Instead of the usual technical meeting, the NSW Branch of the ASEG will hold a student night presentations by Honours students at 5:30 pm for 6:00 pm on Wednesday 17^th October 2007 at The Rugby Club-Level 3,

(near Pitt and Alfred St), Sydney CBD. Cara Danis of Macquarie University and Joshua Knight of University of Sydney will be presenting on their studies.

Alpha GeoScience is generously sponsoring an open bar on the evening.

Also please be aware that the rest technical meetings of this year will be on Thursday 15^th November and Wednesday 12^th December. Suggestions for (or interest in presenting at) these two meetings are welcomed. Please contact Mark Lackie.

We also have a  NEW ASEG AWARD notice 

NSW members will be pleased to know that the plan to use some of our funds in a beneficial way has materialised. The Federal executive of ASEG has agreed to our request to have a new award for members under the age of 36 who have made an outstanding contribution to the profession by way of papers published. It is to be called the “ASEG Early Achievement Award”. The value is $2,000 cash and the recipient is to present a paper at the conference. The Executive have backed the plan by contributing 50% to the value and requesting that other states also contribute.NSW has committed $1,000 to each of the first 5 awards. If you wish to know more, please contact

Roger Henderson.”

Cara Danis of Macquarie University  will be presenting on: 

The Wongwibinda Complex a tilted block?

The Wongwibinda Complex contains a rare exposure of deep New England Fold Belt (NEFB) crust, which has undergone low-pressure high-temperature amphibolite facies metamorphism in a virtually un-metamorphosed region. The aim of defining the subsurface structure of the Complex is to explore the controls of high-T low-P metamorphism, exhumation and tilting in the Complex and develop a geological model that accounts for the tectonic history of the region. With geothermobarometry to determine peak and retrograde metamorphic P-T conditions and a 20 km detailed gravity survey the tilted block model can be tested. Gravity modelling provided a way to determine the 2D subsurface structure of the Wongwibinda Complex and constrain key tectonic features, such as the Wongwibinda Fault, which is shown to be a steep fault extending to at least 2km. A tilted block model could explain the thermal gradient in the Wongwibinda Complex but gravity modelling of the subsurface suggests that a geological model is possible where perhaps tilting is not required. 

Joshua Knight of University of Sydney  will be presenting on: 

Modelling the Contemporary and Palaeo-Stress of the Indo-Australian Plate

Knowledge of the contemporary stress field is important for mining safety and for understanding the origin of intra-plate earthquakes.  The stress field evolution over time is also important for hydrocarbon exploration, and testing theoretical models for geodynamic evolution.

We use a 2 dimensional finite element model in ABAQUS with heterogeneous elastic strengths in lithospheric regions, to model the stress field orientation and relative magnitudes across the Indo-Australian Plate, at a nominal resolution of ~0.2° in latitude and longitude.  The model is coupled with the parallel optimisation package Nimrod/O which allows the efficient exploration of a large non-linear parameter space.  The misfit of the contemporary modelled stress orientations is minimized by comparing against more than 1800 World Stress Map measurements, and adjusting model plate boundary forces and relative strengths of lithospheric regions such as sedimentary basins and mountain belts. Our optimised model has a residual misfit of around 30°.  Our model efficiently assimilates geological observations and shows that large amplitude intraplate stresses are concentrated in mid-latitude India and central Indian Ocean where small earthquakes are common, thereby providing a framework for managing seismic hazards by linking plate scale to local scale phenomenon.  We also show that large rotations of the stress field occur between cratons such as the Yilgarn and adjacent sedimentary basins.

Building on the results from contemporary optimisation, we also model the palaeo-stress field evolution by focusing on two critical times during the India-Eurasia collision in the early Oligocene, which occurs after the onset of India-Asia collision; and the early Miocene, which precedes the onset of the Papua New Guinea collision.  These times had significantly different boundary forces, and we show that the stress field direction and amplitudes have changed significantly during this time period, thereby providing a new tectonic framework for natural resource exploration.