Take yourselves on a tour

Bob and Nancy are experienced geologists from Armidale who have developed a range of free self guided tours for many parts of Australia and New Zealand. At the time of this post most focus on the northern parts of New South Wales and New England but continues to expand.

Bob and Nancy's Brooms Head Tour Map

Their tour home page can be found here:
http://ozgeotours.110mb.com/index.html
or alternatively on their business site here:
http://brovey.yolasite.com/free-self-drive-geological-tours.php

I do recommend having a good look to see what is close to you or what would be worth looking at if you are traveling to other parts of the country or even to New Zealand. Bob and Nancy have done an exceptional job of developing these tour guides. They are easy to read, understand and follow.  In my view there is nothing like it available elsewhere on the web.

At the time of this blog post tours that are directly relevant to the Northern Rivers of the New England Region are: (directly linking to the PDF document from Bob and Nancy's site)

• Brooms Head
• Cathedral Rock
• Diamond Head
• Point Lookout
• Red Rock

How cold was it? Glaciers in New England?

I was very, very pleased to receive this comment by Bob (a physical geographer by ‘trade’) a bit more than a week ago. Bob posted the comment on my blog about Point Lookout and has been reproduced below:

"Rod,

You and your readers might be interested in a discovery made around Ebor and Guyra just last week, when I was working with a team of glacial buffs from UQ and UT. We found definite evidence of periglacial activity, presumably from the Last Glacial Maximum, ~20 000 years ago. The best examples were at Guyra on the slopes around Malpas Dam -- clear evidence of solifluction lobes, rock glaciers, snow hollows, and other freeze-thaw features, and what could only be described as incipient cirques -- ponds and bogs sapping back into the escarpment and probably still holding some snow in the frigid Guyra winters. The curious point is that they were between 1200 and 1300 metres, not at the highest points above 1500m where we were expecting them, but all on steep south facing escarpments.

One intriguing feature near Point Lookout, on the road up where it crosses the Little Styx River and at 1450m, was what looked very like a terminal moraine. This of course is a glacial, not a periglacial feature, so it is very hard to believe-but have a look at it, and see what you can make of it. There were at least 16 glacial cycles in the Pleistocene, so maybe one of them at least was really severe, and glaciated this far north. Otherwise, you have to go back to the Permian...

Bob H."


probable solifluction lobes and terraces on hill slope at Malpas Dam

This is exciting stuff to hear about because to my knowledge there is little or no evidence of cold climate landforms in the region. In fact I think the areas of the Tasmania are probably the only areas in Australia were these are frequent, though they have also been possibly identified in the Southern Alps and areas of Victoria. Certainly authors such as Petherick et al. (2011) and Hope (2005) did not identify such equivalent indicators of how far north such extreme cold could be detected. I understand that the cold climate landforms that Bob mentions have been found by researchers various universities such as from the University of Queensland, University of Technology, Sydney and the University of Tasmania. Acting on the tip off from Bob, I found an example of solifluction right on the northern side of Malpas Dam using Google Maps, this one is actually visible from the lookout on the southern side of the dam too (sorry about the quality of the photos, it was a long time since I took them and I didn’t realise what I was looking at that time). Get on Google maps and visit the dam yourself and have a look.


Same solifluction lobes visible south of the hill (same hill as picture above)

Solifluction is caused from the thawing of surface layers of permafrost during the summer leading to the thawed part of the soil profile slipping over the un-thawed permafrost and creating ‘lobes’ of soil. The cold climate structures that have been identified near Guyra are present on the southern side of the hill slopes where the sun was unable to melt much of the ice in the soil and therefore creates conditions of permafrost. Permafrost is not present anywhere on the Australian mainland today and demonstrates a significant change in climate has occurred (though those that know Guyra will still argue it is still uncomfortably cold there!).

What Bob appears to have found near point lookout is even more incredible, as a moraine is formed through the action of glaciers which are accumulations of ice on the surface that slowly moves through a landscape under the action of their own weight. Glaciers in Australia were thought to be limited to Tasmania and the Snowy Mountains. No doubt we will expect to see some published papers on the structure and context of these cold climate features in the region some time in the near future. I can't wait to read the published work that comes from this discovery. 

For further information on the individual cold climate features described above by Bob  visit the glossary, an online encyclopeadia or a good physical geography book such as Geosystems by Christopherson. If you are a little unclear about the locations of these sites and how they fit into a ‘Northern Rivers’ blog then it is worth mentioning this part of the New England, at Guyra and Malpas Dam are right at the head waters of the Gara River which is a tributary of the Macleay River that runs through Kempsey. The New England Highway in the Guyra area is pretty close to the actual crest of the catchments of the northern rivers, with the rivers to the west of it flowing into the Murray-Darling Basin and those to the east to the Pacific Ocean. Point Lookout is in the headwaters of the Bellinger River which runs trough Bellingen and is also part of the headwaters of the Macleay too.

