Friday, 11 November 2011

Coal seam gas gets a seismic thump!

Ok, time for me for foray into an area that is politically sensitive. But I hopefully do so factually.  I'm starting now because of recent developments by the Lismore City Council to first approve a Review of Environmental Factors (Which is strange since the Mineral Resources Division of the NSW Government approves these (or was it approval to use road reserves? I can't seem to figure out what authority the council has from the news reports)) and then to rescind this approval once they found that the work being undertaken could be used to target the area for further coal seam gas exploration (well... that is how I read it). Here are two newspaper reports that discuss the matter: Northern Star and Northern Rivers Echo.

So, I guess the centre of the matter is 'what is seismic exploration anyway?' Seismic exploration comes under the category of geophysics and in this case refers to the use of sound waves to try and understand what is below the ground. It is a non invasive method with the major environmental impacts believed to be limited to noise pollution and a small area of squashed grass. Practically one of the common processes used (and I understand this may have been the method outlined in the REF) is a truck with a pad under which will drop and hit 'thump' the ground. Sensors in the truck (or an accompanying vehicle) then receive data back from the ground as the vibrations made are reflected off layers of rock under the ground. The truck will then drive off a hundred or so metres further along and then do it again and so on.

The Department of Mineral Resources have previously conducted some of this work in the area since the 1970s. But I understand that Metgasco are currently undertaking more detailed work which may provide them with information that can lead to (or rule out) possible places to target exploration drilling. The Roads and Traffic Authority (RTA) frequently use this technique when planning routes for roads, the last time I heard this was between Byron Bay and Grafton about 6 months ago.

The decision by Lismore City Council is therefore one I find a little hard to understand unless it is simply a matter of the Councillors not understanding the technique itself or just deferring to the current political environment. Personally, I'd certainly love to get some more geophysical information on the Clarence Moreton Basin (for the sake of scientific knowledge itself) since I've recently had some discussions various people that prove that we know very little about faults, stratigraphy, intrusions, groundwater, deformation, metamorphic events, etc that have occurred in the basin since the rocks were laid down. Seismic exploration would go along way to answering some of these questions. But I guess if the politicians and general public don't want the information to be used specifically in coal seam gas exploration then it is important that we do not learn about these features in our region. That might be a price many in our region are prepared to undertake.


  1. Hi Rod
    Yes people are getting hysterical about CSG! You make some good points here.
    Some geological aspects I am interested in at present are; Coffee Rock formations that you find at many North Coast beaches, how old is it? How does it form? Do you also know anything about Glenugie Peak, a small volcanic intrusion( is this the correct terminology?) about 10kms Sth East of Grafton? When did it form, was it associated with the Ebor Volcano?
    Thanks Mark

  2. Hi Mark,
    Lots of questions and as usual only some half answers from me! Coffee rock is quite common. It is a partially indurated (becoming a rock), it is often full of iron sulphides and is generally Pleistocene in age. i.e. quite recent.

    With regard to Glenugie Peak/ Mount Elaine? area... well... hmmm... maybe. Though I think it is likely to be from a more local volcanic source. I dont know whether it is an intrusion or lava flow as I've only seen it from a distance. Just north of Grafton is the remnant of another hot spot volcano called the Belmore Volcanic Province (about midway in age between Tweed and Ebor) that I will do a post on later which shows there many volcanoes that used to exist through the area. Also, there are many slightly older basalts in the area of unknown origin that just seem to pop up from time to time!

    Hope this helps in the mean time. I'm wondering what I've got myself into by so many people asking so many questions. It just goes to show how little us folks know about this area!

    Cheers, Rod.

  3. Thanks for the info Rod. Yep when you start a blog people will start asking questions.
    Did you know that Glenugie Peak was 'mined' for its basalt cobbles for ballast when they built the North Coast Rail Line. Glad they didn't take it all!

  4. Thanks Mark. I forgot to mention that Coffee Rock has a dark colour mainly due to a high organic derived component. And no I had no idea it was used for building the North Coast Line... interestingly you've touched on another interest of mine which is railways.

  5. Hi Mark and Rob,
    Coffee rock is interesting stuff! I have seen some work done on Stradbroke Island where ages of between 90-110,000 Bp have been found (Notes on the origin of Stradbroke Island. W.T. Ward). It seems a very plausible theory that involves ice age marine regression and subsequent mobilisation of sand and mud on the continental shelf forming a gigantic strand plain (An example of this can be seen in western Namibia). My observations at Belongil Beach (Byron Bay) show that coffee rock is terrestrial sediment that is generally finely bedded with occasional fossil and granule conglomerate layers or partings. Deposition seems to be a product of dominantly Aeolian action with minor lacustrine events. The high sulphide content has been described as a product of REDOX reactions that is similar to that occurs in deltaic soils, but instead of soil it is sand and may be the result of a fluctuating water table.