GEOSCIENCE SOCIETY OF NEW ZEALAND ANNUAL CONFERENCE 2017 DYNAMIC NEW ZEALAND, DYNAMIC EARTH Abstract Volume University of Auckland November 28- December 1 ABSTRACT VOLUME Chair Organizing Committee Michael Rowe Extended Organising Committee Julie Rowland, Paul Augustinus, Martin Brook, Jon Tunnicliffe, Jennifer Eccles, Kathy Campbell, Joel Baker Administration Stephanie Szmurlo Fieldtrip Leaders Bruce Hayward, David Lowe, Julie Rowland Abstracts are organised in alphabetical order by family name of first author The bibliographic reference for abstracts is: Author, A.N. (2017). Title of Abstract. In: Baker, J. and Rowe, M. (eds). Abstracts, Geosciences 2017, Auckland, Geoscience Society of New Zealand Miscellaneous Publication 147A. p. x. Co-Published by: University of Auckland, School of Environment & The Geoscience Society of New Zealand ISBN 978-0-9922634-4-7 ISSN (print) 2230-4487 ISSN (online) 2230-4495 Platinum Sponsor Gold Sponsor Silver Sponsor and poster sessions Bronze Sponsor Ice Breaker and Student Award under in situ conditions, with simulations that RECONCILING EXPERIMENTAL AND STATIC- account for micrometre-scale variations in DYNAMIC NUMERICAL ESTIMATIONS OF elastic properties of constituent minerals with SEISMIC ANISOTROPY IN ALPINE FAULT the MTEX toolbox and finite-element wave MYLONITES propagation on EBSD images. We observe that the sorts of variations in the distribution of L. Adam1, M. Frehner2, K. Sauer3, V. Toy3, S. micas and quartz+feldspar within any one of Guerin-Marthe4 & C. Boulton5 our real core samples can change the elastic 1 University of Auckland, New Zealand wave anisotropy by 10%. In addition, at 60 2 ETH Zurich, Switzerland MPa confining pressure, experimental elastic 3 University of Otago, New Zealand anisotropy is greater than modelled 4 Durham University, Earth Sciences, United anisotropy, which could indicate that open Kingdom microfractures dramatically influence seismic 5 Victoria University of Wellington, New wave anisotropy in the top 3 to 4 km of the Zealand crust, or be related to the different resolutions [email protected] of the two methods. Quartzo-feldspathic mylonites and schists are the main contributors to seismic wave THE PHYSICAL PROPERTIES OF ALPINE FAULT anisotropy in the vicinity of the Alpine Fault CATACLASITES THAT DRIVE ITS ELASTIC (New Zealand). We must determine how the WAVE VELOCITIES physical properties of rocks like these influence elastic wave anisotropy if we want to L. Adam 1, S. Guerin-Marthe 2, S. J. Kanakiya unravel both the reasons for heterogeneous 1, C. Boulton 3, V. Toy 4 & D. Faulkner 5 seismic wave propagation, and interpret 1 University of Auckland, New Zealand deformation processes in fault zones. To study 2 Durham University, Earth Sciences, United such controls on velocity anisotropy we can: 1) Kingdom experimentally measure elastic wave 3 Victoria University of Wellington, New anisotropy on cores at in-situ conditions or 2) Zealand estimate wave velocities by static (effective 4 University of Otago, New Zealand medium averaging) or dynamic (finite 5 University of Liverpool, United Kingdom element) modelling based on EBSD data or [email protected] photomicrographs. Here we compare all three approaches in study of schist and mylonite Studying the Alpine fault, which is late in its samples from the Alpine Fault. cycle of stress accumulation, is a unique opportunity to understand the subsurface Volumetric proportions of intrinsically conditions ahead of a large earthquake. It is anisotropic micas in cleavage domains and the physical properties of the rocks in the comparatively isotropic quartz+feldspar in damaged zone around the fault that will microlithons commonly vary significantly control the mechanisms of rupture and within one sample. Our analysis examines the propagation. Here we present a effects of these phases and their arrangement, comprehensive study of the physical and further addresses how heterogeneity properties of Alpine Fault cataclasites and influences elastic wave anisotropy. We their relation to elastic wave speed and compare P-wave seismic anisotropy estimates moduli. We study 12 cataclasite samples from based on millimetres-scale ultrasonic waves core extracted from the DFDP-1A and -1B 1 wells from the first Alpine fault DFDP more closely match those likely to be campaign. encountered in future career opportunities. However, fieldtrips are also a stressful Sonic log P-wave velocities in the cataclasite experience, requiring students to work long sections in DFDP wells vary between 2000 and hours and to produce an integrated finished 6000 m/s and there is little quantitative product (e.g., a map) in a relatively short understanding on the nature of this variability. period of time. We have performed