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Understanding the seismic hazard posed by large earthquakes requires paleoseismic investigation because most faults have not ruptured repeatedly during the period of historic records. However, determining the location and length of fault ruptures using paleoseismic data remains challenging. Our study demonstrates that lake sediments record the high intensity shaking that occurs proximal to fault rupture, allowing the location and length of ruptures to be reconstructed. In two lakes adjacent to the Alpine Fault, New Zealand, seismic shaking is recorded as subaqueous mass-wasting derived turbidites formed by coseismic subaqueous slope failures, which are overlain by sets of hyperpycnites representing elevated fluvial sediment fluxes from earthquake-induced landslides. Precise radiocarbon age models show that shaking events are synchronous between the two lake sites and correlate with the timing of known Alpine Fault earthquakes. Modelled shaking intensities for the last two Alpine Fault earthquakes show that subaqueous mass-wasting occurs when shaking intensities exceed Modified Mercalli scale (MM) VI–VII, and that fluvial sediment fluxes from earthquake-induced landslides occur when shaking intensities exceed MM IX. The data demonstrate that lake records distinguish between strong (MM VI) and violent (MM IX) shaking at a lake site. The ability to map the spatial extent of MM IX shaking provides new insights into the timing and extent of rupture for the last five earthquakes on the Alpine Fault. The study demonstrates that lake deposits constrain the spatial extent of rupture during large earthquakes and may yield long records of the spatial and temporal patterns of fault rupture.

Continental transform faults are dominantly highly localized strike-slip shear zones hundreds of kilometers long that accumulate tens to hundreds of kilometers of displacement. From work on the Alpine Fault, we pose the questions: what is the deep structure of a continental transform, and how does the displacement become localized? We review research on the Alpine Fault and propose a model in which the fault partitions at depth into a steep zone extending into the mantle with largely fault-parallel motion and a flat ductile decollement in the lower crust. The fault localizes around two-thirds of the plate motion within a 100 km wide zone of distributed deformation. A review of other active continental fault systems suggests that variation between them may reflect their tectonic origins, the nature of the crust in which they develop, the presence of a significant oblique component of motion, and the displacement rate. All however have evidence for the development of a single principal fault zone that carries ≥50% of the total displacement and extends as a localized zone of shear into the upper mantle. We review mechanisms of strain weakening and suggest that localization of a principal fault may be initiated in the seismogenic crust and through a series of positive feedbacks eventually extend through the lower crust into the upper mantle.

Lake basins that experience rapid rates of deposition act as high-resolution environmental archives because they produce sedimentary records that have centennial or even decadal resolution. However, identifying target fractions for radiocarbon dating of lake sediments remains problematic because reworked organic material from fluvial catchments can produce anomalously old radiocarbon ages. This study determines the extent to which reworked material from catchment soils impacts radiocarbon dates on pollen and other organic concentrates by comparing radiocarbon dates produced by these techniques against a chronostratigraphic marker in cores from Lake Mapourika, New Zealand. Pollen preferentially preserved and reworked from catchment soils was identified using soil palynology. A technique was then developed to remove reworked pollen types from pollen concentrates extracted from lake sediment. Identification and removal of reworked pollen from pollen concentrates produced ages that were consistently closer to the age of the chronostratigraphic horizon than other organic concentrates. However, these dates were still between 736 and 366 calendar years older than expected. The only organic fractions that reliably reproduced the age of the chronostratigraphic horizon were terrestrial leaf macrofossils, although terrestrial leaf macrofossils isolated from megaturbidite deposits, which are formed by high-energy depositional events, also provided anomalously old ages. The results indicate that leaf material extracted from hemipelagite, which accumulates gradually, is likely to be the only organic fraction to produce reliable chronology in lakes where a component of sedimentation is driven by the fluvial system. The results also demonstrate the importance of conducting a detailed investigation of physical sedimentology before selecting material for radiocarbon dating lake sediments.

