1 10 30 https://theses.otagogeology.org.nz/files/original/d4d06c5c9345c095b6cb9ba405b1fb1c.pdf 0da3fa631abc646eb41ac3d74bd75217 Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Geology theses OU Geology thesis Thesis or dissertation completed by University of Otago Geology students Location WKT (WGS84) The location stored in WKT (WGS84) format MULTIPOLYGON (((-110.326873029723 35.1091344486426,-110.318230781959 35.1214432048754,-110.301394402982 35.112238115349,-110.290255505864 35.0951927799335,-110.303058835885 35.0945087871119,-110.326873029723 35.1091344486426))) Author last name Last name of the Author Re Project type Is it an MSc, PhD, BSc(Hons) or PGDipSci? PhD Advisers Who supervised/advised this student White, J.D.L. Ort, M. Abstract The Abstract for this thesis Many populated areas in the world (e.g., Flagstaff, AZ; Auckland, NZ; Mexico City, MEX) lie within active monogenetic volcanic fields that typically contain small volcanic cones and explosive maar craters formed over the course of a single eruptive cycle. Although much work has focused on the eruptive behaviour of monogenetic volcanoes, little geological information exists about their subsurface development and how the movement of magma through Earth’s shallow crust modulates the location and style of hazardous volcanic eruptions. Determination of the dynamics of magma intrusion and the transition from a coherent magma's ascent to its explosive fragmentation is crucial to our understanding of the controls on explosive versus effusive eruptive behaviour, thus to better evaluation of risks in a certain area. This study aims to determine the processes and relative timing of activity that took place below the ground surface of the deeply-eroded but well-preserved Jagged Rocks Complex, a cluster of monogenetic volcanoes within the Miocene Hopi Buttes Volcanic Field in northeastern Arizona, by combining detailed structural mapping, volcanological observation, paleomagnetic and geochemical analysis. The Jagged Rocks Complex, exposed at ~ 350 m below the pre-eruptive surface, comprises a well-preserved intrusive network, including dikes, sills and inclined sheets, associated with different type of fragmental bodies including buds, pyroclastic massifs and a diatreme, that represent different extents of shallow-depth fragmentation. These exposures at the Jagged Rocks Complex provide an excellent natural laboratory for examining the subsurface record of volcano initiation, and for constraining interpretations of processes controlling upward migration of magma from intrusion to eruption. This multidisciplinary approach allows an investigation at different levels from the source region to the surface, and aims to shed the light on the processes that regulate eruptions not only within monogenetic volcanic fields but also within small basaltic volcanoes in general. OURArchive handle The handle from the Otago University Research Archive (OURArchive) <a href="http://hdl.handle.net/10523/7358">http://hdl.handle.net/10523/7358</a> OURArchvive access level Open Access Department The department where the student is studying primarily. Geology Named locality Named locality describing the field area location. Arizona USA Thesis description Number of pages, maps, CDs, etc. 273 pages A4 Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Identifier An unambiguous reference to the resource within a given context 2017Re Creator An entity primarily responsible for making the resource Re, Giuseppe (Peppe) Date A point or period of time associated with an event in the lifecycle of the resource 2017 Title A name given to the resource Evolution and dynamics of a monogenetic volcanic complex in the southern Hopi Buttes Volcanic Field (AZ, US): magma diversion and fragmentation processes at the Jagged Rocks Complex Subject The topic of the resource Volcanology Basaltic Conduit diatreme Dike Feeder Hopi Buttes Monogenetic volcano https://theses.otagogeology.org.nz/files/original/48572e4d61711ae8b65345e14aad2f84.pdf 7161d97d9bf6331b7bf4380fe1e78fe6 Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Geology theses OU Geology thesis Thesis or dissertation completed by University of Otago Geology students Location WKT (WGS84) The location stored in WKT (WGS84) format MULTIPOLYGON (((-18.4711923145008 63.5416956421709,-18.9703197424945 63.50349596139,-19.1271883627211 63.813963623143,-18.6280609347274 63.8517463583428,-18.4711923145008 63.5416956421709))) Author last name Last name of the Author Gorny Project type Is it an MSc, PhD, BSc(Hons) or PGDipSci? PhD Advisers Who supervised/advised this student White, J.D.L. Gudmundsson, M.T. Abstract The Abstract for this thesis Large scale subglacial eruptions are enigmatic. Their eruption and emplacement dynamics are not well understood due to the incompleteness of preserved units. The Snæbýlisheiði unit, south Iceland, forms a ca. 27 cubic km elongate, flat-topped ridge of volcaniclastic debris coupled with and intruded by coherent basalt and represents a large-scale subglacial basaltic fissure eruption, where both the eruption and ridge growth occurred subglacially. It is preserved in its entirety from the eruption site stretching over 34 km towards the modern day coastline. Snæbýlisheiði differs from typical Icelandic subglacial deposits in being elongate perpendicular to the controlling rift direction reflecting the high eruption rates and the overlying glacier slope at the time of eruption. Investigation of the source area reveals voluminous volcaniclastic debris encased by and complexly intruded into by coherent basalt; I infer early and continuing production of pyroclastic deposits with near-synchronous emplacement of peperitic intrusions. Volcaniclastic debris accumulated at the eruption site and prograded towards the present coastline by deposition in an enlarging drainage network. Deposition took place both in migrating and converging tunnels and during short intervals of sheet flow during outbreak floods. The main body of the deposit is characterized by complexly bedded volcaniclastic debris coupled with and intruded by a longitudinally