Marengo: Coastal Geology, Fossils and Reefs

Marengo draws the eye both to the distant history of the Earth and to more recent coastal history. At the rocky headland near Marengo Beacon, non-marine sedimentary rocks from the Early Cretaceous are visible. They are dated to 110 million years ago and formed as the Australian continent separated from Gondwana. Other features include a shore platform with dinosaur tracks and fossil bones, Marengo Reefs Marine Sanctuary, and a five-kilometre loop in Marengo Bush Reserve. This combination offers different points of interest as you consider whether Marengo is right for your trip: geology, maritime history, coastal habitats or a walking loop.

Rocks that tell the story of a river landscape

Directly below Marengo Beacon, layers of mudstone, sandstone and siltstone alternate. They reveal an ancient freshwater river landscape with a backwater area. The headland therefore tells not only of different types of rock, but also of a landscape that was fundamentally different from today’s millions of years ago.

The beacon and the history of navigation

Marengo Beacon was built in 1858 as a navigational aid. It followed two shipwrecks in quick succession at Haley Reef, 100 metres off Marengo. The four Marengo Beacons were completed less than two months after the wreck of the Grange. The beacon’s history is therefore tied to a specific danger to shipping along this stretch of coast.

A later chapter is also part of the structure’s history: in the summer of 2019–20, the beacon was removed after new electronic reef markers made it redundant as a navigational aid. Following calls from residents for it to be restored, the Council decided to replace it using some of the original timber and a modified ball on top. The altered shape was intended to prevent it from being mistaken for the original beacon.

Dinosaur tracks and fossil bones

The broad shore platform at Marengo includes footprints of ankylosaurs and carnivorous theropods, as well as fossil bones of dinosaurs and reptiles. Tracks and bones are different kinds of evidence: the platform contains both prints and fossil remains. This offers another glimpse into the site’s past, alongside the even older rock layers at the headland.

Reef nature and access conditions

Marengo Reefs Marine Sanctuary lies less than 50 metres offshore. The inner reef can be reached by boat, by swimming or in small watercraft; at very low tide, you can walk there from Hayley Point in Marengo. Snorkelling from Marengo Beach is possible when conditions are suitable. Strong tidal currents occur in the Sanctuary. Check local conditions before attempting to access the area by water or at low tide.

Habitats also vary within the Sanctuary. The tidal reef provides a habitat for marine snails such as abalone and periwinkles, tube worms, barnacles and bryozoans. Bull kelp, large brown algae, red and green algae, sea squirts and sponges also grow in the Sanctuary. The subtidal zone is also home to the temperature-sensitive giant kelp (Macrocystis pyrifera). The larger island is a resting place for Australian fur seals, is designated a “Special Protection Area” and is closed to access.

Trails and choosing your destination

Marengo Bush Reserve has a five-kilometre loop trail. This adds a clearly defined walking option to the geological and historical attractions. If you’re looking for a holiday rental in Marengo, you can choose the area based on the experiences that interest you: rocks and fossils, the history of the beacon, reef habitats or a loop through the Bush Reserve. These different themes give you concrete points of reference for matching Marengo to the focus of your trip.

Discover more destinations: Cranbourne South, Rochester, Gruyere, Spotswood, Smeaton, Dixons Creek, Murrabit, Howqua.

For the broader travel overview: Victoria.