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Tectonic evolution of the Eastern Fiordland Gondwana marginScott, James Morfey, n/a January 2008 (has links)
Eastern Fiordland is an eroded Carboniferous to Cretaceous arc assemblage juxtaposed against the Western Fiordland Gondwana continental margin along the Grebe Shear Zone. In the Manapouri region, Eastern Fiordland is composed of scattered metasedimentary and plutonic rocks of Carboniferous, Jurassic and Jurassic-Early Cretaceous age. Quantitative P-T estimates on rare paragneiss assemblages, coupled with LA-ICP-MS analyses of metamorphic overgrowths on detrital zircon grains, demonstrate metamorphism at low to middle amphibolite facies (<6 kbar, c. 600�C) at 145.0 � 2.8 Ma (all quoted errors at 2[sigma]). The Manapouri-Lake Te Anau area of Eastern Fiordland also exposes scattered fragments of the Mesozoic volcano-sedimentary Loch Burn Formation. Relict sedimentary features within this long-lived Early Jurassic to Early Cretaceous unit indicate deposition in a mostly terrestrial or shallow water environment that was fed by debris flows from proximal granitic and volcanic topographic high points. Deposition of the Loch Burn Formation in the Murchison Mountains is bracketed between a 342.3 � 1.5 Ma basal granite and an intrusive 157.6 � 1.4 Ma quartz diorite. Metamorphism throughout the unit achieved greenschist and amphibolite facies temperatures (P unconstrained) in the Early Cretaceous (post c. 148 Ma and prior to c. 121 Ma).
Although metasedimentary rocks provide insights into the tectonic evolution of Eastern Fiordland, a range of compositionally heterogeneous plutonic rocks dominates the geology. At Lake Manapouri, these comprise four principal associations: (1) the composite Pomona Island Granite (Carboniferous-Permian and Jurassic), (2) the Beehive Diorite (148.6 � 2.3 Ma), (3) the heterogeneous Hunter Intrusives (Carboniferous, Jurassic and Early Cretaceous) of the Darran/Median Suite and (4) HiSY granitoid dikes of the Separation Point Suite (123.5 � l.2Ma). The latter suite also occurs in immediately adjacent parts of Western Fiordland, forming the Refrigerator Orthogneiss (120.7 �1.1 Ma), the Puteketeke Granite (120.9 � 0.8 Ma) and the West Arm Leucogranite (116.3 � 1.2 Ma). Geobarometry indicates the Jurassic portions of the Darran/Median Suite were emplaced between 4 - 6 kbar and Western Fiordland Early Cretaceous Separation Point Suite between 5 - 7 kbar. Zircon initial �⁷⁷Hf/�⁷⁶Hf isotopic ratios suggest that Separation Point Suite magma could be derived from the same Paleozoic - Late Neoproterozoic mantle source as the Jurassic portion of the Hunter Intrusives member of the Darran/Median Suite. However, Early Cretaceous plutons west of the Early Cretaceous active margin (and study area) have significantly more evolved source regions, reflecting the influence of continental Gondwana on lithosphere composition. Initial �⁷⁷Hf/�⁷⁶Hf ratios from the Loch Burn Formation Carboniferous basal granite zircon are slightly less primitive than either Darran/Median or Separation Point Suite but nowhere near as evolved as similar-aged zircon in the Eastern Fiordland Mt Crescent Paragneiss unit in the Hunter Mountains.
The Cambrian/Early Ordovician Russet Paragneiss, which lies just west of the Grebe Mylonite Zone in Western Fiordland and has been intruded by a range of Early Paleozoic to Mesozoic plutons, was metamorphosed at 7.5 � 1.2 kbar, 633 � 25�C at 348.6 � 12 Ma and exhibits no evidence for Jurassic re-equilibration. Zircon U-Pb isotopes from a pelitic schist enclave within the Western Fiordland Mt Murrell Amphibolite are interpreted to show that these and associated intrusive rocks were also metamorphosed at kyanite-grade in the Carboniferous. This event, �M1�, generated a pervasive lineation and distinctive pargasite-anorthite-kyanite/corundum-bearing assemblages in layered aluminous components to the Mt Murrell Amphibolite, garnet-amphibole-biotite-kyanite-gedrite-plagioclase-quartz in metasomatised tonalite at the Mt Murrell Amphibolite margins, and low CaO-garnet in pelitic schist enclaves within the amphibolite. P-T estimates suggest M1 took place at 6.6 � 0.8 kbar, 618 � 25�C. Both the timing and P-T conditions of M1 overlap with metamorphism of the Russet Paragneiss. However, the layered amphibolites and pelitic schist enclaves partially re-equilibrated in the Early Cretaceous (c. 115 Ma) at higher pressure (8.8 � 0.9 kbar). This event, �M2�, generated static assemblages of margarite, epidote, chlorite, oligoclase-andesine and second-generation kyanite in the layered amphibolites and relict olivine gabbronorite, and high-CaO garnet rims, biotite, plagioclase, quartz, kyanite and staurolite in the pelitic schist enclaves. Trace element chemistries of c. 340 Ma zircon grains in the schist have unusual smoothed Ce/Ce* anomalies and high Th/U ratios. These properties may be result of fluid flow and metasomatism from the enveloping amphibolite during imposition of the penetrative M1 lineation. Early Cretaceous (c. 115 Ma) zircon overgrowths and chemistries (low heavy rare earth elements, low Th/U ratios, large Eu/Eu* anomalies) are compatible with formation in the presence of local M2 garnet and plagioclase. M2 was coeval with amphibolite to garnet-granulite facies metamorphism of the regionally extensive Western Fiordland Orthogneiss and Arthur River Complex, thus demonstrating that high-pressure metamorphism was not restricted to the Western Fiordland Early Cretaceous components and their marginal metasedimentary rocks.
