Tharz gold in them hills!

Jim Belshaw, blogger and New England self government advocate has several interesting blogs. I thought I'd take the opportunity to share his latest New England History blog post on gold in the Timbarra/Rocky River area.

Jim has a very interesting writing style and I enjoy his blogs. He also seems to capture many parts of the New England landscape and history that go poorly documented. I understand this fascinating article was also published in the Armidale Express Extra which is not available online.

Doctor John Lindsay

Recently I had a discussion with Gordon Smith who has a wonderful photoblog on the New England. Gordon was curious about some conglomerate that he and a well-known bushwalking writer, Bob Harden had come across in the Oxley Wild Rivers and Carrai National Parks. During the discussion, it became apparent that most of the understanding of the geology of the area was established in the early 1960's by a student named John Lindsay. Later, Bob informed me that John Lindsay was well-known for his later work for NASA. 

Photo of John Lindsay obtained from the Luna and Planetary Institute

On occasions I've posted short blogs on individual geologists and given John Lindsay's background I thought it worth doing the same for him.

John was born in the middle of World War 2 in January 1941. I don't know where he was born or what schools he attended but his tertiary education was in sedimenary geology with a solid background in chemistry, physics, mathematics, and statistics, earning his Bachelor of Science Degree (with Honours) in 1962 and Master of Science degree in 1964 from the University of New England.

During his time at UNE, John completed mapping and research projects which identified anomalous terrestrial rocks in a terrain that was mainly of marine origin. He worked in an area that was very difficult to understand because it was so broken up into different blocks by numerous faults. This is the area that is the gorge country between Kempsey and Walcha which includes the Oxley Wild Rivers and Carrai National Parks. To the best of my knowledge this day the geology of the area has not advanced much since John's work. This area was the subject of my discussion with Gordon Smith and Bob Harden.

Following his UNE study, John moved to the United States where he studied for his PhD at Ohio State University. Following his PhD John obtained a position with NASA in the Apollo Program where he was involved in Luna mission planning and the training of astronauts. John’s other professional background also included positions as Research Scientist at the Marine Science Institute of the University of Texas, Program Manager at Exxon Production Research, Adjunct Professor at Oxford University, and NRC Senior Research Associate at the Astrobiology Institute at NASA Johnson Space Center. While he was at NASA John studied extreme environments on Earth as analogues for extra-terrestrial environments. This lead him to become an authority on aspects of Antarctic geology.

John also maintained contact with Australia and held an academic position at La Trobe University in Victoria in the 1970's and joined the Bureau of Mineral Resources in Canberra in 1984. He spent much of his time developing a deep understanding of the inland Australian sedimentary basins and the ancient sedimentary rocks of the Pilbara. His works on the Pilbara rocks in particular helped us to learn about the very earliest life on earth.

John contributed not just to our present understanding of geology but also to life on earth and even the search for life in the universe. From what I have read he also was held in high regard with those that worked with him.

John died in the United States from cancer in June 2008.

References/bibliography:

Much of the information I have about John Lindsay was obtained from his Luna and Planetary Institue Obituary and the dedication of the book Earliest Life on Earth: Habitats, Environments and Methods of Detection by Golding& Glickson (2011). However, I've used a few internet sources that I seem to have misplaced.

*Golding, S., Glickson, M. 2011. Earliest Life on Earth: Habitats, Environments and Methods of Detection. Springer.

A list of John's published papers, conference proceedings etc. can be found at this Luna and Planetary Institute webpage:
http://www.lpi.usra.edu/lpi/lindsay/papers/lp_papers/

A list of his most recent papers can be found here:
http://www.lpi.usra.edu/lpi/lindsay/papers/

How wonderfully marbleous!

There are some rock types that are very common around the country and around the world that just don’t seem to rate much of a mention in the Northern Rivers. One very common rock is limestone formed from corals in a shallow sea, just like the Great Barrier Reef. Limestone is made almost entirely of the mineral calcite. Some parts of the world have vast terrains dominated by limestone called karst landscapes and it is quite distinctive. Limestone terrains sometimes form amazing subterranean cave systems as the stone is dissolved by rainwater infiltration into the formation. These karst terrains include north-west Mexico and other parts of North America, a giant band through northern England and a wide area of South Australia along the Great Australian Bight. However, it is a landscape absent from the Northern Rivers.

