Thursday, 26 July 2012

Why you won't find CSG here now

As you might have noticed there has been an occasional blog post that I’ve done dealing with coal seam gas matters in a cursory manner. I’ve been asked again and again by many people to explain aspects of the industry and the environmental issues associated with it. I’ve worked in coal exploration and in an environmental capacity before and I know a moderate amount about gas extraction too but I’m afraid I don’t have all the answers. Caution is needed especially given the highly political nature of the subject now. Therefore, I don’t really want to weigh into the subject, but I’ll have a very quick comment or two just to really outline the big picture. In the last week I cautiously commented in the Northern Star online twice as the avatar ‘GeologyRod’ just to correct a couple of mistakes people have made. I’ve also written one letter to the editor cautioning about how to interpret water chemistry. Given the heated debate, I’m not sure I will do so again!

From what I understand of the coal seam gas industry and the geology directly applicable to the area I am not as concerned about the industry doing damage to groundwater sources or surface water as some. From my contaminated land experience, I do however; see two potentially serious environmental problems. These are failure of well casings causing local cross-connection of poor and good quality water (and gas) and the disposal of poor quality production water (salinity is the biggest problem, as the chemicals potentially used can easily be treated but salt is hard to get rid of).

Considering a risk assessment approach (using the possible outcome and likelihood of that outcome) provides many scenarios with only the two mentioned above displaying an elevated level of risk (in my very hastily developed opinion). The nature of the geology of the southern Clarence-Moreton Basin is such that regional scale ground water contamination touted as a problem by many is probably of negligible risk, though this may occur elsewhere in eastern Australia in places like the Surat and Gunnedah Basins. However, local groundwater contamination (with a chance of affecting someone’s water supply bore) is probably on the moderate to high side. The disposal of salty water poses a moderate risk to the environment through adversely affecting large areas of pasture which might be irrigated or a moderate to high level if discharged untreated directly to fresh water streams.

Both of the matters outlined above are difficult to deal with and not knowing about the ins and outs of operators in the region I don’t know how the companies are going to mange these problems. This is ignorance on my part. I can only assume that this has been considered in detail (a legal requirement) so that the management of these problems is adequate.

This is my opinion only and given that opinions can get one in trouble I won’t be commenting on any other matters CSG related for quite some time. I really don’t like getting involved in political matters and it is easy to be carried into them. I hope I haven't been carried into them too far already. If you want to know a bit more about the technical side of coal seam gas extraction and the pollution risks there are some good fact sheets put out by the CSIRO linked to here. Maybe that is why I like rocks so much, they don’t argue with you (too much).

But back onto happier topics. I’ve been most excited by some new information that has come my way, one a University of New South Wales thesis by Leonary Drury on the Richmond Valley stratigraphy, groundwater, dating and much more, and the other is the preliminary geophysical data package released by the NSW geological survey. I’ll be blogging on these topics (plus others) in the coming months.

Monday, 23 July 2012

Geological diversity of the Toonumbar Dam area

Toonumbar Dam is a lovely area that, like so many other places, wish I could visit often. It would be lovely to relax around the dam, maybe stay the night camping or in a cabin. When I last visited, I was rather pathetic... I was looking at the rip-rap on the dam wall and trying to figure out where it was likely to have been quarried! I later found out and visited the quarry to obtain samples and look for structures. But that is a story for another day. As I was saying, the dam is a lovely place and like many beautiful places owes itself to the geological conditions of the area.

The oldest rocks (Mesozoic aged Clarence-Moreton Basin) exposed in the area are actually exposed downstream from the dam itself. Several hundred metres downstream are poor exposures of what appears to be rocks of the Jurassic Walloon Coal Measures, immediately downstream (and all around the dam) is the Kangaroo Creek Sandstone which is obvious to identify up close. The rocks which are apparently of the Walloon Coal Measures are a little harder to distinguish. It is possible that they are members of the MacLean Sandstone (which are considered part of the Walloon Coal Measures) or maybe Woodenbong Beds or even the underlying Bundamba Group but they are certainly younger than the Kangaroo Creek Sandstone.