extensive basalt sheet. The deposits result from an intricate depositional and intrusive history, with a longitudinally extensive internal basalt sheet comprising complex and irregular coherent bodies with dikes, apophyses, horns, tendrils, and lobate fingers that extend into the surrounding host debris. Peperitic margins, where dynamic mingling or quench fragmentation occurred, are common. The basalt sheet fed higher-level intrusions through irregular apophyses as it propagated down-flow to produce the multilevel intrusions exposed today. During propagation the coherent basalt sheet concentrated into gently meandering and locally bifurcating conduits having sheet-lobe extensions. This channelized or conduit-concentrated magma propagation was very thermally and mechanically efficient, insulating the molten basalt and hence reducing rheological changes from cooling. This efficiency is reflected by the intrusions’ propagation more than 34 km from the source area or eruption site with little change to overall intrusion morphology. The sheet forms apophyses and tendrils into the overlying sediment where it dynamically mingled to form extensive peperitic textures. In places, apophyses locally intersected the sediment-water interface and shed clasts into flowing water. These “contorticlasts” have “rolled-up” forms encasing matrix-forming debris. The main body of the intrusion propagated through the host in a channelized fashion, gently meandering within the edifice, with thin sheet-like extensions along the margins. Tendrils and apophyses extending from the main body extended into the overlying host, where they experienced enhanced cooling and frictional interactions resulting in efficient brittle fragmentation. The resulting fragments are typically angular, dense, and glassy medium lapilli to coarse ash sized and make up the bulk of the distal deposits. Where apophyses remain attached to the basal intrusion the margins fragment in the ductile regime forming fluidal-type fragments. Bed contacts are sharp to diffuse, locally erosive, indicating deposition from traction or/and high-concentration flows. Shedding of contorticlasts into bedload beneath flowing water requires that their source intrusions shoaled, hence implying the voluminous intrusions would have also been transferring heat into the water with only a thin, deforming clastic blanket to reduce the heat flux into water and hence overlying ice. As the eruption is influenced by the ice, the ice is influenced by the eruption. The vast amounts of heat release during fragmentation will melt ice above the fragmentation zone. Using simplified ice mechanics and thermodynamic principles the total volume of ice melted can be calculated for a subglacial volcano of any type. For the Snæbýlisheiði unit, the thermal model was constructed to consider the consequences of the formation of the unit based on field and other observational data. The thermal model for the extent of ice melted by the emplacement of the Snæbýlisheiði unit combined with field observations and dissolved volatile contents in matrix glass suggests that the eruption likely occurred during the PreBoreal or Younger Dryas stadials. This is the first description of a complete unit formed by a large-scale subglacial basaltic fissure eruption. OURArchive handle The handle from the Otago University Research Archive (OURArchive) <a href="http://hdl.handle.net/10523/7031">http://hdl.handle.net/10523/7031</a> OURArchvive access level Abstract Only Department The department where the student is studying primarily. Geology Named locality Named locality describing the field area location. South Iceland Thesis description Number of pages, maps, CDs, etc. 791 pages A4, 2 A1 maps in back pocket folded Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Identifier An unambiguous reference to the resource within a given context 2017Gorny Creator An entity primarily responsible for making the resource Gorny, Carolyn Fine (Carolyn) Date A point or period of time associated with an event in the lifecycle of the resource 2017 Title A name given to the resource The Origin of Lava-Hyaloclastite Sheets, South Iceland Subject The topic of the resource Volcanology Dalsheidi Eruption dynamics Fissure eruption Glaciofluvial Glaciovolcanism Glass microtextures Ice melting Iceland Intrusions Juvenile clast microtextures lava-hyaloclastite sheets Lithofacies analysis Magma fragmentation Magma-water interactions Particle analysis Peperite Pipe-flow Sida Group Slurry Subglacial eruption Subglacial sediment transport/deposition Surtseyan eruption Thermal model Tholeiitic basalt Vesicle number density volatiles Volcano-ice interactions https://theses.otagogeology.org.nz/files/original/946cde9a12925510199a73ff2b5452b0.pdf 12c1c9a66180bdb6ea240ecc7c186dff Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Geology theses OU Geology thesis Thesis or dissertation completed by University of Otago Geology students Location WKT (WGS84) The location stored in WKT (WGS84) format MULTIPOLYGON (((168.885947903117 -44.3868052733412,169.230103070856 -44.3965575535404,169.216644972497 -44.6526019245831,168.870984267114 -44.6427529069578,168.885947903117 -44.3868052733412))) Author last name Last name of the Author Maloney Project type Is it an MSc, PhD, BSc(Hons) or PGDipSci? MSc Advisers Who supervised/advised this student White, J.D.L. Abstract The Abstract for this thesis The Lake Wanaka diatreme represents an eroded Oligocene maar-diatreme volcano situated within the Alpine Dike Swarm, northwest Otago, New Zealand. Current levels of exposure display lithofacies that are characteristic of lower diatreme and root zone deposits. There are four main lithofacies exposed within the Lake Wanaka diatreme; (1) country-rock breccia, (2) lapilli tuff and tuff breccia, (3) schist megablocks, and (4) coherent lamprophyre. The country-rock breccia is monomict and composed of randomly orientated schist clasts millimetre to a metre in size with no juvenile material present. Lapilli tuff and tuff breccias are unbedded, poorly mixed, and clast-supported by juvenile pyroclasts. They contain