Lineations within mylonites exhumed in the hanging wall of New Zealand's active Alpine Fault zone have a complicated relationship to contemporary plate kinematics. The shear zone is triclinic and macroscopic object lineations are not usually parallel to the simple shear direction, despite high total simple shear strains ( γ ≥ 150). This is mostly because the lineations are inherited from pre-mylonitic fabrics, and have not been rotated into parallelism with the mylonitic stretching direction (which pitches c. 44° in the fault plane). Furthermore, some lineations have been variably rotated depending on whether they are present in shear bands or microlithons, which accommodated bulk strains with different vorticities. Total strains required to obtain parallelism between the finite maximum principal stretching direction calculated from transpression models and these mylonitic lineations, are pure shear stretch, S 1 ∼ 3.5; simple shear 11.7 γ

In order to assess how different elements of plate boundary-scale shear zone tectonite fabrics reflect the boundary kinematics and strain history, we have examined a range of such structures within the active Alpine Fault mylonite zone, New Zealand. In this oblique slip zone we find that quartz CPO fabric symmetry and individual mica grain lineations reflect incremental stretches but develop stable orientations parallel to the finite stretching direction (S 1 ). This S 1 trends oblique to the plate motion vector because the shear zone experiences some extrusion toward the free surface. Conversely, asymmetric structures (such as shear bands and mica fish) reflect simple shear-dominated deformation late in the shear zone history, parallel to the imposed relative plate motion vector. Finally, linear fabrics are a poor record of the mylonitic deformation in this zone, because (1) they are dominantly inherited and have been only partially re-oriented during mylonitisation, and (2) macroscopically they become less visible at higher strains due to fabric homogenisation. Generally, these results indicate that, particularly in heterogeneous, polyphase shear zones, a full understanding of the movement history can only be obtained by considering kinematic information from as many different sources as possible.

The thermal state within plate boundary fault zones is likely to influence the dimensions of large co-seismic fault ruptures, and strain localisation in underlying mylonitic shear zones. Vein microstructures, biotite chemistry and fluid inclusion data offer new insights into the thermal structure of the mylonitic shear zone down dip of the Alpine Fault, the main Pacific–Australian plate boundary structure through southern New Zealand. Quartz veins within the fault rocks were formed and deformed at temperatures ranging from > 500 °C to immediately above that of the brittle–viscous transition (∼ 325 °C), illustrating that fluids are present throughout the fault zone. Microthermometric data from primary, mixed CO 2 –H 2 O fluid inclusions in boudin-neck quartz–carbonate veins indicate that these inclusions were trapped at temperatures of 325 ± 15 °C and pressures of c. 40 MPa. Vein microstructures indicate that fluid temperatures were equal to rock temperatures. Assuming hydrostatic fluid pressure, the veins were trapped at depths of 2 O–CO 2 fluids in the shallower crust of > 500 kg m − 3 . Biotite grains in the mylonites are a mixture of porphyroclastic grains with high R = Ti/Mg# inherited from the parent Alpine Schist, and smaller, low R grains that recrystallised during mylonitisation, particularly those that are found within syn-mylonitic shear bands. Assuming a simple step-function model approximating diffusive equilibration, the changes in biotite chemistry indicate Δ T during mylonitic deformation of ∼−340 °C according to the Ti-in-biotite thermometer of Henry et al. (2005). A best-fit uplift P – T path to existing data and these new results indicate that the uplift path P – T gradient of fault zone rocks above the brittle–viscous transition is of the order of 40 °C km − 1 . Below the brittle–viscous transition, the uplift path P – T gradient is 10 °C km − 1 . The P – T profile within the fault rocks is comparable to that in the immediate hanging wall Alpine Schist, indicating there is no peak in the crustal isotherms in the fault hanging wall, as was indicated by previous numerical models, and analyses that did not consider data from the fault rocks themselves.

