The active Orakeikorako-Te Kopia geothermal system was drilled in the mid-1960’s, down to 1405m, as part of a programme to investigate its electrical generation capability. Four wells were completed at Orakeikorako (23km NNE of Taupo) and two at Te Kopia, 9.5km further northeast. The exploration drilling provided information on the present day hydrological and thermal regime which is as hot as 265°C (1137m drilled depth (-801m RL) in OK-2). Major flows into the wells occurred at depths down to 850m, although poor permeability and decline in mass output discouraged development. The waters discharged were of near neutral pH and had low salinities (highest Cl content from OK-2 ≈546mg/kg), low discharge enthalpies and indicated water temperatures (TSiO2 and TNaKCa) of 2l0°C to 240°C. A hydrologic model proposed here envisages a hot water reservoir in the OK-2 area (northeastern part of the Orakeikorako thermal area) with a lateral flow supplying water to the Red Hill (OK-4 area) in the southern part of the system and a concealed northeast flow which reaches the surface at Te Kopia. The Orakeikorako thermal area occupies a surface area of about 1.8km2, mainly on the east bank of the Waikato River, where dilute chloride-bicarbonate water discharges along faults and fractures in association with an extensive silica sinter sheet, boiling springs and geysers. The occurrence of a mordenite-smectite assemblage at shallow depths, plus the oxygen and hydrogen isotopic composition of surface discharge waters, indicate that the ascending chloride fluids are diluted by near surface (heated?) groundwaters. The δD shift from local groundwater composition may be evidence for a magmatic component to the convecting hydrothermal system. Incursion of fluids from the relatively cool (<l20°C) steam-heated carapace into deep levels of the system and its mixing with the alkali-chloride fluids, produces argillic alteration, sealing and will eventually result in the demise of the system. Old silica sinter on the west bank, at the foot of the Tutukau Rhyolite Dome, is covered by Oruanui Ash (22,700 years B.P.) and demonstrates that the hydrologic character of this part of the system has changed due to a combination of fault movement, changes in the height of the watertable and sealing. The Te Kopia thermal area is located along 2.5km of the Paeroa Fault scarp, a major structural feature inferred to be controlling migration of deep hydrothermal fluids in the Orakeikorako-Te Kopia area. Surface activity at Te Kopia is characterised by acid alteration (including fumaroles, warm acid pools and steaming ground), although neutral pH alkali-chloride fluids discharged here within the last 3000 years and deposited silica sinter (C14 age on wood enveloped by sinter is 3026 +/- 43years B.P.). New thermal areas in the past --year have begun to develop in the northwestern part of Te Kopia, whilst cold hydrothermally altered ground (hosting a mordenite + clay assemblage) records a decline in activity in the southern part of the Te Kopia thermal area. The system is hosted by a generally SE dipping sequence of Pliocene to Quaternary ignimbrite, tuff and rhyolite lavas of the Taupo Volcanic Zone. Point counting, electron microprobe analyses of surviving primary phases (Fe, Mg, Al and Ti contents of hornblende and biotite), together with X-ray fluorescence and neutron activation analysis were used to distinguish three extensive ignimbrites encountered in the Orakeikorako-Te Kopia drillholes: (0.33Ma, sanidine-bearing) Paeroa, (0.35Ma) Te Kopia and (undated) Akatarewa Ignimbrites, despite their having been hydrothermally altered. Ignimbrite recognition is made on the basis of a combination of immobile trace and rare earth element abundances and ratios: Ta and Yb (ppm), P2O5(%) and the ratios Zr/Yb, Zr/Y, Yb/Hf, La/Lu, Nb/Hf, Zr/Nb, Zr/Lu, Yb/Ta, Ta/Lu, La/Tb and Nb/Ta. The Paeroa Ignimbrite is distinguished by is Eu anomaly ((Eu/Eu*)cn is 0.48 to 0.54), whereas the Te Kopia and Akatarewa Ignimbrites are characterised by their flatter REE Spidergrams ((Eu/Eu*)cn is ~1.0 and ~0.8 respectively). The correlation of the extensive ignimbrites was satisfactorily effected by a combination of their characteristic bulk rock and pumice chemistry, plus primary mineralogy, to enable the subsurface stratigraphy and structure of the Orakeikorako-Te Kopia geothermal system to be defined. The alteration assemblage below 500m consists of quartz, albite+adularia, with variable abundence and distribution of chlorite, pyrite, calcite, wairakite, epidote, pyrrhotite, titanite, leucoxene, siderite and clinozoisite; illite is a late overprint. Rare almandine occurs in rhyolite in OK-1: 1312.5m; this is the first known occurrence of garnet in an active geothermal system of the TVZ. The surficial alteration assemblage of kaolin, cristobalite, alunite, hematite and jarosite reflects alteration by acid sulphate-steam heated waters. The occurrence and textual relations exhibited by the hydrothermal mineral assemblage define the geochemical structure and thermal evolution of the Orakeikorako-Te Kopia system The activities of components of minerals, determined from electron microprobe analyses and composition-activity relationships (OK-2 discharge: logαK+/αH+=3.6, logαNa+/αH+=4.8) support the petrologic observation that illite is now the stable potassium phase (overprinting adularia), although a state of equilibrium between the sheet silicate and the fluids is clearly not fully reached. The Na/K ratio of the altering fluid is controlled by the albite-adularia reaction (dissolution of albite and replacement by adularia, after andesine), whilst the H2/H2S ratio is buffered by the virtually complete replacement of pyrrhotite by pyrite. The fluids are now slightly undersaturated with respect to calcite, this is shown by etched surfaces on some calcite grains. In the past the deep fluid boiled adiabatically from >300°C to ~250°C as it