The Grebe Mylonite Zone forms a lithologic, metamorphic, isotopic and structural boundary between Eastern and Western Fiordland. This 200 to 300 metre-wide and > 50 km long north-striking mylonitic zone is the prominent manifestation of deformation associated with the wider (c. 30 km) Grebe Shear Zone, which extends into Eastern and Western Fiordland. Qualitative and quantitative P-T estimates indicate the currently exposed level of the Grebe Mylonite Zone was active at amphibolite facies conditions (c. 600�C and c. 6 kbar). Coupled U-Pb and Ar-Ar data indicate the mylonite zone was active at, or between, c. 128 and 116 Ma. Temperature-time profiles constructed along a transect perpendicular to the shear zone, used in conjunction with fabric data and the orientation of nearby Tertiary unconformities, suggest that the currently sub-vertical shear zone was rotated during the Cenozoic from an initially steeply east-dipping geometry with a reverse sense of shear. This style of deformation is consistent with an inclined continuously partitioned transpressional structure. Synkinematic emplacement and deformation of the Refrigerator Orthogneiss implies that Grebe Shear Zone provided a crustal anisotropy that facilitated the movement and emplacement of some Separation Point Suite magmas through the crust.
Data collected here are interpreted to show that the Grebe Shear Zone is a terrane-bounding suture. Differences in metasedimentary rock composition, age, provenance and metamorphism across the zone suggest that the crustal framework to Eastern Fiordland did not forth in its current tectonic position. Instead, the Mesozoic portion of Eastern Fiordland is inferred to have developed allochthonously with respect to Western Fiordland, with components internally dismembered and rearranged during Jurassic metamorphism and juxtaposition in the Early Cretaceous. However, the Jurassic portion of the arc may have developed near the Gondwana margin because the Jurassic Borland Paragneiss contains detritus that can be partly matched to sources in the Western and Eastern Provinces of New Zealand, as well as early parts of the Darran/Median Suite and Loch Burn Formation. Recognition that the Eastern Fiordland arc was faulted against and then over Western Fiordland in the Early Cretaceous provides a possible driving mechanism for coeval transpressive shortening, rapid burial and high-pressure metamorphism (e.g., as seen in the Mt Murrell Amphibolite) of the lower Western Fiordland crust.
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The acoustic behaviour of resident bottlenose dolphins in Fiordland, New ZealandBoisseau, Oliver, n/a January 2005 (has links)
The bottlenose dolphin Tursiops truncatus is an extremely well-studied species. We have an extensive knowledge of certain aspects of their vocal behaviour, particularly from captive contexts. Bottlenose dolphins produce a rich tapestry of vocalisations, however, which have historically received minimal attention. Resident groups of bottlenose dolphins frequent the waterways of Fiordland in southwest New Zealand. These deep, sheltered fiords are ideally suited for acoustic studies.
This thesis presents the first detailed study of bottlenose dolphin acoustics in New Zealand. Both narrowband and broadband systems were used to record the vocalisations of two resident groups. Effort was distributed evenly over three years for both Doubtful Sound and Milford Sound. From 875 recordings, I proposed a repertoire of 15 discrete calls. These categories were subsequently compared using parameters measured from almost 2000 individual vocalisations. Various multivariate techniques revealed some redundancy in the proposed repertoire, and it was subsequently reduced to 12 calls.
The 12 call repertoire was compared between the potentially interbreeding populations of Doubtful Sound and Milford Sound. Fiord-specificity was revealed for many of the calls, particularly the sequenced calls and whistles. These differences suggest bottlenose dolphins use dialects, in keeping with studies of killer whales and sperm whales. As Fiordland dolphins are out of sight for 90% of the time, acoustic techniques allow inference in to subsurface behaviour. I investigated sequential relationships among sounds and between sounds and behaviours. Many calls were strongly implicated in social interactions. The vocalisations ratchet, orca and the sequenced calls were associated with periods of conflict. A number of the click-based calls were linked to diving and presumed foraging events.
Inference on the functional significance of sounds allowed an interpretation of habitat use. This appears to be the first study relating the entire vocal repertoire of a cetacean population to a complete home range. Areas important for socialising, foraging and resting are proposed. Local management decisions may be well served by this information. This study uses benign techniques to build on previous research in Fiordland, and adds a new dimension to the study of these populations.