References/Bibliography:

*Christopherson, R.W., 1997. Geosystems Wiley.
*Hope, P. 2005. The Weather and Climate of Australia During the Last Glacial Maximum. University of Melbourne, PhD Thesis, unpubl.
*Petherick, L.M., Moss, P.T & McGowan, H.A., 2011. Climatic and Environmental Variability During the Termination of the Last Glacial Stage in Coastal Eastern Australia: A Review. Australian Journal of Earth Science V.58.

Looking out from the lookout at Point Lookout

The view of the National Park from Point Lookout

One of my favourite places is Point Lookout at the New England National Park between Ebor and Dorrigo. Point Lookout is spectacular for it scenery and feel. On most days you can see the pacific ocean while looking over rugged hills and valleys and I particularly like going there during winter where icicles hang from trees and the waterfalls below the peak are frozen. Point Lookout is nearly 1560metres high which I understand makes it the highest point in northern New South Wales. Like the beauty of the Mount Warning area and Tweed and Brunswick River region, Point lookout owes its attractiveness to the erosion of a large shield volcano.

Point lookout is located on the rim of an escarpment which formed through the erosion of the Cenozoic aged (in this case 19-18 million years) Ebor Volcano and the much older Devonian to Carboniferous (up to ~416Ma) accretionary complex rocks that make up the balance of the New England tablelands. Today, only the north western portions of the lavas (called the Ebor Volcanics) and the central weathered volcanic plug from the Ebor Volcano remain. Research by Ollier (1982) suggested that the central volcanic plug of Ebor Volcano was centred on what is called the crescent which is actually a fairly insignificant looking feature when compared with the rugged valleys today.

It is interesting to note that even though the nearby 23 Million year old Mount Warning (located near and over the Queensland border) is regarded as one of the biggest shield volcanoes in the southern hemisphere, having a height of around 2000 metres before it was eroded, the Ebor volcano was probably a similar size or bigger at its greatest too. It is a bit of a mystery why so little is left of Ebor Volcano when so much remains of the Tweed Volcano/Mount Warning.

The Crescent complex once thought to be Permian (290Ma-250Ma) as recently at the 1970's and was considered part of the intrusives that constitute the New England Batholith. In fact most of the most 'current' geological maps of the area were drawn at this time and so they are incorrect. But since investigations on the radial drainage patterns and geological features by Ollier in the late 1980s followed by dating by Gleadow and Ollier (1987) (which is difficult due to how weathered the Crescent is) and more recent work by Ashley et al (1995) now it is known to be the centre of the Ebor Volcano and aged around 19 Million Years. Ashley et al (1995) also discovered that a nearby basalt called the Doughboy Basalt was around 46 Million years old which is clearly not related to the Ebor volcano but is consistent with other locations where an older Cenozoic basalt is present before the hot spot volcanism that formed the Ebor, Mount Warning and other volcanoes existed.

When I was last at Point Lookout there were several bush walks from long and difficult to short and easy. The most difficult ones take you into the valleys where the rock has been eroded into the older accretionary complex. But even on the short one you can see some interesting 'recent' volcanic rocks. On a section of the walk around the top of the cliffs where security fences are necessary (lest you plummet away!) there is cuttings through the rock. In this rock look closely and you'll see some big crystals within a fine groundmass. This rock is a type of basalt called tholeiite (which means that it has crystalised with a certain geochemical signature) and the crystals are feldspars which is a common rock forming mineral. The feldspars here quite obvious and seem to catch the light at two angles, this feature is called twinning and is characteristic of the calcium rich variety of feldspar called plagioclase. Along the bigger walks below the point dacite can be found as well as basaltic and dacitic breccias at the stunningly beautiful during winter, weeping rock and numerous palaeosols.

The remnant of the shield volcano shows the characteristic radial drainage pattern for volcanic shields but the eroded central areas of the volcano (including the caldera if there was one) drains fairly directly to the east via the Nambucca River. The radially draining creeks and rivers are well known for their waterfalls such as Dangar Falls and Ebor Falls.

The road from Dorrigo to Armidale is not a busy route, it is often missed by many people but I always recommend people visit the New England tablelands because of its beauty and uniqueness in Australia. Point lookout is just off the Waterfall Way which name probably gives you an indication of many of the other attractions. In my opinion, the depths of winter are the best times to visit to get the mood and subtle beauty of the area. I should get back there myself... it has been too long since I was last there.

You may be interested in a self-guided geological tour. Bob and Nancy from Armidale have a wonderful site which includes an excellent (and expanding) range of geological tours including ones of the Northern Rivers Area. Their tour guide on Point Lookout can be accessed from their webpage (very much worth the look) or  directly linked from here.   

References/bibliography:

*Ashley, P.M., Duncan, R.A. & Freebrey, C.A. 1995 Ebor Volcano and the Crescent Complex, northeastern New South Wales: age and geological development. Australian Journal of Earth Sciences V42.
*Gleadow, A.J.W. & Ollier C.D. 1987 The age of gabbro at the Crescent, New South Wales. Australian Journal of Earth Sciences V34.
*Ollier, C.D. 1982 Geomorphology and tectonics of the Dorrigo Plateau, NSW. Australian Journal of Earth Sciences V29.