common composite loaded pyroclasts with dispersed schist lithics within. The schist megablocks are large blocks of schist country-rock up to 4 m in size that protrude from cliffs of the coherent lamprophyre. The coherent lamprophyre is the most prominent rock within the diatreme, is typically columnar jointed, and contains xenoliths of schist and peridotite, plus amphibole megacrysts. The country-rock breccia represents the deposit of rock fall into an open cavity, sourced from weakened and unstable wall rock. The open cavity was created by explosions, probably thermohydraulic, within the root zone that drove volcanic material upwards, leaving behind a temporarily evacuated volume. Further volcanic activity produced shaking that led to the clasts of the country-rock breccia becoming tightly packed in places and caused brittle fragmentation at clast contacts. The large schist megablocks were slabbed off the vent wall, and accumulated on a ledge before becoming enveloped by the lamprophyre. Lapilli tuff and tuff breccia were primarily deposited as spatter. Local agglutination textures can be seen at the point contacts of some juvenile pyroclasts, implying they were above the minimum glass transition temperature. Fragmentation of the magma was driven by bubble bursts or more intensive lava fountaining inferred to have been driven by vapour explosions generated by magma-water interactions at depth. Abundant composite loaded juvenile pyroclasts formed when wall rock lithics were shed into the magma prior to, and during fragmentation. Void space that remained between clasts in the lapilli tuff deposit was later cemented by ankerite. Isotopic signatures of the ankerite suggest it was sourced from mixing between meteoric waters and atmospheric CO2. The columnar jointed coherent lamprophyre is interpreted to have been a late stage intrusive sill that entrained schist xenoliths of various sizes as it intruded the diatreme. Paleomagnetic determination of emplacement temperatures suggests that the lapilli tuff was deposited hot, above 580 °C and the same deposit was later reheated to 295–349 °C. A schist xenolith in the coherent lamprophyre was heated to a minimum of 630 °C. These results indicate high temperatures in the diatreme soon after lapilli tuff deposition, and later heating when a nearby lamprophyre sill was intruded. OURArchive handle The handle from the Otago University Research Archive (OURArchive) <a href="http://hdl.handle.net/10523/6895">http://hdl.handle.net/10523/6895</a> OURArchvive access level Open Access Department The department where the student is studying primarily. Geology Named locality Named locality describing the field area location. Wanaka Central Otago Thesis description Number of pages, maps, CDs, etc. xi, 128 pages A4 Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Identifier An unambiguous reference to the resource within a given context 2016Maloney Creator An entity primarily responsible for making the resource Maloney, Samuel Peter (Sam) Date A point or period of time associated with an event in the lifecycle of the resource 2016 Title A name given to the resource Volcanology of the Lake Wanaka diatreme in the Alpine Dike Swarm, New Zealand Subject The topic of the resource Volcanology Alpine dike swarm diatreme Lake Wanaka lamprophyre https://theses.otagogeology.org.nz/files/original/3d13452d494655e3caadb103a360ec90.pdf da7ad0c5424389d64eec856cbfd3d667 Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Geology theses OU Geology thesis Thesis or dissertation completed by University of Otago Geology students Location WKT (WGS84) The location stored in WKT (WGS84) format POLYGON ((170.940006954538575 -45.086981031540319,171.00179816729198 -45.089032006114557,171.000225480588284 -45.153310855850748,170.940970196037284 -45.153686530991479,170.940006954538575 -45.086981031540319)) Author last name Last name of the Author Moorhouse Project type Is it an MSc, PhD, BSc(Hons) or PGDipSci? PhD Advisers Who supervised/advised this student White, J.D.L. Abstract The Abstract for this thesis Since the eruption of Surtsey (1963 - 1965) many studies have been made of the resulting island, but the pre-emergent base remains submarine, un-incised and little studied. The same is true for many recently studied Surtseyan volcanoes, and means the pre-emergent parts of subaqueous eruptions are not well documented. This thesis presents an in depth study of the superb deposits of Surtseyan-style eruptions preserved in the South Island of New Zealand in Otago sea-cliffs along the coastline between Oamaru and Moeraki. These Eocene-Oligocene intraplate basaltic field deposits erupted in Surtseyan-style onto a submerged continental shelf and have since been exposed above sea level. They are inferred to be typical products of submarine processes such as those that built Surtsey to the sea surface. Volcanic fields typically include many small, monogenetic, volcanoes formed by single eruptions fed by short-lived magma plumbing systems that solidify after eruption. However, the stratigraphy of Cape Wanbrow suggests that eruptions produced multiple volcanoes whose edifices overlapped within a small area, but separated by millions of years. The small Cape Wanbrow highland is shown to include the remnants of 6 volcanoes that are distinguished by discordant to locally concordant inter-volcano contacts marked by biogenic accumulations or other slow-formed features. This discovery challenges the traditional view of monogenetic volcanoes and calls for researchers in monogenetic fields to start evaluating both unstudied and previously studied monogenetic volcanoes with this in mind. The 6 volcanoes contain several lithofacies associations: (a) the dominantly pyroclastic E1 comprising well-bedded tuff and lapilli-tuff, emplaced by traction dominated unsteady, turbulent high-density currents; (b) E2, massive to diffusely laminated block-rich tuff deposited by grain-dominant cohesionless debris flows; (c) E3, broadly cross stratified tuff with local lenses of low to high-angle cross-stratification which was deposited by either subaerial pyroclastic