ascended, resulting in the deposition of adularia, quartz and bladed calcite. The system has cooled, resulting in lower subsurface temperatures (as recorded by fluid inclusion geothermometry) suppressing boiling, and migrated northwards as a consequence of self sealing. The thermal decline and retention of CO2 in the deep alkali-chloride fluid shifted the alteration assemblage from one of albite-adularia stability to illite stability. The homogenisation (Th) temperatures of primary and secondary liquid-rich inclusions in 27 cores from different depths mostly match measured temperature profiles (e.g. OK-1 (shallow levels) and OK-2). Never-the-less, fluid inclusion data support mineral-inferred stability temperatures which indicate that parts of the Orakeikorako-Te Kopia system have cooled appreciably (e.g. OK-1, deep levels) and OK-4 (maximum Tbore=238°C, maximum Th=312°C; epidote abundant). In contrast, the northwestern margin (OK-6 area) has heated (OK-6:1113.4m; Tbore=261°C, Th=210-221°C). Some inclusions in the Te Kopia drillholes have Th values that exceed Tbore by as much as 50°C, and are deduced to have been uplifted by movement on the Paeroa Fault. Freezing data indicate that the trapped fluid was dilute (~0.2 to 1.7 wt% NaCl equivalent) since most Tm values range from -0.1 to -0.5°C. The outflow portion of the Orakeikorako-Te Kopia system has evolved recently, both chemically and physically. Movement on the Paeroa Fault, that uplifted pyroclastic rocks hosting a quartz-adularia-illite assemblage, combined with a lowering of the watertable has resulted in an overprinting of the neutral pH hydrothermal mineral assemblage by a kaolinite-alunite type assemblage which derives from an acid sulphate fluid. Quartz crystals found 150m above the base of the Paeroa Fault scarp host dilute (~1.5wt% NaCl equivalent) fluid inclusions with Th values that range from 180-206°C (average 196°C). Bladed quartz (after calcite) did not contain usable inclusions. It is deduced that the inclusions formed about 120-160m below the ground, which indicates uplift in the order of ~300m. Assuming a constant rate of uplift of 4m/ka (based on the offset of 330ka Paeroa Ignimbrite), the minimum duration of activity at Te Kopia is 75,000 years.

Extensive beach and dune deposits of titanomagnetite sands occur along the west coast of the North Island of New Zealand. Some of the larger deposits cover an area of greater than 10 km2, with a thickness greater than 50 metres. Deposits at Taharoa, Waikato North Head and Raglan were investigated to determine whether geophysical methods can be used to delineate titanomagnetite concentration patterns within the deposits and also to assess the total reserves of titanomagnetite in each deposit. Laboratory measurements showed that the magnetic susceptibility of the sands increases monotonically with the volume concentration of magnetite CV; the observed variation of magnetic susceptibility as a function of CV can be explained by changes in the resultant magnetic permeability of a binary mixture of magnetic and non-magnetic grains. The density of the sand increases linearly with CV; the particle density of titanomagnetite is 4.7 x 103 kg m-3. The natural remanence of magnetite sands is small (Koenigsberger ratio Q<0.2). No significant induced polarization response could be observed even for mixtures of almost pure magnetite. When placed in an electric field, the magnetite sands were found to be non-conductive. Field measurements showed that total magnetic force anomalies with peak values of up to 1600 nT and 800 nT could be observed over the deposits during aeromagnetic surveys at elevations of 183 m and 366 m respectively. Topographic anomalies were subtracted from the observed data, assuming an average concentration of 18% magnetite for sands in the deposits dawn to an arbitrary datum level. The resulting residual anomalies are caused entirely by sand which is enriched in magnetite (commonly up to 45% to 50% by weight). At Taharoa, the enriched sands were modelled by a 33 x 13 array of vertical prisms (200 m x 200 m dimension), retaining the length and magnetization of each prism as parameter. At Waikato North Head and Raglan, the enriched sands were modelled by three-dimensional polygonal bodies. Ground magnetic studies are suitable for outlining particular magnetite concentration patterns, such as in streams or on beaches. Magnetite concentration patterns Rave gravitational effects of up to ±1 mgal, which are distorted by interfering gravitational effects from basement structures at Taharoa and by a strong regional gradient at Waikato Heads. However, the gravity data at Taharoa could be interpreted in terms of basement depths, whereas at Waikato North Head, gravity anomalies outline magnetite-enriched sub-deposits which occur below sea level. Concentration patterns above sea level at Waikato North Head could not be accurately defined from the gravity data. Seismic refraction studies showed that the Taharoa deposit is up t o 200 m thick. The seismic velocity in the drifting surface sands increases linearly with depth, from a surface velocity of 0.24 km sec-1 to a maximum of 0.65 km sec-1, with a rate of increase varying from 19 to 30 sec-1. These sands are underlain by a weakly cemented, homogeneous sand unit which has a velocity of 1.7 ± 0.1 km sec-1 and has a titanomagnetite concentration of less than 18% by weight. The two sand members are separated by a sequence of tephras and paleosols. Values of DC-resistivity observed over the deposits exceed 104 ohm-m in dry sand and are as low as 102 ohm-m in saturated clay- bound sands. Small frequency effects of up to 14% were observed in clean sands at Taharoa. Magnetite sand deposits can be successfully prospected by geophysical methods. Airborne magnetic surveys are most applicable; a flightline spacing of 0.5 km allows magnetite concentration patterns with wavelengths greater than 200 m to