Microscopic fossils embedded within limestone formations have provided new insight into the age of Australia’s Twelve Apostles, revealing that the iconic sea stacks are between 8.6 million and 14 million years old. The findings, derived from a detailed geological study, shed light on the region’s complex history along the southwestern coast of Victoria.

The Twelve Apostles, a series of towering limestone pillars rising from the Southern Ocean along the Great Ocean Road, attract approximately 2.8 million visitors annually. While these formations are widely admired for their striking natural beauty, geologists view them as records of extensive geological processes, according to Stephen Gallagher, associate professor at the University of Melbourne’s school of geography, Earth and atmospheric sciences.

Gallagher explained that tectonic activity over millions of years caused the uplift and tilting of the underlying Gellibrand marl, which dates back 15 million years, as well as the overlying Port Campbell limestone layers that formed during the mid-Miocene epoch. “The tectonic movements didn’t push up the Apostles perfectly straight,” he noted, pointing to the slight tilting and fault lines visible in the cliff faces today as evidence of historical seismic activity.

The sea stacks themselves are comparatively young, having formed as coastal erosion gradually separated them from the mainland cliffs. Gallagher described the view from nearby lookout platforms as a panorama of geological layers, representing millions of years of Earth’s history, with the Twelve Apostles standing as the most recent chapter in that timeline.

The study, published in the Australian Journal of Earth Sciences, utilized an array of modern techniques including photographic documentation, digital mapping, gamma radiation measurements, and the analysis of tiny foraminifera fossils embedded in the rocks. These single-celled organisms, known for their well-documented evolutionary timeline, were instrumental in precisely dating the rock layers.

Dr. Erich Fitzgerald, senior curator of vertebrate palaeontology at Museums Victoria Research Institute, who was not involved in the research, described the study as significant for "bookending" the geological age of both the Twelve Apostles and the adjacent cliffs. The research contributes to a clearer understanding of the region’s geological development, refining previous estimates and appreciating the lengthy natural history encapsulated in the landscape.

Despite the common name, there have never necessarily been twelve stacks; currently, seven remain standing. The new data adds depth to knowledge about these formations, reinforcing their value not only as a tourist destination but also as a rich subject of geological inquiry.