Strong quartz crystallographic preferred orientations (CPOs) were developed during dislocation creep in the mylonite zone exposed in the hanging wall of the dextral reverse Alpine Fault Zone, New Zealand. The CPOs have a consistent asymmetry indicating a high ratio of simple to pure shear strain, with a shear sense of dextral-up to the NW, consistent with the mesoscopic shear sense indicators and with slip on the active fault. There is a transition from Y-maxima and asymmetric single girdles in mylonites and ultramylonites within 300 m of the present fault trace, to cross-girdle fabrics in the protomylonites further from the fault. The strong Y-maxima or single girdle CPOs are ascribed to high ductile shear strains under amphibolite facies conditions while the cross-girdle patterns found in the protomylonites are interpreted to represent deformation under lower temperature conditions. However, the observed fabric transition cannot logically be attributed to variations in temperature during the last increment of deformation. The highly oriented Y-maximum fabrics formed at high temperature contain very few grains suitably oriented for basal slip, so that the slip systems activated during subsequent shear at lower temperatures during exhumation were prism or rhomb . Further from the fault, where shear strains under high temperature conditions were lower, weaker fabrics developed under these conditions were modified at higher levels in the crust into crossed girdle patterns. This interpretation implies that intense localisation of shear strain along the fault zone within the lower crust must have occurred in order for the high-temperature fabrics to become sufficiently intense to be preserved. This in turn implies that deep-seated localised shear was taking place early during the evolution of the current oblique-slip plate boundary fault. The results of this study also indicate that the current model that operation of certain slip systems in quartz is mostly a function of temperature is incorrect. Future work should consider the effects of deformation history, total strain and the presence of other mineral phases.

Oblique displacement on the Alpine Fault, which forms the principal structure along the Australian–Pacific plate boundary in South Island, New Zealand, has resulted in exhumation of a kilometre-wide mylonite zone in the hanging wall adjacent to the current brittle fault trace. The mylonites formed under amphibolite facies conditions at depths of ca. 25 km and have been uplifted during the past 5 Ma. A suite of 65–70 Ma pegmatite veins in the hanging wall Alpine schists has been progressively deformed within the mylonite zone and sheared out over a strike length of ca. 100 km. Measurements of the thickness distribution of the pegmatite veins within the non-mylonitised schists and at three localities within the progressively strained mylonites have been used to estimate strain values within the mylonites. The thicknesses approximate a log-normal distribution, with a mean value that is progressively reduced through the protomylonites, mylonites and ultramylonites. By assuming that the thickness distribution currently observed in the schists was the same for the pegmatites within the mylonites before strain, a model of deformation incorporating simple shear and simultaneous pure shear is used to strain the undeformed veins until a fit is obtained with the strained distributions. Shear strains calculated range from 12 to 22 for the protomylonites, 120 to 200 for the mylonites and 180 to 300 for the ultramylonites, corresponding to pure shear values of 1–3 in each case. These values are compatible with the strains predicted if most of the surface displacement on the fault over the past 5 Ma were accommodated within a 1–2-km-wide mylonite zone through the middle and lower crusts. The results suggest that processes such as erosional focussing of deformation and thermal weakening may cause intense strain localisation within the lower crust, with plate boundary deformation restricted to narrow zones rather than becoming increasingly distributed over a widening shear zone with depth.

Published geological data on Late Quaternary offsets on the Alpine Fault, New Zealand, have been assembled into a common format and analysed with respect to uncertainties. Uncertainties arise mainly from measurement of offset features, relating apparent offsets to actual fault slip, and dating the offset features. Despite the considerable uncertainties, the data form a coherent set consistent with a relatively constant rate of strike-slip of 27±5 mm/year between Milford Sound and Hokitika. This rate represents 70–75% of the fault-parallel interplate motion. North of the confluence with the Hope Fault, the rate drops substantially. Dip-slip rates, on the other hand, show considerable variation along strike, rising to a maximum of more than 10 mm/year in the central section and decreasing to zero at the southern end. Partitioning of c. 25% of the interplate slip on to structures east of the Alpine Fault occurs in the central section, consistent with predictions from critical wedge models. The partitioning of all the fault-normal component of displacement on to other structures in the south may be related, in part, to a doubling in width of the deforming wedge to the east. Most probably, however, the fault-normal displacement is mainly accommodated by underthrusting of the Australian plate offshore, due to a change in the nature of the crust from continental to oceanic.