be resolved. The seismic refraction method delineates the vertical extent of the deposits. Gravity, ground magnetic and electrical methods can be used to test specific objectives. Electromagnetic methods were found to be unsuitable for the prospecting of ironsand deposits. Ore reserves of magnetite calculated from the interpretation of the geophysical data were found to be significantly greater than previous estimates. At Taharoa, a total mass of 545 x 106 tonnes of enriched sand with an average magnetite concentration of 38% was calculated from geophysical data. Three major and three minor sub-deposits of enriched sands, containing a total of 580 x 106 tonnes with an average concentration of 46% magnetite are indicated from similar data at Waikato North Head; of these, two major sub-deposits, which occur below Sea level and which contain 230 x 106 tonnes of sand (114 x 106 tonnes of magnetite) were not previously known. The ore reserves at Raglan amount to 56 x 106 tonnes with an average concentration of 36% titanomagnetite. As well as the enriched sands, all three deposits also contain large reserves of low-grade magnetite sand. It is postulated that a large proportion of the magnetite sands which have accumulated along the west coast of the North Island may have been derived from the erosion of extensive Quaternary tephra sheets which originated from numerous centres in the Central Volcanic Zone.

The fossil Cirripedia : Thoracica of Australia and New Zealand have been studied. One hundred and three taxa are now known as fossil, and these are systematically described and illustrated. A number of major systematic revisions are proposed, including 1 new superfamily, 6 new subfamilies, 7 new genera, 2 new subgenera and 52 new species or subspecies. The material studied has revealed inconsistencies in the presently held views on phylogeny. Amongst the Balanomorpha, the Balanidae are shown to have evolved from a new six-plated archaeobalanid (with a tripartite rostrum), rather than Hexelasma; and in the Lepadomorpha, Arcoscalpellum is revised, and a new genus, which gave rise to many modern arcoscalpellids, is proposed. The difficulties in assigning the more primitive representatives of families to generic level are discussed, and keys are introduced to facilitate identification. The study also identifies many taxa with restricted time ranges, illustrating the stratigraphic importance of cirripeds. Thoracican ecology is discussed, and it is shown that early taxa preferred the shallower upper shelf environment; but following an explosive evolutionary radiation during the Lower Cenozoic, a great diversity of habitats became occupied. Neogene species especially, can be of considerable importance in paleoecology, both as indicators of depth and temperature. Faunal relationships are discussed in the light of new advances in plate tectonics. An early association between Australia and New Zealand can be recognised, and this is followed in the Neogene by the development of a South American fauna with distinct Australasian influences. Laboratory techniques, including thin section analysis and scanning electron microscopy are discussed with relevance to their use in identification. Charts showing both the stratigraphic and lithologic distribution of the known fossil Thoracica of Australasia are included.

This is the first study of cretaceous or Paleogene Radiolaria from on-land New Zealand. It is based on five Late Cretaceous to Paleocene sections within the Amuri Limestone Group of eastern Marlborough (NE South Island): Woodside Creek, Wharanui Point, Chancet Rocks, Flaxbourne River and Mead Stream. Faunas from coeval sediments at DSDP Site 208 (Lord Howe Rise, north Tasman Sea) are also reexamined. Because diverse and well-preserved radiolarian faunas are common, the location of the Cretaceous/Tertiary (K/T) boundary well-documented, and the earliest Paleocene relatively complete, these sections provide the most complete known record of radiolarian evolution from latest Cretaceous to mid Late Paleocene (c.70-60 Ma). Systematic treatment of K-T transitional faunas was hampered by a dichotomy between Cenozoic and Mesozoic methodologies and nomenclature. To resolve this schism, broad taxonomic definitions are adopted, numerous synonymies are identified, and several revised definitions are proposed for established taxa. Of the 94 taxa recorded, 65 are species or species groups, and 29 are undifferentiated genera or higher level categories. Three new species are described: Amphisphaera aotea n.sp., A. kina n.sp. and Stichomitra wero n.sp. A new latest Cretaceous to mid Late Paleocene zonation is proposed. Six new interval zones are defined by the first appearances of the nominated species. In ascending order these are: Lithomelissa? hoplites (RK9, Cretaceous), Amphisphaera aotea (RP1, Paleocene), A. kina (RP2), Stichomitra granulata (RP3), Buryella foremanae (RP4) and B. tetradica (RP5) Interval Zones. The Late Paleocene Bekoma campechensis Zone of Nishimura (1987) succeeds RP5 at Mead Stream. The K/T boundary does not mark an extinction event for radiolarians, but does coincide with a sudden change from nassellarian to spumellarian dominance. It also coincides with a sudden influx of diatoms in Marlborough, where a fall in sea level appears to have promoted upwelling. Thus, rather than marking a catastrophe, the K/T boundary heralded a period (from RP1 to lower RP3) of great productivity for siliceous plankton. With a return to conditions similar to those of the Cretaceous, later in the Paleocene (upper RP3-RP6), Cretaceous survivors were rapidly replaced by new Tertiary taxa in deep-water settings. However, in shallower settings, many Cretaceous taxa remained abundant throughout the Early Paleocene. Faunal changes at site 208 are similar to those of the deep-water Marlborough sections, but without clear evidence for increased fertilty in the earliest Paleocene.

