronostratigraphy of the Late Eocene – earliest Miocene Te Kuiti Group, Waikato – King Country Basin, New Zealand

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    This report reviews and synthesises the biostratigraphy of the Te Kuiti Group based on existing sample data archived in the Fossil Record Electronic Database (FRED). Based on these faunal and floral data, New Zealand biostratigraphic stages for the Late Eocene to Early Miocene are assigned to the formations and members within the group. Analytical strontium (Sr) data and resulting numerical ages are reported here for 26 new macrofossil samples from the Te Kuiti Group, but they do not improve the accuracy of the biostratigraphy and the age information that can be derived from it. The identification of unconformity-bound sequences, the boundaries of which align with the formation contacts within the group, provide an important set of time planes within the group. The integration of the biostratigraphy and sequence stratigraphy produces a robust chronostratigraphy for the Te Kuiti Group

    Electro-osmotic flow of couple stress fluids in a microchannel propagated by peristalsis

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    A mathematical model is developed for electro-osmotic peristaltic pumping of a non-Newtonian liquid in a deformable micro-channel. Stokes’ couple stress fluid model is deployed to represent realistic working liquids. The Poisson-Boltzmann equation for electric potential distribution is implemented owing to the presence of an electrical double layer (EDL) in the micro-channel. Using long wavelength, lubrication theory and Debye-Huckel approximations, the linearized transformed dimensionless boundary value problem is solved analytically. The influence of electro-osmotic parameter (inversely proportional to Debye length), maximum electro-osmotic velocity (a function of external applied electrical field) and couple stress parameter on axial velocity, volumetric flow rate, pressure gradient, local wall shear stress and stream function distributions is evaluated in detail with the aid of graphs. The Newtonian fluid case is retrieved as a special case with vanishing couple stress effects. With increasing couple stress parameter there is a significant elevation in axial pressure gradient whereas the core axial velocity is reduced. An increase in electro-osmotic parameter induces both flow acceleration in the core region (around the channel centreline) and also enhances axial pressure gradient substantially. The study is relevant to simulation of novel smart bio-inspired space pumps, chromatography and medical microscale devices
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