The geological history of the Brisbane and Ipswich areas, Australia
Published: 7 August 2014 (GMT+10)
One of the values of history is that it helps us understand where we have come from and so appreciate our place in the world. Our view of the past will inform the choices we make today, which also shape our future. Especially significant is our understanding of geological history, which provides the broadest and most basic picture of where we fit into the world.
George Orwell said, “He who controls the past controls the future. He who controls the present controls the past.”1 How true. There is a contest at present about geological history, about which version of history will inform the stories in our culture that explain the world. The basic difference in approach stems from the geologist’s belief about the Bible, whether it is a record of true history, or whether it is some sort of legend or fantasy.
George Orwell also said, “The most effective way to destroy people is to deny and obliterate their own understanding of their history.” In the last 50 years with the increased influence of films, media, and public education, there has been a change in the way people understand geological history. That, in turn, has changed our culture. It’s pervasive. At the tourist sites in South East Queensland signs are posted that present just one particular view.2 It’s the same with news reports of fossil discoveries,3 documentaries on national television,4 and so on.
Many people think that these stories about the past are based on objective geological facts, set in stone, so to speak. That is not correct. The lion’s share of the story is based on the shared beliefs and opinions of those within the professional geological community—beliefs that are widely accepted but rarely examined or questioned. Let’s briefly look at how these geological histories are created.
How geological history is developed
A geological history is a story. It’s a story about the past that has been invented by geologists to explain how the rocks came to be in the places where they are found. Geologists observe the rocks in the field. They do not observe the events in the past. The story they tell comes from their imagination. So, although the geologist is constrained by the rocks he sees on the ground, he has a great amount of flexibility about the sorts of stories he can invent.
Let’s look briefly at how this works. The rocks in the field provide the basic geological data, and geologists are good at carefully recording and describing what they see. From these observations they draw conclusions about the area, such as the dollar value of the minerals in the ground, and the area’s geological history.
One of the main tools geologists use to record geological data is the geological map, which shows where different types of rocks are found geographically, plus much detail about their relationships with each other.5 In conjunction with the geological map geologists publish reports in which they describe the characteristics of the different rocks and their relationships with each other.
In this article we will present a geological history of the Brisbane and Ipswich area as part of the broader history of the world recorded in the Bible, a perspective that is not generally heard. Not only will our story be constrained by the rocks in the field, but it will also be constrained by biblical history. We will use the geological information from standard geological publications but we will reinterpret it using a biblical geological model.6 Detailed analyses using the biblical perspective have been applied to two significant geological features of the area. These are the basement rocks7 and the sediments connected with the Great Artesian Basin.8
Figure 1 shows a simplified geological map of the Brisbane and Ipswich area in South-East Queensland, as presented in a popular-level booklet entitled “Rocks and Landscapes of Brisbane and Ipswich”.9 Different rock units are shown as different colours, and we can identify the rocks from the legend on the map. Not only does the legend distinguish the geological units, but it briefly describes their characteristics, plus it arranges them in order. The oldest rocks are at the bottom of the legend and the youngest at the top.
From the information on the map together with the material in the booklet we can now develop the geological history for the area. Geologically, south-east Queensland is an interesting area because of the large variety of different rocks exposed.
The waters of Noah’s Flood rise (First 150 days)
The global Flood of Noah’s time (Genesis 6–8) is the key historical event that explains the rocks of the area. Early during the Flood, in the first 150 days as the waters were rising, the basement rocks of the south-east Queensland area were deposited deep under the ocean.10 Figure 2 shows the current location of these deposits. On the geological map (figure 1) these rocks are coloured grey and indicated at the bottom of the legend. The Warwick Willmott booklet describes these events as occurring 300–400 million years ago, but that length of time was decided by long-age geologists by assuming the rocks were deposited slowly.11 This assumption ignores the catastrophic impact of Noah’s Flood, which they don’t believe happened, and which washes away the idea of millions of years. There was a large volume of a variety of materials deposited including fine silt, poorly sorted sand, beds of chemically deposited silica, and black volcanic lava.12 These display evidence of rapid and catastrophic processes, which is consistent with the nature of the Flood.