Radiolaria from Late Eocene to Early Miocene localities in New Zealand are detailed in a series of studies in an attempt to broaden our knowledge of New Zealand Late Paleogene-Early Neogene Radiolaria, and a new technique for investigating Radiolaria is described. Chapter One introduces the studies and the rationale behind each, details the history of radiolarian work in New Zealand, and provides discussion of several points that surfaced during the studies. The points discussed are: radiolarian literature; plate production; scanning electron micrographs versus transmitted light photomicrographs; skeletal terminology; systematic paleontology and the description of new species; radiolarian classification; usefulness of strewn slides. Each study constitutes a published in press, or in review paper and is presented as a chapter. As each chapter is able to stand alone, their abstracts are given below. The reference lists for each paper/chapter have been amalgamated into a master list at the end of the thesis and so do not appear at the end of each chapter: Chapter Two - Seven New Radiolarian Species from the Oligocene of New Zealand Abstract: Seven new radiolarian species from the Oligocene Mahurangi limestone of Northland, New Zealand, are formally described. They are: Dorcadospyris mahurangi (Trissocyclidae), Dictyoprora gibsoni, Siphocampe missilis, Spirocyrtis proboscis (Artostrobiidae), Anthocyrtidium odontatum, Lamprocyclas matakohe (Pterocorythidae), Phormocyrtis vasculum (Theoperidae). Chapter Three – New Radiolaria from the Oligocene and Early Miocene of Northland, New Zealand Abstract: Thirteen new radiolarian species, two new genera and one new combination from the Oligocene and early Miocene of Northland, New Zealand, are formally described - The species are – Heliodiscus tunicatus (Phacodiscidae), Rhopalastrum tritelum (spongodiscidae), Lithomelissa gelasinus, L. maureenae, Lophophaena tekopua (Plagiacanthidae), Valkyria pukapuka (Sethoconidae), Cyrtocapsa osculum, Lophocyrtis (Paralampterium)? inaequalis, Lychnocanium neptunei, Stichocorys negripontensis, Theocorys bianulus, T. perforalvus, T. puriri (Theoperidae); the genera are – Plannapus (Artostrobiidae) and Valkyria (Sethoconidae); the combination is Plannapus microcephalus (Artostrobiidae). Standardised terminology is proposed for internal skeletal elements and external appendages. Emendations are proposed for the family Artostrobiidae and the genera Heliodiscus, Lithomelissa and Cyrtocapsa. Heliodiscus, Cyrtocapsa and Lychnocanium are established as senior synonyms of Astrophacus, Cyrtocapsella and Lychnocanoma respectively. Chapter Four – Early Miocene Radiolaria from Te Kopua Point, Kaipara Harbour, New Zealand Abstract: Radiolaria from the Early Miocene Puriri Formation at Te Kopua Point in the Kaipara area, Northland, New Zealand are documented. Six new species are described - Spongotrochus antoniae (Spongodiscidae), Botryostrobus hollisi, Siphocampe grantmackiei, (Artostrobiidae), Carpocanium rubyae (Carpocaniidae), Anthocyrtidium marieae (Pterocorythidae) and Phormocyrtis alexandrae (Theoperidae). Carpocanium is established as the senior synonym of Carpocanistrum. Chapter Five – Radiolaria from the Oamaru Diatomite, South Island, New Zealand Abstract: Radiolaria from the world-famous Oamaru Diatomite are documented with 24 new species described and three new genera erected The new species are Tricorporisphaera bibula, Zealithapium oamaru (Actionommidae), Plectodiscus runanganus (Porodiscidae), Plannapus hornibrooki, P. mauricei, Spirocyrtis greeni (Artostrobiidae), Botryocella pauciperforata (Cannobotryidae), Carpocanopsis ballisticum (Carpocaniidae), Verutotholus doigi, V. edwardsi, V. mackayi (Neosciadiocapsidae), Lithomelissa lautouri, Velicucullus fragilis (Plagoniidae), Lamprocyclas particollis (Pterocorythidae), Artophormis fluminafauces, Eucyrtidium ventriosum, Eurystomoskevos cauleti, Lophocyrtis (L.) haywardi, Lychnocanium alma, L. waiareka, L. waitaki, Pterosyringium hamata, Sethochytris cavipodis and Thyrsocyrtis (T.?) pingusicoides (Theoperidae). The new genera are Tricorporisphaera, Zealithapium (Actinommidae), and Verutotholus (Neosciadiocapsidae). Emendations are proposed to the family Neosciadiocapsidae and the genus Eurystomoskevos, and Pterosyringium is raised from subgeneric to generic level. Radiolarian faunal composition confirms a Late Eocene age for the Oamaru Diatomite. Chapter Six – Confocal Laser Scanning Microscopy: A New Technique for Investigating and Illustrating Fossil Radiolaria Abstract: Confocal laser scanning microscopy (CLSM), a technique newly applied to the study of fossil Radiolaria, offers the radiolarist clear views of single optical planes of specimens, unhindered by many of the optical effects of conventional light microscopy, while obviating the need to section or break specimens. Resulting images are of a clarity unsurpassed by conventional light microscopy and, as they are saved on computer, are easily viewed, manipulated, enhanced, measured and converted to hard copy. Used in conjunction with common radiolarian study methods CLSM is a powerful tool for gaining additional information with relatively little extra effort. Chapter Seven conveniently summarises taxonomic, stratigraphic and geographic data of all new taxa described, incorporating information gained from the studies and relevant literature. Appendices present the following: data pertaining to all illustrated specimens in this thesis from the University of Auckland Catalogue of Type and Figured Specimens; distribution of Radiolaria at Te Kopua Point; distribution of species and a species list for the Mahurangi Limestone. / Chapter 1 is included in 01front, along with pages 38,93, 130 for additional information. Chapter 2 + of the thesis is now published and subject to copyright restrictions.