currents or subaqueously by unstable antidune and chute-and-pool forming supercritical flows; (d) E4, very-fine- to medium-grained tuff deposited by turbidity currents; (e) E5, bedded bioclast-rich tuff with increasing glaucony content upward, emplaced by debris flows; (f) E6, pillow lava and inter-pillow bioclastic sediment; and (g) E7, hyaloclastite breccia. These lithofacies associations aid interpretation of the eruptive evolution of each separate volcano, which in turn grew and degraded during build-up of the overall volcanic pile. Sedimentary processes played a prominent role in the evolution of the volcanic pile with both syn- and post-eruptive remobilization of debris from the growing pile of primary pyroclastic deposits of multiple volcanoes separated by time. An increase in bioclastic detritus up-sequence suggests that the stack of deposits from overlapping volcanoes built up into shallow enough waters for colonization to occur. This material was periodically shed from the top of the edifice to form bioclast-rich debris flow deposits of volcanoes 4, 5 and 6. Bedform geometries of volcanogenic sedimentary structures produced in both subaqueous and subaerial environments can be incredibly similar, if not identical, and this has resulted in a long history of difficulties in unambiguously distinguishing primary from reworked deposits, and gas-deposited from water-deposited ones. Sedimentary structures such as dunes and low- and high-angle cross-stratification produced by numerous flow types make interpretation of setting difficult. In particular the architecture of such deposits and often field observations of contextual detail can be extremely difficult to interpret based on their ubiquitous presence in many settings and flow types. This is made increasingly difficult when structures are poorly preserved, exposures are limited and independent palaeoenvironmental indicators are absent or ambiguous. However correct interpretation of such sedimentary structures along with the deposits they are part of can be crucial to understanding the host volcanic sequences. The origins of dunes and associated structures that occur within the pyroclastic deposits at Cape Wanbrow serve as an example, and have long been debated. To determine the depositional setting of dune-bearing deposits, careful analysis of contextual information has been completed along with the examination of well-described examples of; (1) subaerial dry pyroclastic deposits, (2) subaerial moist pyroclastic deposits, (3) deposits of gaseous fluid-gravity flow (e.g. eolian currents), (4) unidirectional fluid-gravity water flow deposits (e.g. rivers, tides) and (5) aqueous sediment-gravity flow deposits split into those comprising pyroclastic material and those with non-pyroclastic material. This includes examination of the physical controls that shape each example and the factors controlling bedform deposition in that environment with the aim of being able to distinguish between major flow types in each environment. For Cape Wanbrow, this analysis showed that ambiguous bedforms were formed subaerially, which thus provides direct evidence for emergence and subaerial growth of one of the the volcanoes represented in the succession. To understand multiple eruptions of monogenetic volcanoes at one site at Cape Wanbrow a study of peridotite xenoliths from Kakanui and Boatmans Harbour revealed that the peridotitic portions of sub-continental lithospheric mantle (SCLM) beneath North Otago contains a degree of compositional variation but is relatively fertile. The origins of the xenoliths indicate that the magmas are from either the base of the spinel facies lithosphere, from within the predicted narrow zone of garnet facies lithosphere or from within the asthenosphere. The xenoliths indicate that the magma source was fairly deep, and therefore the process that led to multiple eruptions over a small geographical area has to be one that affected the asthenosphere or the lower lithosphere. OURArchive handle The handle from the Otago University Research Archive (OURArchive) <a href="http://hdl.handle.net/10523/6012">http://hdl.handle.net/10523/6012</a> OURArchvive access level Open Access Department The department where the student is studying primarily. Geology Named locality Named locality describing the field area location. Northeast Otago Cape Wanbrow Thesis description Number of pages, maps, CDs, etc. xx, 219 pages A4 Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Identifier An unambiguous reference to the resource within a given context 2015Moorhouse Creator An entity primarily responsible for making the resource Moorhouse, Benjamin Luke Date A point or period of time associated with an event in the lifecycle of the resource 2015 Title A name given to the resource The emplacement of overlapping submarine deposits of monogenetic Surtseyan-style volcanoes onto a submerged continental shelf that built-up over millions of years in the Waiareka-Deborah Volcanic Field, New Zealand Subject The topic of the resource Volcanology monogenetic New Zealand Northeast Otago submarine Surtseyan volcanoes Waiareka-Deborah Volcanics https://theses.otagogeology.org.nz/files/original/63afddef819f9f6f9196be5dd882c54d.pdf bec82779471eed258f899a6f8f01b78a Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Geology theses OU Geology thesis Thesis or dissertation completed by University of Otago Geology students Location WKT (WGS84) The location stored in WKT (WGS84) format POLYGON ((170.645410735438048 -45.68886906718609,170.590243071158852 -45.691647629262405,170.578760209540263 -45.674257715981327,170.589245854143513 -45.655546404157548,170.622297477666962 -45.656953928908955,170.649091909342161 -45.637503848559703,170.678307847888732 -45.645246264572044,170.645410735438048 -45.68886906718609)) Author last name Last name of the Author McLeod Project type Is it an MSc, PhD, BSc(Hons) or PGDipSci? BSc(Hons) Advisers Who supervised/advised this student White, J.D.L. Palin, J.M. Abstract The Abstract for this thesis A study of Miocene alkaline volcanic rocks at Karitane, East Otago was undertaken