Geology of Land, Animals and Water
Age of Reptiles, Shifting Continents, and the Foundation of Modern Australia
The Mesozoic Era (approximately 252 to 66 million years ago) is one of the most dynamic and transformative periods in Earth’s history. Following the mass extinction that ended the Palaeozoic Era, the Mesozoic witnessed the rise of reptiles and dinosaurs, the breakup of the supercontinent Pangaea, and the formation of the modern continents and ocean systems.
Known as the “Age of Reptiles”, the Mesozoic was also a time of major climatic, biological, and geological shifts. The continents moved apart, opening new seas and creating mountain chains, while flowering plants and early mammals appeared.
In Australia, the Mesozoic was the period when much of the continent’s geological character began to take form — particularly through the sedimentary basins, coal deposits, and early volcanic activity that shaped regions like Victoria, Queensland, and New South Wales. Fossils discovered in Victoria’s Otway Basin and Gippsland Basin have revealed an extraordinary story of polar dinosaurs and ancient ecosystems that thrived near the South Pole.
The Structure of the Mesozoic
The Mesozoic is divided into three major periods:
Period
Time (million years ago)
Key Events
Triassic
252–201
Recovery from mass extinction, rise of reptiles, early dinosaurs
Jurassic
201–145
Expansion of dinosaurs, appearance of birds, breakup of Pangaea
Cretaceous
145–66
Flowering plants evolve, modern continents form, ends with asteroid impact and extinction of dinosaurs
Each of these periods played a crucial role in shaping both the biological and geological evolution of the planet — including the foundations of the Australian continent.
Global Geology and Continental Drift
Pangaea and Plate Tectonics
At the start of the Mesozoic, all of Earth’s landmasses were joined in a single supercontinent — Pangaea.
During the Triassic, Pangaea began to fragment due to plate tectonic forces.
By the Jurassic, it had split into Laurasia (north) and Gondwana (south).
Gondwana included what are now Australia, Antarctica, India, Africa, and South America.
By the Cretaceous Period, Australia was firmly part of Gondwana’s southern edge, bordered by shallow inland seas and vast river deltas (Scotese, 2015).
Volcanism and Sedimentary Basins
In Victoria, the Mesozoic saw the formation of major sedimentary basins including the Otway Basin and Gippsland Basin, which later became rich in coal and petroleum deposits (Holdgate et al., 2003).
Volcanic and tectonic activity along the southern margin of Australia was linked to the gradual rifting from Antarctica, which continued into the Cenozoic (McGowran et al., 2004).
These processes established the continental outlines we recognize today.
Climate and Environment
Triassic Recovery
After the catastrophic Permian–Triassic extinction, which eliminated about 90% of species, ecosystems slowly recovered.
The Triassic climate was hot and dry, supporting coniferous forests, cycads, and ferns.
Reptiles became dominant on land, while the first small mammals and dinosaurs appeared.
Jurassic Warmth
The Jurassic Period brought a globally warm and humid climate.
Vast forests of conifers, ferns, and ginkgoes covered much of the world.
Ocean levels rose, and shallow seas spread over continental margins.
The first birds evolved from theropod dinosaurs, marking one of evolution’s most important transitions (Padian & Chiappe, 1998).
Cretaceous Cooling and Diversity
The Cretaceous was initially warm, but by its end climates became cooler and more seasonal.
The rise of angiosperms (flowering plants) transformed ecosystems and supported new herbivores.
In Australia’s polar regions, forests of southern beech (Nothofagus) and conifers thrived under months of winter darkness (Rich & Vickers-Rich, 2003).
Life in the Mesozoic
Dinosaurs
Dinosaurs were the dominant terrestrial vertebrates throughout the Mesozoic.
In Australia, fossils of polar dinosaurs have been discovered in Victoria’s Otway and Strzelecki Ranges, indicating that these animals adapted to life near the Antarctic Circle (Rich et al., 1999).
Species include small ornithopods such as Leaellynasaura amicagraphica and Qantassaurus intrepidus, which likely had keen eyesight to survive long polar nights.
Marine and Flying Reptiles
Marine reptiles such as plesiosaurs and ichthyosaurs swam in the ancient seas of southern Gondwana.
Flying reptiles, or pterosaurs, evolved aerodynamic wings and dominated the skies.
Early Mammals and Birds
Small insectivorous mammals coexisted with dinosaurs, representing early evolutionary experiments that would later diversify in the Cenozoic.
