Breaking the trend: why do New Zealand turbidity currents run so far?

Evolution of a colossal turbidite channel at a convergent plate margin

Supervisors: Lorna J. Strachan¹, Helen Bostock², Phil Barnes², Brian Romans³, and Henry Pantin^{4 1}Geology, School of Environment, University of Auckland, Auckland 1142, New Zealand (l.strachan@auckland.ac.nz). ²National Institute of Water & Atmospheric Research (NIWA), Private Bag 14901, Wellington, New Zealand. ³Virginia Polytechnic Institute and State University, Department of Geosciences, 4044 Derring Hall, Blacksburg, VA, USA. ⁴School of Earth and Environment, University of Leeds, Leeds, LS2 9JT, UK.     Continent-derived sand, mud, and gravel is transported to the deepest ocean basins by deep-sea river-like conduits – known as turbidite channels. The Hikurangi Channel east of New Zealand is an immense example; its length measuring some 1700 km is more than four times longer than any other located at an active continental margin. Since the discovery of turbidite channels as geomorphic features of the ocean floor, there has been rigorous debate as to what processes control their length, width, depth, and gradient.  Recent research¹ shows that Earth’s longest deep-water channels correspond with mature, passive continental margins and voluminous mud-rich sediment supplies. Interestingly, these findings are inconsistent with preliminary observations of the Hikurangi Channel that today transports relatively small sediment loads of sand and gravel² across a narrow, active continental margin. Today the Hikurangi Channel has its headwaters in the Kaikoura Canyon located off the South Island of New Zealand, where in shallow water sediment sporadically collapses into the deep abyss, spawning turbidity currents.  Hikurangi Channel turbidity currents have scoured a 500 m deep and 1-10 km wide channel that travels north and east, past the North Island of New Zealand, across the Hikurangi oceanic plateau, and ultimately plunging to water depths in excess of 5600m. Using integrated sediment core, seismic reflection, multibeam, and sidescan sonar data from NIWAs world-class repository, this project will focus on Hikurangi Channel evolution and address the following questions:

• How old is the channel and what processes led to its formation?
• What are the range, frequencyand size of flows within the channel?
• How have variable sediment flux (associated with uplift of the Southern Alps and glacio-eustasy) and changing seafloor relief (linked to Hikurangi subduction) influenced the evolution of the channel?

  The project will involve a range of sedimentological, geomorphological and geophysical techniques used to decipher the short-term modern flow processes (e.g. sediment core analysis, granulometric and provenance analyses, geomorphological analysis, GIS manipulation) and long-term geologic controls of channel evolution (e.g. seismic stratigraphy, sediment dating, depositional element mapping).  The student will have access to analytical facilities at Auckland University, NIWA (Wellington) and Virginia Polytechnic Institute and State University.   The student will join the Process Sedimentology research Group at Auckland (Dr Strachan) and the Ocean Geology NIWA group based in Wellington.  They will thus join a larger team of researchers investigating a range of marine problems. The studentship will be based in Auckland but it is anticipated that up to 1 year will be spent at NIWA (Wellington), where the student may have the opportunity to participate on a research cruise using NIWAs deepwater research vessel the RV Tangaroa.   Training will be provided in state-of-the-art techniques including advanced process sedimentology, seismic stratigraphy, and seafloor geomorphological analyses.  This combination of advanced training will provide a broad portfolio of skills which could facilitate career development in the academic, environmental or industrial sectors.

Eligibility

We seek a motivated and able graduate committed to becoming an independent researcher.  The studentship is open toNew Zealand, Australian and international candidates.  We seek a graduate with a minimum upper second class BSc (Hons) degree (or equivalent) in Geological Sciences, Geology and Earth Sciences.  Due to the multidisciplinary nature of this project candidates must also demonstrate a strong background or interest in sedimentology, seafloor geomorphology, or seismic stratigraphy research.

General information

The “Beate Schuler Doctoral Scholarship in Marine Science” at the University of Auckland is available to support this project and consists of a 3-year stipend of NZ $25,000 per annum (tax free) and university fees.  Applications for the Scholarship must be made on the application form available from the Scholarships Office website: (http://www.auckland.ac.nz/uoa/cs-search-for-scholarships-and-awards?form=details&detailCode=500634).  Please specify THIS project when applying. Further details are available from Dr Lorna Strachan, e-mail: l.strachan@auckland.ac.nz. Closing date: 1^st November 2012

References

1. Covault, J.A., Shelef, E., Traer, M., Hubbard, S.M., Romans, B.W., and Fildani, A., 2012, Deep-water channel run-out length: insights from seafloor geomorphology: Journal of Sedimentary Research v. 82, p. 25-40. 2. Lewis, K.B., 1994, The 1500-km-long Hikurangi Channel: trench-axis channel that escapes its trench, crosses a plateau, and feeds a fan drift: Geo-Marine Letters, v. 14, p. 19-28.