to characterise the distribution and composition of the ‘Karitane Suite’. The suite is located on the northern periphery of Dunedin Volcano and contains basanites, hawaiites, benmoreites, tephri-phonolites and phonolites that were formed by magmatic differentiation of a basanitic parent magma at upper mantle to crustal levels. Major element trends show strong depletions of Fe, Ca, Mg, Ti, and enrichments of Na, K, Al and P that are consistent with fractional crystallisation involving clinopyroxene, kaersutite and Ti-magnetite for the series basanite to benmoreite, and kaersutite and alkali feldspar for the series benmoreite to phonolite. Kaersutite bearing mafic inclusions in tephri-phonolite and benmoreite also record a history of repeated injections of basanitic melt into crustal magma chambers that may have influenced the style and extent of volcanism in the Karitane area. Large, columnar jointed blocks at Karitane Beach and rare in situ outcrops further inland are the only remnants of volcanic rock following post Miocene erosion of the area. Field mapping indicates that much of the present and historical erosion is controlled by slumping and landslides in clay rich marine sedimentary rocks that dominate the local stratigraphy. Such landslides are responsible for erosion of the volcanic cover sequence, and the extent of these landslides was used to locate in situ remnants of the Karitane Suite from the ridges above the coast Department The department where the student is studying primarily. Geology Named locality Named locality describing the field area location. Otago East Otago Karitane Puketeraki Seacliff Pukemaeroero Dunedin Organ Pipes Pyramid Victory Beach Thesis description Number of pages, maps, CDs, etc. 176p with A2 map in back pocket Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Identifier An unambiguous reference to the resource within a given context 2015McLeod Creator An entity primarily responsible for making the resource McLeod, Oliver Emerson, 1993 (Oliver) Date A point or period of time associated with an event in the lifecycle of the resource 2015 Title A name given to the resource Petrology of alkaline volcanic rocks in the Karitane Area, East Otago. Subject The topic of the resource Geochemistry Map Petrology Volcanology basanite Dunedin Volcanic Complex Dunedin Volcanic Group Dunedin Volcano Fractionation Karitane Landslides phonolite Puketeraki Whole rock analysis https://theses.otagogeology.org.nz/files/original/32b14e467b6d10a30212a661b52e1d55.pdf 01f7ab807449b3de71fb5ac23d471292 Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Geology theses OU Geology thesis Thesis or dissertation completed by University of Otago Geology students Author last name Last name of the Author Andrews Project type Is it an MSc, PhD, BSc(Hons) or PGDipSci? PhD Advisers Who supervised/advised this student White, J.D.L. Valentine, G. Abstract The Abstract for this thesis In recent decades, major fieldwork studies have greatly advanced our knowledge of maar-diatreme systems, the second most common type of volcano; despite this, much of the interpretation is strongly debated. My original contribution to volcanological research is twofold: firstly, successfully simulating maar-diatreme systems using analogue experimentation in order to determine the processes that generate them; secondly, using mathematical modelling to produce a predictive model for their total energy release during an eruption. This study uses a tripartite, quantitative approach: (1) bench-scale experiments are used to generate simulated maar-diatreme volcanoes and examine their eruption and depositional processes; (2) these are qualitatively compared and quantitatively scaled to both field-scale experiments and natural maar-diatreme volcanoes; and (3) the 1886 maar-forming Rotomahana eruption is used as a case study for a new thermodynamic model which gives a first-order calculation of the cumulative energy change during the event. This study finds that maar-diatreme volcanoes can form through both ascending and descending blast series; multiple types of diatreme can form depending on the blast pattern. Debris jets responsible for the genesis of such systems are two-tier processes: the crater excavation and upward entrainment processes are temporally segregated. The behaviour of the explosively generated cavities, the preservation potential of the system architecture, and the stratigraphic partitioning of blast energy are controlled by mathematical relationships between blast depth and energy. Comparing the simulated volcanoes’ sedimentological architecture to natural examples reveals additional information regarding their eruption history and depositional processes. Data produced by the thermodynamic modelling of the 1886 Rotomahana event corroborates with both fieldwork studies and direct observations, and reveals the eruption was overwhelmingly dominated by a thermal component; this predictive model is hypothetically applicable to similar volcanic systems. A new conceptual model of maar-diatreme formation is conceived based on a synthesis of the findings of this thesis. OURArchive handle The handle from the Otago University Research Archive (OURArchive) <a href="http://hdl.handle.net/10523/5716">http://hdl.handle.net/10523/5716</a> OURArchvive access level Open Access Department The department where the student is studying primarily. Geology Thesis description Number of pages, maps, CDs, etc. 321 pages A4 Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Identifier An unambiguous reference to the resource within a given context 2015Andrews Creator An entity primarily responsible for making the resource Andrews, Robin George Date A point or period of time associated with an event in the lifecycle of the resource 2015 Title A name given to the resource Approaches in Experimental Volcanology: Bench-Scale, Field-Scale and Mathematical Modelling of Maar-Diatreme Systems Subject The topic of the resource Volcanology bench-scale experiments Experimental Volcanology field-scale experiments maar-diatreme volcanoes mathematical modelling phreatomagmatism