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Tectonic evolution of the Eastern Fiordland Gondwana marginScott, James Morfey, n/a January 2008 (has links)
Eastern Fiordland is an eroded Carboniferous to Cretaceous arc assemblage juxtaposed against the Western Fiordland Gondwana continental margin along the Grebe Shear Zone. In the Manapouri region, Eastern Fiordland is composed of scattered metasedimentary and plutonic rocks of Carboniferous, Jurassic and Jurassic-Early Cretaceous age. Quantitative P-T estimates on rare paragneiss assemblages, coupled with LA-ICP-MS analyses of metamorphic overgrowths on detrital zircon grains, demonstrate metamorphism at low to middle amphibolite facies (<6 kbar, c. 600�C) at 145.0 � 2.8 Ma (all quoted errors at 2[sigma]). The Manapouri-Lake Te Anau area of Eastern Fiordland also exposes scattered fragments of the Mesozoic volcano-sedimentary Loch Burn Formation. Relict sedimentary features within this long-lived Early Jurassic to Early Cretaceous unit indicate deposition in a mostly terrestrial or shallow water environment that was fed by debris flows from proximal granitic and volcanic topographic high points. Deposition of the Loch Burn Formation in the Murchison Mountains is bracketed between a 342.3 � 1.5 Ma basal granite and an intrusive 157.6 � 1.4 Ma quartz diorite. Metamorphism throughout the unit achieved greenschist and amphibolite facies temperatures (P unconstrained) in the Early Cretaceous (post c. 148 Ma and prior to c. 121 Ma).
Although metasedimentary rocks provide insights into the tectonic evolution of Eastern Fiordland, a range of compositionally heterogeneous plutonic rocks dominates the geology. At Lake Manapouri, these comprise four principal associations: (1) the composite Pomona Island Granite (Carboniferous-Permian and Jurassic), (2) the Beehive Diorite (148.6 � 2.3 Ma), (3) the heterogeneous Hunter Intrusives (Carboniferous, Jurassic and Early Cretaceous) of the Darran/Median Suite and (4) HiSY granitoid dikes of the Separation Point Suite (123.5 � l.2Ma). The latter suite also occurs in immediately adjacent parts of Western Fiordland, forming the Refrigerator Orthogneiss (120.7 �1.1 Ma), the Puteketeke Granite (120.9 � 0.8 Ma) and the West Arm Leucogranite (116.3 � 1.2 Ma). Geobarometry indicates the Jurassic portions of the Darran/Median Suite were emplaced between 4 - 6 kbar and Western Fiordland Early Cretaceous Separation Point Suite between 5 - 7 kbar. Zircon initial �⁷⁷Hf/�⁷⁶Hf isotopic ratios suggest that Separation Point Suite magma could be derived from the same Paleozoic - Late Neoproterozoic mantle source as the Jurassic portion of the Hunter Intrusives member of the Darran/Median Suite. However, Early Cretaceous plutons west of the Early Cretaceous active margin (and study area) have significantly more evolved source regions, reflecting the influence of continental Gondwana on lithosphere composition. Initial �⁷⁷Hf/�⁷⁶Hf ratios from the Loch Burn Formation Carboniferous basal granite zircon are slightly less primitive than either Darran/Median or Separation Point Suite but nowhere near as evolved as similar-aged zircon in the Eastern Fiordland Mt Crescent Paragneiss unit in the Hunter Mountains.
The Cambrian/Early Ordovician Russet Paragneiss, which lies just west of the Grebe Mylonite Zone in Western Fiordland and has been intruded by a range of Early Paleozoic to Mesozoic plutons, was metamorphosed at 7.5 � 1.2 kbar, 633 � 25�C at 348.6 � 12 Ma and exhibits no evidence for Jurassic re-equilibration. Zircon U-Pb isotopes from a pelitic schist enclave within the Western Fiordland Mt Murrell Amphibolite are interpreted to show that these and associated intrusive rocks were also metamorphosed at kyanite-grade in the Carboniferous. This event, �M1�, generated a pervasive lineation and distinctive pargasite-anorthite-kyanite/corundum-bearing assemblages in layered aluminous components to the Mt Murrell Amphibolite, garnet-amphibole-biotite-kyanite-gedrite-plagioclase-quartz in metasomatised tonalite at the Mt Murrell Amphibolite margins, and low CaO-garnet in pelitic schist enclaves within the amphibolite. P-T estimates suggest M1 took place at 6.6 � 0.8 kbar, 618 � 25�C. Both the timing and P-T conditions of M1 overlap with metamorphism of the Russet Paragneiss. However, the layered amphibolites and pelitic schist enclaves partially re-equilibrated in the Early Cretaceous (c. 115 Ma) at higher pressure (8.8 � 0.9 kbar). This event, �M2�, generated static assemblages of margarite, epidote, chlorite, oligoclase-andesine and second-generation kyanite in the layered amphibolites and relict olivine gabbronorite, and high-CaO garnet rims, biotite, plagioclase, quartz, kyanite and staurolite in the pelitic schist enclaves. Trace element chemistries of c. 340 Ma zircon grains in the schist have unusual smoothed Ce/Ce* anomalies and high Th/U ratios. These properties may be result of fluid flow and metasomatism from the enveloping amphibolite during imposition of the penetrative M1 lineation. Early Cretaceous (c. 115 Ma) zircon overgrowths and chemistries (low heavy rare earth elements, low Th/U ratios, large Eu/Eu* anomalies) are compatible with formation in the presence of local M2 garnet and plagioclase. M2 was coeval with amphibolite to garnet-granulite facies metamorphism of the regionally extensive Western Fiordland Orthogneiss and Arthur River Complex, thus demonstrating that high-pressure metamorphism was not restricted to the Western Fiordland Early Cretaceous components and their marginal metasedimentary rocks.