The Waikukupa thrust is a 4-km long oblique thrust segment of the New Zealand Alpine Fault that has developed over the last 65,000 years, emplacing mylonite and cataclasite over fluvioglacial gravel. During the last 20,000 years or so, a 2-km long ‘out-of-sequence’ imbricate, the Hare Mare thrust, has formed on the east side of the Waikukupa River valley. The average rate of slip on the two thrusts is estimated at 22–30 mm/year. Analysis of the fault structure in terms of critical wedge theory is consistent with imbrication resulting from a reduction in wedge taper below the critical value due to rapid river erosion. The internal structure of the Waikukupa thrust sheet consists of reverse faults and angular folds forming duplex-like systems, associated with minor strike-slip faults. Within the limits of uncertainty, the structures are consistent with strain accumulating during internal transpressional shear of the thrust sheet while the taper of the latter was subcritical prior to the transfer of fault displacement to the Hare Mare imbricate. The thrust complex forms part of a serrated range front fault system consisting of oblique thrust sections linked by strike-slip faults. We introduce the term ‘serial partitioning’ for this type of partitioned transpressional fault system. Its development is linked to the erosional processes at the range front. An alternative system consisting of parallel thrust and strike-slip faults we here term ‘parallel partitioning’. While angle of obliquity is an important parameter in determining which partitioning model develops, we suggest that erosion rate is also an influential factor.

Central Otago in New Zealand is an area of active continental shortening in which a peneplain surface cut into schist has been deformed by folds, which are developed above buried reverse faults. We use the drainage patterns in this region to demonstrate various processes in fold (and fault) growth and interaction that would be difficult to identify by other means. In particular we show: (1) how simple asymmetric folds can develop into box folds; (2) how apparently continuous ridges were formed by the coalescing of quite separate propagating fold (and fault) segments; (3) evidence for the relative ages (or relative uplift rates) of adjacent structures; and (4) evidence for the propagation direction of folds (or faults) as they grow. The few quantitative estimates we obtain for fault propagation rates suggest an increase in length of 10–50 m per earthquake on faults about 20 km long. These estimates are very uncertain, but are similar in magnitude to an estimate made in Nevada for a normal fault of similar size and are also similar to predicted estimates from theoretical growth models. They raise the question of whether fault growth, earthquake recurrence rates and climate change can interact to produce semi-regular discrete features in an active landscape.

The prehnite-pumpellyite to greenschist facies rocks of the classic low-grade Otago schist terrane are subdivided into a number of textural zones based on the development of slaty cleavage and the appearance of segregation lamination in metagreywackes. In this study, conglomerates from fifteen localities have been studied in order to investigate the relationship between ductile strain and the sequence of textural zones. Strain measurements on lithic pebbles show a clear correlation between strain and textural zone, ranging from around 40% shortening in TZ IIA with the development of slaty cleavage to more than 70% in TZ IIIA corresponding to the appearence of segregation lamination. The much lower and more prolate strains of the quartzose pebbles compared to the corresponding lithic clasts may be explained by differential strain partitioning between clast and matrix. Microstructural evidence, including well-developed strain shadows and solution seams, indicates that solution-transfer was the dominant deformation mechanism. The development of quartz segregation laminae in TZ III is due to three related processes: the development of mica-rich solution seams demarcating quartzo-feldspathic microlithons; the development of amalgamated and recrystallised strain shadow overgrowths on clastic grains; and the formation, rotation and disruption of early formed veins. The large increase in strain from TZ II to TZ III is responsible both for increased segregation and for the rotation and flattening of segregation features into the foliation, thus producing a segregation lamination. Large strains developed by solution-transfer during the low-grade metamorphism of greywackes will lead inevitably to segregated schists.

The Alpine Fault of New Zealand forms the western boundary of a zone of distributed deformation formed by the oblique convergence of continental crust belonging to the Pacific and Australian plates. Structural and geodetic data from the Alpine Fault show that a large proportion of the total plate displacement is accommodated by rapid oblique slip on the fault. The remaining displacement is distributed over a 200 km wide zone to the east. The collision may be modelled as a two-sided deforming orogen, with the partitioning of deformation being controlled by erosional differences between the narrow high-strain inboard and broad low-strain outboard sides. In ancient collision zones, little evidence may remain of the nature and amount of displacement on the inboard side. Partitioning of deformation among pre-existing structures complicates interpretation of the outboard zone. Radiometric ages may post-date collision by several tens of millions of years and indicate slow isostatic uplift and unroofing. Collision ages, if preserved, may be recognized by high uplift rates calculated from muscovite-biotite pairs.