After some time, of the order of weeks, tectonic movements in the earth’s crust compressed and uplifted these deposits above sea level. The compression and uplift deformed the rocks, mixed them up, and metamorphosed them. Willmott describes this in his booklet as “Consolidation, intense compression, folding and uplift of the sediments to form a mountain belt.”13 It wasn’t just a mountain belt, but the whole of eastern Australia seems to have been involved in the formation of a number of fold belts around this time, including the New England Fold Belt (figure 2).
The basement area is large and has been given different names depending on where it is exposed, such as the Neranleigh-Fernvale Beds, the Bunya Phyllite, the Rocksberg Greenstone, and the Kurwongbah Beds (see geological map—figure 1).
After these rocks were uplifted, as well as being folded and slightly metamorphosed, the surface of the continent was greatly eroded as the water uplifted with the sediment flowed into the ocean.
Volcanoes erupted violently around this time. It’s possible that the tectonic movements that compressed and uplifted the basement rocks also heated and melted other rocks, generating the molten magma. It is likely that these events were connected. Some of the molten rock erupted over the landscape, now forming the Brisbane Tuff, which is beautifully exposed in the Kangaroo Point Cliffs.14 Other molten rock pooled under the earth’s surface forming granite plutons, such as the Enoggera Granite. These rocks are shown as dark blue and red on the geological map (figure 1), and are toward to bottom of the legend.
Following the uplift, folding, and erosion of the basement rocks, the waters of the Flood continued to rise. They would have flowed back and forth across the land under the influence of tides, tsunamis, and crustal movements. These waters deposited sediment and buried plants and animals in places that today are called the Galilee Basin, Cooper Basin, and Bowen Basin (figure 3). These basins contain abundant coal and gas, which come from the vegetation buried at this time. It is likely that these basins in Queensland were connected to the Sydney Basin in New South Wales and that the water flowing from the uplifted continent flowed into the sea around this area (figure 3). The smaller Ipswich Basin near Brisbane was also deposited around this time (figure 3). Willmott describes this process as “Sediments begin to accumulate on stabilised continent.”15 These sediments are shown as pale blue on the geological map (figure 1) and sit at about the middle of the legend.
Further tectonic movements gently folded these rocks and changed the levels of the land surface, causing the positions of the sedimentary basins to change. This, coupled with rising floodwaters meant that sediment, vegetation, and animals continued to be deposited over a much larger series of basins covering a large part of Eastern Australia. These sediments now contain the water reservoir known as the Great Artesian Basin (figure 4). A geological cross section of the basin (figure 5) shows these sediments up to 3 km thick. Note the dotted lines which show the arrangement of some strata across this vast deposit. Note too that some of these lines are cut off at the ground surface illustrating how the material above the surface was eroded away after the sediment was deposited. That will be explained in the next section. The Woogaroo Subgroup around Brisbane was deposited at this time, and is shown as green on the geological map (figure 1).
Willmott describes this process as, “Widespread accumulation of sediments on river plains of the stabilised continent.”16 He speaks of “river plains” because long-age geologists automatically try to explain the rocks they observe in terms of the sorts of things we see happening today. No doubt the continent did look something like a river plain in flood, with water moving in wide sheets across the continent, probably multiple streams like a braid of hair, depositing sediment. But the flow of water would have been wider, deeper and more constant. The water level was rising and that provided space for more sediment to accumulate. Unlike the river plains we see today, there would not have been trees and forests growing because the sediments were fresh and there was no time for trees to grow since the sediments were deposited. Rather, vegetation would have been washed into the area. The vast coal deposits we find in these rocks represent the vegetation that was washed in as enormous rafts and dumped there. The sediments of the Great Artesian Basin were deposited as the waters of Noah’s Flood were reaching their peak.