This work is a detailed analysis of the transient behaviour of geothermal convective systems. The flow in these systems is found to be fluctuating or regular oscillatory in a simplified two-dimensional model and these unsteady effects persist when the model is refined to include the concepts of temperature dependent viscosity and fluid withdrawal and recharge. The analysis is extended into three dimensions to verify this behaviour. The supplementary exploration of added salinity gradients indicates transient effects of a different kind in this case. The examination of the porous insulator problem confirms the results of previous authors and verifies the viability of the numerical methods that are used throughout the investigation.

The lithologic and biostratigraphic successions of Ururoan, Temaikan and Lower - Middle Heterian (?Sinemurian, Pliensbachian - ?Kimmeridgian) strata from southwest Auckland, south Otago and Southland, New Zealand, are described and discussed. A more logical correlation of the lithologic sequence at Port Waikato with that at Te Akau is proposed. Two new formations are introduced for the sequences on the western limb of the Kawhia Regional Syncline, the Whakapatiki Mudstone for the fine grained lower Kirikiri Group strata in the Awakino Valley and the Gribbon Formation for the Rengarenga Group strata between Marokopa and Mahoenui. In Southland a new formation (Ben Bolt Formation) is proposed for the c.1340m sequence overlying the Flag Hill Sandstone, in turn overlain by a 485m thick, mudstone-dominated formation for which a long disused name is resurrected (Lora Formation). The Lora Formation is in turn overlain by a coarse-grained unit, for which the name West Peak Formation is proposed. In the absence of suitable alternatives, a subdivision of the Ururoan Stage into a Lower Ururoan, the range-zone of pseudaucella marshalli, and an Upper Ururoan, the interval-zone between the last appearance of Pseudaucella marshalli and the first appearance of a Temaikan fauna is proposed. The existing three-fold subdivision of the Temaikan Stage is emended. Belemnopsis mackayi and B. deborahae are retained as the indices of the Temaikan and its lowest subdivision, as they are present in most sections at a consistent stratigraphic position. Retroceramus (Fractoceramus) inconditus is proposed as the basal Middle Temaikan index species. Retroceramus(R.) brownei, which first appears consistently higher than R. inconditus, but below R. marwicki is proposed as the index for the upper Middle Temaikan. Retroceramus (R.) marwicki is proposed as a replacement upper Temaikan index for "Macrocephalites cf. beta-gamma" which is unsuitable. Meleagrinella n. sp. is inconsistent in its first appearance and therefore unsuitable as a Middle Temaikan index and, although confined to this stage, it ranges from Early to early Upper Temaikan. Basal Temaikan Belemnopsis spp. are absent from sections in the Catlins district whereas the earliest Temaikan taxon appearing above typical Ururoan faunas is Meleagrinella n. sp. In the absence of a better alternative Meleagrinella n. sp. is used to mark the base of the stage in the Catlins sections. However, the base of the Temaikan is here likely to be slightly younger than in other sections. Within the redefined Upper Temaikan four subdivisions based on the sequence of Retroceramus species are recognised. The lowest of these is characterised by the first appearance of R. (R.) marwicki, the second by the first appearance of R. (R.) n. sp. A., the third characterised by the first appearance of R. (R.) stehni, and the highest marked by the first appearance of either R. (R ) sp. C. (a wide triangular form) or sp. D. (an ovate flat form). The presence of these two morphologic forms indicate finer zonation of the Upper Temaikan may be possible, with further field work. The Ururoan to Middle Heterian succession of New Zealand is correlated with the international chronostratigraphic scheme based mainly on comparison of New Zealand's Retroceramus succession with that of South America and Indonesia and on relatively rare ammonites. The Ururoan is equivalent to the ?Sinemurian to Late Toarcian, Temaikan to the ?latest Toarcian to Early Callovian and the Early Heterian to the Middle Callovian to latest Middle to Late Oxfordian. Early Ururoan is correlated with the ?Sinemurian to Pliensbachian based on the presence of the ammonite Juraphyllites. Presence of the Early Toarican ammonites Harpoceras cf. falcifer and Dactylioceras spp. in the Late Ururoan indicates a potential international correlation of ?Late Pliensbachian to Late Toarcian. A ?late Toarcian to Aalenian correlation for the Early Temaikan is suggested by the presence of the European belemnite Brevibelus zieteni. Retroceramus (Fractoceramus) inconditus is similar to the Northern hemisphere Mytiloceramus lucifer and the northern hemisphere Retroceramus gr. popovi and thus