page_title: Sutherland Shire
section_title: Geology
hierarchical_section_title: Sutherland Shire / Geography / Geology
caption_attribution_description: Sand Dunes in the Sutherland Shire, New South Wales, Australia. Two photo stitch
context_page_description: The Sutherland Shire is a local government area in the southern region of Sydney, in the state of New South Wales, Australia. The Sutherland Shire is colloquially known as "The Shire" and it has been featured in several reality television series.
  Geographically, it is the area to the south of Botany Bay and the Georges River. The administrative centre of the local government is located in the suburb of Sutherland, with council chambers located in Eton Street. Within the Shire is the birthplace of modern Australia, as it was the first landing site of Lieutenant James Cook, who went ashore onto what is now the suburb of Kurnell on 29 April 1770. It was originally intended to be the site of the first British Settlement, before Sydney Cove was chosen as the location during the First Fleet. The Sutherland Shire is 26 kilometres south of Sydney central business district, and is bordered by the City of Canterbury-Bankstown, City of Wollongong, City of Liverpool, Georges River Council and City of Campbelltown local government areas.
  The Sutherland Shire comprises an area of 370 square kilometres and as at the 2016 census had an estimated population of 218,464.
context_section_description: The geology of the Sutherland Shire, whilst sharing characteristics with the North Shore, is very different from the western and central suburbs of Sydney. The oldest rock unit in the Shire is the Illawarra Coal Measures, exposed from drilling at Helensburgh where it is 305 metres (1,001 ft) below sea level. Above the coal-bearing rocks is found the Narrabeen Group, mostly made up of layers of sandstone and characteristic red claystone beds. Overlying the Narrabeen Group is the Hawkesbury Sandstone, the rock unit most characteristic of the Shire. Occasional patches of Ashfield shale overlay the Hawkesbury sandstone. Some time later than the Triassic period - possibly early Tertiary - minor volcanic activity occurred in the region. This took the form of intrusion of a number of dykes of basaltic rock which forced their way up through the sedimentary rocks. Due to the wetting and drying action of the weather the basaltic rock of the dykes has changed to clay.
  From the end of the Triassic period to the middle of the Tertiary period, soft material was worn down or removed by wind and running water. In the final stages of this period of erosion the climate was apparently rather wetter and more humid than today's, causing the exposed rocks to change and form laterite soil, which is abundant in the Shire.
caption: Cronulla sand dunes, Kurnell Peninsula
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