Floodwaters recede (Last 220 days)
After around 150 days, the floodwaters eventually reached a maximum. They began to fall after large scale tectonic movements slowly lifted up the continent and lowered the ocean basins. The floodwaters then started to flow off the continent into the oceans. Geologists recognize this period of tectonic upheaval and describe it at the break-up of the supercontinent Pangaea. The Bible describes this period in Genesis 8.
The receding floodwaters, first in wide sheets and then in huge channels, severely eroded the surface of the continent of what is now Australia, and carved the landscape into pretty much the form we see it today. Lots of sediment, kilometres in thickness, was eroded from the surface of the continent during this time. We can see an indication of the extent of this on the geological section of the Great Artesian Basin (figure 5) where some of the strata (dotted lines) are cut off at ground level. This was a period of erosion on the continents, not a period of deposition. Willmott describes this as “A long period of erosion of the landscape …”17
During this time Noah was in the Ark which was resting on the mountains of Ararat. He was releasing birds to try to determine when the waters had receded (Genesis 8). The flow of water gradually reduced in its intensity until the area around Brisbane and Ipswich was likely covered in large ‘lakes’, which continued to drain. Sediment accumulated in these ‘lakes’, and it is now preserved in local sedimentary basins, such as the Oxley and Petrie basins. These are coloured brown on the geological map (figure 1).
While the floodwaters were receding volcanic eruptions occurred, probably caused by stress in the crust as crustal movements produced cracks, and pressurized the areas beneath the crust of molten (or partly molten) rock. This movement and pressure caused the magma to erupt on the surface, now forming the basalt plateaus in the area such as Maleny Plateau. Eruptions during this time also formed the enormous shield volcano in northern New South Wales, called Mt Warning, part of which form the Lamington Plateau.
These eruptions also formed the Glasshouse Mountains, which are the eroded plugs of volcanoes. The composition of the Glasshouse Volcanoes is less basaltic and more granitic than the original basalt lava on the Mapleton Plateau. It’s likely that the Glasshouse eruptions were a later stage of the same eruption, representing melted continental crust, or that the original basaltic magma changed its composition to be more like granite as the magma crystallized.
A significant area of land around these plateaus and mountains was eroded away by the final stages of the receding floodwaters, leaving them exposed as spectacular landmarks. This erosion evidence provides an idea for the timing of the eruptions. These volcanic eruptions are shown red on the map, at Mount Glorious and near Redbank Plains (figure 1—don’t confuse the red for these basalt lavas with similar red used for the granite.)
After the Flood (~4,500 years ago)
After the floodwaters receded, the continent was vegetated by seeds and plants left on the surface. The oceans and waterways were colonized by marine animals that were left in the waters on and around the continent after the Flood. However, the air-breathing land animals that now live in Eastern Australia migrated from Mt Ararat in the Middle East, probably using land bridges through the Indonesian Islands.
All humans living in Australia today also have their origin in the Middle East, having migrated to the continent at various times by various routes. Humans have been responsible for bringing many different kinds of animals, including dingoes, rabbits and cane toads. Landscape erosion, sedimentation and volcanic eruptions have occurred in the approximate 4,500 years since the Flood, but these were minor compared with what happened in the catastrophic year of the Flood itself. On the geologic map (figure 1) the areas that formed after the Flood are called Alluvium, coloured white, and restricted to the coastal areas and river flood plains.
Once we understand how to link geological evidence to the Bible, it’s a simple step to develop a geological history. We begin with the biblical geological model and the classifications that have already been carried out., We obtain geological maps and commentaries and are able to reinterpret the information provided within the biblical model. The geological sequence of the area is shown schematically in figure 6, interpreted from both the long-age and the biblical perspectives.