The Grebe Mylonite Zone forms a lithologic, metamorphic, isotopic and structural boundary between Eastern and Western Fiordland. This 200 to 300 metre-wide and > 50 km long north-striking mylonitic zone is the prominent manifestation of deformation associated with the wider (c. 30 km) Grebe Shear Zone, which extends into Eastern and Western Fiordland. Qualitative and quantitative P-T estimates indicate the currently exposed level of the Grebe Mylonite Zone was active at amphibolite facies conditions (c. 600�C and c. 6 kbar). Coupled U-Pb and Ar-Ar data indicate the mylonite zone was active at, or between, c. 128 and 116 Ma. Temperature-time profiles constructed along a transect perpendicular to the shear zone, used in conjunction with fabric data and the orientation of nearby Tertiary unconformities, suggest that the currently sub-vertical shear zone was rotated during the Cenozoic from an initially steeply east-dipping geometry with a reverse sense of shear. This style of deformation is consistent with an inclined continuously partitioned transpressional structure. Synkinematic emplacement and deformation of the Refrigerator Orthogneiss implies that Grebe Shear Zone provided a crustal anisotropy that facilitated the movement and emplacement of some Separation Point Suite magmas through the crust.
Data collected here are interpreted to show that the Grebe Shear Zone is a terrane-bounding suture. Differences in metasedimentary rock composition, age, provenance and metamorphism across the zone suggest that the crustal framework to Eastern Fiordland did not forth in its current tectonic position. Instead, the Mesozoic portion of Eastern Fiordland is inferred to have developed allochthonously with respect to Western Fiordland, with components internally dismembered and rearranged during Jurassic metamorphism and juxtaposition in the Early Cretaceous. However, the Jurassic portion of the arc may have developed near the Gondwana margin because the Jurassic Borland Paragneiss contains detritus that can be partly matched to sources in the Western and Eastern Provinces of New Zealand, as well as early parts of the Darran/Median Suite and Loch Burn Formation. Recognition that the Eastern Fiordland arc was faulted against and then over Western Fiordland in the Early Cretaceous provides a possible driving mechanism for coeval transpressive shortening, rapid burial and high-pressure metamorphism (e.g., as seen in the Mt Murrell Amphibolite) of the lower Western Fiordland crust.
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The Structural Evolution Of A Portion Of The Median Batholith And Its Host Rock In Central Fiordland, New Zealand: Examples Of Partitioned Transpression And Structural ReactivationBlatchford, Hannah Jane 01 January 2016 (has links)
This thesis presents the results of structural analyses and detailed field mapping from a region near Adams Burn in central Fiordland, New Zealand. The region preserves assemblages of metasedimentary and metaigneous rocks deposited, intruded, and ultimately metamorphosed and deformed during the growth of a Gondwana-margin continental arc from Cambrian-Early Cretaceous. Evidence of arc growth is preserved in the Late Devonian-Early Cretaceous Median Batholith, a belt of intrusive rock whose growth culminated with the emplacement of the Western Fiordland Orthogneiss (WFO) into the middle-lower crust of the margin. Following this magmatic flare-up, the margin experienced Late Cretaceous extensional orogenic collapse and rifting. During the Late Tertiary, the margin records oblique convergence that preceded the Alpine fault. The history of arc growth and record of changing tectonic and deformational regimes makes the area ideal for study of structural reactivation during multiple cycles of magmatism, metamorphism and deformation, including during a mid-lower crust magma flare-up.