suggests a latest Aalenian to Early Bajocian correlation of the Middle Temaikan. The earliest Late Middle Temaikan Retroceramus (Retroceramus) marwicki is also present in the Late Bajocian (Rotundum Zone) of Argentina. ?Teloceras gr. banksi, ?stephanoceras (S.) gr. humphriesianum, Chondroceras (C.) gr. evolvescens, C. (C.) cf. recticostatum, and C. (Defonticeras) cf. oblatum are present in the Middle Temaikan reinforcing an earliest to late Early Bajocian correlation for this substage. Toxamblyites aff. densicostatus Sturani, Chondroceras (C.) gr. Evolvescens (Waagen), C. (Schmidtoceras) orbignyanum (Wright), C. (Defonticeras?) sp. indet. occur with Retroceramus marwicki indicating an Early to Late Bajocian correlation for this zone, slightly broader than in Argentina. However, somewhat anomalously the first of these ammonites suggests a Mid Aalenian to Early Bajocian correlation. The succeeding zone (Retroceramus (R.) n. sp A. zone) has yielded the Latest Bathonian Xenocephalites grantmackiei and Lilloettia aff. boesei. Retroceramus(R.)stehni is the index for the third Upper Temaikan Retroceramus zone and is also known from the latest Bathonian to Early Callovian of Argentina. In New Zealand R. stehni is associated with Lilloettia cf. Lilloetensis and Xenocephalites cf. stipanicici which also indicate a latest Bathonian to Early Callovian correlation. The fourth and highest zone of the Upper Temaikan has yielded the ammonites Araucanites marwicki, Eurycephalites gr. extremus, Iniskinites gr. cepoides and Choffatia (Homoeoplanulites) sp. suggesting an Early to Middle Callovian correlation. The overseas relationships of the associated Retroceramus (R.) spp. C. and D. are unknown. The Heterian index Retroceramus (Retroceramus) galoi is of Oxfordian age in Indonesia where it is associated with Malayomaorica malayomaorica. In New Zealand Araucanites marwicki and Sulaites heteriense are present in the Early Heterian, below the incoming of Malayomaorica malayomaorica, low in the range of Retroceramus galoi. The presence of Sulaites high in the Early Heterian suggests a ?Middle to Late Oxfordian correlation while Araucanites indicates the lowest part of the range of Retroceramus galoi could be slightly older, perhaps Upper Callovian. The biostratigraphic scheme presented here is a significant advance on those proposed previously.

This study is based on 15 measured Jurassic to Lower Cretaceous sections and their abundant bivalve faunas distributed mainly in the Nyalam and Gamba districts of southern Xizang. It addresses the establishment of bivalve assemblages, stratigraphic subdivision and correlation, analysis of sedimentary environments, sea-level change and paleogeography in light of the tectonic framework and geological evolution of the Xizang Plateau. The Plateau consists of three terranes: Qangtang, Gangdise and Himalaya They are separated by the sutures: Kunlun-Hoh Xil-Jingsha Jiang, Banggong Co-Nu Jiang, and Yarlu Zangbo Jiang, which represent three closed oceans: Paleo-Tethys, Neo-Tethys and South Xizang Sea. Stratigraphic development of the Jurassic and Lower Cretaceous of southern Xizang is especially closely related to the evolution of the South Xizang Sea Bivalves are one of the most common and important Jurassic and Early Cretaceous fossil groups in the Plateau. From 15 measured sections, 51 bivalve species within 26 genera are described, including 3 new genera and 14 new species. New genera: Vanustus, Yoldioides, Antipectenoides New species: Nuculoma oriens (Nuculidae) Yoldioides jurianoides (Malletiidae) Mesosaccella gangbaensis (Nuculanidae) M. Orienta Grammatodon (Indogrammatodon) sinensis (Parallelodontidae) Oxytoma jiabulensis (Oxytomidae) Meleagrinella minima M. dongshangensis M. sinensis Entolium dongshangensis (Entoliidae) Antipectenoides sinensis Ctenoides shizangensis (Limidae) Anisocardia shizangensis (Arcticidae) Protodiceras lanonglaensis (Megalodontidae) A stratigraphic sequence of ten different bivalve assemblages and four Buchia faunas from the Jurassic to Lower Cretaceous of Nyalam district, and four Jurassic bivalve faunas from the Gamba district are recognised. In addition, the Oxytoma jiabulensis bed and two Meleagrinella beds are also recognised. These assemblages can be seen to be of two types, high and low diversity, indicating different sedimentary environments. These assemblages along with co-existing ammonites also provide a good basis for stratigraphic division and correlation of the sequences. Special attention is given to nomenclatural and other problems associated with the important genus Buchia:. Australobuchia Zakharov is believed to be inseparable generically, and some Xizang species of Buchia an placed in synonymy. On this basis the evolution and migration of the genus is discussed From measured sections in southern Xizang, a comparatively complete Jurassic- Lower Cretaceous sequence has been established, which includes six formations: (in ascending order) Pupugar. Nieniexiongla. Lanongla. Menbu. Xuomo and Gucocun Formations. A new stratigraphic unit, the Gangdong Formation, is established, for Mid-Upper Jurassic strata of the Gamba district. Direct and indirect biostratigraphic correlation within China and between southern Xizang and other places around Gondwanaland is well established. Lithologic features, sedimentary structures and bivalve assemblages allow four environments