The AAPG Student Chapter at the University of Adelaide would like to extend an invitation to our annual AAPG Student-Industry Field Trip, to be held on November 16-18, 2012: “Depositional environments of the Hawkesbury Sandstone and associated Permo-Triassic strata in the Sydney Basin” This year’s field trip, investigating the depositional environments and sequence stratigraphic framework of the Permo-Triassic strata of the Sydney Basin, will be led by Professor Peter McCabe (Queensland University of Technology). The primary focus will be the Triassic Hawkesbury Sandstone, which is spectacularly exposed in coastal outcrops south of Sydney. Classically interpreted as the deposit of a large sandy braided river, the Hawkesbury has recently been reinterpreted as deposited in a tide-dominated setting. Participants will be encouraged to examine the outcrops to formulate their own interpretations. Underlying Permo-Triassic strata will be examined and the evolution of the Sydney Basin discussed. This fieldtrip provides an excellent opportunity for those wishing to learn more about sedimentary structures, sequence stratigraphic concepts, and sandstone geometries on a reservoir scale. A major objective of the field trip is to provide the petroleum geology students at Adelaide University with an opportunity to network with industry professionals from across Australia while learning new concepts in the field. For further information and payment details, refer to this attached document. Keep in mind that industry places are limited; please contact us ASAP (details in attachment) if you are interested in attending, and feel free to circulate to any interested colleagues.

An IODP workshop to discuss drilling projects in the SW Pacific Ocean will be held in Sydney, Australia on the 9^th-11^th October 2012. For more information, please click on the following link

PhD Opportunity in sedimentology and sedimentary provenance studies of intraplate orogenic-related sedimentation.   We seek a highly motivated student with strong field-based research interests in sedimentology and detrital mineral geochronology to be part of a collaborative, multi-disciplinary research program investigating the Carbonifeous sedimentary record across eastern Australia.   Sedimentary rocks are a key recorder of tectonic events. This fundamental Australia-based research will take new approaches to establish a finely tuned record of orogenic processes deforming the continental interior and how sediment loading from this mountain building event may have affected extension and magmatism at the continental margin. This project will examine the Late Devonian to Early Carboniferous (~380-320 Ma) continental sedimentary record across central and eastern Australia as this time slice records widespread rift basin development in northeastern Australia, intraplate orogenic events in central Australia (Alice Springs Orogeny), the progradation of a major sheet of cratonic-derived quartz-rich sand spreading outwards across Australia, and the initiation of Late Paleozoic glaciation. Mutliple dating techniques applied to the detrital minerals will be a key component of this project, revealing both the igneous and high-grade metamorphic history (from U/Pb zircon and rutile ages), and the recent tectonic and exhumation history (using lower temperature thermochronometers) of the source region. These new data will provide new insights into the relationship and timing of sedimentation and deformation.   Queensland University of Technology has one of Australia's fastest growing research profiles, and aims to become research-intensive in selected areas of strength and priority. QUT's focus is to undertake high-impact research that is both of the highest academic quality and also aimed at making a real and practical difference to the world around us.   Application process:   A MSc degree in Earth Sciences (or equivalent) and excellent communication skills in English are a prerequisite. We seek a student with previous experience in field mapping, stratigraphy/sedimentology, sedimentary petrology and/or geochronology. The annual scholarship round is now open with applications closing on October 12, 2012.   Information on the PhD scholarships available and how to apply can be found at: http://www.qut.edu.au/research/scholarships-and-funding/research-scholarships   Academic and Research Experience Required: a)         a relevant first class or second class division A honours degree or equivalent, or an appropriate research masters or professional doctorate, from a recognised institution OR b)         a coursework Masters or  professional doctorates with a.         a grade point average of at least 5.0 on a 7 point scale and b.         an significant level of research experience such as publications and research work   English: A demonstrated sufficient command of English to complete the proposed course of study.   For further information, please contact:   Dr Scott Bryan (scott.bryan@qut.edu.au) Earth, Environmental and Biological Sciences, Faculty of Science and Engineering Queensland University of Technology GPO Box 2434 Brisbane Queensland 4001 Australia

We wanted to update you about a number of key events that you may considering attending in 2012 and 2013, together with abstract deadlines:

• Geoscience 2012, 25-28th November, 2012. Annual meeting of the Geoscience Society NZ.  University of Waikato.  Abstract and early-bird deadline: Friday 14 September.

• Subsea Australasia Conference, 20-22nd February, 2013,  Perth, Western Australia (Call for papers).

• AAPG Annual Convention, 19-22nd May, 2013, Pittsburgh. Abstract deadline: Thursday 11 October.