Outcrop of limestone north west of Tabulam

Having said that vast areas of limestone don’t exist in the region it is worth noting that they do exist in small areas here and there within the older rocks of the New England Orogen. The reason for this is interesting. The New England Orogeny was a period of mountain building during periods of plate collision which included a period of subduction of an oceanic plate under the Australian continental landmass during the Silurian period. The material on the surface of the oceanic plate was often accreted, that is scraped off and squashed onto the Australian continent. Seamounts are old islands in the middle of the sea. Such as, those around modern day Hawaii or Fiji. The seamounts were accreted onto the continental mass where they created little pockets of limestone in midst of the jumbled, squashed mass of deep seafloor sediments.

This means that if you find limestone in the New England area you are actually finding the preserved remnants of a little tropical island reef or lagoon. An especially nice thought, when you find some limestone on a cold frosty New England winter morning. One relatively accessible place to see some limestone is an old quarry on the Pretty Gully Road just north-west of the town of Tabulam which sits on the Bruxner Highway crossing of the Clarence River. The stratigraphic unit that the limestone of the area is part is the Emu Creek Formation which also includes areas of interesting fossils (more about that in yet another post). However, the quarry is interesting for more reasons than just as an occurrence of limestone.

Following the period of subduction and accretion a period occurred where intrusions of molten magma pushed their way into the accretionary sedimentary rocks. It occurred a couple of times including during the Late Permian to Early Triassic and created one part of what is referred to as the New England Batholith. The batholith is an array of granitic rocks that stretches through the whole New England Tablelands. The intrusions of the Late

fresh face of limestone - note the sparkles from the calcite crystals

Permian to Early Triassic included the emplacement of the Bruxner Monzogranite, a type of granite pluton (more about this specific rock in a future post). This pluton heated up and metamorphosed the rocks around it and one of which was that body of limestone near Tabulam. Contact metamorphism of limestone creates the rock called marble and this has happened at Tabulam. Although, the quality of marble is questionable because of the amount of impurities.

Other things happened to the limestone during metamorphism too. The transfer of fluids into and out of the cooling magma created chemical reactions which concentrated elements such as iron. This process develops what is called a skarn, a body of altered limestone with sometimes economic amounts of minerals. The minerals in a skarn can be diverse and very, very valuable but the minerals are based on the chemistry of the granite pluton. In the case of the chemistry of the Bruxner Monzogranite, there was not much of value except lots of iron which formed abundant amounts of the minerals magnetite and haematite. This has been considered for mining in the past but the small size and low grade means it is not a viable iron mine.

There are other small limestone deposits all around the New England and all of them are interesting for one reason or another. Some north of Inverell have lovely caves, others near Tamworth are mined for lime on a large scale. While others, just have interesting little features that illustrate what happened during the formation of our region.

References/bibliography:

*Bryant, C.J., Arculus, R.J. & Chappell, B.W. 1997. Clarence River Supersuite: 250Ma Cordilleran Tonalitic I-type Intrusions in Eastern Australia. Journal of Petrology. v38.

*Lishmund, S.R., Dawood, A.D. & Langley, W.V. 1986. The Limestone Deposits of New South Wales. 2nd Ed. Geological Survey of New South Wales

The Koukandowie Formation has a cool Name

Previously I’ve completed blogs on the stratigraphy of the upper units of the Clarence-Moreton Basin. These upper units have been the Grafton Formation (youngest at Late Jurassic), Woodenbong Beds, Kangaroo Creek Sandstone and Walloon Coal Measures including the Maclean Sandstone Member of that unit (Middle Jurassic). Now, as we get towards the middle units of the basin we get into the Early Jurassic with much more complexity to the mode of formation of the geological units. Because of this the stratigraphic units have been divided into groups, subgroups, formations and members. The First one that I will tackle is the Koukandowie Formation, which is part of the Marburg Subgroup which in turn is part of the Bundamba Group.

The Koukandowie Formation actually is made up of an additional three members known as the Heifer Creek Sandstone Member, Ma Ma Creek Member and Towallum Basalt. But I’ll focus on these individually in future posts, for the time being it is worth noting that the Towallum Basalt is a very important unit for understanding the relative age relationships of all of the units in the Bundamba Group. For the time being I’ll focus on the Koukandowie Formation specifically.