https://theses.otagogeology.org.nz/files/original/bf6ff2523b7eab0eb1cef7d4f7f03054.pdf c2e118430a1c4d2024ca857e0daa3f6c Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Geology theses OU Geology thesis Thesis or dissertation completed by University of Otago Geology students Location WKT (WGS84) The location stored in WKT (WGS84) format POLYGON ((171.049635063794909 -45.06576525856206,170.90794555027091 -45.241289254485061,170.804882988596205 -45.225659396297367,170.910174343019349 -45.019235135644244,171.049635063794909 -45.06576525856206)) Author last name Last name of the Author Hicks Project type Is it an MSc, PhD, BSc(Hons) or PGDipSci? PhD Advisers Who supervised/advised this student Fordyce, R.E. White, J.D.L. Lee, D.E. Abstract The Abstract for this thesis In Late Cretaceous times, regional subsidence resulted in deposition of a transgressive marine continental shelf sequence across the east of the South Island, which reportedly reached its peak in the Late Oligocene, followed by a Neogene regression. The Waiareka Volcanic-Ototara Limestone sequences of this study formed in the later phases of the Late Cretaceous-Mid Cenozoic transgression when Zealandia was substantially submerged. Previous studies interpreted the volcanics as formed by short-lived localized marine Surtseyan volcanoes which erupted in a continental shelf setting probably tens of km from land, remote from a source of terrigenous components. This thesis reports on the stratigraphy, sedimentology, and especially the foraminiferal micropaleontology for the basaltic Waiareka Volcanics and the immediately overlying Ototara Limestone at 3 localities in North Otago, New Zealand. These strata have been reported widely in studies on regional geology, stratigraphy, paleontology, volcanology and igneous petrology, but few details have been published on the physical stratigraphy and biostratigraphy of limestone and associated sedimentary rocks above the Waiareka-Deborah volcanics. This study uses physical sedimentology and foraminiferal micropaleontology to deduce details of the Late Eocene marine environment associated with the Waiareka-Deborah volcanics. Composite lithostratigraphic sections of 18-20 m meters were made for the limestone-dominated strata above the Waiareka volcanics at the 3 study localities of Reidston, Maheno and Bridge Point, North Otago. Samples from those sections indicated lower to middle Runangan Stage, Late Eocene (later Priabonian) for all 3 localities, bounded by the first occurrence of Bolivina pontis at the base of Runangan, about 36.4 Ma and the last occurrence of Globigerinatheka index at 34.6 Ma (end of Runangan). The absence of G. brevis suggests that the uppermost Runangan was not represented. Thus, sequences span from the base of the Runangan stage to at least the end of the Subbotina linaperta zone, uncertainly a little older than 34.6 Ma. Paleodepths were equivalent to inner to mid shelf, as deduced from micropaleontological assessments using benthic and planktic foraminifera, taking also physical sedimentology in account. Warm to subtropical paleotemperatures were deduced by the presence of warm stenothermal fossil foraminifera including species in large benthic genera such as Asterocyclina, Asterigerina, Wadella, and Cribrorotalia, as well as by planktic species such as Globigerinatheka index, and Hantkenina alabamensis. OURArchive handle The handle from the Otago University Research Archive (OURArchive) <a href="http://hdl.handle.net/10523/4881">http://hdl.handle.net/10523/4881</a> OURArchvive access level Abstract Only Department The department where the student is studying primarily. Geology Named locality Named locality describing the field area location. Northeast Otago Thesis description Number of pages, maps, CDs, etc. xviii, 417 pages A4, some A3 foldouts Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Identifier An unambiguous reference to the resource within a given context 2014Hicks Creator An entity primarily responsible for making the resource Hicks, Simone Barbara Date A point or period of time associated with an event in the lifecycle of the resource 2014 Title A name given to the resource Paleoecology and sedimentology of the volcanically active Late Eocene continental shelf, Northeast Otago, New Zealand Subject The topic of the resource Paleontology Paleoecology Sedimentology biostratigraphy Eocene Foraminifera micropaleontology Otago paleoecology Runangan sedimentology https://theses.otagogeology.org.nz/files/original/8179ffbd9b5841d5afda16ed6bc34053.pdf 05b4751989514e5697dc86695d50b522 Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Geology theses OU Geology thesis Thesis or dissertation completed by University of Otago Geology students Location WKT (WGS84) The location stored in WKT (WGS84) format POLYGON ((-20.622451335754462 63.307985499708614,-20.594999327214847 63.313277037891055,-20.587155896203495 63.297559921781094,-20.600347121086156 63.293869965035654,-20.616390502700249 63.295955650965247,-20.622451335754462 63.307985499708614)) Author last name Last name of the Author Bush-Marcinowski Project type Is it an MSc, PhD, BSc(Hons) or PGDipSci? BSc(Hons) Advisers Who supervised/advised this student White, J.D.L. Abstract The Abstract for this thesis Holocene explosive surtseyan volcanism on the southern most tip of the Vestmannaeyjar archipelago is reported and discussed. Subaerial tuff and tephra deposits recording a 180m thickness retrieved from a borehole are analysed from one of the two active explosive craters during the formation of the island of Surtsey. A range of minerologies, coarseness, porosities, alteration and densities are encountered throughout the volcanic pile, highlighting the non-­‐uniform nature of deposits due to post volcanic processes. Additionally, the presence of shear planes, concentric subsidence faults, accretionary lappili, tuff vesicles and scoraceous fragments infer mass flow processes operating within the crater. The geochemical variation of glass grains and a few olivine penocrysts are analysed from new subsamples. Primarily a non-­‐variation in major elements