The tallest mountain in Australia and classic geology in New South Wales

Entering the world of academia comes the exciting but terrifying ordeal of presenting research at conferences. Although this was the purpose of my visit to New South Wales (NSW), located in south west Australia, I will save my research details for another post and instead highlight some of the classic geology I was able to encounter on the coast of NSW during my travels. Before trekking to the coast, a “hike” up to the tallest “mountain” in Australia was necessary, as I initially started my journey in Thredbo, NSW. In Thredbo lies one of Australia’s ski resorts and the great Mt. Koscuiszko, highest mountain of them all in Australia!

At a towering 2228m and a grueling gradual incline of 10° for a couple hours toward the top, well… it’s was a nice try for a mountain Australia, nice try 😉 At least I did summit it and can start my highest-mountain-on-each-continent list by checking off Australia… so I’m pretty much ready for Everest now I assume? After that is was a drive down to the coast and a look at some textbook examples of structural geology.

Classic structural geology examples – Veins, Dykes, Beds and Folds

In this post I instead am going to be a bit random and show some isolated, but great outcrops that convey classic concepts in geology. First up are veins; a fracture with hydrothermal mineral infill (and commonly precious minerals like gold). What is important about veins are their internal crystals growth and external shapes can tell you about the direction of opening and displacement of the vein, and therefore what the original stress and shear forces were during formation.

From veins to dykes, somewhat similar concepts apply, but instead of hydrothermal mineral infill, it’s (usual, but not always) an igneous magma. Strange features can occur however when you get magma mingling of partly molten magmas, such as the features at Bingie Bingie Point. Here igneous intrusive appear to have obscured and transitional margins, and cross-cutting small mafic dykes appear to “jump” and step-over during their initial emplacement.

Well, now that I mention jumping, I will “jump” over to the world of sedimentary geology where layers of sands and muds are deposited in a much “cooler” environment. When you imagine a shoreline-type setting, over hundreds to thousands (+) years, different size sediments are deposited from natural processes, such as waves and winds, these will be deposited and eroded to form typical sedimentary structure turbidites and “Bouma” sequences (Powell, 1983a). When you get density differences over layers, like between mud and sand, some neat features can form like flame structures, which form from upward injection of mud into sandstone. Not only cool looking features, but they tell you about the stratigraphic way-up in units, important as things over time seem can get turned around and folded over…

…which leads to the final “neat structural geology examples” in this post (it appears my randomness actually isn’t too bad from one concept to the next, if you don’t mind the cheesy segues). As different compressive stress orientations can change in the earth, original horizontal laid-down layers can be contorted and overturned. Sometimes you get tight, sharp V-shaped “chevron” folds, and other times you can get folds re-folding folds!

Final thoughts

Alright, now, there’s a whole lot more detail and analysis that goes into understanding each of these features, however, for the sake of this blog post I will leave it there. As for my thoughts, well I already expressed my feelings towards “Mount” Koscuiszko … however I did enjoy the area of Threbdo where it is located, and the trip to the coast of NSW was beautiful. Having not really been to too many places in Australia outside Tasmania it was fantastic to see beach after beach, each open and empty with white side, big waves, and very cool rocks!

I wasn’t expecting to see such classic geology examples down there, but it brought me back memories of undergrad and new thoughts and ideas, as just when you think you fully understand something about geology and earth science, you question it and realize you don’t. Well, at least that’s how I feel sometimes, but that’s make it always interesting in my opinion I guess, cheers!

-Stephanie

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