Geology Rocks!

History and Victorian Geology

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Since the beginning, humans have had a natural curiosity to wonder and explore our environment, it helps us learn and survive as babies and thrive as adults.

How old is… everything? The Earth Sciences are fascinating and diverse; what’s cooler than studying all the stuff on earth and how it came to be? From volcanoes to dinosaurs… not much (in our opinion).

No body could confidently determine the age of the earth before the discovery of radioactivity (not as scary as it sounds) and the development of radiometric dating in the early 20th century.

Interesting Fact?!

In 17th century Europe, it was commonplace to believe that the earth, and the age of the human species were about the same. One historian estimated the earth was about 6000 years old, based on the contextual evidence of the bible….

The discovery and use of fossils as evidence started deeper thinking by philosophers and scientists, and began to shape idea of the earth existing pre-human, a total revelation in thinking.

Over the years, it was found that different fossils existed in very consistent and separate layers of rock around the globe, puzzling together idea’s of what the past looked like, both in the living and non-living world.

Throughout history excavation and mining has been used prolifically all around the world to create understanding of the world we live in as well as take advantage of the rich mineral resources available to create the modern world we know today.

Archaeologist’s have shown that indigenous populations around the great lakes mined and used the copper in Lake superior for over 6000 years. In Europe, mining took off along with colonisation. In the 16th century, colonial empires exploited the precious metals of central and south America relying on the geological knowledge and technical skills of indigenous communities.

Just like humans can develop a history of the world in the past for human existence, through old ruins, letter, writings etc. Geo-historians rely on fossils, volcanoes and rocks to tell a story.

The earth sciences became more regular as professions in the late 1700’s and early 1800’s as industrialisational thinking came about: realising that an understanding of natural resources can help create super useful things.

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As we grow and expand our critical thinking, humans have realised the impacts of  our footprint. Mass scale historic mining, clearing for housing, farming and agriculture: can lead to some often times devastating environmental impacts such as soil salinity, habitat loss and species extinction. So too have we realised the importance of managing all our activities responsibly to co-exist with the natural environment.

In Victoria, both mining and agriculture are tightly controlled and monitored, so as to protect both the community and the environment, whilst still enjoying the economic rewards of fresh and local produce, mineral extraction, job opportunities and community growth development.

Golden History of Victoria’s Geology

Victoria is host to some world-famous gold deposits, boasting many of the richest alluvial prospects ever recorded.

It is hard to imagine a landscape in the same area so vastly different to what we see now, but through geological periods far greater than human timescales, the earth erodes and evolves dramatically. Victoria used to be under water!

Regional Victorian geology is hosted within the Castlemaine Turbidite sequence.
This is a package of moderate depth, marine sediments, that at a point in time have been tectonically uplifted to approximately 400m above sea level. These sediments can be further defined as Sandstones, Siltstone and Black shales. The age of these sediments’ dates to the Ordovician Period, this makes these sediments more than 400,000 years old!

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FIG 1 – Example of Folded Rock Layers

Source – Earle, S., 2021. 12.2 Folding | Physical Geology. [online] Courses.lumenlearning.com.  Go to page  [Accessed 3 March 2021].

At this point Victoria was a quiet marine shelf. Towards the end of the Ordovician, Victoria began to experience a tectonic compressional event. This event squeezed Victoria in an east/west direction, and some believe this compressed Victoria to 50% of its original size.
During this event, the deposited layers of sediment began to fold and warp. These newly formed structures are known as Anticlines and Synclines (FIG 1), these will play an extremely important role in future gold deposition.

Deformation continued for many thousands of years. It came to an apex when the folds couldn’t become any tighter, so they began to break and fault. This created space in the rock and allowed the deep, hot, gold rich fluids to migrate towards surface. As they ascended, they deposited gold in the newly formed space. These faults trend in a north/south direction, right across Victoria (FIG 2).
Near to this time, Victoria’s volcanism began.

The State was intruded by Granites, these are large deep bodies of magma that didn’t make it to surface. They generally stopped rising about 1.5km below surface. This is where they slowly cooled and crystalised into rock. After this, Victoria was relatively quiet, giving the surface time to slowly eroded to expose these deep granites (FIG 2).

FIG 2 – Map of Victoria, highlighting major faults and granites.

FIG 2 – Map of Victoria, highlighting major faults and granites.

Source – Burlinson, K., 2021. Woods point gold deposit, decrepitation and CO2 rich fluids, mineral exploration with fluid inclusions. [online] See Link [Accessed 3 March 2021].

Fast Forward 250,000 years and Volcanism started again. In contrast to the last phase, the magma made it to surface and during this time Victoria would have closely resembled todays Hawaii… with a less pleasant climate.
There were massive lava flows, covering most of the western side of Victoria. There plains are relatively hidden under vegetation, pastureland and cover these days, but are still considered to be some of the world’s largest Lava fields.

Victoria is in a dormant stage currently, the most recent phase of Volcanism finished only 10,000 years ago and created features such as Mt Buninyong near Ballarat and Tower Hill Near Warrnambool.

Victoria has an ancient, complex geological history, with a lot of hidden mysteries and treasures yet to be discovered!