high (up to 100 MPa) and low (pressure at the core depth, 2-4 MPa) At the University of Canterbury, we identified pressure P- and S-wave ultrasonic velocity that students felt underprepared for fieldwork measurements on the water-saturated and that the current laboratory-based field cataclasites. Our laboratory velocities match training was not an adequate lead in for the well data at the pressures representative independent field mapping trips. Therefore, of the core depths, but as expected, velocities we developed a one-day fieldtrip “boot camp” at higher pressures do not agree with the log. to replace laboratory teaching. In the boot To understand which micro-scale physical camp, we introduced the students to basic properties affect the P- and S-wave velocities, field concepts in an authentic field setting, we have performed computerized which helped to improve their self-efficacy tomography scanning and analysis, semi- before attempting their first overnight quantitative XRD, XRF, porosity and grain independent field mapping course. density from pycnometry and fracture estimation from rock physics modelling. Here, we present our initial findings on Preliminary data indicate that fractures and student self-efficacy as a result of our fieldtrip porosity are not the principal controls on wave changes. We also present ongoing curriculum speed variability. Moreover, we will discuss development into the benefits of repeated the challenges of studying the physical field skills exercises as a preparation to further properties in cataclasite rocks in the context of learning in later degree fieldtrips which atmospheric vs. confining pressures. require more independence and critical thinking from undergraduate students. We then discuss implications of our data for the TRADITIONAL AND VIRTUAL FIELDTRIPS AS development of future real and virtual PREPARTION FOR FURTHER GEOSCIENCE fieldtrips. LEARNING P.A. Ashwell1, A. Jolley1, J. Dohaney2 & B.M. Kennedy1 1 Dept. of Geological Sciences, University of Canterbury, Private Bag 4800, Christchurch 2 Swinburne University of Technology, PO Box 218, Hawthorn, Victoria, Australia [email protected] Fieldtrips are often seen as crucial learning experiences for undergraduate students. In the field, students apply knowledge and skills from prior courses to real world scenarios that 2 INTEGRATED INTERPRETATION OF which broadly coincide with the surface AEROMAGNETIC AND GEOLOGICAL DATA TO geology, including: a) > 3 km deep andesite IMAGE THE SUBSURFACE GEOLOGICAL intrusives, b) 0.5 – 2 km deep andesite/dacite PATTERNS (DISCONTINUITIES) WITHIN THE intrusives and extrusives, and c) < 1 km deep COROMANDEL VOLCANIC ZONE (CVZ) andesite/dacite and rhyolite extrusives. Similarly, the data show prominent NW-SE, E.A. Bahiru1, J.V. Rowland1 & J.D. Eccles1 and NE-SW oriented, strong and linear to 1School of Environment, the University of semi-linear structural discontinuities and Auckland, Private Bag 92109, New Zealand anomaly boundaries, which we interpret as [email protected] deep-seated structural patterns that broadly reflect the control of regional basement The paucity of bed rock exposures due to structures. dense vegetation cover, and a lack of uniform coverage of high-resolution geophysical data in the Coromandel Volcanic Zone (CVZ) make SEDIMENTARY PROCESSES OF THE COOK imaging of the subsurface geologic patterns STRAIT CANYON SYSTEM difficult. We compile companies’ deposit scale high-resolution aeromagnetic surveys and S. Banks1, L. Strachan1, I. Pecher1, P. Barnes2, integrate with the surface geological data as A. Orpin2 constraints to illustrate the subsurface 1School of Environment, University of geologic features and their relationship with Auckland, Private Bag 92019, Auckland, New surface patterns. Despite the inherent Zealand ambiguity associated with aeromagnetic 2National Institute of Water and Atmospheric interpretation, the data provide an Research, 301 Evans Bay Parade, Wellington opportunity to recognise the occurrence of [email protected] magnetic source bodies at different subsurface depths by isolating the long and Submarine canyon systems provide a major short wavelength anomaly components. In conduit for transport of marine and terrestrial this regard, we particularly use the multiscale sediment from shelf to deep-ocean. Sediment edge detection (worming) technique on the flow processes and triggering mechanisms gradient enhanced aeromagnetic grid to that drive flow processes vary greatly from indicate locations where there exist maximum canyon to canyon. Variation of flow processes contrasts in the susceptibility of the is affected mainly by the canyon subsurface geology. The technique images the geomorphology and sediment type. This subsurface contrast