Bundamba Group with conglomerate and abundant organic fragments - Tabulam

Unfortunately I do not have a photo specifically of the Koukandowie Formation. But I have attached a photograph a similar type of rock as the Koukandowie of the an undifferentiated part of the Bundamba Group.

The Koukandowie Formation was deposited in a dominantly fluvial (riverine) environment. Essentially the unit is comprised of sets of channel lithic sandstone (sandstone made from fragments of older rock) with some finer grained rock such as siltstone and even shale. But the formation also thin layers of conglomerate or occasional woody fragments that have turned into coal. The way the lithic sandstone was deposited means that a feature known as cross-bedding is very common and this structure is further evidence of its fluvial origin. The exact nature of these particular cross-bedding structures it interpreted by Wells & O'Brien 1994 as meaning that the river system that created the Koukandowie Formation was not a meandering stream but fairly straight. A modern example might be the middle reaches of the modern day Clarence River.

A rough stratigraphic guide to the Bundamba Group
(Walloon Coal Measures are above and Gatton Sandstone under)

The Koukandowie Formation was considered an important formation for gas and oil exploration in the region. The Koukandowie was thought to be a generally an impermeable unit, that is, stops the migration of fluids and gases such as oil and natural gas. This means that the underlying units of the Bundamba Group which are more conducive to forming and storing these gases and fluids may retain them in structural traps (such as folds in the earth or faults). How effective this unit has been seems to be a bit hit and miss. I understand that the NSW Government and some companies during the 1970’s and 1980’s had some success with this model but not enough to make it viable financially at the time. More recent work by exploration companies has shown this to be on its own not-viable. But when combined with similar modes of gas source rocks in the overlying Walloon Coal Measures, other more deeply buried organic rich units and other sources of gas directly from coal seams the economics seem to have looked good for some companies.

As for ground water sources, like the overlying Walloon Coal Measures the Koukandowie Formation does not contain much in the way of useful fresh groundwater. This is for two reasons:

1. the finer grained components of the formation tend to contain more salt due to the some of the sedimentary depositional environment; and
2. the Koukandowie Formation tends to show very little lateral porosity. This means that the water is stored in smaller localised aquifers of low long term yield. 

These reasons also imply the nature of recharge of what aquifers to occur in the area. Essentially vertical percolation from surface water through fractures is the main driver of aquifer recharge. Though there are exceptions due to the location of the sub-units in the Formation.

As for the name the Koukandowie Formation takes its name from Mount Koukandowie which is located near Nymboida. The formation outcrops in a relatively thin band in from the margins of the Clarence-Moreton Basin. I don't think that the formation outcrops anywhere in the middle areas the Clarence-Moreton Basin but certainly occurs at within the basin depth. The formation tends to weather and erode easily and therefore most of the outcrop of the unit shows relatively subdued landforms of rolling hills.

References/bibliography:

*McMahon, G.A. & Cox, M.E. 1996. The relationship between groundwater chemical type and Jurassic sedimentary formations: The example of the Sandy Creek Catchment, Lockyer, southeast Queensland. Mesozoic 96 Conference at Brisbane - extended abstracts.
*O’Brien, P.E. & Wells, A.T. 1994. Sedimentology of the Bundamba Group. In Wells, A.T. & O’Brien, P.E. 1994. Geology and Petroleum Potential of the Clarence-Moreton Basin, New South Wales and Queensland. Bulletin 241. Australian Geological Survey Organisation
*Wells, A.T. & O’Brien, P.E. 1994. Lithostratigraphic Framework of the Clarence-Moreton Basin. In Wells, A.T. & O’Brien, P.E. 1994. Geology and Petroleum Potential of the Clarence-Moreton Basin, New South Wales and Queensland. Bulletin 241. Australian Geological Survey Organisation.
*Wells, A.T., O’Brien, P.E. Willis, I.L. & Cranfield, L.C. 1990. A new lithostratigraphic framework of the Early Jurassic units in the Bundamba Group, Clarence-Moreton Basin, Queensland and New South Wales. B.M.R. Journal of Australian Geology and Geophysics. V11.