Inclined bedding in Kangaroo Creek Sandstone
In Iron Pot Creek below the dam. Cross-bedding is also evident
It is worth noting the bedding plains in the sedimentary rocks if you are downstream of the dam. The plains are actually inclined to the west in this area and the further you go down stream the flatter the beds become, then they tilt back the other way (eastward) for a short distance. This is actually a large basin structure called the Toonumbar Anticline (the top of a fold in the rock layers). Another structure, much bigger and of regional significance is located only another couple of kilometres to the east. This is the East Richmond Fault which extends into southern Queensland and down almost to Grafton. I have actually never seen evidence of this fault in the field, but there is geophysical evidence for it and I'm assured it is there. Apparently the fault is much more evident further south between the villages of Mummelgum and Mallanganee.

The large rugged hill and ridge about 5km north of the dam is made from basalt lava, I'm not sure of the exact composition of this rock but it is likely to be part of the Kyogle Basalt which is associated with the Focal Peak Volcano. Interestingly, I think that the basalt is likely not to have been sourced from the actual peak of the volcano but from a distant vent on the side. This is because a few kilometres to the north west just on the north side of the lake is actually one of at least two intrusions of gabbro (the intrusive equivalent of basalt) near Toonumbar, one of these is crossed by Murrays Scrub Road. It is possible that these intrusions were the feeder systems for vents which erupted the Kyogle basalt in this area. This probably demonstrates the nature of volcanism in the area during the Cenozoic period. It seems apparent that the central volcano models of the Focal Peak and even the Tweed Volcanoes appears to be a bit too simplistic.

But, whether you are interested in geology or just enjoy the forests of the Northern Rivers, a trip to Toonumbar Dam is worth while.

Note that the stratigraphy of the Kangaroo Creek Sandstone has been revised since this blog post. See the this post for details.


*O’Brien, P.E., Korsch, R.J., Wells, A.T., Sexton, M.J. Wake-Dyster, K. (1994) Structure and Tectonics of the Clarence-Morton Basin in Wells, A.T. and O'Brien, P.E. (eds.) Geology and Petroleum Potential of the Clarence-Moreton Basin, New South Wales and Queensland. Australian Geological Survey Organisation. Bulletin 241.
*Bell, A.D.M. (1968). Report on the geology of Toonumbar Dam and Appurtenant Works. Water Conservation and Irrigation Commission.

Sunday, 15 July 2012

Who has the answer? Woodenbong, MacLean, Grafton and a Kangaroo Creek

How well do we understand how the Clarence-Moreton Basin was formed? We know a little but not much about areas have never been drilled to understand the stratigraphy. A good example of our lack of geological understanding is the areas to the north and west of Kyogle, Bonalbo, Urbenville, etc. This area on the most recently published geological maps includes the area referred to as the Woodenbong Beds. We know very little about this particular formation.

It was actually Queensland based geologists (Exon et al. 1974) that first named the Woodenbong Beds. Exon et al (1974), (although according to the stratigraphic names database Coote (1986) is considered the first reference) described the lower portion of the Woodenbong Beds as massive to medium bedded pale-grey, fine to coarse grained, cross-bedded, labile (easily decomposed) sandstone. The upper portions were described as fine-medium grained feldspathic sandstone with siltstone, mudstone and minor coal. Stratigraphically, Exon et al (1974) also suggested that the Woodenbong Beds were lateral equivalents of the Kangaroo Creek Sandstone and/or the Grafton Formation. The boundary between the underlying Walloon Coal Measures was also described as conformable (that is, no significant time gap between deposition of the units).

Woodenbong beds possible stratigraphic relationships
Subsequent authors such as Wells & O'Brien (1994) have followed on with the definition provided by Exon et al (1974), who extrapolated the interpretation of the Woodenbong Beds to suggest that they may actually be equivalents of the Injune Creek Group (Springbok Sandstone and Westborne Formation) in the Surat Basin.

However, in the very same volume of work as Wells & O'Brien (1994) a different author, Willis (1994) proposed that the Woodenbong Beds actually underlie the Kangaroo Creek Sandstone (and therefore Grafton Formation), suggesting that the MacLean Sandstone Member of the Walloon Coal Measures was equivalent to the Woodenbong Beds. Willis (1994) also cited other authors such as (McElroy 1963, Ellice-Flint 1973 and Scott 1982 (note I have not seen these three publications)). These authors contradicted Exon et al 1974, and Wells & O'Brien 1994 by indicating that the boundary between the underlying Kangaroo Creek Sandstone is in places disconformable/unconformable (meaning there is a hiatus of deposition or a period of erosion preceding the formation of the Kangaroo Creek Sandstone).

The only thing all of the above authors agree on is that the composition of the Woodenbong Beds is very different from the Kangaroo Creek Sandstone and Grafton Formation. I'm sure you would agree that we obviously need more information to figure this one out!