Tectonic processes and/or climate-related fluvial activity commonly cause river drainage reorientation that can affect topographic development and sedimentary depocentres on a regional scale. Drainage reorientation results from development of a physical barrier within a river valley, erosional river capture, or a combination of these. Physical barriers also separate indigenous freshwater fish, resulting in isolated populations that then evolve independently. Divergent molecular evolution of mitochondrial DNA in the separated populations results in measurable differences in DNA sequences after about 5-10 ka. We are calibrating the resultant “molecular clock” using suitable geological barrierforming events associated with glacial and tectonic development of topography in the South Island of New Zealand. Several Holocene and late Quaternary glacial outwash and tectonic barriers have been dated by regional fluvial terrace correlation supplemented by carbon dating [1]. A middle Quaternary tectonic barrier has been dated by extrapolation of late Quaternary uplift rate estimates [2].The age of an early Quaternary barrier has been estimated from Be and Al dating of surface materials [3]. The resultant calibration line implies DNA divergence rates of about 10%/Ma, which is substantially faster than longer-term DNA divergence rates commonly used by biologists (typically about 2%/Ma). Further work is needed to determine if the divergence rate is linear through the Quaternary, but the method shows promise as a potential dating tool for Quaternary topographic evolution events. This method is useful in active tectonic settings where the rate of geomorphic evolution is similar to the rate of biological evolution. The method dates the last time that a “wet connection” existed between drainages that allowed genetic interchange between now-separated populations.

A 27 year old white male presented in June 1991 with a two year history of perineal pain and a mass at the crus of the corpus cavernosum which was drained percutaneously each three months. At operation a mass was found in the right antero-iaterai pararectal space which did no involve the bladder, rectum, anus or the pelvic bones. The patient received no adjuvant therapy and is alive and well 8 months after surgery. A cylindrical tumour 180 × 60 × 35 mm with attached skin and skeletal muscle was received. The cut surface of the tumour showed a partly solid and cystic lesion with pale yellow-grey solid and papillary areas separated by thin-walled cystic spaces which measured up to 20 mm in diameter. The cyst walls had a yellow-brown colour and were filled by semi-solid and liquid brown material. Histological sections showed partly solid partly cystic tumour. Within the solid component there was a prominent cribriform and spindle cell pattern with relatively uniform columnar epithelial cells with open vesicular nuclei and small prominent nucleoli lining acinar spaces filled with Alcian blue and PAS positive material. Between the acini the tumour had a solid and trabecular pattern with these trabeculae separated by relatively amorphous eosinophilic connective tissue which was PAS positive and diastase sensitive and congo red negative. Mitotic figures were rare. There was a prominent microvascular pattern through the tumour and extensive areas of intratumoral haemorrhage and necrosis. The tumour cells stained for broad spectrum cytokeratins and Cam 5.2. The spindle cell component of the lesion stained patchily with NSE and vimentin but is negative for S100 and CEA. Electron microscopy was performed and showed epithelial cells which were columnar and perpendicular to the lumen with tight cell junctions, desmosomes and microvillous cytoplasmic processes near the base of the cells. In areas there was a well defined basal lamina. Within the cells there were scattered glycogen granules, few mitochondria and numerous lysosomes. The features are consistent with those described by Demopoulos and others as Wollfian duct carcinoma.

A 200 m thick mudstone unit in the Carboniferous of the Cantabrian Mountains, northern Spain, exhibits an increase in intensity of the slaty cleavage from top to bottom which appears to be correlated with a decrease in the mean grain size, average bed thickness and quartz: mica ratio. Anastomosing cleavage domains, formed by pressure solution and by kinking and rotation of the detrital micas, become closer spaced, wider and more continuous towards the finer-grained base of the unit. Growth of strongly oriented new micas within the cleavage domains also appears to be correlated with the intensity of the domain development and hence with the initial lithology. Clay minerals have been completely replaced throughout the mudstone by muscovite, paragonite and pyrophyllite during low-grade metamorphism. The growth of an oriented mica fabric, however, is restricted to samples with well-developed cleavage domains.