exists throughout the borehole, with change only observed within the initial stages of eruptions. An average vesicularity range of 40-­‐50% exists in most samples, consistent with other surtseyan volcanic eruption ranges. These characteristics together infer a closed-­‐system magma chamber complex beneath the Surtsey region with normal fractional crystallization. The magma batch that produced all satellite vents is relatively homogenous with whole rock variation minimal. Department The department where the student is studying primarily. Geology Named locality Named locality describing the field area location. Surtsey Iceland Thesis description Number of pages, maps, CDs, etc. 90 pages A4 Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Identifier An unambiguous reference to the resource within a given context 2014Bush-Marcinowski Creator An entity primarily responsible for making the resource Bush-Marcinowski, Tim Date A point or period of time associated with an event in the lifecycle of the resource 2014 Title A name given to the resource Compositional and textural variation of Surtur I tephra crater through the Surtsey eruption, Iceland, 1963-1967 Subject The topic of the resource Volcanology fractional crystallisation lapilli tephra tuff https://theses.otagogeology.org.nz/files/original/99ab62d8ee34015ad8b1d54afd669882.pdf b4b0a97198b1b23dd34f27acf0db853a Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Geology theses OU Geology thesis Thesis or dissertation completed by University of Otago Geology students Location WKT (WGS84) The location stored in WKT (WGS84) format POLYGON ((-110.538039144707525 35.604813712081047,-110.324127389853018 35.663024395560669,-110.070998479941906 35.668843111302046,-109.839260745516228 35.494095647681959,-109.871347508744364 35.31896388243829,-110.174389161454911 35.084858422440377,-110.359779348995446 35.102439939710258,-110.57725629976413 35.359862293443044,-110.538039144707525 35.604813712081047)) Author last name Last name of the Author Lefebvre Project type Is it an MSc, PhD, BSc(Hons) or PGDipSci? PhD Advisers Who supervised/advised this student White, J.D.L. Kjarsgaard, B. Abstract The Abstract for this thesis Maar-diatreme volcanoes are unique in that most "eruptive" activity takes place below the ground surface, thus forming large conduit structures filled with pyroclastic deposits that are large relative to their volcanic edifices. These small-volume volcanoes are traditionally divided into three main levels based on common divergences in geometry and internal architecture at different depths: feeder dike, diatreme structure (conduit structure) and tephra ring (surface deposits). Although maar-diatreme volcanoes worldwide show generally very similar characteristics despite many different magma compositions, there is no consensus on how these volcanoes excavate the country rock and develop during an eruption. This study aims to determine the processes and relative timing of activity taking place below the ground surface by combining detailed mapping of three exemplary exposures of diatremes at different structure levels, from dike-widening transition to well-formed diatreme, within the Hopi Buttes volcanic field. Observations from different volcanoes are readily related to one another because the field had homogeneous preeruption hydrology, wall-rock stratigraphy, and magma composition, with a narrow range of eruption ages. Castle Butte Trading Post (CBTP) comprises four closely spaced narrow spatter-dikes and wider maar-diatremes ~150 m below the pre-eruptive surface. The spatter-dikes consist of bedded, variably welded deposits plus wall-rock debris in multiple NEyounging sequences demarcated by truncation surfaces. They reveal a shallow plumbing cycle of pulsating, weak, hot spatter fragmentation, concurrent wall-rock failure and periodic slips that truncated down dropped bedded deposits from repeated magma withdrawal and diversions during progressive NE fissure extension and vent stepping. Both Standing Rocks West (SRW) and East (SRE) diatremes, exposed ~300 m below the pre-eruptive surface, are part of a single larger volcanic complex formed along a series of irregularly offset NW-SE trending dikes. SRW comprises dominantly multiple, structureless irregular columns of well-mixed, poorly sorted juvenile-rich lapilli tuff deposits that contain abundant recycled material; they truncate local marginal layered deposits and peripheral country rock breccia. SRW mostly records late-stage activity of multiple, small-volume, explosions and jets within loose pyroclastic debris, which resulted in gradual mixing, recycling and remobilization of cognate diatreme debris, incremental addition of juvenile material and a well-formed diatreme. In contrast, SRE comprises predominantly country rock lithic-rich breccia of coarse inhomogeneously mixed wall-rock blocks, cross-cut by domains of lapilli tuff deposits that are overlain by spatter deposits and cross-cut by irregularly distributed dikes. SRE shows a progressive transition from fissure to diatreme, but an overall evolution from explosive to weak eruption styles, thus reflecting an arrested diatreme. Instead of simply representing vertical differences of a diatreme structure, CBTP, SRE and SRW reveal much volcano-to-volcano variation, and even within-eruption variation in eruption processes and intensity. Variability in eruption intensity is inferred at all scales i.e. between different en echelon dike systems, between the structures formed along segments within these systems and between the vents for individual volcanoes at the surface. These Hopi Buttes volcanoes show that the roots of weakly and strongly explosive small volcanoes are shared with changes in explosive intensity over short distances and not necessarily systematic variations in behaviour through time. The evolution of the shallow plumbing during an eruption involves local feedback effects that critically affect eruption style over short times and distances. Neither magma composition nor country-rock hydrology can be considered as the primary control on inter-eruption variation or on changes through a single eruption in the Hopi Buttes volcanic field. OURArchive handle The handle from the Otago University Research Archive (OURArchive) <a href="http://hdl.handle.net/10523/4268">http://hdl.handle.net/10523/4268</a> OURArchvive access level Abstract Only Department The department where the student is studying primarily. Geology Named locality Named locality describing the field area location. Hopi Buttes volcanic field Navajo Nation Arizona USA. Thesis description Number of pages, maps, CDs, etc. x, 279 leaves plus papers. Maps in colour in text; 30cm. Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Identifier An unambiguous reference to the resource within a given context 2013Lefebvre Creator An entity primarily responsible for making the resource Lefebvre, Nathalie Date A point or period of time associated with an event in the lifecycle of the resource 2013 Title A name given to the resource Volcanology of maar-diatreme volcanic vent complexes, Hopi Buttes Volcanic Field, Navajo Nation, Arizona, USA Subject The topic of the resource Volcanology diatreme fissure Hopi Buttes maar monogenetic root zone shallow plumbing volcanism https://theses.otagogeology.org.nz/files/original/d63c34745f52b6d20eb179916555e303.pdf 52a198a7321c7e4bc81a25c93ee14a08 Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Geology theses OU Geology thesis Thesis or dissertation completed by University of Otago Geology students Author last name Last name of the Author Murtagh Project type Is it an MSc, PhD, BSc(Hons) or PGDipSci? PhD Advisers Who supervised/advised this student White, J.D.L. Abstract The Abstract for this thesis Explosive basaltic eruptions present a challenge to modelling volcanic behaviour. The main focus of this thesis is the examination of pyroclastic micro-textures and morphology of the ash fraction in order to constrain the conduit conditions during ascent and at the time of fragmentation, respectively in the lead up to such explosive volcanic eruptions. Three sites, Black Point, California, Pahvant Butte, Utah and Ilchulbong, Korea, were considered. I propose that, in certain cases, conduit processes can collaborate to modify basaltic magma rheology, which can be complemented by powerful water-magma interactions to result in an intense and violent eruption. Results of micro-textural data show: (1) vesicularity of shallow subaqueous basaltic (“Surtseyan") tephra can reach high values (up to 92% at Pahvant Butte) and vesicularity ranges are broad (e.g. from 6% to 92%, for Pahvant Butte pre-emergent mound). Quantitative values combined with textural observations (e.g. vesicle shape and pattern) indicate a strong heterogeneity of vesiculating magma. (2) vesicle number densities are high (the minimum is at Black Point, 5.4 x 102 vesicles per mm3 and the maximum is seen at both Black Point and Pahvant Butte, 4.8 x 104 vesicles per mm3). Finally, (3) extensive microlite formation is common within Surtseyan pyroclasts examined here. Results of ash morphology analyses show 75% of Black Point ash and 80% of Pahvant Butte ash fragments fall within the hydromagmatic fragmentation field. Furthermore, strong evidence for water-magma interaction (fracture-bound, stepped, cracked and etched surfaces) is seen, as is a dominance of thermohydraulic mechanism of fragmentation. Due to the thermodynamic properties of water and magma this fragmentation regime is considered the most efficient and explosive. A model, common to the three study sites, of shallow conduit conditions and fragmentation leading to eruption is proposed here. Early nucleation at depth is followed by ascent and temporary arrest of magma resulting in a mature (relatively large equivalent diameters) vesicle population and a variable amount of microphenocrysts, both juvenile and xenocrystic. A decompression event, possibly induced by injection of a fresh batch of magma and/or, later in the eruption, flank instability and failure, induces a late stage of bubble nucleation and consequently the final ascent of the magma is rapid and thought to follow a parabolic ascent profile. Simultaneous to rapid ascent microlite nucleation occurs. This burst of nucleation is prompted by high volatile contents (Black Point 0.64-1.92 wt% and Pahvant Butte 0.80-1.29 wt% H2Ot) and decompression. Magma rheology is progressively altered, particularly the viscosity. These processes in combination are sufficient drivers of an explosive eruption. In the Surtseyan cases presented here, conduit processes act to prime the basaltic magma for explosive interaction with an external body of water, however, explosivity cannot be directly linked to the presence of external water alone. In summary, the Surtseyan eruptions presented in this study are interpreted to have been as a result of exceptional conduit conditions which aided explosive eruptive behaviour that is uncharacteristic for basaltic magmas. It is speculated that had these eruptions occurred in a subaerial setting the outcome could have been as dramatic as well documented sub-Plinian and Plinian eruptions. OURArchive handle The handle from the Otago University Research Archive (OURArchive) <a href="http://hdl.handle.net/10523/1982">http://hdl.handle.net/10523/1982</a> OURArchvive access level Open Department The department where the student is studying primarily. Geology Named locality Named locality describing the field area location. USA Thesis description Number of pages, maps, CDs, etc. xi, 242 p. : ill. (some col.) ; 30 cm. + 1 CD-ROM (4 3/4 in.) Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Identifier An unambiguous reference to the resource within a given context 2011Murtagh Creator An entity primarily responsible for making the resource Murtagh, Rachel M. (Rachel Maria) Date A point or period of time associated with an event in the lifecycle of the resource 2011 Title A name given to the resource An investigation into the explosivity of shallow subaqueous basaltic eruptions Subject The topic of the resource Igneous volcanology basalt MFCI Surtseyan eruption Vesicle micro-texture Vesicle number density volcanic ash