Note that the stratigraphy of these formations have been recently revised since this blog post. See the this post for details.


*Wells, A.T. and O'Brien, P.E. 1994. Lithostratigraphic framework of the Clarence-Moreton Basin. In Wells, A.T. and O'Brien, P.E. (eds.) Geology and Petroleum Potential of the Clarence-Moreton Basin, New South Wales and Queensland. Australian Geological Survey Organisation. Bulletin 241.
*Wells, A.T. and O'Brien, P.E. (eds.) 1994. Geology and Petroleum Potential of the Clarence-Moreton Basin, New South Wales and Queensland. Australian Geological Survey Organisation. Bulletin 241.
*Willis, I.L. 1994 Stratigraphic Implications of Regional Reconnaissance Observations in the Southern Clarence-Morton Basin, New South Wales In Wells, A.T. and O'Brien, P.E. (eds.) Geology and Petroleum Potential of the Clarence-Moreton Basin, New South Wales and Queensland. Australian Geological Survey Organisation. Bulletin 241.

see *Wells, A.T. and O'Brien, P.E. (eds.) 1994. Geology and Petroleum Potential of the Clarence-Moreton Basin, New South Wales and Queensland. Australian Geological Survey Organisation. Bulletin 241.  for other cited authors.

Sunday, 8 July 2012

The 'older' Rhyolite in the North East

In some of my earlier posts I mentioned that there are many areas in the mountains around the Tweed Valley that are comprised of rhyolite. I mentioned that this rhyolite was formed during eruptions associated with the Tweed Volcano during the Cenozoic era. This rhyolite is called the Nimbin Rhyolite or the Binna Burra Rhyolite (depending what side of the state border you are on). However, there is actually another large distribution of rhyolite not associated with the Tweed Volcano, erupting much earlier, during part of the Mesozoic known as the Triassic. These older mainly rhyolitic rocks are called the Chillingham Volcanics with the type location unsurprisingly located at Chillingham, a village west of Murwillimbah. Those of you who have seen my earlier posts will recognise that I have briefly mentioned the Chillingham Volcanics before, but in this post I intend to go into it further.

Layers of pyroclastics and volcaniclastic of the Chillingham Volcanics
(Murwillimbah - Kyogle Road)

The Chillingham Volcanics have been studied in a fair amount of detail by Roach (1997) in his thesis. This included all of the Triassic volcanic rocks from Brisbane to Uki. So, obviously there is a relationship with the rocks of the southern Queensland, Indeed Roach (1997) indicates that the Brisbane Tuff is a deposit of volcanic rock of rhyolitic composition. The Brisbane Tuff is most well known by the Kangaroo Point Cliffs opposite the Brisbane River in Brisbane City and was erupted during the same general period of time as the Chillingham Volcanics.

The Brisbane Tuff provides a miniature version of the Chillingham Volcanics and is well known because the volcanic centre can be identified in the northern suburbs of Brisbane and the tuff was laid down in the valleys that existed in the Palaeozoic aged basement. The situation which lead to the formation of the Brisbane Tuff also developed further west and south where a larger valley now known as the Ipswich Basin was forming. The eruptions occurred in and around the basin as the crust in this area was subsiding during thermal fluctuations and as the basin filled up with volcanic rocks subsidence continued leading to a very thick unit of mostly rhyolite and reworked volcanic rocks (actually a sedimentary rock known as a volcaniclastic rock). So the Chillingham Volcanics are actually the lower most stratigraphic unit in the Ipswich Basin.

The Chillingham volcanics are mainly comprised of rhyolite in the form of lavas, pyroclastic, ash and tuff deposits as well as the above mentioned volcaniclastics. Many volcanic vents are recognised from structural characteristics of the rocks, however, only one area really shows an obvious modern geomorphological character. This area is around Uki and Clarie Hall Dam where eruptions formed a large mass due to the slow moving nature of the lava. Interestingly the northern most parts of the Chillingham Volcanics in Queensland shows us that there was not just rhyolite but also some andesite and even basalt, but in the area between Chillingham and Uki it is pretty much all rhyolite.

