Microscopic fossils trapped in limestone have shed light on the age of Victoria’s Twelve Apostles, which date back between 8.6 and 14 million years. These towering rock formations draw around 2.8 million tourists each year along the Great Ocean Road, just south of Melbourne.
For geologists like A/Prof Stephen Gallagher from the University of Melbourne, these rocks are more than just pretty views. “Each layer tells a story, a timeline of Earth’s history,” he explains. Over millions of years, shifting tectonic plates have pushed up layers of ancient rock, including Gellibrand marl, which is about 15 million years old, and the yellow-grey Port Campbell limestone formed during the mid-Miocene.
The rocks show some fascinating geological features. The layers don’t rise perfectly straight; they have tilted and cracked over time. If you look carefully at the cliffs, you can spot small fault lines that signal past earthquakes. The sea stacks we see today are relatively new, shaped by erosion.
Gallagher points out an interesting fact: just 20,000 years ago, what is now Bass Strait was a land bridge. You could have walked from the Twelve Apostles all the way to Tasmania, covering about 70 kilometers on solid ground.
Research has detailed the geology of the Twelve Apostles using various methods, including photography and digital mapping. Scientists extracted tiny fossils, called foraminifera, to help date the rock layers. Dr. Matthew McCurry, a palaeontology curator at the Australian Museum, notes that these single-celled organisms are key for dating marine fossils, often used alongside radiometric dating techniques.
Dr. Erich Fitzgerald from Museums Victoria Research Institute highlights that the Twelve Apostles formed during the Middle Miocene Climatic Transition, a period that began significant global cooling and set the stage for future Ice Ages. As these rocks formed, oceans teemed with life, including the enormous Megalodon shark, which existed during a peak time for marine creatures.
The research not only confirms the age of these stunning formations but also emphasizes the ongoing discoveries in geological science. Fitzgerald asserts the importance of dating geological features: “Understanding Earth’s timeline helps us grasp critical events in our planet’s history, from environmental changes to the evolution of life.”
Even with over a century of scientific exploration, Gallagher notes that there’s still much to learn about these iconic sites. Each visit to the Twelve Apostles offers not just breathtaking views but also a glimpse into the deep history of our planet.
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