Birds, evolved from dinosaurs like Archaeopteryx, became increasingly widespread during the Cretaceous.
The Mesozoic in Victoria and Australia
Sedimentary and Volcanic Formations
The Otway Basin, Gippsland Basin, and Eromanga Basin in Queensland all contain thick Mesozoic sedimentary layers, including coal seams and fossil-bearing shales.
These deposits reveal changing sea levels, climates, and ecosystems across millions of years (Holdgate et al., 2003).
Polar Dinosaurs and Climate Adaptation
Victoria’s Mesozoic fossil sites, especially along the Otway Coast near Inverloch and Cape Paterson, are globally significant.
The region lay within the polar circle during the Early Cretaceous, yet supported diverse animal and plant life.
Fossils suggest that dinosaurs here were warm-blooded or seasonally migratory, capable of surviving long dark winters (Rich & Vickers-Rich, 2003).
Plant Evolution
Australian fossil floras from this period include ancient conifers, cycads, and the earliest flowering plants, marking a turning point toward the vegetation that would later dominate the continent.
Mass Extinction and the End of the Mesozoic
The Cretaceous–Paleogene (K–Pg) extinction about 66 million years ago ended the Mesozoic.
An asteroid impact near modern-day Yucatán, Mexico, combined with volcanic activity and climate shifts, caused the extinction of around 75% of species, including nearly all dinosaurs (Alvarez et al., 1980).
Surviving groups — birds, mammals, crocodiles, and turtles — inherited a radically changed planet.
In Australia, post-extinction environments gave rise to new mammals, birds, and forests that would dominate the Cenozoic Era.
Aboriginal Perspectives and Deep Time
For Aboriginal peoples, the landscapes shaped during the Mesozoic — mountains, rivers, and plains — are living embodiments of Ancestral Beings.
Volcanic and sedimentary landscapes in Victoria, formed from Mesozoic and later Cenozoic processes, appear in Dreaming stories as acts of creation and transformation.
The idea that the land is alive and ancient, continually forming and reforming, resonates strongly with the geological record of the Mesozoic (Rose, 1996; Neale, 2017).
The Aboriginal understanding of deep time and connection to Country aligns with the scientific narrative of Earth’s vast evolutionary history — both describing a planet in perpetual transformation.
Conclusion
The Mesozoic Era was a world of immense change — from the dominance of reptiles to the origins of modern ecosystems and continents.
In Victoria and across Australia, its legacy endures in fossil-rich cliffs, coal basins, and the ancient rocks that record the breakup of Gondwana and the evolution of unique life under polar skies.
The Mesozoic represents a vital bridge between the ancient Earth of the Precambrian and the more familiar world of the Cenozoic. It was the time when Australia’s deep geological and biological identity — as both isolated and extraordinary — began to take shape.
References
Alvarez, L. W., Alvarez, W., Asaro, F. & Michel, H. V. (1980) ‘Extraterrestrial cause for the Cretaceous–Tertiary extinction’, Science, 208(4448), pp. 1095–1108.
Holdgate, G. R., Sluiter, I. R. & Kelman, A. P. (2003) ‘The origin of brown coal deposits in the Latrobe Valley, Victoria’, International Journal of Coal Geology, 54(1–2), pp. 77–99.
Joyce, E. B. (2010) The Western Victorian Volcanic Plains: A Field Guide to the Newer Volcanics Province. Geological Society of Australia.
McGowran, B., Li, Q., Cann, J. & Padley, D. (2004) ‘The Cenozoic of the Australian southern margin: evolution of a rifted continent’, Australian Journal of Earth Sciences, 51, pp. 125–145.
Neale, M. (2017) Songlines: The Power and Promise. Canberra: National Museum of Australia.
Padian, K. & Chiappe, L. M. (1998) ‘The origin and early evolution of birds’, Biological Reviews, 73(1), pp. 1–42.
Rich, T. H., Rich, P. V. & Vickers-Rich, P. (1999) Dinosaurs of Darkness. London: Allen & Unwin.
Rich, P. V. & Vickers-Rich, P. (2003) A Century of Polar Dinosaurs. Museum Victoria.
Rose, D. B. (1996) Nourishing Terrains: Australian Aboriginal Views of Landscape and Wilderness. Canberra: Australian Heritage Commission.
Scotese, C. R. (2015) Paleomap Project: Plate Tectonics and the Breakup of Pangaea. University of Texas.
Written, Researched and Directed by James Vegter 16/09/2025
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