Structural and lithologic mapping, structural analyses, and cross-cutting relationships between superposed structures and three intrusions were used to bracket the relative timing of four tectonic events (D1-D4), spanning the Paleozoic to the Tertiary. The oldest event (D1) created a composite fabric in the metasedimentary and metaigneous rocks of the Irene Complex and Jaquiery granitoid gneiss prior to emplacement of the Carboniferous Cozette pluton. S1 foliation development, set the stage for structural reactivation during the second phase of deformation (D2), where S1 was folded and reactivated via intra-arc shearing. These second-phase structures were coeval with the emplacement of the Misty pluton, (part of WFO in central Fiordland), and record crustal thickening and deformation involving a kinematically partitioned style of transpression. Arc-normal displacements were localized into the rocks of the Irene Complex. Oblique displacements were localized along the Misty-Cozette plutonic contact, forming a ≥1 km-wide, upper amphibolite-facies gneissic shear zone that records sinistral-reverse offset. Second-phase structures are cross-cut by widespread leucocratic pegmatite dikes. S2 in the Cozette and Misty plutons is reactivated by localized, ≤10 m-thick, greenschist-facies (ultra)mylonitic shear zones that record sinistral-normal offsets. S3/L3 shear zones and lithologic contacts were then reactivated by two episodes of Tertiary, fourth-phase faulting compatible with Alpine faulting, everywhere truncating the pegmatite dikes. Early faults accommodated shortening normal to the Alpine fault, and were obliquely reactivated by a younger population of faults during dextral transpression.
My results show that structural reactivation occurred repeatedly after D1, and that structural inheritance played a key role in the geometry, distribution, and kinematics of younger deformation events throughout the arc's history. The sheeted emplacement of the Misty pluton was accompanied, and possibly facilitated, by a system of partitioned transpression during Early Cretaceous crustal thickening and arc magmatism. These results show that transpression helped accommodate and move magma through the middle and lower crust during the flare-up. This conclusion is important for the study of continental arcs globally, as evidence of deformation during high-flux magmatism at lower crustal depths (~40 km) is rarely preserved and exhumed to the surface.
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The interplay between deformation and metamorphism during strain localization in the lower crust: Insights from Fiordland, New ZealandDianiska, Kathryn Elise 01 January 2015 (has links)
In this thesis, I present field, microstructural, and Electron Backscatter Diffraction (EBSD) analyses of rock fabrics from high strain zones in exposures of lower crustal Cretaceous plutons at Breaksea Entrance, Fiordland, New Zealand. The interplay between deformation and metamorphism occurs across multiple scales at the root of a continental arc. I show a series of steps in which retrogressive metamorphism is linked to the accommodation of deformation.
I define three main phases of deformation and metamorphism at Breaksea Entrance. The first phase (D1) involved emplacement of dioritic to gabbroic plutons at depths up to 60 km. The second phase (D2) is characterized by deformation and metamorphism at the granulite and eclogite facies that produced high strain zones with linear fabrics, isoclinal folding of igneous layering, and asymmetric pressure shadows around mafic aggregates. New structural analyses from Hāwea Island in Breaksea Entrance reveal the development of doubly plunging folds that define subdomes within larger, kilometer-scale gneiss domes. The development and intensification of S2 foliations within the domes was facilitated by the recrystallization of plagioclase and clinopyroxene at the micro-scale (subgrain rotation and grain boundary migration recrystallization), consistent with metamorphism at the granulite and eclogite facies and climb-accommodated dislocation creep. EBSD data show a strong crystallographic preferred orientation in plagioclase during D2 deformation. The third phase (D3) is characterized by deformation and metamorphism at the upper amphibolite facies that produced sets of discrete, narrow shear zones that wrap and encase lozenges of older fabrics. Structural analyses reveal a truncation and/or transposition relationship between the older S2 and the younger S3 foliations developed during D3. Progressive localization of deformation during cooling, hydration, and retrogression, resulted in the breakdown of garnet and pyroxene to form hornblende, biotite, fine plagioclase and quartz. EBSD data show a strong crystallographic preferred orientation in hornblende. During D3, hornblende and biotite accommodated most of the strain through fluid-assisted diffusion creep.
The last two events (D2 and D3) reflect a transition in deformation and metamorphism during exhumation, as well as a focusing of strain and evolving strain localization mechanisms at the root of a continental arc. An examination of structures at multiple scales of observation reveals that fabrics seen in the field are a composite of multiple generations of deformation and metamorphism.
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Strain Accommodation, Metamorphic Evolution, And 3d Kinematics Of Transpressional Flow Within The Lower Crust Of A Cretaceous Magmatic Arc In Fiordland, New ZealandMoyer, Griffin Amoss 01 January 2019 (has links)
The George Sound Shear Zone (GSSZ) exposed in Bligh Sound within Fiordland, New Zealand allowed us to reconstruct the kinematics of transpressive flow in >100 km2 of exhumed Cretaceous lower crust. We compare the three-dimensional characteristics of the deformation to theoretical models of transpression that assume steady-state flow in a homogeneous medium. This assumption is rarely the case for shear zones that experience metamorphism during deformation. We determined the three-dimensional kinematics of the GSSZ and evaluated the effects of metamorphism on strain accommodation and structural fabric evolution in the GSSZ to determine if metamorphism is an important parameter that transpressional models should account for. We found that metamorphism aided strain localization within the GSSZ and resulted in a style of structural fabric development that deviates from predictions made by theoretical models.