It is worth noting that the geological sequence of events in the Brisbane area broadly applies to all of eastern Australia. Once we understand the big picture sequence for Brisbane, we can use the same story and apply it to another area that we are interested in. It is helpful to obtain a geological map of the area18 so you can identify the rocks that you see, and then you can link them to this geological history. The main rock packages and events will be much the same, but they have different names in different areas. Different areas will experience the various geologic processes to a different degree. For example, in some areas the basement rocks are severely folded but in others the folds are gentler. In some areas there is little erosion while in others the erosion is severe, removing some of the packages entirely and exposing rocks from deeper in the earth. It’s variations on a theme.
When we can see the connection between the rocks of the landscape and the history of the Bible, it changes our attitude toward life. It opens our minds to the fact that the Bible’s history connects with the real world. The Bible reveals our place in the world, our purpose in life, and our relationship with the God who has spoken to us through the Bible. Noah and his family survived the Flood. We are all descended from him. He is held up as an example for us, as a witness to the reality and faithfulness of God. Hebrews 11:7 says:
By faith Noah, being warned by God concerning events as yet unseen, in reverent fear constructed an ark for the saving of his household. By this he condemned the world and became an heir of the righteousness that comes by faith.
He saved his family because he believed God and did what he was told. And, at the end of the list of heroes of the Faith, we are called upon to follow their example:
Therefore, since we are surrounded by so great a cloud of witnesses, let us also lay aside every weight, and sin which clings so closely, and let us run with endurance the race that is set before us, (Hebrews 12:1)
References and notes
- Orwell, G., 1984, ch. 3, 1949. Return to text.
- Walker, T., Signs point people the wrong way, Creation 34(2):55, 2012. Return to text.
- For example: Walker, T., Huge dinosaurs flee rising waters of Noah’s Flood in Australia: ABC’s Catalyst program reports Kimberley dinosaur footprints, 30 October 2012. Return to text.
- One of many examples would be the TV documentary Australia the Time Traveller’s Guide, UKTV, 2012. This pictures the geological history of Australia as a road trip across the continent spanning billions of years. On which, see Walker, T., Australia: The Time Traveller’s Guide—ABC Mythology, 1 April 2012. Return to text.
- On using geological maps as an aid to Flood geology, see Walker, T., Seeing Noah’s Flood in geological maps, Journal of Creation 25(2):12–14, 2011. Return to text.
- Walker, T.B., A biblical geologic model, in: Proceedings of the Third International Conference on Creationism, R. E. Walsh (ed), Creation Science Fellowship, Pittsburgh, Pennsylvania, pp. 581–592, 1994. Also: Biblical Geology: Properly Understanding the Rocks. Return to text.
- Walker, T., The basement rocks of the Brisbane area, Australia: Where do they fit in the creation model? Journal of Creation 10(2):241–257, 1996. Return to text.
- Walker, T., The Great Artesian Basin, Australia, Journal of Creation 10(3):379–390, 1996. Return to text.
- Willmott, W., Rocks and Landscapes of Brisbane and Ipswich, 2nd Ed., Geological Society of Australia, Queensland Division, Brisbane, Queensland, pp. 40–41, 2012. Return to text.
- Wilmott, ref. 8, pp. 1–2. Return to text.
- See Mortenson, T., The Great Turning Point: The Church’s Catastrophic Mistake on Geology—Before Darwin, Master Books, Green Forest, AR, 2004. Return to text.
- Wilmott, ref. 8, pp. 1–2, 4. Return to text.
- Wilmott, ref. 8, p. 3. Return to text.
- Wilmott, ref. 8, pp. 4–6. Return to text.
- Wilmott, ref. 8, pp. 6–7. Return to text.
- Wilmott, ref. 8, pp. 8–10. Return to text.
- Wilmott, ref. 8, p. 9. Return to text.
- At Geoscience Australia (http://www.geoscience.gov.au) you can download the 1:250,000 scale geological maps which are really useful. (These maps could be called 1:250k Geological Maps). You can also obtain useful publications from Geoscience Australia. Return to text.