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Australian Geology and Minerals

In the museum we have two cases of mineral specimens from Australia, as well as other specimens in other exhibits. The main exhibit features specimens from the John Webber Collection.

An Introduction to Australian Geology

Australia is home to a wide range of geological features, ranging from some of the most ancient rocks to fairly modern volcanic eruptions. The country’s geology is shaped by its unique position on the planet, which has resulted in a complex history of geological processes.

One of the most significant geological features of Australia is the Great Barrier Reef, which is the largest coral reef system in the world. This natural wonder is a product of millions of years of biological and geological processes, including the uplift of the Australian continent, the formation of coral reefs, and the impact of sea level changes over time. Coral reefs can only grow at a relatively shallow depth, and the changing sea level has allowed the expansion of the reef to its current size.

Another prominent feature of Australian geology is the Great Dividing Range, stretching over 2100 miles along the eastern coast of the continent. This mountain range was formed over millions of years as a result of tectonic activity and erosion, and it is home to a range of diverse ecosystems and habitats.

Map of the Geological Regions of Australia by Rollinator, CC BY-SA 3.0

On Right: View of the Great Dividing Range by fir0002flagstaffotos [at] gmail.com Canon GFDL 1.2, https://commons.wikimedia.org/w/index.php?curid=876831

The Range reaches from the tip of Queensland to the state of Victoria. It is primarily sedimentary rock, including sandstone, shale, and mudstone. These rocks were deposited during the Paleozoic Era (541 to 252 Ma). At that time, the eastern coast of Australia was covered by a shallow sea, and sediments from both rivers and the local marine environments were deposited on the near-shore sea floor. These sediments were compacted and cemented to form the rock layers that make up the Great Dividing Range.

In addition to sedimentary rocks, the Great Dividing Range also contains several igneous rocks, including basalt and granite. These rocks were formed more recently during periods of volcanic activity during the Paleozoic and Mesozoic eras. The basalt, in particular, is the result of lava flows that covered large areas of eastern Australia during the Jurassic period (201 to 145 Ma).

The uplift of the Great Dividing Range occurred during the Carboniferous period when Australia collided with what are now parts of the now Pacific Plate.

The Indo-Australian Tectonic Plate by Alataristarion, Eric Gaba CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=39885183

The range has since then been subject to erosion, shaping the current landscape. The range contains several valleys, gorges, and waterfalls, all formed by the erosion of the sedimentary rock layers. The range is also home to several significant rivers, including the Murray and Brisbane Rivers.

Australia’s rich mineral resources, including iron ore, gold, and coal, have been a major contributor to the country’s growth and economy, and continue to be an important part of Australia’s industrial and economic landscape.

One of the most fascinating aspects of Australian geology is the presence of ancient rocks dating to at least 3.8 billion years old. These come from the Pilbara region and provide important insights into the early history of the Earth and the evolution of life.

Pilbara by Yewenyi at the English-language Wikipedia, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=13266082

The Pilbara region is located in the northwestern part of Australia, spanning over 200,000 square miles in Western Australia. It is a largely arid and remote region, characterized by rugged landscapes, and vast deserts.

Geologically, the Pilbara region is best known for its extensive deposits of iron ore, which account for a significant portion of the world’s iron ore exports. The iron ore deposits are mainly located in the Hamersley Range, a mountain range that stretches for almost 400 miles. The Hamersley Range is composed of a sequence of banded iron formations, which were formed over 2.5 billion years ago during the Archean Eon.

In addition to iron ore, the region contains significant deposits of other minerals, including gold, copper, lead, and zinc. The region is also home to several large gas and oil reserves, particularly offshore.

Australia sits firmly away from the edges of a tectonic plate, and without volcanic hotspots, there are no active volcanoes. The last volcanic activity on the continent occurred over 4,000 years ago.

Geological Exploration

Sir Roderick Impey Murchison photographed by Camille Silvy in 1860

The Western geological exploration of Australia began with the arrival of European explorers in the late 18th century. The first recorded geological observations were made by British navigator James Cook during his voyage along the east coast of Australia in 1770. Cook noted the presence of coal seams near what is now the city of Newcastle in New South Wales.

During the early 19th century, several expeditions were launched to explore the geology of Australia. One of the most significant of these was led by Scottish geologist Sir Roderick Murchison in the 1840s. Murchison’s expedition focused on the geology of the eastern states of Australia, including New South Wales, Victoria, and Tasmania. The expedition resulted in the publication of a landmark geological map of the region, which established the geological framework for much of Australia.

Throughout the 19th and early 20th centuries, several other geological surveys were conducted across the continent. In 1861, the Geological Survey of Victoria was established, followed by the Geological Survey of New South Wales in 1875. The establishment of these surveys marked a shift towards more systematic and scientific approaches to geological exploration.

During the 19th and early 20th centuries, several significant discoveries were made in Australia that helped to establish the country as a major source of mineral resources. These included the discovery of gold in Victoria in the 1850s, which led to a gold rush and the establishment of the mining industry in Australia. Many miners who were disappointed by their lack of immediate success in the 1849 California gold rush headed to Australia.

Other important discoveries during this time included the discovery of silver, lead, and zinc deposits in the Broken Hill region of New South Wales in the 1880s. Mines are still active in the area, including the Broken Hill mine itself.