We used foliation and lineation orientation data and field observations to determine GSSZ kinematics. Asymmetric pyroxene σ-porphyroclasts and hornblende fish show top-down-to-the-SW apparent normal shear sense with a sinistral component. The Z-axes of oblate SPO ellipsoids define the vorticity normal section and the moderately WNW-plunging vorticity vector. Foliation deflections relative to the shear zone boundaries yielded a vorticity magnitude (Wk) of ≥0.8. Our kinematic results suggest that the GSSZ records inclined, triclinic transpression with sinistral, top-down-to-the-SW simple shear-dominated flow.
We used finite strain analysis and petrographic analysis to determine that metamorphism influences strain accommodation. Finite strain analyses were performed in 3D on 16 samples using the Rf/ɸ, Fry, and Intercept methods to determine the SPO fabric ellipsoids at different stages of deformation. Petrographic analysis was performed to identify metamorphic reactions using syn-kinematic minerals and constrain deformational temperatures using deformation mechanisms of plagioclase. Early deformation formed a ~13 km wide prolate fabric at granulite facies. Deformation later localized into a ~2-4.6 km wide oblate, mylonitic fabric at upper amphibolite facies. This fabric cross-cuts the prolate fabric and is characterized by metamorphic hornblende and biotite produced from retrogressive hydration reactions. Samples with syn-kinematic biotite contain more shear bands and display more grain size reduction of plagioclase than samples without this phase, suggesting these samples may have accommodated more strain. Changes in syn-kinematic metamorphic minerals were accompanied by steepening of stretching lineations and by changes in foliation orientation.
Our analyses show that retrogressive hydration metamorphism aided strain localization within a cross-cutting oblate fabric, and the uneven distribution of biotite within this domain potentially influenced along strike variation in strain magnitude and fabric ellipsoid symmetry. Our results highlight the influence of fluid-induced metamorphism on shear zone evolution and call for new transpressional models to incorporate changes in rheology due to syn-kinematic metamorphism.
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The geology of central southern Fiordland : with emphasis on the cause of polybaric Cretaceous metamorphism in western New ZealandPowell, Nicholas Garth, n/a January 2007 (has links)
Central southern Fiordland, New Zealand, is underlain extensively by metasediments and associated metavolcanics. These are mapped in three lithostratigraphic units, from west to east Edgecumbe Group, Cameron Group and Cumbrae Supergroup. Lower Cameron Group units lithocorrelate with Central Fiordland Belt lithological associations and with those of Fraser Complex, Westland.
Eastern Fiordland Belt metavolcanics and lacustrine metasediments are tectonostratigraphically unrelated to Cameron Group, from which they are separated by the Grebe Fault. They instead have affiliations with the Loch Burn Formation, Largs Volcanics, Drumduan Group and Paterson Group. These units (collectively, "Cumbrae Supergroup") represent remnants of a Triassic-Jurassic calc-alkaline arc.
Six deformational episodes are identified in central southern Fiordland. The earliest, D₁, is obliterated by D₂ and M₂ metamorphism. D₃ is restricted to the Southwest Fiordland Block. D₄ occupied a brief interval of M₃ time. D₄ of the Central and Western Fiordland Belts corresponds to earliest deformation in Eastern Fiordland Belt metavolcanics. The Grebe Fault is a left-lateral reverse D₄ fault; now vertical, it previously dipped eastward. The Dusky Fault, a reactivated D₅ left-lateral transfer structure, accommodated the dip-slip component of displacement at low-angle normal faults during mid-Cretaceous extension. Open folds represent D₆. Post-glacial scarps mark the post-D₆ Kilcoy and Vincent Faults. Their merged northward continuation is intersected by the tailrace tunnel of the Manapouri Hydroelectric Power Station.
Southwest Fiordland Block pelites were metamorphosed at 665 �C, c. 3 kbar during M₂. Early M₃ is of contact metamorphic aspect. Late M₃ is distinctively polybaric: Central Fiordland Belt kyanite-garnet pelites recrystallised at c. 8.5 kbar after metamorphism in the sillimanite field at c. 3.5 kbar. Western Fiordland Orthogneiss 12 kbar granulite assemblages formed during late M₃. South of the Dusky Fault, late M₃ is almost asymptomatic. The M₃ field gradient is continuous across the Grebe Fault: in the Eastern Fiordland Belt, late M₃ staurolite and garnet supersede chloritoid in lacustrine (meta-)sapropel-silts.
The Grebe Fault is an important tectonostratigraphic break; it may separate New Zealand�s Western and Eastern Provinces. Its relationship to any "Median Tectonic Zone" is unclear, as no such zone has been found in southeastern Fiordland. Cumbrae Supergroup rocks within the "Median Tectonic Zone" represent the arc that nourished the Eastern Province�s Barretts Formation, Murihiku Supergroup and Stephens Subgroup. The Cumbrae arc was �obducted� westwards during Early Cretaceous continent-arc collision. This event simultaneously halted Eastern Province volcanogenic sedimentation and tectonically buried Fiordland, imposing late M₃ pressure increments. Drumduan Group lawsonite is coeval.
