The geological history of the Townsville area, Australia

From a biblical Flood perspective

by Tas Walker

Early Flood—the Ascending phase

The oldest rocks well exposed in the Townsville district are around Charters Towers and are the remnants of a once-extensive sequence of sediments and volcanics. These were deposited rapidly and early during the global Flood (Genesis 6–8). The remains of these rocks have been called the Lolworth-Ravenswood Block. Soon after they were deposited they were crumpled (deformed) and metamorphosed (recrystallised) into schist, quartzite and gneiss.

1. The Tasman Zone:  Geologically, the first event in the Townsville area was the deposition of the basement rocks, an event that affected the whole of eastern Australia. Around Townsville the basement is not exposed but is visible in the area around Charters Towers.

2. Galilee, Cooper, Bowen, and Sydney Basins:  Not present in the Townsville area, probably not deposited in the area but possibly, less likely, eroded by receding floodwaters.

3. Great Artesian Basin sediments:  Again, not present in the Townsville area, probably eroded by receding floodwaters.

After this, and also during the early phase of the Flood, the eastern part of Australia was dominated by geological developments in the Tasman Zone. Rocks deposited at this time are now exposed in the fold belts of eastern Australia. A large volume of material was deposited including fine silt, poorly sorted sand, beds of chemically deposited silica, black volcanic lava and fossiliferous limestone.

Tectonic movements in the earth’s crust compressed and uplifted these deposits above sea level. Some rocks were folded by the compression while others were severely deformed and disrupted. The basement areas are large and have been given different names depending on where they are exposed (figure 1). The exposed rocks were severely eroded as the water uplifted with the sediment flowed off the continent.

Violent volcanic eruptions took place soon after (or while) the basement rocks were compressed and uplifted (possibly the catastrophic compression heated and melted the sediment locally). Some of the molten rock erupted over the landscape while other molten rock pooled under the earth forming granite plutons. These features form the major granite and volcanic rock exposures of the Townsville area such as Mt Stuart, Mt Storth and Fredrick Peak.

Because of this rapid uplift the water flowed off the continent depositing sediment and animals in the Galilee, Cooper and Bowen Basins and probably also in the Sydney Basin to the south where the waters likely flowed into the sea. (figure 2). Tectonic movements gently folded these rocks and changed the depositional environment. These rocks are not present in the Townsville area. Either they were eroded away after they were deposited or they were not deposited.

Middle Flood—the Zenithic phase

The changed conditions meant that sediment, vegetation and animals were 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 3). Again, these rocks are not present in the Townsville area because they have either have been eroded away or they were not deposited.

Eventually the Floodwaters reached their peak and tectonic movements slowly lifted up the continent and lowered the ocean basins. The Floodwaters then started to flow off the continent into the oceans.

Late Flood—the Recessive stage

The receding floodwaters (first in huge sheets and then in wide 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. While the Floodwaters were receding, volcanic eruptions occurred (caused by earth movements that produced heating, pressure and cracks). These eruptions now form basalt plateaus along eastern Australia such as the basalt cap in the Carnarvon Gorge area and the well-known plateaus near Brisbane such as Lamington Plateau and Maleny Plateau. Eruptions during this time also formed volcanic plugs such as the Glasshouse Mountains and Mt Warning. The land around these plateaus and mountains was eroded away by the final stages of the receding floodwaters, leaving them exposed as spectacular landmarks. The receding floodwaters eroded the areas around Townsville, forming the extensive scarp to the west during the sheet flow phase. The receding floodwaters also left sediment in numerous small, local sedimentary basins in various parts of the state.

Post-Flood—colonization by plants, animals and people

After the Floodwaters receded the continent was vegetated by seeds and plants left on the surface after the Flood. In the early stages of the post-Flood period the Ice Age caused ocean levels to drop, and continued sedimentation, but on a much smaller scale, deposited sediments in smaller basins along the coastline. Toward the end of the Ice Age the ocean levels rose to around what they are now, isolating the near shore islands such as Magnetic Island.

The oceans and waterways were colonised 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 landbridges through the Indonesian Islands. Humans have probably been responsible for much animal migration. Landscape erosion, sedimentation and volcanic eruptions have occurred in the 4,300 years since the Flood, but these have been minor compared with what happened in the catastrophic year of the Flood itself.

4. Cross section of the sediments comprising the Great Artesian Basin which stretches more than a thousand kilometres across eastern Australia. The sediments are not present in the Townsville area.

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