Miner’s Memorial at the Line of Lode mine commemorates over 800 workers who lost their lives working the mine. By Jjron – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=2985070

In the 20th century, geological exploration in Australia became increasingly focused on the search for oil, gas, and other hydrocarbons. In the 1960s, the discovery of the North West Shelf gas fields off the coast of Western Australia marked a major milestone in Australia’s exploration of hydrocarbons. The development of these fields has since made Australia one of the world’s largest exporters of liquefied natural gas.

Shark Bay and Stromatolites

Photo: Shark Bay and Stromatolites

Shark Bay, located in Western Australia, is home to one of the world’s most unique and important natural wonders – the stromatolites. These living rock formations are estimated to be around 3.5 billion years old, making them some of the oldest living organisms on Earth. They are believed to be important drivers in the increase of oxygen in the planet’s atmosphere that allowed plants and animals to evolve.

Stromatolites are layered rock formations created by the growth and mineralization of microbial mats. These mats are created by cyanobacteria, also known as blue-green algae, which are capable of photosynthesis. The cyanobacteria in the microbial mats trap sediment particles and minerals from the water, eventually creating layers of sediment and calcium carbonate. Over time, these layers become compacted and form the distinctive dome-shaped rock formations known as stromatolites.

The stromatolites of Shark Bay are located in Hamelin Pool, a shallow, sheltered bay on the eastern edge of Shark Bay. Hamelin Pool is an ideal location for stromatolite growth, as the high salt content and low tidal movement of the water create a stable environment for microbial mat growth.

The stromatolites of Shark Bay are the largest and most diverse living examples of these formations in the world. They can reach up to 1.5 meters in height and can be found in a range of shapes and sizes. The microbial mats that create the stromatolites are made up of a variety of cyanobacteria species, each with its own unique characteristics and preferences for specific conditions.

Stromatolites grow incredibly slowly, at a rate of just 0.3 to 0.5 millimeters per year. This slow rate of growth means that the stromatolites of Shark Bay have been forming for thousands of years. The stromatolites are also incredibly resilient and can survive in harsh environments where other life forms cannot, such as extreme heat, high salinity, and low oxygen levels.

The stromatolites of Shark Bay are an essential part of the ecosystem of the region. The stromatolite field acts as a nursery and area of shelter for many species of fish, crustaceans, and other invertebrates.

The Shark Bay stromatolites are one of the most important natural wonders in the world. They provide valuable information about the history of life, as they are believed to be one of the earliest forms of life. The stromatolites are also important for their role in the ecosystem of Shark Bay, providing a habitat for a diverse range of marine life.

The museum has fossil stromatolites from Arizona on display.

Significant Places of Geological Interest

1. Uluru-Kata Tjuta National Park, Northern Territory: This location is home to Ayers Rock/Uluru and Kata Tjuta (The Olgas), two massive sandstone rock formations that hold great cultural significance for the indigenous Anangu people. Uluru is one of the world’s largest monoliths and is a sacred site for the Anangu people.

2. Great Barrier Reef, Queensland: The Great Barrier Reef is the world’s largest coral reef system and is home to a vast array of marine life. It is also one of the world’s most popular tourist destinations, attracting millions of visitors each year.

3. Kakadu National Park, Northern Territory: Kakadu is a vast, biodiverse wilderness that contains wetlands, savannas, and rugged stone escarpments. It is home to many unique species of plants and animals and has been inhabited by indigenous peoples for tens of thousands of years.

4. The Kimberley, Western Australia: This region is known for its rugged terrain, ancient rock formations, and spectacular coastline. It is home to many unique species of plants and animals, including the iconic Boab tree.

Map showing the extent of the Kimberly region in Western Australia, by User:Brisbane, User:Martyman – Derivative of File:Northern Territory locator-MJC.png based on File:Kimberley_region_of_western_australia.JPG and File:Regions_of_western_australia_nine_plus_perth.png., CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=14102655

5. Flinders Ranges, South Australia: The Flinders Ranges is a mountain range in South Australia that is rich in geological history and contains many important fossil sites. It is also home to unique flora and fauna, such as the Yellow-footed Rock-wallaby.

6. Lake Eyre, South Australia: Lake Eyre is Australia’s largest salt lake and is an important site for migratory birds. It is also a significant geological location, as it contains evidence of past climate change and ancient river systems.

7. Nullarbor Plain, Western Australia/South Australia: The Nullarbor Plain is a vast, treeless expanse of limestone that contains many important fossil sites. It is also home to unique flora and fauna, such as the Nullarbor Dwarf Bettong.

8. Tasmanian Wilderness, Tasmania: The Tasmanian Wilderness is a rugged and remote wilderness area that is home to many unique species of plants and animals. It is also home to some of the oldest rocks in Australia, dating back over 1 billion years.

9. Blue Mountains, New South Wales: The Blue Mountains are a mountain range in New South Wales known for its dramatic scenery and unique rock formations. It is also home to many unique species of plants and animals, such as the Blue Mountains Water Skink.

10. Cradle Mountain, Tasmania: Cradle Mountain is a mountain in Tasmania that is known for its spectacular scenery and unique geological formations. It is also home to many unique species of plants and animals, such as the Tasmanian Devil.

Ayers Rock, photo by Ek2030372672 – CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=105272234

Australian Minerals Word Search

Other Places of Geological Interest

Superposition Reading Exercise