Cretaceous collision induced glaciation. Late Cretaceous climatic deterioration and extensional tectonism caused icecap development. The Otago "Peneplain" is a Late Cretaceous subglacial floor. Accumulation of voluminous perennial Cretaceous ice on Earth has hitherto not been inferred.
Facultative psychrophily in New Zealand�s ancient endemics and their preference for dark conditions reflect passage through a hitherto-unsuspected evolutionary bottleneck: prolonged winter darkness and harsh climate of near-polar Late Cretaceous New Zealand exerted extraordinary evolutive pressures on ancestral forms after biotic links with Gondwana were severed. New Zealand�s ancient endemics are the evolutionary derivatives of a Late Cretaceous near-polar fauna.
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Conservation biology of bottlenose dolphins in Fiordland, New ZealandCurrey, Rohan J. C, n/a January 2009 (has links)
The bottlenose dolphins of Fiordland, New Zealand, live at the southern limit of the species' worldwide range. They are exposed to impacts from tourism and habitat modification, particularly in Doubtful Sound, and their conservation requirements are presently unclear. Dolphin abundance was estimated in Doubtful Sound using photo-identification census and capture-recapture techniques (56 individuals; 95% CI: 55-57), detecting a decline of 34-39% over 12 years among adults and sub-adults (>3 years old). The cause of this decline was investigated via demographic modelling in Doubtful Sound and a comparative assessment of population status in Dusky Sound.
Capture-recapture modelling of photo-identification data compiled since 1990 yielded a constant adult survival rate marginally lower than prior estimates for wild bottlenose dolphins ([phi]a(1990-2008) = 0.9374; 95% CI: 0.9170-0.9530). Survival of calves (<1 year old) declined to an unsustainable level that is thought to be the lowest recorded for wild bottlenose dolphins ([phi]c(2002-2008) = 0.3750; 95% CI: 0.2080-0.5782) coincident with the opening of a second tailrace tunnel for a hydroelectric power station. Reverse-time capture-recapture modelling detected declines in recruitment (f(1994-2008) = 0.0249; 95% CI: 0.0174-0.0324) and population growth ([lambda](1994-2008) = 0.9650; 95% CI: 0.9554-0.9746) over time consistent with the decline in calf survival (<1 year old) and a separate reduction in juvenile survival (1 to 3 years old) reflecting cumulative impacts.
Dolphin abundance was estimated in Dusky Sound using photo-identification census and capture-recapture techniques (102 individuals, 95% CI: 100-104) providing no evidence of interchange with Doubtful Sound. A comparative assessment of health status between Doubtful and Dusky Sounds revealed skin lesioning was more severe in Doubtful Sound, particularly among females, and newborn calves appeared to be smaller and were born over a shorter period: factors that may contribute to the low levels of calf survival in Doubtful Sound. The Fiordland bottlenose dolphins were assessed under IUCN Red List regional criteria. The small size of the population (205 individuals, 95% CI: 192-219) combined with the projected rate of decline in stochastic matrix models (average decline 31.4% over one generation) resulted in a recommended classification of Critically Endangered.
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The geology of central southern Fiordland : with emphasis on the cause of polybaric Cretaceous metamorphism in western New ZealandPowell, Nicholas Garth, n/a January 2007 (has links)
Central southern Fiordland, New Zealand, is underlain extensively by metasediments and associated metavolcanics. These are mapped in three lithostratigraphic units, from west to east Edgecumbe Group, Cameron Group and Cumbrae Supergroup. Lower Cameron Group units lithocorrelate with Central Fiordland Belt lithological associations and with those of Fraser Complex, Westland.
Eastern Fiordland Belt metavolcanics and lacustrine metasediments are tectonostratigraphically unrelated to Cameron Group, from which they are separated by the Grebe Fault. They instead have affiliations with the Loch Burn Formation, Largs Volcanics, Drumduan Group and Paterson Group. These units (collectively, "Cumbrae Supergroup") represent remnants of a Triassic-Jurassic calc-alkaline arc.
Six deformational episodes are identified in central southern Fiordland. The earliest, D₁, is obliterated by D₂ and M₂ metamorphism. D₃ is restricted to the Southwest Fiordland Block. D₄ occupied a brief interval of M₃ time. D₄ of the Central and Western Fiordland Belts corresponds to earliest deformation in Eastern Fiordland Belt metavolcanics. The Grebe Fault is a left-lateral reverse D₄ fault; now vertical, it previously dipped eastward. The Dusky Fault, a reactivated D₅ left-lateral transfer structure, accommodated the dip-slip component of displacement at low-angle normal faults during mid-Cretaceous extension. Open folds represent D₆. Post-glacial scarps mark the post-D₆ Kilcoy and Vincent Faults. Their merged northward continuation is intersected by the tailrace tunnel of the Manapouri Hydroelectric Power Station.
