Australia: The Land Where Time Began

A biography of the Australian continent 

Narrabeen Group 

The Narrabeen Group, mostly from the Lower Triassic, the Olenekian, and this shale unit is the lowest of the 3 units in the series. It lies conformably below the Hawkesbury Sandstone from the Middle Triassic, the Anisian, as well as the Mittagong Formation, a transitional unit, and the Wianamatta Group, the uppermost unit in the series from the Anisian-Landinian. The rich microfossil record and the plant/vertebrates assemblages have been used to determine the age ranges of the strata.

Located at Long Reef in Sydney's northern suburbs, the Bulgo Sandstone of Olenekian age is a key fossiliferous unit of the Narrabeen Group, as is the Terrigal Formation near Gosford to the north of Sydney, from the Lower to Middle Triassic, Upper Olenekian-Lower Anisian. Exposures of these rocks occur along extensive sea-cliffs and the adjacent rock platforms. Fine-grained shales and sandstones that were deposited on a coastal floodplain by a stream that was flowing to the southeast comprise the Bulgo Sandstone and the Terrigal Formation.

Sources & Further reading

1. Kear, B.P. & Hamilton-Bruce, R.J., 2011, Dinosaurs in Australia, Mesozoic life from the southern continent, CSIRO Publishing.