including nine lithofacies to be recognised in southern Xizang: 1. Inner shelf environment 1] Shoreface sandstone facies 2] Neritic terrigenous clastic facies 3] Open shelf carbonate facies 4] Protected barrier carbonate facies 5] Reef limestone facie 2. Outer shelf environment 6] Siltstone-shale-carbonate facies 3. Slope environment 7] Fine clastic facies 8] Pelagic limestone facies 4. Bathyal environment 9] Dark Buchia-ammonite-lutite facies They can be seen to be organised into sedimentary cycles, which clearly show a huge transgression with three peaks in the Upper Jurassic reaching a maximum at the top of the Jurassic (Upper Tithonian). In the Lower and Middle Jurassic, sea-level changes fluctuated between coastal and shelf-sea environments, whereas in the Upper Jurassic, as a result of sea-floor spreading in the South Xizang Sea and the formation of fault basins, the area descended into bathyal depths. Paleogeographically, the northern part of the Plateau (i.e. the Northern Branch, or Neo-Tethys) underwent a shallowing process along with areal extension during Jurassic times, but shrank in the Early Cretaceous, whereas in the Southern Branch, during Jurassic-Early Cretaceous times, the South Xizang Sea developed a wide variety of sedimentary environments, including inner and outer shelf sea, continental slope and bathyal fault basin.

This thesis describes the vegetation and climatic changes over the past 20,000 years from pollen records at eight northern New Zealand lowland peat and lake sites, ranging from Taranaki to the Far North. The sites investigated are Umutekai Swamp (Taranaki), Lakes Rotomanuka, Rotokauri, and Okoroire (Waikato), Kopouatai Bog (Hauraki Plains), Lake Waiatarua (Auckland), Otakairangi Swamp (mid-Northland), and Trig Road Swamp (Far North). At sites from Auckland southwards, dating and correlation of the pollen records were enhanced by the occurrence of multiple tephra layers within the pollen-bearing sediments. The clearest picture of regional vegetation history and tightest chronologic control were obtained from the tephra-rich organic lake sediments of the Waikato lowlands. Holocene vegetation changes were broadly consistent throughout this northern New Zealand region and indicate climates, which were initially moist, mild and equable, but became increasingly variable and probably drier overall during the late Holocene. Podocarpangiosperm forest was always prominent and Agathis australis forest expanded throughout the region north of latitude 38° S during the last 6,000 years. Kauri was especially prominent in the Waikato region during the 1000 years or so following the Taupo eruption of c.1800 years ago. At pollen sites from Waikato, Hauraki Plains, and Auckland, palynological evidence suggests that people began clearing forests as early as 800 years ago, but probably not much earlier. Pollen records for the last glacial show less regional uniformity. South of Auckland, scattered tracts of Nothofagus or Libocedrus forest within a shrubland/grassland mosaic were succeeded, between c.14.5 and 10 ka by the regional expansion of podocarp-angiosperm forest, with Prumnopitys taxifolia initially prominent. North of Auckland, the pre-Holocene vegetation history is complicated by uncertain chronologies. Conifer-angiosperm forest with prominent A. austalis grew in the Far North during the last glacial, while in mid-Northland, a substantial period of Nothofagus forest, shrub and grassland communities may correspond to either the entire last glacial or to the late glacial. Local variations in vegetation cover were maintained to some extent independently of regional climate, influenced by site specific factors including edaphic controls, hydroseral succession, and local hydrological changes caused by, e.g., lahar or lava flow, fluvial activity and sea level change. The influence of these local factors is most evident for the late glacial, during which period podocarp-angiosperm forest spread throughout northern New Zealand generally, but with considerable variation in timing even between nearby sites. Fire appears to have been an important factor in vegetation change throughout the period investigated, not just during the human deforestation era; peat swamp communities show a long history of association with fire, while in dryland vegetation, Agathis australis appears to have been especially affected by burning. No unequivocal evidence was found for postglacial latitudinal migrations, but several plants show significant altitudinal range expansions during the last glacial compared with their present distributions in northern New Zealand, viz., Nothofagus menziesii, Libocedrus bidwillii, Phyllocladus aspleniifolius, and Halocarpus spp. Thus although vegetation communities at each locality have changed substantially over time, the flora of northern New Zealand remained essentially the same during the c.20,000 years before the human era. Interpretation of the pollen records was assisted by principal components analysis (PCA) and by referring to modern pollen data and pollen-vegetation comparisons obtained from Waipoua Forest, Northland. PCA provides an efficient means of summarising and portraying large pollen datasets, and helps to clarify underlying environmental factors and temporal trends. PCA also generally supports pollen diagram zonations determined by eye. The Waipoua study indicated