Southwest Fiordland Block pelites were metamorphosed at 665 �C, c. 3 kbar during M₂. Early M₃ is of contact metamorphic aspect. Late M₃ is distinctively polybaric: Central Fiordland Belt kyanite-garnet pelites recrystallised at c. 8.5 kbar after metamorphism in the sillimanite field at c. 3.5 kbar. Western Fiordland Orthogneiss 12 kbar granulite assemblages formed during late M₃. South of the Dusky Fault, late M₃ is almost asymptomatic. The M₃ field gradient is continuous across the Grebe Fault: in the Eastern Fiordland Belt, late M₃ staurolite and garnet supersede chloritoid in lacustrine (meta-)sapropel-silts.
The Grebe Fault is an important tectonostratigraphic break; it may separate New Zealand�s Western and Eastern Provinces. Its relationship to any "Median Tectonic Zone" is unclear, as no such zone has been found in southeastern Fiordland. Cumbrae Supergroup rocks within the "Median Tectonic Zone" represent the arc that nourished the Eastern Province�s Barretts Formation, Murihiku Supergroup and Stephens Subgroup. The Cumbrae arc was �obducted� westwards during Early Cretaceous continent-arc collision. This event simultaneously halted Eastern Province volcanogenic sedimentation and tectonically buried Fiordland, imposing late M₃ pressure increments. Drumduan Group lawsonite is coeval.
Cretaceous collision induced glaciation. Late Cretaceous climatic deterioration and extensional tectonism caused icecap development. The Otago "Peneplain" is a Late Cretaceous subglacial floor. Accumulation of voluminous perennial Cretaceous ice on Earth has hitherto not been inferred.
Facultative psychrophily in New Zealand�s ancient endemics and their preference for dark conditions reflect passage through a hitherto-unsuspected evolutionary bottleneck: prolonged winter darkness and harsh climate of near-polar Late Cretaceous New Zealand exerted extraordinary evolutive pressures on ancestral forms after biotic links with Gondwana were severed. New Zealand�s ancient endemics are the evolutionary derivatives of a Late Cretaceous near-polar fauna.
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Movements, population dynamics and predatory behaviour of stoats inhabiting alpine grasslands in FiordlandSmith, Derek, n/a January 2006 (has links)
Stoats are introduced mammalian carnivores implicated in the decline of several of New Zealand�s endemic species. Most research into stoats in New Zealand has focused on beech forest habitat, especially in years of peak stoat abundance following heavy beech seedfall and peak cohorts of mice. In New Zealand, alpine grasslands occur above the altitudinal limit of beech forest (900-1000 m a.s.l.). Although previous research has shown stoats to be present there, little is known about the ecology of stoats in alpine grasslands. This research aimed to test whether alpine grasslands were a marginal habitat occupied by surplus stoats that had spilled over from beech forest populations, i.e. a sink habitat. The alternative is that alpine grasslands are a desirable habitat deliberately exploited by stoats. This question was answered using mark-recapture, radio-tracking, diet analysis and a food addition experiment. Another objective was to determine whether nest survival is higher in alpine grassland compared to beech forest and whether stoats are likely to be a frequent predator of ground nests in alpine grasslands relative to other introduced mammals that inhabit them. If nest survival is higher in alpine grassland then alpine grasslands may be a refuge from predation. However, if it is not then it is important for management to know the relative risk posed by stoats compared with other predators. An artificial nest experiment was used to answer these questions. This research was undertaken during two years of low to intermediate beech seedfall and therefore provided an opportunity to look at the ecology of stoats in a New Zealand National Park outside years of peak abundance. The principal study site for this research was the Borland Valley, Fiordland National Park.
Compositional analysis showed that stoats in alpine grassland selected for it over adjacent beech forest. The range cores of these stoats were high up in alpine grassland away from the ecotone with beech forest. Stoats occurred at similar densities in alpine grasslands as they did in beech forest and observed survival was similar between the two habitats (with the exception of 2004 when it may have been higher in alpine grassland). The most frequent prey of stoats inhabiting beech forest were birds and mice. Although stoats in alpine grasslands also ate birds and mice their most frequent prey were ground weta and hare. Food addition appeared to cause diet switching but did not reduce the distances moved by stoats, suggesting that other factors may be more important in regulating their summer home range size in alpine grasslands. All of these factors lead to the conclusion that alpine grasslands in the Borland are not a marginal habitat for stoats, but may instead be a desirable one. Artificial nests had a higher probability of survival in alpine grassland compared to adjacent beech forest, but survival was too low to support the idea that alpine grasslands are a refuge. Stoats were the most frequent predator of artificial nests in both habitats, but 95 % confidence intervals overlapped the predation rate by possums, which was also high.
These findings illustrate the need for a comprehensive landscape approach to stoat control in montane National Parks, for two reasons: 1) endemic biodiversity in alpine grasslands may be under threat from stoat predation, 2) alpine grasslands may act as a source for dispersing stoats that reinvade lowland stoat control areas. In the absence of heavy beech seedfall and peak mouse abundance, stoats occurred at densities of around 1 km⁻� in both habitats and there was recruitment into these populations. This raises the important question: What regulates the distribution and abundance of stoats in years of low beech seedfall and low mouse abundance? In these years birds, ground weta and hares may be as important as mice are in years of peak abundance following heavy beech seedfall.
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