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New Study Finds Tectonic Uplift Shaped the Twelve Apostles and Pins Their Limestone at 8.6–14 Million Years

The stacked limestones hold a clear record of past seas that can guide future climate research.

The sediment layers of the Twelve Apostles are among the world’s best-preserved and most accessible records of ancient climate and sea level changes. Picture: Stephen Gallagher
The enigma of Australia's iconic limestone stacks has been uncovered.
Scientists have used millions of microscopic fossilised shellfish to work out exactly how old the iconic Twelve Apostles rock formation is. File picture

Overview

  • University of Melbourne researchers report in the Australian Journal of Earth Sciences that tectonic plate movements lifted and slightly tilted the Port Campbell limestone, then microfossils narrowed its age to between 8.6 and 14 million years.
  • The sea stacks people see today are geologically young features that waves carved only in the last few thousand years after post‑Ice Age sea levels flooded the coast.
  • Field mapping, photographic analysis, and micropalaeontology were combined with unpublished cliff samples from the 1960s to build the most complete timeline yet for the Port Campbell embayment.
  • Small faults and gently leaning layers in the cliffs record ancient earthquakes and regional tilting, which help explain why the coastline continues to erode and reshape.
  • The team will now read the layers like pages to reconstruct Miocene climate and sea‑level swings, with urgency because only eight stacks remain and visitor pressure and ongoing erosion threaten these natural archives.