Outcrops of the Chillingham volcanics occur over a long distance with the eastern most side of the Ipswich Basin exposed in New South Wales meaning that a band of the Chillingham Volcanics is visible within the eroded valleys of the Tweed Volcano. The band is actually interupted by the Mount Warning Complex which appears to have intruded right along the line of the pre-existing Chillingham Volcanics. Also the volcanics are covered by the Lamington Volcanics of the Tweed Volcano too, both along the Queensland Border and between Clarie Hall Dam and Evans Head. Indeed the Chillingham Volcanics appears to change composition through this area with authors such as Smith et al 1997 and Cotter 1998 identifying andestite and basalt at Evans Head and an area near Wardell.

The Chillingham Volcanics overlie palaeozoic aged rocks of the Beenleigh Block, mainly rocks of the Neranleigh-Fernvale Group. The overlying rocks are more components of the Ipswich Basin such as the Ipswich Coal Measures and its equivalent (such as the Evans Head Coal Measures).

Although I have said that the Chillingham Volcanics contain the older rhyolitic rock in this area, there are actually still older rhyolites in the region... But I'll talk about those rocks in a future post.


*Cotter, S. 1998. A Geochemical, Palaeomagnetic and Geomorphological Investigation of the Tertiary Volcanic Sequence of North Eastern New South Wales. Masters Thesis, Southern Cross University.
*Roach, A. 1998. Late Triassic Volcanism of the Ipswich Basin, Masters Thesis, Macquarie University.
*Smith, J.V., Miyake, J., Houston, E.C. 1998. Mesozoic age for volcanic rocks at Evans Head, Northeastern New South Wales. Australian Journal of Earth Sciences V45

Monday, 2 July 2012

Mining and the Bible?!

This is a bit of a different type of post than I usually do but I find this quite interesting! If you don't mind I'll put my 'philosophical hat' on.

I've reproduced a part of the Bible below - it is sort of an account of 'mining and gemstones', but more than that it is also a comment on how people are often motivated in life and see things like struggling for the riches of the earth as the most important thing. I agree with the author that the wisdom and understanding described are the most important things in life, not the search for personal riches.

It is also worth noting that in 'gemology' what some of the precious stones are considered to represent (these are the only ones I know, maybe someone else knows the ones I am missing):
  • Lapis Lazuli - wisdom;
  • Gold - wealth;
  • Oryx - overcoming adversity;
  • Silver - love;
  • Topaz - loyalty or being righteous; and
  • Rubies - desire
It is interesting to read the passage, but in particular the section 12-28 by replacing the gemstones with their popular meanings, it actually emphasizes the message even more.

Job 28
1 There is a mine for silver
and a place where gold is refined.
2 Iron is taken from the earth,
and copper is smelted from ore.
3 Mortals put an end to the darkness;
they search out the farthest recesses
for ore in the blackest darkness.
4 Far from human dwellings they cut a shaft,
in places untouched by human feet;
far from other people they dangle and sway.
5 The earth, from which food comes,
is transformed below as by fire;
6 lapis lazuli comes from its rocks,
and its dust contains nuggets of gold.
7 No bird of prey knows that hidden path,
no falcon’s eye has seen it.
8 Proud beasts do not set foot on it,
and no lion prowls there.
9 People assault the flinty rock with their hands
and lay bare the roots of the mountains.
10 They tunnel through the rock;
their eyes see all its treasures.
11 They search the sources of the rivers
and bring hidden things to light.

12 But where can wisdom be found?
Where does understanding dwell?
13 No mortal comprehends its worth;
it cannot be found in the land of the living.
14 The deep says, “It is not in me”;
the sea says, “It is not with me.”
15 It cannot be bought with the finest gold,
nor can its price be weighed out in silver.
16 It cannot be bought with the gold of Ophir,
with precious onyx or lapis lazuli.
17 Neither gold nor crystal can compare with it,
nor can it be had for jewels of gold.
18 Coral and jasper are not worthy of mention;
the price of wisdom is beyond rubies.
19 The topaz of Cush cannot compare with it;
it cannot be bought with pure gold.

20 Where then does wisdom come from?
Where does understanding dwell?
21 It is hidden from the eyes of every living thing,
concealed even from the birds in the sky.
22 Destruction and Death say,
“Only a rumor of it has reached our ears.”
23 God understands the way to it
and he alone knows where it dwells,
24 for he views the ends of the earth
and sees everything under the heavens.
25 When he established the force of the wind
and measured out the waters,
26 when he made a decree for the rain
and a path for the thunderstorm,
27 then he looked at wisdom and appraised it;
he confirmed it and tested it.
28 And he said to the human race,
“The fear of the Lord—that is wisdom,
and to shun evil is understanding.”