Continental transform boundaries in detail consist of zones of fault-bounded blocks adjacent to the principal active transform fault(s). Relative movement of these blocks in response to plate boundary motions gives rise to differential vertical displacements of the earth's crust and hence exercises a degree of control on the tectonic evolution of sedimentary basins adjacent to the transform boundary. The Cenozoic sedimentary basins of southwest New Zealand have several features in common that may be attributed directly to the movement on the adjacent plate boundary. However, their location, detailed sedimentary evolution and tectonic development may best be understood in the context of the relative displacements of a number of fault-bounded blocks, in response to the plate motions. In particular, movements of the Fiordland block, bounded by the Alpine and Moonlight fault zones, exercised a large measure of influence on the development of the basins. The tectonic model presented is consistent with plate boundary motions inferred from marine magnetic anomalies while at the same time providing an explanation for many of the more detailed features of the basins.

Sea-floor spreading data from the Southwest Pacific have recently been used to predict the Cainozoic geological history along the Indo-Australian/Pacific plate boundary. Geologic and sedimentologic data pertaining to this plate boundary where it crosses southern New Zealand, as the Alpine Fault, are summarised and discussed. It is concluded that there is a close accord between the plate-tectonic predictions and South Island Cainozoic geological history. In particular, (1) no Cainozoic plate boundary traversed the New Zealand region prior to 38 m.y. B.P. (late Eocene); (2) transcurrent movement on the Alpine Fault took place largely between ca. 30 m.y. B.P. (middle Oligocene) and ca. 10 m.y. B.P. (late Miocene); and (3) the period 10 m.y. B.P. to present corresponds to a phase of oblique compression, continental collision, and mountain building along the Alpine Fault sector of the plate boundary. There is a close correlation between the sites and histories of Cainozoic sedimentation and this tectonic timetable.

Carter, R.M. and Norris, R.J., 1977. Redeposited conglomerates in a Miocene flysch sequence at Blackmount, western Southland, New Zealand, Sediment. Geol., 18: 289319. The Middle Miocene Monowai Formation represents a gravel delta that prograded south into a flysch basin complex developed along the Moonlight Tectonic Zone, southern New Zealand. The delta-slope environment was characterized by a conglomeratic sequence up to 500 m thick. Most of the gravel was moved downslope by mass-transport processes. A complete spectrum exists from synsedimentary slide sheets (up to 10 m thick and 100 m long) that retain pre-sliding sedimentary structures, to more mature mass-transported sediment types in which all original structures have been destroyed. The most distal deposits include ungraded homogeneous pebble conglomerates up to 3 m thick. Some of the more mature redeposited conglomerate--sand--mud units (X--Y--Z sequences) are between 2 and 10 m thick; they comprise a basal X-division of bouldery conglomerate, a middle Y-division of pebbly mudstone or pebbly sandstone, and an upper Z-division of hydroplastically folded mudstone. Though X--Y--Z sequences may have been deposited from very proximal turbidity or fluxoturbidity currents, inertia-flow emplacement seems more likely. An inertia-flow mode of emplacement also seems most probable for the other redeposited sediment types described from the Monowai Formation.

Deformed pillow structures are described in greenstones from the Tauern Window, Austria, confirming the presence of submarine basalts within this part of the Pennine Zone. The pillows have been subjected to a large constrictional strain, so that their shapes are still easily recognisable in sections perpendicular to the stretching direction. The pillow rims are highly enriched in epidote, whereas the cores are of more typical spilitic composition. The nature of the alteration is unlike that described from pillow basalts altered on the sea floor, and is therefore assigned to alteration during regional metamorphism. Recalculation of the analyses of rim and core suggests that additional calcium in the rim was derived by spilitisation of the core rather than by massive calcium metasomatism from outside. Intense flattening of the differentiated pillows, as is usual over most of the area studied, produced an epidote-banded greenstone in which recognisable pillow structures are largely absent.