that the relationship between pollen and tree abundances is highly variable within forests, dependent largely on local site characteristics, especially the masking effect of strong local pollen sources. Nevertheless, quantified pollen-vegetation relationships averaged for the study area mostly accord with results from previous New Zealand modern pollen rain studies, while adding new information for the pollen representation of several prominent northern species. The Waipoua study indicates that pollen spectra rich in Agathis may be found where trees grow nearby, but Agathis pollen appears to be less widely dispersed than pollen of other New Zealand anemophilous taxa. At several swamp sites, correlation of tephra layers and pollen-stratigraphic events reveals problems with radiocarbon chronologies which can not be satisfactorily resolved except by assuming contamination by modern carbon. Sites with a history of hydroseral succession, where swamp communities have developed in former lake basins, are especially prone to this contamination, presumably because root penetration of older sediments provides channels for downward movement of younger carbon. In such situations it may be unwise to date and correlate pre-Holocene sediments on the basis of radiocarbon alone. Periods of hiatus are not uncommon in lake and swamp profiles from northern New Zealand and it is possible that the record of the last glacial is missing or strongly compressed at many Northland sites. Sedimentation rates also varied markedly between and within sequences, precluding the accurate estimation of pollen accumulation rates except at the Waikato lake sites where tephra sequences provide detailed chronological resolution. Even here, however, pollen concentration and accumulation rates appear to have been highly susceptible to short-term fluctuations in the sedimentation regime.

Whole document restricted, see Access Instructions file below for details of how to access the print copy. / This thesis describes the facies, architecture and development of the Tunanui Formation, a deep-marine, sand-rich, slope basin-fill of Middle Miocene age (NZ stages Clifdenian to Lillburnian). The study area is located in the northern Hawke Bay region of the East Coast Basin, North Island, New Zealand, and is within the forearc domain of the Hikurangi active margin. It is part of a structurally complex and now largely emergent accretionary wedge with sediments dating from basal Miocene to present. Due to renewed plate subduction and compressive movements along the margin in the Neogene, highly restricted intra-slope basins developed between rising thrust ridges of the inner-forearc. The Tunanui deepwater-clastics were originally deposited as flat-lying sediments within one such elongate slope-basin, atop the deformed sedimentary prism. These rocks are now present within the subsurface of offshore Hawke Bay and extend N/NW to the onshore areas. Structural inversion has produced outcrops of Tunanui sediments in the core of two major anticlines, the Mangaone and the Morere Highs. In the Morere Anticline along the Paritu Coast south of Gisborne, spectacular sea-cliff exposures provide a unique opportunity to investigate the nature and development of over 1000 m thickness of sandy, deepwater, slope basin-fill representing almost the entire stratigraphic section of the Tunanui Formation. Rocks in this remote region have not been previously described in any detail. A database of thousands of digital field photographs, together with 71 stratigraphic logs and some deep borehole information has enabled the production of a series of detailed correlations for the Tunanui sections. In turn, the number of logs available has made possible the construction of a large-scale (over c.25 km in length) stratigraphic cross-section, slightly oblique to the basin axis, through the deepwater clastic succession. Interpretation has allowed a series of deductions to be made concerning the nature of the 'Tunanui Basin' fill and its development, the types of gravity flow elements present and in most field areas, the production of a detailed sandstone architecture for the Tunanui deposits. Five phases of basin fill are recognised. These range from highly restricted, over-thickened sandstone packages, deposited under conditions of high slope gradient and complex basin-floor topography, within the lower parts of the sequence, to laterally continuous 'fan-like' deposits, and thinner-bedded sandstones within the upper part of the Tunanui section. A c.250 m thick sequence that is slightly younger than the upper Tunanui Formation, containing numerous channel-forms (the Tangawa Formation), is present on the East Coast of the Mahia Peninsula c.17 km to the south of the Paritu Coast outcrops. The architecture of the Tangawa Formation, and its regional structural position, indicates that it was the 'spill' of the Tunanui basin-fill into an adjacent down-slope sediment trap within the forearc terrane. This depocentre was also controlled by deep-seated imbricate thrust faulting in common with the Tunanui Basin. Several different types of deepwater channel-forms are present within what is a limited stratigraphic range. The vertical sequence reflects an overall progression within a muddy slope from deeply incised, erosive systems, to laterally offset-stacked channels of a mixed erosional depositional type.